diff --git a/xep-0285.xml b/xep-0285.xml new file mode 100755 index 00000000..c2028045 --- /dev/null +++ b/xep-0285.xml @@ -0,0 +1,321 @@ + + + BASE64 RFC 4648: The Base16, Base32, and Base64 Data <http://tools.ietf.org/html/rfc4648>." > + DATETIME RFC 3339: Date and Time on the Internet Timestamps <http://tools.ietf.org/html/rfc3339>." > + XMLDSIG XML Signature Syntax and Processing, W3C Recommendation, 10 June 2008 <http://www.w3.org/TR/xmldsig-core/>." > + E2EEncrypt End-to-End Object Encryption for the Extensible Messaging and Presence Protocol (XMPP), Miller, M. and P. Saint-Andre, work in progress <http://datatracker.ietf.org/doc/draft-miller-3923bis>." > +%ents; +]> + + +
+ Digital Signatures in XMPP + This document provides a technical specification for Digital Signatures in the + Extensible Messaging and Presence Protocol (XMPP). &LEGALNOTICE; + 0285 + Experimental + Technical Specification + Standards + Council + + XMPP Core + XEP-0001 + + + + N/A + &kdz; + + 0.1 + 2010-09-15 + psa +

Initial published version.

 + + + 0.0 + 2010-03-10 + kdz + +

Proto-XEP draft.

+ + +
+ + +

This document provides a technical specification for Digital Signatures in Extensible + Messaging and Presence Protocol (&xmpp;) based upon End-to-End Object Encryption + (&E2EEncrypt;) "work in progress".

+

The S/MIME approach defined in &rfc3923; has never been implemented in XMPP clients to the + best of our knowledge, but has some attractive features, especially the ability to + store-and-forward a signed message at a user's server if the user is not online when the + message is received (in the XMPP community this is called "offline storage" and the message is + referred to as an "offline message"). The authors surmise that RFC 3923 has not been + implemented mainly because it adds several new dependencies to XMPP clients, especially MIME + (along with the CPIM and MSGFMT media types). This document explores the possibility of an + approach that is similar to but simpler than RFC 3923.

+ + +

The process that a sending agent follows for securing stanzas is very similar regardless of + the form of stanza (i.e., <iq/>, <message/>, or <presence/>).

+
    +
  1. Constructs a cleartext version of the stanza, S.
    2. +
  2. Notes the current UTC date and time N when this stanza is constructed, formatted as + described in Section 5.
    3. +
  3. Converts the stanza to a UTF-8, as defined by &rfc3269;, encoded string, optionally + removing line breaks and other insignificant whitespace between elements and attributes, + i.e., UTF8-encode(S) = S'. We call S' a "stanza-string" because for purposes of signing and + verification it is treated not as XML but as an opaque string (this avoids the need for + complex canonicalization of the XML input).
    4. +
  4. Constructs a plaintext envelope (E) <plain/> qualified by the "urn:xmpp:signed:0" + namespace as follows:
      +
    • The attribute 'timestamp' set to the UTC date and time value N
      • +
    • The XML character data set to the base64-encoded form of S' (where the encoding + adheres to the definition in Section 4 of &BASE64; and where the padding bits are set to + zero). This encoding is necessary to preserve a canonicalized form of S'.
      • +
    +
    5. +
  5. Converts the envelope (E) to a UTF-8 encoded string, optionally removing line breaks and + other insignificant whitespace between elements and attributes, i.e., E' = + UTF8-encode(E).
    6. +
  6. Produce a signature of UTF8-encoded envelope (E') using the intended signature algorithm. + T = signature(E'). (This step is underspecified and will be expanded upon in later revision + of this document.)
    7. +
  7. Base64-encodes T to produce the signature data T'.
    8. +
  8. Constructs an <signed/> element qualified by the "urn:xmpp:signed:0" namespace as + follows:
      +
    • The child element <signature> (implicitly qualified by the "urn:xmpp:signed:0" + namespace) as follows:
        +
      • The attribute 'algorithm' set to a string identifying the signature algorithm + used.
        • +
      • The XML character data T'.
        • +
      • +
    • The child element <data> (implicitly qualified by the "urn:xmpp:signed:0" + namespace) as follows:
        +
      • The XML character data E'.
        • +
      +
      • +
    +
    9. +
  9. Sends the <signed> element as the payload of a stanza that SHOULD match the stanza + from step 1 in kind (e.g., <message/>), type (e.g., "chat"), and addressing (e.g. + to="romeo@montague.net" from="juliet@capulet.net/balcony"). If the original stanza (S) has a + value for the "id" attribute, this stanza MUST NOT use the same value for its "id" + attribute.
    10. +
+ + +

The sender begins with the cleartext version of the <message/> stanza "S":

+ + 8996aef0-061d-012d-347a-549a200771aa + Wherefore art thou, Romeo? + + ]]> + +

The sender then performs the steps 1 through 4 from above to generate:

+ + PG1lc3NhZ2UgeG1sbnM9ImphYmJlcjpjbGllbnQiIGZyb209Imp1bGlldEBjYXB + 1bGV0Lm5ldC9iYWxjb255IiB0bz0icm9tZW9AbW9udGVndWUubmV0IiB0eXBlPS + JjaGF0Ij48dGhyZWFkPmM2MzczODI0LWEzMDctNDBkZC04ZmUwLWJhZDZlNzI5O + WFkMDwvdGhyZWFkPjxib2R5PldoZXJlZm9yZSBhcnQgdGhvdSwgUm9tZW8/PC9i + b2R5PjwvbWVzc2FnZT4= + + ]]> +

And then performs steps 5 through 9 steps, causing the following to be sent:

+ + + + DxbxIziY1C1Ytcxkj0IFLsfmDLMv96JMlMAQZ7jh49IbsOIPsxI2LyLmqhKH/994UXDJKQLHvLJz + gAmw8V2b+zmyZeItJzSmB+HHiLFVXkD2Dd4JfetsafsfIcB7uNWg0gAeiKrTHfFgiyEC/2WxwOj3 + JUMRyQ9ykEPIzS0GZ/k= + + + PHBsYWluIHhtbG5zPSJ1cm46eG1wcDpzaWduZWQ6MCIgdGltZXN0YW1wPSIyMDEwLTA2LTI5VDAy + OjE1OjIxLjAxMloiPgogIFBHMWxjM05oWjJVZ2VHMXNibk05SW1waFltSmxjanBqYkdsbGJuUWlJ + R1p5YjIwOUltcDFiR2xsZEVCallYQgogIDFiR1YwTG01bGRDOWlZV3hqYjI1NUlpQjBiejBpY205 + dFpXOUFiVzl1ZEdWbmRXVXVibVYwSWlCMGVYQmxQUwogIEpqYUdGMElqNDhkR2h5WldGa1BtTTJN + emN6T0RJMExXRXpNRGN0TkRCa1pDMDRabVV3TFdKaFpEWmxOekk1TwogIFdGa01Ed3ZkR2h5WldG + a1BqeGliMlI1UGxkb1pYSmxabTl5WlNCaGNuUWdkR2h2ZFN3Z1VtOXRaVzgvUEM5aQogIGIyUjVQ + and2YldWemMyRm5aVDQ9CjwvcGxhaW4+Cg== + + + + ]]> + + + +

To be added....

+ + + +

The following limitations and caveats apply:

+ + + + + +

Several scenarios are possible when an entity receives an encrypted stanza:

+ +
+ +
Case #1:
+
The receiving application does not understand the protocol.
+ + +
Case #2:
+
The receiving application understands the protocol and is able to verify the + signature.
+ + +
Case #3:
+
The receiving application understands the protocol and is able to verify the signature, + but the timestamps fail the checks specified under Checking of Timestamps.
+ + +
Case #4:
+
The receiving application understands the protocol and is unable to verify the + signature.
+ +
+ +

In Case #1, the receiving application MUST do one and only one of the following: (1) ignore + the <signed/> extension, (2) ignore the entire stanza, or (3), except where precluded by + the protocol (&rfc3920bis;), return a <service-unavailable/> error to the sender.

+

In Case #2, the receiving application MUST NOT return a stanza error to the sender, since + this is the success case.

+

In Case #3, the receiving application MAY, except where precluded by the protocol, return a + <not-acceptable/> error to the sender, optionally supplemented by an + application-specific error condition element of <bad-timestamp/> as shown below:

+ + + XML-character-data-here + + + + + + + ]]> +

In Case #4, the receiving application SHOULD, except as precluded by the protocol, return a + <bad-request/> error to the sender, optionally supplemented by an application-specific + error condition element of <bad-signature/> as shown below:

+ + + XML-character-data-here + + + + + + + ]]> +

Additionally in Case #4, the receiving application SHOULD NOT present the stanza to the + intended recipient (human or application) and SHOULD provide some explicit alternate + processing of the stanza (which may be to display a message informing the recipient that it + has received a stanza that cannot be verified).

+ + + +

Timestamps are included to help prevent replay attacks. All timestamps MUST conform to + &DATETIME; and be presented as UTC with no offset, always including the seconds and fractions + of a second to three digits (resulting in a datetime 24 characters in length). Absent a local + adjustment to the sending agent's perceived time or the underlying clock time, the sending + agent MUST ensure that the timestamps it sends to the receiver increase monotonically (if + necessary by incrementing the seconds fraction in the timestamp if the clock returns the same + time for multiple requests). The following rules apply to the receiving application:

+ + + +

The foregoing timestamp checks assume that the recipient is online when the message is + received. However, if the recipient is offline then the server will probably store the message + for delivery when the recipient is next online (offline storage does not apply to <iq/> + or <presence/> stanzas, only <message/> stanzas). As described in &xep0160;, when + sending an offline message to the recipient, the server SHOULD include delayed delivery data + as specified in &xep0203; so that the recipient knows that this is an offline message and also + knows the original time of receipt at the server. In this case, the recipient SHOULD verify + that the timestamp received in the encrypted message is within five minutes of the time + stamped by the recipient's server in the <delay/> element.

+ + + +

All implementations MUST support the following algorithms. Implementations MAY support other + algorithms as well.

+ + + + +

To participate in end-to-end signing using the methods defined in this document, a client + needs to possess an X.509 certificate. It is expected that many clients will generate their + own (self-signed) certificates rather than obtain a certificate issued by a certification + authority (CA). In any case the certificate MUST include an XMPP address that is represented + using the ASN.1 Object Identifier "id-on-xmppAddr" as specified in Section 5.1.1 of + RFC 3920bis.

+ + + +

TBD.

+ + + + +

A URN sub-namespace of signed content for the Extensible Messaging and Presence Protocol + (XMPP) is defined as follows.

+
+ +
URI:
+
urn:xmpp:signed
+ + +
Specification:
+
ProtoXEP
+ + +
Description:
+
This is an XML namespace name of signed content for the Extensible Messaging and + Presence Protocol as defined by ProtoXEP.
+ + +
Registrant Contact:
+
XSF
+ +
+ + + +

This document borrows ideas and text from End-to-End Object Encryption "work in progress" by + Matthew Miller and Peter Saint-Andre.

+ +