text: /* 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"
  
  #ifdef LTC_MDH
  
  /**
    Import a DH key from a binary packet
    @param in     The packet to read
    @param inlen  The length of the input packet
    @param key    [out] Where to import the key to
    @return CRYPT_OK if successful, on error all allocated memory is freed automatically
  */
  int dh_import(const unsigned char *in, unsigned long inlen, dh_key *key)
  {
     unsigned char flags[1];
     int err;
     unsigned long version;
  
     LTC_ARGCHK(in  != NULL);
     LTC_ARGCHK(key != NULL);
  
     /* init */
     if ((err = mp_init_multi(&key->x, &key->y, &key->base, &key->prime, NULL)) != CRYPT_OK) {
        return err;
     }
  
     /* find out what type of key it is */
     err = der_decode_sequence_multi(in, inlen,
                                     LTC_ASN1_SHORT_INTEGER, 1UL, &version,
                                     LTC_ASN1_BIT_STRING, 1UL, &flags,
                                     LTC_ASN1_EOL, 0UL, NULL);
     if (err != CRYPT_OK && err != CRYPT_INPUT_TOO_LONG) {
        goto error;
     }
  
     if (version == 0) {
        if (flags[0] == 1) {
           key->type = PK_PRIVATE;
           if ((err = der_decode_sequence_multi(in, inlen,
                                                LTC_ASN1_SHORT_INTEGER, 1UL, &version,
                                                LTC_ASN1_BIT_STRING,    1UL, flags,
                                                LTC_ASN1_INTEGER,       1UL, key->prime,
                                                LTC_ASN1_INTEGER,       1UL, key->base,
                                                LTC_ASN1_INTEGER,       1UL, key->x,
                                                LTC_ASN1_EOL,           0UL, NULL)) != CRYPT_OK) {
              goto error;
           }
           /* compute public key: y = (base ^ x) mod prime */
           if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) {
              goto error;
           }
        }
        else if (flags[0] == 0) {
           key->type = PK_PUBLIC;
           if ((err = der_decode_sequence_multi(in, inlen,
                                                LTC_ASN1_SHORT_INTEGER, 1UL, &version,
                                                LTC_ASN1_BIT_STRING,    1UL, flags,
                                                LTC_ASN1_INTEGER,       1UL, key->prime,
                                                LTC_ASN1_INTEGER,       1UL, key->base,
                                                LTC_ASN1_INTEGER,       1UL, key->y,
                                                LTC_ASN1_EOL,           0UL, NULL)) != CRYPT_OK) {
              goto error;
           }
        }
        else {
           err = CRYPT_INVALID_PACKET;
           goto error;
        }
     }
     else {
        err = CRYPT_INVALID_PACKET;
        goto error;
     }
  
     /* check public key */
     if ((err = dh_check_pubkey(key)) != CRYPT_OK) {
        goto error;
     }
  
     return CRYPT_OK;
  
  error:
     dh_free(key);
     return err;
  }
  
  #endif /* LTC_MDH */
  
  /* ref:         HEAD -> master, tag: v1.18.2 */
  /* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
  /* commit time: 2018-07-01 22:49:01 +0200 */
  