/* $OpenBSD: tls_server.c,v 1.52 2025/06/04 10:25:30 tb Exp $ */
/*
 * Copyright (c) 2014 Joel Sing <jsing@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 <sys/socket.h>

#include <arpa/inet.h>

#include <string.h>

#include <openssl/ec.h>
#include <openssl/err.h>
#include <openssl/ssl.h>

#include <tls.h>
#include "tls_internal.h"

struct tls *
tls_server(void)
{
        struct tls *ctx;

        if (tls_init() == -1)
                return (NULL);

        if ((ctx = tls_new()) == NULL)
                return (NULL);

        ctx->flags |= TLS_SERVER;

        return (ctx);
}

struct tls *
tls_server_conn(struct tls *ctx)
{
        struct tls *conn_ctx;

        if ((conn_ctx = tls_new()) == NULL)
                return (NULL);

        conn_ctx->flags |= TLS_SERVER_CONN;

        pthread_mutex_lock(&ctx->config->mutex);
        ctx->config->refcount++;
        pthread_mutex_unlock(&ctx->config->mutex);

        conn_ctx->config = ctx->config;
        conn_ctx->keypair = ctx->config->keypair;

        return (conn_ctx);
}

static int
tls_server_alpn_cb(SSL *ssl, const unsigned char **out, unsigned char *outlen,
    const unsigned char *in, unsigned int inlen, void *arg)
{
        struct tls *ctx = arg;

        if (SSL_select_next_proto((unsigned char**)out, outlen,
            ctx->config->alpn, ctx->config->alpn_len, in, inlen) ==
            OPENSSL_NPN_NEGOTIATED)
                return (SSL_TLSEXT_ERR_OK);

        return (SSL_TLSEXT_ERR_ALERT_FATAL);
}

static int
tls_servername_cb(SSL *ssl, int *al, void *arg)
{
        struct tls *ctx = (struct tls *)arg;
        struct tls_sni_ctx *sni_ctx;
        union tls_addr addrbuf;
        struct tls *conn_ctx;
        const char *name;
        int match;

        if ((conn_ctx = SSL_get_app_data(ssl)) == NULL)
                goto err;

        if ((name = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name)) ==
            NULL) {
                /*
                 * The servername callback gets called even when there is no
                 * TLS servername extension provided by the client. Sigh!
                 */
                return (SSL_TLSEXT_ERR_NOACK);
        }

        /*
         * Per RFC 6066 section 3: ensure that name is not an IP literal.
         *
         * While we should treat this as an error, a number of clients
         * (Python, Ruby and Safari) are not RFC compliant. To avoid handshake
         * failures, pretend that we did not receive the extension.
         */
        if (inet_pton(AF_INET, name, &addrbuf) == 1 ||
            inet_pton(AF_INET6, name, &addrbuf) == 1)
                return (SSL_TLSEXT_ERR_NOACK);

        free(conn_ctx->servername);
        if ((conn_ctx->servername = strdup(name)) == NULL)
                goto err;

        /* Find appropriate SSL context for requested servername. */
        for (sni_ctx = ctx->sni_ctx; sni_ctx != NULL; sni_ctx = sni_ctx->next) {
                if (tls_check_name(ctx, sni_ctx->ssl_cert, name,
                    &match) == -1)
                        goto err;
                if (match) {
                        conn_ctx->keypair = sni_ctx->keypair;
                        SSL_set_SSL_CTX(conn_ctx->ssl_conn, sni_ctx->ssl_ctx);
                        return (SSL_TLSEXT_ERR_OK);
                }
        }

        /* No match, use the existing context/certificate. */
        return (SSL_TLSEXT_ERR_OK);

 err:
        /*
         * There is no way to tell libssl that an internal failure occurred.
         * The only option we have is to return a fatal alert.
         */
        *al = SSL_AD_INTERNAL_ERROR;
        return (SSL_TLSEXT_ERR_ALERT_FATAL);
}

static struct tls_ticket_key *
tls_server_ticket_key(struct tls_config *config, unsigned char *keyname)
{
        struct tls_ticket_key *key = NULL;
        time_t now;
        int i;

        now = time(NULL);
        if (config->ticket_autorekey == 1) {
                if (now - 3 * (config->session_lifetime / 4) >
                    config->ticket_keys[0].time) {
                        if (tls_config_ticket_autorekey(config) == -1)
                                return (NULL);
                }
        }
        for (i = 0; i < TLS_NUM_TICKETS; i++) {
                struct tls_ticket_key *tk = &config->ticket_keys[i];
                if (now - config->session_lifetime > tk->time)
                        continue;
                if (keyname == NULL || timingsafe_memcmp(keyname,
                    tk->key_name, sizeof(tk->key_name)) == 0) {
                        key = tk;
                        break;
                }
        }
        return (key);
}

static int
tls_server_ticket_cb(SSL *ssl, unsigned char *keyname, unsigned char *iv,
    EVP_CIPHER_CTX *ctx, HMAC_CTX *hctx, int mode)
{
        struct tls_ticket_key *key;
        struct tls *tls_ctx;

        if ((tls_ctx = SSL_get_app_data(ssl)) == NULL)
                return (-1);

        if (mode == 1) {
                /* create new session */
                key = tls_server_ticket_key(tls_ctx->config, NULL);
                if (key == NULL) {
                        tls_set_errorx(tls_ctx, TLS_ERROR_UNKNOWN,
                            "no valid ticket key found");
                        return (-1);
                }

                memcpy(keyname, key->key_name, sizeof(key->key_name));
                arc4random_buf(iv, EVP_MAX_IV_LENGTH);
                if (!EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL,
                    key->aes_key, iv)) {
                        tls_set_errorx(tls_ctx, TLS_ERROR_UNKNOWN,
                            "failed to init encrypt");
                        return (-1);
                }
                if (!HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
                    EVP_sha256(), NULL)) {
                        tls_set_errorx(tls_ctx, TLS_ERROR_UNKNOWN,
                            "failed to init hmac");
                        return (-1);
                }
                return (0);
        } else {
                /* get key by name */
                key = tls_server_ticket_key(tls_ctx->config, keyname);
                if (key == NULL)
                        return (0);

                if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL,
                    key->aes_key, iv)) {
                        tls_set_errorx(tls_ctx, TLS_ERROR_UNKNOWN,
                            "failed to init decrypt");
                        return (-1);
                }
                if (!HMAC_Init_ex(hctx, key->hmac_key, sizeof(key->hmac_key),
                    EVP_sha256(), NULL)) {
                        tls_set_errorx(tls_ctx, TLS_ERROR_UNKNOWN,
                            "failed to init hmac");
                        return (-1);
                }

                /* time to renew the ticket? is it the primary key? */
                if (key != &tls_ctx->config->ticket_keys[0])
                        return (2);
                return (1);
        }
}

static int
tls_configure_server_ssl(struct tls *ctx, SSL_CTX **ssl_ctx,
    struct tls_keypair *keypair)
{
        SSL_CTX_free(*ssl_ctx);

        if ((*ssl_ctx = SSL_CTX_new(SSLv23_server_method())) == NULL) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "ssl context failure");
                goto err;
        }

        SSL_CTX_set_options(*ssl_ctx, SSL_OP_NO_CLIENT_RENEGOTIATION);

        if (SSL_CTX_set_tlsext_servername_callback(*ssl_ctx,
            tls_servername_cb) != 1) {
                tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                    "failed to set servername callback");
                goto err;
        }
        if (SSL_CTX_set_tlsext_servername_arg(*ssl_ctx, ctx) != 1) {
                tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                    "failed to set servername callback arg");
                goto err;
        }

        if (tls_configure_ssl(ctx, *ssl_ctx) != 0)
                goto err;
        if (tls_configure_ssl_keypair(ctx, *ssl_ctx, keypair, 1) != 0)
                goto err;
        if (ctx->config->verify_client != 0) {
                int verify = SSL_VERIFY_PEER;
                if (ctx->config->verify_client == 1)
                        verify |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
                if (tls_configure_ssl_verify(ctx, *ssl_ctx, verify) == -1)
                        goto err;
        }

        if (ctx->config->alpn != NULL)
                SSL_CTX_set_alpn_select_cb(*ssl_ctx, tls_server_alpn_cb,
                    ctx);

        if (ctx->config->dheparams == -1)
                SSL_CTX_set_dh_auto(*ssl_ctx, 1);
        else if (ctx->config->dheparams == 1024)
                SSL_CTX_set_dh_auto(*ssl_ctx, 2);

        if (ctx->config->ecdhecurves != NULL) {
                SSL_CTX_set_ecdh_auto(*ssl_ctx, 1);
                if (SSL_CTX_set1_groups(*ssl_ctx, ctx->config->ecdhecurves,
                    ctx->config->ecdhecurves_len) != 1) {
                        tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                            "failed to set ecdhe curves");
                        goto err;
                }
        }

        if (ctx->config->ciphers_server == 1)
                SSL_CTX_set_options(*ssl_ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);

        if (SSL_CTX_set_tlsext_status_cb(*ssl_ctx, tls_ocsp_stapling_cb) != 1) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "failed to add OCSP stapling callback");
                goto err;
        }

        if (ctx->config->session_lifetime > 0) {
                /* set the session lifetime and enable tickets */
                SSL_CTX_set_timeout(*ssl_ctx, ctx->config->session_lifetime);
                SSL_CTX_clear_options(*ssl_ctx, SSL_OP_NO_TICKET);
                if (!SSL_CTX_set_tlsext_ticket_key_cb(*ssl_ctx,
                    tls_server_ticket_cb)) {
                        tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                            "failed to set the TLS ticket callback");
                        goto err;
                }
        }

        if (SSL_CTX_set_session_id_context(*ssl_ctx, ctx->config->session_id,
            sizeof(ctx->config->session_id)) != 1) {
                tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                    "failed to set session id context");
                goto err;
        }

        return (0);

  err:
        SSL_CTX_free(*ssl_ctx);
        *ssl_ctx = NULL;

        return (-1);
}

static int
tls_configure_server_sni(struct tls *ctx)
{
        struct tls_sni_ctx **sni_ctx;
        struct tls_keypair *kp;

        if (ctx->config->keypair->next == NULL)
                return (0);

        /* Set up additional SSL contexts for SNI. */
        sni_ctx = &ctx->sni_ctx;
        for (kp = ctx->config->keypair->next; kp != NULL; kp = kp->next) {
                if ((*sni_ctx = tls_sni_ctx_new()) == NULL) {
                        tls_set_errorx(ctx, TLS_ERROR_OUT_OF_MEMORY, "out of memory");
                        goto err;
                }
                (*sni_ctx)->keypair = kp;
                if (tls_configure_server_ssl(ctx, &(*sni_ctx)->ssl_ctx, kp) == -1)
                        goto err;
                if (tls_keypair_load_cert(kp, &ctx->error,
                    &(*sni_ctx)->ssl_cert) == -1)
                        goto err;
                sni_ctx = &(*sni_ctx)->next;
        }

        return (0);

 err:
        return (-1);
}

int
tls_configure_server(struct tls *ctx)
{
        if (tls_configure_server_ssl(ctx, &ctx->ssl_ctx,
            ctx->config->keypair) == -1)
                goto err;
        if (tls_configure_server_sni(ctx) == -1)
                goto err;

        return (0);

 err:
        return (-1);
}

static struct tls *
tls_accept_common(struct tls *ctx)
{
        struct tls *conn_ctx = NULL;

        if ((ctx->flags & TLS_SERVER) == 0) {
                tls_set_errorx(ctx, TLS_ERROR_INVALID_CONTEXT,
                    "not a server context");
                goto err;
        }

        if ((conn_ctx = tls_server_conn(ctx)) == NULL) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "connection context failure");
                goto err;
        }

        if ((conn_ctx->ssl_conn = SSL_new(ctx->ssl_ctx)) == NULL) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "ssl failure");
                goto err;
        }

        if (SSL_set_app_data(conn_ctx->ssl_conn, conn_ctx) != 1) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "ssl application data failure");
                goto err;
        }

        return conn_ctx;

 err:
        tls_free(conn_ctx);

        return (NULL);
}

int
tls_accept_socket(struct tls *ctx, struct tls **cctx, int s)
{
        return (tls_accept_fds(ctx, cctx, s, s));
}

int
tls_accept_fds(struct tls *ctx, struct tls **cctx, int fd_read, int fd_write)
{
        struct tls *conn_ctx;

        if ((conn_ctx = tls_accept_common(ctx)) == NULL)
                goto err;

        if (SSL_set_rfd(conn_ctx->ssl_conn, fd_read) != 1 ||
            SSL_set_wfd(conn_ctx->ssl_conn, fd_write) != 1) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "ssl file descriptor failure");
                goto err;
        }

        *cctx = conn_ctx;

        return (0);
 err:
        tls_free(conn_ctx);
        *cctx = NULL;

        return (-1);
}

int
tls_accept_cbs(struct tls *ctx, struct tls **cctx,
    tls_read_cb read_cb, tls_write_cb write_cb, void *cb_arg)
{
        struct tls *conn_ctx;

        if ((conn_ctx = tls_accept_common(ctx)) == NULL)
                goto err;

        if (tls_set_cbs(conn_ctx, read_cb, write_cb, cb_arg) != 0)
                goto err;

        *cctx = conn_ctx;

        return (0);
 err:
        tls_free(conn_ctx);
        *cctx = NULL;

        return (-1);
}

int
tls_handshake_server(struct tls *ctx)
{
        int ssl_ret;
        int rv = -1;

        if ((ctx->flags & TLS_SERVER_CONN) == 0) {
                tls_set_errorx(ctx, TLS_ERROR_INVALID_CONTEXT,
                    "not a server connection context");
                goto err;
        }

        ctx->state |= TLS_SSL_NEEDS_SHUTDOWN;

        ERR_clear_error();
        if ((ssl_ret = SSL_accept(ctx->ssl_conn)) != 1) {
                rv = tls_ssl_error(ctx, ctx->ssl_conn, ssl_ret, "handshake");
                goto err;
        }

        ctx->state |= TLS_HANDSHAKE_COMPLETE;
        rv = 0;

 err:
        return (rv);
}