[Slirp] [PATCH v3] slirp: tftp: restrict relative path access

[P J P]

From: Prasad J Pandit <pjp at fedoraproject.org>

tftp restricts relative or directory path access on Linux systems.
Apply same restrictions on Windows systems too. It helps to avoid
directory traversal issue.

Fixes: https://bugs.launchpad.net/qemu/+bug/1812451
Reported-by: Peter Maydell <peter.maydell at linaro.org>
Signed-off-by: Prasad J Pandit <pjp at fedoraproject.org>
---
 src/tftp.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Update v3: use #ifdef mid-if-expression
  -> https://lists.freedesktop.org/archives/slirp/2020-January/000047.html

diff --git a/src/tftp.c b/src/tftp.c
index 093c2e0..ebb80b5 100644
--- a/src/tftp.c
+++ b/src/tftp.c
@@ -344,8 +344,13 @@ static void tftp_handle_rrq(Slirp *slirp, struct sockaddr_storage *srcsas,
     k += 6; /* skipping octet */
 
     /* do sanity checks on the filename */
-    if (!strncmp(req_fname, "../", 3) ||
-        req_fname[strlen(req_fname) - 1] == '/' || strstr(req_fname, "/../")) {
+    if (
+#ifdef G_OS_WIN32
+        strstr(req_fname, "..\\")
+        || req_fname[strlen(req_fname) - 1] == '\\' ||
+#endif
+        strstr(req_fname, "../")
+        || req_fname[strlen(req_fname) - 1] == '/') {
         tftp_send_error(spt, 2, "Access violation", tp);
         return;
     }
-- 
2.24.1