From e1b568dd2462f7cacf98f3d117936c34e2849a6b Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Thu, 26 Feb 2015 11:56:00 +0000 Subject: [PATCH] Prevent handshake with unseeded PRNG Fix security issue where under certain conditions a client can complete a handshake with an unseeded PRNG. The conditions are: - Client is on a platform where the PRNG has not been seeded, and the user has not seeded manually - A protocol specific client method version has been used (i.e. not SSL_client_methodv23) - A ciphersuite is used that does not require additional random data from the PRNG beyond the initial ClientHello client random (e.g. PSK-RC4-SHA) If the handshake succeeds then the client random that has been used will have been generated from a PRNG with insufficient entropy and therefore the output may be predictable. For example using the following command with an unseeded openssl will succeed on an unpatched platform: openssl s_client -psk 1a2b3c4d -tls1_2 -cipher PSK-RC4-SHA CVE-2015-0285 Reviewed-by: Richard Levitte --- ssl/s3_clnt.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c index 1e437b2e1e..750217fff6 100644 --- a/ssl/s3_clnt.c +++ b/ssl/s3_clnt.c @@ -719,8 +719,9 @@ int ssl3_client_hello(SSL *s) } else i = 1; - if (i) - ssl_fill_hello_random(s, 0, p, sizeof(s->s3->client_random)); + if (i && ssl_fill_hello_random(s, 0, p, + sizeof(s->s3->client_random)) <= 0) + goto err; /* Do the message type and length last */ d = p = ssl_handshake_start(s); -- GitLab