gpg: Try hard to use MDC also for sign+symenc.

* g10/encrypt.c (use_mdc): Make it a global func.
* g10/sign.c (sign_symencrypt_file): Use that function to decide
whether to use an MDC.
* tests/openpgp/conventional-mdc.test: Add a simple test case.
--

We used --force-mdc in sign+symenc mode (-cs) only with --force-mdc.
That broke our assumption from commit 625e292 (GnuPG 2.1.9) that all
uses of modern ciphers are using MDC.

Reported-by: Ben Kibbey <bjk@luxsci.net>
Signed-off-by: Werner Koch <wk@gnupg.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/tests/openpgp/conventional-mdc.test b/tests/openpgp/conventional-mdc.test
index 744e11ef3..031fc0e12 100755
--- a/tests/openpgp/conventional-mdc.test
+++ b/tests/openpgp/conventional-mdc.test
@@ -31,5 +31,14 @@ for ciph in `all_cipher_algos`; do
     cmp z y || error "$ciph/$i: mismatch"
   done
 done
-
 progress_end
+
+#info Checking sign+symencrypt
+for i in $plain_files $data_files; do
+    echo "Hier spricht HAL" | $GPG --passphrase-fd 0 $s2k -cs -o x --yes $i
+    echo "Hier spricht HAL" | $GPG --passphrase-fd 0 $s2k     -o y --yes x
+    cmp $i y || error "$i: mismatch in sign+symenc"
+done
+
+
+# eof