Corrected bug in checking the third number and added extra checks

webrtc/test/channel_transport/udp_transport_impl.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 2904 matching lines @@
         int32_t nDots = 0;
         int32_t iDotPos[4] = {0,0,0,0};
 
         for (i = 0; (i < len) && (nDots < 4); i++)
         {
             if (ipadr[i] == (char)'.')
             {
                 // Store index of dots and count number of dots.
                 iDotPos[nDots++] = i;
             }
+            else if (isdigit(ipadr[i]) == 0)
+            {
+                return false;
+            }
         }
 
         bool allUnder256 = false;
         // TODO (hellner): while loop seems to be abused here to get
         // label like functionality. Fix later to avoid introducing bugs now.
 
         // Check that all numbers are smaller than 256.
         do
         {
             if (nDots != 3 )
             {
                 break;
             }
 
             if (iDotPos[0] <= 3)
             {
                 char nr[4];
                 memset(nr,0,4);
                 strncpy(nr,&ipadr[0],iDotPos[0]);
                 int32_t num = atoi(nr);
-                if (num > 255)
+                if (num > 255 || num < 0)
                 {
                     break;
                 }
             } else {
                 break;
             }
 
             if (iDotPos[1] - iDotPos[0] <= 4)
             {
                 char nr[4];
                 memset(nr,0,4);
                 strncpy(nr,&ipadr[iDotPos[0]+1], iDotPos[1] - iDotPos[0] - 1);
                 int32_t num = atoi(nr);
-                if (num > 255)
+                if (num > 255 || num < 0)
                     break;
             } else {
                 break;
             }
 
             if (iDotPos[2] - iDotPos[1] <= 4)
             {
                 char nr[4];
                 memset(nr,0,4);
-                strncpy(nr,&ipadr[iDotPos[1]+1], iDotPos[1] - iDotPos[0] - 1);
+                strncpy(nr,&ipadr[iDotPos[1]+1], iDotPos[2] - iDotPos[1] - 1);
                 int32_t num = atoi(nr);
-                if (num > 255)
+                if (num > 255 || num < 0)
                     break;
+            } else {
+                break;
+            }
 
+            if (len - iDotPos[2] <= 4)
+            {
+                char nr[4];
                 memset(nr,0,4);
                 strncpy(nr,&ipadr[iDotPos[2]+1], len - iDotPos[2] -1);
-                num = atoi(nr);
-                if (num > 255)
+                int32_t num = atoi(nr);
+                if (num > 255 || num < 0)
                     break;
                 else
                     allUnder256 = true;
-            } else
+            } else {
                 break;
+            }
         } while(false);
 
         if (nDots != 3 || !allUnder256)
         {
             return false;
         }
     }
     return true;
 }
 
 }  // namespace test
 }  // namespace webrtc