gpg: New option --override-session-key-fd.

* g10/gpg.c (oOverrideSessionKeyFD): New.
(opts): Add option --override-session-key-fd.
(main): Handle that option.
(read_sessionkey_from_fd): New.
--

The override-session-key feature was designed to mitigate the effect
of the British RIP act by allowing to keep the private key private and
hand out only a session key.  For that use case the leaking of the
session key would not be a problem.  However there are other use
cases, for example fast re-decryption after an initial decryption,
which would benefit from concealing the session key from other users.

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

1 files changed, 10 insertions, 6 deletions

diff --git a/doc/gpg.texi b/doc/gpg.texi
index aff3aebbc..c69e512d5 100644
--- a/doc/gpg.texi
+++ b/doc/gpg.texi
@@ -3118,13 +3118,17 @@ inappropriate plaintext so they can take action against the offending
 user.
 
 @item --override-session-key @code{string}
+@itemx --override-session-key-fd @code{fd}
 @opindex override-session-key
-Don't use the public key but the session key @code{string}. The format
-of this string is the same as the one printed by
-@option{--show-session-key}. This option is normally not used but comes
-handy in case someone forces you to reveal the content of an encrypted
-message; using this option you can do this without handing out the
-secret key.
+Don't use the public key but the session key @code{string} respective
+the session key taken from the first line read from file descriptor
+@code{fd}.  The format of this string is the same as the one printed
+by @option{--show-session-key}. This option is normally not used but
+comes handy in case someone forces you to reveal the content of an
+encrypted message; using this option you can do this without handing
+out the secret key.  Note that using @option{--override-session-key}
+may reveal the session key to all local users via the global process
+table.
 
 @item --ask-sig-expire
 @itemx --no-ask-sig-expire