Use a fetched MD if appropriate in ssl3_cbc_digest_record

HMACs used via the legacy EVP_DigestSign interface are strange in
that they use legacy codepath's which eventually (under the covers)
transform the operation into a new style EVP_MAC. This can mean the
digest in use can be a legacy one, so we need to be careful with any
digest we extract from the ctx.

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/11511)

1 files changed, 12 insertions, 6 deletions

diff --git a/ssl/s3_cbc.c b/ssl/s3_cbc.c
index 888ff3c2f6..bbc24cc6d1 100644
--- a/ssl/s3_cbc.c
+++ b/ssl/s3_cbc.c
@@ -131,7 +131,8 @@ char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
  * padding too. )
  * Returns 1 on success or 0 on error
  */
-int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
+int ssl3_cbc_digest_record(SSL *s,
+                           const EVP_MD_CTX *ctx,
                            unsigned char *md_out,
                            size_t *md_out_size,
                            const unsigned char header[13],
@@ -166,7 +167,8 @@ int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
      */
     size_t md_length_size = 8;
     char length_is_big_endian = 1;
-    int ret;
+    int ret = 0;
+    const EVP_MD *md = NULL;
 
     /*
      * This is a, hopefully redundant, check that allows us to forget about
@@ -461,7 +463,11 @@ int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
     md_ctx = EVP_MD_CTX_new();
     if (md_ctx == NULL)
         goto err;
-    if (EVP_DigestInit_ex(md_ctx, EVP_MD_CTX_md(ctx), NULL /* engine */ ) <= 0)
+    md = ssl_evp_md_fetch(s->ctx->libctx, EVP_MD_type(EVP_MD_CTX_md(ctx)),
+                          s->ctx->propq);
+    if (md == NULL)
+        goto err;
+    if (EVP_DigestInit_ex(md_ctx, md, NULL /* engine */ ) <= 0)
         goto err;
     if (is_sslv3) {
         /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
@@ -484,10 +490,10 @@ int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
     ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u);
     if (ret && md_out_size)
         *md_out_size = md_out_size_u;
-    EVP_MD_CTX_free(md_ctx);
 
-    return 1;
+    ret = 1;
  err:
     EVP_MD_CTX_free(md_ctx);
-    return 0;
+    ssl_evp_md_free(md);
+    return ret;
 }