view libtomcrypt/src/pk/asn1/der/sequence/der_encode_sequence_multi.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
line wrap: on
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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>


/**
  @file der_encode_sequence_multi.c
  ASN.1 DER, encode a SEQUENCE, Tom St Denis
*/

#ifdef LTC_DER

/**
  Encode a SEQUENCE type using a VA list
  @param out    [out] Destination for data
  @param outlen [in/out] Length of buffer and resulting length of output
  @remark <...> is of the form <type, size, data> (int, unsigned long, void*)
  @return CRYPT_OK on success
*/
int der_encode_sequence_multi(unsigned char *out, unsigned long *outlen, ...)
{
   int           err;
   ltc_asn1_type type;
   unsigned long size, x;
   void          *data;
   va_list       args;
   ltc_asn1_list *list;

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

   /* get size of output that will be required */
   va_start(args, outlen);
   x = 0;
   for (;;) {
       type = (ltc_asn1_type)va_arg(args, int);
       size = va_arg(args, unsigned long);
       data = va_arg(args, void*);
       LTC_UNUSED_PARAM(size);
       LTC_UNUSED_PARAM(data);

       if (type == LTC_ASN1_EOL) {
          break;
       }

       switch (type) {
           case LTC_ASN1_BOOLEAN:
           case LTC_ASN1_INTEGER:
           case LTC_ASN1_SHORT_INTEGER:
           case LTC_ASN1_BIT_STRING:
           case LTC_ASN1_OCTET_STRING:
           case LTC_ASN1_NULL:
           case LTC_ASN1_OBJECT_IDENTIFIER:
           case LTC_ASN1_IA5_STRING:
           case LTC_ASN1_PRINTABLE_STRING:
           case LTC_ASN1_UTF8_STRING:
           case LTC_ASN1_UTCTIME:
           case LTC_ASN1_SEQUENCE:
           case LTC_ASN1_SET:
           case LTC_ASN1_SETOF:
           case LTC_ASN1_RAW_BIT_STRING:
           case LTC_ASN1_GENERALIZEDTIME:
                ++x;
                break;

           case LTC_ASN1_CHOICE:
           case LTC_ASN1_CONSTRUCTED:
           case LTC_ASN1_CONTEXT_SPECIFIC:
           case LTC_ASN1_EOL:
           case LTC_ASN1_TELETEX_STRING:
               va_end(args);
               return CRYPT_INVALID_ARG;
       }
   }
   va_end(args);

   /* allocate structure for x elements */
   if (x == 0) {
      return CRYPT_NOP;
   }

   list = XCALLOC(sizeof(*list), x);
   if (list == NULL) {
      return CRYPT_MEM;
   }

   /* fill in the structure */
   va_start(args, outlen);
   x = 0;
   for (;;) {
       type = (ltc_asn1_type)va_arg(args, int);
       size = va_arg(args, unsigned long);
       data = va_arg(args, void*);

       if (type == LTC_ASN1_EOL) {
          break;
       }

       switch (type) {
           case LTC_ASN1_BOOLEAN:
           case LTC_ASN1_INTEGER:
           case LTC_ASN1_SHORT_INTEGER:
           case LTC_ASN1_BIT_STRING:
           case LTC_ASN1_OCTET_STRING:
           case LTC_ASN1_NULL:
           case LTC_ASN1_OBJECT_IDENTIFIER:
           case LTC_ASN1_IA5_STRING:
           case LTC_ASN1_PRINTABLE_STRING:
           case LTC_ASN1_UTF8_STRING:
           case LTC_ASN1_UTCTIME:
           case LTC_ASN1_SEQUENCE:
           case LTC_ASN1_SET:
           case LTC_ASN1_SETOF:
           case LTC_ASN1_RAW_BIT_STRING:
           case LTC_ASN1_GENERALIZEDTIME:
                LTC_SET_ASN1(list, x++, type, data, size);
                break;

           case LTC_ASN1_CHOICE:
           case LTC_ASN1_CONSTRUCTED:
           case LTC_ASN1_CONTEXT_SPECIFIC:
           case LTC_ASN1_EOL:
           case LTC_ASN1_TELETEX_STRING:
               va_end(args);
               err = CRYPT_INVALID_ARG;
               goto LBL_ERR;
       }
   }
   va_end(args);

   err = der_encode_sequence(list, x, out, outlen);
LBL_ERR:
   XFREE(list);
   return err;
}

#endif


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