view libtomcrypt/src/mac/f9/f9_file.c @ 1790:42745af83b7d

Introduce extra delay before closing unauthenticated sessions To make it harder for attackers, introduce a delay to keep an unauthenticated session open a bit longer, thus blocking a connection slot until after the delay. Without this, while there is a limit on the amount of attempts an attacker can make at the same time (MAX_UNAUTH_PER_IP), the time taken by dropbear to handle one attempt is still short and thus for each of the allowed parallel attempts many attempts can be chained one after the other. The attempt rate is then: "MAX_UNAUTH_PER_IP / <process time of one attempt>". With the delay, this rate becomes: "MAX_UNAUTH_PER_IP / UNAUTH_CLOSE_DELAY".
author Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
date Wed, 15 Feb 2017 13:53:04 +0100
parents e9dba7abd939
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_file.c
  f9 support, process a file, Tom St Denis
*/

#ifdef LTC_F9_MODE

/**
   f9 a file
   @param cipher   The index of the cipher desired
   @param key      The secret key
   @param keylen   The length of the secret key (octets)
   @param fname    The name of the file you wish to f9
   @param out      [out] Where the authentication tag is to be stored
   @param outlen   [in/out] The max size and resulting size of the authentication tag
   @return CRYPT_OK if successful, CRYPT_NOP if file support has been disabled
*/
int f9_file(int cipher,
              const unsigned char *key, unsigned long keylen,
              const char *fname,
                    unsigned char *out, unsigned long *outlen)
{
#ifdef LTC_NO_FILE
   LTC_UNUSED_PARAM(cipher);
   LTC_UNUSED_PARAM(key);
   LTC_UNUSED_PARAM(keylen);
   LTC_UNUSED_PARAM(fname);
   LTC_UNUSED_PARAM(out);
   LTC_UNUSED_PARAM(outlen);
   return CRYPT_NOP;
#else
   size_t x;
   int err;
   f9_state f9;
   FILE *in;
   unsigned char *buf;

   LTC_ARGCHK(key    != NULL);
   LTC_ARGCHK(fname  != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(outlen != NULL);

   if ((buf = XMALLOC(LTC_FILE_READ_BUFSIZE)) == NULL) {
      return CRYPT_MEM;
   }

   if ((err = f9_init(&f9, cipher, key, keylen)) != CRYPT_OK) {
      goto LBL_ERR;
   }

   in = fopen(fname, "rb");
   if (in == NULL) {
      err = CRYPT_FILE_NOTFOUND;
      goto LBL_ERR;
   }

   do {
      x = fread(buf, 1, LTC_FILE_READ_BUFSIZE, in);
      if ((err = f9_process(&f9, buf, (unsigned long)x)) != CRYPT_OK) {
         fclose(in);
         goto LBL_CLEANBUF;
      }
   } while (x == LTC_FILE_READ_BUFSIZE);

   if (fclose(in) != 0) {
      err = CRYPT_ERROR;
      goto LBL_CLEANBUF;
   }

   err = f9_done(&f9, out, outlen);

LBL_CLEANBUF:
   zeromem(buf, LTC_FILE_READ_BUFSIZE);
LBL_ERR:
#ifdef LTC_CLEAN_STACK
   zeromem(&f9, sizeof(f9_state));
#endif
   XFREE(buf);
   return err;
#endif
}

#endif

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/* git commit:  $Format:%H$ */
/* commit time: $Format:%ai$ */