On Wed, Mar 16, 2016 at 06:07:43PM +0800, Hui Yiqun wrote:
> + if (runtime_dir && *runtime_dir)
> + git_runtime_dir = mkpathdup("%s/git/", runtime_dir);
> + else
> + git_runtime_dir = mkpathdup("/tmp/git-%d", uid);
Here we allocate the string, but later we may return NULL on error,
leaking the allocated memory.
> + if (!lstat(git_runtime_dir, &st)) {
> + /*
> + * As described in XDG base dir spec[1], the subdirectory
> + * under $XDG_RUNTIME_DIR or its fallback MUST be owned by
> + * the user, and its unix access mode MUST be 0700.
> + *
> + * Calling chmod or chown silently may cause security
> + * problem if somebody chdir to it, sleep, and then, try
> + * to open our protected runtime cache or socket.
> + * So we just put warning and left it to user to solve.
> + *
> + * [1]https://specifications.freedesktop.org/basedir-spec/
> + * basedir-spec-latest.html
> + */
OK. I think these checks should be sufficient to deal with the /tmp race
I mentioned elsewhere in the thread (assuming that an attacker cannot
flip the uid back and forth in the same way, but that should be true on
Unix systems).
> + if ((st.st_mode & 0777) != S_IRWXU) {
> + fprintf(stderr,
> + "permission of runtime directory '%s' "
> + "MUST be 0700 instead of 0%o\n",
> + git_runtime_dir, (st.st_mode & 0777));
> + return NULL;
> + } else if (st.st_uid != uid) {
> + fprintf(stderr,
> + "owner of runtime directory '%s' "
> + "MUST be %d instead of %d\n",
> + git_runtime_dir, uid, st.st_uid);
> + return NULL;
> + }
Should these be using warning(), rather than a raw fprintf?
> + } else {
> + if (safe_create_leading_directories_const(git_runtime_dir) < 0)
> {
> + fprintf(stderr,
> + "unable to create directories for
> '%s'\n",
> + git_runtime_dir);
> + return NULL;
> + }
> + if (mkdir(git_runtime_dir, 0700) < 0) {
> + fprintf(stderr,
> + "unable to mkdir '%s'\n",
> git_runtime_dir);
> + return NULL;
> + }
> + }
And this retains the un-racy mkdir(). Good.
> + free(git_runtime_dir);
> + return mkpathdup("%s/%s", git_runtime_dir, filename);
This mkpathdup accesses the string we just freed?
It might be easier to just use a strbuf here, and then you can append to
it at the end.
-Peff
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