*
* @dentry: Dentry to load the alternate data streams into.
* @dentry->num_ads must have been set to the number of
- * data streams that are expected.
+ * alternate data streams that are expected.
*
* @remaining_size: Number of bytes of data remaining in the buffer pointed
* to by @p.
* The format of the on-disk alternate stream entries is as follows:
*
* struct ads_entry_on_disk {
- * u64 length; // Length of the entry, in bytes
+ * u64 length; // Length of the entry, in bytes. This includes
+ * all fields (including the stream name, the
+ * null terminator, AND the padding!).
* u64 reserved; // Seems to be unused
* u8 hash[20]; // SHA1 message digest of the uncompressed stream
* u16 stream_name_len; // Length of the stream name, in bytes
* char stream_name[]; // Stream name in UTF-16LE, @stream_name_len bytes long,
- * // not including null terminator
+ * not including null terminator
* u16 zero; // UTF-16 null terminator for the stream name, NOT
- * // included in @stream_name_len
+ * included in @stream_name_len
+ * char padding[]; // Padding to make the size a multiple of 8 bytes.
* };
*
* In addition, the entries are 8-byte aligned.
for (u16 i = 0; i < num_ads; i++) {
struct ads_entry *cur_entry = &ads_entries[i];
u64 length;
+ u64 length_no_padding;
+ u64 total_length;
size_t utf8_len;
const char *p_save = p;
ret = WIMLIB_ERR_INVALID_DENTRY;
goto out_free_ads_entries;
}
- remaining_size -= WIM_ADS_ENTRY_DISK_SIZE;
- p = get_u64(p, &length); /* ADS entry length */
- p += 8; /* Unused */
+ p = get_u64(p, &length);
+ p += 8;
p = get_bytes(p, SHA1_HASH_SIZE, (u8*)cur_entry->hash);
p = get_u16(p, &cur_entry->stream_name_len);
cur_entry->stream_name = NULL;
cur_entry->stream_name_utf8 = NULL;
- if (remaining_size < cur_entry->stream_name_len + 2) {
+ /* Length including neither the null terminator nor the padding
+ * */
+ length_no_padding = WIM_ADS_ENTRY_DISK_SIZE +
+ cur_entry->stream_name_len;
+ total_length = ((length_no_padding + 2) + 7) & ~7;
+
+ wimlib_assert(total_length == ads_entry_total_length(cur_entry));
+
+ if (remaining_size < length_no_padding) {
ERROR("Stream entries go past end of metadata resource");
- ERROR("(remaining_size = %"PRIu64" bytes, stream_name_len "
- "= %"PRIu16" bytes", remaining_size,
- cur_entry->stream_name_len);
+ ERROR("(remaining_size = %"PRIu64" bytes, "
+ "length_no_padding = %"PRIu16" bytes",
+ remaining_size, length_no_padding);
+ ret = WIMLIB_ERR_INVALID_DENTRY;
+ goto out_free_ads_entries;
+ }
+
+ /* The @length field in the on-disk ADS entry is expected to be
+ * equal to @total_length, which includes all of the entry and
+ * the padding that follows it to align the next ADS entry to an
+ * 8-byte boundary. However, to be safe, we'll accept the
+ * length field as long as it's not less than the un-padded
+ * total length and not more than the padded total length. */
+ if (length < length_no_padding || length > total_length) {
+ ERROR("Stream entry has unexpected length "
+ "field (length field = %"PRIu64", "
+ "unpadded total length = %"PRIu64", "
+ "padded total length = %"PRIu64")",
+ length, length_no_padding, total_length);
ret = WIMLIB_ERR_INVALID_DENTRY;
goto out_free_ads_entries;
}
- remaining_size -= cur_entry->stream_name_len + 2;
cur_entry->stream_name = MALLOC(cur_entry->stream_name_len);
if (!cur_entry->stream_name) {
ret = WIMLIB_ERR_NOMEM;
goto out_free_ads_entries;
}
- p = p_save + ads_entry_total_length(cur_entry);
+ /* It's expected that the size of every ADS entry is a multiple
+ * of 8. However, to be safe, I'm allowing the possibility of
+ * an ADS entry at the very end of the metadata resource ending
+ * un-aligned. So although we still need to increment the input
+ * pointer by @total_length to reach the next ADS entry, it's
+ * possible that less than @total_length is actually remaining
+ * in the metadata resource. We should set the remaining size to
+ * 0 bytes if this happens. */
+ p = p_save + total_length;
+ if (remaining_size < total_length)
+ remaining_size = 0;
+ else
+ remaining_size -= total_length;
}
dentry->ads_entries = ads_entries;
return 0;
git://wimlib.net / wimlib / blobdiff