Re: Small patch to enable use of gpg-agent with pgg

[Simon Josefsson <jas@extundo.com>]

Sascha Wilde <wilde@sha-bang.de> writes:

> Hi,
>
> I wrote a small patch, which makes it possible to use the GnuPG agent
> (which is part of gpg 1.9 and considered ready to use by Werner) with
> the GnuPG backend of pgg.
>
> I have done very little testing yet, but it seems to work fine.[0]
>
> To test it: 
> set up your gpg-agent as usual and set pgg-gpg-use-agent to t.

Your patch didn't work well for me:

1) Non-agent mode didn't work at all (the args list contained 'nil' so
   invoking gpg failed with a lisp error).

2) After fixing the above, the patch made the passphrase be 't', which
   broke the passphrase cache, causing a lisp error.

How about this patch instead?  It works for me.  I've also improved
the pgg-use-agent default value.  I've installed this on Emacs CVS
trunk, Gnus v5-10 and Gnus CVS.

Thanks for working on this, it is quite useful.

--- pgg-gpg.el	21 Mar 2006 14:53:00 +0100	1.4
+++ pgg-gpg.el	21 Mar 2006 15:22:38 +0100	
@@ -51,6 +51,13 @@
   :type '(choice (const :tag "New `--recipient' option" "--recipient")
 		 (const :tag "Old `--remote-user' option" "--remote-user")))
 
+(defcustom pgg-gpg-use-agent (if (getenv "GPG_AGENT_INFO") t nil)
+  "Whether to use gnupg agent for key caching.
+By default, it will be enabled iff the environment variable
+\"GPG_AGENT_INFO\" is set."
+  :group 'pgg-gpg
+  :type 'boolean)
+
 (defvar pgg-gpg-user-id nil
   "GnuPG ID of your default identity.")
 
@@ -58,7 +65,8 @@
   (let* ((output-file-name (pgg-make-temp-file "pgg-output"))
 	 (args
 	  `("--status-fd" "2"
-	    ,@(if passphrase '("--passphrase-fd" "0"))
+	    ,@(if pgg-gpg-use-agent '("--use-agent")
+		(if passphrase '("--passphrase-fd" "0")))
 	    "--yes" ; overwrite
 	    "--output" ,output-file-name
 	    ,@pgg-gpg-extra-args ,@args))
@@ -100,7 +108,8 @@
       (set-default-file-modes orig-mode))))
 
 (defun pgg-gpg-possibly-cache-passphrase (passphrase &optional key notruncate)
-  (if (and pgg-cache-passphrase
+  (if (and passphrase
+	   pgg-cache-passphrase
 	   (progn
 	     (goto-char (point-min))
 	     (re-search-forward "^\\[GNUPG:] \\(GOOD_PASSPHRASE\\>\\)\\|\\(SIG_CREATED\\)" nil t)))
@@ -182,7 +191,7 @@
 passphrase cache or user."
   (let* ((pgg-gpg-user-id (or pgg-gpg-user-id pgg-default-user-id))
 	 (passphrase (or passphrase
-                         (when sign
+			 (when (and sign (not pgg-gpg-use-agent))
                            (pgg-read-passphrase
                             (format "GnuPG passphrase for %s: "
                                     pgg-gpg-user-id)
@@ -214,8 +223,9 @@
 If optional PASSPHRASE is not specified, it will be obtained from the
 passphrase cache or user."
   (let* ((passphrase (or passphrase
+			 (when (not pgg-gpg-use-agent)
                          (pgg-read-passphrase
-                          "GnuPG passphrase for symmetric encryption: ")))
+			    "GnuPG passphrase for symmetric encryption: "))))
 	 (args
 	  (append (list "--batch" "--armor" "--symmetric" )
 		  (if pgg-text-mode (list "--textmode")))))
@@ -242,12 +252,13 @@
 	 (pgg-gpg-user-id (or key-id key
 	                      pgg-gpg-user-id pgg-default-user-id))
 	 (passphrase (or passphrase
+			 (when (not pgg-gpg-use-agent)
                          (pgg-read-passphrase
                           (format (if (pgg-gpg-symmetric-key-p message-keys)
                                       "Passphrase for symmetric decryption: "
                                     "GnuPG passphrase for %s: ")
                                   (or key-owner "??"))
-                          pgg-gpg-user-id)))
+			    pgg-gpg-user-id))))
 	 (args '("--batch" "--decrypt")))
     (pgg-gpg-process-region start end passphrase pgg-gpg-program args)
     (with-current-buffer pgg-errors-buffer
@@ -277,9 +288,11 @@
   "Make detached signature from text between START and END."
   (let* ((pgg-gpg-user-id (or pgg-gpg-user-id pgg-default-user-id))
 	 (passphrase (or passphrase
+			 (when (not pgg-gpg-use-agent)
                          (pgg-read-passphrase
-                          (format "GnuPG passphrase for %s: " pgg-gpg-user-id)
-                          pgg-gpg-user-id)))
+			    (format "GnuPG passphrase for %s: "
+				    pgg-gpg-user-id)
+			    pgg-gpg-user-id))))
 	 (args
 	  (append (list (if cleartext "--clearsign" "--detach-sign")
 			"--armor" "--batch" "--verbose"