view libtomcrypt/src/mac/blake2/blake2bmac_memory_multi.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 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"
#include <stdarg.h>

#ifdef LTC_BLAKE2BMAC

/**
   BLAKE2B MAC multiple blocks of memory to produce the authentication tag
   @param key       The secret key
   @param keylen    The length of the secret key (octets)
   @param mac       [out] Destination of the authentication tag
   @param maclen    [in/out] Max size and resulting size of authentication tag
   @param in        The data to BLAKE2B MAC
   @param inlen     The length of the data to BLAKE2B MAC (octets)
   @param ...       tuples of (data,len) pairs to BLAKE2B MAC, terminated with a (NULL,x) (x=don't care)
   @return CRYPT_OK if successful
*/
int blake2bmac_memory_multi(const unsigned char *key, unsigned long keylen, unsigned char *mac, unsigned long *maclen, const unsigned char *in,  unsigned long inlen, ...)
{
   blake2bmac_state st;
   int err;
   va_list args;
   const unsigned char *curptr;
   unsigned long curlen;

   LTC_ARGCHK(key    != NULL);
   LTC_ARGCHK(in     != NULL);
   LTC_ARGCHK(mac    != NULL);
   LTC_ARGCHK(maclen != NULL);

   va_start(args, inlen);
   curptr = in;
   curlen = inlen;
   if ((err = blake2bmac_init(&st, *maclen, key, keylen)) != CRYPT_OK)          { goto LBL_ERR; }
   for (;;) {
      if ((err = blake2bmac_process(&st, curptr, curlen)) != CRYPT_OK) { goto LBL_ERR; }
      curptr = va_arg(args, const unsigned char*);
      if (curptr == NULL) break;
      curlen = va_arg(args, unsigned long);
   }
   err = blake2bmac_done(&st, mac, maclen);
LBL_ERR:
#ifdef LTC_CLEAN_STACK
   zeromem(&st, sizeof(blake2bmac_state));
#endif
   va_end(args);
   return err;
}

#endif

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