/* $OpenBSD: tls_client.c,v 1.51 2024/03/26 08:54:48 joshua 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/types.h>
#include <sys/socket.h>
#include <sys/stat.h>

#include <arpa/inet.h>
#include <netinet/in.h>

#include <limits.h>
#include <netdb.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <openssl/err.h>
#include <openssl/x509.h>

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

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

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

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

        ctx->flags |= TLS_CLIENT;

        return (ctx);
}

int
tls_connect(struct tls *ctx, const char *host, const char *port)
{
        return tls_connect_servername(ctx, host, port, NULL);
}

int
tls_connect_servername(struct tls *ctx, const char *host, const char *port,
    const char *servername)
{
        struct addrinfo hints, *res, *res0;
        const char *h = NULL, *p = NULL;
        char *hs = NULL, *ps = NULL;
        int rv = -1, s = -1, ret;

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

        if (host == NULL) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "host not specified");
                goto err;
        }

        /* If port is NULL, try to extract a port from the specified host. */
        if (port == NULL) {
                ret = tls_host_port(host, &hs, &ps);
                if (ret == -1) {
                        tls_set_errorx(ctx, TLS_ERROR_OUT_OF_MEMORY, "out of memory");
                        goto err;
                }
                if (ret != 0) {
                        tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "no port provided");
                        goto err;
                }
        }

        h = (hs != NULL) ? hs : host;
        p = (ps != NULL) ? ps : port;

        /*
         * First check if the host is specified as a numeric IP address,
         * either IPv4 or IPv6, before trying to resolve the host.
         * The AI_ADDRCONFIG resolver option will not return IPv4 or IPv6
         * records if it is not configured on an interface;  not considering
         * loopback addresses.  Checking the numeric addresses first makes
         * sure that connection attempts to numeric addresses and especially
         * 127.0.0.1 or ::1 loopback addresses are always possible.
         */
        memset(&hints, 0, sizeof(hints));
        hints.ai_socktype = SOCK_STREAM;

        /* try as an IPv4 literal */
        hints.ai_family = AF_INET;
        hints.ai_flags = AI_NUMERICHOST;
        if (getaddrinfo(h, p, &hints, &res0) != 0) {
                /* try again as an IPv6 literal */
                hints.ai_family = AF_INET6;
                if (getaddrinfo(h, p, &hints, &res0) != 0) {
                        /* last try, with name resolution and save the error */
                        hints.ai_family = AF_UNSPEC;
                        hints.ai_flags = AI_ADDRCONFIG;
                        if ((s = getaddrinfo(h, p, &hints, &res0)) != 0) {
                                tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                                    "%s", gai_strerror(s));
                                goto err;
                        }
                }
        }

        /* It was resolved somehow; now try connecting to what we got */
        s = -1;
        for (res = res0; res; res = res->ai_next) {
                s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
                if (s == -1) {
                        tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                            "socket");
                        continue;
                }
                if (connect(s, res->ai_addr, res->ai_addrlen) == -1) {
                        tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                            "connect");
                        close(s);
                        s = -1;
                        continue;
                }

                break;  /* Connected. */
        }
        freeaddrinfo(res0);

        if (s == -1)
                goto err;

        if (servername == NULL)
                servername = h;

        if (tls_connect_socket(ctx, s, servername) != 0) {
                close(s);
                goto err;
        }

        ctx->socket = s;

        rv = 0;

 err:
        free(hs);
        free(ps);

        return (rv);
}

static int
tls_client_read_session(struct tls *ctx)
{
        int sfd = ctx->config->session_fd;
        uint8_t *session = NULL;
        size_t session_len = 0;
        SSL_SESSION *ss = NULL;
        BIO *bio = NULL;
        struct stat sb;
        ssize_t n;
        int rv = -1;

        if (fstat(sfd, &sb) == -1) {
                tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                    "failed to stat session file");
                goto err;
        }
        if (sb.st_size < 0 || sb.st_size > INT_MAX) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "invalid session file size");
                goto err;
        }
        session_len = (size_t)sb.st_size;

        /* A zero size file means that we do not yet have a valid session. */
        if (session_len == 0)
                goto done;

        if ((session = malloc(session_len)) == NULL)
                goto err;

        n = pread(sfd, session, session_len, 0);
        if (n < 0 || (size_t)n != session_len) {
                tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                    "failed to read session file");
                goto err;
        }
        if ((bio = BIO_new_mem_buf(session, session_len)) == NULL)
                goto err;
        if ((ss = PEM_read_bio_SSL_SESSION(bio, NULL, tls_password_cb,
            NULL)) == NULL) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "failed to parse session");
                goto err;
        }

        if (SSL_set_session(ctx->ssl_conn, ss) != 1) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "failed to set session");
                goto err;
        }

 done:
        rv = 0;

 err:
        freezero(session, session_len);
        SSL_SESSION_free(ss);
        BIO_free(bio);

        return rv;
}

static int
tls_client_write_session(struct tls *ctx)
{
        int sfd = ctx->config->session_fd;
        SSL_SESSION *ss = NULL;
        BIO *bio = NULL;
        long data_len;
        char *data;
        off_t offset;
        size_t len;
        ssize_t n;
        int rv = -1;

        if ((ss = SSL_get1_session(ctx->ssl_conn)) == NULL) {
                if (ftruncate(sfd, 0) == -1) {
                        tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                            "failed to truncate session file");
                        goto err;
                }
                goto done;
        }

        if ((bio = BIO_new(BIO_s_mem())) == NULL)
                goto err;
        if (PEM_write_bio_SSL_SESSION(bio, ss) == 0)
                goto err;
        if ((data_len = BIO_get_mem_data(bio, &data)) <= 0)
                goto err;

        len = (size_t)data_len;
        offset = 0;

        if (ftruncate(sfd, len) == -1) {
                tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                    "failed to truncate session file");
                goto err;
        }
        while (len > 0) {
                if ((n = pwrite(sfd, data + offset, len, offset)) == -1) {
                        tls_set_error(ctx, TLS_ERROR_UNKNOWN,
                            "failed to write session file");
                        goto err;
                }
                offset += n;
                len -= n;
        }

 done:
        rv = 0;

 err:
        SSL_SESSION_free(ss);
        BIO_free_all(bio);

        return (rv);
}

static int
tls_connect_common(struct tls *ctx, const char *servername)
{
        union tls_addr addrbuf;
        size_t servername_len;
        int rv = -1;

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

        if (servername != NULL) {
                if ((ctx->servername = strdup(servername)) == NULL) {
                        tls_set_errorx(ctx, TLS_ERROR_OUT_OF_MEMORY,
                            "out of memory");
                        goto err;
                }

                /*
                 * If there's a trailing dot, remove it. While an FQDN includes
                 * the terminating dot representing the zero-length label of
                 * the root (RFC 8499, section 2), the SNI explicitly does not
                 * include it (RFC 6066, section 3).
                 */
                servername_len = strlen(ctx->servername);
                if (servername_len > 0 &&
                    ctx->servername[servername_len - 1] == '.')
                        ctx->servername[servername_len - 1] = '\0';
        }

        if ((ctx->ssl_ctx = SSL_CTX_new(SSLv23_client_method())) == NULL) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "ssl context failure");
                goto err;
        }

        if (tls_configure_ssl(ctx, ctx->ssl_ctx) != 0)
                goto err;

        if (tls_configure_ssl_keypair(ctx, ctx->ssl_ctx,
            ctx->config->keypair, 0) != 0)
                goto err;

        if (ctx->config->verify_name) {
                if (ctx->servername == NULL) {
                        tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                            "server name not specified");
                        goto err;
                }
        }

        if (tls_configure_ssl_verify(ctx, ctx->ssl_ctx, SSL_VERIFY_PEER) == -1)
                goto err;

        if (ctx->config->ecdhecurves != NULL) {
                if (SSL_CTX_set1_groups(ctx->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 (SSL_CTX_set_tlsext_status_cb(ctx->ssl_ctx, tls_ocsp_verify_cb) != 1) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "ssl OCSP verification setup failure");
                goto err;
        }

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

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

        if (ctx->config->session_fd != -1) {
                SSL_clear_options(ctx->ssl_conn, SSL_OP_NO_TICKET);
                if (tls_client_read_session(ctx) == -1)
                        goto err;
        }

        if (SSL_set_tlsext_status_type(ctx->ssl_conn, TLSEXT_STATUSTYPE_ocsp) != 1) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                    "ssl OCSP extension setup failure");
                goto err;
        }

        /*
         * RFC 6066 (SNI): Literal IPv4 and IPv6 addresses are not
         * permitted in "HostName".
         */
        if (ctx->servername != NULL &&
            inet_pton(AF_INET, ctx->servername, &addrbuf) != 1 &&
            inet_pton(AF_INET6, ctx->servername, &addrbuf) != 1) {
                if (SSL_set_tlsext_host_name(ctx->ssl_conn,
                    ctx->servername) == 0) {
                        tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                            "server name indication failure");
                        goto err;
                }
        }

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

 err:
        return (rv);
}

int
tls_connect_socket(struct tls *ctx, int s, const char *servername)
{
        return tls_connect_fds(ctx, s, s, servername);
}

int
tls_connect_fds(struct tls *ctx, int fd_read, int fd_write,
    const char *servername)
{
        int rv = -1;

        if (fd_read < 0 || fd_write < 0) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "invalid file descriptors");
                goto err;
        }

        if (tls_connect_common(ctx, servername) != 0)
                goto err;

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

        rv = 0;
 err:
        return (rv);
}

int
tls_connect_cbs(struct tls *ctx, tls_read_cb read_cb,
    tls_write_cb write_cb, void *cb_arg, const char *servername)
{
        int rv = -1;

        if (tls_connect_common(ctx, servername) != 0)
                goto err;

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

        rv = 0;

 err:
        return (rv);
}

int
tls_handshake_client(struct tls *ctx)
{
        X509 *cert = NULL;
        int match, ssl_ret;
        int rv = -1;

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

        if ((ctx->state & TLS_CONNECTED) == 0) {
                tls_set_errorx(ctx, TLS_ERROR_UNKNOWN, "context not connected");
                goto err;
        }

        ctx->state |= TLS_SSL_NEEDS_SHUTDOWN;

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

        if (ctx->config->verify_name) {
                cert = SSL_get_peer_certificate(ctx->ssl_conn);
                if (cert == NULL) {
                        tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                            "no server certificate");
                        goto err;
                }
                if (tls_check_name(ctx, cert, ctx->servername, &match) == -1)
                        goto err;
                if (!match) {
                        tls_set_errorx(ctx, TLS_ERROR_UNKNOWN,
                            "name `%s' not present in server certificate",
                            ctx->servername);
                        goto err;
                }
        }

        ctx->state |= TLS_HANDSHAKE_COMPLETE;

        if (ctx->config->session_fd != -1) {
                if (tls_client_write_session(ctx) == -1)
                        goto err;
        }

        rv = 0;

 err:
        X509_free(cert);

        return (rv);
}