tls.c

/*
 * Copyright (c) 2014, 2015, Nikos Mavrogiannopoulos.  All rights reserved.
 * Copyright (c) 2015, Red Hat, Inc. 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 <config.h>
#include <includes.h>
#include <radcli/radcli.h>
#include "util.h"
#include "tls.h"
 
#ifdef HAVE_GNUTLS
 
#include <gnutls/gnutls.h>
#include <gnutls/dtls.h>
#include <pthread.h>
#include <time.h>
 
#define DEFAULT_DTLS_SECRET "radius/dtls"
#define DEFAULT_TLS_SECRET "radsec"
 
typedef struct tls_int_st {
        char hostname[256];     /* server's hostname */
        unsigned port;          /* server's port */
        struct sockaddr_storage our_sockaddr;
        gnutls_session_t session;
        int sockfd;
        unsigned init;
        unsigned need_restart;
        unsigned skip_hostname_check; /* whether to verify hostname */
        pthread_mutex_t lock;
        time_t last_msg;
        time_t last_restart;
} tls_int_st;
 
typedef struct tls_st {
        gnutls_psk_client_credentials_t psk_cred;
        gnutls_certificate_credentials_t x509_cred;
        struct tls_int_st ctx;  /* one for ACCT and another for AUTH */
        unsigned flags; /* the flags set on init */
        rc_handle *rh; /* a pointer to our owner */
} tls_st;
 
static void restart_session(rc_handle *rh, tls_st *st);
 
static int tls_get_fd(void *ptr, struct sockaddr *our_sockaddr)
{
        tls_st *st = ptr;
        return st->ctx.sockfd;
}
 
static ssize_t tls_sendto(void *ptr, int sockfd,
                           const void *buf, size_t len,
                           int flags, const struct sockaddr *dest_addr,
                           socklen_t addrlen)
{
        tls_st *st = ptr;
        int ret;
 
        if (st->ctx.need_restart != 0) {
                restart_session(st->rh, st);
        }
 
        ret = gnutls_record_send(st->ctx.session, buf, len);
        if (ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED) {
                errno = EINTR;
                return -1;
        }
 
        if (ret < 0) {
                rc_log(LOG_ERR, "%s: error in sending: %s", __func__,
                       gnutls_strerror(ret));
                errno = EIO;
                st->ctx.need_restart = 1;
                return -1;
        }
 
        st->ctx.last_msg = time(0);
        return ret;
}
 
static int tls_lock(void *ptr)
{
        tls_st *st = ptr;
 
        return pthread_mutex_lock(&st->ctx.lock);
}
 
static int tls_unlock(void *ptr)
{
        tls_st *st = ptr;
 
        return pthread_mutex_unlock(&st->ctx.lock);
}
 
static ssize_t tls_recvfrom(void *ptr, int sockfd,
                             void *buf, size_t len,
                             int flags, struct sockaddr *src_addr,
                             socklen_t * addrlen)
{
        tls_st *st = ptr;
        int ret;
 
        ret = gnutls_record_recv(st->ctx.session, buf, len);
        if (ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED ||
            ret == GNUTLS_E_HEARTBEAT_PING_RECEIVED || ret == GNUTLS_E_HEARTBEAT_PONG_RECEIVED) {
                errno = EINTR;
                return -1;
        }
 
        if (ret == GNUTLS_E_WARNING_ALERT_RECEIVED) {
                rc_log(LOG_ERR, "%s: received alert: %s", __func__,
                       gnutls_alert_get_name(gnutls_alert_get(st->ctx.session)));
                errno = EINTR;
                return -1;
        }
 
        /* RFC6614 says: "After the TLS session is established, RADIUS packet payloads are
         * exchanged over the encrypted TLS tunnel.  In RADIUS/UDP, the
         * packet size can be determined by evaluating the size of the
         * datagram that arrived.  Due to the stream nature of TCP and TLS,
         * this does not hold true for RADIUS/TLS packet exchange.",
         *
         * That is correct in principle but it fails to associate the length with 
         * the TLS record boundaries. Here, when in TLS, we assume that a single TLS
         * record holds a single radius packet. It wouldn't make sense anyway to send
         * multiple TLS records for a single packet.
         */
 
        if (ret <= 0) {
                rc_log(LOG_ERR, "%s: error in receiving: %s", __func__,
                       gnutls_strerror(ret));
                errno = EIO;
                st->ctx.need_restart = 1;
                return -1;
        }
 
        st->ctx.last_msg = time(0);
        return ret;
}
 
/* This function will verify the peer's certificate, and check
 * if the hostname matches.
 */
static int cert_verify_callback(gnutls_session_t session)
{
        unsigned int status;
        int ret;
        struct tls_int_st *ctx;
        gnutls_datum_t out;
 
        /* read hostname */
        ctx = gnutls_session_get_ptr(session);
        if (ctx == NULL)
                return GNUTLS_E_CERTIFICATE_ERROR;
 
        if (ctx->skip_hostname_check)
                ret = gnutls_certificate_verify_peers2(session, &status);
        else
                ret = gnutls_certificate_verify_peers3(session, ctx->hostname, &status);
        if (ret < 0) {
                rc_log(LOG_ERR, "%s: error in certificate verification: %s",
                       __func__, gnutls_strerror(ret));
                return GNUTLS_E_CERTIFICATE_ERROR;
        }
 
        if (status != 0) {
                ret =
                    gnutls_certificate_verification_status_print(status,
                                                                 gnutls_certificate_type_get
                                                                 (session),
                                                                 &out, 0);
                if (ret < 0) {
                        return GNUTLS_E_CERTIFICATE_ERROR;
                }
                rc_log(LOG_INFO, "%s: certificate: %s", __func__, out.data);
                gnutls_free(out.data);
                return GNUTLS_E_CERTIFICATE_ERROR;
        }
 
        return 0;
}
 
static void deinit_session(tls_int_st *ses)
{
        if (ses->init != 0) {
                ses->init = 0;
                pthread_mutex_destroy(&ses->lock);
                if (ses->sockfd != -1)
                        close(ses->sockfd);
                if (ses->session)
                        gnutls_deinit(ses->session);
        }
}
 
static int init_session(rc_handle *rh, tls_int_st *ses,
                        const char *hostname, unsigned port,
                        struct sockaddr_storage *our_sockaddr,
                        int timeout,
                        unsigned secflags)
{
        int sockfd, ret, e;
        struct addrinfo *info;
        char *p;
        unsigned flags = 0;
        unsigned cred_set = 0;
        tls_st *st = rh->so.ptr;
 
        ses->sockfd = -1;
        ses->init = 1;
 
        pthread_mutex_init(&ses->lock, NULL);
        sockfd = socket(our_sockaddr->ss_family, (secflags&SEC_FLAG_DTLS)?SOCK_DGRAM:SOCK_STREAM, 0);
        if (sockfd < 0) {
                rc_log(LOG_ERR,
                       "%s: cannot open socket", __func__);
                ret = -1;
                goto cleanup;
        }
 
        if (our_sockaddr->ss_family == AF_INET)
                ((struct sockaddr_in *)our_sockaddr)->sin_port = 0;
        else
                ((struct sockaddr_in6 *)our_sockaddr)->sin6_port = 0;
 
        ses->sockfd = sockfd;
 
        /* Initialize DTLS */
 
        flags = GNUTLS_CLIENT;
        if (secflags&SEC_FLAG_DTLS)
                flags |= GNUTLS_DATAGRAM;
        ret = gnutls_init(&ses->session, flags);
        if (ret < 0) {
                rc_log(LOG_ERR,
                       "%s: error in gnutls_init(): %s", __func__, gnutls_strerror(ret));
                ret = -1;
                goto cleanup;
        }
 
        memcpy(&ses->our_sockaddr, our_sockaddr, sizeof(*our_sockaddr));
        if (!(secflags&SEC_FLAG_DTLS)) {
                if (timeout > 0) {
                        gnutls_handshake_set_timeout(ses->session, timeout*1000);
                } else {
                        gnutls_handshake_set_timeout(ses->session, GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
                }
        } else { /* DTLS */
                if (timeout > 0)
                        gnutls_dtls_set_timeouts(ses->session, 1000, timeout*1000);
        }
 
        gnutls_transport_set_int(ses->session, sockfd);
        gnutls_session_set_ptr(ses->session, ses);
        /* we only initiate heartbeat messages */
        gnutls_heartbeat_enable(ses->session, GNUTLS_HB_LOCAL_ALLOWED_TO_SEND);
 
        p = rc_conf_str(rh, "tls-verify-hostname");
        if (p && (strcasecmp(p, "false") == 0 || strcasecmp(p, "no"))) {
                ses->skip_hostname_check = 1;
        }
 
        if (st && st->psk_cred) {
                cred_set = 1;
                gnutls_credentials_set(ses->session,
                                       GNUTLS_CRD_PSK, st->psk_cred);
 
                ret = gnutls_priority_set_direct(ses->session, "NORMAL:-KX-ALL:+ECDHE-PSK:+DHE-PSK:+PSK:-VERS-TLS1.0", NULL);
                if (ret < 0) {
                        ret = -1;
                        rc_log(LOG_ERR,
                               "%s: error in setting PSK priorities: %s",
                               __func__, gnutls_strerror(ret));
                        goto cleanup;
                }
        } else if (st) {
                cred_set = 1;
                if (st->x509_cred) {
                        gnutls_credentials_set(ses->session,
                                               GNUTLS_CRD_CERTIFICATE,
                                               st->x509_cred);
                }
 
                gnutls_set_default_priority(ses->session);
        }
 
        gnutls_server_name_set(ses->session, GNUTLS_NAME_DNS,
                               hostname, strlen(hostname));
 
        info =
            rc_getaddrinfo(hostname, PW_AI_AUTH);
        if (info == NULL) {
                ret = -1;
                rc_log(LOG_ERR, "%s: cannot resolve %s", __func__,
                       hostname);
                goto cleanup;
        }
 
        if (port != 0) {
                if (info->ai_addr->sa_family == AF_INET)
                        ((struct sockaddr_in *)info->ai_addr)->sin_port =
                            htons(port);
                else
                        ((struct sockaddr_in6 *)info->ai_addr)->sin6_port =
                            htons(port);
        } else {
                rc_log(LOG_ERR, "%s: no port specified for server %s",
                       __func__, hostname);
                ret = -1;
                goto cleanup;
        }
 
        strlcpy(ses->hostname, hostname, sizeof(ses->hostname));
        ses->port = port;
 
        if (cred_set == 0) {
                rc_log(LOG_CRIT,
                       "%s: neither tls-ca-file or a PSK key are configured",
                       __func__);
                ret = -1;
                goto cleanup;
        }
 
        /* we connect since we are talking to a single server */
        ret = connect(sockfd, info->ai_addr, info->ai_addrlen);
        freeaddrinfo(info);
        if (ret == -1) {
                e = errno;
                ret = -1;
                rc_log(LOG_CRIT, "%s: cannot connect to %s: %s",
                       __func__, hostname, strerror(e));
                goto cleanup;
        }
 
        rc_log(LOG_DEBUG,
               "%s: performing TLS/DTLS handshake with [%s]:%d",
               __func__, hostname, port);
        do {
                ret = gnutls_handshake(ses->session);
                if (ret == GNUTLS_E_LARGE_PACKET)
                        break;
        } while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
 
        if (ret < 0) {
                rc_log(LOG_ERR, "%s: error in handshake: %s",
                       __func__, gnutls_strerror(ret));
                ret = -1;
                goto cleanup;
        }
 
        return 0;
 cleanup:
        deinit_session(ses);
        return ret;
 
}
 
/* The time after the last message was received, that
 * we will try heartbeats */
#define TIME_ALIVE 120
 
static void restart_session(rc_handle *rh, tls_st *st)
{
        struct tls_int_st tmps;
        time_t now = time(0);
        int ret;
        int timeout;
 
        if (now - st->ctx.last_restart < TIME_ALIVE)
                return;
 
        st->ctx.last_restart = now;
 
        timeout = rc_conf_int(rh, "radius_timeout");
 
        /* reinitialize this session */
        ret = init_session(rh, &tmps, st->ctx.hostname, st->ctx.port, &st->ctx.our_sockaddr, timeout, st->flags);
        if (ret < 0) {
                rc_log(LOG_ERR, "%s: error in re-initializing DTLS", __func__);
                return;
        }
 
        if (tmps.sockfd == st->ctx.sockfd)
                st->ctx.sockfd = -1;
        deinit_session(&st->ctx);
        memcpy(&st->ctx, &tmps, sizeof(tmps));
        st->ctx.need_restart = 0;
 
        return;
}
 
int rc_tls_fd(rc_handle * rh)
{
        tls_st *st;
 
        if (rh->so_type != RC_SOCKET_TLS && rh->so_type != RC_SOCKET_DTLS)
                return -1;
 
        st = rh->so.ptr;
 
        if (st->ctx.init != 0) {
                return st->ctx.sockfd;
        }
        return -1;
}
 
int rc_check_tls(rc_handle * rh)
{
        tls_st *st;
        time_t now = time(0);
        int ret;
 
        if (rh->so_type != RC_SOCKET_TLS && rh->so_type != RC_SOCKET_DTLS)
                return 0;
 
        st = rh->so.ptr;
 
        if (st->ctx.init != 0) {
                if (st->ctx.need_restart != 0) {
                        restart_session(rh, st);
                } else if (now - st->ctx.last_msg > TIME_ALIVE) {
                        ret = gnutls_heartbeat_ping(st->ctx.session, 64, 4, GNUTLS_HEARTBEAT_WAIT);
                        if (ret < 0) {
                                restart_session(rh, st);
                        }
                        st->ctx.last_msg = now;
                }
        }
        return 0;
}
 
/*- This function will deinitialize a previously initialed DTLS or TLS session.
 *
 * @param rh the configuration handle.
 -*/
void rc_deinit_tls(rc_handle * rh)
{
        tls_st *st = rh->so.ptr;
        char *ns = NULL;
        int ns_def_hdl = 0;
 
        if (st) {
                ns = rc_conf_str(rh, "namespace"); /* Check for namespace config */
                if (ns != NULL) {
                        if(-1 == rc_set_netns(ns, &ns_def_hdl)) {
                                rc_log(LOG_ERR, "rc_send_server: namespace %s set failed", ns);
                                return;
                        }
                }
                if (st->ctx.init != 0)
                        deinit_session(&st->ctx);
                if (st->x509_cred)
                        gnutls_certificate_free_credentials(st->x509_cred);
                if (st->psk_cred)
                        gnutls_psk_free_client_credentials(st->psk_cred);
                if (ns != NULL) {
                        if(-1 == rc_reset_netns(&ns_def_hdl))
                        rc_log(LOG_ERR, "rc_send_server: namespace %s reset failed", ns);
                }
        }
        free(st);
}
 
/*- Initialize a configuration for TLS or DTLS
 *
 * This function will initialize the handle for TLS or DTLS.
 *
 * @param rh a handle to parsed configuration
 * @param flags must be zero or SEC_FLAG_DTLS
 * @return 0 on success, -1 on failure.
 -*/
int rc_init_tls(rc_handle * rh, unsigned flags)
{
        int ret;
        tls_st *st = NULL;
        struct sockaddr_storage our_sockaddr;
        const char *ca_file = rc_conf_str(rh, "tls-ca-file");
        const char *cert_file = rc_conf_str(rh, "tls-cert-file");
        const char *key_file = rc_conf_str(rh, "tls-key-file");
        const char *pskkey = NULL;
        SERVER *authservers;
        char hostname[256];     /* server's hostname */
        unsigned port;          /* server's port */
        char *ns = NULL;
        int ns_def_hdl = 0;
 
        memset(&rh->so, 0, sizeof(rh->so));
 
        ns = rc_conf_str(rh, "namespace"); /* Check for namespace config */
        if (ns != NULL) {
                if(-1 == rc_set_netns(ns, &ns_def_hdl)) {
                        rc_log(LOG_ERR, "rc_send_server: namespace %s set failed", ns);
                        return -1;
                }
        }
 
        if (flags & SEC_FLAG_DTLS) {
                rh->so_type = RC_SOCKET_DTLS;
                rh->so.static_secret = DEFAULT_DTLS_SECRET;
        } else {
                rh->so_type = RC_SOCKET_TLS;
                rh->so.static_secret = DEFAULT_TLS_SECRET;
        }
 
        rc_own_bind_addr(rh, &our_sockaddr);
 
        st = calloc(1, sizeof(tls_st));
        if (st == NULL) {
                ret = -1;
                goto cleanup;
        }
 
        st->rh = rh;
        st->flags = flags;
 
        rh->so.ptr = st;
 
        if (ca_file || (key_file && cert_file)) {
                ret = gnutls_certificate_allocate_credentials(&st->x509_cred);
                if (ret < 0) {
                        ret = -1;
                        rc_log(LOG_ERR,
                               "%s: error in setting X.509 credentials: %s",
                               __func__, gnutls_strerror(ret));
                        goto cleanup;
                }
 
                if (ca_file) {
                        ret =
                            gnutls_certificate_set_x509_trust_file(st->x509_cred,
                                                           ca_file,
                                                           GNUTLS_X509_FMT_PEM);
                        if (ret < 0) {
                                ret = -1;
                                rc_log(LOG_ERR,
                                       "%s: error in setting X.509 trust file: %s: %s",
                                       __func__, gnutls_strerror(ret), ca_file);
                                goto cleanup;
                        }
                }
 
                if (cert_file && key_file) {
                        ret =
                            gnutls_certificate_set_x509_key_file(st->x509_cred,
                                                                 cert_file,
                                                                 key_file,
                                                                 GNUTLS_X509_FMT_PEM);
                        if (ret < 0) {
                                ret = -1;
                                rc_log(LOG_ERR,
                                       "%s: error in setting X.509 cert and key files: %s: %s - %s",
                                       __func__, gnutls_strerror(ret), cert_file, key_file);
                                goto cleanup;
                        }
                }
 
                gnutls_certificate_set_verify_function(st->x509_cred,
                                                       cert_verify_callback);
        }
 
        /* Read the PSK key if any */
        authservers = rc_conf_srv(rh, "authserver");
        if (authservers == NULL) {
                rc_log(LOG_ERR,
                       "%s: cannot find authserver", __func__);
                ret = -1;
                goto cleanup;
        }
        if (authservers->max > 1) {
                ret = -1;
                rc_log(LOG_ERR,
                       "%s: too many auth servers for TLS/DTLS; only one is allowed",
                       __func__);
                goto cleanup;
        }
        strlcpy(hostname, authservers->name[0], sizeof(hostname));
        port = authservers->port[0];
        if (authservers->secret)
                pskkey = authservers->secret[0];
 
        if (pskkey && pskkey[0] != 0) {
                char *p;
                char username[64];
                gnutls_datum_t hexkey;
                int username_len;
 
                if (strncmp(pskkey, "psk@", 4) != 0) {
                        ret = -1;
                        rc_log(LOG_ERR,
                               "%s: server secret is set but does not start with 'psk@'",
                               __func__);
                        goto cleanup;
                }
                pskkey+=4;
 
                if ((p = strchr(pskkey, '@')) == NULL) {
                        ret = -1;
                        rc_log(LOG_ERR,
                               "%s: PSK key is not in 'username@hexkey' format",
                               __func__);
                        goto cleanup;
                }
 
                username_len = p - pskkey;
                if (username_len + 1 > sizeof(username)) {
                        rc_log(LOG_ERR,
                               "%s: PSK username too big", __func__);
                        ret = -1;
                        goto cleanup;
                }
 
                strlcpy(username, pskkey, username_len + 1);
 
                p++;
                hexkey.data = (uint8_t*)p;
                hexkey.size = strlen(p);
 
                ret = gnutls_psk_allocate_client_credentials(&st->psk_cred);
                if (ret < 0) {
                        ret = -1;
                        rc_log(LOG_ERR,
                               "%s: error in setting PSK credentials: %s",
                               __func__, gnutls_strerror(ret));
                        goto cleanup;
                }
 
                ret =
                    gnutls_psk_set_client_credentials(st->psk_cred,
                                                      username, &hexkey,
                                                      GNUTLS_PSK_KEY_HEX);
                if (ret < 0) {
                        ret = -1;
                        rc_log(LOG_ERR,
                               "%s: error in setting PSK key: %s",
                               __func__, gnutls_strerror(ret));
                        goto cleanup;
                }
        }
 
        ret = init_session(rh, &st->ctx, hostname, port, &our_sockaddr, 0, flags);
        if (ret < 0) {
                ret = -1;
                goto cleanup;
        }
 
        rh->so.get_fd = tls_get_fd;
        rh->so.sendto = tls_sendto;
        rh->so.recvfrom = tls_recvfrom;
        rh->so.lock = tls_lock;
        rh->so.unlock = tls_unlock;
        if (ns != NULL) {
                if(-1 == rc_reset_netns(&ns_def_hdl)) {
                        rc_log(LOG_ERR, "rc_send_server: namespace %s reset failed", ns);
                        goto cleanup;
                }
        }
        return 0;
 cleanup:
        if (st) {
                if (st->ctx.init != 0)
                        deinit_session(&st->ctx);
                if (st->x509_cred)
                        gnutls_certificate_free_credentials(st->x509_cred);
                if (st->psk_cred)
                        gnutls_psk_free_client_credentials(st->psk_cred);
        }
        free(st);
        if (ns != NULL) {
                if(-1 == rc_reset_netns(&ns_def_hdl))
                rc_log(LOG_ERR, "rc_send_server: namespace %s reset failed", ns);
        }
        return ret;
}
 
#endif