From 7947c50bcd09cf471c95511739bc66d2cb506ee2 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Mon, 6 Nov 2017 23:51:52 +0100
Subject: [PATCH] ntlm: avoid integer overflow for malloc size

Reported-by: Alex Nichols
Assisted-by: Kamil Dudka and Max Dymond

CVE-2017-8816

Bug: https://curl.haxx.se/docs/adv_2017-11e7.html
---
 lib/curl_ntlm_core.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

--- a/lib/curl_ntlm_core.c
+++ b/lib/curl_ntlm_core.c
@@ -618,6 +618,15 @@ CURLcode Curl_hmac_md5(const unsigned ch
   return CURLE_OK;
 }
 
+#ifndef SIZE_T_MAX
+/* some limits.h headers have this defined, some don't */
+#if defined(_LP64) || defined(_I32LPx)
+#define SIZE_T_MAX 18446744073709551615U
+#else
+#define SIZE_T_MAX 4294967295U
+#endif
+#endif
+
 /* This creates the NTLMv2 hash by using NTLM hash as the key and Unicode
  * (uppercase UserName + Domain) as the data
  */
@@ -627,10 +636,20 @@ CURLcode Curl_ntlm_core_mk_ntlmv2_hash(c
                                        unsigned char *ntlmv2hash)
 {
   /* Unicode representation */
-  size_t identity_len = (userlen + domlen) * 2;
-  unsigned char *identity = malloc(identity_len);
+  size_t identity_len;
+  unsigned char *identity;
   CURLcode result = CURLE_OK;
 
+  /* we do the length checks below separately to avoid integer overflow risk
+     on extreme data lengths */
+  if((userlen > SIZE_T_MAX/2) ||
+     (domlen > SIZE_T_MAX/2) ||
+     ((userlen + domlen) > SIZE_T_MAX/2))
+    return CURLE_OUT_OF_MEMORY;
+
+  identity_len = (userlen + domlen) * 2;
+  identity = malloc(identity_len);
+
   if(!identity)
     return CURLE_OUT_OF_MEMORY;
 
