ssl sigalg extension: fix NULL pointer dereference
authorPeter Kaestle <>
Mon, 15 Mar 2021 12:19:56 +0000 (13:19 +0100)
committerMatt Caswell <>
Thu, 25 Mar 2021 09:43:33 +0000 (09:43 +0000)
As the variable peer_sigalgslen is not cleared on ssl rehandshake, it's
possible to crash an openssl tls secured server remotely by sending a
manipulated hello message in a rehandshake.

On such a manipulated rehandshake, tls1_set_shared_sigalgs() calls
tls12_shared_sigalgs() with the peer_sigalgslen of the previous
handshake, while the peer_sigalgs has been freed.
As a result tls12_shared_sigalgs() walks over the available
peer_sigalgs and tries to access data of a NULL pointer.

This issue was introduced by c589c34e61 (Add support for the TLS 1.3
signature_algorithms_cert extension, 2018-01-11).

Signed-off-by: Peter Kästle <>
Signed-off-by: Samuel Sapalski <>

CLA: trivial

Reviewed-by: Tomas Mraz <>
Reviewed-by: Paul Dale <>
Reviewed-by: Matt Caswell <>

index b055935d697b9284a34b7fdcc54943e36e68ff8d..4aed508d0f03c533f94b86395ce03a3a17b2b62b 100644 (file)
@@ -1139,6 +1139,7 @@ static int init_sig_algs(SSL *s, unsigned int context)
     /* Clear any signature algorithms extension received */
     s->s3->tmp.peer_sigalgs = NULL;
+    s->s3->tmp.peer_sigalgslen = 0;
     return 1;