view libtomcrypt/src/mac/f9/f9_process.c @ 1715:3974f087d9c0

Disallow leading lines before the ident for server (#102) Per RFC4253 4.2 clients must be able to process other lines of data before the version string, server behavior is not defined neither with MUST/SHOULD nor with MAY. If server process up to 50 lines too - it may cause too long hanging session with invalid/evil client that consume host resources and potentially may lead to DDoS on poor embedded boxes. Let's require first line from client to be version string and fail early if it's not - matches both RFC and real OpenSSH behavior.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 15 Jun 2020 18:22:18 +0500
parents 6dba84798cd5
children
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */
#include "tomcrypt.h"

/**
  @file f9_process.c
  f9 Support, process blocks with f9
*/

#ifdef LTC_F9_MODE

/** Process data through f9-MAC
  @param f9       The f9-MAC state
  @param in       Input data to process
  @param inlen    Length of input in octets
  Return CRYPT_OK on success
*/
int f9_process(f9_state *f9, const unsigned char *in, unsigned long inlen)
{
   int err, x;

   LTC_ARGCHK(f9 != NULL);
   LTC_ARGCHK(in   != NULL);

   /* check structure */
   if ((err = cipher_is_valid(f9->cipher)) != CRYPT_OK) {
      return err;
   }

   if ((f9->blocksize > cipher_descriptor[f9->cipher].block_length) || (f9->blocksize < 0) ||
       (f9->buflen > f9->blocksize) || (f9->buflen < 0)) {
      return CRYPT_INVALID_ARG;
   }

#ifdef LTC_FAST
   if (f9->buflen == 0) {
       while (inlen >= (unsigned long)f9->blocksize) {
           for (x = 0; x < f9->blocksize; x += sizeof(LTC_FAST_TYPE)) {
              *(LTC_FAST_TYPE_PTR_CAST(&(f9->IV[x]))) ^= *(LTC_FAST_TYPE_PTR_CAST(&(in[x])));
           }
           cipher_descriptor[f9->cipher].ecb_encrypt(f9->IV, f9->IV, &f9->key);
           for (x = 0; x < f9->blocksize; x += sizeof(LTC_FAST_TYPE)) {
              *(LTC_FAST_TYPE_PTR_CAST(&(f9->ACC[x]))) ^= *(LTC_FAST_TYPE_PTR_CAST(&(f9->IV[x])));
           }
           in    += f9->blocksize;
           inlen -= f9->blocksize;
       }
   }
#endif

   while (inlen) {
      if (f9->buflen == f9->blocksize) {
         cipher_descriptor[f9->cipher].ecb_encrypt(f9->IV, f9->IV, &f9->key);
         for (x = 0; x < f9->blocksize; x++) {
            f9->ACC[x] ^= f9->IV[x];
         }
         f9->buflen = 0;
      }
      f9->IV[f9->buflen++] ^= *in++;
      --inlen;
   }
   return CRYPT_OK;
}

#endif

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