/*
 * LibSylph -- E-Mail client library
 * Copyright (C) 1999-2014 Hiroyuki Yamamoto
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#if USE_SSL

#include "defs.h"

#include <glib.h>
#include <glib/gi18n.h>

#include "utils.h"
#include "ssl.h"
#include "ssl_hostname_validation.h"

static SSL_CTX *ssl_ctx_SSLv23 = NULL;
static SSL_CTX *ssl_ctx_TLSv1 = NULL;

static GSList *trust_list = NULL;
static GSList *tmp_trust_list = NULL;
static GSList *reject_list = NULL;

static SSLVerifyFunc verify_ui_func = NULL;

static gchar *find_certs_file(const gchar *certs_dir)
{
	gchar *certs_file;

#define LOOK_FOR(crt)							   \
{									   \
	certs_file = g_strconcat(certs_dir, G_DIR_SEPARATOR_S, crt, NULL); \
	debug_print("looking for %s\n", certs_file);			   \
	if (is_file_exist(certs_file))					   \
		return certs_file;					   \
	g_free(certs_file);						   \
}

	if (certs_dir) {
		LOOK_FOR("ca-certificates.crt");
		LOOK_FOR("ca-bundle.crt");
		LOOK_FOR("ca-root.crt");
		LOOK_FOR("certs.crt");
	}

#undef LOOK_FOR

	return NULL;
}

void ssl_init(void)
{
	gchar *certs_file, *certs_dir;
	FILE *fp;

	SSL_library_init();
	SSL_load_error_strings();

	certs_dir = g_strconcat(get_rc_dir(), G_DIR_SEPARATOR_S, "certs", NULL);
	if (!is_dir_exist(certs_dir)) {
		debug_print("ssl_init(): %s doesn't exist, or not a directory.\n",
			    certs_dir);
		g_free(certs_dir);
#ifdef G_OS_WIN32
		certs_dir = g_strconcat(get_startup_dir(), G_DIR_SEPARATOR_S
					"etc" G_DIR_SEPARATOR_S
					"ssl" G_DIR_SEPARATOR_S "certs", NULL);
#else
		certs_dir = g_strdup("/etc/ssl/certs");
#endif
		if (!is_dir_exist(certs_dir)) {
			debug_print("ssl_init(): %s doesn't exist, or not a directory.\n",
				    certs_dir);
			g_free(certs_dir);
			certs_dir = NULL;
		}
	}
	if (certs_dir)
		debug_print("ssl_init(): certs dir %s found.\n", certs_dir);

	certs_file = find_certs_file(get_rc_dir());

	if (certs_dir && !certs_file)
		certs_file = find_certs_file(certs_dir);

	if (!certs_file) {
#ifdef G_OS_WIN32
		certs_dir = g_strconcat(get_startup_dir(),
					G_DIR_SEPARATOR_S "etc"
					G_DIR_SEPARATOR_S "ssl", NULL);
		certs_file = find_certs_file(certs_dir);
		g_free(certs_dir);
		certs_dir = NULL;
		if (!certs_file) {
			certs_dir = g_strconcat(get_startup_dir(),
						G_DIR_SEPARATOR_S "etc", NULL);
			certs_file = find_certs_file(certs_dir);
			g_free(certs_dir);
			certs_dir = NULL;
		}
#else
		certs_file = find_certs_file("/etc/ssl");
		if (!certs_file)
			certs_file = find_certs_file("/etc");
#endif
	}

	if (certs_file)
		debug_print("ssl_init(): certs file %s found.\n", certs_file);

	ssl_ctx_SSLv23 = SSL_CTX_new(SSLv23_client_method());
	if (ssl_ctx_SSLv23 == NULL) {
		debug_print(_("SSLv23 not available\n"));
	} else {
		debug_print(_("SSLv23 available\n"));
		if ((certs_file || certs_dir) &&
		    !SSL_CTX_load_verify_locations(ssl_ctx_SSLv23, certs_file,
						   certs_dir))
			g_warning("SSLv23 SSL_CTX_load_verify_locations failed.\n");
	}

	/* ssl_ctx_TLSv1 = SSL_CTX_new(TLSv1_client_method()); */
	ssl_ctx_TLSv1 = SSL_CTX_new(SSLv23_client_method());
	if (ssl_ctx_TLSv1 == NULL) {
		debug_print(_("TLSv1 not available\n"));
	} else {
		debug_print(_("TLSv1 available\n"));
		/* disable SSLv2/SSLv3 */
		SSL_CTX_set_options(ssl_ctx_TLSv1,
				    SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3);
		if ((certs_file || certs_dir) &&
		    !SSL_CTX_load_verify_locations(ssl_ctx_TLSv1, certs_file,
						   certs_dir))
			g_warning("TLSv1 SSL_CTX_load_verify_locations failed.\n");
	}

	g_free(certs_dir);
	g_free(certs_file);

	certs_file = g_strconcat(get_rc_dir(), G_DIR_SEPARATOR_S, "trust.crt",
				 NULL);
	if ((fp = g_fopen(certs_file, "rb")) != NULL) {
		X509 *cert;

		debug_print("ssl_init(): reading trust.crt\n");

		while ((cert = PEM_read_X509(fp, NULL, NULL, NULL)) != NULL)
			trust_list = g_slist_append(trust_list, cert);
		fclose(fp);
	}
	g_free(certs_file);
}

void ssl_done(void)
{
	gchar *trust_file;
	GSList *cur;
	FILE *fp;

	if (trust_list) {
		trust_file = g_strconcat(get_rc_dir(), G_DIR_SEPARATOR_S,
					 "trust.crt", NULL);
		if ((fp = g_fopen(trust_file, "wb")) == NULL) {
			FILE_OP_ERROR(trust_file, "fopen");
		}
		for (cur = trust_list; cur != NULL; cur = cur->next) {
			if (fp && !PEM_write_X509(fp, (X509 *)cur->data))
				g_warning("can't write X509 to PEM file: %s",
					  trust_file);
			X509_free((X509 *)cur->data);
		}
		if (fp)
			fclose(fp);
		g_free(trust_file);
		g_slist_free(trust_list);
		trust_list = NULL;
	}
	for (cur = tmp_trust_list; cur != NULL; cur = cur->next)
		X509_free((X509 *)cur->data);
	g_slist_free(tmp_trust_list);
	tmp_trust_list = NULL;
	for (cur = reject_list; cur != NULL; cur = cur->next)
		X509_free((X509 *)cur->data);
	g_slist_free(reject_list);
	reject_list = NULL;

	if (ssl_ctx_SSLv23) {
		SSL_CTX_free(ssl_ctx_SSLv23);
		ssl_ctx_SSLv23 = NULL;
	}

	if (ssl_ctx_TLSv1) {
		SSL_CTX_free(ssl_ctx_TLSv1);
		ssl_ctx_TLSv1 = NULL;
	}
}

gboolean ssl_init_socket(SockInfo *sockinfo)
{
	return ssl_init_socket_with_method(sockinfo, SSL_METHOD_SSLv23);
}

static gint x509_cmp_func(gconstpointer a, gconstpointer b)
{
	const X509 *xa = a;
	const X509 *xb = b;

	return X509_cmp(xa, xb);
}

gboolean ssl_init_socket_with_method(SockInfo *sockinfo, SSLMethod method)
{
	X509 *server_cert;
	gint err, ret;

	switch (method) {
	case SSL_METHOD_SSLv23:
		if (!ssl_ctx_SSLv23) {
			g_warning(_("SSL method not available\n"));
			return FALSE;
		}
		sockinfo->ssl = SSL_new(ssl_ctx_SSLv23);
		break;
	case SSL_METHOD_TLSv1:
		if (!ssl_ctx_TLSv1) {
			g_warning(_("SSL method not available\n"));
			return FALSE;
		}
		sockinfo->ssl = SSL_new(ssl_ctx_TLSv1);
		break;
	default:
		g_warning(_("Unknown SSL method *PROGRAM BUG*\n"));
		return FALSE;
		break;
	}

	if (sockinfo->ssl == NULL) {
		g_warning(_("Error creating ssl context\n"));
		return FALSE;
	}

	SSL_set_fd(sockinfo->ssl, sockinfo->sock);
	while ((ret = SSL_connect(sockinfo->ssl)) != 1) {
		err = SSL_get_error(sockinfo->ssl, ret);
		if (err == SSL_ERROR_WANT_READ || err == SSL_ERROR_WANT_WRITE) {
			g_usleep(100000);
			g_warning("SSL_connect(): try again\n");
			continue;
		}
		g_warning("SSL_connect() failed with error %d, ret = %d (%s)\n",
			  err, ret, ERR_error_string(ERR_get_error(), NULL));
		return FALSE;
	}

	/* Get the cipher */

	debug_print(_("SSL connection using %s\n"),
		    SSL_get_cipher(sockinfo->ssl));
	debug_print("SSL protocol version: %s\n",
		    SSL_get_version(sockinfo->ssl));

	/* Get server's certificate (note: beware of dynamic allocation) */

	if ((server_cert = SSL_get_peer_certificate(sockinfo->ssl)) != NULL) {
		glong verify_result;
		gboolean expired = FALSE;

		if (get_debug_mode()) {
			gchar *str;
			guchar keyid[EVP_MAX_MD_SIZE];
			gchar keyidstr[EVP_MAX_MD_SIZE * 3 + 1] = "";
			guint keyidlen = 0;
			gint i;
	
			debug_print(_("Server certificate:\n"));

			if ((str = X509_NAME_oneline(X509_get_subject_name(server_cert), 0, 0)) != NULL) {
				debug_print(_("  Subject: %s\n"), str);
				OPENSSL_free(str);
			}

			if ((str = X509_NAME_oneline(X509_get_issuer_name(server_cert), 0, 0)) != NULL) {
				debug_print(_("  Issuer: %s\n"), str);
				OPENSSL_free(str);
			}
			if (X509_digest(server_cert, EVP_sha1(), keyid, &keyidlen)) {
				for (i = 0; i < keyidlen; i++)
				g_snprintf(keyidstr + i * 3, 4, "%02x:", keyid[i]);
				keyidstr[keyidlen * 3 - 1] = '\0';
				debug_print("  SHA1 fingerprint: %s\n", keyidstr);
			}
			if (X509_digest(server_cert, EVP_md5(), keyid, &keyidlen)) {
				for (i = 0; i < keyidlen; i++)
				g_snprintf(keyidstr + i * 3, 4, "%02x:", keyid[i]);
				keyidstr[keyidlen * 3 - 1] = '\0';
				debug_print("  MD5 fingerprint: %s\n", keyidstr);
			}
		}

		verify_result = SSL_get_verify_result(sockinfo->ssl);
		if (verify_result == X509_V_OK) {
			debug_print("SSL certificate verify OK\n");
			if (ssl_validate_hostname(sockinfo->hostname, server_cert) == SSL_HOSTNAME_MATCH_FOUND) {
				debug_print("SSL certificate hostname validation OK\n");
				X509_free(server_cert);
				return TRUE;
			} else {
				verify_result = X509_V_ERR_APPLICATION_VERIFICATION;
			}
		}

		if (verify_result == X509_V_ERR_CERT_HAS_EXPIRED) {
			log_message("SSL certificate of %s has expired\n", sockinfo->hostname);
			expired = TRUE;
		} else if (g_slist_find_custom(trust_list, server_cert,
					       x509_cmp_func) ||
			   g_slist_find_custom(tmp_trust_list, server_cert,
					       x509_cmp_func)) {
			log_message("SSL certificate of %s previously accepted\n", sockinfo->hostname);
			X509_free(server_cert);
			return TRUE;
		} else if (g_slist_find_custom(reject_list, server_cert,
					       x509_cmp_func)) {
			log_message("SSL certificate of %s previously rejected\n", sockinfo->hostname);
			X509_free(server_cert);
			return FALSE;
		}

		if (verify_result == X509_V_ERR_APPLICATION_VERIFICATION) {
			g_warning("%s: SSL hostname validation failed\n",
				  sockinfo->hostname);
		} else {
			g_warning("%s: SSL certificate verify failed (%ld: %s)\n",
				  sockinfo->hostname, verify_result,
				  X509_verify_cert_error_string(verify_result));
		}

		if (verify_ui_func) {
			gint res;

			res = verify_ui_func(sockinfo, sockinfo->hostname,
					     server_cert, verify_result);
			/* 0: accept 1: temporarily accept -1: reject */
			if (res < 0) {
				debug_print("SSL certificate of %s rejected\n",
					    sockinfo->hostname);
#if 0
				reject_list = g_slist_prepend
					(reject_list, X509_dup(server_cert));
#endif
				X509_free(server_cert);
				return FALSE;
			} else if (res > 0) {
				debug_print("Temporarily accept SSL certificate of %s\n", sockinfo->hostname);
				if (!expired)
					tmp_trust_list = g_slist_prepend(tmp_trust_list, X509_dup(server_cert));
			} else {
				debug_print("Permanently accept SSL certificate of %s\n", sockinfo->hostname);
				if (!expired)
					trust_list = g_slist_prepend(trust_list, X509_dup(server_cert));
			}
		}

		X509_free(server_cert);
	} else {
		g_warning("%s: couldn't get SSL certificate\n",
			  sockinfo->hostname);
		return FALSE;
	}

	return TRUE;
}

void ssl_done_socket(SockInfo *sockinfo)
{
	if (sockinfo->ssl) {
		SSL_free(sockinfo->ssl);
	}
}

void ssl_set_verify_func(SSLVerifyFunc func)
{
	verify_ui_func = func;
}

#endif /* USE_SSL */
