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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
@@ -22,13 +22,42 @@
# include <string.h>
#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)
{
if (t->th_buf.gnu_longname)
- return t->th_buf.gnu_longname;
+ return safer_name_suffix(t->th_buf.gnu_longname);
/* allocate the th_pathname buffer if not already */
if (t->th_pathname == NULL)
@@ -51,7 +80,7 @@ th_get_pathname(TAR *t)
}
/* will be deallocated in tar_close() */
- return t->th_pathname;
+ return safer_name_suffix(t->th_pathname);
}
--- 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
@@ -21,3 +21,4 @@
#define TLS_THREAD
#endif
+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');
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