view libtomcrypt/src/pk/asn1/der/choice/der_decode_choice.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_decode_choice.c
  ASN.1 DER, decode a CHOICE, Tom St Denis
*/

#ifdef LTC_DER

/**
   Decode a CHOICE
   @param in       The DER encoded input
   @param inlen    [in/out] The size of the input and resulting size of read type
   @param list     The list of items to decode
   @param outlen   The number of items in the list
   @return CRYPT_OK on success
*/
int der_decode_choice(const unsigned char *in,   unsigned long *inlen,
                            ltc_asn1_list *list, unsigned long  outlen)
{
   unsigned long size, x, z;
   void          *data;

   LTC_ARGCHK(in    != NULL);
   LTC_ARGCHK(inlen != NULL);
   LTC_ARGCHK(list  != NULL);

   /* get blk size */
   if (*inlen < 2) {
      return CRYPT_INVALID_PACKET;
   }

   /* set all of the "used" flags to zero */
   for (x = 0; x < outlen; x++) {
       list[x].used = 0;
   }

   /* now scan until we have a winner */
   for (x = 0; x < outlen; x++) {
       size = list[x].size;
       data = list[x].data;

       switch (list[x].type) {
           case LTC_ASN1_BOOLEAN:
               if (der_decode_boolean(in, *inlen, data) == CRYPT_OK) {
                  if (der_length_boolean(&z) == CRYPT_OK) {
                      list[x].used = 1;
                      *inlen       = z;
                      return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_INTEGER:
               if (der_decode_integer(in, *inlen, data) == CRYPT_OK) {
                  if (der_length_integer(data, &z) == CRYPT_OK) {
                      list[x].used = 1;
                      *inlen       = z;
                      return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_SHORT_INTEGER:
               if (der_decode_short_integer(in, *inlen, data) == CRYPT_OK) {
                  if (der_length_short_integer(size, &z) == CRYPT_OK) {
                      list[x].used = 1;
                      *inlen       = z;
                      return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_BIT_STRING:
               if (der_decode_bit_string(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_bit_string(size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_RAW_BIT_STRING:
               if (der_decode_raw_bit_string(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_bit_string(size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_OCTET_STRING:
               if (der_decode_octet_string(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_octet_string(size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_NULL:
               if (*inlen == 2 && in[x] == 0x05 && in[x+1] == 0x00) {
                  *inlen = 2;
                  list[x].used   = 1;
                  return CRYPT_OK;
               }
               break;

           case LTC_ASN1_OBJECT_IDENTIFIER:
               if (der_decode_object_identifier(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_object_identifier(data, size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_TELETEX_STRING:
               if (der_decode_teletex_string(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_teletex_string(data, size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_IA5_STRING:
               if (der_decode_ia5_string(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_ia5_string(data, size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_PRINTABLE_STRING:
               if (der_decode_printable_string(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_printable_string(data, size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_UTF8_STRING:
               if (der_decode_utf8_string(in, *inlen, data, &size) == CRYPT_OK) {
                  if (der_length_utf8_string(data, size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     list[x].size = size;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_UTCTIME:
               z = *inlen;
               if (der_decode_utctime(in, &z, data) == CRYPT_OK) {
                  list[x].used = 1;
                  *inlen       = z;
                  return CRYPT_OK;
               }
               break;

           case LTC_ASN1_GENERALIZEDTIME:
               z = *inlen;
               if (der_decode_generalizedtime(in, &z, data) == CRYPT_OK) {
                  list[x].used = 1;
                  *inlen       = z;
                  return CRYPT_OK;
               }
               break;

           case LTC_ASN1_SET:
           case LTC_ASN1_SETOF:
           case LTC_ASN1_SEQUENCE:
               if (der_decode_sequence(in, *inlen, data, size) == CRYPT_OK) {
                  if (der_length_sequence(data, size, &z) == CRYPT_OK) {
                     list[x].used = 1;
                     *inlen       = z;
                     return CRYPT_OK;
                  }
               }
               break;

           case LTC_ASN1_CHOICE:
           case LTC_ASN1_CONSTRUCTED:
           case LTC_ASN1_CONTEXT_SPECIFIC:
           case LTC_ASN1_EOL:
               return CRYPT_INVALID_ARG;
       }
   }

   return CRYPT_INVALID_PACKET;
}

#endif

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