view libtomcrypt/src/pk/asn1/der/generalizedtime/der_length_generalizedtime.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 der_length_utctime.c
  ASN.1 DER, get length of GeneralizedTime, Steffen Jaeckel
  Based on der_length_utctime.c
*/

#ifdef LTC_DER

/**
  Gets length of DER encoding of GeneralizedTime
  @param gtime        The GeneralizedTime structure to get the size of
  @param outlen [out] The length of the DER encoding
  @return CRYPT_OK if successful
*/
int der_length_generalizedtime(ltc_generalizedtime *gtime, unsigned long *outlen)
{
   LTC_ARGCHK(outlen  != NULL);
   LTC_ARGCHK(gtime != NULL);

   if (gtime->fs == 0) {
      /* we encode as YYYYMMDDhhmmssZ */
      *outlen = 2 + 14 + 1;
   } else {
      unsigned long len = 2 + 14 + 1;
      unsigned fs = gtime->fs;
      do {
         fs /= 10;
         len++;
      } while(fs != 0);
      if (gtime->off_hh == 0 && gtime->off_mm == 0) {
         /* we encode as YYYYMMDDhhmmss.fsZ */
         len += 1;
      }
      else {
         /* we encode as YYYYMMDDhhmmss.fs{+|-}hh'mm' */
         len += 5;
      }
      *outlen = len;
   }

   return CRYPT_OK;
}

#endif

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