draft-ietf-httpauth-scram-auth-06.txt   draft-ietf-httpauth-scram-auth-07.txt 
HTTPAUTH A. Melnikov HTTPAUTH A. Melnikov
Internet-Draft Isode Ltd Internet-Draft Isode Ltd
Intended status: Standards Track June 18, 2015 Intended status: Standards Track July 26, 2015
Expires: December 20, 2015 Expires: January 27, 2016
Salted Challenge Response (SCRAM) HTTP Authentication Mechanism Salted Challenge Response (SCRAM) HTTP Authentication Mechanism
draft-ietf-httpauth-scram-auth-06.txt draft-ietf-httpauth-scram-auth-07.txt
Abstract Abstract
The secure authentication mechanism most widely deployed and used by The secure authentication mechanism most widely deployed and used by
Internet application protocols is the transmission of clear-text Internet application protocols is the transmission of clear-text
passwords over a channel protected by Transport Layer Security (TLS). passwords over a channel protected by Transport Layer Security (TLS).
There are some significant security concerns with that mechanism, There are some significant security concerns with that mechanism,
which could be addressed by the use of a challenge response which could be addressed by the use of a challenge response
authentication mechanism protected by TLS. Unfortunately, the HTTP authentication mechanism protected by TLS. Unfortunately, the HTTP
Digest challenge response mechanism presently on the standards track Digest challenge response mechanism presently on the standards track
skipping to change at page 1, line 45 skipping to change at page 1, line 45
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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 December 20, 2015. This Internet-Draft will expire on January 27, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Conventions Used in This Document . . . . . . . . . . . . . . 2 1. Conventions Used in This Document . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
3. SCRAM Algorithm Overview . . . . . . . . . . . . . . . . . . 6 3. SCRAM Algorithm Overview . . . . . . . . . . . . . . . . . . 6
4. SCRAM Mechanism Names . . . . . . . . . . . . . . . . . . . . 7 4. SCRAM Mechanism Names . . . . . . . . . . . . . . . . . . . . 7
5. SCRAM Authentication Exchange . . . . . . . . . . . . . . . . 7 5. SCRAM Authentication Exchange . . . . . . . . . . . . . . . . 7
5.1. One round trip reauthentication . . . . . . . . . . . . . . 10 5.1. One round trip reauthentication . . . . . . . . . . . . . . 10
6. Use of Authentication-Info header field with SCRAM . . . . . 11 6. Use of Authentication-Info header field with SCRAM . . . . . 11
7. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 11 7. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
11. Design Motivations . . . . . . . . . . . . . . . . . . . . . 14 11. Design Motivations . . . . . . . . . . . . . . . . . . . . . 14
12. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 15 12. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 15
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
13.1. Normative References . . . . . . . . . . . . . . . . . . . 15 13.1. Normative References . . . . . . . . . . . . . . . . . . . 15
13.2. Informative References . . . . . . . . . . . . . . . . . . 16 13.2. Informative References . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Conventions Used in This Document 1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Formal syntax is defined by [RFC5234] including the core rules Formal syntax is defined by [RFC5234] including the core rules
defined in Appendix B of [RFC5234]. defined in Appendix B of [RFC5234].
skipping to change at page 4, line 19 skipping to change at page 4, line 19
o ":=": The variable on the left hand side represents the octet o ":=": The variable on the left hand side represents the octet
string resulting from the expression on the right hand side. string resulting from the expression on the right hand side.
o "+": Octet string concatenation. o "+": Octet string concatenation.
o "[ ]": A portion of an expression enclosed in "[" and "]" may not o "[ ]": A portion of an expression enclosed in "[" and "]" may not
be included in the result under some circumstances. See the be included in the result under some circumstances. See the
associated text for a description of those circumstances. associated text for a description of those circumstances.
o Normalize(str): Apply the SASLPrep profile [RFC4013] of the o Normalize(str): Apply the Preparation and Enforcement steps
"stringprep" algorithm [RFC3454] as the normalization algorithm to according to the OpaqueString profile (see
a UTF-8 [RFC3629] encoded "str". The resulting string is also in [I-D.ietf-precis-saslprepbis]) to a UTF-8 [RFC3629] encoded "str".
UTF-8. When applying SASLPrep, "str" is treated as a "stored The resulting string is also in UTF-8. Note that implementations
strings", which means that unassigned Unicode codepoints are MUST either implement OpaqueString profile operations from
prohibited (see Section 7 of [RFC3454]). Note that [I-D.ietf-precis-saslprepbis], or disallow use of non US-ASCII
implementations MUST either implement SASLPrep, or disallow use of Unicode codepoints in "str". The latter is a particular case of
non US-ASCII Unicode codepoints in "str". compliance with [I-D.ietf-precis-saslprepbis].
o HMAC(key, str): Apply the HMAC keyed hash algorithm (defined in o HMAC(key, str): Apply the HMAC keyed hash algorithm (defined in
[RFC2104]) using the octet string represented by "key" as the key [RFC2104]) using the octet string represented by "key" as the key
and the octet string "str" as the input string. The size of the and the octet string "str" as the input string. The size of the
result is the hash result size for the hash function in use. For result is the hash result size for the hash function in use. For
example, it is 32 octets for SHA-256 and 20 octets for SHA-1 (see example, it is 32 octets for SHA-256 and 20 octets for SHA-1 (see
[RFC3174]). [RFC3174]).
o H(str): Apply the cryptographic hash function to the octet string o H(str): Apply the cryptographic hash function to the octet string
"str", producing an octet string as a result. The size of the "str", producing an octet string as a result. The size of the
skipping to change at page 7, line 47 skipping to change at page 7, line 47
scram-name = "SCRAM-SHA-256" / "SCRAM-SHA-1" / other-scram-name scram-name = "SCRAM-SHA-256" / "SCRAM-SHA-1" / other-scram-name
; SCRAM-SHA-256 and SCRAM-SHA-1 are registered by this RFC ; SCRAM-SHA-256 and SCRAM-SHA-1 are registered by this RFC
other-scram-name = "SCRAM-" hash-name other-scram-name = "SCRAM-" hash-name
; hash-name is a capitalized form of names from IANA ; hash-name is a capitalized form of names from IANA
; "Hash Function Textual Names" registry. ; "Hash Function Textual Names" registry.
; Additional SCRAM names must be registered in both ; Additional SCRAM names must be registered in both
; the IANA "SASL mechanisms" registry ; the IANA "SASL mechanisms" registry
; and the IANA "authentication scheme" registry. ; and the IANA "authentication scheme" registry.
[[CREF1: Replace with SHA-256?]] This is a simple example of a SCRAM- This is a simple example of a SCRAM-SHA-256 authentication exchange
SHA-1 authentication exchange (no support for channel bindings, as (no support for channel bindings, as this feature is not currently
this feature is not currently supported by HTTP). In the example supported by HTTP). Username 'user' and password 'pencil' are used.
base64 encoded data is denoted by 'base64(...)' convention. Username
'user' and password 'pencil' are used. Note that long lines are folded for readability.
C: GET /resource HTTP/1.1 C: GET /resource HTTP/1.1
C: Host: server.example.com C: Host: server.example.com
C: [...] C: [...]
S: HTTP/1.1 401 Unauthorized S: HTTP/1.1 401 Unauthorized
S: WWW-Authenticate: Digest realm="realm1@host.com", S: WWW-Authenticate: Digest realm="realm1@host.com",
Digest realm="realm2@host.com", Digest realm="realm2@host.com",
Digest realm="realm3@host.com", Digest realm="realm3@host.com",
SCRAM-SHA-1 realm="realm3@host.com", SCRAM-SHA-1 realm="realm3@host.com",
SCRAM-SHA-1 realm="testrealm@host.com" SCRAM-SHA-1 realm="testrealm@host.com"
S: [...] S: [...]
C: GET /resource HTTP/1.1 C: GET /resource HTTP/1.1
C: Host: server.example.com C: Host: server.example.com
C: Authorization: SCRAM-SHA-1 realm="testrealm@host.com", C: Authorization: SCRAM-SHA-1 realm="testrealm@host.com",
data=base64(n,,n=user,r=fyko+d2lbbFgONRv9qkxdawL) data=biwsbj11c2VyLHI9ck9wck5HZndFYmVSV2diTkVrcU8K
C: [...] C: [...]
S: HTTP/1.1 401 Unauthorized S: HTTP/1.1 401 Unauthorized
S: WWW-Authenticate: SCRAM-SHA-1 S: WWW-Authenticate: SCRAM-SHA-1
sid=AAAABBBBCCCCDDDD, sid=AAAABBBBCCCCDDDD,
data=base64(r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j, data=cj1yT3ByTkdmd0ViZVJXZ2JORWtxTyVodllEcFdVYTJSYVRDQWZ1eEZJbGo
s=QSXCR+Q6sek8bf92,i=4096) paE5sRixzPVcyMlphSjBTTlk3c29Fc1VFamI2Z1E9PSxpPTQwOTYK
S: [...] S: [...]
C: GET /resource HTTP/1.1 C: GET /resource HTTP/1.1
C: Host: server.example.com C: Host: server.example.com
C: Authorization: SCRAM-SHA-1 sid=AAAABBBBCCCCDDDD, C: Authorization: SCRAM-SHA-1 sid=AAAABBBBCCCCDDDD,
data=base64(c=biws,r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j, data=Yz1iaXdzLHI9ck9wck5HZndFYmVSV2diTkVrcU8laHZZRHBXVWEyUmFUQ0FmdXhG
p=v0X8v3Bz2T0CJGbJQyF0X+HI4Ts=) SWxqKWhObEYscD1kSHpiWmFwV0lrNGpVaE4rVXRlOXl0YWc5empmTUhnc3FtbWl6
N0FuZFZRPQo=
C: [...] C: [...]
S: HTTP/1.1 200 Ok S: HTTP/1.1 200 Ok
S: Authentication-Info: sid=AAAABBBBCCCCDDDD, S: Authentication-Info: sid=AAAABBBBCCCCDDDD,
data=base64(v=rmF9pqV8S7suAoZWja4dJRkFsKQ=) data=dj02cnJpVFJCaTIzV3BSUi93dHVwK21NaFVaVW4vZEI1bkxUSlJzamw5NUc0PQo=
S: [...Other header fields and resource body...] S: [...Other header fields and resource body...]
In the above example the first client request contains data attribute
which base64 decodes as follows: "n,,n=user,r=rOprNGfwEbeRWgbNEkqO"
(with no quotes). Server then responds with data attribute which
base64 decodes as follows: "r=rOprNGfwEbeRWgbNEkqO%hvYDpWUa2RaTCAfuxF
Ilj)hNlF$k0,s=W22ZaJ0SNY7soEsUEjb6gQ==,i=4096". The next client
request contains data attribute which base64 decodes as follows: "c=b
iws,r=rOprNGfwEbeRWgbNEkqO%hvYDpWUa2RaTCAfuxFIlj)hNlF$k0,p=dHzbZapWIk
4jUhN+Ute9ytag9zjfMHgsqmmiz7AndVQ=". An the final server response
contains data attribute which base64 decodes as follows:
"v=6rriTRBi23WpRR/wtup+mMhUZUn/dB5nLTJRsjl95G4=".
Note that in the example above the client can also initiate SCRAM Note that in the example above the client can also initiate SCRAM
authentication without first being prompted by the server. authentication without first being prompted by the server.
Initial "SCRAM-SHA-256" authentication starts with sending the Initial "SCRAM-SHA-256" authentication starts with sending the
"Authorization" request header field defined by HTTP/1.1, Part 7 "Authorization" request header field defined by HTTP/1.1, Part 7
[RFC7235] containing "SCRAM-SHA-256" authentication scheme and the [RFC7235] containing "SCRAM-SHA-256" authentication scheme and the
following attributes: following attributes:
o A "realm" attribute MAY be included to indicate the scope of o A "realm" attribute MAY be included to indicate the scope of
protection in the manner described in HTTP/1.1, Part 7 [RFC7235]. protection in the manner described in HTTP/1.1, Part 7 [RFC7235].
skipping to change at page 9, line 28 skipping to change at page 9, line 39
Note that the header always starts with "n", "y" or "p", Note that the header always starts with "n", "y" or "p",
otherwise the message is invalid and authentication MUST fail. otherwise the message is invalid and authentication MUST fail.
* SCRAM username and a random, unique nonce attributes. * SCRAM username and a random, unique nonce attributes.
In HTTP response, the server sends WWW-Authenticate header field In HTTP response, the server sends WWW-Authenticate header field
containing: a unique session identifier (the "sid" attribute) plus containing: a unique session identifier (the "sid" attribute) plus
the "data" attribute containing base64-encoded "server-first-message" the "data" attribute containing base64-encoded "server-first-message"
[RFC5802]. The "server-first-message" contains the user's iteration [RFC5802]. The "server-first-message" contains the user's iteration
count i, the user's salt, and the nonce with a concatenation of the count i, the user's salt, and the nonce with a concatenation of the
client-specified one with a server nonce. [[CREF2: OPEN ISSUE: client-specified one with a server nonce. [[CREF1: OPEN ISSUE:
Alternatively, the "sid" attribute can be another header field.]] Alternatively, the "sid" attribute can be another header field.]]
The client then responds with another HTTP request with the The client then responds with another HTTP request with the
Authorization header field, which includes the "sid" attribute Authorization header field, which includes the "sid" attribute
received in the previous server response, together with the "data" received in the previous server response, together with the "data"
attribute containing base64-encoded "client-final-message" data. The attribute containing base64-encoded "client-final-message" data. The
latter has the same nonce and a ClientProof computed using the latter has the same nonce and a ClientProof computed using the
selected hash function (e.g. SHA-256) as explained earlier. selected hash function (e.g. SHA-256) as explained earlier.
The server verifies the nonce and the proof, and, finally, it The server verifies the nonce and the proof, and, finally, it
skipping to change at page 10, line 17 skipping to change at page 10, line 25
If the server supports SCRAM reauthentication, the server sends in If the server supports SCRAM reauthentication, the server sends in
its initial HTTP response a WWW-Authenticate header field containing: its initial HTTP response a WWW-Authenticate header field containing:
the "realm" attribute (as defined earlier), the "sr" attribute that the "realm" attribute (as defined earlier), the "sr" attribute that
contains the server part of the "r" attribute (see [RFC5802] and contains the server part of the "r" attribute (see [RFC5802] and
optional "ttl" attribute (which contains the "sr" value validity in optional "ttl" attribute (which contains the "sr" value validity in
seconds). seconds).
If the client has authenticated to the same realm before (i.e. it If the client has authenticated to the same realm before (i.e. it
remembers "i" and "s" attributes for the user from earlies remembers "i" and "s" attributes for the user from earlies
authentication exchanges with the server), it can respond to that authentication exchanges with the server), it can respond to that
with "client-final-message". [[CREF3: Should some counter be added with "client-final-message". [[CREF2: Should some counter be added
to make "sr" unique for each reauth?]] to make "sr" unique for each reauth?]]
If the server considers the server part of the nonce (the "r" If the server considers the server part of the nonce (the "r"
attribute) to be still valid, it will provide access to the requested attribute) to be still valid, it will provide access to the requested
resource (assuming the client hash verifies correctly, of course). resource (assuming the client hash verifies correctly, of course).
However if the server considers that the server part of the nonce is However if the server considers that the server part of the nonce is
stale (for example if the "sr" value is used after the "ttl" stale (for example if the "sr" value is used after the "ttl"
seconds), the server returns "401 Unauthorized" containing the SCRAM seconds), the server returns "401 Unauthorized" containing the SCRAM
mechanism name with a new "sr" and optional "ttl" attributes. mechanism name with the following attributes: a new "sr",
[[CREF4: Do we also need the "stale" attribute, like the one used by "stale=true" and an optional "ttl". The "stale" attribute signals to
DIGEST?]] the client that there is no need to ask user for the password.
Formally, the "stale" attribute is defined as follows: A flag,
indicating that the previous request from the client was rejected
because the nonce value was stale. If stale is TRUE (case-
insensitive), the client may wish to simply retry the request with
a new encrypted response, without reprompting the user for a new
username and password. The server should only set stale to TRUE
if it receives a request for which the nonce is invalid but with a
valid digest for that nonce (indicating that the client knows the
correct username/password). If stale is FALSE, or anything other
than TRUE, or the stale directive is not present, the username
and/or password are invalid, and new values must be obtained.
When constructing AuthMessage Section 3 to be used for calculating When constructing AuthMessage Section 3 to be used for calculating
client and server proofs, "client-first-message-bare" and "server- client and server proofs, "client-first-message-bare" and "server-
first-message" are reconstructed from data known to the client and first-message" are reconstructed from data known to the client and
the server. the server.
Reauthentication can look like this: Reauthentication can look like this:
C: GET /resource HTTP/1.1 C: GET /resource HTTP/1.1
C: Host: server.example.com C: Host: server.example.com
C: [...] C: [...]
S: HTTP/1.1 401 Unauthorized S: HTTP/1.1 401 Unauthorized
S: WWW-Authenticate: Digest realm="realm1@host.com", S: WWW-Authenticate: Digest realm="realm1@host.com",
Digest realm="realm2@host.com", Digest realm="realm2@host.com",
Digest realm="realm3@host.com", Digest realm="realm3@host.com",
SCRAM-SHA-1 realm="realm3@host.com", SCRAM-SHA-1 realm="realm3@host.com",
SCRAM-SHA-1 realm="testrealm@host.com", sr=3rfcNHYJY1ZVvWVs7j SCRAM-SHA-1 realm="testrealm@host.com", sr=pWUa2RaTCAfuxFIlj)hNlF$k0
SCRAM-SHA-1 realm="testrealm2@host.com", sr=AAABBBCCCDDD, ttl=120 SCRAM-SHA-1 realm="testrealm2@host.com", sr=AAABBBCCCDDD, ttl=120
S: [...] S: [...]
[Client authenticates as usual to realm "testrealm@host.com"] [Client authenticates as usual to realm "testrealm@host.com"]
[Some time later client decides to reauthenticate. [Some time later client decides to reauthenticate.
It will use the cached "i" and "s" from earlies exchanges. It will use the cached "i" (4096) and "s" (W22ZaJ0SNY7soEsUEjb6gQ==) from earlies exchanges.
It will use the server advertised "sr" value as the server part of the "r".] It will use the server advertised "sr" value as the server part of the "r".]
C: GET /resource HTTP/1.1 C: GET /resource HTTP/1.1
C: Host: server.example.com C: Host: server.example.com
C: Authorization: SCRAM-SHA-1 realm="testrealm@host.com", C: Authorization: SCRAM-SHA-1 realm="testrealm@host.com",
data=base64(c=biws,r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j, data=Yz1iaXdzLHI9ck9wck5HZndFYmVSV2diTkVrcU8laHZZRHBXVWEyUmFUQ0FmdXhG
p=v0X8v3Bz2T0CJGbJQyF0X+HI4Ts=) SWxqKWhObEYscD1kSHpiWmFwV0lrNGpVaE4rVXRlOXl0YWc5empmTUhnc3FtbWl6
N0FuZFZRPQo=
C: [...] C: [...]
S: HTTP/1.1 200 Ok S: HTTP/1.1 200 Ok
S: Authentication-Info: sid=AAAABBBBCCCCDDDD, S: Authentication-Info: sid=AAAABBBBCCCCDDDD,
data=base64(v=rmF9pqV8S7suAoZWja4dJRkFsKQ=) data=dj02cnJpVFJCaTIzV3BSUi93dHVwK21NaFVaVW4vZEI1bkxUSlJzamw5NUc0PQo=
S: [...Other header fields and resource body...] S: [...Other header fields and resource body...]
6. Use of Authentication-Info header field with SCRAM 6. Use of Authentication-Info header field with SCRAM
When used with SCRAM, the Authentication-Info header field is allowed When used with SCRAM, the Authentication-Info header field is allowed
in the trailer of an HTTP message transferred via chunked transfer- in the trailer of an HTTP message transferred via chunked transfer-
coding. coding.
7. Formal Syntax 7. Formal Syntax
skipping to change at page 12, line 33 skipping to change at page 12, line 39
;; SCRAM challenge or response defined in ;; SCRAM challenge or response defined in
;; RFC 5802. ;; RFC 5802.
ttl = "ttl" = 1*DIGIT ttl = "ttl" = 1*DIGIT
;; "sr" value validity in seconds. ;; "sr" value validity in seconds.
;; No leading 0s. ;; No leading 0s.
sid = "sid=" token sid = "sid=" token
;; See token definition in RFC 7235. ;; See token definition in RFC 7235.
stale = "stale=" ( "true" / "false" )
realm = "realm=" <as defined in RFC 7235> realm = "realm=" <as defined in RFC 7235>
8. Security Considerations 8. Security Considerations
If the authentication exchange is performed without a strong security If the authentication exchange is performed without a strong security
layer (such as TLS with data confidentiality), then a passive layer (such as TLS with data confidentiality), then a passive
eavesdropper can gain sufficient information to mount an offline eavesdropper can gain sufficient information to mount an offline
dictionary or brute-force attack which can be used to recover the dictionary or brute-force attack which can be used to recover the
user's password. The amount of time necessary for this attack user's password. The amount of time necessary for this attack
depends on the cryptographic hash function selected, the strength of depends on the cryptographic hash function selected, the strength of
skipping to change at page 15, line 36 skipping to change at page 15, line 44
Hansen, T., "SCRAM-SHA-256 and SCRAM-SHA-256-PLUS SASL Hansen, T., "SCRAM-SHA-256 and SCRAM-SHA-256-PLUS SASL
Mechanisms", draft-hansen-scram-sha256-02 (work in Mechanisms", draft-hansen-scram-sha256-02 (work in
progress), October 2014. progress), October 2014.
[I-D.ietf-httpbis-auth-info] [I-D.ietf-httpbis-auth-info]
Reschke, J., "The Hypertext Transfer Protocol (HTTP) Reschke, J., "The Hypertext Transfer Protocol (HTTP)
Authentication-Info and Proxy- Authentication-Info Authentication-Info and Proxy- Authentication-Info
Response Header Fields", draft-ietf-httpbis-auth-info-03 Response Header Fields", draft-ietf-httpbis-auth-info-03
(work in progress), March 2015. (work in progress), March 2015.
[I-D.ietf-precis-saslprepbis]
Saint-Andre, P. and A. Melnikov, "Preparation,
Enforcement, and Comparison of Internationalized Strings
Representing Usernames and Passwords", draft-ietf-precis-
saslprepbis-18 (work in progress), May 2015.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February Hashing for Message Authentication", RFC 2104,
1997. DOI 10.17487/RFC2104, February 1997,
<http://www.rfc-editor.org/info/rfc2104>.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1 [RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1
(SHA1)", RFC 3174, September 2001. (SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001,
<http://www.rfc-editor.org/info/rfc3174>.
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454, Internationalized Strings ("stringprep")", RFC 3454,
December 2002. DOI 10.17487/RFC3454, December 2002,
<http://www.rfc-editor.org/info/rfc3454>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names [RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names
and Passwords", RFC 4013, February 2005. and Passwords", RFC 4013, DOI 10.17487/RFC4013, February
2005, <http://www.rfc-editor.org/info/rfc4013>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006. Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>.
[RFC5056] Williams, N., "On the Use of Channel Bindings to Secure [RFC5056] Williams, N., "On the Use of Channel Bindings to Secure
Channels", RFC 5056, November 2007. Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007,
<http://www.rfc-editor.org/info/rfc5056>.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC5802] Newman, C., Menon-Sen, A., Melnikov, A., and N. Williams, [RFC5802] Newman, C., Menon-Sen, A., Melnikov, A., and N. Williams,
"Salted Challenge Response Authentication Mechanism "Salted Challenge Response Authentication Mechanism
(SCRAM) SASL and GSS-API Mechanisms", RFC 5802, July 2010. (SCRAM) SASL and GSS-API Mechanisms", RFC 5802,
DOI 10.17487/RFC5802, July 2010,
<http://www.rfc-editor.org/info/rfc5802>.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, July 2010. for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<http://www.rfc-editor.org/info/rfc5929>.
[RFC7235] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol [RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
(HTTP/1.1): Authentication", RFC 7235, June 2014. Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014,
<http://www.rfc-editor.org/info/rfc7235>.
13.2. Informative References 13.2. Informative References
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)", RFC "Remote Authentication Dial In User Service (RADIUS)",
2865, June 2000. RFC 2865, DOI 10.17487/RFC2865, June 2000,
<http://www.rfc-editor.org/info/rfc2865>.
[RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography [RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography
Specification Version 2.0", RFC 2898, September 2000. Specification Version 2.0", RFC 2898,
DOI 10.17487/RFC2898, September 2000,
<http://www.rfc-editor.org/info/rfc2898>.
[RFC2945] Wu, T., "The SRP Authentication and Key Exchange System", [RFC2945] Wu, T., "The SRP Authentication and Key Exchange System",
RFC 2945, September 2000. RFC 2945, DOI 10.17487/RFC2945, September 2000,
<http://www.rfc-editor.org/info/rfc2945>.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
Requirements for Security", BCP 106, RFC 4086, June 2005. "Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<http://www.rfc-editor.org/info/rfc4086>.
[RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol [RFC4510] Zeilenga, K., Ed., "Lightweight Directory Access Protocol
(LDAP): Technical Specification Road Map", RFC 4510, June (LDAP): Technical Specification Road Map", RFC 4510,
2006. DOI 10.17487/RFC4510, June 2006,
<http://www.rfc-editor.org/info/rfc4510>.
[RFC4616] Zeilenga, K., "The PLAIN Simple Authentication and [RFC4616] Zeilenga, K., Ed., "The PLAIN Simple Authentication and
Security Layer (SASL) Mechanism", RFC 4616, August 2006. Security Layer (SASL) Mechanism", RFC 4616,
DOI 10.17487/RFC4616, August 2006,
<http://www.rfc-editor.org/info/rfc4616>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC [RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
4949, August 2007. FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<http://www.rfc-editor.org/info/rfc4949>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[tls-server-end-point] [tls-server-end-point]
Zhu, L., , "Registration of TLS server end-point channel Zhu, L., , "Registration of TLS server end-point channel
bindings", IANA http://www.iana.org/assignments/ bindings", IANA http://www.iana.org/assignments/
channel-binding-types/tls-server-end-point, July 2008. channel-binding-types/tls-server-end-point, July 2008.
Author's Address Author's Address
Alexey Melnikov Alexey Melnikov
Isode Ltd Isode Ltd
 End of changes. 43 change blocks. 
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