Add ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS option

This fixes a directory traversal in the cpio tool.
libarchive · Mar 4, 2015 · 5935715 · 5935715
1 parent fc04ba0
commit 5935715
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Showing 6 changed files with 43 additions and 4 deletions.
diff --git a/cpio/bsdcpio.1 b/cpio/bsdcpio.1
@@ -156,7 +156,8 @@ See above for description.
 .It Fl Fl insecure
 (i and p mode only)
 Disable security checks during extraction or copying.
-This allows extraction via symbolic links and path names containing
+This allows extraction via symbolic links, absolute paths,
+and path names containing
 .Sq ..
 in the name.
 .It Fl J , Fl Fl xz

diff --git a/cpio/cpio.c b/cpio/cpio.c
@@ -171,6 +171,7 @@ main(int argc, char *argv[])
 	cpio->extract_flags |= ARCHIVE_EXTRACT_NO_OVERWRITE_NEWER;
 	cpio->extract_flags |= ARCHIVE_EXTRACT_SECURE_SYMLINKS;
 	cpio->extract_flags |= ARCHIVE_EXTRACT_SECURE_NODOTDOT;
+	cpio->extract_flags |= ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS;
 	cpio->extract_flags |= ARCHIVE_EXTRACT_PERM;
 	cpio->extract_flags |= ARCHIVE_EXTRACT_FFLAGS;
 	cpio->extract_flags |= ARCHIVE_EXTRACT_ACL;
@@ -256,6 +257,7 @@ main(int argc, char *argv[])
 		case OPTION_INSECURE:
 			cpio->extract_flags &= ~ARCHIVE_EXTRACT_SECURE_SYMLINKS;
 			cpio->extract_flags &= ~ARCHIVE_EXTRACT_SECURE_NODOTDOT;
+			cpio->extract_flags &= ~ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS;
 			break;
 		case 'L': /* GNU cpio */
 			cpio->option_follow_links = 1;

diff --git a/libarchive/archive.h b/libarchive/archive.h
@@ -649,6 +649,8 @@ __LA_DECL int archive_read_set_passphrase_callback(struct archive *,
 /* Default: Do not use HFS+ compression if it was not compressed. */
 /* This has no effect except on Mac OS v10.6 or later. */
 #define	ARCHIVE_EXTRACT_HFS_COMPRESSION_FORCED	(0x8000)
+/* Default: Do not reject entries with absolute paths */
+#define ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS (0x10000)
 
 __LA_DECL int archive_read_extract(struct archive *, struct archive_entry *,
 		     int flags);

diff --git a/libarchive/archive_write_disk.3 b/libarchive/archive_write_disk.3
@@ -177,6 +177,9 @@ The default is to not refuse such paths.
 Note that paths ending in
 .Pa ..
 always cause an error, regardless of this flag.
+.It Cm ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS
+Refuse to extract an absolute path.
+The default is to not refuse such paths.
 .It Cm ARCHIVE_EXTRACT_SPARSE
 Scan data for blocks of NUL bytes and try to recreate them with holes.
 This results in sparse files, independent of whether the archive format

diff --git a/libarchive/archive_write_disk_posix.c b/libarchive/archive_write_disk_posix.c
@@ -2509,8 +2509,9 @@ cleanup_pathname_win(struct archive_write_disk *a)
 /*
  * Canonicalize the pathname.  In particular, this strips duplicate
  * '/' characters, '.' elements, and trailing '/'.  It also raises an
- * error for an empty path, a trailing '..' or (if _SECURE_NODOTDOT is
- * set) any '..' in the path.
+ * error for an empty path, a trailing '..', (if _SECURE_NODOTDOT is
+ * set) any '..' in the path or (if ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS
+ * is set) if the path is absolute.
  */
 static int
 cleanup_pathname(struct archive_write_disk *a)
@@ -2529,8 +2530,15 @@ cleanup_pathname(struct archive_write_disk *a)
 	cleanup_pathname_win(a);
 #endif
 	/* Skip leading '/'. */
-	if (*src == '/')
+	if (*src == '/') {
+		if (a->flags & ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS) {
+			archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC,
+			                  "Path is absolute");
+			return (ARCHIVE_FAILED);
+		}
+
 		separator = *src++;
+	}
 
 	/* Scan the pathname one element at a time. */
 	for (;;) {

diff --git a/libarchive/test/test_write_disk_secure.c b/libarchive/test/test_write_disk_secure.c
@@ -178,6 +178,29 @@ DEFINE_TEST(test_write_disk_secure)
 	assert(S_ISDIR(st.st_mode));
 	archive_entry_free(ae);
 
+	/*
+	 * Without security checks, we should be able to
+	 * extract an absolute path.
+	 */
+	assert((ae = archive_entry_new()) != NULL);
+	archive_entry_copy_pathname(ae, "/tmp/libarchive_test-test_write_disk_secure-absolute_path.tmp");
+	archive_entry_set_mode(ae, S_IFREG | 0777);
+	assert(0 == archive_write_header(a, ae));
+	assert(0 == archive_write_finish_entry(a));
+	assertFileExists("/tmp/libarchive_test-test_write_disk_secure-absolute_path.tmp");
+	assert(0 == unlink("/tmp/libarchive_test-test_write_disk_secure-absolute_path.tmp"));
+
+	/* But with security checks enabled, this should fail. */
+	assert(archive_entry_clear(ae) != NULL);
+	archive_entry_copy_pathname(ae, "/tmp/libarchive_test-test_write_disk_secure-absolute_path.tmp");
+	archive_entry_set_mode(ae, S_IFREG | 0777);
+	archive_write_disk_set_options(a, ARCHIVE_EXTRACT_SECURE_NOABSOLUTEPATHS);
+	failure("Extracting an absolute path should fail here.");
+	assertEqualInt(ARCHIVE_FAILED, archive_write_header(a, ae));
+	archive_entry_free(ae);
+	assert(0 == archive_write_finish_entry(a));
+	assertFileNotExists("/tmp/libarchive_test-test_write_disk_secure-absolute_path.tmp");
+
 	assertEqualInt(ARCHIVE_OK, archive_write_free(a));
 
 	/* Test the entries on disk. */