dtach: fix CVE-2012-3368

pkgs/tools/misc/dtach/default.nix

@@ -8,6 +8,8 @@ stdenv.mkDerivation rec {
     sha256 = "16614ebddf8ab2811d3dc0e7f329c7de88929ac6a9632d4cb4aef7fe11b8f2a9";
   };
 
+  patches = [ ./fix-CVE-2012-3368.patch ];
+
   installPhase = ''
     mkdir -p $out/bin
     cp dtach $out/bin/dtach

pkgs/tools/misc/dtach/fix-CVE-2012-3368.patch

@@ -0,0 +1,49 @@
+Fix error handling for read from stdin in attach.c
+
+attach.c did not correctly handle a read from stdin when read returned
+an error. The code assigned the return value of read to pkt.len (an
+unsigned char) before checking the value. This prevented the error check
+from working correctly, since an unsigned integer can never be < 0.
+
+A packet with an invalid length was then sent to the master, which then
+sent 255 bytes of garbage to the program.
+
+Fix the bug in attach.c and the unchecked packet length bug in master.c.
+
+Report and initial patch by Enrico Scholz.
+
+--- a/master.c	2012/07/01 21:26:10	1.14
++++ b/master.c	2012/07/01 21:44:34	1.15
+@@ -351,7 +351,10 @@
+ 
+ 	/* Push out data to the program. */
+ 	if (pkt.type == MSG_PUSH)
+-		write(the_pty.fd, pkt.u.buf, pkt.len);
++	{
++		if (pkt.len <= sizeof(pkt.u.buf))
++			write(the_pty.fd, pkt.u.buf, pkt.len);
++	}
+ 
+ 	/* Attach or detach from the program. */
+ 	else if (pkt.type == MSG_ATTACH)
+--- a/attach.c	2012/07/01 21:26:10	1.12
++++ b/attach.c	2012/07/01 21:44:34	1.13
+@@ -237,12 +237,16 @@
+ 		/* stdin activity */
+ 		if (n > 0 && FD_ISSET(0, &readfds))
+ 		{
++			ssize_t len;
++
+ 			pkt.type = MSG_PUSH;
+ 			memset(pkt.u.buf, 0, sizeof(pkt.u.buf));
+-			pkt.len = read(0, pkt.u.buf, sizeof(pkt.u.buf));
++			len = read(0, pkt.u.buf, sizeof(pkt.u.buf));
+ 
+-			if (pkt.len <= 0)
++			if (len <= 0)
+ 				exit(1);
++
++			pkt.len = len;
+ 			process_kbd(s, &pkt);
+ 			n--;
+ 		}