gpg: New commands --add-recipients and --change-recipients.

* g10/gpg.c (aAddRecipients, aChangeRecipients): New consts.
(opts): Add --add-recipients and --change-recipients.
(main): Handle them.
* g10/gpg.h (struct server_control_s): Add fields modify_recipients,
clear_recipients, and last_read_ctb.
* g10/armor.c (was_armored): New.
* g10/decrypt.c (decrypt_message): Add optional arg 'remusr'.  Handle
re-encryption if desired.
* g10/encrypt.c (write_pubkey_enc): Factor info printing out to ...
(show_encrypted_for_user_info): new.
(reencrypt_to_new_recipients): New.
* g10/packet.h (struct parse_packet_ctx_s): Add fields only_fookey_enc
and last_ctb.
(init_parse_packet): Clear them.
* g10/parse-packet.c (parse): Store CTB in the context.  Early return
on pubkey_enc and symkey_enc packets if requested.
* g10/mainproc.c (proc_encrypted): Allow for PKT being NULL.  Return
early in modify-recipients mode.
(proc_encryption_packets): Add two optional args 'r_dek' and 'r_list'.
Adjust callers.  Call do_proc_packets in modify-recipients mode
depending on the optional args.
(do_proc_packets): Add arg 'keep_dek_and_list'.  Adjust callers.  Save
the last read CTB in CTRL and return after the last fooenc_enc
packets.
--

This basically works but does not yet handle symmetric encrypted
packets (symkey_enc).

GnuPG-bug-id: 1825
(Yes, this is an at least 9 year old feature request)

1 files changed, 19 insertions, 12 deletions

diff --git a/g10/parse-packet.c b/g10/parse-packet.c
index 8bd283b4b..a16f70fea 100644
--- a/g10/parse-packet.c
+++ b/g10/parse-packet.c
@@ -763,6 +763,7 @@ parse (parse_packet_ctx_t ctx, PACKET *pkt, int onlykeypkts, off_t * retpos,
       rc = -1;
       goto leave;
     }
+  ctx->last_ctb = ctb;
   hdrlen = 0;
   hdr[hdrlen++] = ctb;
 
@@ -774,18 +775,28 @@ parse (parse_packet_ctx_t ctx, PACKET *pkt, int onlykeypkts, off_t * retpos,
     }
 
   /* Immediately following the header is the length.  There are two
-     formats: the old format and the new format.  If bit 6 (where the
-     least significant bit is bit 0) is set in the tag, then we are
-     dealing with a new format packet.  Otherwise, it is an old format
-     packet.  */
+   * formats: the old format and the new format.  If bit 6 (where the
+   * least significant bit is bit 0) is set in the tag, then we are
+   * dealing with a new format packet.  Otherwise, it is an old format
+   * packet.  In the new format the packet's type is encoded in the 6
+   * least significant bits of the tag; in the old format it is
+   * encoded in bits 2-5.  */
   pktlen = 0;
   new_ctb = !!(ctb & 0x40);
   if (new_ctb)
+    pkttype = ctb & 0x3f;
+  else
+    pkttype = (ctb >> 2) & 0xf;
+
+  if (ctx->only_fookey_enc
+      && !(pkttype == PKT_SYMKEY_ENC || pkttype == PKT_PUBKEY_ENC))
     {
-      /* Get the packet's type.  This is encoded in the 6 least
-	 significant bits of the tag.  */
-      pkttype = ctb & 0x3f;
+      rc = gpg_error (GPG_ERR_TRUE);
+      goto leave;
+    }
 
+  if (new_ctb)
+    {
       /* Extract the packet's length.  New format packets have 4 ways
 	 to encode the packet length.  The value of the first byte
 	 determines the encoding and partially determines the length.
@@ -855,12 +866,8 @@ parse (parse_packet_ctx_t ctx, PACKET *pkt, int onlykeypkts, off_t * retpos,
         }
 
     }
-  else
-    /* This is an old format packet.  */
+  else /* This is an old format packet.  */
     {
-      /* Extract the packet's type.  This is encoded in bits 2-5.  */
-      pkttype = (ctb >> 2) & 0xf;
-
       /* The type of length encoding is encoded in bits 0-1 of the
 	 tag.  */
       lenbytes = ((ctb & 3) == 3) ? 0 : (1 << (ctb & 3));