Defer sigalgs selection until the certificate is known.

Previously the signature algorithm was selected when the TLS extension was
parsed (or the client received a certificate request), however the actual
certificate to be used is not known at this stage. This leads to various
problems, including the selection of a signature algorithm that cannot be
used with the certificate key size (as found by jeremy@ via ruby regress).

Instead, store the signature algorithms list and only select a signature
algorithm when we're ready to do signature generation.

Joint work with beck@.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/lib/libssl/s3_lib.c b/src/lib/libssl/s3_lib.c
index de928bd70e..49f402d065 100644
--- a/src/lib/libssl/s3_lib.c
+++ b/src/lib/libssl/s3_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_lib.c,v 1.184 2019/02/09 15:26:15 jsing Exp $ */
+/* $OpenBSD: s3_lib.c,v 1.185 2019/03/25 17:21:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1559,6 +1559,7 @@ ssl3_free(SSL *s)
         tls1_cleanup_key_block(s);
         ssl3_release_read_buffer(s);
         ssl3_release_write_buffer(s);
+        freezero(S3I(s)->hs.sigalgs, S3I(s)->hs.sigalgs_len);
 
         DH_free(S3I(s)->tmp.dh);
         EC_KEY_free(S3I(s)->tmp.ecdh);
@@ -1598,6 +1599,9 @@ ssl3_clear(SSL *s)
         S3I(s)->tmp.dh = NULL;
         EC_KEY_free(S3I(s)->tmp.ecdh);
         S3I(s)->tmp.ecdh = NULL;
+        freezero(S3I(s)->hs.sigalgs, S3I(s)->hs.sigalgs_len);
+        S3I(s)->hs.sigalgs = NULL;
+        S3I(s)->hs.sigalgs_len = 0;
 
         freezero(S3I(s)->tmp.x25519, X25519_KEY_LENGTH);
         S3I(s)->tmp.x25519 = NULL;