/* $OpenBSD: ssh_api.c,v 1.34 2026/03/03 09:57:25 dtucker Exp $ */
/*
 * Copyright (c) 2012 Markus Friedl.  All rights reserved.
 *
 * 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 <sys/types.h>

#include <stdio.h>
#include <stdlib.h>

#include "ssh_api.h"
#include "compat.h"
#include "log.h"
#include "authfile.h"
#include "sshkey.h"
#include "dh.h"
#include "misc.h"
#include "ssh2.h"
#include "version.h"
#include "myproposal.h"
#include "ssherr.h"
#include "sshbuf.h"

#include <string.h>

int     _ssh_exchange_banner(struct ssh *);
int     _ssh_send_banner(struct ssh *, struct sshbuf *);
int     _ssh_read_banner(struct ssh *, struct sshbuf *);
int     _ssh_order_hostkeyalgs(struct ssh *);
int     _ssh_verify_host_key(struct sshkey *, struct ssh *);
struct sshkey *_ssh_host_public_key(int, int, struct ssh *);
struct sshkey *_ssh_host_private_key(int, int, struct ssh *);
int     _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *,
    u_char **, size_t *, const u_char *, size_t, const char *);

/*
 * stubs for privsep calls in the server side implementation of kex.
 */
int     mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
    const u_char *, u_int, const char *, const char *, const char *, u_int);

#ifdef WITH_OPENSSL
DH      *mm_choose_dh(int, int, int);
#endif

int
mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
    const u_char *data, u_int datalen, const char *alg,
    const char *sk_provider, const char *sk_pin, u_int compat)
{
        size_t slen = 0;
        int ret;

        ret = sshkey_sign(key, sigp, &slen, data, datalen, alg,
            sk_provider, sk_pin, compat);
        *lenp = slen;
        return ret;
}

#ifdef WITH_OPENSSL
DH *
mm_choose_dh(int min, int nbits, int max)
{
        return choose_dh(min, nbits, max);
}
#endif

/* API */

int
ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
{
        char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
        char *populated[PROPOSAL_MAX];
        struct ssh *ssh;
        char **proposal;
        static int called;
        int r;

        if (!called) {
                called = 1;
        }

        if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if (is_server)
                ssh_packet_set_server(ssh);

        /* Initialize key exchange */
        proposal = kex_params ? kex_params->proposal : myproposal;
        kex_proposal_populate_entries(ssh, populated,
            proposal[PROPOSAL_KEX_ALGS],
            proposal[PROPOSAL_ENC_ALGS_CTOS],
            proposal[PROPOSAL_MAC_ALGS_CTOS],
            proposal[PROPOSAL_COMP_ALGS_CTOS],
            proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]);
        r = kex_ready(ssh, populated);
        kex_proposal_free_entries(populated);
        if (r != 0) {
                ssh_free(ssh);
                return r;
        }

        ssh->kex->server = is_server;
        if (is_server) {
#ifdef WITH_OPENSSL
                ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
                ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
                ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
                ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
                ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
                ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
                ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
                ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
#endif /* WITH_OPENSSL */
                ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server;
                ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
                ssh->kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_server;
                ssh->kex->load_host_public_key=&_ssh_host_public_key;
                ssh->kex->load_host_private_key=&_ssh_host_private_key;
                ssh->kex->sign=&_ssh_host_key_sign;
        } else {
#ifdef WITH_OPENSSL
                ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
                ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
                ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
                ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
                ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
                ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
                ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
                ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
#endif /* WITH_OPENSSL */
                ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
                ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
                ssh->kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_client;
                ssh->kex->verify_host_key =&_ssh_verify_host_key;
        }
        *sshp = ssh;
        return 0;
}

void
ssh_free(struct ssh *ssh)
{
        struct key_entry *k;

        if (ssh == NULL)
                return;

        /*
         * we've only created the public keys variants in case we
         * are a acting as a server.
         */
        while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
                TAILQ_REMOVE(&ssh->public_keys, k, next);
                if (ssh->kex && ssh->kex->server)
                        sshkey_free(k->key);
                free(k);
        }
        while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
                TAILQ_REMOVE(&ssh->private_keys, k, next);
                free(k);
        }
        ssh_packet_close(ssh);
        free(ssh);
}

void
ssh_set_app_data(struct ssh *ssh, void *app_data)
{
        ssh->app_data = app_data;
}

void *
ssh_get_app_data(struct ssh *ssh)
{
        return ssh->app_data;
}

/* Returns < 0 on error, 0 otherwise */
int
ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
{
        struct sshkey *pubkey = NULL;
        struct key_entry *k = NULL, *k_prv = NULL;
        int r;

        if (ssh->kex->server) {
                if ((r = sshkey_from_private(key, &pubkey)) != 0)
                        return r;
                if ((k = malloc(sizeof(*k))) == NULL ||
                    (k_prv = malloc(sizeof(*k_prv))) == NULL) {
                        free(k);
                        sshkey_free(pubkey);
                        return SSH_ERR_ALLOC_FAIL;
                }
                k_prv->key = key;
                TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);

                /* add the public key, too */
                k->key = pubkey;
                TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
                r = 0;
        } else {
                if ((k = malloc(sizeof(*k))) == NULL)
                        return SSH_ERR_ALLOC_FAIL;
                k->key = key;
                TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
                r = 0;
        }

        return r;
}

int
ssh_set_verify_host_key_callback(struct ssh *ssh,
    int (*cb)(struct sshkey *, struct ssh *))
{
        if (cb == NULL || ssh->kex == NULL)
                return SSH_ERR_INVALID_ARGUMENT;

        ssh->kex->verify_host_key = cb;

        return 0;
}

int
ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
{
        return sshbuf_put(ssh_packet_get_input(ssh), data, len);
}

int
ssh_packet_next(struct ssh *ssh, u_char *typep)
{
        int r;
        uint32_t seqnr;
        u_char type;

        /*
         * Try to read a packet. Return SSH_MSG_NONE if no packet or not
         * enough data.
         */
        *typep = SSH_MSG_NONE;
        if (sshbuf_len(ssh->kex->client_version) == 0 ||
            sshbuf_len(ssh->kex->server_version) == 0)
                return _ssh_exchange_banner(ssh);
        /*
         * If we enough data and a dispatch function then
         * call the function and get the next packet.
         * Otherwise return the packet type to the caller so it
         * can decide how to go on.
         *
         * We will only call the dispatch function for:
         *     20-29    Algorithm negotiation
         *     30-49    Key exchange method specific (numbers can be reused for
         *              different authentication methods)
         */
        for (;;) {
                if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
                        return r;
                if (type > 0 && type < DISPATCH_MAX &&
                    type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
                    ssh->dispatch[type] != NULL) {
                        if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
                                return r;
                } else {
                        *typep = type;
                        return 0;
                }
        }
}

const u_char *
ssh_packet_payload(struct ssh *ssh, size_t *lenp)
{
        return sshpkt_ptr(ssh, lenp);
}

int
ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
{
        int r;

        if ((r = sshpkt_start(ssh, type)) != 0 ||
            (r = sshpkt_put(ssh, data, len)) != 0 ||
            (r = sshpkt_send(ssh)) != 0)
                return r;
        return 0;
}

const u_char *
ssh_output_ptr(struct ssh *ssh, size_t *len)
{
        struct sshbuf *output = ssh_packet_get_output(ssh);

        *len = sshbuf_len(output);
        return sshbuf_ptr(output);
}

int
ssh_output_consume(struct ssh *ssh, size_t len)
{
        return sshbuf_consume(ssh_packet_get_output(ssh), len);
}

int
ssh_output_space(struct ssh *ssh, size_t len)
{
        return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
}

int
ssh_input_space(struct ssh *ssh, size_t len)
{
        return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
}

/* Read other side's version identification. */
int
_ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
{
        struct sshbuf *input = ssh_packet_get_input(ssh);
        const char *mismatch = "Protocol mismatch.\r\n";
        const u_char *s = sshbuf_ptr(input);
        u_char c;
        char *cp = NULL, *remote_version = NULL;
        int r = 0, remote_major, remote_minor, expect_nl;
        size_t n, j;

        for (j = n = 0;;) {
                sshbuf_reset(banner);
                expect_nl = 0;
                for (;;) {
                        if (j >= sshbuf_len(input))
                                return 0; /* insufficient data in input buf */
                        c = s[j++];
                        if (c == '\r') {
                                expect_nl = 1;
                                continue;
                        }
                        if (c == '\n')
                                break;
                        if (expect_nl)
                                goto bad;
                        if ((r = sshbuf_put_u8(banner, c)) != 0)
                                return r;
                        if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
                                goto bad;
                }
                if (sshbuf_len(banner) >= 4 &&
                    memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
                        break;
                debug_f("%.*s", (int)sshbuf_len(banner),
                    sshbuf_ptr(banner));
                /* Accept lines before banner only on client */
                if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
  bad:
                        if ((r = sshbuf_put(ssh_packet_get_output(ssh),
                            mismatch, strlen(mismatch))) != 0)
                                return r;
                        return SSH_ERR_NO_PROTOCOL_VERSION;
                }
        }
        if ((r = sshbuf_consume(input, j)) != 0)
                return r;

        /* XXX remote version must be the same size as banner for sscanf */
        if ((cp = sshbuf_dup_string(banner)) == NULL ||
            (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }

        /*
         * Check that the versions match.  In future this might accept
         * several versions and set appropriate flags to handle them.
         */
        if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
            &remote_major, &remote_minor, remote_version) != 3) {
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        debug("Remote protocol version %d.%d, remote software version %.100s",
            remote_major, remote_minor, remote_version);

        compat_banner(ssh, remote_version);
        if  (remote_major == 1 && remote_minor == 99) {
                remote_major = 2;
                remote_minor = 0;
        }
        if (remote_major != 2)
                r = SSH_ERR_PROTOCOL_MISMATCH;

        debug("Remote version string %.100s", cp);
 out:
        free(cp);
        free(remote_version);
        return r;
}

/* Send our own protocol version identification. */
int
_ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
{
        char *cp;
        int r;

        if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
                return r;
        if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
                return r;
        /* Remove trailing \r\n */
        if ((r = sshbuf_consume_end(banner, 2)) != 0)
                return r;
        if ((cp = sshbuf_dup_string(banner)) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        debug("Local version string %.100s", cp);
        free(cp);
        return 0;
}

int
_ssh_exchange_banner(struct ssh *ssh)
{
        struct kex *kex = ssh->kex;
        int r;

        /*
         * if _ssh_read_banner() cannot parse a full version string
         * it will return NULL and we end up calling it again.
         */

        r = 0;
        if (kex->server) {
                if (sshbuf_len(ssh->kex->server_version) == 0)
                        r = _ssh_send_banner(ssh, ssh->kex->server_version);
                if (r == 0 &&
                    sshbuf_len(ssh->kex->server_version) != 0 &&
                    sshbuf_len(ssh->kex->client_version) == 0)
                        r = _ssh_read_banner(ssh, ssh->kex->client_version);
        } else {
                if (sshbuf_len(ssh->kex->server_version) == 0)
                        r = _ssh_read_banner(ssh, ssh->kex->server_version);
                if (r == 0 &&
                    sshbuf_len(ssh->kex->server_version) != 0 &&
                    sshbuf_len(ssh->kex->client_version) == 0)
                        r = _ssh_send_banner(ssh, ssh->kex->client_version);
        }
        if (r != 0)
                return r;
        /* start initial kex as soon as we have exchanged the banners */
        if (sshbuf_len(ssh->kex->server_version) != 0 &&
            sshbuf_len(ssh->kex->client_version) != 0) {
                if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
                    (r = kex_send_kexinit(ssh)) != 0)
                        return r;
        }
        return 0;
}

struct sshkey *
_ssh_host_public_key(int type, int nid, struct ssh *ssh)
{
        struct key_entry *k;

        debug3_f("need %d", type);
        TAILQ_FOREACH(k, &ssh->public_keys, next) {
                debug3_f("check %s", sshkey_type(k->key));
                if (k->key->type == type &&
                    (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
                        return (k->key);
        }
        return (NULL);
}

struct sshkey *
_ssh_host_private_key(int type, int nid, struct ssh *ssh)
{
        struct key_entry *k;

        debug3_f("need %d", type);
        TAILQ_FOREACH(k, &ssh->private_keys, next) {
                debug3_f("check %s", sshkey_type(k->key));
                if (k->key->type == type &&
                    (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
                        return (k->key);
        }
        return (NULL);
}

int
_ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
{
        struct key_entry *k;

        debug3_f("need %s", sshkey_type(hostkey));
        TAILQ_FOREACH(k, &ssh->public_keys, next) {
                debug3_f("check %s", sshkey_type(k->key));
                if (sshkey_equal_public(hostkey, k->key))
                        return (0);     /* ok */
        }
        return (-1);    /* failed */
}

/* offer hostkey algorithms in kexinit depending on registered keys */
int
_ssh_order_hostkeyalgs(struct ssh *ssh)
{
        struct key_entry *k;
        char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
        char **proposal;
        size_t maxlen;
        int ktype, nid, r;

        /* XXX we de-serialize ssh->kex->my, modify it, and change it */
        if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
                return r;
        orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
        if ((oavail = avail = strdup(orig)) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        maxlen = strlen(avail) + 1;
        if ((replace = calloc(1, maxlen)) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        *replace = '\0';
        while ((alg = strsep(&avail, ",")) && *alg != '\0') {
                if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
                        continue;
                nid = sshkey_ecdsa_nid_from_name(alg);
                TAILQ_FOREACH(k, &ssh->public_keys, next) {
                        if (k->key->type != ktype &&
                            (!sshkey_is_cert(k->key) ||
                            k->key->type != sshkey_type_plain(ktype)))
                                continue;
                        if (sshkey_type_plain(k->key->type) == KEY_ECDSA &&
                            k->key->ecdsa_nid != nid)
                                continue;
                        /* Candidate */
                        if (*replace != '\0')
                                strlcat(replace, ",", maxlen);
                        strlcat(replace, alg, maxlen);
                        break;
                }
        }
        if (*replace != '\0') {
                debug2_f("orig/%d    %s", ssh->kex->server, orig);
                debug2_f("replace/%d %s", ssh->kex->server, replace);
                free(orig);
                proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
                replace = NULL; /* owned by proposal */
                r = kex_prop2buf(ssh->kex->my, proposal);
        }
 out:
        free(oavail);
        free(replace);
        kex_prop_free(proposal);
        return r;
}

int
_ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
    struct sshkey *pubkey, u_char **signature, size_t *slen,
    const u_char *data, size_t dlen, const char *alg)
{
        return sshkey_sign(privkey, signature, slen, data, dlen,
            alg, NULL, NULL, ssh->compat);
}