CVE-2018-1000300.patch

From 583b42cb3b809b1bf597af160468ccba728c2248 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Fri, 23 Mar 2018 23:30:04 +0100
Subject: [PATCH] pingpong: fix response cache memcpy overflow

Response data for a handle with a large buffer might be cached and then
used with the "closure" handle when it has a smaller buffer and then the
larger cache will be copied and overflow the new smaller heap based
buffer.

Reported-by: Dario Weisser
CVE: CVE-2018-1000300
Bug: https://curl.haxx.se/docs/adv_2018-82c2.html
---
 lib/pingpong.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/pingpong.c b/lib/pingpong.c
index 438856a99..ad370ee82 100644
--- a/lib/pingpong.c
+++ b/lib/pingpong.c
@@ -302,11 +302,14 @@ CURLcode Curl_pp_readresp(curl_socket_t sockfd,
        *
        * pp->cache_size is cast to ssize_t here.  This should be safe, because
        * it would have been populated with something of size int to begin
        * with, even though its datatype may be larger than an int.
        */
-      DEBUGASSERT((ptr + pp->cache_size) <= (buf + data->set.buffer_size + 1));
+      if((ptr + pp->cache_size) > (buf + data->set.buffer_size + 1)) {
+        failf(data, "cached response data too big to handle");
+        return CURLE_RECV_ERROR;
+      }
       memcpy(ptr, pp->cache, pp->cache_size);
       gotbytes = (ssize_t)pp->cache_size;
       free(pp->cache);    /* free the cache */
       pp->cache = NULL;   /* clear the pointer */
       pp->cache_size = 0; /* zero the size just in case */
-- 
2.17.0