Avoid potential NULL pointer function calls in n_ssl3_mac() by checking

the return value of EVP_MD_CTX_copy_ex(). If the copy fails early then
EVP_DigestUpdate() will invoke md_ctx.update(), which will be a NULL
function pointer.

Analysis and patch from David Ramos.

ok deraadt@

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/libssl/src/ssl/s3_enc.c b/src/lib/libssl/src/ssl/s3_enc.c
index f4ac5222f3..13ba633f49 100644
--- a/src/lib/libssl/src/ssl/s3_enc.c
+++ b/src/lib/libssl/src/ssl/s3_enc.c
@@ -762,7 +762,8 @@ n_ssl3_mac(SSL *ssl, unsigned char *md, int send)
                 /* Chop the digest off the end :-) */
                 EVP_MD_CTX_init(&md_ctx);
 
-                EVP_MD_CTX_copy_ex(&md_ctx, hash);
+                if (!EVP_MD_CTX_copy_ex(&md_ctx, hash))
+                        return (-1);
                 EVP_DigestUpdate(&md_ctx, mac_sec, md_size);
                 EVP_DigestUpdate(&md_ctx, ssl3_pad_1, npad);
                 EVP_DigestUpdate(&md_ctx, seq, 8);
@@ -774,7 +775,8 @@ n_ssl3_mac(SSL *ssl, unsigned char *md, int send)
                 EVP_DigestUpdate(&md_ctx, rec->input, rec->length);
                 EVP_DigestFinal_ex(&md_ctx, md, NULL);
 
-                EVP_MD_CTX_copy_ex(&md_ctx, hash);
+                if (!EVP_MD_CTX_copy_ex(&md_ctx, hash))
+                        return (-1);
                 EVP_DigestUpdate(&md_ctx, mac_sec, md_size);
                 EVP_DigestUpdate(&md_ctx, ssl3_pad_2, npad);
                 EVP_DigestUpdate(&md_ctx, md, md_size);