ocserv/src/tlslib.c

/*
 * Copyright (C) 2013 Nikos Mavrogiannopoulos
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <config.h>

#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>
#include <gnutls/pkcs11.h>
#include <errno.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <limits.h>
#include <tlslib.h>
#include <ccan/hash/hash.h>
#include <vpn.h>
#include <main.h>
#include <worker.h>


ssize_t tls_send(gnutls_session_t session, const void *data,
			size_t data_size)
{
	int ret;
	int left = data_size;
	const uint8_t* p = data;

	while(left > 0) {
		ret = gnutls_record_send(session, p, data_size);
		if (ret < 0 && (ret != GNUTLS_E_AGAIN && ret != GNUTLS_E_INTERRUPTED)) {
			return ret;
		}
	
		if (ret > 0) {
			left -= ret;
			p += ret;
		}
	}
	
	return data_size;
}

ssize_t tls_send_file(gnutls_session_t session, const char *file)
{
FILE* fp;
char buf[512];
ssize_t len, total = 0;
int ret;

	fp = fopen(file, "r");
	
	while (	(len = fread( buf, 1, sizeof(buf), fp)) > 0) {
		ret = tls_send(session, buf, len);
		GNUTLS_FATAL_ERR(ret);
		
		total += ret;
	}
	
	fclose(fp);
	
	return total;
}

ssize_t tls_recv(gnutls_session_t session, void *data, size_t data_size)
{
	int ret;

	do {
		ret = gnutls_record_recv(session, data, data_size);
	} while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
	
	return ret;
}

int __attribute__ ((format(printf, 2, 3)))
    tls_printf(gnutls_session_t session, const char *fmt, ...)
{
	char buf[1024];
	va_list args;

	buf[1023] = 0;

	va_start(args, fmt);
	vsnprintf(buf, 1023, fmt, args);
	va_end(args);
	return tls_send(session, buf, strlen(buf));

}

void tls_close(gnutls_session_t session)
{
	gnutls_bye(session, GNUTLS_SHUT_WR);
	gnutls_deinit(session);
}

void tls_fatal_close(gnutls_session_t session,
			    gnutls_alert_description_t a)
{
	gnutls_alert_send(session, GNUTLS_AL_FATAL, a);
	gnutls_deinit(session);
}

static size_t rehash(const void *_e, void *unused)
{
const tls_cache_st *e = _e;

	return hash_stable_8(e->session_id, e->session_id_size, 0);
}

void tls_cache_init(hash_db_st** _db)
{
hash_db_st * db;

	db = malloc(sizeof(*db));
	if (db == NULL)
		exit(1);

	htable_init(&db->ht, rehash, NULL);
	db->entries = 0;

	*_db = db;
}

void tls_cache_deinit(hash_db_st* db)
{
tls_cache_st* cache;
struct htable_iter iter;

	cache = htable_first(&db->ht, &iter);
	while(cache != NULL) {
		if (cache->session_data_size > 0) {
	          	memset(cache->session_data, 0, cache->session_data_size);
	          	cache->session_data_size = 0;
	          	cache->session_id_size = 0;
		}
          	free(cache);
          	
          	cache = htable_next(&db->ht, &iter);
        }
        htable_clear(&db->ht);
	db->entries = 0;

        return;
}

static void tls_log_func(int level, const char *str)
{
	syslog(LOG_DEBUG, "TLS[<%d>]: %s", level, str);
}

static void tls_audit_log_func(gnutls_session_t session, const char *str)
{
worker_st * ws;

	if (session == NULL)
		syslog(LOG_AUTH, "warning: %s", str);
	else {
		ws = gnutls_session_get_ptr(session);
		
		oclog(ws, LOG_ERR, "warning: %s", str);
	}
}

static int verify_certificate_cb(gnutls_session_t session)
{
	unsigned int status;
	int ret;
	worker_st * ws;

	ws = gnutls_session_get_ptr(session);
	if (ws == NULL) {
		syslog(LOG_ERR, "%s:%d: could not obtain worker state.", __func__, __LINE__);
		return -1;
	}
	
	if (session == ws->dtls_session) /* no certificate is verified in DTLS */
		return 0;

	ws->cert_auth_ok = 0;

	/* This verification function uses the trusted CAs in the credentials
	 * structure. So you must have installed one or more CA certificates.
	 */
	ret = gnutls_certificate_verify_peers2(session, &status);
	if (ret < 0) {
		oclog(ws, LOG_ERR, "error verifying client certificate");
		goto fail;
	}

	if (status != 0) {
#if GNUTLS_VERSION_NUMBER > 0x030106
		gnutls_datum_t out;
		int type = gnutls_certificate_type_get(session);

		ret =
		    gnutls_certificate_verification_status_print(status, type,
							 &out, 0);
		if (ret < 0)
			goto fail;

		oclog(ws, LOG_INFO, "client certificate verification failed: %s", out.data);

		gnutls_free(out.data);
#else
		oclog(ws, LOG_INFO, "client certificate verification failed.");
#endif

		goto fail;
	} else {
		ws->cert_auth_ok = 1;
		oclog(ws, LOG_INFO, "client certificate verification succeeded");
	}

	/* notify gnutls to continue handshake normally */
	return 0;
fail:
	if (ws->config->force_cert_auth != 0)
		return GNUTLS_E_CERTIFICATE_ERROR;
	else
		return 0;

}

int pin_callback (void *user, int attempt, const char *token_url,
	const char *token_label, unsigned int flags, char *pin,
	size_t pin_max)
{
struct tls_st * ts = user;
int srk = 0;
const char* p;
unsigned len;

	if (flags & GNUTLS_PIN_FINAL_TRY) {
		syslog(LOG_ERR, "PIN callback: final try before locking; not attempting to unlock");
		return -1;
	}

	if (flags & GNUTLS_PIN_WRONG) {
		syslog(LOG_ERR, "PIN callback: wrong PIN was entered for '%s' (%s)", token_label, token_url);
		return -1;
	}

	if (ts->pin[0] == 0) {
		syslog(LOG_ERR, "PIN required for '%s' but pin-file was not set", token_label);
		return -1;
	}

	if (strcmp(token_url, "SRK") == 0 || strcmp(token_label, "SRK") == 0) {
		srk = 1;
		p = ts->srk_pin;
	} else {
		p = ts->pin;
	}

	if (srk != 0 && ts->srk_pin[0] == 0) {
		syslog(LOG_ERR, "PIN required for '%s' but srk-pin-file was not set", token_label);
		return -1;
	}
	
	len = strlen(p);
	if (len > pin_max-1) {
		syslog(LOG_ERR, "Too long PIN (%u chars)", len);
		return -1;
	}
	
	memcpy(pin, p, len);
	pin[len] = 0;
	
	return 0;
}

static
int load_pins(main_server_st* s)
{
int fd, ret;

	s->creds.srk_pin[0] = 0;
	s->creds.pin[0] = 0;

	if (s->config->srk_pin_file != NULL) {
		fd = open(s->config->srk_pin_file, O_RDONLY);
		if (fd < 0) {
			mslog(s, NULL, LOG_ERR, "could not open SRK PIN file '%s'", s->config->srk_pin_file);
			return -1;
		}
	
		ret = read(fd, s->creds.srk_pin, sizeof(s->creds.srk_pin));
		close(fd);
		if (ret <= 1) {
			mslog(s, NULL, LOG_ERR, "could not read from PIN file '%s'", s->config->srk_pin_file);
			return -1;
		}
	
		if (s->creds.srk_pin[ret-1] == '\n' || s->creds.srk_pin[ret-1] == '\r')
			s->creds.srk_pin[ret-1] = 0;
		s->creds.srk_pin[ret] = 0;
	}

	if (s->config->pin_file != NULL) {
		fd = open(s->config->pin_file, O_RDONLY);
		if (fd < 0) {
			mslog(s, NULL, LOG_ERR, "could not open PIN file '%s'", s->config->pin_file);
			return -1;
		}
	
		ret = read(fd, s->creds.pin, sizeof(s->creds.pin));
		close(fd);
		if (ret <= 1) {
			mslog(s, NULL, LOG_ERR, "could not read from PIN file '%s'", s->config->pin_file);
			return -1;
		}
	
		if (s->creds.pin[ret-1] == '\n' || s->creds.pin[ret-1] == '\r')
			s->creds.pin[ret-1] = 0;
		s->creds.pin[ret] = 0;
	}
	
	return 0;
}

void tls_global_init(main_server_st* s)
{
int ret;

	gnutls_global_set_audit_log_function(tls_audit_log_func);

	ret = gnutls_global_init();
	GNUTLS_FATAL_ERR(ret);
	
	return;
}

/* Checks, if there is a single certificate specified, whether it
 * is compatible with all ciphersuites */
static void certificate_check(main_server_st *s)
{
gnutls_datum_t data;
gnutls_x509_crt_t crt;
int ret;
unsigned usage;

	if (s->config->cert_size > 1)
		return;

#if GNUTLS_VERSION_NUMBER > 0x030100
	if (gnutls_url_is_supported(s->config->cert[0]) == 0) {
#endif
		/* no URL */
		ret = gnutls_load_file(s->config->cert[0], &data);
		if (ret < 0)
			return;
		
		ret = gnutls_x509_crt_init(&crt);
		GNUTLS_FATAL_ERR(ret);

		ret = gnutls_x509_crt_import(crt, &data, GNUTLS_X509_FMT_PEM);
		GNUTLS_FATAL_ERR(ret);
		
		ret = gnutls_x509_crt_get_pk_algorithm(crt, NULL);
		if (ret != GNUTLS_PK_RSA)
			goto cleanup;
		
		ret = gnutls_x509_crt_get_key_usage(crt, &usage, NULL);
		if (ret >= 0) {
			if (!(usage & GNUTLS_KEY_KEY_ENCIPHERMENT)) {
				mslog(s, NULL, LOG_WARNING, "server certificate key usage prevents key encipherment; unable to support the RSA ciphersuites\n");
				if (s->config->dh_params_file != NULL)
					mslog(s, NULL, LOG_WARNING, "no DH-params file specified; server will be limited to ECDHE ciphersuites\n");
			}
		}
#if GNUTLS_VERSION_NUMBER > 0x030100
	}
#endif

cleanup:
	gnutls_x509_crt_deinit(crt);
	gnutls_free(data.data);
	return;
}

static void set_dh_params(main_server_st* s, gnutls_certificate_credentials_t cred)
{
gnutls_datum_t data;
int ret;

	if (s->config->dh_params_file != NULL) {
		ret = gnutls_dh_params_init (&s->creds.dh_params);
		GNUTLS_FATAL_ERR(ret);

		ret = gnutls_load_file(s->config->dh_params_file, &data);
		GNUTLS_FATAL_ERR(ret);

		ret = gnutls_dh_params_import_pkcs3(s->creds.dh_params, &data, GNUTLS_X509_FMT_PEM);
		GNUTLS_FATAL_ERR(ret);

		gnutls_free(data.data);

		gnutls_certificate_set_dh_params(cred, s->creds.dh_params);
	}
}

/* reload key files etc. */
void tls_global_init_certs(main_server_st* s)
{
int ret;
unsigned i;
const char* perr;

	if (s->config->tls_debug) {
		gnutls_global_set_log_function(tls_log_func);
		gnutls_global_set_log_level(9);
	}

	if (s->creds.xcred != NULL)
		gnutls_certificate_free_credentials(s->creds.xcred);

	ret = gnutls_certificate_allocate_credentials(&s->creds.xcred);
	GNUTLS_FATAL_ERR(ret);

	ret = load_pins(s);
	if (ret < 0) {
		exit(1);
	}
	
	set_dh_params(s, s->creds.xcred);

	gnutls_certificate_set_pin_function (s->creds.xcred, pin_callback, &s->creds);
	
	if (s->config->key_size == 0 || s->config->cert_size == 0) {
		mslog(s, NULL, LOG_ERR, "no certificate or key files were specified.\n"); 
		exit(1);
	}

	certificate_check(s);
	
	for (i=0;i<s->config->key_size;i++) {
		if (strncmp(s->config->key[i], "pkcs11:", 7) != 0) {
			ret =
			    gnutls_certificate_set_x509_key_file(s->creds.xcred, s->config->cert[i],
						 s->config->key[i], GNUTLS_X509_FMT_PEM);
			if (ret < 0) {
				mslog(s, NULL, LOG_ERR, "error setting the certificate (%s) or key (%s) files: %s\n",
					s->config->cert[i], s->config->key[i], gnutls_strerror(ret));
				exit(1);
			}
		} else {
#ifndef HAVE_PKCS11
			mslog(s, NULL, LOG_ERR, "cannot load key, GnuTLS is compiled without pkcs11 support\n");
			exit(1);
#endif	
		}
	}

	if (s->config->cert_req != GNUTLS_CERT_IGNORE) {
		if (s->config->ca != NULL) {
			ret =
			    gnutls_certificate_set_x509_trust_file(s->creds.xcred,
								   s->config->ca,
								   GNUTLS_X509_FMT_PEM);
			if (ret < 0) {
				mslog(s, NULL, LOG_ERR, "error setting the CA (%s) file.\n",
					s->config->ca);
				exit(1);
			}

			mslog(s, NULL, LOG_INFO, "processed %d CA certificate(s).\n", ret);
		}

		if (s->config->crl != NULL) {
			ret =
			    gnutls_certificate_set_x509_crl_file(s->creds.xcred,
								 s->config->crl,
								 GNUTLS_X509_FMT_PEM);
			if (ret < 0) {
				mslog(s, NULL, LOG_ERR, "error setting the CRL (%s) file.\n",
					s->config->crl);
				exit(1);
			}
		}

		gnutls_certificate_set_verify_function(s->creds.xcred,
						       verify_certificate_cb);
	}

	ret = gnutls_priority_init(&s->creds.cprio, s->config->priorities, &perr);
	if (ret == GNUTLS_E_PARSING_ERROR)
		mslog(s, NULL, LOG_ERR, "error in TLS priority string: %s\n", perr);
	GNUTLS_FATAL_ERR(ret);
	
	ret = gnutls_session_ticket_key_generate(&s->creds.ticket_key);
	GNUTLS_FATAL_ERR(ret);
	
	if (s->config->ocsp_response != NULL) {
		ret = gnutls_certificate_set_ocsp_status_request_file(s->creds.xcred,
			s->config->ocsp_response, 0);
		GNUTLS_FATAL_ERR(ret);
	}
	
	return;
}

int tls_global_init_client(worker_st* ws)
{
#ifdef HAVE_PKCS11
int ret;
unsigned i;

	/* when we have PKCS #11 keys we cannot open them and then fork(), we need
	 * to open them at the process they are going to be used. */
	for (i=0;i<ws->config->key_size;i++) {
		if (strncmp(ws->config->key[i], "pkcs11:", 7) == 0) {
			ret = gnutls_pkcs11_reinit();
			if (ret < 0) {
				oclog(ws, LOG_ERR, "could not reinitialize PKCS #11 subsystem: %s\n",
					gnutls_strerror(ret));
				return -1;

			}

			ret =
			    gnutls_certificate_set_x509_key_file(ws->creds->xcred, ws->config->cert[i],
						 ws->config->key[i],
						 GNUTLS_X509_FMT_PEM);
			if (ret < 0) {
				oclog(ws, LOG_ERR, "error setting the certificate (%s) or key (%s) files: %s\n",
					ws->config->cert[i], ws->config->key[i], gnutls_strerror(ret));
				return -1;
			}
		}
	}
#endif

	return 0;
}

void tls_cork(gnutls_session_t session)
{
#if GNUTLS_VERSION_NUMBER > 0x030109
	gnutls_record_cork(session);
#endif
}

int tls_uncork(gnutls_session_t session)
{
#if GNUTLS_VERSION_NUMBER > 0x030109
	return gnutls_record_uncork(session, GNUTLS_RECORD_WAIT);
#else
	return 0;
#endif
}

void *calc_sha1_hash(char* file, unsigned cert)
{
int ret;
gnutls_datum_t data;
uint8_t digest[20];
char * retval;
gnutls_x509_crt_t crt;

	ret = gnutls_load_file(file, &data);
	if (ret < 0) {
		return NULL;
	}
	
	if (cert != 0) {
		ret = gnutls_x509_crt_init(&crt);
		GNUTLS_FATAL_ERR(ret);

		ret = gnutls_x509_crt_import(crt, &data, GNUTLS_X509_FMT_PEM);
		if (ret == GNUTLS_E_BASE64_DECODING_ERROR)
	  		ret = gnutls_x509_crt_import(crt, &data, GNUTLS_X509_FMT_DER);
		GNUTLS_FATAL_ERR(ret);

		gnutls_free(data.data);
	
		ret = gnutls_x509_crt_export2(crt, GNUTLS_X509_FMT_DER, &data);
		GNUTLS_FATAL_ERR(ret);
		gnutls_x509_crt_deinit(crt);
	}
	
	ret = gnutls_hash_fast(GNUTLS_DIG_SHA1, data.data, data.size, digest);
	gnutls_free(data.data);

	if (ret < 0) {
		fprintf(stderr, "Error calculating hash of '%s': %s\n", file, gnutls_strerror(ret));
		exit(1);
	}
	
	size_t ret_size = sizeof(digest)*2+1;
	retval = malloc(ret_size);
	if (retval == NULL) {
		fprintf(stderr, "Memory error\n");
		exit(1);
	}
	
	data.data = digest;
	data.size = sizeof(digest);
	ret = gnutls_hex_encode(&data, retval, &ret_size);
	if (ret < 0) {
		fprintf(stderr, "Error in hex encode: %s\n", gnutls_strerror(ret));
		exit(1);
	}
	retval[ret_size] = 0;
	
	return retval;
}