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Description of problem:
When Client Hello received by server does not include algorithms known to server, the server signs Server Key Exchange with a sha1+rsa signature algorithm.
Version-Release number of selected component (if applicable):
nss-3.21.0-17.el7.x86_64
How reproducible:
always
Steps to Reproduce:
1. Send Client Hello with invalid values in signature_algorithms extension
Actual results:
Server replies with a SKE message signed with SHA-1
Expected results:
handshake_failure alert message
Additional info:
This is RFC 5246 violation:
If the client does not support the default algorithms (...),
it MUST send the
signature_algorithms extension, listing the algorithms it is willing
to accept.
("default algorithms" refers to sha1+rsa, sha1+dsa and sha1+ecdsa pairs)
If the client has offered the "signature_algorithms" extension, the
signature algorithm and hash algorithm MUST be a pair listed in that
extension. Note that there is a possibility for inconsistencies
here. For instance, the client might offer DHE_DSS key exchange but
omit any DSA pairs from its "signature_algorithms" extension. In
order to negotiate correctly, the server MUST check any candidate
cipher suites against the "signature_algorithms" extension before
selecting them. This is somewhat inelegant but is a compromise
designed to minimize changes to the original cipher suite design.
Comment 2Kai Engert (:kaie) (inactive account)
2017-01-11 14:19:31 UTC
Hubert, can this bug be fixed by upgrading to NSS 3.28 ?
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHEA-2017:1977
Description of problem: When Client Hello received by server does not include algorithms known to server, the server signs Server Key Exchange with a sha1+rsa signature algorithm. Version-Release number of selected component (if applicable): nss-3.21.0-17.el7.x86_64 How reproducible: always Steps to Reproduce: 1. Send Client Hello with invalid values in signature_algorithms extension Actual results: Server replies with a SKE message signed with SHA-1 Expected results: handshake_failure alert message Additional info: This is RFC 5246 violation: If the client does not support the default algorithms (...), it MUST send the signature_algorithms extension, listing the algorithms it is willing to accept. ("default algorithms" refers to sha1+rsa, sha1+dsa and sha1+ecdsa pairs) If the client has offered the "signature_algorithms" extension, the signature algorithm and hash algorithm MUST be a pair listed in that extension. Note that there is a possibility for inconsistencies here. For instance, the client might offer DHE_DSS key exchange but omit any DSA pairs from its "signature_algorithms" extension. In order to negotiate correctly, the server MUST check any candidate cipher suites against the "signature_algorithms" extension before selecting them. This is somewhat inelegant but is a compromise designed to minimize changes to the original cipher suite design.