gpg: Hard fail on a missing MDC even for legacy algorithms.

* g10/mainproc.c (proc_encrypted): Require an MDC or AEAD
* tests/openpgp/defs.scm (create-gpghome): Use --ignore-mdc-error to
allow testing with the current files.

Signed-off-by: Werner Koch <wk@gnupg.org>

1 files changed, 6 insertions, 9 deletions

diff --git a/g10/mainproc.c b/g10/mainproc.c
index ea3721a4f..a991203ea 100644
--- a/g10/mainproc.c
+++ b/g10/mainproc.c
@@ -738,15 +738,12 @@ proc_encrypted (CTX c, PACKET *pkt)
   else if (!result
            && !opt.ignore_mdc_error
            && !pkt->pkt.encrypted->mdc_method
-           && !pkt->pkt.encrypted->aead_algo
-           && openpgp_cipher_get_algo_blklen (c->dek->algo) != 8
-           && c->dek->algo != CIPHER_ALGO_TWOFISH)
-    {
-      /* The message has been decrypted but has no MDC despite that a
-         modern cipher (blocklength != 64 bit, except for Twofish) is
-         used and the option to ignore MDC errors is not used: To
-         avoid attacks changing an MDC message to a non-MDC message,
-         we fail here.  */
+           && !pkt->pkt.encrypted->aead_algo)
+    {
+      /* The message has been decrypted but does not carry an MDC or
+       * uses AEAD encryption.  --ignore-mdc-error has also not been
+       * used.  To avoid attacks changing an MDC message to a non-MDC
+       * message, we fail here.  */
       log_error (_("WARNING: message was not integrity protected\n"));
       if (opt.verbose > 1)
         log_info ("decryption forced to fail\n");