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CVE-2021-3634: Create a separate length for session_id

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Normally, the length of session_id and secret_hash is the same,
but if we will get into rekeying with a peer that changes preference
of key exchange algorithm, the new secret hash can be larger or
smaller than the previous session_id causing invalid reads or writes.

Resolves https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35485

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Jakub Jelen
2021-06-23 13:16:33 +02:00
parent a3b2229a4e
commit f5211239f9
10 changed files with 23 additions and 18 deletions
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4
src/messages.c
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@@ -714,8 +714,8 @@ static ssh_buffer ssh_msg_userauth_build_digest(ssh_session session,
rc = ssh_buffer_pack(buffer,
"dPbsssbsS",
crypto->digest_len, /* session ID string */
(size_t)crypto->digest_len, crypto->session_id,
crypto->session_id_len, /* session ID string */
crypto->session_id_len, crypto->session_id,
SSH2_MSG_USERAUTH_REQUEST, /* type */
msg->auth_request.username,
service,