path: root/src/spf.c

/*
 * Copyright (c) 2009, Rambler media
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * 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 Rambler media ''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 Rambler 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 "evdns/evdns.h"
#include "spf.h"
#include "main.h"
#include "message.h"
#include "filter.h"

#define SPF_VER_STR "v=spf1"
#define SPF_ALL "all"
#define SPF_A "a"
#define SPF_IP4 "ip4"
#define SPF_IP6 "ip6"
#define SPF_PTR "ptr"
#define SPF_MX "mx"
#define SPF_EXISTS "exists"
#define SPF_INCLUDE "include"
#define SPF_REDIRECT "redirect"
#define SPF_EXP "exp"

/** SPF limits for avoiding abuse **/
#define SPF_MAX_NESTING 5
#define SPF_MAX_DNS_REQUESTS 10

/**
 * State machine for SPF record:
 *
 * spf_mech ::= +|-|~|?
 *
 * spf_body ::= spf=v1 <spf_command> [<spf_command>]
 * spf_command ::= [spf_mech]all|a|<ip4>|<ip6>|ptr|mx|<exists>|<include>|<redirect>
 *
 * spf_domain ::= [:domain][/mask]
 * spf_ip4 ::= ip[/mask]
 * ip4 ::= ip4:<spf_ip4>
 * mx ::= mx<spf_domain>
 * a ::= a<spf_domain>
 * ptr ::= ptr[:domain]
 * exists ::= exists:domain
 * include ::= include:domain
 * redirect ::= redirect:domain
 * exp ::= exp:domain
 *
 */

struct spf_dns_cb {
	struct spf_record *rec;
	struct spf_addr *addr;
	spf_action_t cur_action;
};

#define CHECK_REC(rec)										\
do {														\
	if ((rec)->nested > SPF_MAX_NESTING ||					\
		(rec)->dns_requests > SPF_MAX_DNS_REQUESTS) {		\
		return FALSE;										\
	}														\
} while (0)													\

static gboolean parse_spf_record (struct worker_task *task, struct spf_record *rec);
static void start_spf_parse (struct spf_record *rec, char *begin);

/* Determine spf mech */
static spf_mech_t
check_spf_mech (const char *elt, gboolean *need_shift)
{
	g_assert (elt != NULL);
	
	*need_shift = TRUE;

	switch (*elt) {
		case '-':
			return SPF_FAIL;
		case '~':
			return SPF_SOFT_FAIL;
		case '+':
			return SPF_PASS;
		case '?':
			return SPF_NEUTRAL;
		default:
			*need_shift = FALSE;
			return SPF_PASS;	
	}
}

static gboolean
parse_spf_ipmask (const char *begin, struct spf_addr *addr)
{
	const char *pos;
	char ip_buf[sizeof ("255.255.255.255")], mask_buf[3], *p;
	int state = 0, dots = 0;
	struct in_addr in;
	
	bzero (ip_buf, sizeof (ip_buf));
	bzero (mask_buf, sizeof (mask_buf));
	pos = begin;

	while (*pos) {
		switch (state) {
			case 0:
				/* Require ':' */
				if (*pos != ':') {
					return FALSE;
				}
				state = 1;
				pos ++;
				p = ip_buf;
				dots = 0;
				break;
			case 1:
				/* Begin parse ip */
				if (p - ip_buf >= sizeof (ip_buf) || dots > 3) {
					return FALSE;
				}
				if (g_ascii_isdigit (*pos)) {
					*p ++ = *pos ++;
				}
				else if (*pos == '.') {
					*p ++ = *pos ++;
					dots ++;
				}
				else if (*pos == '/') {
					pos ++;
					p = mask_buf;
					state = 2;
				}
				else {
					/* Invalid character */
					return FALSE;
				}
				break;
			case 2:
				/* Parse mask */
				if (p - mask_buf > 2) {
					return FALSE;
				}
				if (g_ascii_isdigit (*pos)) {
					*p ++ = *pos ++;
				}
				else {
					return FALSE;
				}
				break;
		}
	}

	if (!inet_aton (ip_buf, &in)) {
		return FALSE;
	}
	addr->addr = ntohl (in.s_addr);
	if (state == 2) {
		/* Also parse mask */
		addr->mask = (mask_buf[0] - '0') * 10 + mask_buf[1] - '0';
		if (addr->mask > 32) {
			msg_info ("parse_spf_ipmask: bad ipmask value: '%s'", begin);
			return FALSE;
		}
	}
	else {
		addr->mask = 32;
	}

	return TRUE;

}

static char *
parse_spf_hostmask (struct worker_task *task, const char *begin, struct spf_addr *addr, struct spf_record *rec)
{
	char *host = NULL, *p,  mask_buf[3];
	int hostlen;

	bzero (mask_buf, sizeof (mask_buf));
	if (*begin == '\0' || *begin == '/') {
		/* Assume host as host to resolve from record */
		host = rec->cur_domain;
	}
	p = strchr (begin, '/');
	if (p != NULL) {
		/* Extract mask */
		g_strlcpy (mask_buf, p + 1, sizeof (mask_buf));
		addr->mask = mask_buf[0] * 10 + mask_buf[1];
		if (addr->mask > 32) {
			return FALSE;
		}
		if (host == NULL) {
			hostlen = p - begin;
			host = memory_pool_alloc (task->task_pool, hostlen);
			g_strlcpy (host, begin, hostlen);
		}
	}
	else {
		addr->mask = 32;
		if (host == NULL) {
			g_strlcpy (host, begin, strlen (begin));
		}
	}

	return host;
}

static void
spf_record_dns_callback (int result, char type, int count, int ttl, void *addresses, void *data)
{
	struct spf_dns_cb *cb = data;
	char *begin;
	struct evdns_mx *mx;
	GList *tmp = NULL;

	if (result == DNS_ERR_NONE) {
		if (addresses != NULL) {
			/* Add all logic for all DNS states here */
			switch (cb->cur_action) {
				case SPF_RESOLVE_MX:
					if (type == DNS_MX) {
						mx = (struct evdns_mx *)addresses;
						/* Now resolve A record for this MX */
						if (evdns_resolve_ipv4 (mx->host, DNS_QUERY_NO_SEARCH, spf_record_dns_callback, (void *)cb) == 0) {
							return;
						}
					}
					else if (type == DNS_IPv4_A) {
						/* XXX: process only one record */
						cb->addr->addr = ntohl (*((uint32_t *)addresses));
					}
					break;
				case SPF_RESOLVE_A:
					if (type == DNS_IPv4_A) {
						/* XXX: process only one record */
						cb->addr->addr = ntohl (*((uint32_t *)addresses));
					}
					break;
				case SPF_RESOLVE_PTR:
					break;
				case SPF_RESOLVE_REDIRECT:
					if (type == DNS_TXT) {
						if (addresses != NULL) {
							begin = *(char **)addresses;
							if (cb->rec->addrs) {
								g_list_free (cb->rec->addrs);
								cb->rec->addrs = NULL;
							}
							start_spf_parse (cb->rec, begin);
						}
					}
					break;
				case SPF_RESOLVE_INCLUDE:
					if (type == DNS_TXT) {
						if (addresses != NULL) {
							begin = *(char **)addresses;
							if (cb->rec->addrs) {
								tmp = cb->rec->addrs;
								cb->rec->addrs = NULL;
							}
							start_spf_parse (cb->rec, begin);
							if (tmp) {
								cb->rec->addrs = g_list_concat (tmp, cb->rec->addrs);
							}
						}
					}
					break;
				case SPF_RESOLVE_EXP:
					break;
				case SPF_RESOLVE_EXISTS:
					if (type == DNS_IPv4_A) {
						/* If specified address resolves, we can accept connection from every IP */
						cb->addr->addr = ntohl (INADDR_ANY);
					}
					break;
			}
		}
	}

	cb->rec->task->save.saved--;
	if (cb->rec->task->save.saved == 0 && cb->rec->callback) {
		if (cb->rec->addrs) {
			cb->rec->callback (cb->rec, cb->rec->task);
			g_list_free (cb->rec->addrs);
			cb->rec->addrs = NULL;
		}
	}
	remove_forced_event (cb->rec->task->s, (event_finalizer_t) spf_record_dns_callback);

}

static gboolean
parse_spf_a (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	struct spf_dns_cb *cb;
	char *host;
	
	CHECK_REC (rec);
	
	if (begin == NULL || *begin != ':') {
		return FALSE;
	}
	begin ++;
	
	host = parse_spf_hostmask (task, begin, addr, rec);
	
	if (!host) {
		return FALSE;
	}

	rec->dns_requests ++;
	cb = memory_pool_alloc (task->task_pool, sizeof (struct spf_dns_cb));
	cb->rec = rec;
	cb->addr = addr;
	cb->cur_action = SPF_RESOLVE_A;

	if (evdns_resolve_ipv4 (host, DNS_QUERY_NO_SEARCH, spf_record_dns_callback, (void *)cb) == 0) {
		task->save.saved++;
		register_async_event (task->s, (event_finalizer_t) spf_record_dns_callback, NULL, TRUE);
		
		return TRUE;
	}

	return FALSE;

}

static gboolean
parse_spf_ptr (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	CHECK_REC (rec);
	
	msg_info ("parse_spf_ptr: ptr parsing is unimplemented");
	return FALSE;
}

static gboolean
parse_spf_mx (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	struct spf_dns_cb *cb;
	char *host;
	
	CHECK_REC (rec);
	
	if (begin == NULL) {
		return FALSE;
	}
	if (*begin == ':') {
		begin ++;
	}
	
	host = parse_spf_hostmask (task, begin, addr, rec);
	
	if (!host) {
		return FALSE;
	}

	rec->dns_requests ++;
	cb = memory_pool_alloc (task->task_pool, sizeof (struct spf_dns_cb));
	cb->rec = rec;
	cb->addr = addr;
	cb->cur_action = SPF_RESOLVE_MX;

	if (evdns_resolve_mx (host, DNS_QUERY_NO_SEARCH, spf_record_dns_callback, (void *)cb) == 0) {
		task->save.saved++;
		register_async_event (task->s, (event_finalizer_t) spf_record_dns_callback, NULL, TRUE);
		
		return TRUE;
	}

	return FALSE;
}

static gboolean
parse_spf_all (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	/* All is 0/0 */
	addr->addr = 0;
	addr->mask = 0;

	return TRUE;
}

static gboolean
parse_spf_ip4 (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	/* ip4:addr[/mask] */

	CHECK_REC (rec);
	return parse_spf_ipmask (begin, addr);
}

static gboolean
parse_spf_include (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	struct spf_dns_cb *cb;
	char              *domain;

	CHECK_REC (rec);

	if (begin == NULL || *begin != ':') {
		return FALSE;
	}
	begin ++;
	rec->dns_requests ++;

	cb = memory_pool_alloc (task->task_pool, sizeof (struct spf_dns_cb));
	cb->rec = rec;
	cb->addr = addr;
	cb->cur_action = SPF_RESOLVE_REDIRECT;
	domain = memory_pool_strdup (task->task_pool, begin);

	if (evdns_resolve_txt (domain, DNS_QUERY_NO_SEARCH, spf_record_dns_callback, (void *)cb) == 0) {
		task->save.saved++;
		register_async_event (task->s, (event_finalizer_t) spf_record_dns_callback, NULL, TRUE);
		
		return TRUE;
	}

	return FALSE;
}

static gboolean
parse_spf_exp (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	CHECK_REC (rec);

	msg_info ("parse_spf_exp: exp record is ignored");
	return TRUE;
}

static gboolean
parse_spf_redirect (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	struct spf_dns_cb *cb;
	char              *domain;

	CHECK_REC (rec);

	if (begin == NULL || *begin != '=') {
		return FALSE;
	}
	begin ++;
	rec->dns_requests ++;

	cb = memory_pool_alloc (task->task_pool, sizeof (struct spf_dns_cb));
	cb->rec = rec;
	cb->addr = addr;
	cb->cur_action = SPF_RESOLVE_INCLUDE;
	domain = memory_pool_strdup (task->task_pool, begin);

	if (evdns_resolve_txt (domain, DNS_QUERY_NO_SEARCH, spf_record_dns_callback, (void *)cb) == 0) {
		task->save.saved++;
		register_async_event (task->s, (event_finalizer_t) spf_record_dns_callback, NULL, TRUE);
		
		return TRUE;
	}

	return FALSE;
}

static gboolean
parse_spf_exists (struct worker_task *task, const char *begin, struct spf_record *rec, struct spf_addr *addr)
{
	struct spf_dns_cb *cb;
	char              *host;

	CHECK_REC (rec);
	
	if (begin == NULL || *begin != ':') {
		return FALSE;
	}
	begin ++;
	rec->dns_requests ++;

	cb = memory_pool_alloc (task->task_pool, sizeof (struct spf_dns_cb));
	cb->rec = rec;
	cb->addr = addr;
	cb->cur_action = SPF_RESOLVE_EXISTS;
	host = memory_pool_strdup (task->task_pool, begin);

	if (evdns_resolve_ipv4 (host, DNS_QUERY_NO_SEARCH, spf_record_dns_callback, (void *)cb) == 0) {
		task->save.saved++;
		register_async_event (task->s, (event_finalizer_t) spf_record_dns_callback, NULL, TRUE);
		
		return TRUE;
	}

	return FALSE;
}

#define NEW_ADDR(x) do {														\
	(x) = memory_pool_alloc (task->task_pool, sizeof (struct spf_addr));		\
	(x)->mech = check_spf_mech (rec->cur_elt, &need_shift);						\
	(x)->spf_string = memory_pool_strdup (task->task_pool, begin);				\
} while (0);

/* Read current element and try to parse record */
static gboolean
parse_spf_record (struct worker_task *task, struct spf_record *rec)
{
	struct spf_addr *new = NULL;
	gboolean need_shift, res = FALSE;
	char *begin;
	
	rec->cur_elt = rec->elts[rec->elt_num];
	if (rec->cur_elt == NULL) {
		return FALSE;
	}
	else {
		/* Check spf mech */
		if (need_shift) {
			rec->cur_elt ++;
		}
		begin = rec->cur_elt;
		if (*begin == '?' || *begin == '+' || *begin == '-' || *begin == '~') {
			begin ++;
		}


		/* Now check what we have */
		switch (*begin) {
			case 'a':
				/* all or a */
				if (strncmp (begin, SPF_ALL, sizeof (SPF_ALL) - 1) == 0) {
					NEW_ADDR (new);
					begin += sizeof (SPF_ALL) - 1;
					res = parse_spf_all (task, begin, rec, new);
				}
				else if (strncmp (begin, SPF_A, sizeof (SPF_A) - 1) == 0) {
					NEW_ADDR (new);
					begin += sizeof (SPF_A) - 1;
					res = parse_spf_a (task, begin, rec, new);
				}
				else {
					msg_info ("parse_spf_record: bad spf command: %s", begin);
				}
				break;
			case 'i':
				/* include or ip4 */
				if (strncmp (begin, SPF_IP4, sizeof (SPF_IP4) - 1) == 0) {
					NEW_ADDR (new);
					begin += sizeof (SPF_IP4) - 1;
					res = parse_spf_ip4 (task, begin, rec, new);
				}
				else if (strncmp (begin, SPF_INCLUDE, sizeof (SPF_INCLUDE) - 1) == 0) {
					begin += sizeof (SPF_INCLUDE) - 1;
					res = parse_spf_include (task, begin, rec, NULL);
				}
				else {
					msg_info ("parse_spf_record: bad spf command: %s", begin);
				}
				break;
			case 'm':
				/* mx */
				if (strncmp (begin, SPF_MX, sizeof (SPF_MX) - 1) == 0) {
					NEW_ADDR (new);
					begin += sizeof (SPF_MX) - 1;
					res = parse_spf_mx (task, begin, rec, new);
				}
				else {
					msg_info ("parse_spf_record: bad spf command: %s", begin);
				}
				break;
			case 'p':
				/* ptr */
				if (strncmp (begin, SPF_PTR, sizeof (SPF_PTR) - 1) == 0) {
					NEW_ADDR (new);
					begin += sizeof (SPF_PTR) - 1;
					res = parse_spf_ptr (task, begin, rec, new);
				}
				else {
					msg_info ("parse_spf_record: bad spf command: %s", begin);
				}
				break;
			case 'e':
				/* exp or exists */
				if (strncmp (begin, SPF_EXP, sizeof (SPF_EXP) - 1) == 0) {
					begin += sizeof (SPF_EXP) - 1;
					res = parse_spf_exp (task, begin, rec, NULL);
				}
				else if (strncmp (begin, SPF_EXISTS, sizeof (SPF_EXISTS) - 1) == 0) {
					NEW_ADDR (new);
					begin += sizeof (SPF_EXISTS) - 1;
					res = parse_spf_exists (task, begin, rec, new);
				}
				else {
					msg_info ("parse_spf_record: bad spf command: %s", begin);
				}
				break;
			case 'r':
				/* redirect */
				if (strncmp (begin, SPF_REDIRECT, sizeof (SPF_REDIRECT) - 1) == 0) {
					begin += sizeof (SPF_REDIRECT) - 1;
					res = parse_spf_redirect (task, begin, rec, NULL);
				}
				else {
					msg_info ("parse_spf_record: bad spf command: %s", begin);
				}
				break;
			default:
				msg_info ("parse_spf_record: bad spf command: %s", begin);
				break;
		}
		if (res) {
			if (new != NULL) {
				rec->addrs = g_list_prepend (rec->addrs, new);
			}
			rec->elt_num ++;
		}
	}

	return res;
}
#undef NEW_ADDR

static void
start_spf_parse (struct spf_record *rec, char *begin)
{
	if (strncmp (begin, SPF_VER_STR, sizeof (SPF_VER_STR) - 1) == 0) {
		begin += sizeof (SPF_VER_STR) - 1;
		while (g_ascii_isspace (*begin) && *begin) {
			begin ++;
		}
		rec->elts = g_strsplit (begin, " ", 0);
		rec->elt_num = 0;
		if (rec->elts) {
			memory_pool_add_destructor (rec->task->task_pool, (pool_destruct_func)g_strfreev, rec->elts);
			rec->cur_elt = rec->elts[0];
			while (parse_spf_record (rec->task, rec));
			if (rec->addrs) {
				rec->addrs = g_list_reverse (rec->addrs);
			}
		}
	}
	else {
		msg_info ("start_spf_parse: bad spf record version: %*s", sizeof (SPF_VER_STR) - 1, begin);
	}
}

static void
spf_dns_callback (int result, char type, int count, int ttl, void *addresses, void *data)
{
	struct spf_record *rec = data;
	char *begin;

	if (result == DNS_ERR_NONE && type == DNS_TXT) {
		if (addresses != NULL) {
			begin = *(char **)addresses;
			start_spf_parse (rec, begin);
		}
	}

	rec->task->save.saved--;
	if (rec->task->save.saved == 0 && rec->callback) {
		rec->callback (rec, rec->task);
	}
	remove_forced_event (rec->task->s, (event_finalizer_t) spf_dns_callback);

}


gboolean
resolve_spf (struct worker_task *task, spf_cb_t callback)
{
	struct spf_record *rec;
	char *domain;
	GList *domains;

	rec = memory_pool_alloc0 (task->task_pool, sizeof (struct spf_record));
	rec->task = task;
	rec->callback = callback;

	if (task->from && (domain = strchr (task->from, '@'))) {
		rec->cur_domain = memory_pool_strdup (task->task_pool, domain + 1);
		if ((domain = strchr (rec->cur_domain, '>')) != NULL) {
			*domain = '\0';
		}

		if (evdns_resolve_txt (rec->cur_domain, DNS_QUERY_NO_SEARCH, spf_dns_callback, (void *)rec) == 0) {
			task->save.saved++;
			register_async_event (task->s, (event_finalizer_t) spf_dns_callback, NULL, TRUE);

			return TRUE;
		}
	}
	else {
		domains = message_get_header (task->task_pool, task->message, "From");

		if (domains != NULL) {
			rec->cur_domain = memory_pool_strdup (task->task_pool, domains->data);
			g_list_free (domains);
			if ((domain = strchr (rec->cur_domain, '@')) == NULL) {
				return FALSE;
			}
			rec->cur_domain = domain + 1;

			if ((domain = strchr (rec->cur_domain, '>')) != NULL) {
				*domain = '\0';
			}
			if (evdns_resolve_txt (rec->cur_domain, DNS_QUERY_NO_SEARCH, spf_dns_callback, (void *)rec) == 0) {
				task->save.saved++;
				register_async_event (task->s, (event_finalizer_t) spf_dns_callback, NULL, TRUE);
	
				return TRUE;
			}
		}
	}

	return FALSE;
}

/* 
 * vi:ts=4 
 */