dpkg-deb: Do not accept deb packages with data and control members swapped

This is not allowed by the format defined in deb(5), but dpkg-deb has
been very lenient all this time. Enforce the correct format by erroring
out in case of misplaced members.

debian/changelog

@@ -10,6 +10,7 @@ dpkg (1.17.2) UNRELEASED; urgency=low
     does not ship the overlapping paths any more.
   * Automatically prepend needed spaces for continuation --force-help lines.
   * Be more precise on deb format errors with data member in dpkg-deb.
+  * Do not allow deb packages with control and data members swapped.
 
  -- Guillem Jover <guillem@debian.org>  Sun, 28 Jul 2013 15:06:29 +0200
 

dpkg-deb/extract.c

@@ -120,7 +120,7 @@ extracthalf(const char *debar, const char *dir,
   int arfd;
   struct stat stab;
   char nlc;
-  int adminmember;
+  int adminmember = -1;
   bool header_done;
   enum compressor_type decompressor = compressor_type_gzip;
 
@@ -181,6 +181,11 @@ extracthalf(const char *debar, const char *dir,
 	if (strncmp(arh.ar_name, ADMINMEMBER, sizeof(arh.ar_name)) == 0)
 	  adminmember = 1;
 	else {
+          if (adminmember != 1)
+            ohshit(_("archive '%s' has premature member '%.*s' before '%s', "
+                     "giving up"),
+                   debar, (int)sizeof(arh.ar_name), arh.ar_name, ADMINMEMBER);
+
 	  if (strncmp(arh.ar_name, DATAMEMBER, strlen(DATAMEMBER)) == 0) {
 	    const char *extension = arh.ar_name + strlen(DATAMEMBER);