/* Copyright (c) 2019, Google Inc.

 *

 * Permission to use, copy, modify, and/or distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY

 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION

 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN

 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include <openssl/evp.h>

#include <openssl/bytestring.h>

#include <openssl/curve25519.h>

#include <openssl/err.h>

#include <openssl/mem.h>

#include "internal.h"

#include "../internal.h"

static void x25519_free(EVP_PKEY *pkey) {

  OPENSSL_free(pkey->pkey);

  pkey->pkey = NULL;

}

static int x25519_set_priv_raw(EVP_PKEY *pkey, const uint8_t *in, size_t len) {

  if (len != 32) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);

    return 0;

  }

  X25519_KEY *key = OPENSSL_malloc(sizeof(X25519_KEY));

  if (key == NULL) {

    return 0;

  }

  OPENSSL_memcpy(key->priv, in, 32);

  X25519_public_from_private(key->pub, key->priv);

  key->has_private = 1;

  x25519_free(pkey);

  pkey->pkey = key;

  return 1;

}

static int x25519_set_pub_raw(EVP_PKEY *pkey, const uint8_t *in, size_t len) {

  if (len != 32) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);

    return 0;

  }

  X25519_KEY *key = OPENSSL_malloc(sizeof(X25519_KEY));

  if (key == NULL) {

    return 0;

  }

  OPENSSL_memcpy(key->pub, in, 32);

  key->has_private = 0;

  x25519_free(pkey);

  pkey->pkey = key;

  return 1;

}

static int x25519_get_priv_raw(const EVP_PKEY *pkey, uint8_t *out,

                               size_t *out_len) {

  const X25519_KEY *key = pkey->pkey;

  if (!key->has_private) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_NOT_A_PRIVATE_KEY);

    return 0;

  }

  if (out == NULL) {

    *out_len = 32;

    return 1;

  }

  if (*out_len < 32) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_BUFFER_TOO_SMALL);

    return 0;

  }

  OPENSSL_memcpy(out, key->priv, 32);

  *out_len = 32;

  return 1;

}

static int x25519_get_pub_raw(const EVP_PKEY *pkey, uint8_t *out,

                               size_t *out_len) {

  const X25519_KEY *key = pkey->pkey;

  if (out == NULL) {

    *out_len = 32;

    return 1;

  }

  if (*out_len < 32) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_BUFFER_TOO_SMALL);

    return 0;

  }

  OPENSSL_memcpy(out, key->pub, 32);

  *out_len = 32;

  return 1;

}

static int x25519_set1_tls_encodedpoint(EVP_PKEY *pkey, const uint8_t *in,

                                        size_t len) {

  return x25519_set_pub_raw(pkey, in, len);

}

static size_t x25519_get1_tls_encodedpoint(const EVP_PKEY *pkey,

                                           uint8_t **out_ptr) {

  const X25519_KEY *key = pkey->pkey;

  if (key == NULL) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_NO_KEY_SET);

    return 0;

  }

  *out_ptr = OPENSSL_memdup(key->pub, 32);

  return *out_ptr == NULL ? 0 : 32;

}

static int x25519_pub_decode(EVP_PKEY *out, CBS *params, CBS *key) {

  // See RFC 8410, section 4.

  // The parameters must be omitted. Public keys have length 32.

  if (CBS_len(params) != 0) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);

    return 0;

  }

  return x25519_set_pub_raw(out, CBS_data(key), CBS_len(key));

}

static int x25519_pub_encode(CBB *out, const EVP_PKEY *pkey) {

  const X25519_KEY *key = pkey->pkey;

  // See RFC 8410, section 4.

  CBB spki, algorithm, oid, key_bitstring;

  if (!CBB_add_asn1(out, &spki, CBS_ASN1_SEQUENCE) ||

      !CBB_add_asn1(&spki, &algorithm, CBS_ASN1_SEQUENCE) ||

      !CBB_add_asn1(&algorithm, &oid, CBS_ASN1_OBJECT) ||

      !CBB_add_bytes(&oid, x25519_asn1_meth.oid, x25519_asn1_meth.oid_len) ||

      !CBB_add_asn1(&spki, &key_bitstring, CBS_ASN1_BITSTRING) ||

      !CBB_add_u8(&key_bitstring, 0 /* padding */) ||

      !CBB_add_bytes(&key_bitstring, key->pub, 32) ||

      !CBB_flush(out)) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_ENCODE_ERROR);

    return 0;

  }

  return 1;

}

static int x25519_pub_cmp(const EVP_PKEY *a, const EVP_PKEY *b) {

  const X25519_KEY *a_key = a->pkey;

  const X25519_KEY *b_key = b->pkey;

  return OPENSSL_memcmp(a_key->pub, b_key->pub, 32) == 0;

}

static int x25519_priv_decode(EVP_PKEY *out, CBS *params, CBS *key) {

  // See RFC 8410, section 7.

  // Parameters must be empty. The key is a 32-byte value wrapped in an extra

  // OCTET STRING layer.

  CBS inner;

  if (CBS_len(params) != 0 ||

      !CBS_get_asn1(key, &inner, CBS_ASN1_OCTETSTRING) ||

      CBS_len(key) != 0) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);

    return 0;

  }

  return x25519_set_priv_raw(out, CBS_data(&inner), CBS_len(&inner));

}

static int x25519_priv_encode(CBB *out, const EVP_PKEY *pkey) {

  const X25519_KEY *key = pkey->pkey;

  if (!key->has_private) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_NOT_A_PRIVATE_KEY);

    return 0;

  }

  // See RFC 8410, section 7.

  CBB pkcs8, algorithm, oid, private_key, inner;

  if (!CBB_add_asn1(out, &pkcs8, CBS_ASN1_SEQUENCE) ||

      !CBB_add_asn1_uint64(&pkcs8, 0 /* version */) ||

      !CBB_add_asn1(&pkcs8, &algorithm, CBS_ASN1_SEQUENCE) ||

      !CBB_add_asn1(&algorithm, &oid, CBS_ASN1_OBJECT) ||

      !CBB_add_bytes(&oid, x25519_asn1_meth.oid, x25519_asn1_meth.oid_len) ||

      !CBB_add_asn1(&pkcs8, &private_key, CBS_ASN1_OCTETSTRING) ||

      !CBB_add_asn1(&private_key, &inner, CBS_ASN1_OCTETSTRING) ||

      // The PKCS#8 encoding stores only the 32-byte seed which is the first 32

      // bytes of the private key.

      !CBB_add_bytes(&inner, key->priv, 32) ||

      !CBB_flush(out)) {

    OPENSSL_PUT_ERROR(EVP, EVP_R_ENCODE_ERROR);

    return 0;

  }

  return 1;

}

static int x25519_size(const EVP_PKEY *pkey) { return 32; }

static int x25519_bits(const EVP_PKEY *pkey) { return 253; }

const EVP_PKEY_ASN1_METHOD x25519_asn1_meth = {

    EVP_PKEY_X25519,

    {0x2b, 0x65, 0x6e},

    3,

    &x25519_pkey_meth,

    x25519_pub_decode,

    x25519_pub_encode,

    x25519_pub_cmp,

    x25519_priv_decode,

    x25519_priv_encode,

    x25519_set_priv_raw,

    x25519_set_pub_raw,

    x25519_get_priv_raw,

    x25519_get_pub_raw,

    x25519_set1_tls_encodedpoint,

    x25519_get1_tls_encodedpoint,

    /*pkey_opaque=*/NULL,

    x25519_size,

    x25519_bits,

    /*param_missing=*/NULL,

    /*param_copy=*/NULL,

    /*param_cmp=*/NULL,

    x25519_free,

};