Remote Procedure Call Version 2 Encryption By Default
draft-cel-nfsv4-rpc-tls-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|
|---|---|---|---|
| Authors | Trond Myklebust , Chuck Lever | ||
| Last updated | 2018-11-12 | ||
| Replaced by | draft-ietf-nfsv4-rpc-tls, draft-ietf-nfsv4-rpc-tls, RFC 9289 | ||
| RFC stream | (None) | ||
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draft-cel-nfsv4-rpc-tls-00
Network File System Version 4 T. Myklebust
Internet-Draft Hammerspace
Updates: 5531 (if approved) C. Lever, Ed.
Intended status: Standards Track Oracle
Expires: May 16, 2019 November 12, 2018
Remote Procedure Call Version 2 Encryption By Default
draft-cel-nfsv4-rpc-tls-00
Abstract
This document proposes a mechanism that makes it possible to enable
in-transit encryption of Remote Procedure Call traffic with little
administrative overhead and full compatibility with implementations
that do not support it.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 16, 2019.
Copyright Notice
Copyright (c) 2018 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. RPC on TLS in Operation . . . . . . . . . . . . . . . . . . . 4
3.1. Discovering Server-side TLS Support . . . . . . . . . . . 4
3.2. Streams and Datagrams . . . . . . . . . . . . . . . . . . 5
3.3. Authentication . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 7
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
In 2014, the IETF published [RFC7258] which recognized that
unauthorized observation of network traffic had become widespread,
and was a subversive threat to all who make use of the Internet at
large. It strongly recommended that newly defined Internet protocols
make a real effort to mitigate monitoring attacks. Typically this
mitigation is done by encrypting data in transit.
The Remote Procedure Call version 2 protocol has been around for more
than a decade [RFC5531]. Support for in-transit encryption of RPC
was introduced with RPCSEC GSS [RFC7861]. However, experience has
shown that RPCSEC GSS is challenging to deploy, especially in
environments where:
o Per-host administrative or deployment costs must be kept to a
minimum,
o Parts of the RPC header that remain in clear-text are a security
exposure,
o Host CPU resources are at a premium, or
o Host identity management is carried out in a security domain that
is distinct from user identity management.
However strong a privacy service is, it is not effective if it cannot
be deployed in typical environments.
An alternative approach is to employ a transport layer security
mechanism that can protect the privacy of each RPC connection
transparently to RPC and Upper Layer protocols. The Transport Layer
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Security protocol [RFC8446] (TLS) is a well-established Internet
building block that protects many common Internet protocols such as
https [RFC2818].
Encrypting at the RPC transport layer enables several significant
benefits.
Encryption By Default
With the use of pre-shared keys, in-transit encryption can be
enabled immediately after installation without additional
administrative actions such as identifying the host system to a
trust authority, generating additional key material, or
provisioning a secure network tunnel.
Protection of Existing Protocols
The imposition of encryption at the transport layer protects any
Upper Layer protocol that employs RPC without alteration of that
protocol. RPC transport layer encryption can protect recent
versions of NFS such as NFS version 4.2 [RFC7862] and indeed
legacy NFS versions such as NFS version 3 [RFC1813] and NFS side-
band protocols such as the MNT protocol [RFC1813].
Decoupled User and Host Identities
RPCSEC GSS provides a framework for cryptographically protecting
user and host identities, but assumes that both are managed by the
same security authority.
Encryption Offload
The use of a well-established transport encryption mechanism that
is also employed by other very common network protocols makes it
possible to use hardware encryption implementations so that the
host CPU is not burdened with the work of encrypting and
decrypting large RPC arguments and results.
This document adopts the terminology introduced in Section 3 of
[RFC6973], and assumes a working knowledge of the Remote Procedure
Call (RPC) version 2 protocol [RFC5531] and the Transport Layer
Security (TLS) version 1.3 protocol [RFC8446].
2. Requirements Language
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] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
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3. RPC on TLS in Operation
3.1. Discovering Server-side TLS Support
The mechanism described in this document interoperates fully with
implementations that do not support it. Encryption (TLS) is
automatically disabled in these cases. To achieve this, we introduce
a new authentication flavor called AUTH_TLS.
<CODE BEGINS>
enum auth_flavor {
AUTH_NONE = 0,
AUTH_SYS = 1,
AUTH_SHORT = 2,
AUTH_DH = 3,
AUTH_KERB = 4,
AUTH_RSA = 5,
RPCSEC_GSS = 6,
AUTH_TLS = 7,
/* and more to be defined */
};
<CODE ENDS>
This new flavor is used to signal that the client wants to initiate
TLS security negotiation if the server supports it. The length of
the opaque data constituting the credential MUST be zero. The
verifier accompanying the credential MUST be an AUTH_NONE verifier of
length zero. The flavor value of the verifier received in the reply
message from the server MUST be AUTH_NONE. The bytes of the
verifier's string encode the fixed ASCII characters "STARTTLS".
When an RPC client is ready to initiate TLS negotiation, it sends a
NULL RPC request with an auth_flavor of AUTH_TLS. The server can
respond in one of three ways:
o If the server does not recognise the AUTH_TLS authentication
flavor, it responds with a reject_stat of AUTH_ERROR. The client
then knows that this server does not support TLS.
o If the server accepts the NULL RPC procedure, but fails to return
an AUTH_NONE verifier containing the string "STARTTLS", the client
knows that this server does not support TLS.
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o If the server accepts the NULL RPC procedure, and returns an
AUTH_NONE verifier containing the string "STARTTLS", the client
MAY proceed with TLS security negotiation.
If a client attempts to use AUTH_TLS for anything other than the NULL
RPC procedure, the server responds with a reject_stat of AUTH_ERROR.
Once TLS security negotiation is complete, the client and server will
have established a secure channel for communicating and can proceed
to use standard security flavours within that channel, presumably
after negotiating down the irrelevant RPCSEC_GSS privacy and
integrity services and applying channel binding.
If TLS negotiation fails for any reason (for example the server
rejects the certificate presented by the client), the RPC client
reports this failure to the calling application the same way it would
report an AUTH_ERROR rejection from the server.
3.2. Streams and Datagrams
RPC commonly operates on stream transports and datagram transports.
When operating on a stream transport, using TLS [RFC8446] is
appropriate. On a datagram transport, RPC should use DTLS [RFC6347].
RPC-over-RDMA [RFC8166] may make use of transport layer security
below the RDMA transport layer.
3.3. Authentication
Both RPC and TLS have their own in-built forms of host and user
authentication. Each have their strengths and weaknesses. We
believe the combination of host authentication via TLS and user
authentication via RPC provides optimal security, efficiency, and
flexibility, although many combinations are possible.
TLS Encryption-only with AUTH_SYS: A pre-shared key enables TLS
encryption. The RPC client uses AUTH_SYS to identify users with
the guarantee that the UID and GID values cannot be observed or
altered in transit.
TLS Encryption-only with RPCSEC GSS Kerberos: A pre-shared key
enables TLS encryption in encryption-only mode. The RPC client
uses Kerberos to identify the client host and its users, and does
not need to additionally require costly GSS integrity or privacy
services.
TLS per-client certificate with AUTH_SYS: During TLS negotiation,
the client identifies itself to the server with a unique
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certificate. The server can use this identity to perform
additional authorization of the client's requests.
TLS per-user certificate with AUTH_NONE: Each user establishes her
own TLS context with the server, identified by a unique
certficate. There is no need for any additional information at
the RPC layer, so the RPC client can use the simplest
authentication flavor for RPC transactions.
4. Security Considerations
One purpose of the mechanism described in this document is to protect
RPC-based applications against threats to the privacy of RPC
transactions and RPC user identities. A taxonomy of these threats
appears in Section 5 of [RFC6973]. In addition, Section 6 of
[RFC7525] contains a detailed discussion of technologies used in
conjunction with TLS. Implementers should familiarize themselves
with these materials.
The NFS version 4 protocol permits more than one user to use an NFS
client at the same time [RFC7862]. Typically that NFS client will
conserve connection resources by routing RPC transactions from all of
its users over a few or a single connection. In circumstances where
the users on that NFS client belong to multiple distinct security
domains, it may be necessary to establish separate TLS-protected
connections that do not share the same encryption parameters.
5. IANA Considerations
This document does not require actions by IANA.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5531] Thurlow, R., "RPC: Remote Procedure Call Protocol
Specification Version 2", RFC 5531, DOI 10.17487/RFC5531,
May 2009, <https://www.rfc-editor.org/info/rfc5531>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
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[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>.
[RFC7861] Adamson, A. and N. Williams, "Remote Procedure Call (RPC)
Security Version 3", RFC 7861, DOI 10.17487/RFC7861,
November 2016, <https://www.rfc-editor.org/info/rfc7861>.
[RFC8166] Lever, C., Ed., Simpson, W., and T. Talpey, "Remote Direct
Memory Access Transport for Remote Procedure Call Version
1", RFC 8166, DOI 10.17487/RFC8166, June 2017,
<https://www.rfc-editor.org/info/rfc8166>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
6.2. Informative References
[LJNL] Fisher, C., "Encrypting NFSv4 with Stunnel TLS", August
2018, <https://www.linuxjournal.com/content/
encrypting-nfsv4-stunnel-tls>.
[RFC1813] Callaghan, B., Pawlowski, B., and P. Staubach, "NFS
Version 3 Protocol Specification", RFC 1813,
DOI 10.17487/RFC1813, June 1995,
<https://www.rfc-editor.org/info/rfc1813>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/info/rfc6973>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
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[RFC7862] Haynes, T., "Network File System (NFS) Version 4 Minor
Version 2 Protocol", RFC 7862, DOI 10.17487/RFC7862,
November 2016, <https://www.rfc-editor.org/info/rfc7862>.
Acknowledgments
Special mention goes to Charles Fisher, author of "Encrypting NFSv4
with Stunnel TLS" [LJNL]. His article inspired the mechanism
described in this document.
The authors wish to thank Bill Baker, David Black, Benjamin Kaduk
Greg Marsden, David Noveck, and Justin Mazzola Paluska for their
input and support of this work.
Special thanks go to Transport Area Director Spencer Dawkins, NFSV4
Working Group Chairs Spencer Shepler and Brian Pawlowski, and NFSV4
Working Group Secretary Thomas Haynes for their guidance and
oversight.
Authors' Addresses
Trond Myklebust
Hammerspace Inc
4300 El Camino Real Ste 105
Los Altos, CA 94022
United States of America
Email: trond.myklebust@hammerspace.com
Charles Lever (editor)
Oracle Corporation
1015 Granger Avenue
Ann Arbor, MI 48104
United States of America
Email: chuck.lever@oracle.com
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