/* $OpenBSD: ssh-ecdsa.c,v 1.27 2024/08/15 00:51:51 djm Exp $ */

/*

 * Copyright (c) 2000 Markus Friedl.  All rights reserved.

 * Copyright (c) 2010 Damien Miller.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include "includes.h"

#if defined(WITH_OPENSSL) && defined(OPENSSL_HAS_ECC)

#include <sys/types.h>

#include <openssl/bn.h>

#include <openssl/ec.h>

#include <openssl/ecdsa.h>

#include <openssl/evp.h>

#include <string.h>

#include "sshbuf.h"

#include "ssherr.h"

#include "digest.h"

#define SSHKEY_INTERNAL

#include "sshkey.h"

#include "openbsd-compat/openssl-compat.h"

int

sshkey_ecdsa_fixup_group(EVP_PKEY *k)

{

  int nids[] = {

    NID_X9_62_prime256v1,

    NID_secp384r1,

#ifdef OPENSSL_HAS_NISTP521

    NID_secp521r1,

#endif

    -1

  };

  int nid = -1;

  u_int i;

  const EC_GROUP *g;

  EC_KEY *ec = NULL;

  EC_GROUP *eg = NULL;

  if ((ec = EVP_PKEY_get1_EC_KEY(k)) == NULL ||

      (g = EC_KEY_get0_group(ec)) == NULL)

    goto out;

  /*

   * The group may be stored in a ASN.1 encoded private key in one of two

   * ways: as a "named group", which is reconstituted by ASN.1 object ID

   * or explicit group parameters encoded into the key blob. Only the

   * "named group" case sets the group NID for us, but we can figure

   * it out for the other case by comparing against all the groups that

   * are supported.

   */

  if ((nid = EC_GROUP_get_curve_name(g)) > 0)

    goto out;

  nid = -1;

  for (i = 0; nids[i] != -1; i++) {

    if ((eg = EC_GROUP_new_by_curve_name(nids[i])) == NULL)

      goto out;

    if (EC_GROUP_cmp(g, eg, NULL) == 0)

      break;

    EC_GROUP_free(eg);

    eg = NULL;

  }

  if (nids[i] == -1)

    goto out;

  /* Use the group with the NID attached */

  EC_GROUP_set_asn1_flag(eg, OPENSSL_EC_NAMED_CURVE);

  if (EC_KEY_set_group(ec, eg) != 1 ||

      EVP_PKEY_set1_EC_KEY(k, ec) != 1)

    goto out;

  /* success */

  nid = nids[i];

 out:

  EC_KEY_free(ec);

  EC_GROUP_free(eg);

  return nid;

}

static u_int

ssh_ecdsa_size(const struct sshkey *key)

{

  switch (key->ecdsa_nid) {

  case NID_X9_62_prime256v1:

    return 256;

  case NID_secp384r1:

    return 384;

#ifdef OPENSSL_HAS_NISTP521

  case NID_secp521r1:

    return 521;

#endif

  default:

    return 0;

  }

}

static void

ssh_ecdsa_cleanup(struct sshkey *k)

{

  EVP_PKEY_free(k->pkey);

  k->pkey = NULL;

}

static int

ssh_ecdsa_equal(const struct sshkey *a, const struct sshkey *b)

{

  if (a->pkey == NULL || b->pkey == NULL)

    return 0;

  return EVP_PKEY_cmp(a->pkey, b->pkey) == 1;

}

static int

ssh_ecdsa_serialize_public(const struct sshkey *key, struct sshbuf *b,

    enum sshkey_serialize_rep opts)

{

  int r;

  if (key->pkey == NULL)

    return SSH_ERR_INVALID_ARGUMENT;

  if ((r = sshbuf_put_cstring(b,

      sshkey_curve_nid_to_name(key->ecdsa_nid))) != 0 ||

      (r = sshbuf_put_ec_pkey(b, key->pkey)) != 0)

    return r;

  return 0;

}

static int

ssh_ecdsa_serialize_private(const struct sshkey *key, struct sshbuf *b,

    enum sshkey_serialize_rep opts)

{

  int r;

  if (!sshkey_is_cert(key)) {

    if ((r = ssh_ecdsa_serialize_public(key, b, opts)) != 0)

      return r;

  }

  if ((r = sshbuf_put_bignum2(b,

      EC_KEY_get0_private_key(EVP_PKEY_get0_EC_KEY(key->pkey)))) != 0)

    return r;

  return 0;

}

static int

ssh_ecdsa_generate(struct sshkey *k, int bits)

{

  EVP_PKEY *res = NULL;

  EVP_PKEY_CTX *ctx = NULL;

  int ret = SSH_ERR_INTERNAL_ERROR;

  if ((k->ecdsa_nid = sshkey_ecdsa_bits_to_nid(bits)) == -1)

    return SSH_ERR_KEY_LENGTH;

  if ((ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  if (EVP_PKEY_keygen_init(ctx) <= 0 ||

      EVP_PKEY_CTX_set_ec_paramgen_curve_nid(ctx, k->ecdsa_nid) <= 0 ||

      EVP_PKEY_keygen(ctx, &res) <= 0) {

    ret = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  /* success */

  k->pkey = res;

  res = NULL;

  ret = 0;

 out:

  EVP_PKEY_free(res);

  EVP_PKEY_CTX_free(ctx);

  return ret;

}

static int

ssh_ecdsa_copy_public(const struct sshkey *from, struct sshkey *to)

{

  const EC_KEY *ec_from;

  EC_KEY *ec_to = NULL;

  int ret = SSH_ERR_INTERNAL_ERROR;

  ec_from = EVP_PKEY_get0_EC_KEY(from->pkey);

  if (ec_from == NULL)

    return SSH_ERR_LIBCRYPTO_ERROR;

  to->ecdsa_nid = from->ecdsa_nid;

  if ((ec_to = EC_KEY_new_by_curve_name(from->ecdsa_nid)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  if (EC_KEY_set_public_key(ec_to,

      EC_KEY_get0_public_key(ec_from)) != 1) {

    ret = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  EVP_PKEY_free(to->pkey);

  if ((to->pkey = EVP_PKEY_new()) == NULL) {

    ret = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  if (EVP_PKEY_set1_EC_KEY(to->pkey, ec_to) != 1) {

    ret = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  ret = 0;

 out:

  EC_KEY_free(ec_to);

  return ret;

}

static int

ssh_ecdsa_deserialize_public(const char *ktype, struct sshbuf *b,

    struct sshkey *key)

{

  int r;

  char *curve = NULL;

  EVP_PKEY *pkey = NULL;

  EC_KEY *ec = NULL;

  if ((key->ecdsa_nid = sshkey_ecdsa_nid_from_name(ktype)) == -1)

    return SSH_ERR_INVALID_ARGUMENT;

  if ((r = sshbuf_get_cstring(b, &curve, NULL)) != 0)

    goto out;

  if (key->ecdsa_nid != sshkey_curve_name_to_nid(curve)) {

    r = SSH_ERR_EC_CURVE_MISMATCH;

    goto out;

  }

  if ((ec = EC_KEY_new_by_curve_name(key->ecdsa_nid)) == NULL) {

    r = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  if ((r = sshbuf_get_eckey(b, ec)) != 0)

    goto out;

  if (sshkey_ec_validate_public(EC_KEY_get0_group(ec),

      EC_KEY_get0_public_key(ec)) != 0) {

    r = SSH_ERR_KEY_INVALID_EC_VALUE;

    goto out;

  }

  if ((pkey = EVP_PKEY_new()) == NULL) {

    r = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  if (EVP_PKEY_set1_EC_KEY(pkey, ec) != 1) {

    r = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  EVP_PKEY_free(key->pkey);

  key->pkey = pkey;

  pkey = NULL;

  /* success */

  r = 0;

#ifdef DEBUG_PK

  sshkey_dump_ec_point(

      EC_KEY_get0_group(EVP_PKEY_get0_EC_KEY(key->pkey)),

      EC_KEY_get0_public_key(EVP_PKEY_get0_EC_KEY(key->pkey)));

#endif

 out:

  EC_KEY_free(ec);

  EVP_PKEY_free(pkey);

  free(curve);

  return r;

}

static int

ssh_ecdsa_deserialize_private(const char *ktype, struct sshbuf *b,

    struct sshkey *key)

{

  int r;

  BIGNUM *exponent = NULL;

  EC_KEY *ec = NULL;

  if (!sshkey_is_cert(key)) {

    if ((r = ssh_ecdsa_deserialize_public(ktype, b, key)) != 0)

      return r;

  }

  if ((r = sshbuf_get_bignum2(b, &exponent)) != 0)

    goto out;

  if ((ec = EVP_PKEY_get1_EC_KEY(key->pkey)) == NULL) {

    r = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  if (EC_KEY_set_private_key(ec, exponent) != 1) {

    r = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  if ((r = sshkey_ec_validate_private(ec)) != 0)

    goto out;

  if (EVP_PKEY_set1_EC_KEY(key->pkey, ec) != 1) {

    r = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  /* success */

  r = 0;

 out:

  BN_clear_free(exponent);

  EC_KEY_free(ec);

  return r;

}

static int

ssh_ecdsa_sign(struct sshkey *key,

    u_char **sigp, size_t *lenp,

    const u_char *data, size_t dlen,

    const char *alg, const char *sk_provider, const char *sk_pin, u_int compat)

{

  ECDSA_SIG *esig = NULL;

  unsigned char *sigb = NULL;

  const unsigned char *psig;

  const BIGNUM *sig_r, *sig_s;

  int hash_alg;

  size_t slen = 0;

  struct sshbuf *b = NULL, *bb = NULL;

  int len = 0, ret = SSH_ERR_INTERNAL_ERROR;

  if (lenp != NULL)

    *lenp = 0;

  if (sigp != NULL)

    *sigp = NULL;

  if (key == NULL || key->pkey == NULL ||

      sshkey_type_plain(key->type) != KEY_ECDSA)

    return SSH_ERR_INVALID_ARGUMENT;

  if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1)

    return SSH_ERR_INTERNAL_ERROR;

  if ((ret = sshkey_pkey_digest_sign(key->pkey, hash_alg, &sigb, &slen,

      data, dlen)) != 0)

    goto out;

  psig = sigb;

  if ((esig = d2i_ECDSA_SIG(NULL, &psig, slen)) == NULL) {

    ret = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  if ((bb = sshbuf_new()) == NULL || (b = sshbuf_new()) == NULL) {

    ret = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  ECDSA_SIG_get0(esig, &sig_r, &sig_s);

  if ((ret = sshbuf_put_bignum2(bb, sig_r)) != 0 ||

      (ret = sshbuf_put_bignum2(bb, sig_s)) != 0)

    goto out;

  if ((ret = sshbuf_put_cstring(b, sshkey_ssh_name_plain(key))) != 0 ||

      (ret = sshbuf_put_stringb(b, bb)) != 0)

    goto out;

  len = sshbuf_len(b);

  if (sigp != NULL) {

    if ((*sigp = malloc(len)) == NULL) {

      ret = SSH_ERR_ALLOC_FAIL;

      goto out;

    }

    memcpy(*sigp, sshbuf_ptr(b), len);

  }

  if (lenp != NULL)

    *lenp = len;

  ret = 0;

 out:

  freezero(sigb, slen);

  sshbuf_free(b);

  sshbuf_free(bb);

  ECDSA_SIG_free(esig);

  return ret;

}

static int

ssh_ecdsa_verify(const struct sshkey *key,

    const u_char *sig, size_t siglen,

    const u_char *data, size_t dlen, const char *alg, u_int compat,

    struct sshkey_sig_details **detailsp)

{

  ECDSA_SIG *esig = NULL;

  BIGNUM *sig_r = NULL, *sig_s = NULL;

  int hash_alg, len = 0;

  int ret = SSH_ERR_INTERNAL_ERROR;

  struct sshbuf *b = NULL, *sigbuf = NULL;

  char *ktype = NULL;

  unsigned char *sigb = NULL, *cp;

  if (key == NULL || key->pkey == NULL ||

      sshkey_type_plain(key->type) != KEY_ECDSA ||

      sig == NULL || siglen == 0)

    return SSH_ERR_INVALID_ARGUMENT;

  if ((hash_alg = sshkey_ec_nid_to_hash_alg(key->ecdsa_nid)) == -1)

    return SSH_ERR_INTERNAL_ERROR;

  /* fetch signature */

  if ((b = sshbuf_from(sig, siglen)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||

      sshbuf_froms(b, &sigbuf) != 0) {

    ret = SSH_ERR_INVALID_FORMAT;

    goto out;

  }

  if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {

    ret = SSH_ERR_KEY_TYPE_MISMATCH;

    goto out;

  }

  if (sshbuf_len(b) != 0) {

    ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;

    goto out;

  }

  /* parse signature */

  if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 ||

      sshbuf_get_bignum2(sigbuf, &sig_s) != 0) {

    ret = SSH_ERR_INVALID_FORMAT;

    goto out;

  }

  if (sshbuf_len(sigbuf) != 0) {

    ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;

    goto out;

  }

  if ((esig = ECDSA_SIG_new()) == NULL) {

    ret = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  if (!ECDSA_SIG_set0(esig, sig_r, sig_s)) {

    ret = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  sig_r = sig_s = NULL; /* transferred */

  if ((len = i2d_ECDSA_SIG(esig, NULL)) <= 0) {

    len = 0;

    ret = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  if ((sigb = calloc(1, len)) == NULL) {

    ret = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  cp = sigb; /* ASN1_item_i2d increments the pointer past the object */

  if (i2d_ECDSA_SIG(esig, &cp) != len) {

    ret = SSH_ERR_LIBCRYPTO_ERROR;

    goto out;

  }

  if ((ret = sshkey_pkey_digest_verify(key->pkey, hash_alg,

      data, dlen, sigb, len)) != 0)

    goto out;

  /* success */

 out:

  freezero(sigb, len);

  sshbuf_free(sigbuf);

  sshbuf_free(b);

  ECDSA_SIG_free(esig);

  BN_clear_free(sig_r);

  BN_clear_free(sig_s);

  free(ktype);

  return ret;

}

/* NB. not static; used by ECDSA-SK */

const struct sshkey_impl_funcs sshkey_ecdsa_funcs = {

  /* .size = */   ssh_ecdsa_size,

  /* .alloc = */    NULL,

  /* .cleanup = */  ssh_ecdsa_cleanup,

  /* .equal = */    ssh_ecdsa_equal,

  /* .ssh_serialize_public = */ ssh_ecdsa_serialize_public,

  /* .ssh_deserialize_public = */ ssh_ecdsa_deserialize_public,

  /* .ssh_serialize_private = */ ssh_ecdsa_serialize_private,

  /* .ssh_deserialize_private = */ ssh_ecdsa_deserialize_private,

  /* .generate = */ ssh_ecdsa_generate,

  /* .copy_public = */  ssh_ecdsa_copy_public,

  /* .sign = */   ssh_ecdsa_sign,

  /* .verify = */   ssh_ecdsa_verify,

};

const struct sshkey_impl sshkey_ecdsa_nistp256_impl = {

  /* .name = */   "ecdsa-sha2-nistp256",

  /* .shortname = */  "ECDSA",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ECDSA,

  /* .nid = */    NID_X9_62_prime256v1,

  /* .cert = */   0,

  /* .sigonly = */  0,

  /* .keybits = */  0,

  /* .funcs = */    &sshkey_ecdsa_funcs,

};

const struct sshkey_impl sshkey_ecdsa_nistp256_cert_impl = {

  /* .name = */   "ecdsa-sha2-nistp256-cert-v01@openssh.com",

  /* .shortname = */  "ECDSA-CERT",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ECDSA_CERT,

  /* .nid = */    NID_X9_62_prime256v1,

  /* .cert = */   1,

  /* .sigonly = */  0,

  /* .keybits = */  0,

  /* .funcs = */    &sshkey_ecdsa_funcs,

};

const struct sshkey_impl sshkey_ecdsa_nistp384_impl = {

  /* .name = */   "ecdsa-sha2-nistp384",

  /* .shortname = */  "ECDSA",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ECDSA,

  /* .nid = */    NID_secp384r1,

  /* .cert = */   0,

  /* .sigonly = */  0,

  /* .keybits = */  0,

  /* .funcs = */    &sshkey_ecdsa_funcs,

};

const struct sshkey_impl sshkey_ecdsa_nistp384_cert_impl = {

  /* .name = */   "ecdsa-sha2-nistp384-cert-v01@openssh.com",

  /* .shortname = */  "ECDSA-CERT",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ECDSA_CERT,

  /* .nid = */    NID_secp384r1,

  /* .cert = */   1,

  /* .sigonly = */  0,

  /* .keybits = */  0,

  /* .funcs = */    &sshkey_ecdsa_funcs,

};

#ifdef OPENSSL_HAS_NISTP521

const struct sshkey_impl sshkey_ecdsa_nistp521_impl = {

  /* .name = */   "ecdsa-sha2-nistp521",

  /* .shortname = */  "ECDSA",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ECDSA,

  /* .nid = */    NID_secp521r1,

  /* .cert = */   0,

  /* .sigonly = */  0,

  /* .keybits = */  0,

  /* .funcs = */    &sshkey_ecdsa_funcs,

};

const struct sshkey_impl sshkey_ecdsa_nistp521_cert_impl = {

  /* .name = */   "ecdsa-sha2-nistp521-cert-v01@openssh.com",

  /* .shortname = */  "ECDSA-CERT",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ECDSA_CERT,

  /* .nid = */    NID_secp521r1,

  /* .cert = */   1,

  /* .sigonly = */  0,

  /* .keybits = */  0,

  /* .funcs = */    &sshkey_ecdsa_funcs,

};

#endif

#endif /* WITH_OPENSSL && OPENSSL_HAS_ECC */