view libtomcrypt/src/pk/katja/katja_encrypt_key.c @ 1861:2b3a8026a6ce

Add re-exec for server This allows ASLR to re-randomize the address space for every connection, preventing some vulnerabilities from being exploitable by repeated probing. Overhead (memory and time) is yet to be confirmed. At present this is only enabled on Linux. Other BSD platforms with fexecve() would probably also work though have not been tested.
author Matt Johnston <matt@ucc.asn.au>
date Sun, 30 Jan 2022 10:14:56 +0800
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 katja_encrypt_key.c
  Katja PKCS-style OAEP encryption, Tom St Denis
*/

#ifdef LTC_MKAT

/**
    (PKCS #1 v2.0) OAEP pad then encrypt
    @param in          The plaintext
    @param inlen       The length of the plaintext (octets)
    @param out         [out] The ciphertext
    @param outlen      [in/out] The max size and resulting size of the ciphertext
    @param lparam      The system "lparam" for the encryption
    @param lparamlen   The length of lparam (octets)
    @param prng        An active PRNG
    @param prng_idx    The index of the desired prng
    @param hash_idx    The index of the desired hash
    @param key         The Katja key to encrypt to
    @return CRYPT_OK if successful
*/
int katja_encrypt_key(const unsigned char *in,     unsigned long inlen,
                          unsigned char *out,    unsigned long *outlen,
                    const unsigned char *lparam, unsigned long lparamlen,
                    prng_state *prng, int prng_idx, int hash_idx, katja_key *key)
{
  unsigned long modulus_bitlen, modulus_bytelen, x;
  int           err;

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

  /* valid prng and hash ? */
  if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
     return err;
  }
  if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
     return err;
  }

  /* get modulus len in bits */
  modulus_bitlen = mp_count_bits((key->N));

  /* payload is upto pq, so we know q is 1/3rd the size of N and therefore pq is 2/3th the size */
  modulus_bitlen = ((modulus_bitlen << 1) / 3);

  /* round down to next byte */
  modulus_bitlen -= (modulus_bitlen & 7) + 8;

  /* outlen must be at least the size of the modulus */
  modulus_bytelen = mp_unsigned_bin_size((key->N));
  if (modulus_bytelen > *outlen) {
     *outlen = modulus_bytelen;
     return CRYPT_BUFFER_OVERFLOW;
  }

  /* OAEP pad the key */
  x = *outlen;
  if ((err = pkcs_1_oaep_encode(in, inlen, lparam,
                                lparamlen, modulus_bitlen, prng, prng_idx, hash_idx,
                                out, &x)) != CRYPT_OK) {
     return err;
  }

  /* Katja exptmod the OAEP pad */
  return katja_exptmod(out, x, out, outlen, PK_PUBLIC, key);
}

#endif /* LTC_MRSA */

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