X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/99dbdcf461adff82b2fe68c9c9c690c4982969b1..1d28cc061677bd07d9bed48dd84bd5c590247043:/src/src/auths/spa.c

diff --git a/src/src/auths/spa.c b/src/src/auths/spa.c
index e7a588dd2..222ccea86 100644
--- a/src/src/auths/spa.c
+++ b/src/src/auths/spa.c
@@ -5,6 +5,7 @@
 /* Copyright (c) University of Cambridge 1995 - 2018 */
 /* Copyright (c) The Exim Maintainers 2020 */
 /* See the file NOTICE for conditions of use and distribution. */
+/* SPDX-License-Identifier: GPL-2.0-or-later */
 
 /* This file, which provides support for Microsoft's Secure Password
 Authentication, was contributed by Marc Prud'hommeaux. Tom Kistner added SPA
@@ -140,7 +141,8 @@ SPAAuthChallenge challenge;
 SPAAuthResponse  response;
 SPAAuthResponse  *responseptr = &response;
 uschar msgbuf[2048];
-uschar *clearpass;
+uschar *clearpass, *s;
+unsigned off;
 
 /* send a 334, MS Exchange style, and grab the client's request,
 unless we already have it via an initial response. */
@@ -187,9 +189,19 @@ that causes failure if the size of msgbuf is exceeded. ****/
 
   {
   int i;
-  char * p = (CS responseptr) + IVAL(&responseptr->uUser.offset,0);
+  char * p;
   int len = SVAL(&responseptr->uUser.len,0)/2;
 
+  if (  (off = IVAL(&responseptr->uUser.offset,0)) >= sizeof(SPAAuthResponse)
+     || len >= sizeof(responseptr->buffer)/2
+     || (p = (CS responseptr) + off) + len*2 >= CS (responseptr+1)
+     )
+    {
+    DEBUG(D_auth)
+      debug_printf("auth_spa_server(): bad uUser spec in response\n");
+    return FAIL;
+    }
+
   if (len + 1 >= sizeof(msgbuf)) return FAIL;
   for (i = 0; i < len; ++i)
     {
@@ -235,8 +247,16 @@ spa_smb_nt_encrypt(clearpass, challenge.challengeData, ntRespData);
 
 /* compare NT hash (LM may not be available) */
 
-if (memcmp(ntRespData, (US responseptr)+IVAL(&responseptr->ntResponse.offset,0),
-      24) == 0)
+off = IVAL(&responseptr->ntResponse.offset,0);
+if (off >= sizeof(SPAAuthResponse) - 24)
+  {
+  DEBUG(D_auth)
+    debug_printf("auth_spa_server(): bad ntRespData spec in response\n");
+  return FAIL;
+  }
+s = (US responseptr) + off;
+
+if (memcmp(ntRespData, s, 24) == 0)
   return auth_check_serv_cond(ablock);	/* success. we have a winner. */
 
   /* Expand server_condition as an authorization check (PH) */