git-tar-tree: no more void pointer arithmetic

[git.git] / patch-delta.c

diff --git a/patch-delta.c b/patch-delta.c
index a8d75ee..8f318ed 100644 (file)
--- a/patch-delta.c
+++ b/patch-delta.c
@@ -13,76 +13,76 @@
 #include <string.h>
 #include "delta.h"
 
-void *patch_delta(void *src_buf, unsigned long src_size,
-                 void *delta_buf, unsigned long delta_size,
+void *patch_delta(const void *src_buf, unsigned long src_size,
+                 const void *delta_buf, unsigned long delta_size,
                  unsigned long *dst_size)
 {
        const unsigned char *data, *top;
        unsigned char *dst_buf, *out, cmd;
        unsigned long size;
-       int i;
 
-       /* the smallest delta size possible is 6 bytes */
-       if (delta_size < 6)
+       if (delta_size < DELTA_SIZE_MIN)
                return NULL;
 
        data = delta_buf;
        top = delta_buf + delta_size;
 
        /* make sure the orig file size matches what we expect */
-       size = i = 0;
-       cmd = *data++;
-       while (cmd) {
-               if (cmd & 1)
-                       size |= *data++ << i;
-               i += 8;
-               cmd >>= 1;
-       }
+       size = get_delta_hdr_size(&data, top);
        if (size != src_size)
                return NULL;
 
        /* now the result size */
-       size = i = 0;
-       cmd = *data++;
-       while (cmd) {
-               if (cmd & 1)
-                       size |= *data++ << i;
-               i += 8;
-               cmd >>= 1;
-       }
-       dst_buf = malloc(size);
+       size = get_delta_hdr_size(&data, top);
+       dst_buf = malloc(size + 1);
        if (!dst_buf)
                return NULL;
+       dst_buf[size] = 0;
 
        out = dst_buf;
        while (data < top) {
                cmd = *data++;
                if (cmd & 0x80) {
                        unsigned long cp_off = 0, cp_size = 0;
-                       const unsigned char *buf;
                        if (cmd & 0x01) cp_off = *data++;
                        if (cmd & 0x02) cp_off |= (*data++ << 8);
                        if (cmd & 0x04) cp_off |= (*data++ << 16);
                        if (cmd & 0x08) cp_off |= (*data++ << 24);
                        if (cmd & 0x10) cp_size = *data++;
                        if (cmd & 0x20) cp_size |= (*data++ << 8);
+                       if (cmd & 0x40) cp_size |= (*data++ << 16);
                        if (cp_size == 0) cp_size = 0x10000;
-                       buf = (cmd & 0x40) ? dst_buf : src_buf;
-                       memcpy(out, buf + cp_off, cp_size);
+                       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;
 }