When merge-recursive creates a unique filename, it uses a
template like:
path~branch_%d
where the final "_%d" is filled by an incrementing counter
until we find a unique name. We allocate 8 characters for
the counter, but there is no logic to limit the size of the
integer.
Of course, this is extremely unlikely, as you would need a
hundred million collisions to trigger the problem. Even if
an attacker constructed a specialized repo, it is unlikely
that the victim would have the patience to run the merge.
However, we can make it trivially correct (and hopefully
more readable) by using a strbuf.
Signed-off-by: Jeff King <p...@peff.net>
---
merge-recursive.c | 41 ++++++++++++++++++++++++++---------------
1 file changed, 26 insertions(+), 15 deletions(-)
diff --git a/merge-recursive.c b/merge-recursive.c
index 532a1da..398a734 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -601,25 +601,36 @@ static int remove_file(struct merge_options *o, int clean,
return 0;
}
+/* add a string to a strbuf, but converting "/" to "_" */
+static void add_flattened_path(struct strbuf *out, const char *s)
+{
+ size_t i = out->len;
+ strbuf_addstr(out, s);
+ for (; i < out->len; i++)
+ if (out->buf[i] == '/')
+ out->buf[i] = '_';
+}
+
static char *unique_path(struct merge_options *o, const char *path, const char
*branch)
{
- char *newpath = xmalloc(strlen(path) + 1 + strlen(branch) + 8 + 1);
+ struct strbuf newpath = STRBUF_INIT;
int suffix = 0;
struct stat st;
- char *p = newpath + strlen(path);
- strcpy(newpath, path);
- *(p++) = '~';
- strcpy(p, branch);
- for (; *p; ++p)
- if ('/' == *p)
- *p = '_';
- while (string_list_has_string(&o->current_file_set, newpath) ||
- string_list_has_string(&o->current_directory_set, newpath) ||
- lstat(newpath, &st) == 0)
- sprintf(p, "_%d", suffix++);
-
- string_list_insert(&o->current_file_set, newpath);
- return newpath;
+ size_t base_len;
+
+ strbuf_addf(&newpath, "%s~", path);
+ add_flattened_path(&newpath, branch);
+
+ base_len = newpath.len;
+ while (string_list_has_string(&o->current_file_set, newpath.buf) ||
+ string_list_has_string(&o->current_directory_set, newpath.buf) ||
+ lstat(newpath.buf, &st) == 0) {
+ strbuf_setlen(&newpath, base_len);
+ strbuf_addf(&newpath, "_%d", suffix++);
+ }
+
+ string_list_insert(&o->current_file_set, newpath.buf);
+ return strbuf_detach(&newpath, NULL);
}
static int dir_in_way(const char *path, int check_working_copy)
--
2.0.0.566.gfe3e6b2
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