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Date: Fri, 6 Dec 2019 05:25:10 +0000
From: VMware Security Response Center <security@...are.com>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
CC: VMware Security Response Center <security@...are.com>
Subject: CVE-2019-5544 openslp 1.2.1, 2.0.0 heap overflow vulnerability

openslp has a heap overflow vulnerability that when exploited may result
in memory corruption and a crash of slpd or in remote code execution.

CVE-2019-5544 has been assigned to this issue.

Below you may find:
- a copy of the affected code with comments indicating the problem.
- patches for openslp versions 1.2.1 and 2.0.0

VMware would like to thank the 360Vulcan team working with the 2019
Tianfu Cup Pwn Contest for reporting this issue to us.

VMware Security Response Center


============================== CODE SNIPPET ============================

slpd_process.c

static int ProcessSrvRqst(SLPMessage * message, SLPBuffer * sendbuf,
      int errorcode)
{
   ...
   if (db && errorcode == 0)
   {
      for (i = 0; i < db->urlcount; i++)
      {
         /* urlentry is the url from the db result */
         urlentry = db->urlarray[i];

         size += urlentry->urllen + 6; /*  1 byte for reserved  *///<=======================================(1)here size plus urllen
                                       /*  2 bytes for lifetime */
                                       /*  2 bytes for urllen   */
                                       /*  1 byte for authcount */
#ifdef ENABLE_SLPv2_SECURITY
         /* make room to include the authblock that was asked for */
         if (G_SlpdProperty.securityEnabled
               && message->body.srvrqst.spistrlen)
         {
            for (j = 0; j < urlentry->authcount; j++)
            {
               if (SLPCompareString(urlentry->autharray[j].spistrlen,
                     urlentry->autharray[j].spistr,
                     message->body.srvrqst.spistrlen,
                     message->body.srvrqst.spistr) == 0)
               {
                  authblock = &(urlentry->autharray[j]);
                  size += authblock->length;
                  break;
               }
            }
         }
#endif
      }
   }

   /* reallocate the result buffer */
   result = SLPBufferRealloc(result, size);//<======================================(2)here use size to malloc a buffer
   if (result == 0)
   {
      errorcode = SLP_ERROR_INTERNAL_ERROR;
      goto FINISHED;
   }

   /* add the header */

   /* version */
   *result->curpos++ = 2;

   /* function id */
   *result->curpos++ = SLP_FUNCT_SRVRPLY;

   /* length */
   PutUINT24(&result->curpos, size);

   /* flags */
   PutUINT16(&result->curpos, (size > (size_t)G_SlpdProperty.MTU?
         SLP_FLAG_OVERFLOW: 0));

   /* ext offset */
   PutUINT24(&result->curpos, 0);

   /* xid */
   PutUINT16(&result->curpos, message->header.xid);

   /* lang tag len */
   PutUINT16(&result->curpos, message->header.langtaglen);

   /* lang tag */
   memcpy(result->curpos, message->header.langtag,
         message->header.langtaglen);
   result->curpos += message->header.langtaglen;

   /* add rest of the SrvRply */

   /* error code*/
   PutUINT16(&result->curpos, errorcode);
   if (db && errorcode == 0)
   {
      /* urlentry count */
      PutUINT16(&result->curpos, db->urlcount);
      for (i = 0; i < db->urlcount; i++)
      {
         /* urlentry is the url from the db result */
         urlentry = db->urlarray[i];

#ifdef ENABLE_SLPv1
         if (urlentry->opaque == 0)
         {
            /* url-entry reserved */
            *result->curpos++ = 0;

            /* url-entry lifetime */
            PutUINT16(&result->curpos, urlentry->lifetime);

            /* url-entry urllen */
            PutUINT16(&result->curpos, urlentry->urllen);

            /* url-entry url */
            memcpy(result->curpos, urlentry->url, urlentry->urllen);
            result->curpos += urlentry->urllen;

            /* url-entry auths */
            *result->curpos++ = 0;
         }
         else
#endif
         {
            /* Use an opaque copy if available (and authentication is
             * not being used).
             */

            /* TRICKY: Fix up the lifetime. */
            TO_UINT16(urlentry->opaque + 1, urlentry->lifetime);
            memcpy(result->curpos, urlentry->opaque, urlentry->opaquelen);//<==================================(3)opaquelen could be bigger than urllen,lead to heap overflow
            result->curpos += urlentry->opaquelen;
         }
      }
   }
   else
      PutUINT16(&result->curpos, 0); /* set urlentry count to 0*/

FINISHED:

   if (db)
      SLPDDatabaseSrvRqstEnd(db);

   *sendbuf = result;

   return errorcode;
}     

============================== /CODE SNIPPET ============================


============================== PATCH FOR OPENSLP 1.2.1 ============================

diff -ur openslp-1.2.1.orig/common/slp_buffer.c openslp-1.2.1/common/slp_buffer.c
--- openslp-1.2.1.orig/common/slp_buffer.c	2005-02-07 21:32:58.000000000 -0800
+++ openslp-1.2.1/common/slp_buffer.c	2019-11-26 21:58:26.000000000 -0800
@@ -47,6 +47,12 @@
 /*                                                                         */
 /***************************************************************************/
 
+/* Copyright (c) 2019 VMware, Inc.
+ * SPDX-License-Identifier: BSD-3-Clause
+ * This file is provided under the BSD-3-Clause license.
+ * See COPYING file for more details and other copyrights
+ * that may apply.
+ */
 
 #include "slp_buffer.h" 
 #include "slp_xmalloc.h"
@@ -142,6 +148,21 @@
     return result;
 }
 
+/*=========================================================================*/
+size_t RemainingBufferSpace(SLPBuffer buf)
+/* Report remaining free buffer size in bytes.                             */
+/*                                                                         */
+/* Check if buffer is allocated and if so return bytes left in a           */
+/* @c SLPBuffer object.                                                    */
+/*                                                                         */
+/* @param[in] buf The SLPBuffer to be freed.                               */
+/*=========================================================================*/
+{
+   if (buf->allocated == 0) {
+      return 0;
+   }
+   return buf->end - buf->curpos;
+}
 
 /*=========================================================================*/
 SLPBuffer SLPBufferDup(SLPBuffer buf)
diff -ur openslp-1.2.1.orig/common/slp_buffer.h openslp-1.2.1/common/slp_buffer.h
--- openslp-1.2.1.orig/common/slp_buffer.h	2005-02-07 21:32:58.000000000 -0800
+++ openslp-1.2.1/common/slp_buffer.h	2019-11-26 21:58:16.000000000 -0800
@@ -48,6 +48,13 @@
 /*                                                                         */
 /***************************************************************************/
 
+/* Copyright (c) 2019 VMware, Inc.
+ * SPDX-License-Identifier: BSD-3-Clause
+ * This file is provided under the BSD-3-Clause license.
+ * See COPYING file for more details and other copyrights
+ * that may apply.
+ */
+
 #if(!defined SLP_BUFFER_H_INCLUDED)
 #define SLP_BUFFER_H_INCLUDED
 
@@ -147,6 +154,15 @@
 /* Returns the added item in the list.                                     */
 /*=========================================================================*/
 
+size_t RemainingBufferSpace(SLPBuffer buf);
+/*=========================================================================*/
+/* Return bytes left in buffer from current position                       */
+/*                                                                         */
+/* buf (IN) pointer to the buffer                                          */
+/*                                                                         */
+/* Returns number of bytes left in buffer from current position            */
+/*=========================================================================*/
+
 
 /*=========================================================================*/
 void* memdup(const void* src, int srclen);
diff -ur openslp-1.2.1.orig/slpd/slpd_process.c openslp-1.2.1/slpd/slpd_process.c
--- openslp-1.2.1.orig/slpd/slpd_process.c	2005-02-07 22:12:24.000000000 -0800
+++ openslp-1.2.1/slpd/slpd_process.c	2019-11-26 21:58:37.000000000 -0800
@@ -46,6 +46,13 @@
 /*                                                                         */
 /***************************************************************************/
 
+/* Copyright (c) 2019 VMware, Inc.
+ * SPDX-License-Identifier: BSD-3-Clause
+ * This file is provided under the BSD-3-Clause license.
+ * See COPYING file for more details and other copyrights
+ * that may apply.
+ */
+
 /*=========================================================================*/
 /* slpd includes                                                           */
 /*=========================================================================*/
@@ -447,11 +454,26 @@
         {
             /* urlentry is the url from the db result */
             urlentry = db->urlarray[i];
-
+            if (urlentry->opaque != NULL)
+            {
+                const int64_t newsize = size + urlentry->opaquelen;
+                if (urlentry->opaquelen <= 0 || newsize > INT_MAX)
+                {
+                    SLPDLog("Invalid opaquelen %d or sizeo of opaque url is too big, size=%d\n",
+                            urlentry->opaquelen, size);
+                    errorcode = SLP_ERROR_PARSE_ERROR;
+                    goto FINISHED;
+                }
+            size +=  urlentry->opaquelen;
+         }
+         else
+         {
+            /* urlentry is the url from the db result */
             size += urlentry->urllen + 6; /*  1 byte for reserved  */
                                           /*  2 bytes for lifetime */
                                           /*  2 bytes for urllen   */
                                           /*  1 byte for authcount */
+          }
 #ifdef ENABLE_SLPv2_SECURITY
 
             /* make room to include the authblock that was asked for */
@@ -527,7 +549,7 @@
             urlentry = db->urlarray[i]; 
 
 #ifdef ENABLE_SLPv1
-            if (urlentry->opaque == 0)
+            if (urlentry->opaque == NULL)
             {
                 /* url-entry reserved */
                 *result->curpos = 0;        
@@ -539,8 +561,18 @@
                 ToUINT16(result->curpos,urlentry->urllen);
                 result->curpos = result->curpos + 2;
                 /* url-entry url */
-                memcpy(result->curpos,urlentry->url,urlentry->urllen);
-                result->curpos = result->curpos + urlentry->urllen;
+                if (RemainingBufferSpace(result) >= urlentry->urllen)
+                {
+                   memcpy(result->curpos, urlentry->url, urlentry->urllen);
+                   result->curpos = result->curpos + urlentry->urllen;
+                }
+                else
+                {
+                   SLPDLog("Url too big (ask: %d have %lld), failing request\n",
+                           urlentry->opaquelen, (long long) RemainingBufferSpace(result));
+                   errorcode = SLP_ERROR_PARSE_ERROR;
+                   goto FINISHED;
+                }
                 /* url-entry auths */
                 *result->curpos = 0;
                 result->curpos = result->curpos + 1;
@@ -551,8 +583,18 @@
                 /* Use an opaque copy if available (and authentication is not being used)*/
                 /* TRICKY: fix up the lifetime */
                 ToUINT16(urlentry->opaque + 1,urlentry->lifetime);
-                memcpy(result->curpos,urlentry->opaque,urlentry->opaquelen);
-                result->curpos = result->curpos + urlentry->opaquelen;
+                if (RemainingBufferSpace(result) >= urlentry->opaquelen)
+                {
+                   memcpy(result->curpos, urlentry->opaque, urlentry->opaquelen);
+                   result->curpos = result->curpos + urlentry->opaquelen;
+                }
+                else
+                {
+                   SLPDLog("Opaque Url too big (ask: %d have %lld), failing request\n",
+                           urlentry->opaquelen, (long long) RemainingBufferSpace(result));
+                   errorcode = SLP_ERROR_PARSE_ERROR;
+                   goto FINISHED;
+                }
             }
         }
     }

============================== /PATCH FOR OPENSLP 1.2.1 ============================


============================== PATCH FOR OPENSLP 2.0.0 =============================

diff -ur openslp-2.0.0.orig/common/slp_buffer.c openslp-2.0.0/common/slp_buffer.c
--- openslp-2.0.0.orig/common/slp_buffer.c	2012-12-10 15:31:53.000000000 -0800
+++ openslp-2.0.0/common/slp_buffer.c	2019-11-26 21:54:20.000000000 -0800
@@ -30,6 +30,13 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *-------------------------------------------------------------------------*/
 
+/* Copyright (c) 2019 VMware, Inc.
+ * SPDX-License-Identifier: BSD-3-Clause
+ * This file is provided under the BSD-3-Clause license.
+ * See COPYING file for more details and other copyrights
+ * that may apply.
+ */
+
 /** Functions for managing SLP message buffers.
  *
  * This file provides a higher level abstraction over malloc and free that
@@ -153,4 +160,20 @@
    xfree(buf);
 }
 
+/** Report remaining free buffer size in bytes.
+ *
+ * Check if buffer is allocated and if so return bytes left in a
+ * @c SLPBuffer object.
+ *
+ * @param[in] buf The SLPBuffer to be freed.
+ */
+size_t
+RemainingBufferSpace(SLPBuffer buf)
+{
+   if (buf->allocated == 0) {
+      return 0;
+   }
+   return buf->end - buf->curpos;
+}
+
 /*=========================================================================*/
diff -ur openslp-2.0.0.orig/common/slp_buffer.h openslp-2.0.0/common/slp_buffer.h
--- openslp-2.0.0.orig/common/slp_buffer.h	2012-11-28 09:07:04.000000000 -0800
+++ openslp-2.0.0/common/slp_buffer.h	2019-11-26 21:54:32.000000000 -0800
@@ -30,6 +30,13 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *-------------------------------------------------------------------------*/
 
+/* Copyright (c) 2019 VMware, Inc.
+ * SPDX-License-Identifier: BSD-3-Clause
+ * This file is provided under the BSD-3-Clause license.
+ * See COPYING file for more details and other copyrights
+ * that may apply.
+ */
+
 /** Header file that defines SLP message buffer management routines.
  *
  * Includes structures, constants and functions that used to handle memory 
@@ -78,6 +85,8 @@
 
 SLPBuffer SLPBufferListAdd(SLPBuffer * list, SLPBuffer buf);
 
+size_t RemainingBufferSpace(SLPBuffer buf);
+
 /*! @} */
 
 #endif /* SLP_BUFFER_H_INCLUDED */
diff -ur openslp-2.0.0.orig/slpd/slpd_process.c openslp-2.0.0/slpd/slpd_process.c
--- openslp-2.0.0.orig/slpd/slpd_process.c	2012-12-12 09:38:54.000000000 -0800
+++ openslp-2.0.0/slpd/slpd_process.c	2019-11-26 21:55:10.000000000 -0800
@@ -30,6 +30,13 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *-------------------------------------------------------------------------*/
 
+/* Copyright (c) 2019 VMware, Inc.
+ * SPDX-License-Identifier: BSD-3-Clause
+ * This file is provided under the BSD-3-Clause license.
+ * See COPYING file for more details and other copyrights
+ * that may apply.
+ */
+
 /** Processes incoming SLP messages.
  *
  * @file       slpd_process.c
@@ -514,13 +521,27 @@
    {
       for (i = 0; i < db->urlcount; i++)
       {
-         /* urlentry is the url from the db result */
          urlentry = db->urlarray[i];
+         if (urlentry->opaque != NULL) {
+            const int64_t newsize = size + urlentry->opaquelen;
+            if (urlentry->opaquelen <= 0 || newsize > INT_MAX)
+            {
+               SLPDLog("Invalid opaquelen %d or sizeo of opaque url is too big, size=%d\n",
+                       urlentry->opaquelen, size);
+               errorcode = SLP_ERROR_PARSE_ERROR;
+               goto FINISHED;
+            }
+            size +=  urlentry->opaquelen;
+         }
+         else
+         {
+            /* urlentry is the url from the db result */
+            size += urlentry->urllen + 6; /*  1 byte for reserved  */
+                                          /*  2 bytes for lifetime */
+                                          /*  2 bytes for urllen   */
+                                          /*  1 byte for authcount */
+          }
 
-         size += urlentry->urllen + 6; /*  1 byte for reserved  */
-                                       /*  2 bytes for lifetime */
-                                       /*  2 bytes for urllen   */
-                                       /*  1 byte for authcount */
 #ifdef ENABLE_SLPv2_SECURITY
          /* make room to include the authblock that was asked for */
          if (G_SlpdProperty.securityEnabled
@@ -594,7 +615,7 @@
          urlentry = db->urlarray[i];
 
 #ifdef ENABLE_SLPv1
-         if (urlentry->opaque == 0)
+         if (urlentry->opaque == NULL)
          {
             /* url-entry reserved */
             *result->curpos++ = 0;
@@ -606,8 +627,18 @@
             PutUINT16(&result->curpos, urlentry->urllen);
 
             /* url-entry url */
-            memcpy(result->curpos, urlentry->url, urlentry->urllen);
-            result->curpos += urlentry->urllen;
+            if (RemainingBufferSpace(result) >= urlentry->urllen)
+            {
+               memcpy(result->curpos, urlentry->url, urlentry->urllen);
+               result->curpos = result->curpos + urlentry->urllen;
+            }
+            else
+            {
+                SLPDLog("Url too big (ask: %d have %" PRId64 "), failing request\n",
+                        urlentry->opaquelen, (int64_t) RemainingBufferSpace(result));
+                errorcode = SLP_ERROR_PARSE_ERROR;
+                goto FINISHED;
+            }
 
             /* url-entry auths */
             *result->curpos++ = 0;
@@ -621,8 +652,18 @@
 
             /* TRICKY: Fix up the lifetime. */
             TO_UINT16(urlentry->opaque + 1, urlentry->lifetime);
-            memcpy(result->curpos, urlentry->opaque, urlentry->opaquelen);
-            result->curpos += urlentry->opaquelen;
+            if (RemainingBufferSpace(result) >= urlentry->opaquelen)
+            {
+               memcpy(result->curpos, urlentry->opaque, urlentry->opaquelen);
+               result->curpos = result->curpos + urlentry->opaquelen;
+             }
+             else
+             {
+               SLPDLog("Opaque Url too big (ask: %d have %" PRId64 "), failing request\n",
+                       urlentry->opaquelen, (int64_t) RemainingBufferSpace(result));
+               errorcode = SLP_ERROR_PARSE_ERROR;
+               goto FINISHED;
+             }
          }
       }
    }

============================== /PATCH FOR OPENSLP 2.0.0 =============================



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