Re: [PATCH] daemon: detect and reject too-long paths
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Oct 22, 2016, 16:37 UTC
- Message-ID
- <xmqqzilw8hn0.fsf@gitster.mtv.corp.google.com>
- In-Reply-To
- <20161022045938.h3xa3yapzlg427vy@sigill.intra.peff.net>
Jeff King <peff@peff.net> writes:
Show 10 quoted lines
> When we are checking the path via path_ok(), we use some > fixed PATH_MAX buffers. We write into them via snprintf(), > so there's no possibility of overflow, but it does mean we > may silently truncate the path, leading to potentially > confusing errors when the partial path does not exist. > > We're better off to reject the path explicitly. > > Signed-off-by: Jeff King <peff@peff.net> > ---
Sounds sensible.
Show 6 quoted lines
> Another option would be to switch to strbufs here. That potentially > introduces cases where a client can convince us to just keep allocating > memory, but I don't think so in practice; the paths and interpolated > data items all have to come in 64K pkt-lines, which places a hard > limit. This is a much more minimal change, though, and I don't hear > anybody complaining about the inability to use large paths.
The alternative version did not look bad, either; in fact, the end result may even be conceptually simpler.
But I agree that this one with the same hard-limit we always had is a much more minimal change and is sufficient.
Thanks.
Show 59 quoted lines
> daemon.c | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/daemon.c b/daemon.c
> index 425aad0507..ff0fa583b0 100644
> --- a/daemon.c
> +++ b/daemon.c
> @@ -160,6 +160,7 @@ static const char *path_ok(const char *directory, struct hostinfo *hi)
> {
> static char rpath[PATH_MAX];
> static char interp_path[PATH_MAX];
> + size_t rlen;
> const char *path;
> const char *dir;
>
> @@ -187,8 +188,12 @@ static const char *path_ok(const char *directory, struct hostinfo *hi)
> namlen = slash - dir;
> restlen -= namlen;
> loginfo("userpath <%s>, request <%s>, namlen %d, restlen %d, slash <%s>", user_path, dir, namlen, restlen, slash);
> - snprintf(rpath, PATH_MAX, "%.*s/%s%.*s",
> - namlen, dir, user_path, restlen, slash);
> + rlen = snprintf(rpath, sizeof(rpath), "%.*s/%s%.*s",
> + namlen, dir, user_path, restlen, slash);
> + if (rlen >= sizeof(rpath)) {
> + logerror("user-path too large: %s", rpath);
> + return NULL;
> + }
> dir = rpath;
> }
> }
> @@ -207,7 +212,15 @@ static const char *path_ok(const char *directory, struct hostinfo *hi)
>
> strbuf_expand(&expanded_path, interpolated_path,
> expand_path, &context);
> - strlcpy(interp_path, expanded_path.buf, PATH_MAX);
> +
> + rlen = strlcpy(interp_path, expanded_path.buf,
> + sizeof(interp_path));
> + if (rlen >= sizeof(interp_path)) {
> + logerror("interpolated path too large: %s",
> + interp_path);
> + return NULL;
> + }
> +
> strbuf_release(&expanded_path);
> loginfo("Interpolated dir '%s'", interp_path);
>
> @@ -219,7 +232,11 @@ static const char *path_ok(const char *directory, struct hostinfo *hi)
> logerror("'%s': Non-absolute path denied (base-path active)", dir);
> return NULL;
> }
> - snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
> + rlen = snprintf(rpath, sizeof(rpath), "%s%s", base_path, dir);
> + if (rlen >= sizeof(rpath)) {
> + logerror("base-path too large: %s", rpath);
> + return NULL;
> + }
> dir = rpath;
> }