commit 329e78c7fa7bd3d10a4b4bd937a773560801749e
author Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Mon Jun 26 12:22:17 2017 +0200
committer Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Tue Aug 08 11:06:49 2017 +0200
tree 8ecd65c1af2225ba933a305d59c540b51f9c6090
parent a4a206e834f576e3c7d242d5354995b80c466326

Improve handling of md errors in X.509

md() already checks for md_info == NULL. Also, in the future it might also
return other errors (eg hardware errors if acceleration is used), so it make
more sense to check its return value than to check for NULL ourselves and then
assume no other error can occur.

Also, currently, md_info == NULL can never happen except if the MD and OID modules
get out of sync, or if the user messes with members of the x509_crt structure
directly.

This commit does not change the current behaviour, which is to treat MD errors
the same way as a bad signature or no trusted root.

library/x509_crt.c

diff --git a/library/x509_crt.c b/library/x509_crt.c
index c6209fb..1adf8bf 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1675,17 +1675,13 @@
             flags |= MBEDTLS_X509_BADCRL_BAD_PK;
 
         md_info = mbedtls_md_info_from_type( crl_list->sig_md );
-        if( md_info == NULL )
+        if( mbedtls_md( md_info, crl_list->tbs.p, crl_list->tbs.len, hash ) != 0 )
         {
-            /*
-             * Cannot check 'unknown' hash
-             */
+            /* Note: this can't happen except after an internal error */
             flags |= MBEDTLS_X509_BADCRL_NOT_TRUSTED;
             break;
         }
 
-        mbedtls_md( md_info, crl_list->tbs.p, crl_list->tbs.len, hash );
-
         if( x509_profile_check_key( profile, crl_list->sig_pk, &ca->pk ) != 0 )
             flags |= MBEDTLS_X509_BADCERT_BAD_KEY;
 
@@ -1930,15 +1926,12 @@
     *flags |= MBEDTLS_X509_BADCERT_NOT_TRUSTED;
 
     md_info = mbedtls_md_info_from_type( child->sig_md );
-    if( md_info == NULL )
+    if( mbedtls_md( md_info, child->tbs.p, child->tbs.len, hash ) != 0 )
     {
-        /*
-         * Cannot check 'unknown', no need to try any CA
-         */
+        /* Note: this can't happen except after an internal error */
+        /* Cannot check signature, no need to try any CA */
         trust_ca = NULL;
     }
-    else
-        mbedtls_md( md_info, child->tbs.p, child->tbs.len, hash );
 
     for( /* trust_ca */ ; trust_ca != NULL; trust_ca = trust_ca->next )
     {