From 358b2b131ad6c095696f20dcfa62b8305263f898 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Tue, 1 Aug 2017 17:16:46 +0200
Subject: [PATCH] tftp: reject file name lengths that don't fit

... and thereby avoid telling send() to send off more bytes than the
size of the buffer!

CVE-2017-1000100

Bug: https://curl.haxx.se/docs/adv_20170809B.html
Reported-by: Even Rouault

Credit to OSS-Fuzz for the discovery
---
 lib/tftp.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/tftp.c b/lib/tftp.c
index 02bd84242..f6f4bce5b 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -3,11 +3,11 @@
  *  Project                     ___| | | |  _ \| |
  *                             / __| | | | |_) | |
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
  * are also available at https://curl.haxx.se/docs/copyright.html.
  *
@@ -489,10 +489,15 @@ static CURLcode tftp_send_first(tftp_state_data_t *state, tftp_event_t event)
     result = Curl_urldecode(data, &state->conn->data->state.path[1], 0,
                             &filename, NULL, FALSE);
     if(result)
       return result;
 
+    if(strlen(filename) > (state->blksize - strlen(mode) - 4)) {
+      failf(data, "TFTP file name too long\n");
+      return CURLE_TFTP_ILLEGAL; /* too long file name field */
+    }
+
     snprintf((char *)state->spacket.data+2,
              state->blksize,
              "%s%c%s%c", filename, '\0',  mode, '\0');
     sbytes = 4 + strlen(filename) + strlen(mode);
 
-- 
2.13.3