Add sanity check of tar "uid, "gid" and "mtime" fields

Sometimes a bz2 file is identified as tar.bz2, i.e. a chunk of
raw data may look like a tar header (metadata block).
To reduce chance of such false positive, the format of uid, gid
and mtime field is checked. This fields are expected to contain
octal numbers. In fact, also space and '\0' are allowed - perhaps
I am too liberal.

diff --git a/libarchive/archive_read_support_format_tar.c b/libarchive/archive_read_support_format_tar.c
index 469666e8e5eb2d5a679c9a14b1baa4fc0e5b8d43..0625c1f36895f985a89f582cff8d4f5d403e05b9 100644 (file)
--- a/libarchive/archive_read_support_format_tar.c
+++ b/libarchive/archive_read_support_format_tar.c
@@ -362,7 +362,26 @@ archive_read_format_tar_bid(struct archive_read *a, int best_bid)
                /* Not a valid mode; bail out here. */
                return (0);
        }
-       /* TODO: Sanity test uid/gid/size/mtime/rdevmajor/rdevminor fields. */
+
+       /* Sanity test uid/gid/mtime fields must hold octal numbers. */
+       size_t i;
+       for (i = 0; i < sizeof(header->gid); ++i) {
+               char c = header->gid[i];
+               if (c != ' ' && c != '\0' && (c < '0' || c > '7'))
+                       return 0;
+       }
+       for (i = 0; i < sizeof(header->uid); ++i) {
+               char c = header->uid[i];
+               if (c != ' ' && c != '\0' && (c < '0' || c > '7'))
+                       return 0;
+       }
+       for (i = 0; i < sizeof(header->mtime); ++i) {
+               char c = header->mtime[i];
+               if (c != ' ' && c != '\0' && (c < '0' || c > '7'))
+                       return 0;
+       }
+
+       /* TODO: Sanity test size/rdevmajor/rdevminor fields. */
 
        return (bid);
 }