gnu: libtar: Fix CVE-2013-4420.

* gnu/packages/compression.scm (libtar)[source]: Add patch.
* gnu/packages/patches/libtar-CVE-2013-4420.patch: New variable.
* gnu/local.mk (dist_patch_DATA): Add it.

This is a follow-up to 89d80159b1.

gnu/local.mk

@@ -588,6 +588,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/libmad-frame-length.patch		\
   %D%/packages/patches/libmad-mips-newgcc.patch			\
   %D%/packages/patches/libssh-0.6.5-CVE-2016-0739.patch		\
+  %D%/packages/patches/libtar-CVE-2013-4420.patch \
   %D%/packages/patches/libtheora-config-guess.patch		\
   %D%/packages/patches/libtiff-CVE-2015-8665+CVE-2015-8683.patch \
   %D%/packages/patches/libtiff-oob-accesses-in-decode.patch	\

gnu/packages/compression.scm

@@ -34,6 +34,7 @@
   #:use-module (guix git-download)
   #:use-module (guix build-system gnu)
   #:use-module (guix build-system perl)
+  #:use-module (gnu packages)
   #:use-module (gnu packages autotools)
   #:use-module (gnu packages backup)
   #:use-module (gnu packages base)
@@ -122,7 +123,8 @@ utility.  Instead of being written in Java, FastJar is written in C.")
                      version ".orig.tar.gz")))
             (sha256
              (base32
-              "02cihzl77ia0dcz7z2cga2412vyhhs5pa2355q4wpwbyga2lrwjh"))))
+              "02cihzl77ia0dcz7z2cga2412vyhhs5pa2355q4wpwbyga2lrwjh"))
+            (patches (search-patches "libtar-CVE-2013-4420.patch"))))
    (build-system gnu-build-system)
    (arguments
     `(#:tests? #f ;no "check" target

gnu/packages/patches/libtar-CVE-2013-4420.patch

@@ -0,0 +1,118 @@
+Author: Raphael Geissert <geissert@debian.org>
+Bug-Debian: https://bugs.debian.org/731860
+Description: Avoid directory traversal when extracting archives 
+ by skipping over leading slashes and any prefix containing ".." components.
+Forwarded: yes
+
+--- a/lib/decode.c
++++ b/lib/decode.c
+@@ -22,6 +22,36 @@
+ #endif
+ 
+ 
++char *
++safer_name_suffix (char const *file_name)
++{
++	char const *p, *t;
++	p = t = file_name;
++	while (*p == '/') t = ++p;
++	while (*p)
++	{
++		while (p[0] == '.' && p[0] == p[1] && p[2] == '/')
++		{
++			p += 3;
++			t = p;
++		}
++		/* advance pointer past the next slash */
++		while (*p && (p++)[0] != '/');
++	}
++
++	if (!*t)
++	{
++		t = ".";
++	}
++
++	if (t != file_name)
++	{
++		/* TODO: warn somehow that the path was modified */
++	}
++	return (char*)t;
++}
++
++
+ /* determine full path name */
+ char *
+ th_get_pathname(TAR *t)
+@@ -29,17 +59,17 @@ th_get_pathname(TAR *t)
+ 	static char filename[MAXPATHLEN];
+ 
+ 	if (t->th_buf.gnu_longname)
+-		return t->th_buf.gnu_longname;
++		return safer_name_suffix(t->th_buf.gnu_longname);
+ 
+ 	if (t->th_buf.prefix[0] != '\0')
+ 	{
+ 		snprintf(filename, sizeof(filename), "%.155s/%.100s",
+ 			 t->th_buf.prefix, t->th_buf.name);
+-		return filename;
++		return safer_name_suffix(filename);
+ 	}
+ 
+ 	snprintf(filename, sizeof(filename), "%.100s", t->th_buf.name);
+-	return filename;
++	return safer_name_suffix(filename);
+ }
+ 
+ 
+--- a/lib/extract.c
++++ b/lib/extract.c
+@@ -298,14 +298,14 @@ tar_extract_hardlink(TAR * t, char *real
+ 	if (mkdirhier(dirname(filename)) == -1)
+ 		return -1;
+ 	libtar_hashptr_reset(&hp);
+-	if (libtar_hash_getkey(t->h, &hp, th_get_linkname(t),
++	if (libtar_hash_getkey(t->h, &hp, safer_name_suffix(th_get_linkname(t)),
+ 			       (libtar_matchfunc_t)libtar_str_match) != 0)
+ 	{
+ 		lnp = (char *)libtar_hashptr_data(&hp);
+ 		linktgt = &lnp[strlen(lnp) + 1];
+ 	}
+ 	else
+-		linktgt = th_get_linkname(t);
++		linktgt = safer_name_suffix(th_get_linkname(t));
+ 
+ #ifdef DEBUG
+ 	printf("  ==> extracting: %s (link to %s)\n", filename, linktgt);
+@@ -343,9 +343,9 @@ tar_extract_symlink(TAR *t, char *realna
+ 
+ #ifdef DEBUG
+ 	printf("  ==> extracting: %s (symlink to %s)\n",
+-	       filename, th_get_linkname(t));
++	       filename, safer_name_suffix(th_get_linkname(t)));
+ #endif
+-	if (symlink(th_get_linkname(t), filename) == -1)
++	if (symlink(safer_name_suffix(th_get_linkname(t)), filename) == -1)
+ 	{
+ #ifdef DEBUG
+ 		perror("symlink()");
+--- a/lib/internal.h
++++ b/lib/internal.h
+@@ -15,3 +15,4 @@
+ 
+ #include <libtar.h>
+ 
++char* safer_name_suffix(char const*);
+--- a/lib/output.c
++++ b/lib/output.c
+@@ -123,9 +123,9 @@ th_print_long_ls(TAR *t)
+ 		else
+ 			printf(" link to ");
+ 		if ((t->options & TAR_GNU) && t->th_buf.gnu_longlink != NULL)
+-			printf("%s", t->th_buf.gnu_longlink);
++			printf("%s", safer_name_suffix(t->th_buf.gnu_longlink));
+ 		else
+-			printf("%.100s", t->th_buf.linkname);
++			printf("%.100s", safer_name_suffix(t->th_buf.linkname));
+ 	}
+ 
+ 	putchar('\n');