PKIX M. Pritikin, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track P. Yee, Ed.
Expires: August 15, 2013 AKAYLA, Inc.
D. Harkins, Ed.
Aruba Networks
February 11, 2013
Enrollment over Secure Transport
draft-ietf-pkix-est-04
Abstract
This document profiles certificate enrollment for clients using
Certificate Management over CMS (CMC) messages over a secure
transport. This profile, called Enrollment over Secure Transport
(EST), describes a simple yet functional certificate management
protocol targeting Public Key Infrastructure (PKI) clients that need
to acquire client certificates and associated Certification Authority
(CA) certificate(s).
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 15, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Operational Scenario Overviews . . . . . . . . . . . . . . . . 6
2.1. Obtaining CA Certificates . . . . . . . . . . . . . . . . 7
2.2. Initial Enrollment . . . . . . . . . . . . . . . . . . . . 8
2.2.1. Certificate TLS authentication . . . . . . . . . . . . 8
2.2.2. Certificate-less TLS authentication . . . . . . . . . 8
2.2.3. HTTP-based client authentication . . . . . . . . . . . 8
2.3. Client Certificate Re-issuance . . . . . . . . . . . . . . 9
2.4. Server Key Generation . . . . . . . . . . . . . . . . . . 9
2.5. Full PKI Request messages . . . . . . . . . . . . . . . . 9
2.6. Certificate Signing Request (CSR) Attributes Request . . . 9
3. Protocol Design and Layering . . . . . . . . . . . . . . . . . 10
3.1. Application Layer . . . . . . . . . . . . . . . . . . . . 13
3.2. HTTP Layer . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.1. HTTP headers for control . . . . . . . . . . . . . . . 14
3.2.2. HTTP URIs for control . . . . . . . . . . . . . . . . 15
3.2.3. HTTP-Based Client Authentication . . . . . . . . . . . 16
3.2.4. Message types . . . . . . . . . . . . . . . . . . . . 17
3.3. TLS Layer . . . . . . . . . . . . . . . . . . . . . . . . 18
3.3.1. TLS-Based Server Authentication . . . . . . . . . . . 19
3.3.2. TLS-Based Client Authentication . . . . . . . . . . . 19
3.3.3. Certificate-less TLS Mutual Authentication . . . . . . 20
3.4. Proof-of-Possession . . . . . . . . . . . . . . . . . . . 20
3.5. Linking Identity and PoP information . . . . . . . . . . . 21
3.6. Server Authorization . . . . . . . . . . . . . . . . . . . 22
3.7. Client Authorization . . . . . . . . . . . . . . . . . . . 22
4. Protocol Exchange Details . . . . . . . . . . . . . . . . . . 23
4.1. Distribution of CA certificates . . . . . . . . . . . . . 23
4.1.1. Bootstrap Distribution of CA certificates . . . . . . 23
4.1.2. Distribution of CA certificates request . . . . . . . 24
4.1.3. Distribution of CA certificates response . . . . . . . 24
4.2. Client Certificate Request Functions . . . . . . . . . . . 25
4.2.1. Simple Enrollment of Clients . . . . . . . . . . . . . 26
4.2.2. Simple Re-Enrollment of Clients . . . . . . . . . . . 26
4.2.3. Simple Enroll and Re-Enroll Response . . . . . . . . . 27
4.3. Full CMC . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.3.1. Full CMC Request . . . . . . . . . . . . . . . . . . . 28
4.3.2. Full CMC Response . . . . . . . . . . . . . . . . . . 28
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4.4. Server-side Key Generation . . . . . . . . . . . . . . . . 29
4.4.1. Server-side Key Generation Request . . . . . . . . . . 29
4.4.2. Server-side Key Generation Response . . . . . . . . . 30
4.5. CSR Attributes . . . . . . . . . . . . . . . . . . . . . . 31
4.5.1. CSR Attributes Request . . . . . . . . . . . . . . . . 31
4.5.2. CSR Attributes Response . . . . . . . . . . . . . . . 31
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
6. Security Considerations . . . . . . . . . . . . . . . . . . . 34
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.1. Normative References . . . . . . . . . . . . . . . . . . . 36
7.2. Informative References . . . . . . . . . . . . . . . . . . 38
Appendix A. Operational Scenario Example Messages . . . . . . . . 39
A.1. Obtaining CA Certificates . . . . . . . . . . . . . . . . 39
A.2. Certificate TLS authentication . . . . . . . . . . . . . . 40
A.3. Username/Password Distributed Out-of-Band . . . . . . . . 42
A.4. Re-Enrollment . . . . . . . . . . . . . . . . . . . . . . 45
A.5. Server Key Generation . . . . . . . . . . . . . . . . . . 46
A.6. CSR Attributes . . . . . . . . . . . . . . . . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 50
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1. Introduction
This document profiles certificate enrollment for clients using
Certificate Management over CMS (CMC) [RFC5272] messages over a
secure transport. Enrollment over Secure Transport (EST) describes
the use of Transport Layer Security (TLS) 1.1 [RFC4346] (or a later
version) and Hypertext Transfer Protocol (HTTP) 1.1 [RFC2616] to
provide an authenticated and authorized channel for Simple PKI
Requests and Responses [RFC5272].
Architecturally, the EST service is located between a CA and a client
device. It performs several functions traditionally allocated to the
PKI role of the Registration Authority (RA). The nature of
communication between an EST server and a CA is not described in this
document.
EST adopts the Certificate Management Protocol (CMP) [RFC4210] model
for CA certificate rollover, but does not use the CMP message syntax
or protocol. EST servers are extensible in that new functions may be
defined to provide additional capabilities not specified in CMC
[RFC5272]. Non-CMC-based extensions, such as requesting Certificate
Signing Request attributes and requests for server-generated keys,
are defined in this document.
EST specifies how to transfer messages securely via HTTP over TLS
(HTTPS) [RFC2818], where the HTTP headers and content types are used
in conjunction with TLS. HTTPS operates over TCP; this document does
not specify EST over Datagram Transport Layer Security/User Datagram
Protocol (DTLS/UDP). Figure 1 shows how the layers build upon each
other.
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EST Layering:
Protocols:
+--------------------------------------------+
| |
| EST request/response messages |
| |
+--------------------------------------------+
| |
| HTTP for message transfer and signaling |
| |
+--------------------------------------------+
| |
| TLS for transport security |
| |
+--------------------------------------------+
| |
| TCP for transport |
| |
+--------------------------------------------+
Figure 1
[[EDNOTE: Comments such as this one, included within double brackets
and initiated with an 'EDNOTE', are for editorial use and shall be
removed as the document is polished.]]
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
It is assumed that the reader is familiar with the terms and concepts
described in Public Key Cryptography Standard (PKCS) #10 [RFC2314],
HTTPS [RFC2818], CMP [RFC4210], CMC [RFC5272][RFC5273][RFC5274], and
TLS [RFC4346].
In addition to the terms defined in the terminology section of CMC
[RFC5272] the following terms are defined for reading clarity:
EST CA: The CA the EST server is providing services for that
ultimately services requests accepted by the EST server. This
term is introduced for readability. The actual CA may be a member
of a complex PKI or it may be a simple embedded CA.
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Third-Party Trust Anchor (TA): Any Trust Anchor that is not
authoritative for the PKI hierarchy the EST server is providing
services for. For example TAs commonly used by web browsers to
authenticate web servers. The trust model for these TAs is
different from the trust model for Absolute Trust Anchors. (See
more details in Section 3.6 and Section 6.)
Absolute Trust Anchor: Any Trust Anchor that is authoritative for
the PKI hierarchy the EST server is providing services for or that
is specifically designated as providing trust for the EST server.
An EST client gives these TAs absolute precedence over Third-Party
TAs when selecting a TA to validate a certificate.
Certificate-less TLS: Use of a TLS cipher suite in which neither the
client nor server use a certificate to authenticate. The
credential used for authentication is a word, phrase, code or key
that is shared between the client and server. The credential must
be uniquely shared between the client and server in order to
provide authentication of an individual client.
2. Operational Scenario Overviews
This section provides an informative overview of the operational
scenarios to better introduce the reader to the protocol discussion.
This section does not include RFC 2119 key words.
Both the EST clients and server are configured with information that
provides the basis for bidirectional authentication and for
authorization. The specific initialization data depends on the
methods available in the client device and server, but can include
shared secrets, network service names and locations (e.g., a Uniform
Resource Identifier (URI) [RFC3986]), trust anchor information (e.g.,
a CA certificate or a hash of a TA's certificate), and enrollment
keys and certificates. Depending on an enterprise's acquisition and
network management practices, some initialization may be performed by
the vendor prior to delivery of client hardware and software. In
that case, the client device vendor may provide data, such as trust
anchors, to the enterprise via a secure procedure. The distribution
of this initial information is out of scope.
Distribution of trust anchors and other certificates can be effected
via the EST server. However, nothing can be inferred about the
authenticity of this data until an out-of-band mechanism is used to
verify them.
Sections 2.1-2.3 very closely mirror the text of the Scenarios
Appendix of [RFC6403] with such modifications as are appropriate for
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this profile. (Our thanks are extended to the authors of that
document). Sections 2.1-2.6, below, enumerate the set of EST
functions (see Figure 5) and provide an informative overview of EST's
capabilities.
The general client/server interaction proceeds as follows: The client
device initiates a TLS-secured HTTP session with an EST server. A
specific EST service is requested based on a portion of the URI used
for the session. The client device and server authenticate each
other. The client verifies that the server is authorized to serve
this client. The server verifies that the client is authorized to
make use of this server and the request that the client has made.
The server acts upon the client request.
2.1. Obtaining CA Certificates
The EST client can request a copy of the current CA certificates
under which the EST server's end-entity certificate has issued.
(Throughout this document we assume that a CA may have a certificate
used to verify signed objects issued by the CA, e.g., certificates
and certificate revocation lists (CRLs), and a separate end-entity
(EE) certificate used when communication with the CA requires
encryption.) The EST client is assumed to perform this operation
before performing other operations.
The EST client authenticates and verifies the authorization scope of
the EST server when requesting the current CA certificate(s). As
detailed in Section 3.3.1 and Section 3.3.3) available options
include:
o Verifying the EST server's HTTPS URI against the EST server's
certificate using third-party TAs (similar to a common HTTPS
exchange). This allows the EST server and client to leverage
existing TAs that might be known to the EST client.
o The client can leverage a previously distributed trust anchor
specific to the EST server. This allows the EST client to use an
existing, potentially older, CA certificate to request a current
CA certificate.
o For bootstrapping, the EST client can rely upon manual
authentication performed by the end user as detailed in
Section 4.1.1.
Client authentication is not required for this exchange, so it is
trivially supported by the EST server.
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2.2. Initial Enrollment
After authenticating an EST server and verifying that it is
authorized to provide services to the client, an EST client can
acquire a certificate (for itself) by submitting an enrollment
request to that server.
The EST server authenticates and authorizes the EST client as
specified in Section 3.3.2, Section 3.3.3 and Section 3.7. The
methods described in the normative text that are discussed in this
overview include:
o TLS with a previously issued client certificate (e.g., an existing
certificate issued by the EST CA);
o TLS with a previously installed certificate (e.g., manufacturer
installed certificate or a certificate issued by some other
party);
o Certificate-less TLS (e.g., with a shared credential distributed
out-of-band);
o HTTP-based with a username/password distributed out-of-band.
2.2.1. Certificate TLS authentication
If the EST client has a previously installed certificate issued by a
third party CA, this certificate can be used to authenticate the
client's request for a certificate from the EST server's CA (if that
CA is recognized by the EST server). An EST client responds to the
EST server's TLS certificate request message with the existing
certificate already held by the client. The EST server will verify
the client's existing certificate and authorize the client's request
as described in Section 3.3.2.
2.2.2. Certificate-less TLS authentication
The EST client can be authenticated using a certificate-less TLS
ciphersuite. An appropriate ciphersuite will also authenticate the
EST server to the EST client--i.e. it performs mutual authentication
(see Section 3.3.3).
2.2.3. HTTP-based client authentication
If the EST client cannot be authenticated during the TLS handshake
(see Section 3.3.2), or if the EST server requires additional
authentication information, the EST server can optionally also
request that the EST client submit a username/password using the HTTP
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Basic or Digest Authentication methods. See Section 3.2.3.
2.3. Client Certificate Re-issuance
An EST client can renew/rekey its existing client certificate by
submitting a re-enrollment request to an EST server.
When the current EST client certificate can be used for TLS client
authentication (Section 3.3.2) the client presents this certificate
to the EST server for client authentication. When the to be re-
issued EST client certificate cannot be used for TLS client
authentication any of the authentication methods used for initial
enrollment can be used.
For example if the client has an alternative certificate issued by
the EST CA that can be used for TLS client authentication then it can
be used.
The certification request message includes the same Subject and
SubjectAltName as the current certificate with name changes handled
as specified in Section 4.2.2.
2.4. Server Key Generation
The EST client can request a server-generated certificate and key
pair (see Section 4.4).
2.5. Full PKI Request messages
Full PKI Request [RFC5272] messages can be transported via EST using
the Full CMC Request function. This affords access to functions not
provided by the Simple Enrollment functions. Full PKI Request
messages are defined in Sections 3.2 and 4.2 of [RFC5272]. See
Section 4.3 for a discussion of how EST provides a transport for
these functions.
2.6. Certificate Signing Request (CSR) Attributes Request
Prior to sending an enrollment request to an EST server, an EST
client can query the EST server for a set of additional attribute(s)
that the client is requested to use in a subsequent enrollment
request.
These attributes can be requests for additional descriptive
information that the server does not have access to, e.g., the MAC
address of an interface, or they can be indicative of the kind of
enrollment request to make, e.g., a specific elliptic curve that the
client is expected to generate a public/private key pair with, or a
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specific hash function that the client is expected to use when
generating the CSR.
3. Protocol Design and Layering
Figure 2 provides an expansion of Figure 1 describing how the layers
are used. Each aspect is described in more detail in the sections
that follow.
EST Layering:
Protocols and uses:
+---------------------------------------------------+
| |
| Message types: |
| - "Simple PKI" messages |
| (incorporating proof-of-possession) |
| - CA certificate retrieval |
| - "Full PKI" messages (OPTIONAL) |
| - CSR attribute request (OPTIONAL) |
| - Server-generated key request (OPTIONAL) |
| |
+---------------------------------------------------+
| |
| HTTP: |
| - HTTP headers and URIs for control |
| - Content-Type headers specify message type |
| - Headers for control/error messages |
| - URIs for selecting functions |
| - Basic or Digest authentication (OPTIONAL) |
| |
+---------------------------------------------------+
| |
| TLS for transport security |
| - Authentication of the EST server |
| - Authentication of the EST client (OPTIONAL) |
| - Provides communications integrity |
| and confidentiality |
| - Channel Binding [RFC5929] to link |
| proof-of-identity with message-based |
| proof-of-possession. (OPTIONAL) |
| |
+---------------------------------------------------+
Figure 2
Specifying HTTPS as the secure transport for enrollment messages
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introduces two 'layers' to communicate authentication and control
messages: TLS and HTTP.
The TLS layer provides integrity and confidentiality during
transport. The proof-of-identity is supplied by TLS handshake
authentication and optionally also by the HTTP layer headers. The
message type and control/error messages are included in the HTTP
headers.
CMC [RFC5272] Section 3.1 notes that "the Simple PKI Request MUST NOT
be used if a proof-of-identity needs to be included". Since the TLS
and HTTP layers provide proof-of-identity for EST clients and servers
the Simple PKI message types are used.
The TLS layer certificate exchange provides a method for authorizing
client enrollment requests using existing certificates. Such
certificates may have been issued by the CA (from which the client is
requesting a certificate) or they may have been issued under a
distinct PKI (e.g., an IEEE 802.1AR IDevID [IDevID] credential).
Proof-of-possession is a distinct issue from proof-of-identity and is
included in the Simple PKI message type as described in Section 3.4.
A method of linking proof-of-identity and proof-of-possession is
described in Section 3.5.
This document also defines transport for CMC [RFC5272] that complies
with CMC Transport Protocols [RFC5273].
During protocol exchanges different certificates can be used. The
following table provides an informative overview. End-entities MAY
have one or more certificates of each type listed in Figure 3 and use
one or mor Trust Anchor databases of each type listed in Figure 4.
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Certificates and their corresponding uses:
+--------------+--------------------+-------------------------------+
| Certificate | Issuer | Use and section references |
+==============+====================+===============================+
| EST server | The CA served by | Presented by the EST server |
| certificate | the EST server | during the TLS handshake |
| | | |
| | | Section 3.3.1 |
+--------------+--------------------+-------------------------------+
| EST server | A CA | Presented by the EST server |
| certificate | authenticatable by | during the TLS handshake |
| | a third-party TA | |
| | | Section 3.3.1, and |
| | | Security Considerations |
+--------------+--------------------+-------------------------------+
| EST client | A CA | Presented by the EST client |
| certificate | authenticatable by | to the EST server by clients |
| | a third-party TA | that have not yet enrolled |
| | e.g., a device | |
| | manufacturer | Section 3.3.2 |
+--------------+--------------------+-------------------------------+
| EST client | The CA served by | Presented by the EST client |
| certificate | the EST server | to PKI End Entities. |
| | | Including to the EST server |
| | | during future EST operations |
| | | |
| | | Section 3.3.2 |
+--------------+--------------------+-------------------------------+
| EST client | The CA served by | Presented by the EST client |
| certificate | the EST server | to PKI End Entities. |
| | | Clients can obtain certs |
| | | that cannot be used for EST |
| | | client authentication |
| | | |
| | | Section 4.2.1 |
+--------------+--------------------+-------------------------------+
Figure 3
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Trust Anchor databases and their corresponding uses:
+--------------+----------------------------------------------------+
| TA database | Use and section references |
+==============+====================================================+
| EST server | EST servers use this TA database to authenticate |
| EST CA | certificates issued by the EST CA, including EST |
| TA database | client certificates during enroll/re-enroll |
| | operations |
| | |
| | Section 3.3.2 |
+--------------+----------------------------------------------------+
| EST server | EST servers use this TA database to authenticate |
| Third-Party | certificates issued by third-party TAs. |
| TA database | e.g., EST client certificates issued by a device |
| | manufacturer |
| | |
| | Section 3.3.2 |
+--------------+----------------------------------------------------+
| EST client | EST clients use this TA database to authenticate |
| Absolute | certificates issued by the EST CA, including EST |
| TA database | server certificates. |
| | |
| | Section 3.3.1 and |
| | Section 4.1 |
+--------------+----------------------------------------------------+
| EST client | EST clients use this trust anchor database to |
| Third-Party | authenticate an EST server that uses an externally |
| TA database | issued certificate. |
| | |
| | |
| | Section 3.1, Section 3.3.1 |
| | The client is RECOMMENDED to use an Absolute TA |
| | database instead of a Third-party TA database for |
| | the reasons detailed in the Security Considerations|
+--------------+----------------------------------------------------+
Figure 4
3.1. Application Layer
The EST client MUST be capable of generating and parsing Simple PKI
messages (see Section 4.2). Generating and parsing Full PKI messages
is OPTIONAL (see Section 4.3). The client MUST also be able to
request CA certificates from the EST server and parse the returned
"bag" of certificates (see Section 4.1). Requesting CSR attributes
and parsing the returned list of attributes is OPTIONAL (see
Section 4.5).
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Details of the EST client application configuration are out of scope
of the protocol discussion but are necessary for understanding the
prerequisites of initiating protocol operations. The EST client is
RECOMMENDED to be configured with an Absolute TA database for
Section 3.3.1 or with a secret key for Section 3.3.3. For human
usability reasons a "fingerprint" of the Absolute TA database entry
can be configured for bootstrapping as discussed in Section 4.1.1.
Configuration of a third-party TA database, perhaps by its inclusion
within the EST client distribution or available from the operating
system, provides flexibility along with the caveats detailed in
Section 6.
The EST client is configured with sufficient information to form the
EST server URI. This can be the full operation path segment (e.g.
https://www.example.com/.well-known/est/ or
https://www.example.com/.well-known/est/arbitraryLabel1) or the EST
client can be configured with a tuple composed of the authority
portion of the URI along with the OPTIONAL label (e.g.
"www.example.com:80", "arbitraryLabel1") or just the authority
portion of the URI.
3.2. HTTP Layer
HTTP is used to transfer EST messages. URIs are defined for handling
each media type (i.e., message type) as described in Section 3.2.2.
HTTP is also used for client authentication services when TLS client
authentication is not available, due to lack of a client certificate
suitable for use by TLS (see Section Section 3.2.3). HTTP
authentication can also be used in addition to TLS client
authentication if the EST server wishes additional authentication
information, as noted in Section 2.2.3. Registered media types are
used to convey EST messages as specified in Figure 6.
HTTP 1.1 [RFC2616] and above support persistent connections. As
described in Section 8.1 of that RFC, persistent connections may be
used to reduce network and processing load associated with multiple
HTTP requests. EST does not require or preclude persistent HTTP
connections and their use is out of scope of this specification.
3.2.1. HTTP headers for control
This document profiles the HTTP content-type header (as defined in
[RFC2046], but see Figure 6 for specific values) to indicate the
media type for EST messages and to specify control messages for EST.
The HTTP Status value is used to communicate success or failure of an
EST function. HTTP authentication is used by a client when requested
by the server.
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The media types indicated in the HTTP content-type header indicates
which EST message is being transferred. Media types used by EST are
specified in Section 3.2.4.
3.2.2. HTTP URIs for control
The EST server MUST use the [RFC5785] defined path-prefix of "/.well-
known/" and the registered name of "est". Thus a valid EST server
URI path begins with "https://www.example.com/.well-known/est". Each
EST operation is indicated by a path-suffix that indicates the
intended operation:
Operations and their corresponding URIs:
+------------------------+-----------------+-------------------+
| Operation |Operation Path | Details |
+========================+=================+===================+
| Distribution of CA | /CACerts | Section 4.1 |
| certificates (MUST) | | |
+------------------------+-----------------+-------------------+
| Enrollment of new | /simpleEnroll | Section 4.2. |
| clients (MUST) | | |
+------------------------+-----------------+-------------------+
| Re-Enrollment of | /simpleReEnroll | Section 4.2.2 |
| existing clients (MUST)| | |
+------------------------+-----------------+-------------------+
| Full CMC (OPTIONAL) | /fullCMC | Section 4.3 |
+------------------------+-----------------+-------------------+
| Server-side Key | /serverKeyGen | Section 4.4 |
| Generation (OPTIONAL) | | |
+------------------------+-----------------+-------------------+
| Request CSR attributes | /CSRAttrs | Section 4.5 |
| (OPTIONAL) | | |
+------------------------+-----------------+-------------------+
Figure 5
The operation path (Figure 5) is appended to the path-prefix to form
the URI used with HTTP GET or POST to perform the desired EST
operation. An example valid URI absolute path for the "/CACerts"
operation is "/.well-known/est/CACerts". To retrieve the CA's
certificates, the EST client would use the following HTTP request:
GET /.well-known/est/CACerts HTTP/1.1
Likewise, to request a new certificate in this example scheme, the
EST client would use the following request:
POST /.well-known/est/simpleEnroll HTTP/1.1
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The use of distinct operation paths simplifies implementation for
servers that do not perform client authentication when distributing
/CACerts responses.
An EST server MAY provide service for multiple CAs as indicated by an
OPTIONAL additional path segment between the registered application
name and the operation path. To avoid conflict the CA label MUST NOT
be the same as any defined operation path segment. The EST server
MUST provide services when the additional path segment is not
included. The following are three example valid URIs:
1. https://www.example.com/.well-known/est/CACerts
2. https://www.example.com/.well-known/est/arbitraryLabel1/CACerts
3. https://www.example.com/.well-known/est/arbitraryLabel2/CACerts
In this specification the distinction between enroll and renew/rekey
is explicitly indicated by the HTTP URI. When requesting /fullCMC
operations CMC uses the same messages for certificate renewal and
certificate rekey.
An EST server MAY provide additional services using other URIs.
3.2.3. HTTP-Based Client Authentication
The EST server MAY request HTTP-based client authentication. This
request can be in addition to successful TLS client authentication
(Section 3.3.2) if EST server policy requires additional
authentication. (For example the EST server may require that an EST
client "knows" a password in addition to "having" an existing client
certificate). Or HTTP-based client authentication can be an EST
server policy specified fallback in situations where the EST client
did not successfully complete the TLS client authentication. (This
might arise if the EST client is enrolling for the first time or if
the certificates available to an EST client cannot be used for TLS
client authentication).
HTTP Basic and Digest authentication MUST only be performed over TLS
1.1 [RFC4346] or later versions. As specified in CMC: Transport
Protocols [RFC5273] the server "MUST NOT assume client support for
any type of HTTP authentication such as cookies, Basic
authentication, or Digest authentication". Clients SHOULD support
the Basic and Digest authentication mechanism.
Servers that wish to use Basic and Digest authentication reject the
HTTP request using the HTTP defined WWW-Authenticate response-header
([RFC2616], Section 14.47). The client is expected to retry the
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request, including the appropriate Authorization Request Header
([RFC2617], Section 3.2.2), if the client is capable of using the
Basic or Digest authentication. If the client is not capable then
the client MUST terminate the connection.
A client MAY set the username to the empty string ("") if it is
presenting a password that is not associated with a username.
Support for HTTP-based client authentication has security
ramifications as discussed in Section 6. The client MUST NOT respond
to the server's HTTP authentication request unless the client has
authenticated the EST server (as per Section 3.6).
3.2.4. Message types
This document uses existing media types for the messages as specified
by [RFC2585], [RFC5967], and CMC [RFC5272]. To support distribution
of multiple certificates for a CA certificate path, the [RFC2046]
multipart/mixed media type is used.
Each distinct EST message type is specified using a HTTP Content-Type
header with a specific media type. The use herein is consistent with
[RFC5273].
The EST messages and their corresponding media types are:
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+--------------------+--------------------------+-------------------+
| Message type |Request media type | Request section(s)|
| |Response media type(s) | Response section |
| |Source(s) of types | |
+====================+==========================+===================+
| CA certificate | N/A | Section 4.1 |
| request | application/pkcs7-mime | Section 4.1.1 |
| | [RFC5751] | |
+--------------------+--------------------------+-------------------+
| Cert enroll/renew/ | application/pkcs10 | Section 4.2/4.2.1 |
| rekey | application/pkcs7-mime | Section 4.2.2 |
| | [RFC5967] [RFC5751] | |
+--------------------+--------------------------+-------------------+
| Full CMC | application/pkcs7-mime | Section 4.3.1 |
| | application/pkcs7-mime | Section 4.3.2 |
| | [RFC5751] | |
+--------------------+--------------------------+-------------------+
| Server-side Key | application/pkcs10 | Section 4.4.1 |
| Generation | multipart/mixed | Section 4.4.2 |
| | (application/pkcs7-mime &| |
| | application/pkcs8) | |
| | [RFC5967] [RFC5751] & | |
| | [RFC5958] | |
+--------------------+--------------------------+-------------------+
| Request CSR | N/A | Section 4.5.1 |
| attributes | application/csrattrs | Section 4.5.2 |
| | This RFC | |
+--------------------+--------------------------+-------------------+
Figure 6
3.3. TLS Layer
TLS provides communications security for the layers above it. The
integrity and confidentiality services it provides are leveraged to
supply proof-of-identity and to allow authorization decisions to be
made. The EST server and EST client are responsible for ensuring
that an acceptable cipher suite is negotiated and that bidirectional
authentication has been performed. Alternately, certificate-less TLS
authentication, where neither the client nor server present a
certificate, is also an acceptable method for EST authentication.
HTTPS [RFC2818] and specifies how HTTP messages are carried over TLS.
HTTPS MUST be used. TLS 1.1 [RFC4346] (or later) MUST be supported.
TLS session resumption [RFC5077] SHOULD be supported.
TLS channel binding information MAY be inserted into a certificate
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request as detailed in Section 3.5 in order to provide the EST server
with assurance that the authenticated TLS client has access to the
private key for the certificate being requested.
3.3.1. TLS-Based Server Authentication
The EST server MUST be authenticated during the TLS handshake unless
the client is requesting Bootstrap Distribution of CA certificates
(Section 4.1.1) or Full CMC (Section 4.3).
The EST client authenticates the EST server as defined for the cipher
suite negotiated. The following text provides details assuming a
certificate-based cipher suite, such as the TLS 1.1 [RFC4346]
mandatory cipher suite (TLS_RSA_WITH_3DES_EDE_CBC_SHA). As an
alternative to authentication using a certificate, an EST client MAY
support certificate-less TLS authentication (Section 3.3.3).
Certificate validation MUST be performed as per [RFC5280]. The EST
server certificate MUST conform to the [RFC5280] certificate profile.
The client validates the TLS server certificate using the EST client
TA databases. If certificate validation fails, the client MAY follow
the procedure outlined in Section 4.1.1 for bootstrap distribution of
CA certificates.
The EST client MUST perform authorization checks as specified in
Section 3.6.
3.3.2. TLS-Based Client Authentication
TLS client authentication is the RECOMMENDED method for identifying
EST clients. HTTP-Based Client Authentication (Section 3.2.3) MAY be
used.
The EST server authenticates the EST client as defined for the cipher
suite negotiated. The following text provides details assuming a
certificate-based cipher suite such as the TLS 1.1 [RFC4346]
mandatory cipher suite (TLS_RSA_WITH_3DES_EDE_CBC_SHA). The EST
server MUST support certificate based client authentication. As an
alternative or as an addition to authentication using a certificate,
an EST server MAY support certificate-less TLS authentication
(Section 3.3.3).
When requesting renew/rekey operations the client MUST use the
existing client certificate that was issued by the EST server unless
this certificate is not appropriate for the negotiated cipher suite.
In that case, the client SHOULD use an alternate certificate, with
the same subject identity information, that is appropriate for the
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negotiated cipher suite. When requesting an enroll operation the
client MAY use a third-party issued client certificate. The EST
server MUST perform authorization checks as specified in Section 3.7.
If a client does not support TLS client authentication, then it MUST
support HTTP-based client authentication (Section 3.2.3) or
certificate-less TLS authentication (Section 3.3.3).
3.3.3. Certificate-less TLS Mutual Authentication
Certificate-less TLS ciphersuites provide a way to perform mutual
authentication in situations where neither the client nor server have
certificates, or do not have a way to verify a certificate. The
client and server MAY negotiate a certificate-less cipher suite for
mutual authentication. Existing documents such as [TLS-SRP] and
[TLS-SRP] present techniques for a certificate-less TLS connection.
When using certificate-less mutual authentication in TLS for
enrollment, the cipher suite MUST be resistant to dictionary attack.
This means that the advantage an adversary gains through attack MUST
be related to interaction and not computation. TLS cipher suites
used with EST to perform certificate-less TLS mutual authentication
MUST be based on a zero knowledge protocol to enable proof of
knowledge of the shared secret without exposure of the shared secret
(or any derived data which can be used to determine the secret).
These requirements mean that the adversary gains advantage solely
through active attack, and the only thing learned from each active
attack is whether a single guess of the secret is successful or not.
Implementations of EST that support certificate-less TLS cipher
suites SHOULD provide countermeasures, e.g., exponential back off
after failed attempts or locking of an account after a certain number
of unsuccessful attempts, to mitigate repeated, active attacks.
A certificate-less ciphersuite MUST provide sufficient information to
perform the authorization checks. For example if the cipher suite
uses a pre-shared secret, provisioned in an out-of-band fashion, as a
credential to perform mutual authentication then knowledge of the
pre-shared secret implies authorization as a peer in the exchange.
3.4. Proof-of-Possession
As defined in Section 2.1 of CMC [RFC5272], Proof-of-possession (POP)
"refers to a value that can be used to prove that the private key
corresponding to the public key is in the possession and can be used
by an end-entity."
The signed enrollment request provides a signature-based proof-of-
possession. The mechanism described in Section 3.5 strengthens this
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by optionally including "Direct"-based proof-of-possession [RFC5272]
by including TLS session-specific information within the data covered
by the enrollment request signature (thus linking the enrollment
request to the authenticated end-point of the TLS connection).
3.5. Linking Identity and PoP information
Server policy determines whether the server requires that the TLS
client identity and proof-of-posession of the private key associated
with a certification are linked. This specification provides an
OPTIONAL method of linking identity and proof-of-possession by
including information specific to the current authenticated TLS
session within the signed certification request. Clients are
RECOMMENDED to link identity and PoP. If the client does not have
local policy configuration the client MAY determine that this method
is expected by examining the CSR Attributes Response (see
Section 4.5.2). The EST server MUST verify the tls-unique
information embedded within the certification request if it is
included in the request. The EST server MAY reject requests without
tls-unique information as indicated by server policy.
Linking identity and proof-of-possession proves to the server that
the authenticated TLS client has possession of the private key
associated with the certification request and that the client was
able to sign the certification request after the TLS session was
established. This is an alternative to the [RFC5272] Section 6.3-
defined "Linking Identity and POP information" method available if
Full PKI messages are used.
The client generating the request obtains the tls-unique value as
defined in Channel Bindings for TLS [RFC5929] from the TLS subsystem.
The tls-unique specification includes a synchronization problem as
described in Channel Bindings for TLS [RFC5929] section 3.1. To
avoid this problem, EST implementations that support this feature
MUST use the tls-unique value from the first TLS handshake. EST
clients and servers use their tls-unique implementation specific
synchronization methods to obtain this first tls-unique value. TLS
"secure_renegotiation" [RFC5746] MUST be used. This maintains the
binding from the first tls-unique value across renegotiations to the
most recently negotiated connection.
The tls-unique value is Base 64 encoded as specified in Section 4 of
[RFC4648] and the resulting string is placed in the certification
request challenge-password field ([RFC2985], Section 5.4.1). If tls-
unique information is not embedded within the certification request
the challenge-password field MUST be empty to indicate that the
client did not include the optional channel-binding information (any
value submitted is verified by the server as tls-unique information).
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If the EST server forwards the request to back-end infrastructure for
processing, it is RECOMMENDED that the results of this verification
be communicated. (For example this communication might use the CMC
"RA POP Witness Control" in a CMC Full PKI Request message. Or an
EST server might TLS authenticate an EST client as being a trusted
infrastructure element that does not forward invalid requests. A
detailed discussion of back-end processing is out of scope).
When rejecting requests, the EST server response is as described for
all enroll responses (Section 4.2.3). If a Full PKI Response is
included, the CMCFailInfo MUST be set to popFailed. If a human
readable reject message is included it SHOULD include an informative
text message indicating that linking of identity and POP information
is required.
3.6. Server Authorization
The client MUST check EST server authorization before accepting any
server responses or responding to HTTP authentication requests.
When the EST client Third-Party TA database is used to validate the
EST server certificate the client MUST check the URI "against the
server's identity as presented in the server's Certificate message"
(HTTP Over TLS Section 3.1 "Server Identity" [RFC2818] and
[RFC6125]). The provisioned URI provides the basis for
authorization, and the server's authenticated identity confirms it is
the authorized server.
When the EST client Absolute TA database is used to validate the EST
server certificate the client MUST check either the URI against the
server's identity or the EST server certificate MUST contain the id-
kp-cmcRA [RFC6402] extended key usage extension. The client MUST
maintain a distinction between the Absolute TA database and any
Third-Party TAs database in order to make this determination.
Successful authentication using a certificate-less cipher suite
implies authorization of the server.
The client MAY perform bootstrapping as specified in Section 4.1.1
even if these checks fail.
3.7. Client Authorization
The decision to issue a certificate to a client is always controlled
by local CA policy. The EST server configuration reflects this CA
policy. This document does not specify any constraints on such
policy. EST provides the EST server access to each client's
authenticated identity -- e.g., the TLS client's certificate in
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addition to any HTTP user authentication credentials -- to help in
implementing such policy.
If the client's certificate was issued by the EST CA, and it includes
the id-kp-cmcRA [RFC6402] extended key usage extension, then the
client is a Registration Authority (RA) as described in [RFC5272] and
[RFC6402]. In this case the EST server SHOULD apply authorization
policy consistent with an RA client. For example when handling
/simpleEnroll requests the EST server could be configured to accept
PoP linking information that does not match the current TLS session
because the authenticated EST client RA has verified this information
when acting as an EST server (as specified in Section 3.5). More
specific RA mechanisms are available if the EST client uses /fullCMC
methods.
4. Protocol Exchange Details
Before processing a request, an EST server determines if the client
is authorized to receive the requested services. Likewise, the
client determines if it will make requests to the EST server. These
authorization decisions are described in the next two sections.
Assuming that both sides of the exchange are authorized, then the
actual operations are as described in subsequent sections.
4.1. Distribution of CA certificates
The EST client can request a copy of the current CA certificates.
This function is generally performed before other EST functions.
4.1.1. Bootstrap Distribution of CA certificates
When the EST server uses an EST CA issued certificate for TLS server
authentication it is possible that the client was not configured with
the Absolute TA database necessary to validate the server
certificate. This section describes methods by which minimally
configured EST clients can populate their Absolute TA database.
If the EST client application does not specify either an Absolute TA
database or a Third-party TA database then the initial TLS server
authentication and authorization will fail. The client MAY
provisionally continue the TLS handshake to completion for the
purposes of accessing the /CACerts or /fullCMC method. If the EST
client continues with an unauthenticated connection, the client MUST
extract the HTTP content data from the response (Section 4.1.3 or
Section 4.3.2) and engage a human user to authorize the CA
certificate using out-of-band data such as a CA certificate
"fingerprint" (e.g., a SHA-1, SHA-256, SHA-512 [SHS], or MD5
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[RFC1321] hash on the whole CA certificate). In a /fullCMC response
it is the Publish Trust Anchors control within the Full PKI Response
that must be accepted manually. It is incumbent on the user to
properly verify the TA information, or to provide the "fingerprint"
data during configuration that is necessary to verify the TA
information.
HTTP authentication requests MUST NOT be responded to if the server
has not been authenticated. The EST client uses the /CACerts
response to establish a trust anchor for subsequent TLS
authentication of the EST server. EST clients MUST NOT engage in any
other protocol exchange until after the /CACerts response has been
accepted and a new TLS session has been established (using TLS
certificate-based authentication).
4.1.2. Distribution of CA certificates request
EST clients request the Absolute TA database information of the CA
(in the form of certificates) with an HTTPS GET message using an
operation path of "/CACerts". EST clients and servers MUST support
the /CACerts function. Clients SHOULD request an up-to-date response
before stored information has expired in order to ensure the EST CA
TA database is up to date.
The EST server MUST NOT require client authentication or
authorization to reply to this request.
The client MUST authenticate the EST server as specified in
Section 3.3.1 and Section 3.3.3 and check the server's authorization
as given in Section 3.6 or follow the procedure outlined in
Section 4.1.1.
4.1.3. Distribution of CA certificates response
The EST server responds to a Distribution of CA certificates request
with the EST CA certificates within a Simple PKI Response. If the
certificates are successfully returned, the server response MUST have
an HTTP 200 response code with a content-type of "application/
pkcs7-mime". Any other response code indicates an error and the
client MUST abort the protocol.
The EST server MUST include the current root CA certificate in the
response. The EST server MUST include any additional certificates
the client would need to build a chain from an EST CA issued
certificate to the current Absolute TA. For example if the EST CA is
a subordinate CA then all the appropriate subordinate CA certificates
necessary to build a chain to the root EST CA are included in the
response.
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The EST server SHOULD include the three "Root CA Key Update"
certificates OldWithOld, OldWithNew, and NewWithOld in the response
chain. These are defined in Section 4.4 of CMP [RFC4210]. The EST
client MUST be able to handle these certificates in the response.
The CA's most recent self-signed certificate (e.g. NewWithNew
certificate) is self-signed and has the latest NotAfter date. This
the Absolute TA in the form of a self-signed certificate. If the EST
server does not include these in the response then after the current
Absolute TA certificate expires the EST clients will need to be
(re)enrolled with the PKI using the Bootstrap Distribution of CA
certificates (Section 4.1.1) method.
The Absolute TA certificate is the certificate that is either
application supplied or is extracted and authorized using out-of-band
information as described in Section 4.1.1. After out-of-band
validation occurs, all the other certificates MUST be validated using
normal [RFC5280] certificate path validation (using the most recent
CA certificate as the TA) before they can be used to build
certificate paths during certificate validation.
The response format is the CMC Simple PKI Response, as defined in
[RFC5272]. The HTTP content-type of "application/pkcs7-mime" is
used. The Simple PKI response is Base64 encoded, as specified in
Section 4 of [RFC4648], and sandwiched between headers:
-----BEGIN PKCS7-----
MIIBhDCB7gIBADBFMQswCQYDVQQGEwJBVTETMBEGA1UECBMKU29tZS1TdGF0ZTEh
Simplified example of Base64 encoding of CMC Simple PKI Response
ED8rf3UDF6HjloiV3jBnpetx4JjZH/BlmD9HMqofVEryb1e4iZgMUvuIgwEjQwpD
8J4OhHvLh1o=
-----END PKCS7-----
4.2. Client Certificate Request Functions
EST clients request a certificate from the EST server with an HTTPS
POST using the operation path value of "/simpleEnroll". EST clients
request a renew/rekey of existing certificates with an HTTP POST
using the operation path value of "/simpleReEnroll". EST servers
MUST support the /simpleEnroll and /simpleReEnroll functions.
It is RECOMMENDED that a client obtain the current CA certificates,
as described in Section 4.1, before performing certificate request
functions. This ensures that the client will be able to validate the
EST server certificate. The client MUST authenticate the EST server
as specified in Section 3.3.1 and Section 3.3.3. The client MUST
verify the authorization the EST server as specified in Section 3.6.
The server MUST authenticate the client as specified in Section 3.3.2
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and Section 3.3.3. The server MUST verify client authorization as
specified in Section 3.7. The EST server MUST check the tls-unique
value as described in Section 3.5 if one is submitted by the client.
The server MAY accept a certificate request for manual authorization
checking by an administrator. (Section 4.2.3 describes the use of an
HTTP 202 response to the EST client if this occurs).
4.2.1. Simple Enrollment of Clients
When HTTPS POSTing to /simpleEnroll the client MUST include a Simple
PKI Request as specified in CMC Section 3.1 (i.e., a PKCS#10
Certification Request).
The Certification Signing Request (CSR) signature provides proof-of-
possession of the private key to the EST server. If the CSR KeyUsage
extension indicates the private key can be used to generate digital
signatures then the CSR signature MUST be generated using the private
key. If the key can be used to generate digital signatures but the
requested CSR KeyUsage extension prohibits generation of digital
signatures then the CSR signature MUST still be generated using the
private key but the key MUST NOT be used to for any other signature
operations (this is consistent with the recommendations concerning
submission of proof-of-possession to an RA or CA as described in
[SP-800-57-Part-1]). The use of /fullCMC operations provides access
to more advanced proof-of-possession methods that MUST be used when
the key pair can not be used for digital signature generation (see
Section 4.3).
The HTTP content-type of "application/pkcs10" is used here. The
format of the message is as specified in Section 6.4 of [RFC4945].
The EST client MAY request additional certificates even when using an
existing certificate in the TLS client authentication. For example
the client can use an existing certificate for TLS client
authentication when requesting a certificate that cannot be used for
TLS client authentication.
4.2.2. Simple Re-Enrollment of Clients
EST clients renew/rekey certificates with an HTTPS POST using the
operation path value of "/simpleReEnroll".
A certificate request employs the same format as the "simpleEnroll"
request, using the same HTTP content-type. The request Subject field
and SubjectAltName extension MUST be identical to the corresponding
fields in the certificate being renewed/rekeyed. The
ChangeSubjectName attribute, as defined in [RFC6402], MAY be included
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in the CSR to request that these fields be changed in the new
certificate.
If the Subject Public Key Info in the certification request is the
same as the current client certificate, the EST server performs a
renew operation. If the public key information is different than the
currently issued certificate then the EST server performs a rekey
operation.
4.2.3. Simple Enroll and Re-Enroll Response
If the enrollment is successful, the server response MUST contain an
HTTP 200 response code with a content-type of "application/
pkcs7-mime". The response data is a certs-only Simple PKI Response
containing only the certificate that was issued. The Simple PKI
response is Base64 encoded and sandwiched between headers:
-----BEGIN PKCS7-----
MIIBhDCB7gIBADBFMQswCQYDVQQGEwJBVTETMBEGA1UECBMKU29tZS1TdGF0ZTEh
Simplified example of Base64 encoding of CMC Simple PKI Response
ED8rf3UDF6HjloiV3jBnpetx4JjZH/BlmD9HMqofVEryb1e4iZgMUvuIgwEjQwpD
8J4OhHvLh1o=
-----END PKCS7-----
When rejecting a request the server MUST specify either an HTTP 4xx
error, or an HTTP 5xx error. A Simple PKI Response with an HTTP
content-type of "application/pkcs7-mime" (see Section 4.3.2) MAY be
included in the response data to convey an error response. If the
content-type is not set the response data MUST be a plain text human-
readable error message containing informative information describing
why the request was rejected (for example indicating that CSR
attributes are incomplete).
If the server responds with an HTTP [RFC2616] 202, this indicates
that the request has been accepted for processing but that a response
is not yet available. The server MUST include a Retry-After header
as defined for HTTP 503 responses. The server also MAY include
informative human-readable content. The client MUST wait at least
the specified 'retry-after' time before repeating the same request.
The client repeats the initial enrollment request after the
appropriate 'retry-after' interval has expired. The client SHOULD
log or inform the end user of this event. The server is responsible
for maintaining all state necessary to recognize and handle retry
operations as the client is stateless in this regard; it simply sends
the same request repeatedly until it receives a different response
code.
All other return codes are handled as specified in HTTP [RFC2616].
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4.3. Full CMC
An EST client can request a certificate from an EST server with an
HTTPS POST using the operation path value of "/fullCMC". Support for
the /fullCMC function is OPTIONAL for both clients and servers.
4.3.1. Full CMC Request
If the HTTP POST to /fullCMC is not a valid Full PKI Request, the
server MUST reject the message. The HTTP content-type used is
"application/pkcs7-mime", as specified in [RFC5273].
4.3.2. Full CMC Response
The server responds with the client's newly issued certificate or
provides an error response.
If the enrollment is successful, the server response MUST include an
HTTP 200 response code with a content-type of "application/
pkcs7-mime" as specified in [RFC5273]. The response data includes
either the Simple PKI Response or the Full PKI Response as specified
in Section 3.2 of [RFC5272].
When rejecting a request, the server MUST specify either an HTTP 4xx
error or an HTTP 5xx error. A CMC response with content-type of
"application/pkcs7-mime" SHOULD be included in the response data for
any CMC error response. If the content-type is not set the response
data MUST be a plain text human-readable error message containing
informative information describing why the request was rejected (for
example indicating that CSR attributes are incomplete).
All other return codes are handled as specified in Section 4.2.3 or
HTTP [RFC2616]. For example, a client interprets a HTTP 404 or 501
response to indicate that this service is not implemented.
The Full PKI Response is Base64 encoded and sandwiched between
headers:
-----BEGIN PKCS7-----
MIIBhDCB7gIBADBFMQswCQYDVQQGEwJBVTETMBEGA1UECBMKU29tZS1TdGF0ZTEh
Simplified example of Base64 encoding of CMC Full PKI Response
ED8rf3UDF6HjloiV3jBnpetx4JjZH/BlmD9HMqofVEryb1e4iZgMUvuIgwEjQwpD
8J4OhHvLh1o=
-----END PKCS7-----
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4.4. Server-side Key Generation
An EST client may request a private key and associated certificate
from an EST server using an HTTPS POST with an operation path value
of "/serverKeyGen". Support for the /serverKeyGen function is
OPTIONAL.
A client MUST authenticate an EST server as specified in
Section 3.3.1 and Section 3.3.3.
The EST server MUST authenticate the client as specified in
Section 3.3.2 and Section 3.3.3. The server SHOULD use Client
Authorization for authorization purposes. The EST server applies
whatever authorization or logic it chooses to determine if the
private key and certificate should be provided.
Proper random number and key generation [RFC4086] is a server
implementation responsibility and server storage of generated keys is
a local option. The key pair and certificate are transferred over
the TLS session. The cipher suite used to return the private key and
certificate MUST offer confidentiality commensurate with the private
key being delivered to the client.
The EST client MAY request additional certificates even when using an
existing certificate in the TLS client authentication. For example
the client can use an existing certificate for TLS client
authentication when requesting a certificate that cannot be used for
TLS client authentication.
4.4.1. Server-side Key Generation Request
The certificate request is HTTPS POSTed and is the same format as for
the "/simpleEnroll" and "/simpeReEnroll" path extensions with the
same content-type.
In all respects the server SHOULD treat the CSR as it would any
enroll or re-enroll CSR; the only distinction here is that the server
MUST ignore the public key values and signature in the CSR. These
are included in the request only to allow re-use of existing
codebases for generating and parsing such requests.
If the client desires to receive the private key with encryption that
exists outside and in addition to that of the TLS transport used by
EST or if server policy requires that the key be delivered in such a
form, the client MUST include a DecryptKeyIdentifier attribute (as
defined in Section 2.2.5, [RFC4108]) specifying the identifier of the
secret key to be used by the server to encrypt the private key.
While that attribute was originally designated for specifying a
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firmware encryption key, it exactly mirrors the requirements for
specifying a private key encryption key. If the server does not have
a secret key matching the identifier specified by the client, the
request must be terminated and an error returned to the client.
Distribution of the key specified by the DecryptKeyIdentifer to the
key generator and the client is outside the scope of this document.
4.4.2. Server-side Key Generation Response
If the request is successful, the server response MUST have an HTTP
200 response code with a content-type of "multipart/mixed" consisting
of two parts. One part is the private key data and the other part is
the certificate data.
The format in which the private key data part is returned is
dependent on whether the private key is being returned with
additional encryption on top of that provided by TLS.
o If additional encryption is being employed, the private key data
part MUST be an "application/pkcs7-mime". The content of this
message is an Asymmetric Key Package (see Section 2 [RFC5958])
protected inside of a CMS [RFC5652] SignedData content which is
further protected inside of a CMS EnvelopedData, as described in
Section 4 of [RFC5958]. The Signed Data is signed by the party
that generated the private key, which may or may not be the EST
server. The EnvelopedData content is encrypted using the secret
key identified in the request.
o If additional encryption is not being employed, the private key
data MUST be an "application/pkcs8". An "application/pkcs8" part
consists of the Base64 encoded DER-encoded PrivateKeyInfo
sandwiched between headers as described in [RFC5958].
The certificate data part is an "application/pkcs7-mime" and exactly
matches the certificate response to /simpleEnroll. If both parts are
"application/pkcs7-mime" the client checks each; one will be a certs-
only Simple PKI response and the other will be the CMS message with
the encrypted data.
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-----BEGIN PRIVATE KEY-----
MIIBhDCB7gIBADBFMQswCQYDVQQGEwJBVTETMBEGA1UECBMKU29tZS1TdGF0ZTEh
Simplified example of Base64 encoding of DER-encoded PrivateKeyInfo
ED8rf3UDF6HjloiV3jBnpetx4JjZH/BlmD9HMqofVEryb1e4iZgMUvuIgwEjQwpD
8J4OhHvLh1o=
-----END PRIVATE KEY-----
or
-----BEGIN PKCS7-----
MIIBhDCB7gIBADBFMQswCQYDVQQGEwJBVTETMBEGA1UECBMKU29tZS1TdGF0ZTEh
Simplified example of Base64 encoding of CMS secured Private key
ED8rf3UDF6HjloiV3jBnpetx4JjZH/BlmD9HMqofVEryb1e4iZgMUvuIgwEjQwpD
8J4OhHvLh1o=
-----END PKCS7-----
When rejecting a request, the server MUST specify either an HTTP 4xx
error, or an HTTP 5xx error. If the content-type is not set, the
response data MUST be a plain text human-readable error message.
4.5. CSR Attributes
CA policy may allow inclusion of client-provided attributes in
certificates that it issues, and some of these attributes may
describe information that is not available to the CA. In addition, a
CA may desire to certify a certain type of public key and a client
may not have a priori knowledge of that fact. Therefore, clients
SHOULD request a list of expected attributes that are required, or
desired, by the CA in an enrollment request, or if dictated by local
policy.
Requesting CSR Attributes is optional but clients are advised that
CA's may refuse enrollment requests that are not encoded according to
the CA's policy.
4.5.1. CSR Attributes Request
The EST client requests a list of CA-desired CSR attributes from the
CA by sending an HTTPS GET message to the EST server with an
operations path of "/CSRAttrs".
4.5.2. CSR Attributes Response
If locally configured policy for an authenticated EST client
indicates a CSR Attributes Response is to be provided, the server
response MUST include an HTTP 200 response code. An HTTP response
code of 204 or 404 indicates that a CSR Attributes Response is not
available. Regardless of the response code, the EST server and CA
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MAY reject any subsequent enrollment requests for any reason, e.g.,
incomplete CSR attributes in the request.
If the CA requires a particular crypto system (e.g., certification of
a public key based on a certain elliptic curve) it MUST provide that
information in the CSR Attributes response. If an EST server
requires the linking of identity and PoP information (see
Section 3.5) it MUST include the challengePassword OID in the CSR
Attributes response.
Responses to attribute request messages MUST be encoded as content
type "application/csrattrs". The syntax for application/csrattrs
body is as follows:
Csrattrs ::= SEQUENCE SIZE (0..MAX) OF OBJECT IDENTIFIER { }
An EST server includes zero or more object identifiers that it
requests the client to include in a certification request. When the
server encodes Csrattrs as an empty SEQUENCE it means that the server
has no specific additional attributes it requests in a client
certification request (this is functionally equivalent to an HTTP
response code of 204 or 404.) The sequence is Distinguished Encoding
Rules (DER) encoded and then base64 encoded (section 4 of [RFC4648]).
The resulting text forms the application/csrattr body, without
headers.
For example, if a CA requests a client to submit a certification
request containing the Media Access Control (MAC) address [RFC2397]
of a device, the challengePassword (indicating that Linking of
Identity and POP information is requested, see Section 3.5), to use
the the secp384r1 elliptic curve, and to use the SH384 hash function
then it sends the following object identifiers:
o macAddress: 1.3.6.1.1.1.1.22
o challengePassword: 1.2.840.113549.1.9.7
o the secp384r1 elliptic curve: 1.3.132.0.4
o the SHA384 hash function: 2.16.840.1.101.3.4.2.2
and encodes them into an ASN.1 SEQUENCE to produce:
30 26 06 07 2B 06 01 01 01 01 16 06 09 2A 86 48 86 F7 0D 01 09 07
06 05 2B 81 04 00 04 06 09 60 86 48 01 65 03 04 02 02
and then base64 encodes the resulting ASN.1 SEQUENCE to produce:
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MCYGBysGAQEBARYGCSqGSIb3DQEJBwYFK4EEAAQGCWCGSAFlAwQCAg==
The EST client parses the OID's in the response and handles each OID
independently. When an OID indicates a known descriptive CSR
attribute type, the client SHOULD include the requested information
in the subsequent CSR that it submits, either in the CSR attributes
or in any other appropriate CSR field. When an OID indicates a
particular way to generate the CSR, the client SHOULD generate its
CSR according to the parsed OID. When an OID is of an unknown type
the OID MUST be ignored by the client.
5. IANA Considerations
(This section is incomplete)
IANA is requested to register the following:
IANA SHALL update the well-known URI registry with the following
filled-in template from [RFC5785].
URI suffix: est
Change controller: IETF
IANA SHALL update the Application Media Types registry with the
following filled-in template from [RFC4288].
The media subtype for Attributes in a CertificationRequest is
application/csrattrs.
Type name: application
Subtype name: csrattrs
Required parameters: None
Optional parameters: None
Encoding considerations: binary;
Security Considerations:
Clients request a list of attributes that servers wish to be in
certification requests. The request/response SHOULD be done in
a TLS-protected tunnel.
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Interoperability considerations: None
Published specification: This memo.
Applications which use this media type:
Enrollment over Secure Transport (EST)
Additional information:
Magic number(s): None
File extension: None
Macintosh File Type Code(s):
Person & email address to contact for further information:
Dan Harkins <dharkins@arubanetworks.com>
Restrictions on usage: None
Author: Dan Harkins <dharkins@arubanetworks.com>
Intended usage: COMMON
Change controller: The IESG
6. Security Considerations
Support for Basic authentication as specified in HTTP [RFC2617]
allows the server access to a client's cleartext password. This
provides support for legacy username/password databases but requires
exposing the plaintext password to the EST server. Use of a PIN or
one-time-password can help mitigate such exposure, but it is
RECOMMENDED that EST clients use such credentials only once to obtain
a client certificate (that will be used during future interactions
with the EST server).
When a client uses the Third-Party TA database for certificate
validation (see Section 3) then authorization proceeds as specified
in Section 3.6. In this situation, the client has validated the
server as being a certified-by-a-third-party responder for the URI
configured, but cannot verify that the responder is authorized to act
as an RA for the PKI in which the client is trying to enroll.
Clients using a third-party trust anchor database are RECOMMENDED to
only use TLS-based client authentication (to prevent exposing HTTP-
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based Client Authentication information). It is RECOMMENDED that
such clients include "Linking Identity and POP information"
(Section 3.5) in requests (to prevent such requests from being
forwarded to a real EST server by a MITM). Additionally it is
RECOMMENDED that the third-party trust anchor database used for EST
server authentication be carefully managed, to reduce the chance of a
third-party CA with poor certification practices from being trusted.
When using a certificate-less TLS cipher suite, the shared secret
used for authentication and authorization MUST be known only to the
two parties to the exchange: the client and the server. Any further
sharing of secrets voids the security afforded by a certificate-less
cipher suite. Exposure of a shared secret used by a certificate-less
cipher suite to a third-party enables client impersonation that can
results in corruption of a client's trust anchor database.
As described in CMC Section 6.7, "For keys that can be used as
signature keys, signing the certification request with the private
key serves as a POP on that key pair". The inclusion of tls-unique
within the certification request links the proof-of-possession to the
TLS proof-of-identity by enforcing that the POP operation occurred
while the TLS session was active. This implies to the server that
the authenticated client currently has access to the private key. If
the authenticated client is known to have specific capabilities, such
as hardware protection for authentication credentials and key
storage, this implication is strengthened but not proven.
The server-side key generation method allows keys to be transported
over the TLS connection to the client. The distribution of private
key material is inherently risky. Private key distribution uses the
encryption mode of the negotiated TLS cipher suite. Keys are not
protected by preferred key wrapping methods such as AES Key Wrap
[RFC3394] or as specified in [RFC5958] as encryption of the private
key beyond that provided by TLS is optional. It is RECOMMEND that
EST servers not support this operation by default. It is RECOMMENDED
that clients not request this service unless there is a compelling
operational benefit. Use of a third-party trust anchor database is
NOT RECOMMENDED when server-side key generation is employed. The use
of an encrypted CMS Server-side Key Generation Response is
RECOMMENDED.
Regarding the CSR attributes that the CA may list for inclusion in an
enrollment request, there are no real inherent security issues with
the content being conveyed but an adversary who is able to interpose
herself into the conversation could exclude attributes that a server
may want, include attributes that a server may not want, and render
meaningless other attributes that a server may want.
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7. References
7.1. Normative References
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2314] Kaliski, B., "PKCS #10: Certification Request Syntax
Version 1.5", RFC 2314, March 1998.
[RFC2585] Housley, R. and P. Hoffman, "Internet X.509 Public Key
Infrastructure Operational Protocols: FTP and HTTP",
RFC 2585, May 1999.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC2985] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object
Classes and Attribute Types Version 2.0", RFC 2985,
November 2000.
[RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
Request Syntax Specification Version 1.7", RFC 2986,
November 2000.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4108] Housley, R., "Using Cryptographic Message Syntax (CMS) to
Pritikin, et al. Expires August 15, 2013 [Page 36]
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Protect Firmware Packages", RFC 4108, August 2005.
[RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen,
"Internet X.509 Public Key Infrastructure Certificate
Management Protocol (CMP)", RFC 4210, September 2005.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", RFC 4288, December 2005.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC4945] Korver, B., "The Internet IP Security PKI Profile of
IKEv1/ISAKMP, IKEv2, and PKIX", RFC 4945, August 2007.
[RFC5054] Taylor, D., Wu, T., Mavrogiannopoulos, N., and T. Perrin,
"Using the Secure Remote Password (SRP) Protocol for TLS
Authentication", RFC 5054, November 2007.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, January 2008.
[RFC5272] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC)", RFC 5272, June 2008.
[RFC5273] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC): Transport Protocols", RFC 5273, June 2008.
[RFC5274] Schaad, J. and M. Myers, "Certificate Management Messages
over CMS (CMC): Compliance Requirements", RFC 5274,
June 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, September 2009.
[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
"Transport Layer Security (TLS) Renegotiation Indication
Extension", RFC 5746, February 2010.
Pritikin, et al. Expires August 15, 2013 [Page 37]
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[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
April 2010.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, July 2010.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
August 2010.
[RFC5967] Turner, S., "The application/pkcs10 Media Type", RFC 5967,
August 2010.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, March 2011.
[RFC6402] Schaad, J., "Certificate Management over CMS (CMC)
Updates", RFC 6402, November 2011.
[SHS] National Institute of Standards and Technology, "Federal
Information Processing Standard Publication 180-4: Secure
Hash Standard (SHS)", March 2012, <http://csrc.nist.gov/
publications/fips/fips180-4/fips-180-4.pdf>.
[X.680] ITU-T Recommendation, "ITU-T Recommendation X.680 Abstract
Syntax Notation One (ASN.1): Specification of basic
notation", November 2008,
<http://www.itu.int/rec/T-REC-X.680-200811-I/en>.
[X.690] ITU-T Recommendation, "ITU-T Recommendation X.690 ASN.1
encoding rules: Specification of Basic Encoding Rules
(BER), Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER)", November 2008,
<http://www.itu.int/rec/T-REC-X.690-200811-I/en>.
7.2. Informative References
[IDevID] IEEE Std, "IEEE 802.1AR Secure Device Identifier",
December 2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>.
[RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397,
August 1998.
[RFC2712] Medvinsky, A. and M. Hur, "Addition of Kerberos Cipher
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Suites to Transport Layer Security (TLS)", RFC 2712,
October 1999.
[RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, September 2002.
[RFC6403] Zieglar, L., Turner, S., and M. Peck, "Suite B Profile of
Certificate Management over CMS", RFC 6403, November 2011.
[SP-800-57-Part-1]
National Institute of Standards and Technology,
"Recommendation for Key Management - Part 1: General
(Revision 3)", July 2012, <http://csrc.nist.gov/
publications/nistpubs/800-57/
sp800-57_part1_rev3_general.pdf>.
[X.520] ITU-T Recommendation, "ITU-T Recommendation X.520 The
Directory: Selected attribute types", November 2008,
<http://www.itu.int/rec/T-REC-X.520-200811-I/en>.
Appendix A. Operational Scenario Example Messages
(informative)
This section expands on the Operational Scenario Overviews by
providing detailed examples of the messages at each TLS layer.
A.1. Obtaining CA Certificates
The following is an example of a valid /CACerts exchange.
During the initial TLS handshake the client can ignore the optional
server generated "certificate request" and can instead proceed with
the HTTP GET request:
GET /CACerts HTTP/1.1
User-Agent: curl/7.24.0 (i686-pc-linux-gnu) libcurl/7.24.0 OpenS
SL/0.9.8b zlib/1.2.3 libidn/0.6.5
Host: 127.0.0.1:8085
Accept: */*
In response the server provides the current CA certificate:
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<= Recv header, 38 bytes (0x26)
Content-Type: application/pkcs7-mime
== Info: no chunk, no close, no size. Assume close to signal end
<= Recv header, 2 bytes (0x2)
<= Recv data, 1111 bytes (0x457)
-----BEGIN PKCS7-----.MIIDEQYJKoZIhvcNAQcCoIIDAjCCAv4CAQExADALBg
kqhkiG9w0BBwGgggLkMIIC.4DCCAcigAwIBAgIJAOjxMZcXhE5wMA0GCSqGSIb3D
QEBBQUAMBcxFTATBgNVBAMT.DGVzdEV4YW1wbGVDQTAeFw0xMjA3MDQxODM5Mjda
Fw0xMzA3MDQxODM5MjdaMBcx.FTATBgNVBAMTDGVzdEV4YW1wbGVDQTCCASIwDQY
JKoZIhvcNAQEBBQADggEPADCC.AQoCggEBALQ7SjZSt6qrnBzUnBNj9z4oxYkvMA
Vh0OIOVRkNhz/2kDGsds0ne7cw.W33kYlxPba4psdLMixCT/O8ZQMpgA+QFKtwb9
VPE8EFUgGzxSYHQHjhJsbg0BVaN.Ya38vjKMjvosuSXUHwkvU57SInSkMr3/aNtS
T8qFfeC6Vuf/G/GLHGuHQKAy/DSo.206MjaMNmWYRVQQVErGookRA4GBF/YE+G/C
SlTsCQNE0KyBFz8JWIkgYY2gYkxb7.wWMvvhaU/Esp+2DG92v9Dhs2MRgrR+WPs7
Y6CYOLD5Mr5lEdkHg27IxkSAoRrI6D.fnVVEQGCj7QrrsUgfXFVYv6cCWFfhMcCA
wEAAaMvMC0wDAYDVR0TBAUwAwEB/zAd.BgNVHQ4EFgQUhH9KxW5TsjkgL7kg2kxJ
yy5tD/MwDQYJKoZIhvcNAQEFBQADggEB.AD+vydZo292XFb2vXojdKD57Gv4tKVm
hvXRdVInntzkY/0AyFCfHJ4BwndgtMh4t.rvBD8+8dL+W3jfPjcSCcUQ/JEnFuMn
b5+kivLeqOnUshETasFPBz2Xq4C1sHDno9.CWOcsjPPw08Tn4dSrzDBSq1NdXB2z
9NOpaVnbpb01qQGhXSOaEvcbZcDuGiW7Di3.gV++remokuPph/s6XoZffzc7ZVzf
Job6tS4RwNz01sutPybXiRWivOz7+QeCOT87.nTGlkQH/+RImUyJ2jefjAW/GDFT
Pzek6cZnabAtsg32n0Pv0j0/1RTNSdYGxPIVA.2f9fhMqMz+vm3w4CFNkGZnOhAD
EA.-----END PKCS7-----.
A.2. Certificate TLS authentication
The following is an example of a valid /simpleEnroll exchange.
During this exchange the EST client uses an existing certificate
issued by a thirt-party CA to obtain an initial certificate from the
EST server.
During the initial TLS handshake the server generated "certificate
request" includes both the distinguished name of the EST CA
("estExampleCA") and it includes the distinguished name of a third-
party CA ("estEXTERNALCA"):
0d 00 00 3d 03 01 02 40 00 37 00 1a 30 18 31 16 ...=...@.7..0.1.
30 14 06 03 55 04 03 13 0d 65 73 74 45 58 54 45 0...U....estEXTE
52 4e 41 4c 43 41 00 19 30 17 31 15 30 13 06 03 RNALCA..0.1.0...
55 04 03 13 0c 65 73 74 45 78 61 6d 70 6c 65 43 U....estExampleC
41 A
Which decodes as:
Acceptable client certificate CA names
/CN=estEXTERNALCA
/CN=estExampleCA
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The EST client provides a certificate issued by "estEXTERNALCA" in
the certificate response and the TLS handshake proceeds to
completion. The EST server accepts the EST client certificate for
authentication and accepts the EST client's POSTed certificate
request:
POST /simpleEnroll HTTP/1.1
User-Agent: curl/7.24.0 (i686-pc-linux-gnu) libcurl/7.24.0 OpenS
SL/0.9.8b zlib/1.2.3 libidn/0.6.5
Host: 127.0.0.1:8085
Accept: */*
Content-Type: application/pkcs10
Content-Length: 952
=> Send data, 952 bytes (0x3b8)
-----BEGIN CERTIFICATE REQUEST-----.MIIChjCCAW4CAQAwQTElMCMGA1UE
AxMccmVxIGJ5IGNsaWVudCBpbiBkZW1vIHN0.ZXAgNjEYMBYGA1UEBRMPUElEOld
pZGdldCBTTjo2MIIBIjANBgkqhkiG9w0BAQEF.AAOCAQ8AMIIBCgKCAQEAwhYyI+
aYezyx+kW0GVUbMKLf2BUd8BgGykkIJYxms6SH.Bv5S4ktcpYbEpR9iCmp96vK6a
Ar57ArZtMmi0Y6eLX4c+njJnYhUeTivnfyfMM5d.hNVwyzKbJagm5f+RLTMfp0y0
ykqrfZ1hFhcNrRzF6mJeaORTHBehMdu8RXcbmy5R.s+vjnUC4Fe3/oLHtXePyYv1
qqlkk0XDrw/+lx0y4Px5tiyb84iPnQOXjG2tuStM+.iEvfpNAnwU0+3GDjl3sjx0
+gTKvblp6Diw9NSaqIAKupcgWsA0JlyYkgPiJnXFKL.vy6rXoOyx3wAbGKLrKCxT
l+RH3oNXf3UCH70aD758QIDAQABoAAwDQYJKoZIhvcN.AQEFBQADggEBADwpafWU
BsOJ2g2oyHQ7Ksw6MwvimjhB7GhjweCcceTSLInUMk10.4E0TfNqaWcoQengMVZr
IcbOb+sa69BWNB/WYIULfEtJIV23/g3n/y3JltMNw/q+R.200t0bNAViijHQHmlF
6dt93tkRrTzXnhV70Ijnff08G7P9HfnXQH4Eiv3zOB6Pak.JoL7QlWQ+w5vHpPo6
WGH5n2iE+Ql76F0HykGeqaR402+ae0WlGLHEvcN9wiFQVKh.KUHteU10SEPijlqf
QW+hciLleX2CwuZY5MqKb4qqyDTs4HSQCBCl8jR2cXsGDuN4.PcMPp+9A1/UPuGD
jhwPt/K3y6aV8zUEh8Ws=.-----END CERTIFICATE REQUEST-----.
The EST server uses the trusted third party CA issued certificate to
perform additional authorization and issues a certificate to the
client:
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<= Recv header, 38 bytes (0x26)
Content-Type: application/pkcs7-mime
== Info: no chunk, no close, no size. Assume close to signal end
<= Recv header, 2 bytes (0x2)
<= Recv data, 1200 bytes (0x4b0)
-----BEGIN PKCS7-----.MIIDUQYJKoZIhvcNAQcCoIIDQjCCAz4CAQExADALBg
kqhkiG9w0BBwGgggMkMIID.IDCCAgigAwIBAgIBBjANBgkqhkiG9w0BAQUFADAXM
RUwEwYDVQQDEwxlc3RFeGFt.cGxlQ0EwHhcNMTIwNzA0MTgzOTM3WhcNMTMwNzA0
MTgzOTM3WjBBMSUwIwYDVQQD.ExxyZXEgYnkgY2xpZW50IGluIGRlbW8gc3RlcCA
2MRgwFgYDVQQFEw9QSUQ6V2lk.Z2V0IFNOOjYwggEiMA0GCSqGSIb3DQEBAQUAA4
IBDwAwggEKAoIBAQDCFjIj5ph7.PLH6RbQZVRswot/YFR3wGAbKSQgljGazpIcG/
lLiS1ylhsSlH2IKan3q8rpoCvns.Ctm0yaLRjp4tfhz6eMmdiFR5OK+d/J8wzl2E
1XDLMpslqCbl/5EtMx+nTLTKSqt9.nWEWFw2tHMXqYl5o5FMcF6Ex27xFdxubLlG
z6+OdQLgV7f+gse1d4/Ji/WqqWSTR.cOvD/6XHTLg/Hm2LJvziI+dA5eMba25K0z
6IS9+k0CfBTT7cYOOXeyPHT6BMq9uW.noOLD01JqogAq6lyBawDQmXJiSA+ImdcU
ou/Lqteg7LHfABsYousoLFOX5Efeg1d./dQIfvRoPvnxAgMBAAGjTTBLMAkGA1Ud
EwQCMAAwHQYDVR0OBBYEFJv4oLLeNxNK.OMmQDDujyNR+zaVPMB8GA1UdIwQYMBa
AFIR/SsVuU7I5IC+5INpMScsubQ/zMA0G.CSqGSIb3DQEBBQUAA4IBAQCMdomfdR
9vi4VUYdF+eym7F8qVUG/1jtjfaxmrzKeZ.7LQ1F758RtwG9CDu2GPHNPjjeM+DJ
RQZN999eLs3Qd/DIJCNimaqdDqmkeBFC5hq.LZOxbKhSmhlR7YKjIZuyI299rOaI
W54ULyz8k0zw6R1/0lMJTsDFGJM+9yDeaARE.n3vtKnUDGHsVU3fYpDENaqUunoU
MZfuEdejfHhU7lVbJI1oSJbnRwBFkPr/RQ3/5.FymcrBD9RpAM5MsQIn0BONil/o
JM+LjOJqyZLbBxz6P3w/OiJGYJNfFT8YudLfjZ.LDX8A8FFcReapNELC4QxE4OrA
hN3sQUT2O7ndIsit4kJoQAxAA==.-----END PKCS7-----.
A.3. Username/Password Distributed Out-of-Band
The following is an example of a valid /simpleEnroll exchange.
During this exchange the EST client uses an out-of-band distributed
username/password to authenticate itself to the EST server.
During the initial TLS handshake the client can ignore the optional
server generated "certificate request" and can instead proceed with
the HTTP POST request:
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POST /simpleEnroll HTTP/1.1
User-Agent: curl/7.24.0 (i686-pc-linux-gnu) libcurl/7.24.0 OpenS
SL/0.9.8b zlib/1.2.3 libidn/0.6.5
Host: 127.0.0.1:8085
Accept: */*
Content-Type: application/pkcs10
Content-Length: 952
=> Send data, 952 bytes (0x3b8)
-----BEGIN CERTIFICATE REQUEST-----.MIIChjCCAW4CAQAwQTElMCMGA1UE
AxMccmVxIGJ5IGNsaWVudCBpbiBkZW1vIHN0.ZXAgMjEYMBYGA1UEBRMPUElEOld
pZGdldCBTTjoyMIIBIjANBgkqhkiG9w0BAQEF.AAOCAQ8AMIIBCgKCAQEAz9lXz9
MowulOx0W5v1k7GKlsNy7mAgmkz/wZDImBDXez.QZCb8lrO8iTD3tI0NH2xpkY3b
uqFjdtQTzCmANLyNWtR1sC5GjN/EM1JSCrO/zZM.ig835RXJTP878N/jNW7EzSxb
/zK5OzKJoRbZ4HgZm4NDapMfMcB4jqBdPxoPAqeR.+KTkv1+9m1vvsdKIs5Hm4Sp
O2WolHPw5BCXdu5zleb6ACih7Zpd2cpHFz6ZHC0G1.Of+F//0BzkFSqWsmUomyJy
WCfLCuX9grs1CNlLxw0gcMprdTxLxjc18z03ZmBCq0.qq5/mUK/tv9R2k8+WuP3a
kzTUIkeHtcp6FVFl3D+TwIDAQABoAAwDQYJKoZIhvcN.AQEFBQADggEBAJH7Etuy
B/oQgQeals08mD2U31FfQ/uYqjNxzZpZJSzVLGMASv9a.pNzaWdfqPdIs+ZZ+gAQ
QkVcXjdbqY3pAf/EeWk+KnuAUjOIPKu3ZBPVbWbXu/Ie7.F1ekQ7TLkFNkHSxHRu
2/bPIByBLRVfWNVXd3wPq+QxqMqgIjBGaTJM5kuHndYFGj.Xdf4rlGRPyOOwG/Xf
QrKBB3tzpbJCy+cwOUAJFPOTO+86RUjf9Wh+yoM182vlg8O.FyEaaA/PMpl3aEcT
BlRZmPx4e7FLwGIhbgE7/6K0nF99xdGd7JYPHasbcWszxD0Z.oPYm+44g0gOnhlj
OWpRiKXcnngSSutRILaw=.-----END CERTIFICATE REQUEST-----.
== Info: upload completely sent off: 952 out of 952 bytes
== Info: HTTP 1.1 or later with persistent connection, pipelining
supported
The EST server accepts this request but since a client certificate
was not provided for authentication/authorization the EST server
responds with the WWW-authenticate header:
<= Recv header, 27 bytes (0x1b)
HTTP/1.1 401 Unauthorized
<= Recv header, 75 bytes (0x4b)
WWW-Authenticate: Digest qop="auth", realm="estrealm", nonce="13
41427174"
The EST client repeats the request, this time including the requested
Authorization header:
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== Info: SSL connection using AES256-SHA
== Info: Server certificate:
== Info: subject: CN=127.0.0.1
== Info: start date: 2012-07-04 18:39:27 GMT
== Info: expire date: 2013-07-04 18:39:27 GMT
== Info: common name: 127.0.0.1 (matched)
== Info: issuer: CN=estExampleCA
== Info: SSL certificate verify ok.
== Info: Server auth using Digest with user 'estuser'
=> Send header, 416 bytes (0x1a0)
POST /simpleEnroll HTTP/1.1
Authorization: Digest username="estuser", realm="estrealm", nonc
e="1341427174", uri="/simpleEnroll", cnonce="ODc0OTk2", nc=00000
001, qop="auth", response="48a2b671ccb6596adfef039e134b7d5d"
User-Agent: curl/7.24.0 (i686-pc-linux-gnu) libcurl/7.24.0 OpenS
SL/0.9.8b zlib/1.2.3 libidn/0.6.5
Host: 127.0.0.1:8085
Accept: */*
Content-Type: application/pkcs10
Content-Length: 952
=> Send data, 952 bytes (0x3b8)
-----BEGIN CERTIFICATE REQUEST-----.MIIChjCCAW4CAQAwQTElMCMGA1UE
AxMccmVxIGJ5IGNsaWVudCBpbiBkZW1vIHN0.ZXAgMjEYMBYGA1UEBRMPUElEOld
pZGdldCBTTjoyMIIBIjANBgkqhkiG9w0BAQEF.AAOCAQ8AMIIBCgKCAQEAz9lXz9
MowulOx0W5v1k7GKlsNy7mAgmkz/wZDImBDXez.QZCb8lrO8iTD3tI0NH2xpkY3b
uqFjdtQTzCmANLyNWtR1sC5GjN/EM1JSCrO/zZM.ig835RXJTP878N/jNW7EzSxb
/zK5OzKJoRbZ4HgZm4NDapMfMcB4jqBdPxoPAqeR.+KTkv1+9m1vvsdKIs5Hm4Sp
O2WolHPw5BCXdu5zleb6ACih7Zpd2cpHFz6ZHC0G1.Of+F//0BzkFSqWsmUomyJy
WCfLCuX9grs1CNlLxw0gcMprdTxLxjc18z03ZmBCq0.qq5/mUK/tv9R2k8+WuP3a
kzTUIkeHtcp6FVFl3D+TwIDAQABoAAwDQYJKoZIhvcN.AQEFBQADggEBAJH7Etuy
B/oQgQeals08mD2U31FfQ/uYqjNxzZpZJSzVLGMASv9a.pNzaWdfqPdIs+ZZ+gAQ
QkVcXjdbqY3pAf/EeWk+KnuAUjOIPKu3ZBPVbWbXu/Ie7.F1ekQ7TLkFNkHSxHRu
2/bPIByBLRVfWNVXd3wPq+QxqMqgIjBGaTJM5kuHndYFGj.Xdf4rlGRPyOOwG/Xf
QrKBB3tzpbJCy+cwOUAJFPOTO+86RUjf9Wh+yoM182vlg8O.FyEaaA/PMpl3aEcT
BlRZmPx4e7FLwGIhbgE7/6K0nF99xdGd7JYPHasbcWszxD0Z.oPYm+44g0gOnhlj
OWpRiKXcnngSSutRILaw=.-----END CERTIFICATE REQUEST-----.
The ESTserver uses the username/password to perform authentication/
authorization and responds with the issued certificate:
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<= Recv header, 38 bytes (0x26)
0000: Content-Type: application/pkcs7-mime
== Info: no chunk, no close, no size. Assume close to signal end
<= Recv header, 2 bytes (0x2)
<= Recv data, 1200 bytes (0x4b0)
-----BEGIN PKCS7-----.MIIDUQYJKoZIhvcNAQcCoIIDQjCCAz4CAQExADALBg
kqhkiG9w0BBwGgggMkMIID.IDCCAgigAwIBAgIBAjANBgkqhkiG9w0BAQUFADAXM
RUwEwYDVQQDEwxlc3RFeGFt.cGxlQ0EwHhcNMTIwNzA0MTgzOTM0WhcNMTMwNzA0
MTgzOTM0WjBBMSUwIwYDVQQD.ExxyZXEgYnkgY2xpZW50IGluIGRlbW8gc3RlcCA
yMRgwFgYDVQQFEw9QSUQ6V2lk.Z2V0IFNOOjIwggEiMA0GCSqGSIb3DQEBAQUAA4
IBDwAwggEKAoIBAQDP2VfP0yjC.6U7HRbm/WTsYqWw3LuYCCaTP/BkMiYENd7NBk
JvyWs7yJMPe0jQ0fbGmRjdu6oWN.21BPMKYA0vI1a1HWwLkaM38QzUlIKs7/NkyK
DzflFclM/zvw3+M1bsTNLFv/Mrk7.MomhFtngeBmbg0Nqkx8xwHiOoF0/Gg8Cp5H
4pOS/X72bW++x0oizkebhKk7ZaiUc./DkEJd27nOV5voAKKHtml3ZykcXPpkcLQb
U5/4X//QHOQVKpayZSibInJYJ8sK5f.2CuzUI2UvHDSBwymt1PEvGNzXzPTdmYEK
rSqrn+ZQr+2/1HaTz5a4/dqTNNQiR4e.1ynoVUWXcP5PAgMBAAGjTTBLMAkGA1Ud
EwQCMAAwHQYDVR0OBBYEFChDQpKEfG9c.e4JaMf8438tb2XOIMB8GA1UdIwQYMBa
AFIR/SsVuU7I5IC+5INpMScsubQ/zMA0G.CSqGSIb3DQEBBQUAA4IBAQAn42mIVG
piaY4yqFD0F8KyUhKsdNnyKeeISQxP//lp.quIieJzdWSc7bhWZNldSzNswCod8B
4eJToQejLSNb8JBDC849z0tcuyHgN6N/p8z.IwI+hAlfXS9q02OECyFes4Jmzc7r
erE5jtOdGsEDBIscw/A+Kv86wv6BKbagMslQ.51AJyPsL6iBhm7LPFrErJgH2kWN
jDKFH9CcVFjXvgriMrLPFeqQWOpj/2XF+4m+c.f9QP5tSjieHJR1hnYk2tlodfE7
iV4pJ07Mmf3yBf753VSUVybqWiMCd0Lm7oghSX.E2GAxrsU1N+N1odn+gJ2wmxTu
AC2aHt9VPRViov4RRTvoQAxAA==.-----END PKCS7-----.
A.4. Re-Enrollment
The following is an example of a valid /simpleReEnroll exchange.
During this exchange the EST client authenticates itself using an
existing certificate issued by the EST CA.
Initially this exchange is identical to enrollment using an
externally issued certificate for client authentication since the
server is not yet aware of the client's intention. As in that
example the EST server the server generated "certificate request"
includes both the distinguished name of the CA the EST server
provides services for ("estExampleCA") and it includes the
distinguished name of a trusted third party CA ("estEXTERNALCA").
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0d 00 00 3d 03 01 02 40 00 37 00 1a 30 18 31 16 ...=...@.7..0.1.
30 14 06 03 55 04 03 13 0d 65 73 74 45 58 54 45 0...U....estEXTE
52 4e 41 4c 43 41 00 19 30 17 31 15 30 13 06 03 RNALCA..0.1.0...
55 04 03 13 0c 65 73 74 45 78 61 6d 70 6c 65 43 U....estExampleC
41 A
In text format this is:
Acceptable client certificate CA names
/CN=estEXTERNALCA
/CN=estExampleCA
The EST client provides a certificate issued by "estExampleCA" in the
certificate response and the TLS handshake proceeds to completion.
The EST server accepts the EST client certificate for authentication
and accepts the EST client's POSTed certificate request.
The rest of the protocol traffic is effectively identical to a normal
enrollment.
A.5. Server Key Generation
The following is an example of a valid /serverKeyGen exchange.
During this exchange the EST client authenticates itself using an
existing certificate issued by the CA the EST server provides
services for.
The initial TLS handshake is identical to the enrollment example
handshake. The HTTP POSTed message is:
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POST /serverKeyGen HTTP/1.1
User-Agent: curl/7.24.0 (i686-pc-linux-gnu) libcurl/7.24.0 OpenS
SL/0.9.8b zlib/1.2.3 libidn/0.6.5
Host: 127.0.0.1:8085
Accept: */*
Content-Type: application/pkcs10
Content-Length: 968
=> Send data, 968 bytes (0x3c8)
-----BEGIN CERTIFICATE REQUEST-----.MIICkzCCAXsCAQAwTjEyMDAGA1UE
AxMpc2VydmVyS2V5R2VuIHJlcSBieSBjbGll.bnQgaW4gZGVtbyBzdGVwIDUxGDA
WBgNVBAUTD1BJRDpXaWRnZXQgU046NTCCASIw.DQYJKoZIhvcNAQEBBQADggEPAD
CCAQoCggEBAMnlUlq0ag/fDAVhLgrXEAD6WtZw.Y2rVGev5saWirer2n0OzghB59
uJByxPo0DYBYqZRuoRF0FTL1ZZTMaZxivge0ecA.ZcoR46jwSBoceMT1jkwFyAER
t9Q2EwdnJLIPo/Ib2PLJNb4Jo8NNKmxtg55BgIVi.vkIB+rMtLeYRUVL0RUaBAqX
FmtXRDceVFIEY24iUQw6vESGJKpArht592aT8lyaP.24bZovuG19dd5xtTX3j37K
x49SlkUvLSpD6ZavIFAZn7Yv19LBKHvRIemybUo294.QeLb/VYP1O+EAthV/igiX
1DHqlUZCZp5SdyUXUwZPatFboNwEVR0R3MJwVECAwEA.AaAAMA0GCSqGSIb3DQEB
BQUAA4IBAQAqhHezK5/tvbXleHO/aTBVYO9l414NM+WA.wJcnS2UaJYScPBqlYK/
gij+dqAtFE+5ukAj56t7HnooI4EFo9r8jqCHewx7iLZYh.JDxo4hWOsAvHV+Iziy
jkhJNdHBIqGM7Gd5f/2VJLEPQPmwNOL5P+2O4eQC/QeEYc.bAmfhOS8b/ZH09/9T
PeaeQpjspjOui/100OuLE8KvU3FM0sXMYt1Va0A0jxzl+5k.EiEJo+ltXsQwdP0H
csoTNBN+j3K18omJQS0e91X8v0xkMWYhUtonXD0YZ6SO/B9c.AE6GTADHA/xpSvA
cqlWa+FHxjwEMXdmViHvMUywo31fDZ/TUvCPX.-----END CERTIFICATE REQUE
ST-----.
Because the DecryptKeyIdentifier attribute is not included in the
request the response does not include additional encryption beyond
the TLS session. The EST server response is:
<= Recv header, 17 bytes (0x11)
HTTP/1.1 200 OK
<= Recv header, 16 bytes (0x10)
Status: 200 OK
<= Recv header, 67 bytes (0x43)
Content-Type: multipart/mixed ; boundary=estServerExampleBoundar
y
== Info: no chunk, no close, no size. Assume close to signal end
<= Recv header, 2 bytes (0x2)
<= Recv data, 3234 bytes (0xca2)
This is the preamble. It is to be ignored, though it.is a handy
place for estServer to include an explanatory note.including con
tact or support information..--estServerExampleBoundary.Content-
Type=application/pkcs8..-----BEGIN PRIVATE KEY-----.MIIEvQIBADAN
BgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQC0781l7tri0yii.Mb9ZZYch8ze
izXrjMPF/Rxoz2C9IU2THCrhPGXGQMne/zivce0m8/BMkkUc+DsSM.tzxn4l+9tI
sVDkAe4FyzN0hLd/zawgj6kUoCi3mxZnb2rWaRYAmM5w41ImDV3blv.aMUKDSJhV
bQ+z/G1W1TRx3iWi5CMHYb+1pJXPTJz/GuWr/b/+Efqwz2ZlwGcj4Dx.Igbx9vG0
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mftIIxM4TUX28KBbaLgJbalsiuOx3C2bEyaSPerdzqgvXFHGGAhg1FU8.DQiQEki
nn66GPMtm1SNgitxFxWouFqpsax5MWn/i52TfEaF2PNThOuzKtilweJhk.g0gMIQ
TXAgMBAAECggEANlrz8XNX/lxBELixK0H83o4aYKYqDKZfZkUN8hU33xpu.Y/0sc
VbLbu46WzysoIfJFyUC+zFJnbMCCOPjGbI/4NWkEqc9TAlKz+wDo+hf5bf0.ypFr
EmikHk8R3fkpnvKi69ldw0iYnqcFVhq7VtGrSmJcy6Hckwbk7EBoUZGL0wtp.xlO
6XlhksAvn8+75qoWzsNhi7S/L0IVCVLbUaV3hodTHlH5M4daFbqyRWD7UiPKt.Q3
hdw1rpyVZg8ZbBFp0Ej4f9GdRaq88SIKMKCDu3t9ibn/v1kEte+PxhuwyW+d0o.h
kKSEW0yLKCzQm5tujsPq0UVzPBkLJACUnFAi+a4AQKBgQDu6VLH2eYoTjPPTyAv.
vOJnNWP7oMzyJ4/eFqdE9m+2Ajm/0qaMY95ftZ+GpEKggvC6Z5DFevEmgH4Sg2+G
.gFd93diyRPScVbNE8SmpXxLPU2UoykVmICuQZzLDNE18B3buxAm2GJ219NEnZOe
c.jPMOV/IcG1aLzTqQssL3zo/0gQKBgQDB4Olpg3EBggtJ/+dlkLHUw8c7Pe3UyL
kS.VxVsyQwioYt8xMeCWuPvPNFcOjcW53KN/YSpCVjpttKGsPtLibMlKYKgasEqg
cvl.Vb5OFtA/jNAP3mdAgCzBn6IF1NhVQe2dclo5puZ0gO38HDWq7EtqSi9Q0JSM
g3YC.QNcOORptVwKBgQCHrCafaYWDhA11/+g2U9x6Yd56ifF43rCbnV+2EQCVaqQ
i49xC.w4AH+Bs0mdlgT5unL6MOEmgZxkRR/SP7TKzixHYHnpMOqLhaQV24Wk5TQH
ek92D7.wu8aXRB9vBj4g0CuDNO6/jWpm/KenXXN+Fka3ySVg4zdbVmBzJJdqYckg
QKBgFXS.zSBzGgwz1/F7AaDZK49m1wPnhyeBb0OqHwbX/LI71rZ1mWef+nSF9Juh
/Y77B5/J.UPdO9vgGgS00nRk0LIRP2s5OU5IQgQTVLvf8a1UmbVgI+KX511Yi5yM
ztEwRcjEX.VM9ejXeXN0I57pvqG/xCOK3Kl2eYLh4TO9/E8WjjAoGAA1mqUV4Hnf
4yvF1rydMp.fpvoWekiiRE33iEbYZNATYhsl7uxwn760pqVifkq2DSrZeYm4+lw9
jwWMtUoPzpg.CJYMoGl846nhiZrbbJ5b5twoLV6GRmkk/CfOxPXNzCtSoQA86HHq
7rRdhXSau/bY.EXc91tnhLjFzZxdBgrd+f4k=.-----END PRIVATE KEY-----.
--estServerExampleBoundary.Content-Type: application/pkcs7-mime.
.-----BEGIN PKCS7-----.MIIDPAYJKoZIhvcNAQcCoIIDLTCCAykCAQExADALB
gkqhkiG9w0BBwGgggMPMIID.CzCCAfOgAwIBAgIBBTANBgkqhkiG9w0BAQUFADAX
MRUwEwYDVQQDEwxlc3RFeGFt.cGxlQ0EwHhcNMTIwNzA0MTgzOTM2WhcNMTMwNzA
0MTgzOTM2WjAsMSowKAYDVQQD.EyFzZXJ2ZXJzaWRlIGtleSBnZW5lcmF0ZWQgcm
VzcG9uc2UwggEiMA0GCSqGSIb3.DQEBAQUAA4IBDwAwggEKAoIBAQC0781l7tri0
yiiMb9ZZYch8zeizXrjMPF/Rxoz.2C9IU2THCrhPGXGQMne/zivce0m8/BMkkUc+
DsSMtzxn4l+9tIsVDkAe4FyzN0hL.d/zawgj6kUoCi3mxZnb2rWaRYAmM5w41ImD
V3blvaMUKDSJhVbQ+z/G1W1TRx3iW.i5CMHYb+1pJXPTJz/GuWr/b/+Efqwz2Zlw
Gcj4DxIgbx9vG0mftIIxM4TUX28KBb.aLgJbalsiuOx3C2bEyaSPerdzqgvXFHGG
Ahg1FU8DQiQEkinn66GPMtm1SNgitxF.xWouFqpsax5MWn/i52TfEaF2PNThOuzK
tilweJhkg0gMIQTXAgMBAAGjTTBLMAkG.A1UdEwQCMAAwHQYDVR0OBBYEFLylcQN
0D5xTfRdayv+0GDULR2+EMB8GA1UdIwQY.MBaAFIR/SsVuU7I5IC+5INpMScsubQ
/zMA0GCSqGSIb3DQEBBQUAA4IBAQButIeM.DB9PkwlGGe7zqvUWVD8y99zowwV6A
rAOXWX+JO0bihgMtZaUfvPCX/LhZVEKDAki.W5orjAEvIu10b6l38ZzX2oyJgkYy
Mmbb14lzTsRyjiqFw9j1PXxwgZvhwcaCF4b7.eDUUBQIeZg3AnkQrEwnHR5oVIN5
8qo0P7PSKC3Vl3H6DlQh3y7w87nN12923/wk0.v/bS3lv7lDX3HdmbQD1r2KPtBs
JGF4jMdstT7FTx32ZFKObycbK7WJ4LHytNJDci.4iXf+B0S3D6Zbf1cXj80/W+jC
GvU0+4SV3cgEXFE5VQvXd8x40W4h0dTSkQCDPOS.nPj4Dl/PsLqX3lDboQAxAA==
.-----END PKCS7-----.--estServerExampleBoundary--.This is the ep
ilogue. It is also to be ignored..
In text format this is:
HTTP/1.1 200 OK
Status: 200 OK
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Content-Type: multipart/mixed ; boundary=estServerExampleBoundary
This is the preamble. It is to be ignored, though it
is a handy place for estServer to include an explanatory note
including contact or support information.
--estServerExampleBoundary
Content-Type=application/pkcs8
-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----
--estServerExampleBoundary
Content-Type: application/pkcs7-mime
-----BEGIN PKCS7-----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aLgJbalsiuOx3C2bEyaSPerdzqgvXFHGGAhg1FU8DQiQEkinn66GPMtm1SNgitxF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-----END PKCS7-----
--estServerExampleBoundary--
This is the epilogue. It is also to be ignored.
A.6. CSR Attributes
The following is an example of a valid /CSRAttrs exchange. During
this exchange the EST client authenticates itself using an existing
certificate issued by the CA the EST server provides services for.
The initial TLS handshake is identical to the enrollment example
handshake. The HTTP GET request:
GET /CSRAttrs HTTP/1.1
User-Agent: curl/7.22.0 (i686-pc-linux-gnu) libcurl/7.22.0 OpenS
SL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3
Host: 127.0.0.1:8085
Accept: */*
In response the server provides suggested attributes that are
appropriate for the authenticated client:
<= Recv header, 36 bytes (0x24)
Content-Type: application/csrattrs
== Info: no chunk, no close, no size. Assume close to signal end
<= Recv header, 2 bytes (0x2)
<= Recv data, 33 bytes (0x21)
0000: MBQGBysGAQEBARYGCSqGSIb3DQEJBw==.
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Authors' Addresses
Max Pritikin (editor)
Cisco Systems, Inc.
510 McCarthy Drive
Milpitas, CA 95035
USA
Email: pritikin@cisco.com
Peter E. Yee (editor)
AKAYLA, Inc.
7150 Moorland Drive
Clarksville, MD 21029
USA
Email: peter@akayla.com
Dan Harkins (editor)
Aruba Networks
1322 Crossman Avenue
Sunnyvale, CA 94089-1113
USA
Email: dharkins@arubanetworks.com
Pritikin, et al. Expires August 15, 2013 [Page 51]
