/* $OpenBSD: ssh-ed25519.c,v 1.20 2025/07/24 06:12:08 djm Exp $ */

/*

 * Copyright (c) 2013 Markus Friedl <markus@openbsd.org>

 *

 * Permission to use, copy, modify, and 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 "includes.h"

#include <sys/types.h>

#include <limits.h>

#include "crypto_api.h"

#include <string.h>

#include <stdarg.h>

#include "log.h"

#include "sshbuf.h"

#define SSHKEY_INTERNAL

#include "sshkey.h"

#include "ssherr.h"

#include "ssh.h"

static void

ssh_ed25519_cleanup(struct sshkey *k)

{

  freezero(k->ed25519_pk, ED25519_PK_SZ);

  freezero(k->ed25519_sk, ED25519_SK_SZ);

  k->ed25519_pk = NULL;

  k->ed25519_sk = NULL;

}

static int

ssh_ed25519_equal(const struct sshkey *a, const struct sshkey *b)

{

  if (a->ed25519_pk == NULL || b->ed25519_pk == NULL)

    return 0;

  if (memcmp(a->ed25519_pk, b->ed25519_pk, ED25519_PK_SZ) != 0)

    return 0;

  return 1;

}

static int

ssh_ed25519_serialize_public(const struct sshkey *key, struct sshbuf *b,

    enum sshkey_serialize_rep opts)

{

  int r;

  if (key->ed25519_pk == NULL)

    return SSH_ERR_INVALID_ARGUMENT;

  if ((r = sshbuf_put_string(b, key->ed25519_pk, ED25519_PK_SZ)) != 0)

    return r;

  return 0;

}

static int

ssh_ed25519_serialize_private(const struct sshkey *key, struct sshbuf *b,

    enum sshkey_serialize_rep opts)

{

  int r;

  if ((r = sshbuf_put_string(b, key->ed25519_pk, ED25519_PK_SZ)) != 0 ||

      (r = sshbuf_put_string(b, key->ed25519_sk, ED25519_SK_SZ)) != 0)

    return r;

  return 0;

}

static int

ssh_ed25519_generate(struct sshkey *k, int bits)

{

  if ((k->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL ||

      (k->ed25519_sk = malloc(ED25519_SK_SZ)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  crypto_sign_ed25519_keypair(k->ed25519_pk, k->ed25519_sk);

  return 0;

}

static int

ssh_ed25519_copy_public(const struct sshkey *from, struct sshkey *to)

{

  if (from->ed25519_pk == NULL)

    return 0; /* XXX SSH_ERR_INTERNAL_ERROR ? */

  if ((to->ed25519_pk = malloc(ED25519_PK_SZ)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  memcpy(to->ed25519_pk, from->ed25519_pk, ED25519_PK_SZ);

  return 0;

}

static int

ssh_ed25519_deserialize_public(const char *ktype, struct sshbuf *b,

    struct sshkey *key)

{

  u_char *pk = NULL;

  size_t len = 0;

  int r;

  if ((r = sshbuf_get_string(b, &pk, &len)) != 0)

    return r;

  if (len != ED25519_PK_SZ) {

    freezero(pk, len);

    return SSH_ERR_INVALID_FORMAT;

  }

  key->ed25519_pk = pk;

  return 0;

}

static int

ssh_ed25519_deserialize_private(const char *ktype, struct sshbuf *b,

    struct sshkey *key)

{

  int r;

  size_t sklen = 0;

  u_char *ed25519_sk = NULL;

  if ((r = ssh_ed25519_deserialize_public(NULL, b, key)) != 0)

    goto out;

  if ((r = sshbuf_get_string(b, &ed25519_sk, &sklen)) != 0)

    goto out;

  if (sklen != ED25519_SK_SZ) {

    r = SSH_ERR_INVALID_FORMAT;

    goto out;

  }

  key->ed25519_sk = ed25519_sk;

  ed25519_sk = NULL; /* transferred */

  /* success */

  r = 0;

 out:

  freezero(ed25519_sk, sklen);

  return r;

}

static int

ssh_ed25519_sign(struct sshkey *key,

    u_char **sigp, size_t *lenp,

    const u_char *data, size_t datalen,

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

{

  u_char *sig = NULL;

  size_t slen = 0;

  unsigned long long smlen;

  int r, ret;

  if (lenp != NULL)

    *lenp = 0;

  if (sigp != NULL)

    *sigp = NULL;

  if (key == NULL ||

      sshkey_type_plain(key->type) != KEY_ED25519 ||

      key->ed25519_sk == NULL ||

      datalen >= INT_MAX - crypto_sign_ed25519_BYTES)

    return SSH_ERR_INVALID_ARGUMENT;

  smlen = slen = datalen + crypto_sign_ed25519_BYTES;

  if ((sig = malloc(slen)) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  if ((ret = crypto_sign_ed25519(sig, &smlen, data, datalen,

      key->ed25519_sk)) != 0 || smlen <= datalen) {

    r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */

    goto out;

  }

  if ((r = ssh_ed25519_encode_store_sig(sig, smlen - datalen,

      sigp, lenp)) != 0)

    goto out;

  /* success */

  r = 0;

 out:

  freezero(sig, slen);

  return r;

}

int

ssh_ed25519_encode_store_sig(const u_char *sig, size_t slen,

    u_char **sigp, size_t *lenp)

{

  struct sshbuf *b = NULL;

  int r = -1;

  size_t len;

  if (lenp != NULL)

    *lenp = 0;

  if (sigp != NULL)

    *sigp = NULL;

  if (slen != crypto_sign_ed25519_BYTES)

    return SSH_ERR_INVALID_ARGUMENT;

  /* encode signature */

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

    r = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  if ((r = sshbuf_put_cstring(b, "ssh-ed25519")) != 0 ||

      (r = sshbuf_put_string(b, sig, slen)) != 0)

    goto out;

  len = sshbuf_len(b);

  if (sigp != NULL) {

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

      r = SSH_ERR_ALLOC_FAIL;

      goto out;

    }

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

  }

  if (lenp != NULL)

    *lenp = len;

  /* success */

  r = 0;

 out:

  sshbuf_free(b);

  return r;

}

static int

ssh_ed25519_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)

{

  struct sshbuf *b = NULL;

  char *ktype = NULL;

  const u_char *sigblob;

  u_char *sm = NULL, *m = NULL;

  size_t len;

  unsigned long long smlen = 0, mlen = 0;

  int r, ret;

  if (key == NULL ||

      sshkey_type_plain(key->type) != KEY_ED25519 ||

      key->ed25519_pk == NULL ||

      dlen >= INT_MAX - crypto_sign_ed25519_BYTES ||

      sig == NULL || siglen == 0)

    return SSH_ERR_INVALID_ARGUMENT;

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

    return SSH_ERR_ALLOC_FAIL;

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

      (r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)

    goto out;

  if (strcmp("ssh-ed25519", ktype) != 0) {

    r = SSH_ERR_KEY_TYPE_MISMATCH;

    goto out;

  }

  if (sshbuf_len(b) != 0) {

    r = SSH_ERR_UNEXPECTED_TRAILING_DATA;

    goto out;

  }

  if (len > crypto_sign_ed25519_BYTES) {

    r = SSH_ERR_INVALID_FORMAT;

    goto out;

  }

  if (dlen >= SIZE_MAX - len) {

    r = SSH_ERR_INVALID_ARGUMENT;

    goto out;

  }

  smlen = len + dlen;

  mlen = smlen;

  if ((sm = malloc(smlen)) == NULL || (m = malloc(mlen)) == NULL) {

    r = SSH_ERR_ALLOC_FAIL;

    goto out;

  }

  memcpy(sm, sigblob, len);

  memcpy(sm+len, data, dlen);

  if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,

      key->ed25519_pk)) != 0) {

    debug2_f("crypto_sign_ed25519_open failed: %d", ret);

  }

  if (ret != 0 || mlen != dlen) {

    r = SSH_ERR_SIGNATURE_INVALID;

    goto out;

  }

  /* XXX compare 'm' and 'data' ? */

  /* success */

  r = 0;

 out:

  if (sm != NULL)

    freezero(sm, smlen);

  if (m != NULL)

    freezero(m, smlen); /* NB mlen may be invalid if r != 0 */

  sshbuf_free(b);

  free(ktype);

  return r;

}

/* NB. not static; used by ED25519-SK */

const struct sshkey_impl_funcs sshkey_ed25519_funcs = {

  /* .size = */   NULL,

  /* .alloc = */    NULL,

  /* .cleanup = */  ssh_ed25519_cleanup,

  /* .equal = */    ssh_ed25519_equal,

  /* .ssh_serialize_public = */ ssh_ed25519_serialize_public,

  /* .ssh_deserialize_public = */ ssh_ed25519_deserialize_public,

  /* .ssh_serialize_private = */ ssh_ed25519_serialize_private,

  /* .ssh_deserialize_private = */ ssh_ed25519_deserialize_private,

  /* .generate = */ ssh_ed25519_generate,

  /* .copy_public = */  ssh_ed25519_copy_public,

  /* .sign = */   ssh_ed25519_sign,

  /* .verify = */   ssh_ed25519_verify,

};

const struct sshkey_impl sshkey_ed25519_impl = {

  /* .name = */   "ssh-ed25519",

  /* .shortname = */  "ED25519",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ED25519,

  /* .nid = */    0,

  /* .cert = */   0,

  /* .sigonly = */  0,

  /* .keybits = */  256,

  /* .funcs = */    &sshkey_ed25519_funcs,

};

const struct sshkey_impl sshkey_ed25519_cert_impl = {

  /* .name = */   "ssh-ed25519-cert-v01@openssh.com",

  /* .shortname = */  "ED25519-CERT",

  /* .sigalg = */   NULL,

  /* .type = */   KEY_ED25519_CERT,

  /* .nid = */    0,

  /* .cert = */   1,

  /* .sigonly = */  0,

  /* .keybits = */  256,

  /* .funcs = */    &sshkey_ed25519_funcs,

};