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-rw-r--r--patch-delta.c26
1 files changed, 21 insertions, 5 deletions
diff --git a/patch-delta.c b/patch-delta.c
index c0e1311435..d95f0d9721 100644
--- a/patch-delta.c
+++ b/patch-delta.c
@@ -28,12 +28,12 @@ void *patch_delta(void *src_buf, unsigned long src_size,
         top = delta_buf + delta_size;
 
         /* make sure the orig file size matches what we expect */
-        size = get_delta_hdr_size(&data);
+        size = get_delta_hdr_size(&data, top);
         if (size != src_size)
                 return NULL;
 
         /* now the result size */
-        size = get_delta_hdr_size(&data);
+        size = get_delta_hdr_size(&data, top);
         dst_buf = malloc(size + 1);
         if (!dst_buf)
                 return NULL;
@@ -52,21 +52,37 @@ void *patch_delta(void *src_buf, unsigned long src_size,
                         if (cmd & 0x20) cp_size |= (*data++ << 8);
                         if (cmd & 0x40) cp_size |= (*data++ << 16);
                         if (cp_size == 0) cp_size = 0x10000;
+                        if (cp_off + cp_size < cp_size ||
+                            cp_off + cp_size > src_size ||
+                            cp_size > size)
+                                goto bad;
                         memcpy(out, src_buf + cp_off, cp_size);
                         out += cp_size;
-                } else {
+                        size -= cp_size;
+                } else if (cmd) {
+                        if (cmd > size)
+                                goto bad;
                         memcpy(out, data, cmd);
                         out += cmd;
                         data += cmd;
+                        size -= cmd;
+                } else {
+                        /*
+                         * cmd == 0 is reserved for future encoding
+                         * extensions. In the mean time we must fail when
+                         * encountering them (might be data corruption).
+                         */
+                        goto bad;
                 }
         }
 
         /* sanity check */
-        if (data != top || out - dst_buf != size) {
+        if (data != top || size != 0) {
+                bad:
                 free(dst_buf);
                 return NULL;
         }
 
-        *dst_size = size;
+        *dst_size = out - dst_buf;
         return dst_buf;
 }