don't ever allow SHA1 collisions to exist by fetching a pack

diff --git a/index-pack.c b/index-pack.c
index b405864be954941dedc4b0cc0c7f7aefcf65dd2d..4effb2da6d419a85a6010562de6ac051a35c9ff3 100644 (file)
--- a/index-pack.c
+++ b/index-pack.c
@@ -345,7 +345,8 @@ static int find_delta_children(const union delta_base *base,
 }
 
 static void sha1_object(const void *data, unsigned long size,
-                       enum object_type type, unsigned char *sha1)
+                       enum object_type type, unsigned char *sha1,
+                       int test_for_collision)
 {
        SHA_CTX ctx;
        char header[50];
@@ -367,6 +368,18 @@ static void sha1_object(const void *data, unsigned long size,
        SHA1_Update(&ctx, header, header_size);
        SHA1_Update(&ctx, data, size);
        SHA1_Final(sha1, &ctx);
+
+       if (test_for_collision && has_sha1_file(sha1)) {
+               void *has_data;
+               enum object_type has_type;
+               unsigned long has_size;
+               has_data = read_sha1_file(sha1, &has_type, &has_size);
+               if (!has_data)
+                       die("cannot read existing object %s", sha1_to_hex(sha1));
+               if (size != has_size || type != has_type ||
+                   memcmp(data, has_data, size) != 0)
+                       die("SHA1 COLLISION FOUND WITH %s !", sha1_to_hex(sha1));
+       }
 }
 
 static void resolve_delta(struct object_entry *delta_obj, void *base_data,
@@ -387,7 +400,7 @@ static void resolve_delta(struct object_entry *delta_obj, void *base_data,
        free(delta_data);
        if (!result)
                bad_object(delta_obj->offset, "failed to apply delta");
-       sha1_object(result, result_size, type, delta_obj->sha1);
+       sha1_object(result, result_size, type, delta_obj->sha1, 1);
        nr_resolved_deltas++;
 
        hashcpy(delta_base.sha1, delta_obj->sha1);
@@ -444,7 +457,7 @@ static void parse_pack_objects(unsigned char *sha1)
                        delta->obj_no = i;
                        delta++;
                } else
-                       sha1_object(data, obj->size, obj->type, obj->sha1);
+                       sha1_object(data, obj->size, obj->type, obj->sha1, 1);
                free(data);
                if (verbose)
                        percent = display_progress(i+1, nr_objects, percent);
@@ -565,7 +578,7 @@ static void append_obj_to_pack(void *buf,
        write_or_die(output_fd, header, n);
        obj[1].offset = obj[0].offset + n;
        obj[1].offset += write_compressed(output_fd, buf, size);
-       sha1_object(buf, size, type, obj->sha1);
+       sha1_object(buf, size, type, obj->sha1, 0);
 }
 
 static int delta_pos_compare(const void *_a, const void *_b)