1818487 - DTLS1.3 Incorrect transcript computation

Status: RESOLVED FIXED

(NSS :: Libraries, defect, P4)

Description

[Anna Weine]

Copy paste from here: https://bugzilla.mozilla.org/show_bug.cgi?id=1809196#c5

WolfSSL transcript function skips the MessageSequence + Fragment Offset + Fragment Length (Handshake header) fields while computing the transcript, we compute using these fields.

RFC (TLS1.3): This value (transcript one) is computed by hashing the concatenation
of each included handshake message, including the handshake message
header carrying the handshake message type and length fields, but not
including record layer headers.

Could be solved (ugly, i know) by:
the function ssl3_AppendHandshakeInternal (https://searchfox.org/mozilla-central/source/security/nss/lib/ssl/sslencode.c#287)
is responsible (among other things) for uploading the client message to ssl.hs.messages. Instead of the full message living in src (https://searchfox.org/mozilla-central/source/security/nss/lib/ssl/sslencode.c#308), I copy the first 4 bytes (that correspond to HandshakeType and Length), then skip the next 8 bytes (MessageSequence + Fragment Offset + Fragment Length), finally I copy the rest.

Comment 1

[Anna Weine]

Attachment: Bug 1818487 - DTLS1.3 transcript generation

Comment 2

[Anna Weine]

The previous patch manages the modification of the transcript only on the client side, but not the server side.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:beurdouche, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 4

[Anna Weine]

Attachment: Bug 1818487 - Implementation of the test checking ECH with DTLS.

Comment 5

[Anna Weine]

Attachment: Bug 1818487 - Implementation of tests supporting Transcription Generation patch for DTLS1.3

Comment 6

[Anna Weine]

Attachment: Bug 1818487 - Ensuring that DTLS does not use ECH

Comment 7

[Anna Weine]

https://hg.mozilla.org/projects/nss/rev/ee63b00a192e7743326e03aabdf23e6d2d98c7f5
https://hg.mozilla.org/projects/nss/rev/0bef0903c5cb84560cdf076970f0888ff6f0ab0c
https://hg.mozilla.org/projects/nss/rev/305d3d208b3c3761753e614e61a91249382de6b5