Re: [PATCH] daemon: sanitize all directory separators

Hi Junio & René,

On Thu, 25 Mar 2021, Junio C Hamano wrote:

René Scharfe. [off-list ref] writes:

quoted

When sanitizing client-supplied strings on Windows, also strip off
backslashes, not just slashes.

Signed-off-by: René Scharfe <redacted>
---
 daemon.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

I do not know how common is it to run "git daemon" on Windows, but
it would be nice to have at least an ack from Windows person.

Here is my ACK.

I do not have any precise numbers, of course, as we do not have any
telemetry in Git for Windows (for better or worse).

There _are_ occasional reports about something in `git daemon` not
working; Most notably, you have to turn off the sideband to make `push`
work.

quoted

diff --git a/daemon.c b/daemon.c
index 2ab7ea82eb..0561c19ee8 100644
--- a/daemon.c
+++ b/daemon.c

@@ -566,14 +566,14 @@ static void parse_host_and_port(char *hostport, char **host,

 /*
  * Sanitize a string from the client so that it's OK to be inserted into a
- * filesystem path. Specifically, we disallow slashes, runs of "..", and
- * trailing and leading dots, which means that the client cannot escape
- * our base path via ".." traversal.
+ * filesystem path. Specifically, we disallow directory separators, runs
+ * of "..", and trailing and leading dots, which means that the client
+ * cannot escape our base path via ".." traversal.

Not a new problem, but "runs of '..'" confused me.  If I am reading
the code right, we disallow directory separators (by ignoring) and
two or more '.' in a row (by squashing them into a single '.').

Indeed, the code is a bit funny in that respect. But at least it keeps us
somewhat safe: there is currently no way to break out of the directory to
the parent directory, whether with this path or not. (Phew!)

Thanks,
Dscho

quoted

  */
 static void sanitize_client(struct strbuf *out, const char *in)
 {
 	for (; *in; in++) {
-		if (*in == '/')
+		if (is_dir_sep(*in))
 			continue;
 		if (*in == '.' && (!out->len || out->buf[out->len - 1] == '.'))
 			continue;
--
2.30.2

Thanks.