From d81a1600588b726c2bdccda7efad3cc7a87d6245 Mon Sep 17 00:00:00 2001 From: Viktor Dukhovni Date: Wed, 30 Dec 2015 22:44:51 -0500 Subject: [PATCH] Better SSLv2 cipher-suite enforcement Based on patch by: Nimrod Aviram CVE-2015-3197 Reviewed-by: Tim Hudson Reviewed-by: Richard Levitte --- ssl/s2_srvr.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/ssl/s2_srvr.c b/ssl/s2_srvr.c index 5e2e0acc35..07e9df8282 100644 --- a/ssl/s2_srvr.c +++ b/ssl/s2_srvr.c @@ -402,7 +402,7 @@ static int get_client_master_key(SSL *s) } cp = ssl2_get_cipher_by_char(p); - if (cp == NULL) { + if (cp == NULL || sk_SSL_CIPHER_find(s->session->ciphers, cp) < 0) { ssl2_return_error(s, SSL2_PE_NO_CIPHER); SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, SSL_R_NO_CIPHER_MATCH); return (-1); @@ -692,8 +692,12 @@ static int get_client_hello(SSL *s) prio = cs; allow = cl; } + + /* Generate list of SSLv2 ciphers shared between client and server */ for (z = 0; z < sk_SSL_CIPHER_num(prio); z++) { - if (sk_SSL_CIPHER_find(allow, sk_SSL_CIPHER_value(prio, z)) < 0) { + const SSL_CIPHER *cp = sk_SSL_CIPHER_value(prio, z); + if ((cp->algorithm_ssl & SSL_SSLV2) == 0 || + sk_SSL_CIPHER_find(allow, cp) < 0) { (void)sk_SSL_CIPHER_delete(prio, z); z--; } @@ -702,6 +706,13 @@ static int get_client_hello(SSL *s) sk_SSL_CIPHER_free(s->session->ciphers); s->session->ciphers = prio; } + + /* Make sure we have at least one cipher in common */ + if (sk_SSL_CIPHER_num(s->session->ciphers) == 0) { + ssl2_return_error(s, SSL2_PE_NO_CIPHER); + SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_NO_CIPHER_MATCH); + return -1; + } /* * s->session->ciphers should now have a list of ciphers that are on * both the client and server. This list is ordered by the order the -- 2.25.1