core: New export mode to export secret subkeys.

* src/gpgme.h.in (GPGME_EXPORT_MODE_SECRET_SUBKEY): New.
* src/export.c (check_mode): Allow new mode and check for invalid
combinations.
(export_keys_start): Return error if new mode flag is set.
* src/engine-gpg.c (export_common): Implement.
* src/gpgme-tool.c (cmd_export): New option --secret-subkey.
* tests/run-export.c (main): New option --secret-subkey.
--

This adds support for exporting secret subkeys (via gpg's
--export-secret-subkeys) to gpgme_op_export[_ext][_start].
The flag is not supported by gpgme_op_export_keys[_start] because
there is no way to specify which subkey(s) to export with these
functions.

GnuPG-bug-id: 5757

1 files changed, 10 insertions, 1 deletions

diff --git a/doc/gpgme.texi b/doc/gpgme.texi
index 8c821989..216d3cde 100644
--- a/doc/gpgme.texi
+++ b/doc/gpgme.texi
@@ -4893,7 +4893,6 @@ OpenPGP key is exported in the OpenSSH public key format.  This
 accepts just a single key; to force the export of a specific subkey
 a fingerprint pattern with an appended exclamation mark may be used.
 
-
 @item GPGME_EXPORT_MODE_SECRET
 @since{1.6.0}
 
@@ -4901,6 +4900,16 @@ Instead of exporting the public key, the secret key is exported.  This
 may not be combined with @code{GPGME_EXPORT_MODE_EXTERN}.  For X.509
 the export format is PKCS#8.
 
+@item GPGME_EXPORT_MODE_SECRET_SUBKEY
+@since{1.17.0}
+
+If this bit is set, then a secret subkey is exported.  The subkey to
+export must be specified with fingerprint pattern with an appended
+exclamation mark.  This is currently only allowed for OpenPGP keys.
+This flag may not be combined with @code{GPGME_EXPORT_MODE_EXTERN}.
+This flag is not supported by the export functions that take an array
+of keys.
+
 @item GPGME_EXPORT_MODE_RAW
 @since{1.6.0}