gnu: tcsh: Fix out of bounds read.

* gnu/packages/patches/tcsh-fix-out-of-bounds-read.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/shells.scm (tcsh)[replacement]: New field.
(tcsh/fixed): New variable.

gnu/local.mk

@@ -885,6 +885,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/tclxml-3.2-install.patch			\
   %D%/packages/patches/tcsh-do-not-define-BSDWAIT.patch		\
   %D%/packages/patches/tcsh-fix-autotest.patch			\
+  %D%/packages/patches/tcsh-fix-out-of-bounds-read.patch	\
   %D%/packages/patches/teensy-loader-cli-help.patch		\
   %D%/packages/patches/texi2html-document-encoding.patch	\
   %D%/packages/patches/texi2html-i18n.patch			\

gnu/packages/patches/tcsh-fix-out-of-bounds-read.patch

@@ -0,0 +1,31 @@
+Fix out-of-bounds read in c_substitute():
+
+http://seclists.org/oss-sec/2016/q4/612
+
+Patch copied from upstream source repository:
+
+https://github.com/tcsh-org/tcsh/commit/6a542dc4fb2ba26518a47e9b3a9bcd6a91b94596
+
+From 6a542dc4fb2ba26518a47e9b3a9bcd6a91b94596 Mon Sep 17 00:00:00 2001
+From: christos <christos>
+Date: Fri, 2 Dec 2016 16:59:28 +0000
+Subject: [PATCH] Fix out of bounds read (Brooks Davis) (reproduce by starting
+ tcsh and hitting tab at the prompt)
+
+---
+ ed.chared.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/ed.chared.c b/ed.chared.c
+index 1277e53..310393e 100644
+--- ed.chared.c
++++ ed.chared.c
+@@ -750,7 +750,7 @@ c_substitute(void)
+     /*
+      * If we found a history character, go expand it.
+      */
+-    if (HIST != '\0' && *p == HIST)
++    if (p >= InputBuf && HIST != '\0' && *p == HIST)
+ 	nr_exp = c_excl(p);
+     else
+         nr_exp = 0;

gnu/packages/shells.scm

@@ -174,6 +174,7 @@ has a small feature set similar to a traditional Bourne shell.")
 (define-public tcsh
   (package
     (name "tcsh")
+    (replacement tcsh/fixed)
     (version "6.18.01")
     (source (origin
               (method url-fetch)
@@ -231,6 +232,15 @@ command-line editor, programmable word completion, spelling correction, a
 history mechanism, job control and a C-like syntax.")
     (license bsd-4)))
 
+(define tcsh/fixed
+  (package
+    (inherit tcsh)
+    (name "tcsh")
+    (source (origin
+              (inherit (package-source tcsh))
+              (patches (cons (search-patch "tcsh-fix-out-of-bounds-read.patch")
+                             (origin-patches (package-source tcsh))))))))
+
 (define-public zsh
   (package
     (name "zsh")