src/usr.bin/ssh/packet.c - diff

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Diff for /src/usr.bin/ssh/packet.c between version 1.52 and 1.53

-version 1.52, 2001/02/27 10:35:27
+version 1.53, 2001/02/28 09:57:06
 Line 1299
 Line 1299
 Line 1299
          max_packet_size = s;
          return s;
  }
+ /*
+  * 9.2.  Ignored Data Message
+  *
+  *   byte      SSH_MSG_IGNORE
+  *   string    data
+  *
+  * All implementations MUST understand (and ignore) this message at any
+  * time (after receiving the protocol version). No implementation is
+  * required to send them. This message can be used as an additional
+  * protection measure against advanced traffic analysis techniques.
+  */
+ /* size of current + ignore message should be n*sumlen bytes (w/o mac) */
+ void
+ packet_inject_ignore(int sumlen)
+ {
+         u_int32_t rand = 0;
+         int i, blocksize, padlen, have, need, nb, mini, nbytes;
+         Enc *enc = NULL;
+         if (use_ssh2_packet_format == 0)
+                 return;
+         have = buffer_len(&outgoing_packet);
+         debug2("packet_inject_ignore: current %d", have);
+         if (kex != NULL)
+         enc  = &kex->enc[MODE_OUT];
+         blocksize = enc ? enc->cipher->block_size : 8;
+         padlen = blocksize - (have % blocksize);
+         if (padlen < 4)
+                 padlen += blocksize;
+         have += padlen;
+         have /= blocksize;      /* # of blocks for current message */
+         nb   = roundup(sumlen,  blocksize) / blocksize; /* blocks for both */
+         mini = roundup(5+1+4+4, blocksize) / blocksize; /* minsize ignore msg */
+         need = nb - (have % nb);                        /* blocks for ignore */
+         if (need <= mini)
+                 need += nb;
+         nbytes = (need - mini) * blocksize;     /* size of ignore payload */
+         debug2("packet_inject_ignore: block %d have %d nb %d mini %d need %d",
+             blocksize, have, nb, mini, need);
+         /* enqueue current message and append a ignore message */
+         packet_send();
+         packet_start(SSH2_MSG_IGNORE);
+         packet_put_int(nbytes);
+         for(i = 0; i < nbytes; i++) {
+                 if (i % 4 == 0)
+                         rand = arc4random();
+                 packet_put_char(rand & 0xff);
+                 rand >>= 8;
+         }
+ }