core: New flags GPGME_DECRYPT_UNWRAP and GPGME_ENCRYPT_WRAP.

* src/gpgme.h.in (GPGME_ENCRYPT_WRAP): New const.
(gpgme_decrypt_flags_t): New enum.
(GPGME_DECRYPT_VERIFY): New const
(GPGME_DECRYPT_UNWRAP): New const
(gpgme_op_decrypt_ext_start): New func.
(gpgme_op_decrypt_ext): New func.
* src/decrypt-verify.c (gpgme_op_decrypt_ext_start): New.
(gpgme_op_decrypt_ext): New.
(decrypt_verify_start): Add arg FLAGS.  Replace call to
engine_op_decrypt_verify by the plain decrypt with the flag set.
(gpgme_op_decrypt_verify_start): Pass the flag.
(gpgme_op_decrypt_verify): Pass the flag.
* src/decrypt.c (decrypt_start): Rename to ...
(_gpgme_decrypt_start): this.  Add arg FLAGS.  Pass FLAGS to
engine_op_decrypt.
(gpgme_op_decrypt_start): Adjust for chnage pass 0 for FLAG.
(gpgme_op_decrypt_start): Ditto.
* src/engine.c (_gpgme_engine_op_decrypt_verify): Remove.
(_gpgme_engine_op_decrypt): Add arg FLAGS.
* src/gpgme.def, src/libgpgme.vers: Add new functions.
* src/engine-backend.h (struct engine_ops): Remove member
'decrypt_verify'.  Add FLAGS to 'decrypt'.  Adjust all initialization.
* src/engine-uiserver.c (uiserver_decrypt): Remove.
(uiserver_decrypt_verify): Remove.
(_uiserver_decrypt): Rename to ...
(uiserver_decrypt): this.  Replace arg VERIFY by new arg FLAGS.
* src/engine-gpg.c (gpg_decrypt): Support GPGME_DECRYPT_UNWRAP.
(gpg_encrypt): Support GPGME_ENCRYPT_WRAP.

* tests/run-decrypt.c (main): New option --unwrap.
* tests/run-encrypt.c (main): New option --wrap.
--

Manual testing of that wrap/unwrap feature can be done this way:

 ./run-encrypt --verbose --key Alice /etc/motd > x
 ./run-decrypt --verbose --unwrap x > y
 ./run-encrypt --verbose --key Bob --wrap y > z

1. The message was first encrypted to Alice.
2. Alice decrypts the message receiving a valid OpenPGP message.
3. Alice encrypt that message to Bob

This will also work with encrypted and signed messages; the signature
will be kept intact during re-encryption.  Requires GnuPG 2.1.12.

Signed-off-by: Werner Koch <[email protected]>

1 files changed, 22 insertions, 2 deletions

diff --git a/src/engine-gpg.c b/src/engine-gpg.c
index 6e4b8339..0c3a63ee 100644
--- a/src/engine-gpg.c
+++ b/src/engine-gpg.c
@@ -1559,7 +1559,9 @@ add_input_size_hint (engine_gpg_t gpg, gpgme_data_t data)
 
 
 static gpgme_error_t
-gpg_decrypt (void *engine, gpgme_data_t ciph, gpgme_data_t plain,
+gpg_decrypt (void *engine,
+             gpgme_decrypt_flags_t flags,
+             gpgme_data_t ciph, gpgme_data_t plain,
              int export_session_key, const char *override_session_key)
 {
   engine_gpg_t gpg = engine;
@@ -1567,6 +1569,14 @@ gpg_decrypt (void *engine, gpgme_data_t ciph, gpgme_data_t plain,
 
   err = add_arg (gpg, "--decrypt");
 
+  if (!err && (flags & GPGME_DECRYPT_UNWRAP))
+    {
+      if (!have_gpg_version (gpg, "2.1.12"))
+        err = gpg_error (GPG_ERR_NOT_SUPPORTED);
+      else
+        err = add_arg (gpg, "--unwrap");
+    }
+
   if (!err && export_session_key)
     err = add_arg (gpg, "--show-session-key");
 
@@ -1857,6 +1867,17 @@ gpg_encrypt (void *engine, gpgme_key_t recp[], gpgme_encrypt_flags_t flags,
   if (!err && use_armor)
     err = add_arg (gpg, "--armor");
 
+  if (!err && (flags & GPGME_ENCRYPT_WRAP))
+    {
+      /* gpg is current not abale to detect already compressed
+       * packets.  Thus when using
+       *   gpg --unwrap -d | gpg --no-literal -e
+       * the encryption would add an additional compression layer.
+       * We better suppress that.  */
+      flags |= GPGME_ENCRYPT_NO_COMPRESS;
+      err = add_arg (gpg, "--no-literal");
+    }
+
   if (!err && (flags & GPGME_ENCRYPT_NO_COMPRESS))
     err = add_arg (gpg, "--compress-algo=none");
 
@@ -3047,7 +3068,6 @@ struct engine_ops _gpgme_engine_ops_gpg =
     gpg_set_locale,
     NULL,				/* set_protocol */
     gpg_decrypt,
-    gpg_decrypt,			/* decrypt_verify */
     gpg_delete,
     gpg_edit,
     gpg_encrypt,