[PATCH] allow weirdly-mixed pkcs7 signatures

[Daniel Kahn Gillmor]

* tools/gpgparsemail.c: add and check info->signing_protocol_2

Some mailers in the wild will generate messages that have the a weird
structure where they use the x- prefix in one part and drop it in
another.

For example, the main MIME part as a whole has:

Content-Type: multipart/signed;
   protocol="application/x-pkcs7-signature"

but the signature sub-part has:

  Content-Type: application/pkcs7-signature

(or vice versa, where the x- prefix is in the sub-part but not the
protocol= section on the main MIME object)

This change also avoids allocating strings for these comparisons,
since the const strings in question are already available in the built
executable, and no dynamic labels are needed.
---
 tools/gpgparsemail.c | 40 +++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/tools/gpgparsemail.c b/tools/gpgparsemail.c
index 98bbad0..fc449c3 100644
--- a/tools/gpgparsemail.c
+++ b/tools/gpgparsemail.c
@@ -67,7 +67,9 @@ struct parse_info_s {
   int smfm_state;              /* State of PGP/MIME or S/MIME parsing.  */
   int is_smime;                /* This is S/MIME and not PGP/MIME. */
 
-  char *signing_protocol;
+  const char *signing_protocol;
+  const char *signing_protocol_2; /* there are two ways to present
+                                     PKCS7 */
   int hashing_level;           /* The nesting level we are hashing. */
   int hashing;
   FILE *hash_file;
@@ -139,15 +141,15 @@ xmalloc (size_t n)
 /*   return p; */
 /* } */
 
-static char *
-xstrdup (const char *string)
-{
-  void *p = malloc (strlen (string)+1);
-  if (!p)
-    die ("out of core: %s", strerror (errno));
-  strcpy (p, string);
-  return p;
-}
+/* static char * */
+/* xstrdup (const char *string) */
+/* { */
+/*   void *p = malloc (strlen (string)+1); */
+/*   if (!p) */
+/*     die ("out of core: %s", strerror (errno)); */
+/*   strcpy (p, string); */
+/*   return p; */
+/* } */
 
 #ifndef HAVE_STPCPY
 static char *
@@ -364,8 +366,8 @@ mime_signed_begin (struct parse_info_s *info, rfc822parse_t msg,
             {
               info->smfm_state = 1;
               info->is_smime = 0;
-              free (info->signing_protocol);
-              info->signing_protocol = xstrdup (s);
+              info->signing_protocol = "application/pgp-signature";
+              info->signing_protocol_2 = NULL;
             }
         }
       else if (!strcmp (s, "application/pkcs7-signature")
@@ -377,8 +379,8 @@ mime_signed_begin (struct parse_info_s *info, rfc822parse_t msg,
             {
               info->smfm_state = 1;
               info->is_smime = 1;
-              free (info->signing_protocol);
-              info->signing_protocol = xstrdup (s);
+              info->signing_protocol = "application/pkcs7-signature";
+              info->signing_protocol_2 = "application/x-pkcs7-signature";
             }
         }
       else if (verbose)
@@ -516,10 +518,14 @@ message_cb (void *opaque, rfc822parse_event_t event, rfc822parse_t msg)
                   char *buf = xmalloc (strlen (s1) + strlen (s2) + 2);
                   strcpy (stpcpy (stpcpy (buf, s1), "/"), s2);
                   assert (info->signing_protocol);
-                  if (strcmp (buf, info->signing_protocol))
-                    err ("invalid %s structure; expected '%s', found '%s'",
+                  if (strcmp (buf, info->signing_protocol) &&
+                      (!info->signing_protocol_2 || strcmp (buf,info->signing_protocol_2)))
+                    err ("invalid %s structure; expected %s%s%s, found '%s'",
                          info->is_smime? "S/MIME":"PGP/MIME",
-                         info->signing_protocol, buf);
+                         info->signing_protocol,
+                         info->signing_protocol_2 ? " or " : "",
+                         info->signing_protocol_2 ? info->signing_protocol_2 : "",
+                         buf);
                   else
                     {
                       printf ("c begin_signature\n");
-- 
2.7.0