[Slirp] [PATCH v2] 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.

Reported-by: Peter Maydell <peter.maydell at linaro.org>
Signed-off-by: Prasad J Pandit <pjp at fedoraproject.org>
---
 src/tftp.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Update v2: add conditional compilation of rules with G_OS_WIN32
  -> https://lists.freedesktop.org/archives/slirp/2020-January/000024.html

diff --git a/src/tftp.c b/src/tftp.c
index 093c2e0..aaca23e 100644
--- a/src/tftp.c
+++ b/src/tftp.c
@@ -344,8 +344,11 @@ 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, "/../")) {
+#ifdef G_OS_WIN32
+    if (strstr(req_fname, "..\\") || req_fname[strlen(req_fname) - 1] == '\\') {
+#else
+    if (strstr(req_fname, "../") || req_fname[strlen(req_fname) - 1] == '/') {
+#endif
         tftp_send_error(spt, 2, "Access violation", tp);
         return;
     }
-- 
2.24.1