Add sanity check to PRF

The function tls1_PRF counts the number of digests in use and partitions
security evenly between them. There always needs to be at least one digest
in use, otherwise this is an internal error. Add a sanity check for this.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 668f6f08c62177ab5893fc26ebb67053aafdffc8)

diff --git a/ssl/t1_enc.c b/ssl/t1_enc.c
index 84f589606be14d74bf6e816c0c4c7fc7a4847d41..577885fe081e80d809a239994518f9b5b122e551 100644 (file)
--- a/ssl/t1_enc.c
+++ b/ssl/t1_enc.c
@@ -260,6 +260,11 @@ static int tls1_PRF(long digest_mask,
         if ((m << TLS1_PRF_DGST_SHIFT) & digest_mask)
             count++;
     }
+    if(!count) {
+        /* Should never happen */
+        SSLerr(SSL_F_TLS1_PRF, ERR_R_INTERNAL_ERROR);
+        goto err;
+    }
     len = slen / count;
     if (count == 1)
         slen = 0;