Metadata resource compatibility

[wimlib] / src / resource.c

diff --git a/src/resource.c b/src/resource.c
index 69ccf3844111c70536420bd3ff8c862ee6f432bc..4832030c12adb5c44b90cd429d5deebca6b50098 100644 (file)
--- a/src/resource.c
+++ b/src/resource.c
@@ -1165,6 +1165,12 @@ int read_metadata_resource(WIMStruct *w, struct image_metadata *imd)
                return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
        }
 
+       if (sizeof(size_t) < 8 && metadata_len > 0xffffffff) {
+               ERROR("Metadata resource is too large (%"PRIu64" bytes",
+                     metadata_len);
+               return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
+       }
+
        /* Allocate memory for the uncompressed metadata resource. */
        buf = MALLOC(metadata_len);
 
@@ -1192,14 +1198,18 @@ int read_metadata_resource(WIMStruct *w, struct image_metadata *imd)
         * and if successful, go ahead and calculate the offset in the metadata
         * resource of the root dentry. */
 
+       wimlib_assert(imd->security_data == NULL);
        ret = read_security_data(buf, metadata_len, &imd->security_data);
        if (ret != 0)
                goto out_free_buf;
 
-       get_u32(buf, &dentry_offset);
-       if (dentry_offset == 0)
-               dentry_offset = 8;
-       dentry_offset = (dentry_offset + 7) & ~7;
+       dentry_offset = imd->security_data->total_length + 7 & ~7;
+
+       if (dentry_offset == 0) {
+               ERROR("Integer overflow while reading metadata resource");
+               ret = WIMLIB_ERR_INVALID_SECURITY_DATA;
+               goto out_free_security_data;
+       }
 
        /* Allocate memory for the root dentry and read it into memory */
        dentry = MALLOC(sizeof(struct dentry));
@@ -1278,7 +1288,6 @@ int write_metadata_resource(WIMStruct *w)
        struct lookup_table_entry *lte;
        u64 metadata_original_size;
        const struct wim_security_data *sd;
-       const unsigned random_tail_len = 20;
 
        DEBUG("Writing metadata resource for image %d", w->current_image);
 
@@ -1304,7 +1313,7 @@ int write_metadata_resource(WIMStruct *w)
        calculate_subdir_offsets(root, &subdir_offset);
 
        /* Total length of the metadata resource (uncompressed) */
-       metadata_original_size = subdir_offset + random_tail_len;
+       metadata_original_size = subdir_offset;
 
        /* Allocate a buffer to contain the uncompressed metadata resource */
        buf = MALLOC(metadata_original_size);
@@ -1320,18 +1329,9 @@ int write_metadata_resource(WIMStruct *w)
        /* Write the dentry tree into the resource buffer */
        p = write_dentry_tree(root, p);
 
-       /*
-        * Append 20 random bytes to the metadata resource so that we don't have
-        * identical metadata resources if we happen to append exactly the same
-        * image twice without any changes in timestamps.  If this were to
-        * happen, it would cause confusion about the number and order of images
-        * in the WIM.
-        */
-       randomize_byte_array(p, random_tail_len);
-
        /* We MUST have exactly filled the buffer; otherwise we calculated its
         * size incorrectly or wrote the data incorrectly. */
-       wimlib_assert(p - buf + random_tail_len == metadata_original_size);
+       wimlib_assert(p - buf == metadata_original_size);
 
        /* Get the lookup table entry for the metadata resource so we can update
         * it. */
@@ -1352,14 +1352,17 @@ int write_metadata_resource(WIMStruct *w)
 
        /* It's very likely the SHA1 message digest of the metadata resource
         * changed, so re-insert the lookup table entry into the lookup table.
+        *
+        * We do not check for other lookup table entries having the same SHA1
+        * message digest.  It's possible for 2 absolutely identical images to
+        * be added, therefore causing 2 identical metadata resources to be in
+        * the WIM.  However, in this case, it's expected for 2 separate lookup
+        * table entries to be created, even though this doesn't make a whole
+        * lot of sense since they will share the same SHA1 message digest.
         * */
        lookup_table_unlink(w->lookup_table, lte);
        lookup_table_insert(w->lookup_table, lte);
 
-       /* We do not allow a metadata resource to be referenced multiple times,
-        * and the 20 random bytes appended to it should make it extremely
-        * likely for each metadata resource to be unique, even if the exact
-        * same image is captured. */
        wimlib_assert(lte->out_refcnt == 0);
        lte->out_refcnt = 1;