/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2008 Isilon Inc http://www.isilon.com/
 * Authors: Doug Rabson <dfr@rabson.org>
 * Developed with Red Inc: Alfred Perlstein <alfred@freebsd.org>
 *
 * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
 */

/*
 * Extensively modified from /usr/src/usr.sbin/gssd.c r344402 for
 * the client side of kernel RPC-over-TLS by Rick Macklem.
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/queue.h>
#include <sys/linker.h>
#include <sys/module.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/time.h>
#include <err.h>
#include <getopt.h>
#include <libutil.h>
#include <netdb.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <rpc/rpc.h>
#include <rpc/rpc_com.h>
#include <rpc/rpcsec_tls.h>

#include <openssl/opensslconf.h>
#include <openssl/bio.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/x509v3.h>

#include "rpctlscd.h"
#include "rpc.tlscommon.h"

#ifndef _PATH_CERTANDKEY
#define _PATH_CERTANDKEY        "/etc/rpc.tlsclntd/"
#endif
#ifndef _PATH_RPCTLSCDPID
#define _PATH_RPCTLSCDPID       "/var/run/rpc.tlsclntd.pid"
#endif

/* Global variables also used by rpc.tlscommon.c. */
int                     rpctls_debug_level;
bool                    rpctls_verbose;
SSL_CTX                 *rpctls_ctx = NULL;
const char              *rpctls_verify_cafile = NULL;
const char              *rpctls_verify_capath = NULL;
char                    *rpctls_crlfile = NULL;
bool                    rpctls_cert = false;
bool                    rpctls_gothup = false;
struct ssl_list         rpctls_ssllist;

static struct pidfh     *rpctls_pfh = NULL;
static const char       *rpctls_certdir = _PATH_CERTANDKEY;
static const char       *rpctls_ciphers = NULL;
static int              rpctls_tlsvers = TLS1_3_VERSION;

static void             rpctlscd_terminate(int);
static SSL_CTX          *rpctls_setupcl_ssl(void);
static SSL              *rpctls_connect(SSL_CTX *ctx, int s, char *certname,
                            u_int certlen, X509 **certp);
static void             rpctls_huphandler(int sig __unused);

extern void rpctlscd_2(struct svc_req *rqstp, SVCXPRT *transp);

static struct option longopts[] = {
        { "usetls1_2",          no_argument,            NULL,   '2' },
        { "certdir",            required_argument,      NULL,   'D' },
        { "ciphers",            required_argument,      NULL,   'C' },
        { "debuglevel",         no_argument,            NULL,   'd' },
        { "verifylocs",         required_argument,      NULL,   'l' },
        { "mutualverf",         no_argument,            NULL,   'm' },
        { "verifydir",          required_argument,      NULL,   'p' },
        { "crl",                required_argument,      NULL,   'r' },
        { "verbose",            no_argument,            NULL,   'v' },
        { NULL,                 0,                      NULL,   0  }
};

int
main(int argc, char **argv)
{
        int ch;
        SVCXPRT *xprt;
        bool tls_enable;
        pid_t otherpid;
        size_t tls_enable_len;

        /* Check that another rpctlscd isn't already running. */
        rpctls_pfh = pidfile_open(_PATH_RPCTLSCDPID, 0600, &otherpid);
        if (rpctls_pfh == NULL) {
                if (errno == EEXIST)
                        errx(1, "rpctlscd already running, pid: %d.", otherpid);
                warn("cannot open or create pidfile");
        }

        /* Check to see that the ktls is enabled. */
        tls_enable_len = sizeof(tls_enable);
        if (sysctlbyname("kern.ipc.tls.enable", &tls_enable, &tls_enable_len,
            NULL, 0) != 0 || !tls_enable)
                errx(1, "Kernel TLS not enabled");

        rpctls_verbose = false;
        while ((ch = getopt_long(argc, argv, "2C:D:dl:mp:r:v", longopts,
            NULL)) != -1) {
                switch (ch) {
                case '2':
                        rpctls_tlsvers = TLS1_2_VERSION;
                        break;
                case 'C':
                        rpctls_ciphers = optarg;
                        break;
                case 'D':
                        rpctls_certdir = optarg;
                        break;
                case 'd':
                        rpctls_debug_level++;
                        break;
                case 'l':
                        rpctls_verify_cafile = optarg;
                        break;
                case 'm':
                        rpctls_cert = true;
                        break;
                case 'p':
                        rpctls_verify_capath = optarg;
                        break;
                case 'r':
                        rpctls_crlfile = optarg;
                        break;
                case 'v':
                        rpctls_verbose = true;
                        break;
                default:
                        fprintf(stderr, "usage: %s "
                            "[-2/--usetls1_2] "
                            "[-C/--ciphers available_ciphers] "
                            "[-D/--certdir certdir] [-d/--debuglevel] "
                            "[-l/--verifylocs CAfile] [-m/--mutualverf] "
                            "[-p/--verifydir CApath] [-r/--crl CRLfile] "
                            "[-v/--verbose]\n", argv[0]);
                        exit(1);
                        break;
                }
        }
        if (rpctls_crlfile != NULL && rpctls_verify_cafile == NULL &&
            rpctls_verify_capath == NULL)
                errx(1, "-r requires the -l <CAfile> and/or "
                    "-p <CApath> options");

        if (modfind("krpc") < 0) {
                /* Not present in kernel, try loading it */
                if (kldload("krpc") < 0 || modfind("krpc") < 0)
                        errx(1, "Kernel RPC is not available");
        }

        /*
         * Set up the SSL_CTX *.
         * Do it now, before daemonizing, in case the private key
         * is encrypted and requires a passphrase to be entered.
         */
        rpctls_ctx = rpctls_setupcl_ssl();
        if (rpctls_ctx == NULL) {
                if (rpctls_debug_level == 0) {
                        syslog(LOG_ERR, "Can't set up TLS context");
                        exit(1);
                }
                err(1, "Can't set up TLS context");
        }
        LIST_INIT(&rpctls_ssllist);

        if (!rpctls_debug_level) {
                if (daemon(0, 0) != 0)
                        err(1, "Can't daemonize");
                signal(SIGINT, SIG_IGN);
                signal(SIGQUIT, SIG_IGN);
                signal(SIGHUP, SIG_IGN);
        }
        signal(SIGTERM, rpctlscd_terminate);
        signal(SIGPIPE, SIG_IGN);
        signal(SIGHUP, rpctls_huphandler);

        pidfile_write(rpctls_pfh);

        if ((xprt = svc_nl_create("tlsclnt")) == NULL) {
                if (rpctls_debug_level == 0) {
                        syslog(LOG_ERR,
                            "Can't create transport for local rpctlscd socket");
                        exit(1);
                }
                err(1, "Can't create transport for local rpctlscd socket");
        }
        if (!svc_reg(xprt, RPCTLSCD, RPCTLSCDVERS, rpctlscd_2, NULL)) {
                if (rpctls_debug_level == 0) {
                        syslog(LOG_ERR,
                            "Can't register service for local rpctlscd socket");
                        exit(1);
                }
                err(1, "Can't register service for local rpctlscd socket");
        }

        rpctls_svc_run();

        SSL_CTX_free(rpctls_ctx);
        return (0);
}

bool_t
rpctlscd_null_2_svc(__unused void *argp, __unused void *result,
    __unused struct svc_req *rqstp)
{

        rpctls_verbose_out("rpctlscd_null: done\n");
        return (TRUE);
}

bool_t
rpctlscd_connect_2_svc(struct rpctlscd_connect_arg *argp,
    struct rpctlscd_connect_res *result, __unused struct svc_req *rqstp)
{
        int s;
        SSL *ssl;
        struct ssl_entry *newslp;
        X509 *cert;

        rpctls_verbose_out("rpctlsd_connect: started\n");
        /* Get the socket fd from the kernel. */
        s = rpctls_syscall(argp->socookie);
        if (s < 0) {
                result->reterr = RPCTLSERR_NOSOCKET;
                return (TRUE);
        }

        /* Do a TLS connect handshake. */
        ssl = rpctls_connect(rpctls_ctx, s, argp->certname.certname_val,
            argp->certname.certname_len, &cert);
        if (ssl == NULL) {
                rpctls_verbose_out("rpctlsd_connect: can't do TLS "
                    "handshake\n");
                result->reterr = RPCTLSERR_NOSSL;
                /*
                 * For RPC-over-TLS, this upcall is expected
                 * to close off the socket.
                 */
                close(s);
                return (TRUE);
        } else
                result->reterr = RPCTLSERR_OK;

        /* Maintain list of all current SSL *'s */
        newslp = malloc(sizeof(*newslp));
        newslp->cookie = argp->socookie;
        newslp->s = s;
        newslp->shutoff = false;
        newslp->ssl = ssl;
        newslp->cert = cert;
        LIST_INSERT_HEAD(&rpctls_ssllist, newslp, next);
        return (TRUE);
}

bool_t
rpctlscd_handlerecord_2_svc(struct rpctlscd_handlerecord_arg *argp,
    struct rpctlscd_handlerecord_res *result, __unused struct svc_req *rqstp)
{
        struct ssl_entry *slp;
        int ret;
        char junk;

        LIST_FOREACH(slp, &rpctls_ssllist, next)
                if (slp->cookie == argp->socookie)
                        break;

        if (slp != NULL) {
                rpctls_verbose_out("rpctlscd_handlerecord fd=%d\n",
                    slp->s);
                /*
                 * An SSL_read() of 0 bytes should fail, but it should
                 * handle the non-application data record before doing so.
                 */
                ret = SSL_read(slp->ssl, &junk, 0);
                if (ret <= 0) {
                        /* Check to see if this was a close alert. */
                        ret = SSL_get_shutdown(slp->ssl);
                        if ((ret & (SSL_SENT_SHUTDOWN |
                            SSL_RECEIVED_SHUTDOWN)) == SSL_RECEIVED_SHUTDOWN)
                                SSL_shutdown(slp->ssl);
                } else {
                        if (rpctls_debug_level == 0)
                                syslog(LOG_ERR, "SSL_read returned %d", ret);
                        else
                                fprintf(stderr, "SSL_read returned %d\n", ret);
                }
                result->reterr = RPCTLSERR_OK;
        } else
                result->reterr = RPCTLSERR_NOSSL;
        return (TRUE);
}

bool_t
rpctlscd_disconnect_2_svc(struct rpctlscd_disconnect_arg *argp,
    struct rpctlscd_disconnect_res *result, __unused struct svc_req *rqstp)
{
        struct ssl_entry *slp;
        int ret;

        LIST_FOREACH(slp, &rpctls_ssllist, next)
                if (slp->cookie == argp->socookie)
                        break;

        if (slp != NULL) {
                rpctls_verbose_out("rpctlscd_disconnect: fd=%d closed\n",
                    slp->s);
                LIST_REMOVE(slp, next);
                if (!slp->shutoff) {
                        ret = SSL_get_shutdown(slp->ssl);
                        /*
                         * Do an SSL_shutdown() unless a close alert has
                         * already been sent.
                         */
                        if ((ret & SSL_SENT_SHUTDOWN) == 0)
                                SSL_shutdown(slp->ssl);
                }
                SSL_free(slp->ssl);
                if (slp->cert != NULL)
                        X509_free(slp->cert);
                /*
                 * For RPC-over-TLS, this upcall is expected
                 * to close off the socket.
                 */
                if (!slp->shutoff)
                        shutdown(slp->s, SHUT_WR);
                close(slp->s);
                free(slp);
                result->reterr = RPCTLSERR_OK;
        } else
                result->reterr = RPCTLSERR_NOCLOSE;
        return (TRUE);
}

int
rpctlscd_2_freeresult(__unused SVCXPRT *transp, __unused xdrproc_t xdr_result,
    __unused caddr_t result)
{

        return (TRUE);
}

static void
rpctlscd_terminate(int sig __unused)
{

        pidfile_remove(rpctls_pfh);
        exit(0);
}

static SSL_CTX *
rpctls_setupcl_ssl(void)
{
        SSL_CTX *ctx;
        char path[PATH_MAX];
        size_t len, rlen;
        int ret;

        ctx = SSL_CTX_new(TLS_client_method());
        if (ctx == NULL) {
                rpctls_verbose_out("rpctls_setupcl_ssl: SSL_CTX_new "
                    "failed\n");
                return (NULL);
        }

        if (rpctls_ciphers != NULL) {
                /*
                 * Set available ciphers, since KERN_TLS only supports a
                 * few of them.
                 */
                ret = SSL_CTX_set_ciphersuites(ctx, rpctls_ciphers);
                if (ret == 0) {
                        rpctls_verbose_out("rpctls_setupcl_ssl: "
                            "SSL_CTX_set_ciphersuites failed: %s\n",
                            rpctls_ciphers);
                        SSL_CTX_free(ctx);
                        return (NULL);
                }
        }

        /*
         * If rpctls_cert is true, a certificate and key exists in
         * rpctls_certdir, so that it can do mutual authentication.
         */
        if (rpctls_cert) {
                /* Get the cert.pem and certkey.pem files. */
                len = strlcpy(path, rpctls_certdir, sizeof(path));
                rlen = sizeof(path) - len;
                if (strlcpy(&path[len], "cert.pem", rlen) != 8) {
                        SSL_CTX_free(ctx);
                        return (NULL);
                }
                ret = SSL_CTX_use_certificate_file(ctx, path,
                    SSL_FILETYPE_PEM);
                if (ret != 1) {
                        rpctls_verbose_out("rpctls_setupcl_ssl: can't use "
                            "certificate file path=%s ret=%d\n", path, ret);
                        SSL_CTX_free(ctx);
                        return (NULL);
                }
                if (strlcpy(&path[len], "certkey.pem", rlen) != 11) {
                        SSL_CTX_free(ctx);
                        return (NULL);
                }
                ret = SSL_CTX_use_PrivateKey_file(ctx, path,
                    SSL_FILETYPE_PEM);
                if (ret != 1) {
                        rpctls_verbose_out("rpctls_setupcl_ssl: Can't use "
                            "private key path=%s ret=%d\n", path, ret);
                        SSL_CTX_free(ctx);
                        return (NULL);
                }
        }

        if (rpctls_verify_cafile != NULL || rpctls_verify_capath != NULL) {
                if (rpctls_crlfile != NULL) {
                        ret = rpctls_loadcrlfile(ctx);
                        if (ret == 0) {
                                rpctls_verbose_out("rpctls_setupcl_ssl: "
                                    "Load CRLfile failed\n");
                                SSL_CTX_free(ctx);
                                return (NULL);
                        }
                }
#if OPENSSL_VERSION_NUMBER >= 0x30000000
                ret = 1;
                if (rpctls_verify_cafile != NULL)
                        ret = SSL_CTX_load_verify_file(ctx,
                            rpctls_verify_cafile);
                if (ret != 0 && rpctls_verify_capath != NULL)
                        ret = SSL_CTX_load_verify_dir(ctx,
                            rpctls_verify_capath);
#else
                ret = SSL_CTX_load_verify_locations(ctx,
                    rpctls_verify_cafile, rpctls_verify_capath);
#endif
                if (ret == 0) {
                        rpctls_verbose_out("rpctls_setupcl_ssl: "
                            "Can't load verify locations\n");
                        SSL_CTX_free(ctx);
                        return (NULL);
                }
                /*
                 * The man page says that the
                 * SSL_CTX_set0_CA_list() call is not normally
                 * needed, but I believe it is harmless.
                 */
                if (rpctls_verify_cafile != NULL)
                        SSL_CTX_set0_CA_list(ctx,
                            SSL_load_client_CA_file(rpctls_verify_cafile));
        }

        /*
         * The RFC specifies that RPC-over-TLS must use TLS1.3.
         * However, early FreeBSD versions (13.0, 13.1) did not
         * support RX for KTLS1.3, so TLS1.2 needs to be used for
         * these servers.
         */
        ret = SSL_CTX_set_min_proto_version(ctx, rpctls_tlsvers);
        if (ret == 0) {
                rpctls_verbose_out("rpctls_setupcl_ssl: "
                    "SSL_CTX_set_min_proto_version failed\n");
                SSL_CTX_free(ctx);
                return (NULL);
        }
        ret = SSL_CTX_set_max_proto_version(ctx, rpctls_tlsvers);
        if (ret == 0) {
                rpctls_verbose_out("rpctls_setupcl_ssl: "
                    "SSL_CTX_set_max_proto_version failed\n");
                SSL_CTX_free(ctx);
                return (NULL);
        }

#ifdef SSL_OP_ENABLE_KTLS
        SSL_CTX_set_options(ctx, SSL_OP_ENABLE_KTLS);
#endif
#ifdef SSL_MODE_NO_KTLS_TX
        SSL_CTX_clear_mode(ctx, SSL_MODE_NO_KTLS_TX | SSL_MODE_NO_KTLS_RX);
#endif
        return (ctx);
}

static SSL *
rpctls_connect(SSL_CTX *ctx, int s, char *certname, u_int certlen, X509 **certp)
{
        SSL *ssl;
        X509 *cert;
        struct sockaddr_storage ad;
        struct sockaddr *sad;
        char hostnam[NI_MAXHOST], path[PATH_MAX];
        int gethostret, ret;
        char *cp, *cp2;
        size_t len, rlen;
        long verfret;

        *certp = NULL;
        sad = (struct sockaddr *)&ad;
        ssl = SSL_new(ctx);
        if (ssl == NULL) {
                rpctls_verbose_out("rpctls_connect: "
                    "SSL_new failed\n");
                return (NULL);
        }
        if (SSL_set_fd(ssl, s) != 1) {
                rpctls_verbose_out("rpctls_connect: "
                    "SSL_set_fd failed\n");
                SSL_free(ssl);
                return (NULL);
        }

        /*
         * If rpctls_cert is true and certname is set, a alternate certificate
         * and key exists in files named <certname>.pem and <certname>key.pem
         * in rpctls_certdir that is to be used for mutual authentication.
         */
        if (rpctls_cert && certlen > 0) {
                len = strlcpy(path, rpctls_certdir, sizeof(path));
                rlen = sizeof(path) - len;
                if (rlen <= certlen) {
                        SSL_free(ssl);
                        return (NULL);
                }
                memcpy(&path[len], certname, certlen);
                rlen -= certlen;
                len += certlen;
                path[len] = '\0';
                if (strlcpy(&path[len], ".pem", rlen) != 4) {
                        SSL_free(ssl);
                        return (NULL);
                }
                ret = SSL_use_certificate_file(ssl, path, SSL_FILETYPE_PEM);
                if (ret != 1) {
                        rpctls_verbose_out("rpctls_connect: can't use "
                            "certificate file path=%s ret=%d\n", path, ret);
                        SSL_free(ssl);
                        return (NULL);
                }
                if (strlcpy(&path[len], "key.pem", rlen) != 7) {
                        SSL_free(ssl);
                        return (NULL);
                }
                ret = SSL_use_PrivateKey_file(ssl, path, SSL_FILETYPE_PEM);
                if (ret != 1) {
                        rpctls_verbose_out("rpctls_connect: Can't use "
                            "private key path=%s ret=%d\n", path, ret);
                        SSL_free(ssl);
                        return (NULL);
                }
        }

        ret = SSL_connect(ssl);
        if (ret != 1) {
                rpctls_verbose_out("rpctls_connect: "
                    "SSL_connect failed %d: %s\n",
                    ret, ERR_error_string(ERR_get_error(), NULL));
                SSL_free(ssl);
                return (NULL);
        }

#if OPENSSL_VERSION_NUMBER >= 0x30000000
        cert = SSL_get1_peer_certificate(ssl);
#else
        cert = SSL_get_peer_certificate(ssl);
#endif
        if (cert == NULL) {
                rpctls_verbose_out("rpctls_connect: get peer"
                    " certificate failed\n");
                SSL_free(ssl);
                return (NULL);
        }
        gethostret = rpctls_gethost(s, sad, hostnam, sizeof(hostnam));
        if (gethostret == 0)
                hostnam[0] = '\0';
        verfret = SSL_get_verify_result(ssl);
        if (verfret == X509_V_OK && (rpctls_verify_cafile != NULL ||
            rpctls_verify_capath != NULL) && (gethostret == 0 ||
            rpctls_checkhost(sad, cert, X509_CHECK_FLAG_NO_WILDCARDS) != 1))
                verfret = X509_V_ERR_HOSTNAME_MISMATCH;
        if (verfret != X509_V_OK && (rpctls_verify_cafile != NULL ||
            rpctls_verify_capath != NULL)) {
                if (verfret != X509_V_OK) {
                        cp = X509_NAME_oneline(X509_get_issuer_name(cert),
                            NULL, 0);
                        cp2 = X509_NAME_oneline(X509_get_subject_name(cert),
                            NULL, 0);
                        if (rpctls_debug_level == 0)
                                syslog(LOG_INFO | LOG_DAEMON,
                                    "rpctls_connect: client IP %s "
                                    "issuerName=%s subjectName=%s verify "
                                    "failed %s\n", hostnam, cp, cp2,
                                    X509_verify_cert_error_string(verfret));
                        else
                                fprintf(stderr,
                                    "rpctls_connect: client IP %s "
                                    "issuerName=%s subjectName=%s verify "
                                    "failed %s\n", hostnam, cp, cp2,
                                    X509_verify_cert_error_string(verfret));
                }
                X509_free(cert);
                SSL_free(ssl);
                return (NULL);
        }

        /* Check to see if ktls is enabled on the connection. */
        ret = BIO_get_ktls_send(SSL_get_wbio(ssl));
        rpctls_verbose_out("rpctls_connect: BIO_get_ktls_send=%d\n", ret);
        if (ret != 0) {
                ret = BIO_get_ktls_recv(SSL_get_rbio(ssl));
                rpctls_verbose_out("rpctls_connect: BIO_get_ktls_recv=%d\n",
                    ret);
        }
        if (ret == 0) {
                if (rpctls_debug_level == 0)
                        syslog(LOG_ERR, "ktls not working\n");
                else
                        fprintf(stderr, "ktls not working\n");
                X509_free(cert);
                SSL_free(ssl);
                return (NULL);
        }
        if (ret == X509_V_OK && (rpctls_verify_cafile != NULL ||
            rpctls_verify_capath != NULL) && rpctls_crlfile != NULL)
                *certp = cert;
        else
                X509_free(cert);

        return (ssl);
}

static void
rpctls_huphandler(int sig __unused)
{

        rpctls_gothup = true;
}