gnu: rxvt-unicode: Disable an unwanted code execution vector.

* gnu/packages/patches/rxvt-unicode-escape-sequences.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/xdisorg.scm (rxvt-unicode)[source]: Use it.

gnu/local.mk

@@ -972,6 +972,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/ruby-puma-ignore-broken-test.patch       \
   %D%/packages/patches/ruby-rack-ignore-failing-test.patch      \
   %D%/packages/patches/ruby-tzinfo-data-ignore-broken-test.patch\
+  %D%/packages/patches/rxvt-unicode-escape-sequences.patch	\
   %D%/packages/patches/scheme48-tests.patch			\
   %D%/packages/patches/scotch-test-threading.patch		\
   %D%/packages/patches/screen-fix-info-syntax-error.patch	\

gnu/packages/patches/rxvt-unicode-escape-sequences.patch

@@ -0,0 +1,35 @@
+This patch prevents a code execution vector involving terminal escape
+sequences when rxvt-unicode is in "secure mode".
+
+This change was spurred by the following conversation on the
+oss-security mailing list:
+
+Problem description and proof of concept:
+http://seclists.org/oss-sec/2017/q2/190
+
+Upstream response:
+http://seclists.org/oss-sec/2017/q2/291
+
+Patch copied from upstream source repository:
+http://cvs.schmorp.de/rxvt-unicode/src/command.C?r1=1.582&r2=1.583
+
+--- rxvt-unicode/src/command.C	2016/07/14 05:33:26	1.582
++++ rxvt-unicode/src/command.C	2017/05/18 02:43:18	1.583
+@@ -2695,7 +2695,7 @@
+         /* kidnapped escape sequence: Should be 8.3.48 */
+       case C1_ESA:		/* ESC G */
+         // used by original rxvt for rob nations own graphics mode
+-        if (cmd_getc () == 'Q')
++        if (cmd_getc () == 'Q' && option (Opt_insecure))
+           tt_printf ("\033G0\012");	/* query graphics - no graphics */
+         break;
+ 
+@@ -2914,7 +2914,7 @@
+         break;
+ 
+       case CSI_CUB:		/* 8.3.18: (1) CURSOR LEFT */
+-      case CSI_HPB: 		/* 8.3.59: (1) CHARACTER POSITION BACKWARD */
++      case CSI_HPB:		/* 8.3.59: (1) CHARACTER POSITION BACKWARD */
+ #ifdef ISO6429
+         arg[0] = -arg[0];
+ #else				/* emulate common DEC VTs */

gnu/packages/xdisorg.scm

@@ -682,6 +682,7 @@ (define-public rxvt-unicode
               (method url-fetch)
               (uri (string-append "http://dist.schmorp.de/rxvt-unicode/Attic/"
                                   name "-" version ".tar.bz2"))
+              (patches (search-patches "rxvt-unicode-escape-sequences.patch"))
               (sha256
                (base32
                 "1pddjn5ynblwfrdmskylrsxb9vfnk3w4jdnq2l8xn2pspkljhip9"))))