/* $OpenBSD: kex-names.c,v 1.7 2026/02/14 00:18:34 jsg 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 <stdio.h>
#include <stdlib.h>
#include <string.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"

struct kexalg {
        char *name;
        u_int type;
        int ec_nid;
        int hash_alg;
        int pq_alg;
};
static const struct kexalg kexalgs[] = {
#ifdef WITH_OPENSSL
        { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1, KEX_NOT_PQ },
        { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1, KEX_NOT_PQ },
        { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256, KEX_NOT_PQ },
        { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512, KEX_NOT_PQ },
        { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512, KEX_NOT_PQ },
        { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1, KEX_NOT_PQ },
        { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256, KEX_NOT_PQ },
        { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2,
            NID_X9_62_prime256v1, SSH_DIGEST_SHA256, KEX_NOT_PQ },
        { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1,
            SSH_DIGEST_SHA384, KEX_NOT_PQ },
        { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1,
            SSH_DIGEST_SHA512, KEX_NOT_PQ },
#endif
        { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0,
            SSH_DIGEST_SHA256, KEX_NOT_PQ },
        { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0,
            SSH_DIGEST_SHA256, KEX_NOT_PQ },
        { KEX_SNTRUP761X25519_SHA512, KEX_KEM_SNTRUP761X25519_SHA512, 0,
            SSH_DIGEST_SHA512, KEX_IS_PQ },
        { KEX_SNTRUP761X25519_SHA512_OLD, KEX_KEM_SNTRUP761X25519_SHA512, 0,
            SSH_DIGEST_SHA512, KEX_IS_PQ },
        { KEX_MLKEM768X25519_SHA256, KEX_KEM_MLKEM768X25519_SHA256, 0,
            SSH_DIGEST_SHA256, KEX_IS_PQ },
        { NULL, 0, -1, -1, 0},
};

char *
kex_alg_list(char sep)
{
        char *ret = NULL;
        const struct kexalg *k;
        char sep_str[2] = {sep, '\0'};

        for (k = kexalgs; k->name != NULL; k++)
                xextendf(&ret, sep_str, "%s", k->name);

        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;
}

int
kex_is_pq_from_name(const char *name)
{
        const struct kexalg *k;

        if ((k = kex_alg_by_name(name)) == NULL)
                return 0;
        return k->pq_alg == KEX_IS_PQ;
}

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;
}