draft-ietf-nfsv4-rpc-tls-06.txt   draft-ietf-nfsv4-rpc-tls-07.txt 
Network File System Version 4 T. Myklebust Network File System Version 4 T. Myklebust
Internet-Draft Hammerspace Internet-Draft Hammerspace
Updates: 5531 (if approved) C. Lever, Ed. Updates: 5531 (if approved) C. Lever, Ed.
Intended status: Standards Track Oracle Intended status: Standards Track Oracle
Expires: August 6, 2020 February 3, 2020 Expires: November 1, 2020 April 30, 2020
Towards Remote Procedure Call Encryption By Default Towards Remote Procedure Call Encryption By Default
draft-ietf-nfsv4-rpc-tls-06 draft-ietf-nfsv4-rpc-tls-07
Abstract Abstract
This document describes a mechanism that, through the use of This document describes a mechanism that, through the use of
opportunistic Transport Layer Security (TLS), enables encryption of opportunistic Transport Layer Security (TLS), enables encryption of
in-transit Remote Procedure Call (RPC) transactions while in-transit Remote Procedure Call (RPC) transactions while
interoperating with ONC RPC implementations that do not support this interoperating with ONC RPC implementations that do not support this
mechanism. This document updates RFC 5531. mechanism. This document updates RFC 5531.
Status of This Memo Status of This Memo
skipping to change at page 1, line 35 skipping to change at page 1, line 35
Internet-Drafts are working documents of the Internet Engineering 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 Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 6, 2020. This Internet-Draft will expire on November 1, 2020.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. RPC-Over-TLS in Operation . . . . . . . . . . . . . . . . . . 5 4. RPC-Over-TLS in Operation . . . . . . . . . . . . . . . . . . 5
4.1. Discovering Server-side TLS Support . . . . . . . . . . . 5 4.1. Discovering Server-side TLS Support . . . . . . . . . . . 6
4.2. Authentication . . . . . . . . . . . . . . . . . . . . . 7 4.2. Authentication . . . . . . . . . . . . . . . . . . . . . 7
4.2.1. Using TLS with RPCSEC GSS . . . . . . . . . . . . . . 8 4.2.1. Using TLS with RPCSEC GSS . . . . . . . . . . . . . . 8
5. TLS Requirements . . . . . . . . . . . . . . . . . . . . . . 8 5. TLS Requirements . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Base Transport Considerations . . . . . . . . . . . . . . 8 5.1. Base Transport Considerations . . . . . . . . . . . . . . 9
5.1.1. Operation on TCP . . . . . . . . . . . . . . . . . . 8 5.1.1. Protected Operation on TCP . . . . . . . . . . . . . 9
5.1.2. Operation on UDP . . . . . . . . . . . . . . . . . . 9 5.1.2. Protected Operation on UDP . . . . . . . . . . . . . 9
5.1.3. Operation on Other Transports . . . . . . . . . . . . 9 5.1.3. Protected Operation on Other Transports . . . . . . . 10
5.2. TLS Peer Authentication . . . . . . . . . . . . . . . . . 10 5.2. TLS Peer Authentication . . . . . . . . . . . . . . . . . 11
5.2.1. X.509 Certificates Using PKIX trust . . . . . . . . . 10 5.2.1. X.509 Certificates Using PKIX trust . . . . . . . . . 11
5.2.2. X.509 Certificates Using Fingerprints . . . . . . . . 11 5.2.2. X.509 Certificates Using Fingerprints . . . . . . . . 12
5.2.3. Pre-Shared Keys . . . . . . . . . . . . . . . . . . . 11 5.2.3. Pre-Shared Keys . . . . . . . . . . . . . . . . . . . 12
5.2.4. Token Binding . . . . . . . . . . . . . . . . . . . . 11 5.2.4. Token Binding . . . . . . . . . . . . . . . . . . . . 13
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 12 6. Implementation Status . . . . . . . . . . . . . . . . . . . . 13
6.1. DESY NFS server . . . . . . . . . . . . . . . . . . . . . 12 6.1. DESY NFS server . . . . . . . . . . . . . . . . . . . . . 13
6.2. Hammerspace NFS server . . . . . . . . . . . . . . . . . 12 6.2. Hammerspace NFS server . . . . . . . . . . . . . . . . . 14
6.3. Linux NFS server and client . . . . . . . . . . . . . . . 13 6.3. Linux NFS server and client . . . . . . . . . . . . . . . 14
6.4. FreeBSD NFS server and client . . . . . . . . . . . . . . 13 6.4. FreeBSD NFS server and client . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7.1. Limitations of an Opportunistic Approach . . . . . . . . 14 7.1. Limitations of an Opportunistic Approach . . . . . . . . 15
7.1.1. STRIPTLS Attacks . . . . . . . . . . . . . . . . . . 14 7.1.1. STRIPTLS Attacks . . . . . . . . . . . . . . . . . . 15
7.2. TLS Identity Management on Clients . . . . . . . . . . . 14 7.1.2. Privacy Leakage Before Session Establishment . . . . 16
7.3. Security Considerations for AUTH_SYS on TLS . . . . . . . 15 7.2. TLS Identity Management on Clients . . . . . . . . . . . 16
7.4. Best Security Policy Practices . . . . . . . . . . . . . 16 7.3. Security Considerations for AUTH_SYS on TLS . . . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7.4. Best Security Policy Practices . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . 16 8.1. RPC Authentication Flavor . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . 18 8.2. ALPN Identifier for SUNRPC . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . 20
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Appendix A. Known Weaknesses of the AUTH_SYS Authentication Appendix A. Known Weaknesses of the AUTH_SYS Authentication
Flavor . . . . . . . . . . . . . . . . . . . . . . . 19 Flavor . . . . . . . . . . . . . . . . . . . . . . . 21
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 20 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction 1. Introduction
RFC Editor: Please remove this Editor's Note and the following
paragraph before this document is published.
The source for this draft is maintained in GitHub. Suggested changes
should be submitted as pull requests at
https://github.com/chucklever/i-d-rpc-tls [1]. Instructions are on
that page as well. Editorial changes can be managed in GitHub, but
any substantive change should be discussed on the nfsv4@ietf.org
mailing list.
In 2014 the IETF published [RFC7258], which recognized that In 2014 the IETF published [RFC7258], which recognized that
unauthorized observation of network traffic had become widespread and unauthorized observation of network traffic had become widespread and
was a subversive threat to all who make use of the Internet at large. was a subversive threat to all who make use of the Internet at large.
It strongly recommended that newly defined Internet protocols should It strongly recommended that newly defined Internet protocols should
make a genuine effort to mitigate monitoring attacks. Typically this make a genuine effort to mitigate monitoring attacks. Typically this
mitigation is done by encrypting data in transit. mitigation is done by encrypting data in transit.
The Remote Procedure Call version 2 protocol has been a Proposed The Remote Procedure Call version 2 protocol has been a Proposed
Standard for three decades (see [RFC5531] and its antecedents). Over Standard for three decades (see [RFC5531] and its antecedents). Over
twenty years ago, Eisler et al. first introduced RPCSEC GSS as an in- twenty years ago, Eisler et al. first introduced RPCSEC GSS as an in-
transit encryption mechanism for RPC [RFC2203]. However, experience transit encryption mechanism for RPC [RFC2203]. However, experience
has shown that RPCSEC GSS with in-transit encryption can be has shown that RPCSEC GSS with in-transit encryption can be
challenging to use in practice: challenging to use in practice:
o Parts of each RPC header remain in clear-text, constituting a o Parts of each RPC header remain in clear-text, constituting a
significant security exposure. significant security exposure.
o Offloading GSS privacy is not practical in large multi-user o Offloading the GSS privacy service is not practical in large
deployments since each message is encrypted using a key based on multi-user deployments since each message is encrypted using a key
the issuing RPC user. based on the issuing RPC user.
However strong a privacy service is, it cannot provide any security However strong GSS-provided confidentiality is, it cannot provide any
if the challenges of using it result in choosing not to deploy it at security if the challenges of using it result in choosing not to
all. deploy it at all.
Moreover, the use of AUTH_SYS remains common despite the adverse Moreover, the use of AUTH_SYS remains common despite the adverse
effects that acceptance of UIDs and GIDs from unauthenticated clients effects that acceptance of UIDs and GIDs from unauthenticated clients
brings with it. Continued use is in part because: brings with it. Continued use is in part because:
o Per-client deployment and administrative costs are not scalable. o Per-client deployment and administrative costs are not scalable.
Administrators must provide keying material for each RPC client, Administrators must provide keying material for each RPC client,
including transient clients. including transient clients.
o Host identity management and user identity management must be o Host identity management and user identity management must be
enforced in the same security realm. In certain environments, enforced in the same security realm. In certain environments,
different authorities might be responsible for provisioning client different authorities might be responsible for provisioning client
systems versus provisioning new users. systems versus provisioning new users.
The alternative described in the current document is to employ a The alternative described in the current document is to employ a
transport layer security mechanism that can protect the privacy of transport layer security mechanism that can protect the
each RPC connection transparently to RPC and upper-layer protocols. confidentiality of each RPC connection transparently to RPC and
The Transport Layer Security protocol [RFC8446] (TLS) is a well- upper-layer protocols. The Transport Layer Security protocol
established Internet building block that protects many standard [RFC8446] (TLS) is a well-established Internet building block that
Internet protocols such as the Hypertext Transport Protocol (HTTP) protects many standard Internet protocols such as the Hypertext
[RFC2818]. Transport Protocol (HTTP) [RFC2818].
Encrypting at the RPC transport layer accords several significant Encrypting at the RPC transport layer accords several significant
benefits: benefits:
Encryption By Default: Transport encryption can be enabled without Encryption By Default: Transport encryption can be enabled without
additional administrative tasks such as identifying client systems additional administrative tasks such as identifying client systems
to a trust authority, generating additional keying material, or to a trust authority, generating additional keying material, or
provisioning a secure network tunnel. provisioning a secure network tunnel.
Encryption Offload: Hardware support for GSS privacy has not Encryption Offload: Hardware support for the GSS privacy service has
appeared in the marketplace. However, the use of a well- not appeared in the marketplace. However, the use of a well-
established transport encryption mechanism that is employed by established transport encryption mechanism that is employed by
other ubiquitous network protocols makes it more likely that other ubiquitous network protocols makes it more likely that
encryption offload for RPC is practicable. encryption offload for RPC is practicable.
Securing AUTH_SYS: Most critically, transport encryption can Securing AUTH_SYS: Most critically, transport encryption can
significantly reduce several security issues inherent in the significantly reduce several security issues inherent in the
current widespread use of AUTH_SYS (i.e., acceptance of UIDs and current widespread use of AUTH_SYS (i.e., acceptance of UIDs and
GIDs generated by an unauthenticated client). GIDs generated by an unauthenticated client).
Decoupled User and Host Identities: TLS can be used to authenticate Decoupled User and Host Identities: TLS can be used to authenticate
peer hosts while other security mechanisms can handle user peer hosts while other security mechanisms can handle user
authentication. authentication.
The current document specifies the implementation of RPC on an The current document specifies the implementation of RPC on an
encrypted transport in a fashion that is transparent to upper-layer encrypted transport in a manner that is transparent to upper-layer
protocols based on RPC. The imposition of encryption at the protocols based on RPC. The imposition of encryption at the
transport layer protects any upper-layer protocol that employs RPC, transport layer protects any upper-layer protocol that employs RPC,
without alteration of that protocol. without alteration of that protocol.
Further, the current document defines policies in line with [RFC7435] Further, Section 7 of the current document defines policies in line
which enable RPC-on-TLS to be deployed opportunistically in with [RFC7435] which enable RPC-on-TLS to be deployed
environments with RPC implementations that do not support TLS. opportunistically in environments that contain RPC implementations
Specifications for RPC-based upper-layer protocols are free to that do not support TLS. However, specifications for RPC-based
require stricter policies to guarantee that encryption or host upper-layer protocols should choose to require even stricter policies
authentication is in use on every connection. that guarantee encryption and host authentication is used for all RPC
transactions. Enforcing the use of RPC-on-TLS is of particular
importance for existing upper-layer protocols whose security
infrastructure is weak.
The protocol specification in the current document assumes that The protocol specification in the current document assumes that
support for RPC, TLS, PKI, GSS-API, and DNSSEC is already available support for RPC, TLS, PKI, GSS-API, and DNSSEC is already available
in an RPC implementation where TLS support is to be added. in an RPC implementation where TLS support is to be added.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Terminology 3. Terminology
This document adopts the terminology introduced in Section 3 of This document adopts the terminology introduced in Section 3 of
[RFC6973] and assumes a working knowledge of the Remote Procedure [RFC6973] and assumes a working knowledge of the Remote Procedure
Call (RPC) version 2 protocol [RFC5531] and the Transport Layer Call (RPC) version 2 protocol [RFC5531] and the Transport Layer
Security (TLS) version 1.3 protocol [RFC8446]. Security (TLS) version 1.3 protocol [RFC8446].
Note also that the NFS community uses the term "privacy" where other Note also that the NFS community long ago adopted the use of the term
Internet communities use "confidentiality". In the current document "privacy" from documents such as [RFC2203]. In the current document,
the two terms are synonymous. the authors use the term "privacy" only when referring specifically
to the historic GSS privacy service defined in [RFC2203]. Otherwise,
the authors use the term "confidentiality", following the practices
of contemporary security communities.
We adhere to the convention that a "client" is a network host that We adhere to the convention that a "client" is a network host that
actively initiates an association, and a "server" is a network host actively initiates an association, and a "server" is a network host
that passively accepts an association request. that passively accepts an association request.
RPC documentation historically refers to the authentication of a RPC documentation historically refers to the authentication of a
connecting host as "machine authentication" or "host authentication". connecting host as "machine authentication" or "host authentication".
TLS documentation refers to the same as "peer authentication". In TLS documentation refers to the same as "peer authentication". In
the current document there is little distinction between these terms. the current document there is little distinction between these terms.
The term "user authentication" in this document refers specifically The term "user authentication" in the current document refers
to the RPC caller's credential, provided in the "cred" and "verf" specifically to the RPC caller's credential, provided in the "cred"
fields in each RPC Call. and "verf" fields in each RPC Call.
4. RPC-Over-TLS in Operation 4. RPC-Over-TLS in Operation
4.1. Discovering Server-side TLS Support 4.1. Discovering Server-side TLS Support
The mechanism described in this document interoperates fully with RPC The mechanism described in the current document interoperates fully
implementations that do not support TLS. The use of TLS is with RPC implementations that do not support TLS. Policy settings on
automatically disabled in these cases. the RPC-on-TLS-enabled peer determine whether RPC operation continues
without the use of TLS or RPC operation is not permitted.
To achieve this, we introduce a new RPC authentication flavor called To achieve this, we introduce a new RPC authentication flavor called
AUTH_TLS. This new flavor signals that the client wants to initiate AUTH_TLS. This new flavor signals that the client wants to initiate
TLS negotiation if the server supports it. Except for the TLS negotiation if the server supports it. Except for the
modifications described in this section, the RPC protocol is unaware modifications described in this section, the RPC protocol is unaware
of security encapsulation. of security encapsulation at the transport layer.
<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> When an RPC client is ready to begin a TLS session, it sends a NULL
RPC procedure with an auth_flavor of AUTH_TLS. The value of AUTH_TLS
is defined in Section 8.1. The NULL request is made to the same port
as if TLS were not in use.
The length of the opaque data constituting the credential sent in the The length of the opaque data constituting the credential sent in the
call message MUST be zero. The verifier accompanying the credential RPC Call message MUST be zero. The verifier accompanying the
MUST be an AUTH_NONE verifier of length zero. credential MUST be an AUTH_NONE verifier of length zero.
The flavor value of the verifier received in the reply message from The flavor value of the verifier in the RPC Reply message received
the server MUST be AUTH_NONE. The length of the verifier's body from the server MUST be AUTH_NONE. The length of the verifier's body
field is eight. The bytes of the verifier's body field encode the field is eight. The bytes of the verifier's body field encode the
ASCII characters "STARTTLS" as a fixed-length opaque. ASCII characters "STARTTLS" as a fixed-length opaque.
When an RPC client is ready to begin sending encrypted traffic to a If the RPC server replies with a reply_stat of MSG_ACCEPTED and an
server, it starts with a NULL RPC request with an auth_flavor of AUTH_NONE verifier containing the "STARTTLS" token, the RPC client
AUTH_TLS. The NULL request is made to the same port as if TLS were follows with a "ClientHello" message. The client MAY proceed with
not in use. TLS session establishment even if the Reply's accept_stat is not
SUCCESS (for example, if the accept_stat is PROG_UNAVAIL). Once the
The RPC server can respond in one of three ways: TLS handshake is complete, the RPC client and server have established
a secure channel for communicating.
o If the RPC server does not recognize the AUTH_TLS authentication
flavor, it responds with a reject_stat of AUTH_ERROR. The RPC
client then knows that this server does not support TLS.
o If the RPC server accepts the NULL RPC procedure but fails to
return an AUTH_NONE verifier containing the "STARTTLS" token in
the NULL Reply, the RPC client knows that this server does not
support TLS.
o If the RPC server accepts the NULL RPC procedure and returns an
AUTH_NONE verifier containing the "STARTTLS" token in the NULL
Reply, the RPC client immediately initiates a TLS session. This
NULL Reply signals that the RPC server is prepared for the client
to begin TLS session negotiation.
Once the TLS handshake is complete, the RPC client and server have If the Reply's reply_stat is MSG_ACCEPTED but the verifier does not
established a secure channel for communicating. The client MUST contain the "STARTTLS" token, or if the Reply's reply_stat is
switch to a security flavor other than AUTH_TLS within that channel, MSG_DENIED, the RPC client MUST NOT send a "ClientHello" message.
presumably after negotiating down redundant RPCSEC_GSS privacy and RPC operation can continue, however it will be without any
integrity services and applying channel binding [RFC7861]. confidentiality, integrity or authentication protection from (D)TLS.
If TLS negotiation fails for any reason, the RPC client reports this If, after a successful RPC AUTH_TLS probe, the subsequent TLS
failure to the upper-layer application the same way it would report handshake should fail for any reason, the RPC client reports this
an AUTH_ERROR rejection from the RPC server. failure to the upper-layer application the same way it reports an
AUTH_ERROR rejection from the RPC server.
If an RPC client attempts to use AUTH_TLS for anything other than the If an RPC client uses the AUTH_TLS authentication flavor on any
NULL RPC procedure, the RPC server MUST respond with a reject_stat of procedure other than the NULL procedure, or an RPC client sends an
AUTH_ERROR. RPC AUTH_TLS probe within an existing TLS session, the RPC server
MUST reject that RPC Call by setting the reply_stat field to
MSG_DENIED, the reject_stat field to AUTH_ERROR, and the auth_stat
field to AUTH_BADCRED.
4.2. Authentication 4.2. Authentication
Both RPC and TLS have peer and user authentication, with some overlap Both RPC and TLS have peer and user authentication, with some overlap
in capability between RPC and TLS. The goal of interoperability with in capability between RPC and TLS. The goal of interoperability with
implementations that do not support TLS requires limiting the implementations that do not support TLS requires limiting the
combinations that are allowed and precisely specifying the role that combinations that are allowed and precisely specifying the role that
each layer plays. We also want to handle TLS such that an RPC each layer plays. We also want to handle TLS such that an RPC
implementation can make the use of TLS invisible to existing RPC implementation can make the use of TLS invisible to existing RPC
consumer applications. consumer applications.
skipping to change at page 7, line 43 skipping to change at page 7, line 33
of client deployment: of client deployment:
Server-only Host Authentication Server-only Host Authentication
In this type of deployment, the client can authenticate the server In this type of deployment, the client can authenticate the server
host using the presented server peer TLS identity, but the server host using the presented server peer TLS identity, but the server
cannot authenticate the client. In this situation, RPC-over-TLS cannot authenticate the client. In this situation, RPC-over-TLS
clients are anonymous. They present no globally unique identifier clients are anonymous. They present no globally unique identifier
to the server peer. to the server peer.
Mutual Host Authentication Mutual Host Authentication
In this type of deployment, the client possesses a unique global In this type of deployment, the client possesses an identity (e.g.
identity (e.g., a certificate). As part of the TLS handshake, a certificate) that is backed by a trusted entity. As part of the
both peers authenticate using the presented TLS identities. If TLS handshake, both peers authenticate using the presented TLS
authentication of either peer fails, or if authorization based on identities. If authentication of either peer fails, or if
those identities blocks access to the server, the peers MUST authorization based on those identities blocks access to the
reject the association. server, the peers MUST reject the association.
In either of these modes, RPC user authentication is not affected by In either of these modes, RPC user authentication is not affected by
the use of transport layer security. When a client presents a TLS the use of transport layer security. When a client presents a TLS
peer identity to an RPC server, the protocol extension described in peer identity to an RPC server, the protocol extension described in
the current document provides no way for the server to know whether the current document provides no way for the server to know whether
that identity represents one RPC user on that client, or is shared that identity represents one RPC user on that client, or is shared
amongst many RPC users. Therefore, a server implementation must not amongst many RPC users. Therefore, a server implementation must not
utilize the remote TLS peer identity for RPC user authentication. utilize the remote TLS peer identity for RPC user authentication.
4.2.1. Using TLS with RPCSEC GSS 4.2.1. Using TLS with RPCSEC GSS
RPCSEC GSS can provide per-request integrity or privacy (also known To use GSS, an RPC server has to possess a GSS service principal. On
as confidentiality) services. When operating over a TLS session, the a TLS session, GSS mutual (peer) authentication occurs as usual, but
GSS services become redundant. A TLS-capable RPC implementation uses only after a TLS session has been established for communication.
GSS channel binding to determine when GSS integrity or privacy is Authentication of GSS users is unchanged by the use of TLS.
unnecessary. See Section 2.5 of [RFC7861] for details.
When using GSS on a TLS session, the RPC server is still required to RPCSEC GSS can also perform per-request integrity or confidentiality
possess a GSS service principal. GSS mutual authentication still protection. When operating over a TLS session, these GSS services
occurs after a TLS session has been established. become redundant. An RPC implementation capable of concurrently
using TLS and RPCSEC GSS can use GSS channel binding, as defined in
[RFC5056], to determine when an underlying transport provides a
sufficient degree of confidentiality. Channel bindings for the TLS
channel type are defined in [RFC5929].
5. TLS Requirements 5. TLS Requirements
When peers negotiate a TLS session that is to transport RPC, the When peers negotiate a TLS session that is to transport RPC, the
following restrictions apply: following restrictions apply:
o Implementations MUST NOT negotiate TLS versions prior to v1.3 o Implementations MUST NOT negotiate TLS versions prior to v1.3 (for
[RFC8446]. Support for mandatory-to-implement ciphersuites for TLS [RFC8446] or DTLS [I-D.ietf-tls-dtls13] respectively).
the negotiated TLS version is REQUIRED. Support for mandatory-to-implement ciphersuites for the negotiated
TLS version is REQUIRED.
o Implementations MUST support certificate-based mutual o Implementations MUST support certificate-based mutual
authentication. Support for TLS-PSK mutual authentication authentication. Support for TLS-PSK mutual authentication
[RFC4279] is OPTIONAL. See Section 4.2 for further details. [RFC4279] is OPTIONAL. See Section 4.2 for further details.
o Negotiation of a ciphersuite providing confidentiality as well as o Negotiation of a ciphersuite providing confidentiality as well as
integrity protection is REQUIRED. Support for and negotiation of integrity protection is REQUIRED. Support for and negotiation of
compression is OPTIONAL. compression is OPTIONAL.
Client implementations MUST include the
"application_layer_protocol_negotiation(16)" extension [RFC7301] in
their "ClientHello" message and MUST include the protocol identifier
defined in Section 8.2 in that message's ProtocolNameList value.
Similary, in response to the "ClientHello" message, server
implementations MUST include the
"application_layer_protocol_negotiation(16)" extension [RFC7301] in
their "ServerHello" message and MUST include only the protocol
identifier defined in Section 8.2 in that message's ProtocolNameList
value.
If the server responds incorrectly, the client MUST NOT establish a
TLS session for use with RPC on this connection. See [RFC7301] for
further details about how to form these messages properly.
5.1. Base Transport Considerations 5.1. Base Transport Considerations
5.1.1. Operation on TCP There is traditionally a strong association between an RPC program
and a destination port number. The use of TLS or DTLS does not
change that association. Thus it is frequently -- though not always
-- the case that a single TLS session carries traffic for only one
RPC program.
The use of TLS [RFC8446] protects RPC on TCP connections. Typically, 5.1.1. Protected Operation on TCP
once a client completes the TCP handshake and performs RPC service
discovery via NULL RPC operations, it uses the mechanism described in
Section 4.1 to discover TLS support. It can then negotiate a TLS
session on that connection.
After establishing a TLS session, an RPC server MUST reject with a The use of the Transport Layer Security (TLS) protocol [RFC8446]
reject_stat of AUTH_ERROR any subsequent RPC requests over a TLS- protects RPC on TCP connections. Typically, once an RPC client
protected connection that are outside of a TLS session. Likewise, an completes the TCP handshake, it uses the mechanism described in
RPC client MUST silently discard any subsequent RPC replies over the Section 4.1 to discover RPC-on-TLS support for that connection. If
connection that are outside of a TLS session. spurious traffic appears on a TCP connection between the initial
clear-text AUTH_TLS probe and the TLS session handshake, receivers
MUST discard that data without response and then SHOULD drop the
connection.
This restriction includes reverse-direction RPC operations (i.e., RPC The protocol convention specified in the current document assumes
calls initiated on the server-end of the connection). An RPC client there can be no more than one concurrent TLS session per TCP
receiving a reverse-direction call on a connection outside of an connection. This is true of current generations of TLS, but might be
existing TLS session MUST reject the request with a reject_stat of different in a future version of TLS.
AUTH_ERROR.
An RPC peer terminates a TLS session by sending a TLS closure alert, Once a TLS session is established on a TCP connection, no further
or by closing the TLS-protected TCP connection. clear-text communication can occur on that connection until the
session is terminated. The use of TLS does not alter RPC record
framing used on TCP transports.
5.1.2. Operation on UDP Furthermore, if an RPC server responds with PROG_UNAVAIL to an RPC
Call within an established TLS session, that does not imply that RPC
server will subsequently reject the same RPC program on a different
TCP connection.
RPC over UDP is protected using DTLS [RFC6347]. As soon as a client Backchannel operation occurs only on connected transports such as
initializes a socket for use with an unfamiliar server, it uses the TCP. To protect backchannel operations, an RPC server uses the
mechanism described in Section 4.1 to discover DTLS support and then existing TLS session on that connection to send backchannel
negotiate a DTLS session. Connected operation is RECOMMENDED. operations. The server does not attempt to establish a TLS session
on a TCP connection for backchannel operation.
Using a DTLS transport does not introduce reliable or in-order When operation is complete, an RPC peer terminates a TLS session by
semantics to RPC on UDP. Also, DTLS does not support fragmentation sending a TLS Closure Alert and may then close the TCP connection.
of RPC messages. Each RPC message MUST fit in a single DTLS
datagram. DTLS encapsulation has overhead, which reduces the
effective Path MTU (PMTU) and thus the maximum RPC payload size.
DTLS does not detect STARTTLS replay. Sending a TLS closure alert 5.1.2. Protected Operation on UDP
terminates a DTLS session. Subsequent RPC messages passing between
the client and server are no longer protected until a new TLS session
is established.
5.1.3. Operation on Other Transports RFC Editor: In the following section, please replace TBD with the
connection_id extension number that is to be assigned in
RPC-over-RDMA can make use of Transport Layer Security below the RDMA [I-D.ietf-tls-dtls-connection-id]. And, please remove this Editor's
transport layer [RFC8166]. The exact mechanism is not within the Note before this document is published.
scope of this document. Because there might not be other provisions
to exchange client and server certificates, authentication material RPC over UDP is protected using the Datagram Transport Layer Security
exchange would need to be provided by facilities within a future RPC- (DTLS) protocol [I-D.ietf-tls-dtls13].
over-RDMA transport.
Using DTLS does not introduce reliable or in-order semantics to RPC
on UDP. Each RPC message MUST fit in a single DTLS record. DTLS
encapsulation has overhead, which reduces the effective Path MTU
(PMTU) and thus the maximum RPC payload size. The use of DTLS record
replay protection is REQUIRED when transporting RPC traffic.
As soon as a client initializes a UDP socket for use with an RPC
server, it uses the mechanism described in Section 4.1 to discover
DTLS support for an RPC program on a particular port. It then
negotiates a DTLS session.
Multi-homed RPC clients and servers may send protected RPC messages
via network interfaces that were not involved in the handshake that
established the DTLS session. Therefore, when protecting RPC
traffic, each DTLS handshake MUST include the "connection_id(TBD)"
extension described in Section 9 of [I-D.ietf-tls-dtls13], and RPC-
on-DTLS peer endpoints MUST provide a ConnectionID with a non-zero
length. Endpoints implementing RPC programs that expect a
significant number of concurrent clients should employ ConnectionIDs
of at least 4 bytes in length.
Sending a TLS Closure Alert terminates a DTLS session. Subsequent
RPC messages exchanged between the RPC client and server are no
longer protected until a new DTLS session is established.
5.1.3. Protected Operation on Other Transports
Transports that provide intrinsic TLS-level security (e.g., QUIC) Transports that provide intrinsic TLS-level security (e.g., QUIC)
would need to be addressed separately from the current document. In need to be addressed separately from the current document. In such
such cases, the use of TLS would not be opportunistic as it is for cases, the use of TLS is not opportunistic as it can be for TCP or
TCP or UDP. UDP.
RPC-over-RDMA can make use of transport layer security below the RDMA
transport layer [RFC8166]. The exact mechanism is not within the
scope of the current document. Because there might not be other
provisions to exchange client and server certificates, authentication
material exchange needs to be provided by facilities within a future
version of the RPC-over-RDMA transport protocol.
5.2. TLS Peer Authentication 5.2. TLS Peer Authentication
TLS can perform peer authentication using any of the following TLS can perform peer authentication using any of the following
mechanisms: mechanisms:
5.2.1. X.509 Certificates Using PKIX trust 5.2.1. X.509 Certificates Using PKIX trust
Implementations are REQUIRED to support this mechanism. In this Implementations are REQUIRED to support this mechanism. In this
mode, the tuple (serial number of the presented certificate; Issuer) mode, the tuple (serial number of the presented certificate; Issuer)
skipping to change at page 10, line 32 skipping to change at page 11, line 32
o Implementations SHOULD indicate their trusted Certification o Implementations SHOULD indicate their trusted Certification
Authorities (CAs). Authorities (CAs).
o Peer validation always includes a check on whether the locally o Peer validation always includes a check on whether the locally
configured expected DNS name or IP address of the server that is configured expected DNS name or IP address of the server that is
contacted matches its presented certificate. DNS names and IP contacted matches its presented certificate. DNS names and IP
addresses can be contained in the Common Name (CN) or addresses can be contained in the Common Name (CN) or
subjectAltName entries. For verification, only one of these subjectAltName entries. For verification, only one of these
entries is to be considered. The following precedence applies: entries is to be considered. The following precedence applies:
for DNS name validation, subjectAltName:DNS has precedence over for DNS name validation, subjectAltName:DNS has precedence over
CN; for IP address validation, subjectAltName:iPAddr has CN; for IP address validation, subjectAltName:iPAddress has
precedence over CN. Implementors of this specification are precedence over CN. Implementors of this specification are
advised to read Section 6 of [RFC6125] for more details on DNS advised to read Section 6 of [RFC6125] for more details on DNS
name validation. name validation.
o For services accessed by their network identifiers (netids) and
universal network addresses (uaddr), the iPAddress subjectAltName
SHOULD be present in the certificate and must exactly match the
address represented by universal address.
o Implementations MAY allow the configuration of a set of additional o Implementations MAY allow the configuration of a set of additional
properties of the certificate to check for a peer's authorization properties of the certificate to check for a peer's authorization
to communicate (e.g., a set of allowed values in to communicate (e.g., a set of allowed values in
subjectAltName:URI or a set of allowed X509v3 Certificate subjectAltName:URI or a set of allowed X509v3 Certificate
Policies). Policies).
o When the configured trust base changes (e.g., removal of a CA from o When the configured trust base changes (e.g., removal of a CA from
the list of trusted CAs; issuance of a new CRL for a given CA), the list of trusted CAs; issuance of a new CRL for a given CA),
implementations MAY renegotiate the TLS session to reassess the implementations MAY renegotiate the TLS session to reassess the
connecting peer's continued authorization. connecting peer's continued authorization.
skipping to change at page 12, line 11 skipping to change at page 13, line 16
This mechanism is OPTIONAL to implement. In this mode, a token This mechanism is OPTIONAL to implement. In this mode, a token
uniquely identifies the RPC peer. uniquely identifies the RPC peer.
Versions of TLS after TLS 1.2 contain a token binding mechanism that Versions of TLS after TLS 1.2 contain a token binding mechanism that
is more secure than using certificates. This mechanism is detailed is more secure than using certificates. This mechanism is detailed
in [RFC8471]. in [RFC8471].
6. Implementation Status 6. Implementation Status
RFC Editor: Please remove this section and the reference to RFC 7942
before this document is published.
This section records the status of known implementations of the This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942]. Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to assist the IETF in its decision processes in progressing drafts to
RFCs. RFCs.
Please note that the listing of any individual implementation here Please note that the listing of any individual implementation here
does not imply endorsement by the IETF. Furthermore, no effort has does not imply endorsement by the IETF. Furthermore, no effort has
been spent to verify the information presented here that was supplied been spent to verify the information presented here that was supplied
by IETF contributors. This is not intended as, and must not be by IETF contributors. This is not intended as, and must not be
construed to be, a catalog of available implementations or their construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may features. Readers are advised to note that other implementations may
exist. exist.
6.1. DESY NFS server 6.1. DESY NFS server
Organization: DESY Organization: DESY
URL: https://desy.de URL: https://desy.de [2]
Maturity: Implementation will be based on mature versions of the Maturity: Implementation will be based on mature versions of the
current document. current document.
Coverage: The implementation is under way. The use of DTLS Coverage: The bulk of this specification is implemented including
functionality is not implemented. DTLS.
Licensing: LGPL Licensing: LGPL
Implementation experience: The implementer has read and commented on Implementation experience: The implementer has read and commented on
the current document. the current document.
6.2. Hammerspace NFS server 6.2. Hammerspace NFS server
Organization: Hammerspace Organization: Hammerspace
URL: https://hammerspace.com URL: https://hammerspace.com [3]
Maturity: Prototype software based on early versions of this Maturity: Prototype software based on early versions of the current
document. document.
Coverage: The bulk of this specification is implemented. The use of Coverage: The bulk of this specification is implemented. The use of
DTLS functionality is not implemented. DTLS functionality is not implemented.
Licensing: Proprietary Licensing: Proprietary
Implementation experience: No comments from implementors. Implementation experience: No comments from implementors.
6.3. Linux NFS server and client 6.3. Linux NFS server and client
Organization: The Linux Foundation Organization: The Linux Foundation
URL: https://www.kernel.org URL: https://www.kernel.org [4]
Maturity: Prototype software based on early versions of this Maturity: Prototype software based on early versions of the current
document. document.
Coverage: The bulk of this specification has yet to be implemented. Coverage: The bulk of this specification has yet to be implemented.
The use of DTLS functionality is not planned. The use of DTLS functionality is not planned.
Licensing: GPLv2 Licensing: GPLv2
Implementation experience: No comments from the implementor. Implementation experience: No comments from the implementor.
6.4. FreeBSD NFS server and client 6.4. FreeBSD NFS server and client
Organization: The FreeBSD Project Organization: The FreeBSD Project
URL: https://www.freebsd.org URL: https://www.freebsd.org [5]
Maturity: Prototype software based on early versions of this Maturity: Prototype software based on early versions of the current
document. document.
Coverage: The bulk of this specification is implemented. The use of Coverage: The bulk of this specification is implemented. The use of
DTLS functionality is not planned. DTLS functionality is not planned.
Licensing: BSD Licensing: BSD
Implementation experience: Implementers have read and commented on Implementation experience: Implementers have read and commented on
this document. the current document.
7. Security Considerations 7. Security Considerations
One purpose of the mechanism described in the current document is to One purpose of the mechanism described in the current document is to
protect RPC-based applications against threats to the privacy of RPC protect RPC-based applications against threats to the confidentiality
transactions and RPC user identities. A taxonomy of these threats of RPC transactions and RPC user identities. A taxonomy of these
appears in Section 5 of [RFC6973]. Also, Section 6 of [RFC7525] threats appears in Section 5 of [RFC6973]. Also, Section 6 of
contains a detailed discussion of technologies used in conjunction [RFC7525] contains a detailed discussion of technologies used in
with TLS. Implementers should familiarize themselves with these conjunction with TLS. Implementers should familiarize themselves
materials. with these materials.
7.1. Limitations of an Opportunistic Approach 7.1. Limitations of an Opportunistic Approach
The purpose of using an explicitly opportunistic approach is to The purpose of using an explicitly opportunistic approach is to
enable interoperation with implementations that do not support RPC- enable interoperation with implementations that do not support RPC-
over-TLS. A range of options is allowed by this approach, from "no over-TLS. A range of options is allowed by this approach, from "no
peer authentication or encryption" to "server-only authentication peer authentication or encryption" to "server-only authentication
with encryption" to "mutual authentication with encryption". The with encryption" to "mutual authentication with encryption". The
actual security level may indeed be selected based on policy and actual security level may indeed be selected based on policy and
without user intervention. without user intervention.
In cases where interoperability is a priority, the security benefits In environments where interoperability is a priority, the security
of TLS are partially or entirely waived. Implementations of the benefits of TLS are partially or entirely waived. Implementations of
mechanism described in the current document must take care to the mechanism described in the current document must take care to
accurately represent to all RPC consumers the level of security that accurately represent to all RPC consumers the level of security that
is actually in effect. Implementations are REQUIRED to provide an is actually in effect, and are REQUIRED to provide an audit log of
audit log of RPC-over-TLS security mode selection. RPC-over-TLS security mode selection.
In all other cases, the adoption, implementation, and deployment of
RPC-based upper-layer protocols that enforce the use of TLS
authentication and encryption (when similar RPCSEC GSS services are
not in use) is strongly encouraged.
7.1.1. STRIPTLS Attacks 7.1.1. STRIPTLS Attacks
A classic form of attack on network protocols that initiate an A classic form of attack on network protocols that initiate an
association in plain-text to discover support for TLS is a man-in- association in plain-text to discover support for TLS is a man-in-
the-middle that alters the plain-text handshake to make it appear as the-middle that alters the plain-text handshake to make it appear as
though TLS support is not available on one or both peers. Clients though TLS support is not available on one or both peers. Clients
implementers can choose from the following to mitigate STRIPTLS implementers can choose from the following to mitigate STRIPTLS
attacks: attacks:
skipping to change at page 14, line 44 skipping to change at page 16, line 8
work, and provide a binding of hostname to x.509 identity. If TLS work, and provide a binding of hostname to x.509 identity. If TLS
cannot be negotiated or authentication fails, the client cannot be negotiated or authentication fails, the client
disconnects and reports the problem. disconnects and reports the problem.
o Client security policy can require that a TLS session is o Client security policy can require that a TLS session is
established on every connection. If an attacker spoofs the established on every connection. If an attacker spoofs the
handshake, the client disconnects and reports the problem. If handshake, the client disconnects and reports the problem. If
TLSA records are not available, this approach is strongly TLSA records are not available, this approach is strongly
encouraged. encouraged.
7.1.2. Privacy Leakage Before Session Establishment
As mentioned earlier, communication between an RPC client and server
appears in the clear on the network prior to the establishment of a
TLS session. This clear-text information usually includes transport
connection handshake exchanges, the RPC NULL procedure probing
support for TLS, and the initial parts of TLS session establishment.
Appendix C of [RFC8446] discusses precautions that can mitigate
exposure during the exchange of connnection handshake information and
TLS certificate material that might enable attackers to track the RPC
client.
Any RPC traffic that appears on the network before a TLS session has
been established is vulnerable to monitoring or undetected
modification. A secure client implementation limits or prevents any
RPC exchanges that are not protected.
The exception to this edict is the initial RPC NULL procedure that
acts as a STARTTLS message, which cannot be protected. This RPC NULL
procedure contains no arguments or results, and the AUTH_TLS
authentication flavor it uses does not contain user information.
7.2. TLS Identity Management on Clients 7.2. TLS Identity Management on Clients
The goal of the RPC-on-TLS protocol extension is to hide the content The goal of the RPC-on-TLS protocol extension is to hide the content
of RPC requests while they are in transit. The RPC-on-TLS protocol of RPC requests while they are in transit. The RPC-on-TLS protocol
by itself cannot protect against exposure of a user's RPC requests to by itself cannot protect against exposure of a user's RPC requests to
other users on the same client. other users on the same client.
Moreover, client implementations are free to transmit RPC requests Moreover, client implementations are free to transmit RPC requests
for more than one RPC user using the same TLS session. Depending on for more than one RPC user using the same TLS session. Depending on
the details of the client RPC implementation, this means that the the details of the client RPC implementation, this means that the
skipping to change at page 15, line 22 skipping to change at page 17, line 10
As a result, client implementations need to carefully segregate TLS As a result, client implementations need to carefully segregate TLS
identity material so that local access to it is restricted to only identity material so that local access to it is restricted to only
the local users that are authorized to perform operations on the the local users that are authorized to perform operations on the
remote RPC server. remote RPC server.
7.3. Security Considerations for AUTH_SYS on TLS 7.3. Security Considerations for AUTH_SYS on TLS
Using a TLS-protected transport when the AUTH_SYS authentication Using a TLS-protected transport when the AUTH_SYS authentication
flavor is in use addresses several longstanding weaknesses (as flavor is in use addresses several longstanding weaknesses (as
detailed in Appendix A). TLS augments AUTH_SYS by providing both detailed in Appendix A). TLS augments AUTH_SYS by providing both
integrity protection and a privacy service that AUTH_SYS lacks. TLS integrity protection and confidentiality that AUTH_SYS lacks. TLS
protects data payloads, RPC headers, and user identities against protects data payloads, RPC headers, and user identities against
monitoring and alteration while in transit. TLS guards against the monitoring and alteration while in transit. TLS guards against the
insertion or deletion of messages, thus also ensuring the integrity insertion or deletion of messages, thus also ensuring the integrity
of the message stream between RPC client and server. Lastly, of the message stream between RPC client and server. Lastly,
transport layer encryption plus peer authentication protects transport layer encryption plus peer authentication protects
receiving XDR decoders from deserializing untrusted data, a common receiving XDR decoders from deserializing untrusted data, a common
coding vulnerability. coding vulnerability.
The use of TLS enables strong authentication of the communicating RPC The use of TLS enables strong authentication of the communicating RPC
peers, providing a degree of non-repudiation. When AUTH_SYS is used peers, providing a degree of non-repudiation. When AUTH_SYS is used
skipping to change at page 16, line 25 skipping to change at page 18, line 10
o When using RPCSEC_GSS, GSS/Kerberos provides adequate host o When using RPCSEC_GSS, GSS/Kerberos provides adequate host
authentication and a policy that requires GSS mutual authentication and a policy that requires GSS mutual
authentication and rejection of a connection when host authentication and rejection of a connection when host
authentication fails. GSS integrity and privacy services, authentication fails. GSS integrity and privacy services,
therefore, can be disabled in favor of TLS encryption with peer therefore, can be disabled in favor of TLS encryption with peer
authentication. authentication.
8. IANA Considerations 8. IANA Considerations
RFC Editor: In the following subsections, please replace RFC-TBD with
the RFC number assigned to this document. And, please remove this
Editor's Note before this document is published.
8.1. RPC Authentication Flavor
Following Appendix B of [RFC5531], the authors request a single new
entry in the RPC Authentication Flavor Numbers registry. The purpose
of the new authentication flavor is to signal the use of TLS with
RPC. This new flavor is not a pseudo-flavor.
The fields in the new entry are assigned as follows:
Identifier String: AUTH_TLS
Flavor Name: TLS
Value: 7
Description: Signals the use of TLS to protect RPC messages on
socket-based transports
Reference: RFC-TBD
8.2. ALPN Identifier for SUNRPC
Following Section 6 of [RFC7301], the authors request the allocation Following Section 6 of [RFC7301], the authors request the allocation
of the following value in the "Application-Layer Protocol Negotiation of the following value in the "Application-Layer Protocol Negotiation
(ALPN) Protocol IDs" registry. The "sunrpc" string identifies SunRPC (ALPN) Protocol IDs" registry. The "sunrpc" string identifies SunRPC
when used over TLS. when used over TLS.
Protocol: Protocol: SunRPC
SunRPC
Identification Sequence: Identification Sequence: 0x73 0x75 0x6e 0x72 0x70 0x63 ("sunrpc")
0x73 0x75 0x6e 0x72 0x70 0x63 ("sunrpc")
Reference: Reference: RFC-TBD
RFC-TBD
9. References 9. References
9.1. Normative References 9.1. Normative References
[FIPS.180-4] [FIPS.180-4]
National Institute of Standards and Technology, "Secure National Institute of Standards and Technology, "Secure
Hash Standard, Federal Information Processing Standards Hash Standard, Federal Information Processing Standards
Publication FIPS PUB 180-4", FIPS PUB 180-4, August 2015. Publication FIPS PUB 180-4", FIPS PUB 180-4, August 2015.
[I-D.ietf-tls-dtls-connection-id]
Rescorla, E., Tschofenig, H., and T. Fossati, "Connection
Identifiers for DTLS 1.2", draft-ietf-tls-dtls-connection-
id-07 (work in progress), October 2019.
[I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-37 (work in progress), March
2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key [RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005, RFC 4279, DOI 10.17487/RFC4279, December 2005,
<https://www.rfc-editor.org/info/rfc4279>. <https://www.rfc-editor.org/info/rfc4279>.
[RFC5056] Williams, N., "On the Use of Channel Bindings to Secure
Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007,
<https://www.rfc-editor.org/info/rfc5056>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
[RFC5531] Thurlow, R., "RPC: Remote Procedure Call Protocol [RFC5531] Thurlow, R., "RPC: Remote Procedure Call Protocol
Specification Version 2", RFC 5531, DOI 10.17487/RFC5531, Specification Version 2", RFC 5531, DOI 10.17487/RFC5531,
May 2009, <https://www.rfc-editor.org/info/rfc5531>. May 2009, <https://www.rfc-editor.org/info/rfc5531>.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<https://www.rfc-editor.org/info/rfc5929>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509 within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer (PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>. 2011, <https://www.rfc-editor.org/info/rfc6125>.
[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>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>. 2014, <https://www.rfc-editor.org/info/rfc7258>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>. July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[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>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205, Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016, RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>. <https://www.rfc-editor.org/info/rfc7942>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
skipping to change at page 19, line 7 skipping to change at page 21, line 33
1", RFC 8166, DOI 10.17487/RFC8166, June 2017, 1", RFC 8166, DOI 10.17487/RFC8166, June 2017,
<https://www.rfc-editor.org/info/rfc8166>. <https://www.rfc-editor.org/info/rfc8166>.
[RFC8471] Popov, A., Ed., Nystroem, M., Balfanz, D., and J. Hodges, [RFC8471] Popov, A., Ed., Nystroem, M., Balfanz, D., and J. Hodges,
"The Token Binding Protocol Version 1.0", RFC 8471, "The Token Binding Protocol Version 1.0", RFC 8471,
DOI 10.17487/RFC8471, October 2018, DOI 10.17487/RFC8471, October 2018,
<https://www.rfc-editor.org/info/rfc8471>. <https://www.rfc-editor.org/info/rfc8471>.
9.3. URIs 9.3. URIs
[1] https://www.linuxjournal.com/content/encrypting-nfsv4-stunnel-tls [1] https://github.com/chucklever/i-d-rpc-tls
[2] https://desy.de
[3] https://hammerspace.com
[4] https://www.kernel.org
[5] https://www.freebsd.org
[6] https://www.linuxjournal.com/content/encrypting-nfsv4-stunnel-tls
Appendix A. Known Weaknesses of the AUTH_SYS Authentication Flavor Appendix A. Known Weaknesses of the AUTH_SYS Authentication Flavor
The ONC RPC protocol, as specified in [RFC5531], provides several The ONC RPC protocol, as specified in [RFC5531], provides several
modes of security, traditionally referred to as "authentication modes of security, traditionally referred to as "authentication
flavors". Some of these flavors provide much more than an flavors". Some of these flavors provide much more than an
authentication service. We refer to these as authentication flavors, authentication service. We refer to these as authentication flavors,
security flavors, or simply, flavors. One of the earliest and most security flavors, or simply, flavors. One of the earliest and most
basic flavors is AUTH_SYS, also known as AUTH_UNIX. Appendix A of basic flavors is AUTH_SYS, also known as AUTH_UNIX. Appendix A of
[RFC5531] specifies AUTH_SYS. [RFC5531] specifies AUTH_SYS.
skipping to change at page 19, line 49 skipping to change at page 22, line 37
It should be noted that use of this flavor of authentication does It should be noted that use of this flavor of authentication does
not guarantee any security for the users or providers of a not guarantee any security for the users or providers of a
service, in itself. The authentication provided by this scheme service, in itself. The authentication provided by this scheme
can be considered legitimate only when applications using this can be considered legitimate only when applications using this
scheme and the network can be secured externally, and privileged scheme and the network can be secured externally, and privileged
transport addresses are used for the communicating end-points (an transport addresses are used for the communicating end-points (an
example of this is the use of privileged TCP/UDP ports in UNIX example of this is the use of privileged TCP/UDP ports in UNIX
systems -- note that not all systems enforce privileged transport systems -- note that not all systems enforce privileged transport
address mechanisms). address mechanisms).
It should be clear, therefore, that AUTH_SYS by itself offers little It should be clear, therefore, that AUTH_SYS by itself (i.e., without
to no communication security: strong client authentication) offers little to no communication
security:
1. It does not protect the privacy or integrity of RPC requests, 1. It does not protect the confidentiality or integrity of RPC
users, or payloads, relying instead on "external" security. requests, users, or payloads, relying instead on "external"
security.
2. It does not provide authentication of RPC peer machines, other 2. It does not provide authentication of RPC peer machines, other
than inclusion of an unprotected domain name. than inclusion of an unprotected domain name.
3. The use of 32-bit unsigned integers as user and group identifiers 3. The use of 32-bit unsigned integers as user and group identifiers
is problematic because these data types are not cryptographically is problematic because these data types are not cryptographically
signed or otherwise verified by any authority. signed or otherwise verified by any authority.
4. Because the user and group ID fields are not integrity-protected, 4. Because the user and group ID fields are not integrity-protected,
AUTH_SYS does not provide non-repudiation. AUTH_SYS does not provide non-repudiation.
Acknowledgments Acknowledgments
Special mention goes to Charles Fisher, author of "Encrypting NFSv4 Special mention goes to Charles Fisher, author of "Encrypting NFSv4
with Stunnel TLS" [1]. His article inspired the mechanism described with Stunnel TLS" [6]. His article inspired the mechanism described
in this document. in the current document.
Many thanks to Tigran Mkrtchyan for his work on the DESY prototype Many thanks to Tigran Mkrtchyan and Rick Macklem for their work on
and his feedback on the current document. prototype implementations and feedback on the current document.
Thanks to Derrell Piper for numerous suggestions that improved both Thanks to Derrell Piper for numerous suggestions that improved both
this simple mechanism and the current document's security-related this simple mechanism and the current document's security-related
discussion. discussion.
The authors are grateful to Bill Baker, David Black, Alan DeKok, Lars Many thanks to Transport Area Director Magnus Westerlund for his
Eggert, Benjamin Kaduk, Olga Kornievskaia, Greg Marsden, Alex sharp questions and careful reading of the final revisions of the
McDonald, Justin Mazzola Paluska, Tom Talpey, and Martin Thomson for current document. The text of Section 5.1.2 is mostly his
their input and support of this work. contribution.
Lastly, special thanks to document shepherd David Noveck, Transport The authors are additionally grateful to Bill Baker, David Black,
Area Director Magnus Westerlund, NFSV4 Working Group Chairs Spencer Alan DeKok, Lars Eggert, Benjamin Kaduk, Olga Kornievskaia, Greg
Shepler and Brian Pawlowski, and NFSV4 Working Group Secretary Thomas Marsden, Alex McDonald, Justin Mazzola Paluska, Tom Talpey, and
Haynes for their guidance and oversight. Martin Thomson for their input and support of this work.
Finally, special thanks to NFSV4 Working Group Chair and document
shepherd David Noveck, NFSV4 Working Group Chairs Spencer Shepler and
Brian Pawlowski, and NFSV4 Working Group Secretary Thomas Haynes for
their guidance and oversight.
Authors' Addresses Authors' Addresses
Trond Myklebust Trond Myklebust
Hammerspace Inc Hammerspace Inc
4300 El Camino Real Ste 105 4300 El Camino Real Ste 105
Los Altos, CA 94022 Los Altos, CA 94022
United States of America United States of America
Email: trond.myklebust@hammerspace.com Email: trond.myklebust@hammerspace.com
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