--- 1/draft-ietf-kitten-sasl-oauth-03.txt 2012-08-20 20:14:12.209426533 +0200 +++ 2/draft-ietf-kitten-sasl-oauth-04.txt 2012-08-20 20:14:12.249476734 +0200 @@ -1,21 +1,21 @@ KITTEN W. Mills Internet-Draft Yahoo! Inc. Intended status: Standards Track T. Showalter -Expires: February 7, 2013 +Expires: February 21, 2013 H. Tschofenig Nokia Siemens Networks - August 6, 2012 + August 20, 2012 A SASL and GSS-API Mechanism for OAuth - draft-ietf-kitten-sasl-oauth-03 + draft-ietf-kitten-sasl-oauth-04 Abstract OAuth enables a third-party application to obtain limited access to a protected resource, either on behalf of a resource owner by orchestrating an approval interaction, or by allowing the third-party application to obtain access on its own behalf. This document defines how an application client uses OAuth over the Simple Authentication and Security Layer (SASL) or the Generic @@ -39,111 +39,117 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on February 7, 2013. + This Internet-Draft will expire on February 21, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 3. OAuth SASL Mechanism Specification . . . . . . . . . . . . . . 8 - 3.1. Initial Client Response . . . . . . . . . . . . . . . . . 8 - 3.1.1. Reserved Key/Values in OAUTH . . . . . . . . . . . . . 9 - 3.2. Server's Response . . . . . . . . . . . . . . . . . . . . 9 - 3.2.1. Mapping to SASL Identities . . . . . . . . . . . . . . 9 - 3.2.2. Server response to failed authentication. . . . . . . 10 - 3.3. Use of Signature Type Authorization . . . . . . . . . . . 10 - 3.4. Channel Binding . . . . . . . . . . . . . . . . . . . . . 11 - 4. GSS-API OAuth Mechanism Specification . . . . . . . . . . . . 13 - 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 5.1. Successful Bearer Token Exchange . . . . . . . . . . . . . 14 - 5.2. MAC Authentication with Channel Binding . . . . . . . . . 14 - 5.3. Failed Exchange . . . . . . . . . . . . . . . . . . . . . 15 - 5.4. Failed Channel Binding . . . . . . . . . . . . . . . . . . 16 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 17 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 - 7.1. SASL Registration . . . . . . . . . . . . . . . . . . . . 18 - 7.2. GSS-API Registration . . . . . . . . . . . . . . . . . . . 18 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 - 8.1. Normative References . . . . . . . . . . . . . . . . . . . 19 - 8.2. Informative References . . . . . . . . . . . . . . . . . . 20 - Appendix A. Document History . . . . . . . . . . . . . . . . . . 21 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 + 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 8 + 3. OAuth SASL Mechanism Specification . . . . . . . . . . . . . . 9 + 3.1. Initial Client Response . . . . . . . . . . . . . . . . . 9 + 3.1.1. Reserved Key/Values in OAUTH . . . . . . . . . . . . . 10 + 3.1.2. Use of the gs2-header . . . . . . . . . . . . . . . . 11 + 3.2. Server's Response . . . . . . . . . . . . . . . . . . . . 11 + 3.2.1. Mapping to SASL Identities . . . . . . . . . . . . . . 11 + 3.2.2. Server response to failed authentication. . . . . . . 12 + 3.2.3. Completing an error message sequence. . . . . . . . . 12 + 3.3. Use of Signature Type Authorization . . . . . . . . . . . 13 + 3.4. Channel Binding . . . . . . . . . . . . . . . . . . . . . 14 + 4. GSS-API OAuth Mechanism Specification . . . . . . . . . . . . 15 + 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 + 5.1. Successful Bearer Token Exchange . . . . . . . . . . . . . 16 + 5.2. OAuth 1.0a Authorization with Channel Binding . . . . . . 17 + 5.3. Failed Exchange . . . . . . . . . . . . . . . . . . . . . 18 + 5.4. Failed Channel Binding . . . . . . . . . . . . . . . . . . 19 + 5.5. SMTP Example of a failed negotiation. . . . . . . . . . . 19 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 21 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 + 7.1. SASL Registration . . . . . . . . . . . . . . . . . . . . 22 + 7.2. GSS-API Registration . . . . . . . . . . . . . . . . . . . 22 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 + 8.1. Normative References . . . . . . . . . . . . . . . . . . . 23 + 8.2. Informative References . . . . . . . . . . . . . . . . . . 24 + Appendix A. Acknowlegements . . . . . . . . . . . . . . . . . . . 25 + Appendix B. Document History . . . . . . . . . . . . . . . . . . 26 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28 1. Introduction OAuth [I-D.ietf-oauth-v2] enables a third-party application to obtain limited access to a protected resource, either on behalf of a resource owner by orchestrating an approval interaction, or by allowing the third-party application to obtain access on its own behalf. The core OAuth specification [I-D.ietf-oauth-v2] does not define the interaction between the client and the resource server with the access to a protected resource using an Access Token. This - functionality is described in two separate specifications, namely - [I-D.ietf-oauth-v2-bearer], and [I-D.ietf-oauth-v2-http-mac], whereby - the focus is on an HTTP-based environment only. + functionality is described in separate specifications, for example + [I-D.ietf-oauth-v2-bearer], [I-D.ietf-oauth-v2-http-mac], and OAuth + 1.0a [RFC5849] where the focus is on an HTTP-based environment only. Figure 1 shows the abstract message flow as shown in Figure 1 of [I-D.ietf-oauth-v2]. +--------+ +---------------+ | |--(A)- Authorization Request ->| Resource | | | | Owner | | |<-(B)-- Authorization Grant ---| | | | +---------------+ | | | | +---------------+ | |--(C)-- Authorization Grant -->| Authorization | | Client | | Server | | |<-(D)----- Access Token -------| | | | +---------------+ | | - | | +---------------+ + | | +---h------------+ | |--(E)----- Access Token ------>| Resource | | | | Server | | |<-(F)--- Protected Resource ---| | +--------+ +---------------+ Figure 1: Abstract OAuth 2.0 Protocol Flow This document takes advantage of the OAuth protocol and its deployment base to provide a way to use SASL [RFC4422] as well as the GSS-API [RFC2743] to gain access to resources when using non-HTTP- based protocols, such as the Internet Message Access Protocol (IMAP) - [RFC3501], which is what this memo uses in the examples. + [RFC3501] and SMTP [RFC5321], which is what this memo uses in the + examples. The Simple Authentication and Security Layer (SASL) is a framework for providing authentication and data security services in connection-oriented protocols via replaceable mechanisms. It provides a structured interface between protocols and mechanisms. + The resulting framework allows new protocols to reuse existing mechanisms and allows old protocols to make use of new mechanisms. The framework also provides a protocol for securing subsequent protocol exchanges within a data security layer. The Generic Security Service Application Program Interface (GSS-API) [RFC2743] provides a framework for applications to support multiple authentication mechanisms through a unified interface. This document defines a SASL mechanism for OAuth, but it conforms to @@ -176,36 +182,46 @@ authorization server and presenting the authorization grant. (D) The authorization server authenticates the client and validates the authorization grant, and if valid issues an access token. (E) The client requests the protected resource from the resource server and authenticates by presenting the access token. (F) The resource server validates the access token, and if valid, - serves the request. + indicates a successful authentication. Steps (E) and (F) are not defined in [I-D.ietf-oauth-v2] and are the main functionality specified within this document. Consequently, the message exchange shown in Figure 2 is the result of this specification. The client will genrally need to determine the authentication endpoints (and perhaps the service endpoints) before the OAuth 2.0 protocol exchange messages in steps (A)-(D) are executed. The discovery of the resource owner and authorization server endpoints is outside the scope of this specification. The client must discover those endpoints using a discovery mechanisms such as Webfinger using host-meta [I-D.jones-appsawg-webfinger]. In band discovery is not tenable if clients support the OAuth 2.0 password grant. Once credentials are obtained the client proceeds to steps (E) and (F) defined in this specification. + The client need not implement more than one authorization scheme, and + there are no mandatory to implement schemes. The server MUST + advertise at least one scheme if the OAUTH mechanism is offered. + During discovery the client might not find any schemes that it + supports, an OAuth 2.0 enabled client MAY attempt to fetch a + credential for a scheme it supports from a discovered OAuth 2.0 + authorization endpoint. If the client finds no schemes it supports + the client SHOULD provide feedback to the user that the requested + enpoint can not be supported. + ----+ +--------+ +---------------+ | | |--(A)-- Authorization Request --->| Resource | | | | | Owner | |Plain | |<-(B)------ Access Grant ---------| | |OAuth | | +---------------+ |2.0 | | | | | Client Credentials & +---------------+ | | |--(C)------ Access Grant -------->| Authorization | | | Client | | Server | | @@ -217,115 +233,158 @@ | | | | |OAuth | |--(E)------ Access Token -------->| Resource | |over | | | Server | |SASL/ | |<-(F)---- Protected Resource -----| | |GSS- | | | | |API +--------+ +---------------+ | ----+ Figure 2: OAuth SASL Architecture - It is worthwhile to note that this specification is also compatible - with OAuth 1.0a [RFC5849]. - 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. The reader is assumed to be familiar with the terms used in the OAuth 2.0 specification [I-D.ietf-oauth-v2]. In examples, "C:" and "S:" indicate lines sent by the client and server respectively. Line breaks have been inserted for readability. Note that the IMAP SASL specification requires base64 encoding message, not this memo. 3. OAuth SASL Mechanism Specification SASL is used as a generalized authentication method in a variety of application layer protocols. This document defines two SASL mechanisms for usage with OAuth: "OAUTH" and "OAUTH-PLUS". The - "OAUTH" SASL mechanism enables OAuth authorizattion schemes for SASL, + "OAUTH" SASL mechanism enables OAuth authorization schemes for SASL, "OAUTH-PLUS" adds channel binding [RFC5056] capability for additional security guarantees. + This mechanism is client initiated and lock-step, the server always + replying to a client message. In the case where the client has and + correctly uses a valid token the flow is: + + o Client sends a valid and correct initial client response. + + o Server responds with a successful authentication. + + In the case where authorization fails the server sends an error + result, then client MUST then send an additional message to the + server in order to allow the server to finish the exchange. Some + protocols and common SASL implementations do not support both sending + a SASL message and finalizing a SASL negotiation, the additional + client message in the error case deals with this problem. This + exchange is: + + o Client sends an invalid initial client response. + + o Server responds with an error message. + + o Client sends an empty client reponse. + + o Server fails the authentication. + 3.1. Initial Client Response - Client responses are a key/value pair sequence. These key/value - pairs carry the equivalent values from an HTTP context in order to be - able to complete an OAuth style HTTP authorization. The ABNF - [RFC5234] syntax is + Client responses are a key/value pair sequence. The initial client + response includes a gs2-header as defined in GSS-API [RFC5801], which + carries the authorization ID as a hint. These key/value pairs carry + the equivalent values from an HTTP context in order to be able to + complete an OAuth style HTTP authorization. The client MUST send an + authorization ID in the gs2-header. The server MAY use this as a + routing or database lookup hint. The server MUST NOT use this as + authoritative, the user name MUST be asserted by the OAuth + credential. The ABNF [RFC5234] syntax is: kvsep = %x01 key = 1*ALPHA value = *(VCHAR | SP | HTAB | CR | LF ) kvpair = key "=" value kvsep - client_resp = 1*kvpair kvsep + client_resp = 0*kvpair kvsep + ;; gs2-header = As defined in GSS-API + initial_client_resp = gs2-header kvsep client_resp The following key/value pairs are defined in the client response: auth (REQUIRED): The payload of the HTTP Authorization header for an equivalent HTTP OAuth authroization. - user (REQUIRED): Contains the user name being authenticated. The - server MAY use this as a routing or database lookup hint. The - server MUST NOT use this as authoritative, the user name MUST - be asserted by the OAuth credential. - host: Contains the host name to which the client connected. port: Contains the port number represented as a decimal positive integer string without leading zeros to which the client connected. + qs: The HTTP query string. In OAUTH this is reserved, the client + SHOUD NOT send it, and has the default value of "". In OAUTH- + PLUS this carries a single key value pair "cbdata" for the + channel binding data payload formatted as an HTTP query string. + In authorization schemes that use signatures, the client MUST send host and port number key/values, and the server MUST fail an authorization request requiring signatures that does not have host - and port values. + and port values. For authorization schemes that require a scheme as + part of the URI being signed "http" is always used. 3.1.1. Reserved Key/Values in OAUTH In the OAUTH mechanism values for path, query string and post body are assigned default values. OAuth authorization schemes MAY define usage of these in the SASL context and extend this specification. For OAuth schemes that use request signatures the default values MUST be used unless explict values are provided in the client response. The following key values are reserved for future use: - path (RESERVED): HTTP path data, the default value is "/". + mthd (RESERVED): HTTP method for use in signatures, the default + value is "POST". - qs (RESERVED): HTTP query string, the default value is "". + path (RESERVED): HTTP path data, the default value is "/". post (RESERVED): HTTP post data, the default value is "". +3.1.2. Use of the gs2-header + + The gs2-header is used as follows: + + o The "gs2-nonstd-flag" MUST NOT be present. + + o The "gs2-authzid" carries the authorization identity as specified + in [RFC5801]. + + In the OAUTH mechanism the "gs2-cb-flag" MUST be set to "n" because + channel-binding [RFC5056] data is not expected. In the OAUTH-PLUS + mechanism the "gs2-cb-flag" MUST be set appropriately by the client. + 3.2. Server's Response The server validates the response per the specification for the authorization scheme used. If the authorization scheme used includes signing of the request parameters the client must provide a client response that satisfies the data requirements for the scheme in use. In the OAUTH-PLUS mechanism the server examines the channel binding data, extracts the channel binding unique prefix, and extracts the raw channel biding data based on the channel binding type used. It then computes it's own copy of the channel binding payload and compares that to the payload sent by the client in the cbdata key/ value. Those two must be equal for channel binding to succeed. The server responds to a successfully verified client message by - completing the SASL negotiation. The authentication scheme MUST - carry the user ID to be used as the authorization identity (identity - to act as). The server MUST use the ID obtained from the credential - as the user being authorized. + completing the SASL negotiation. The authorization scheme MUST carry + the user ID to be used as the authorization identity (identity to act + as). The server MUST use the ID obtained from the credential as the + user being authorized. 3.2.1. Mapping to SASL Identities Some OAuth mechanisms can provide both an authorization identity and an authentication identity. An example of this is OAuth 1.0a [RFC5849] where the consumer key (oauth_consumer_key) identifies the entity using the token which equates to the SASL authentication identity, and is authenticated using the shared secret. The authorization identity in the OAuth 1.0a case is carried in the token (per the requirement above), which SHOULD be validated independently. @@ -342,119 +401,131 @@ result consists of the following values: status (REQUIRED): The authorization error code. Valid error codes are defined in the IANA [[need registry name]] registry specified in the OAuth 2 core specification. schemes (REQUIRED): A space separated list of the OAuth authorization schemes supported by the server, i.e. "bearer" or "bearer mac". - scope (OPTIONAL): The OAuth scope required to access the service. + scope (OPTIONAL): An OAuth scope which is valid to access the + service. This may be empty which implies that unscoped tokens + are required, or a space separated list. Use of a space + separated list is NOT RECOMMENDED. If the resource server provides a scope the client SHOULD always request scoped tokens from the token endpoint. The client MAY use a scope other than the one provided by the resource server. Scopes other than those advertised by the resource server are be defined by the resource owner and provided in service documentation or discovery information (which is beyond the scope of this memo). If not present then the client SHOULD presume an empty scope (unscoped token) is needed. If channel binding is in use and the channel binding fails the server responds with a status code set to 412 to indicate that the channel binding precondition failed. If the authentication scheme in use does not include signing the server SHOULD revoke the presented credential and the client SHOULD discard that credential. +3.2.3. Completing an error message sequence. + + If the client gets an error message form the server it MUST send an + empty client response consisting of a single %x01 (control A) + character, which is a correctly formatted client response with no + key/value pairs. The server then completes the SASL negotiation with + a failure result. + 3.3. Use of Signature Type Authorization This mechanism supports authorization using signatures, which requires that both client and server construct the string to be signed. OAuth 2 is designed for authentication/authorization to access specific URIs. SASL is designed for user authentication, and has no facility for being more specific. In this mechanism we require or define default values for the data elements from an HTTP request which allow the signature base string to be constructed properly. The default HTTP path is "/" and the default post body is empty. These atoms are defined as extension points so that no changes are needed if there is a revision of SASL which supports more specific resource authorization, e.g. IMAP access to a specific folder or FTP access limited to a specific directory. - Using the example in the MAC specification - [I-D.ietf-oauth-v2-http-mac] as a starting point, on an IMAP server - running on port 143 and given the MAC style authorization request - (with %x01 shown as ^A and line breaks added for readability) below: + Using the example in the OAuth 1.0a specification as a starting + point, on an IMAP server running on port 143 and given the OAuth 1.0a + style authorization request (with %x01 shown as ^A and line breaks + added for readability) below: - host=server.example.com^A - user=user@example.com^A + n,a=user@example.com,^A + host=example.com^A port=143^A - auth=MAC token="h480djs93hd8",timestamp="137131200",nonce="dj83hs9s", - signature="YTVjyNSujYs1WsDurFnvFi4JK6o="^A^A + auth=OAuth realm="Example", + oauth_consumer_key="9djdj82h48djs9d2", + oauth_token="kkk9d7dh3k39sjv7", + oauth_signature_method="HMAC-SHA1", + oauth_timestamp="137131201", + oauth_nonce="7d8f3e4a", + oauth_signature="Tm90IGEgcmVhbCBzaWduYXR1cmU%3D"^A^A - The normalized request string would be constructed per the MAC - specification [I-D.ietf-oauth-v2-http-mac]. In this example the - normalized request string with the new line separator character is - represented by "\n" for display purposes only would be: + The signature base string would be constructed per the OAuth 1.0 + specification [RFC5849] with the following things noted: - h480djs93hi8\n - 137131200\n - dj83hs9s\n - \n - GET\n - server.example.com\n - 143\n - /\n - \n + o The method value is defaulted to POST. + + o The scheme defaults to be "http", and any port number other than + 80 is included. + + o The path defaults to "/". + + o The query string defaults to "". + + In this example the signature base string with line breaks added for + readability would be: + + POST&http%3A%2F%2Fexample.com:143%2F&oauth_consumer_key%3D9djdj82h4 + 8djs9d2%26oauth_nonce%3D7d8f3e4a%26oauth_signature_method%3DHMAC-SH + A1%26oauth_timestamp%3D137131201%26oauth_token%3Dkkk9d7dh3k39sjv7 3.4. Channel Binding - If the specification for the underlying authorization scheme requires - a security layer, such as TLS [RFC5246], the server SHOULD only offer - a mechanism where channel binding can be enabled. + The channel binding data is carried in the "qs" (query string) key + value pair formatted as a standard HTTP query parameter with the name + "cbdata". Channel binding requires that the channel binding data be + integrity protected end-to-end in order to protect against man-in- + the-middle attacks. All authorization schemes offered in an OAUTH- + PLUS mechanism MUST provide integrity protection. It should be noted + that while the Bearer token scheme specifies SSL for normal usage it + offers no integrity protection and is not suitable for use in OAUTH- + PLUS. The channel binding data is computed by the client based on it's choice of preferred channel binding type. As specified in [RFC5056], the channel binding information MUST start with the channel binding unique prefix, followed by a colon (ASCII 0x3A), followed by a base64 encoded channel binding payload. The channel binding payload is the - raw data from the channel binding type if the raw channel binding - data is less than 500 bytes. If the raw channel binding data is 500 - bytes or larger then a SHA-1 [RFC3174] hash of the raw channel - binding data is computed. - - If the client is using tls-unique for a channel binding then the raw - channel binding data equals the first TLS finished message. This is - under the 500 byte limit, so the channel binding payload sent to the - server would be the base64 encoded first TLS finished message. - - In the case where the client has chosen tls-endpoint, the raw channel - binding data is the certificate of the server the client connected - to, which will frequently be 500 bytes or more. If it is then the - channel binding payload is the base64 encoded SHA-1 hash of the - server certificate. + raw data from the channel binding type. For example, if the client + is using tls-unique for channel binding then the raw channel binding + data is the TLS finished message as specified in section 3.1 of + [RFC5929]. 4. GSS-API OAuth Mechanism Specification Note: The normative references in this section are informational for SASL implementers, but they are normative for GSS-API implementers. The SASL OAuth mechanism is also a GSS-API mechanism and the messages described in Section 3 are the same, but - 1. the GS2 header on the client's first message is excluded when - OAUTH is used as a GSS-API mechanism, and - - 2. initial context token header is prefixed to the client's first - authentication message (context token), as described in Section - 3.1 of RFC 2743, + 1. the initial context token header is prefixed to the client's + first authentication message (context token), as described in + Section 3.1 of RFC 2743, The GSS-API mechanism OID for OAuth is [[TBD: IANA]]. OAuth security contexts always have the mutual_state flag (GSS_C_MUTUAL_FLAG) set to TRUE. OAuth supports credential delegation, therefore security contexts may have the deleg_state flag (GSS_C_DELEG_FLAG) set to either TRUE or FALSE. The mutual authentication property of this mechanism relies on successfully comparing the TLS server identity with the negotiated @@ -486,170 +557,223 @@ These example illustrate exchanges between an IMAP client and an IMAP server. Note to implementers: Authorization scheme names are case insensitive. One example uses "Bearer" but that could as easily be "bearer", "BEARER", or "BeArEr". 5.1. Successful Bearer Token Exchange - This example shows a successful OAuth 2.0 bearer token exchange with - an initial client response. Note that line breaks are inserted for - readability. + This example shows a successful OAuth 2.0 bearer token exchange. + Note that line breaks are inserted for readability. S: * IMAP4rev1 Server Ready C: t0 CAPABILITY S: * CAPABILITY IMAP4rev1 AUTH=OAUTH S: t0 OK Completed - C: t1 AUTHENTICATE OAUTH aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BcG9ydD0xNDMB - dXNlcj11c2VyQGV4YW1wbGUuY29tAWF1dGg9QmVhcmVyIHZGOWRmdDRxbVRjMk5 + C: t1 AUTHENTICATE OAUTH bixhPXVzZXJAZXhhbXBsZS5jb20sAWhvc3Q9c2VydmVy + LmV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9QmVhcmVyIHZGOWRmdDRxbVRjMk5 2YjNSbGNrQmhiSFJoZG1semRHRXVZMjl0Q2c9PQEB - S: + S: t1 OK SASL authentication succeeded As required by IMAP [RFC3501], the payloads are base64-encoded. The decoded initial client response (with %x01 represented as ^A and long lines wrapped for readability) is: - host=server.example.com^Aport=143^Auser=user@example.com^A + n,a=user@example.com,^Ahost=server.example.com^Aport=143^A auth=Bearer vF9dft4qmTc2Nvb3RlckBhbHRhdmlzdGEuY29tCg==^A^A - The line containing just a "+" and a space is an empty response from - the server. This response contains error information, and in the - success case the error response is empty. Like other messages, and - in accordance with the IMAP SASL binding, the empty response is - base64-encoded. + The same credential used in an SMTP exchange is shown below. Note + that line breaks are inserted for readability, and that the SMTP + protocol terminates lines with CR and LF characters (ASCII values + 0x0D and 0x0A), these are not displayed explicitly in the example. -5.2. MAC Authentication with Channel Binding + [connection begins] + S: 220 mx.example.com ESMTP 12sm2095603fks.9 + C: EHLO sender.example.com + S: 250-mx.example.com at your service,[172.31.135.47] + S: 250-SIZE 35651584 + S: 250-8BITMIME + S: 250-AUTH LOGIN PLAIN OAUTH + S: 250-ENHANCEDSTATUSCODES + S: 250-PIPELINING + C: t1 AUTHENTICATE OAUTH bixhPXVzZXJAZXhhbXBsZS5jb20sAWhvc3Q9c2VydmVy + LmV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9QmVhcmVyIHZGOWRmdDRxbVRjMk5 + 2YjNSbGNrQmhiSFJoZG1semRHRXVZMjl0Q2c9PQEB + S: 235 Authentication successful. + [connection continues...] - This example shows a channel binding failure. The example sends the - same request as above, but in the context of an OAUTH-PLUS exchange - the channel binding information is missing. Note that line breaks - are inserted for readability. +5.2. OAuth 1.0a Authorization with Channel Binding + + This example shows channel binding in the context of an OAuth 1.0a + signed authorization request. Note that line breaks are inserted for + readability. S: * CAPABILITY IMAP4rev1 AUTH=OAUTH SASL-IR IMAP4rev1 Server Ready S: t0 OK Completed -C: t1 AUTHENTICATE OAUTH-PLUS aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BdXNlcj11c2 - VyQGV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9TUFDIHRva2VuPSJoNDgwZGpzOTNo - ZDgiLHRpbWVzdGFtcD0iMTM3MTMxMjAwIixub25jZT0iZGo4M2hzOXMiLHNpZ25hdH - VyZT0iWVRWanlOU3VqWXMxV3NEdXJGbnZGaTRKSzZvPSIBY2JkYXRhPVNHOTNJR0pw - WnlCcGN5QmhJRlJNVXlCbWFXNWhiQ0J0WlhOellXZGxQd289AQE= -S: + +C: t1 AUTHENTICATE OAUTH-PLUS eSxhPXVzZXJAZXhhbXBsZS5jb20sAWhvc3Q9c2Vydm + VyLmV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9T0F1dGggcmVhbG09IkV4YW1wbGUi + LG9hdXRoX2NvbnN1bWVyX2tleT0iOWRqZGo4Mmg0OGRqczlkMiIsb2F1dGhfdG9rZW + 49ImtrazlkN2RoM2szOXNqdjciLG9hdXRoX3NpZ25hdHVyZV9tZXRob2Q9IkhNQUMt + U0hBMSIsb2F1dGhfdGltZXN0YW1wPSIxMzcxMzEyMDEiLG9hdXRoX25vbmNlPSI3ZD + hmM2U0YSIsb2F1dGhfc2lnbmF0dXJlPSJTU2R0SUdFZ2JHbDBkR3hsSUhSbFlTQndi + M1F1IgFxcz1jYmRhdGE9dGxzLXVuaXF1ZTpTRzkzSUdKcFp5QnBjeUJoSUZSTVV5Qm + 1hVzVoYkNCdFpYTnpZV2RsUHdvPQEB S: t1 OK SASL authentication succeeded As required by IMAP [RFC3501], the payloads are base64-encoded. The - decoded initial client response (with %x01 represented as ^A and long + decoded initial client response (with %x01 represented as ^A and lines wrapped for readability) is: - - + y,a=user@example.com,^A host=server.example.com^A - user=user@example.com^A port=143^A - auth=MAC token="h480djs93hd8",timestamp="137131200",nonce="dj83hs9s", - signature="YTVjyNSujYs1WsDurFnvFi4JK6o="^A - cbdata=SG93IGJpZyBpcyBhIFRMUyBmaW5hbCBtZXNzYWdlPwo=^A^A + auth=OAuth realm="Example", + oauth_consumer_key="9djdj82h48djs9d2", + oauth_token="kkk9d7dh3k39sjv7", + oauth_signature_method="HMAC-SHA1", + oauth_timestamp="137131201", + oauth_nonce="7d8f3e4a", + oauth_signature="SSdtIGEgbGl0dGxlIHRlYSBwb3Qu"^A + qs=cbdata=tls-unique:SG93IGJpZyBpcyBhIFRMUyBmaW5hbCBtZXNzYWdlPwo=^A^A - The line containing just a "+" and a space is an empty response from - the server. This response contains discovery information, and in the - success case no discovery information is necessary so the response is - empty. Like other messages, and in accordance with the IMAP SASL - binding, the empty response is base64-encoded. + In this example the signature base string with line breaks added for + readability would be: + + POST&http%3A%2F%2Fserver.example.com:143%2F&cbdata=tls-unique:SG93I + GJpZyBpcyBhIFRMUyBmaW5hbCBtZXNzYWdlPwo=%26oauth_consumer_key%3D9djd + j82h48djs9d2%26oauth_nonce%3D7d8f3e4a%26oauth_signature_method%3DHM + AC-SHA1%26oauth_timestamp%3D137131201%26oauth_token%3Dkkk9d7dh3k39s + jv7 5.3. Failed Exchange This example shows a failed exchange because of the empty Authorization header, which is how a client can query for the needed scope. Note that line breaks are inserted for readability. S: * CAPABILITY IMAP4rev1 AUTH=OAUTH SASL-IR IMAP4rev1 Server Ready S: t0 OK Completed - C: t1 AUTHENTICATE OAUTH aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BdXNlcj11 - c2VyQGV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9AQE= - S: + eyJzdGF0dXMiOiI0MDEiLCJzY2hlbWVzIjoiYmVhcmVyIG1hYyIsInNjb3Bl - IjoiZXhhbXBsZV9zY29wZSJ9 + C: t1 AUTHENTICATE OAUTH bixhPXVzZXJAZXhhbXBsZS5jb20sAWhvc3Q9c2Vy + dmVyLmV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9AQE= + S: + ewoic3RhdHVzIjoiNDAxIiwKInNjaGVtZXMiOiJiZWFyZXIiLAoic2NvcGUi + OiJleGFtcGxlX3Njb3BlIgp9 + C: + AQ== S: t1 NO SASL authentication failed The decoded initial client response is: - host=server.example.com^Auser=user@example.com^Aport=143^Aauth=^A^A + n,a=user@example.com,^Ahost=server.example.com^Aport=143^Aauth=^A^A + The decoded server error response is: { "status":"401", - "schemes":"bearer mac", + "schemes":"bearer", "scope":"example_scope" } + The client responds with the required empty response. + 5.4. Failed Channel Binding This example shows a channel binding failure in an empty request. The channel binding information is empty. Note that line breaks are inserted for readability. - S: * CAPABILITY IMAP4rev1 AUTH=OAUTH SASL-IR IMAP4rev1 Server Ready +S: * CAPABILITY IMAP4rev1 AUTH=OAUTH OAUTH-PLUS SASL-IR IMAP4rev1 Server + Ready S: t0 OK Completed - C: t1 AUTHENTICATE OAUTH aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BdXNlcj11 - c2VyQGV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9AWNiZGF0YT0BAQ== - S: + eyJzdGF0dXMiOiI0MTIiLCJzY2hlbWVzIjoiYmVhcmVyIG1hYyIsInNjb3Bl - IjoiZXhhbXBsZV9zY29wZSJ9 +C: t1 AUTHENTICATE OAUTH-PLUS eSxhPXVzZXJAZXhhbXBsZS5jb20sAWhvc3Q9c2Vydm + VyLmV4YW1wbGUuY29tAXBvcnQ9MTQzAWF1dGg9AWNiZGF0YT0BAQ== +S: + ewoic3RhdHVzIjoiNDEyIiwKInNjaGVtZXMiOiJiZWFyZXIgb2F1dGgiLAoi + c2NvcGUiOiJleGFtcGxlX3Njb3BlIgp9 +C: + AQ== S: t1 NO SASL authentication failed The decoded initial client response is: - host=server.example.com^Auser=user@example.com^Aport=143^A + y,a=user@example.com,^A + host=server.example.com^Aport=143^A auth=^Acbdata=^A^A The decoded server response is: { "status":"412", - "schemes":"bearer mac", + "schemes":"bearer oauth", "scope":"example_scope" } + The client responds with the required empty response. + +5.5. SMTP Example of a failed negotiation. + + This example shows an authorization failure in an SMTP exchange. + Note that line breaks are inserted for readability, and that the SMTP + protocol terminates lines with CR and LF characters (ASCII values + 0x0D and 0x0A), these are not displayed explicitly in the example. + +[connection begins] +S: 220 mx.example.com ESMTP 12sm2095603fks.9 +C: EHLO sender.example.com +S: 250-mx.example.com at your service,[172.31.135.47] +S: 250-SIZE 35651584 +S: 250-8BITMIME +S: 250-AUTH LOGIN PLAIN OAUTH +S: 250-ENHANCEDSTATUSCODES +S: 250-PIPELINING +C: AUTH OAUTH dXNlcj1zb21ldXNlckBleGFtcGxlLmNvbQFhdXRoPUJlYXJlciB2RjlkZn + Q0cW1UYzJOdmIzUmxja0JoZEhSaGRtbHpkR0V1WTI5dENnPT0BAQo= +S: 334 eyJzdGF0dXMiOiI0MDEiLCJzY2hlbWVzIjoiYmVhcmVyIG1hYyIsInNjb3BlIjoia + HR0cHM6Ly9tYWlsLmdvb2dsZS5jb20vIn0K +C: AQ== +S: 535-5.7.1 Username and Password not accepted. Learn more at +S: 535 5.7.1 http://support.example.com/mail/oauth +[connection continues...] + + The client responds with the required empty response. + 6. Security Considerations This mechanism does not provide a security layer, but does provide a provision for channel binding. The OAuth 2 specification [I-D.ietf-oauth-v2] allows for a variety of usages, and the security properties of these profiles vary. The usage of bearer tokens, for example, provide security features similar to cookies. Applications using this mechanism SHOULD exercise the same level of care using this mechanism as they would in using the SASL PLAIN mechanism. In particular, TLS 1.2 or an equivalent secure channel MUST be implemented and its usage is RECOMMENDED. - Channel binding in this mechanism has different properties based on - the authentication scheme used. Channel binding to TLS with a bearer - token provides only a binding to the TLS layer. Authentication - schemes like MAC tokens can implement a signature over the channel - binding information. These provide additional protection against a - man in the middle attacks, and the MAC authorization header is bound - to the channel and only valid in that context. + The channel binding in this mechanism has different properties based + on the authentication scheme used. The integrity guarantee for + channel binding depends on the quality of the guarantee in the the + authorization scheme. It is possible that SASL will be authenticating a connection and the life of that connection may outlast the life of the token used to authenticate it. This is a common problem in application protocols where connections are long-lived, and not a problem with this mechanism per se. Servers MAY unilaterally disconnect clients in accordance with the application protocol. An OAuth credential is not equivalent to the password or primary account credential. There are protocols like XMPP that allow actions like change password. The server SHOULD ensure that actions taken in the authenticated channel are appropriate to the strength of the presented credential. Tokens have a lifetime associated with them. Reducing the lifetime - of a token provides security benefits in case that tokens leak. In - addition a previously obtained token MAY be revoked or rendered + of a token provides security benefits in the case that tokens leak. + In addition a previously obtained token MAY be revoked or rendered invalid at any time. The client MAY request a new access token for each connection to a resource server, but it SHOULD cache and re-use access credentials that appear to be valid. 7. IANA Considerations 7.1. SASL Registration The IANA is requested to register the following SASL profile: @@ -693,25 +817,20 @@ [I-D.ietf-oauth-v2] Hardt, D., "The OAuth 2.0 Authorization Framework", draft-ietf-oauth-v2-31 (work in progress), August 2012. [I-D.ietf-oauth-v2-bearer] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", draft-ietf-oauth-v2-bearer-23 (work in progress), August 2012. - [I-D.ietf-oauth-v2-http-mac] - Hammer-Lahav, E., "HTTP Authentication: MAC Access - Authentication", draft-ietf-oauth-v2-http-mac-01 (work in - progress), February 2012. - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", @@ -731,20 +850,23 @@ [RFC5056] Williams, N., "On the Use of Channel Bindings to Secure Channels", RFC 5056, November 2007. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. + [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, + October 2008. + [RFC5801] Josefsson, S. and N. Williams, "Using Generic Security Service Application Program Interface (GSS-API) Mechanisms in Simple Authentication and Security Layer (SASL): The GS2 Mechanism Family", RFC 5801, July 2010. [RFC5849] Hammer-Lahav, E., "The OAuth 1.0 Protocol", RFC 5849, April 2010. [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings for TLS", RFC 5929, July 2010. @@ -752,32 +874,60 @@ [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, March 2011. 8.2. Informative References + [I-D.ietf-oauth-v2-http-mac] + Hammer-Lahav, E., "HTTP Authentication: MAC Access + Authentication", draft-ietf-oauth-v2-http-mac-01 (work in + progress), February 2012. + [I-D.jones-appsawg-webfinger] Jones, P., Salgueiro, G., and J. Smarr, "WebFinger", draft-jones-appsawg-webfinger-06 (work in progress), June 2012. [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC 3501, March 2003. -Appendix A. Document History +Appendix A. Acknowlegements + + The authors would like to thank the members of the Kitten working + group, and in addition and specifically: Simon Josefson, Torsten + Lodderstadt, Ryan Troll, and Nico Williams. + +Appendix B. Document History [[ to be removed by RFC editor before publication as an RFC ]] + -04 + + o Changed user field to be carried in the gs2-header, and made gs2 + header explicit in all cases. + + o Converted MAC examples to OAuth 1.0a. Moved MAC to an informative + reference. + + o Changed to sending an empty client response (single control-A) as + the second message of a failed sequence. + + o Fixed channel binding prose to refer to the normative specs and + removed the hashing of large channel binding data, which brought + mroe problems than it solved. + + o Added a SMTP examples for Bearer use case. + -03 o Added user field into examples and fixed egregious errors there as well. o Added text reminding developers that Authorization scheme names are case insensitive. -02 @@ -792,24 +942,20 @@ o Replacing HTTP as the message format and adjusted all examples. -00 o Renamed draft into proper IETF naming format now that it's adopted. o Minor fixes. - -00 - - o Initial revision - Authors' Addresses William Mills Yahoo! Inc. Phone: Email: wmills@yahoo-inc.com Tim Showalter