view libtomcrypt/src/pk/asn1/der/sequence/der_encode_sequence_ex.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"


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

#ifdef LTC_DER

/**
   Encode a SEQUENCE
   @param list      The list of items to encode
   @param inlen     The number of items in the list
   @param out       [out] The destination
   @param outlen    [in/out] The size of the output
   @param type_of   LTC_ASN1_SEQUENCE or LTC_ASN1_SET/LTC_ASN1_SETOF
   @return CRYPT_OK on success
*/
int der_encode_sequence_ex(ltc_asn1_list *list, unsigned long inlen,
                           unsigned char *out,  unsigned long *outlen, int type_of)
{
   int           err;
   ltc_asn1_type type;
   unsigned long size, x, y, z, i;
   void          *data;

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

   /* get size of output that will be required */
   y = 0; z = 0;
   if ((err = der_length_sequence_ex(list, inlen, &y, &z)) != CRYPT_OK) return CRYPT_INVALID_ARG;

   /* too big ? */
   if (*outlen < y) {
      *outlen = y;
      err = CRYPT_BUFFER_OVERFLOW;
      goto LBL_ERR;
   }

   /* store header */
   x = 0;
   out[x++] = (type_of == LTC_ASN1_SEQUENCE) ? 0x30 : 0x31;

   if (z < 128) {
      out[x++] = (unsigned char)z;
   } else if (z < 256) {
      out[x++] = 0x81;
      out[x++] = (unsigned char)z;
   } else if (z < 65536UL) {
      out[x++] = 0x82;
      out[x++] = (unsigned char)((z>>8UL)&255);
      out[x++] = (unsigned char)(z&255);
   } else if (z < 16777216UL) {
      out[x++] = 0x83;
      out[x++] = (unsigned char)((z>>16UL)&255);
      out[x++] = (unsigned char)((z>>8UL)&255);
      out[x++] = (unsigned char)(z&255);
   }

   /* store data */
   *outlen -= x;
   for (i = 0; i < inlen; i++) {
       type = list[i].type;
       size = list[i].size;
       data = list[i].data;

       if (type == LTC_ASN1_EOL) {
          break;
       }

       switch (type) {
            case LTC_ASN1_BOOLEAN:
               z = *outlen;
               if ((err = der_encode_boolean(*((int *)data), out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_INTEGER:
               z = *outlen;
               if ((err = der_encode_integer(data, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_SHORT_INTEGER:
               z = *outlen;
               if ((err = der_encode_short_integer(*((unsigned long*)data), out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_BIT_STRING:
               z = *outlen;
               if ((err = der_encode_bit_string(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_RAW_BIT_STRING:
               z = *outlen;
               if ((err = der_encode_raw_bit_string(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_OCTET_STRING:
               z = *outlen;
               if ((err = der_encode_octet_string(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_NULL:
               out[x] = 0x05;
               out[x+1] = 0x00;
               z = 2;
               break;

           case LTC_ASN1_OBJECT_IDENTIFIER:
               z = *outlen;
               if ((err = der_encode_object_identifier(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_IA5_STRING:
               z = *outlen;
               if ((err = der_encode_ia5_string(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_PRINTABLE_STRING:
               z = *outlen;
               if ((err = der_encode_printable_string(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_UTF8_STRING:
               z = *outlen;
               if ((err = der_encode_utf8_string(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_UTCTIME:
               z = *outlen;
               if ((err = der_encode_utctime(data, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_GENERALIZEDTIME:
               z = *outlen;
               if ((err = der_encode_generalizedtime(data, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_SET:
               z = *outlen;
               if ((err = der_encode_set(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_SETOF:
               z = *outlen;
               if ((err = der_encode_setof(data, size, out + x, &z)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_SEQUENCE:
               z = *outlen;
               if ((err = der_encode_sequence_ex(data, size, out + x, &z, type)) != CRYPT_OK) {
                  goto LBL_ERR;
               }
               break;

           case LTC_ASN1_CHOICE:
           case LTC_ASN1_CONSTRUCTED:
           case LTC_ASN1_CONTEXT_SPECIFIC:
           case LTC_ASN1_EOL:
           case LTC_ASN1_TELETEX_STRING:
               err = CRYPT_INVALID_ARG;
               goto LBL_ERR;
       }

       x       += z;
       *outlen -= z;
   }
   *outlen = x;
   err = CRYPT_OK;

LBL_ERR:
   return err;
}

#endif

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