view libtomcrypt/src/pk/asn1/der/ia5/der_encode_ia5_string.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"

/**
  @file der_encode_ia5_string.c
  ASN.1 DER, encode a IA5 STRING, Tom St Denis
*/

#ifdef LTC_DER

/**
  Store an IA5 STRING
  @param in       The array of IA5 to store (one per char)
  @param inlen    The number of IA5 to store
  @param out      [out] The destination for the DER encoded IA5 STRING
  @param outlen   [in/out] The max size and resulting size of the DER IA5 STRING
  @return CRYPT_OK if successful
*/
int der_encode_ia5_string(const unsigned char *in, unsigned long inlen,
                                unsigned char *out, unsigned long *outlen)
{
   unsigned long x, y, len;
   int           err;

   LTC_ARGCHK(in     != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(outlen != NULL);

   /* get the size */
   if ((err = der_length_ia5_string(in, inlen, &len)) != CRYPT_OK) {
      return err;
   }

   /* too big? */
   if (len > *outlen) {
      *outlen = len;
      return CRYPT_BUFFER_OVERFLOW;
   }

   /* encode the header+len */
   x = 0;
   out[x++] = 0x16;
   if (inlen < 128) {
      out[x++] = (unsigned char)inlen;
   } else if (inlen < 256) {
      out[x++] = 0x81;
      out[x++] = (unsigned char)inlen;
   } else if (inlen < 65536UL) {
      out[x++] = 0x82;
      out[x++] = (unsigned char)((inlen>>8)&255);
      out[x++] = (unsigned char)(inlen&255);
   } else if (inlen < 16777216UL) {
      out[x++] = 0x83;
      out[x++] = (unsigned char)((inlen>>16)&255);
      out[x++] = (unsigned char)((inlen>>8)&255);
      out[x++] = (unsigned char)(inlen&255);
   } else {
      return CRYPT_INVALID_ARG;
   }

   /* store octets */
   for (y = 0; y < inlen; y++) {
       out[x++] = der_ia5_char_encode(in[y]);
   }

   /* retun length */
   *outlen = x;

   return CRYPT_OK;
}

#endif

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