Re: pgg symmetric encryption patch

[Ken Manheimer <ken.manheimer@gmail.com>]

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shit.  the attachment was dropped.  shit.  trying again.  sorry about
the clutter.

On 10/10/05, Ken Manheimer <ken.manheimer@gmail.com> wrote:
> for those of you following the developments at home (:-), here's an
> incremental patch on top of what i sent out a few days ago.  i fixed a
> small stack of bugs in pgg-gpg.el that settles my complaint about
> prompting with the secret key identity, and also filled in a small
> oversight in the changes i sent out a few days ago.
>
> while this could be the last pgg patch, i'm still developing, hence
> the incremental.  i plan to send out a full patch when i've finished
> transitioning allout to pgg, at which point i expect my mucking with
> pgg to be settled.  so, repository maintainers may want to wait for
> that, while i'm hoping those actively involved (eg, sascha) will
> scrutinize and, ideally, exercise these patches.
>
> we'll see if the attached patch makes it through this time.  (i
> haven't re-attached it, which i think was the problem last time.)  if
> not, look forward to a followup...
>
> thanks.
> ken
> ken.manheimer@gmail.com
>
> On 10/8/05, Ken Manheimer <ken.manheimer@gmail.com> wrote:
> > On 10/8/05, Sascha Wilde <wilde@sha-bang.de> wrote:
> > > On Sat, Oct 08, 2005 at 10:48:27AM +0200, Simon Josefsson wrote:
> > > > It seems you are making some progress here.  For simplicity, could you
> > > > post the complete patch (preferably in unified diff format) against
> > > > Emacs CVS you want to have installed?  Unless somebody else has
> > > > already taken care of this...
> > >
> > > I attached the complete patch against the latest cvs checkout.
> >
> > i've got another take on the cumulative patch, with the addition of
> > some refinements i would like to add.
> >
> > the patch is against the gnu.org repository, and incorporates recent
> > checkins there as of a few minutes ago.
> >
> > here are the details of my further refinements, which are included in
> > this patch.   their purpose is to enable external management of the
> > passphrases, including prompting and caching, while still using the
> > pgg encryption and cache mechanisms.  the changes have two thrusts:
> >
> >   - extend the (generic pgg and gpg scheme) encryption and decryption
> >     routines to take an optional passphrase argument, and when provided,
> >     use its value instead of prompting for the passphrase
> >
> >   - extend the passphrase caching and prompting routines to take an optional
> >     'notruncate' argument, to enable caching of passphrases for keys besides
> >     those that have the format of the short pgp packet key id.
> >
> > i think that these, together, will enable me to do the passphrase
> > handling and extend it to symmetric keys, while still leveraging the
> > features of the pgg mechanism (in particular, passphrase expiration).
> > i am pretty sure it's all backwards compatible - all the additional
> > functionality hinges on using the new optional arguments, there should
> > be no operational changes if you don't use them.
> >
> > (i am very puzzled about why the passphrase cache was restricted to
> > the length of the short pgp packet key ids.  seems like you want to
> > couple the passphrases with the user identity for which the message is
> > being encoded, in the case of key-pair ciphers, or some arbitrary
> > string for symmetric ciphers - eg, file name is what i want to use for
> > symmetric keys in allout, since the symmetric keys are associated with
> > the files.  but once again i don't know the pgp territory well enough
> > to wade in, and want to minimize the chance of inadvertantly breaking
> > anything.
> >
> > if this approach is deemed to be fine, i can easily provide an
> > additional patch to adjust the pgg-pgp and pgg-pgp5 modules similarly.
>

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Index: ChangeLog
===================================================================
RCS file: /home/klm/.cvs/aside/src/gnus/ChangeLog,v
retrieving revision 1.5
diff -u -r1.5 ChangeLog
--- ChangeLog	8 Oct 2005 17:58:23 -0000	1.5
+++ ChangeLog	10 Oct 2005 20:56:06 -0000
@@ -1,3 +1,17 @@
+2005-10-15  Ken Manheimer  <ken.manheimer@gmail.com>
+
+	* pgg-gpe.el
+	(pgg-gpg-select-matching-key): fixed: look at the right part of the
+	decoded armor to find the key-identifier
+	(pgg-gpg-lookup-key-owner): new function to return the
+	human-readable identifier of a key owner.
+	(pgg-gpg-decrypt-region): prompt with the key owner (rather
+	than the key value) if we have a key and can match it against a
+	secret key.  also, added an XXX note pointing out fact that the
+	prompt only indicates the first matching key.
+
+	* pgg.el (pgg-decrypt): passing along 'passphrase' in call to
+	pgg-decrypt-region; i overlooked this one in my previous patch.
 
 2005-10-08  Ken Manheimer <ken.manheimer+emacs@gmail.com>
 
Index: pgg-gpg.el
===================================================================
RCS file: /home/klm/.cvs/aside/src/gnus/pgg-gpg.el,v
retrieving revision 1.6
diff -u -r1.6 pgg-gpg.el
--- pgg-gpg.el	8 Oct 2005 17:36:41 -0000	1.6
+++ pgg-gpg.el	10 Oct 2005 20:56:06 -0000
@@ -141,6 +141,24 @@
 			     nil t)
 	  (substring (match-string 2) 8)))))
 
+(defun pgg-gpg-lookup-key-owner (string &optional all)
+  "Search keys associated with STRING and return owner of identified key.
+
+Optional ALL non-nil means search all keys, including secret keys."
+  (let ((args (list "--with-colons" "--no-greeting" "--batch"
+		    (if all "--list-secret-keys" "--list-keys")
+		    string))
+        (key-regexp (concat "^\\(sec\\|pub\\)"
+                            ":[^:]*:[^:]*:[^:]*:\\([^:]*\\):[^:]*"
+                            ":[^:]*:[^:]*:[^:]*:\\([^:]*\\):"))
+        )
+    (with-temp-buffer
+      (apply #'call-process pgg-gpg-program nil t nil args)
+      (goto-char (point-min))
+      (if (re-search-forward key-regexp
+			     nil t)
+          (match-string 3)))))
+
 (defun pgg-gpg-encrypt-region (start end recipients &optional sign passphrase)
   "Encrypt the current region between START and END.
 
@@ -200,8 +218,14 @@
 			 (insert-buffer-substring current-buffer)
 			 (pgg-decode-armor-region (point-min) (point-max))))
 	 (secret-keys (pgg-gpg-lookup-all-secret-keys))
+         ;; XXX the user is stuck if they have the passphrase for the
+         ;;     second or later secret key for which the message is
+         ;;     encrypted.  ideally, we would incrementally give them a
+         ;;     chance with subsequent keys each time they fail with one.
 	 (key (pgg-gpg-select-matching-key message-keys secret-keys))
-	 (pgg-gpg-user-id (or key pgg-gpg-user-id pgg-default-user-id))
+	 (key-owner (and key (pgg-gpg-lookup-key-owner key t)))
+	 (pgg-gpg-user-id (or key-owner key
+	                      pgg-gpg-user-id pgg-default-user-id))
 	 (passphrase (or passphrase
                          (pgg-read-passphrase
                           (format (if (pgg-gpg-symmetric-key-p message-keys)
@@ -217,7 +241,7 @@
       (re-search-forward "^\\[GNUPG:] DECRYPTION_OKAY\\>" nil t))))
 
 (defun pgg-gpg-symmetric-key-p (message-keys)
-  "Check if MESSAGE-KEYS contains a symmetric encryption indicator."
+  "True if decoded armor MESSAGE-KEYS has symmetric encryption indicator."
   (let (result)
     (dolist (key message-keys result)
       (when (and (eq (car key) 3)
@@ -228,7 +252,8 @@
   "Choose a key from MESSAGE-KEYS that matches one of the keys in SECRET-KEYS."
   (loop for message-key in message-keys
 	for message-key-id = (and (equal (car message-key) 1)
-				  (cdr (assq 'key-identifier message-key)))
+				  (cdr (assq 'key-identifier
+                                             (cdr message-key))))
 	for key = (and message-key-id (pgg-lookup-key message-key-id 'encrypt))
 	when (and key (member key secret-keys)) return key))
 

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