/* $OpenBSD: kex-names.c,v 1.1 2024/05/17 00:32:32 djm Exp $ */

/*

 * Copyright (c) 2000, 2001 Markus Friedl.  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"

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <signal.h>

#ifdef WITH_OPENSSL

#include <openssl/crypto.h>

#include <openssl/evp.h>

#endif

#include "kex.h"

#include "log.h"

#include "match.h"

#include "digest.h"

#include "misc.h"

#include "ssherr.h"

#include "xmalloc.h"

struct kexalg {

  char *name;

  u_int type;

  int ec_nid;

  int hash_alg;

};

static const struct kexalg kexalgs[] = {

#ifdef WITH_OPENSSL

  { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },

  { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },

  { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },

  { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },

  { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 },

  { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 },

#ifdef HAVE_EVP_SHA256

  { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 },

#endif /* HAVE_EVP_SHA256 */

#ifdef OPENSSL_HAS_ECC

  { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,

      NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },

  { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,

      SSH_DIGEST_SHA384 },

# ifdef OPENSSL_HAS_NISTP521

  { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,

      SSH_DIGEST_SHA512 },

# endif /* OPENSSL_HAS_NISTP521 */

#endif /* OPENSSL_HAS_ECC */

#endif /* WITH_OPENSSL */

#if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL)

  { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },

  { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 },

#ifdef USE_SNTRUP761X25519

  { KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,

      SSH_DIGEST_SHA512 },

#endif

#endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */

  { NULL, 0, -1, -1},

};

char *

kex_alg_list(char sep)

{

  char *ret = NULL, *tmp;

  size_t nlen, rlen = 0;

  const struct kexalg *k;

  for (k = kexalgs; k->name != NULL; k++) {

    if (ret != NULL)

      ret[rlen++] = sep;

    nlen = strlen(k->name);

    if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {

      free(ret);

      return NULL;

    }

    ret = tmp;

    memcpy(ret + rlen, k->name, nlen + 1);

    rlen += nlen;

  }

  return ret;

}

static const struct kexalg *

kex_alg_by_name(const char *name)

{

  const struct kexalg *k;

  for (k = kexalgs; k->name != NULL; k++) {

    if (strcmp(k->name, name) == 0)

      return k;

  }

  return NULL;

}

int

kex_name_valid(const char *name)

{

  return kex_alg_by_name(name) != NULL;

}

u_int

kex_type_from_name(const char *name)

{

  const struct kexalg *k;

  if ((k = kex_alg_by_name(name)) == NULL)

    return 0;

  return k->type;

}

int

kex_hash_from_name(const char *name)

{

  const struct kexalg *k;

  if ((k = kex_alg_by_name(name)) == NULL)

    return -1;

  return k->hash_alg;

}

int

kex_nid_from_name(const char *name)

{

  const struct kexalg *k;

  if ((k = kex_alg_by_name(name)) == NULL)

    return -1;

  return k->ec_nid;

}

/* Validate KEX method name list */

int

kex_names_valid(const char *names)

{

  char *s, *cp, *p;

  if (names == NULL || strcmp(names, "") == 0)

    return 0;

  if ((s = cp = strdup(names)) == NULL)

    return 0;

  for ((p = strsep(&cp, ",")); p && *p != '\0';

      (p = strsep(&cp, ","))) {

    if (kex_alg_by_name(p) == NULL) {

      error("Unsupported KEX algorithm \"%.100s\"", p);

      free(s);

      return 0;

    }

  }

  debug3("kex names ok: [%s]", names);

  free(s);

  return 1;

}

/* returns non-zero if proposal contains any algorithm from algs */

int

kex_has_any_alg(const char *proposal, const char *algs)

{

  char *cp;

  if ((cp = match_list(proposal, algs, NULL)) == NULL)

    return 0;

  free(cp);

  return 1;

}

/*

 * Concatenate algorithm names, avoiding duplicates in the process.

 * Caller must free returned string.

 */

char *

kex_names_cat(const char *a, const char *b)

{

  char *ret = NULL, *tmp = NULL, *cp, *p;

  size_t len;

  if (a == NULL || *a == '\0')

    return strdup(b);

  if (b == NULL || *b == '\0')

    return strdup(a);

  if (strlen(b) > 1024*1024)

    return NULL;

  len = strlen(a) + strlen(b) + 2;

  if ((tmp = cp = strdup(b)) == NULL ||

      (ret = calloc(1, len)) == NULL) {

    free(tmp);

    return NULL;

  }

  strlcpy(ret, a, len);

  for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) {

    if (kex_has_any_alg(ret, p))

      continue; /* Algorithm already present */

    if (strlcat(ret, ",", len) >= len ||

        strlcat(ret, p, len) >= len) {

      free(tmp);

      free(ret);

      return NULL; /* Shouldn't happen */

    }

  }

  free(tmp);

  return ret;

}

/*

 * Assemble a list of algorithms from a default list and a string from a

 * configuration file. The user-provided string may begin with '+' to

 * indicate that it should be appended to the default, '-' that the

 * specified names should be removed, or '^' that they should be placed

 * at the head.

 */

int

kex_assemble_names(char **listp, const char *def, const char *all)

{

  char *cp, *tmp, *patterns;

  char *list = NULL, *ret = NULL, *matching = NULL, *opatterns = NULL;

  int r = SSH_ERR_INTERNAL_ERROR;

  if (listp == NULL || def == NULL || all == NULL)

    return SSH_ERR_INVALID_ARGUMENT;

  if (*listp == NULL || **listp == '\0') {

    if ((*listp = strdup(def)) == NULL)

      return SSH_ERR_ALLOC_FAIL;

    return 0;

  }

  list = *listp;

  *listp = NULL;

  if (*list == '+') {

    /* Append names to default list */

    if ((tmp = kex_names_cat(def, list + 1)) == NULL) {

      r = SSH_ERR_ALLOC_FAIL;

      goto fail;

    }

    free(list);

    list = tmp;

  } else if (*list == '-') {

    /* Remove names from default list */

    if ((*listp = match_filter_denylist(def, list + 1)) == NULL) {

      r = SSH_ERR_ALLOC_FAIL;

      goto fail;

    }

    free(list);

    /* filtering has already been done */

    return 0;

  } else if (*list == '^') {

    /* Place names at head of default list */

    if ((tmp = kex_names_cat(list + 1, def)) == NULL) {

      r = SSH_ERR_ALLOC_FAIL;

      goto fail;

    }

    free(list);

    list = tmp;

  } else {

    /* Explicit list, overrides default - just use "list" as is */

  }

  /*

   * The supplied names may be a pattern-list. For the -list case,

   * the patterns are applied above. For the +list and explicit list

   * cases we need to do it now.

   */

  ret = NULL;

  if ((patterns = opatterns = strdup(list)) == NULL) {

    r = SSH_ERR_ALLOC_FAIL;

    goto fail;

  }

  /* Apply positive (i.e. non-negated) patterns from the list */

  while ((cp = strsep(&patterns, ",")) != NULL) {

    if (*cp == '!') {

      /* negated matches are not supported here */

      r = SSH_ERR_INVALID_ARGUMENT;

      goto fail;

    }

    free(matching);

    if ((matching = match_filter_allowlist(all, cp)) == NULL) {

      r = SSH_ERR_ALLOC_FAIL;

      goto fail;

    }

    if ((tmp = kex_names_cat(ret, matching)) == NULL) {

      r = SSH_ERR_ALLOC_FAIL;

      goto fail;

    }

    free(ret);

    ret = tmp;

  }

  if (ret == NULL || *ret == '\0') {

    /* An empty name-list is an error */

    /* XXX better error code? */

    r = SSH_ERR_INVALID_ARGUMENT;

    goto fail;

  }

  /* success */

  *listp = ret;

  ret = NULL;

  r = 0;

 fail:

  free(matching);

  free(opatterns);

  free(list);

  free(ret);

  return r;

}