libpurple/dnssrv.c

/**
 * @file dnssrv.c
 */

/* purple
 *
 * Copyright (C) 2005 Thomas Butter <butter@uni-mannheim.de>
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02111-1301  USA
 */

#include "internal.h"
#include "util.h"

#ifndef _WIN32
#include <arpa/nameser.h>
#include <resolv.h>
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif
#ifndef T_SRV
#define T_SRV	33
#endif
#ifndef T_TXT
#define T_TXT	16
#endif
#else /* WIN32 */
#include <windns.h>
/* Missing from the mingw headers */
#ifndef DNS_TYPE_SRV
# define DNS_TYPE_SRV 33
#endif
#ifndef DNS_TYPE_TXT
# define DNS_TYPE_TXT 16
#endif
#endif

#include "dnssrv.h"
#include "eventloop.h"
#include "debug.h"

#ifndef _WIN32
typedef union {
	HEADER hdr;
	u_char buf[1024];
} queryans;
#else
static DNS_STATUS (WINAPI *MyDnsQuery_UTF8) (
	PCSTR lpstrName, WORD wType, DWORD fOptions,
	PIP4_ARRAY aipServers, PDNS_RECORD* ppQueryResultsSet,
	PVOID* pReserved) = NULL;
static void (WINAPI *MyDnsRecordListFree) (PDNS_RECORD pRecordList,
	DNS_FREE_TYPE FreeType) = NULL;
#endif

struct _PurpleTxtResponse {
    char *content;
};

struct _PurpleSrvQueryData {
	union {
		PurpleSrvCallback srv;
		PurpleTxtCallback txt;
	} cb;

	gpointer extradata;
	guint handle;
	int type;
#ifdef _WIN32
	GThread *resolver;
	char *query;
	char *error_message;
	GSList *results;
#else
	int fd_in, fd_out;
	pid_t pid;
#endif
};

typedef struct _PurpleSrvInternalQuery {
	int type;
	char query[256];
} PurpleSrvInternalQuery;

static gint
responsecompare(gconstpointer ar, gconstpointer br)
{
	PurpleSrvResponse *a = (PurpleSrvResponse*)ar;
	PurpleSrvResponse *b = (PurpleSrvResponse*)br;

	if(a->pref == b->pref) {
		if(a->weight == b->weight)
			return 0;
		if(a->weight < b->weight)
			return -1;
		return 1;
	}
	if(a->pref < b->pref)
		return -1;
	return 1;
}

#ifndef _WIN32

G_GNUC_NORETURN static void
resolve(int in, int out)
{
	GList *ret = NULL;
	PurpleSrvResponse *srvres;
	PurpleTxtResponse *txtres;
	queryans answer;
	int size;
	int qdcount;
	int ancount;
	guchar *end;
	guchar *cp;
	gchar name[256];
	guint16 type, dlen, pref, weight, port;
	PurpleSrvInternalQuery query;

#ifdef HAVE_SIGNAL_H
	purple_restore_default_signal_handlers();
#endif

	if (read(in, &query, sizeof(query)) <= 0) {
		close(out);
		close(in);
		_exit(0);
	}

	size = res_query( query.query, C_IN, query.type, (u_char*)&answer, sizeof( answer));
	
	qdcount = ntohs(answer.hdr.qdcount);
	ancount = ntohs(answer.hdr.ancount);
	cp = (guchar*)&answer + sizeof(HEADER);
	end = (guchar*)&answer + size;

	/* skip over unwanted stuff */
	while (qdcount-- > 0 && cp < end) {
		size = dn_expand( (unsigned char*)&answer, end, cp, name, 256);
		if(size < 0) goto end;
		cp += size + QFIXEDSZ;
	}

	while (ancount-- > 0 && cp < end) {
		size = dn_expand((unsigned char*)&answer, end, cp, name, 256);
		if(size < 0)
			goto end;
		cp += size;
		GETSHORT(type,cp);

		/* skip ttl and class since we already know it */
		cp += 6;

		GETSHORT(dlen,cp);
		if (query.type == T_SRV) {
			GETSHORT(pref,cp);

			GETSHORT(weight,cp);

			GETSHORT(port,cp);

			size = dn_expand( (unsigned char*)&answer, end, cp, name, 256);
			if(size < 0 )
				goto end;

			cp += size;

			srvres = g_new0(PurpleSrvResponse, 1);
			strcpy(srvres->hostname, name);
			srvres->pref = pref;
			srvres->port = port;
			srvres->weight = weight;

			ret = g_list_insert_sorted(ret, srvres, responsecompare);
		} else if (query.type == T_TXT) {
			txtres = g_new0(PurpleTxtResponse, 1);
			txtres->content = g_strndup((gchar*)(++cp), dlen-1);
			ret = g_list_append(ret, txtres);
			cp += dlen - 1;
		} else {
			cp += dlen;
		}
	}

end:
	size = g_list_length(ret);
	/* TODO: Check return value */
	write(out, &(query.type), sizeof(query.type));
	write(out, &size, sizeof(size));
	while (ret != NULL)
	{
		/* TODO: Check return value */
		if (query.type == T_SRV) write(out, ret->data, sizeof(PurpleSrvResponse));
		if (query.type == T_TXT) write(out, ret->data, sizeof(PurpleTxtResponse));
		g_free(ret->data);
		ret = g_list_remove(ret, ret->data);
	}

	close(out);
	close(in);

	_exit(0);
}

static void
resolved(gpointer data, gint source, PurpleInputCondition cond)
{
	int size;
	int type;
	PurpleSrvQueryData *query_data = (PurpleSrvQueryData*)data;
	int i;
	int status;
	
	if (read(source, &type, sizeof(type)) == sizeof(type)) {
		if (type == T_SRV) {
			PurpleSrvResponse *res;
			PurpleSrvResponse *tmp;
			PurpleSrvCallback cb = query_data->cb.srv;
			if (read(source, &size, sizeof(int)) == sizeof(int)) {
				ssize_t red;
				purple_debug_info("dnssrv","found %d SRV entries\n", size);
				tmp = res = g_new0(PurpleSrvResponse, size);
				for (i = 0; i < size; i++) {
					red = read(source, tmp++, sizeof(PurpleSrvResponse));
					if (red != sizeof(PurpleSrvResponse)) {
						purple_debug_error("dnssrv","unable to read srv "
								"response: %s\n", g_strerror(errno));
						size = 0;
						g_free(res);
						res = NULL;
					}
				}
			} else {
				purple_debug_info("dnssrv","found 0 SRV entries; errno is %i\n", errno);
				size = 0;
				res = NULL;
			}
			cb(res, size, query_data->extradata);
		} else if (type == T_TXT) {
			GSList *responses = NULL;
			PurpleTxtResponse *res;
			PurpleTxtCallback cb = query_data->cb.txt;
			if (read(source, &size, sizeof(int)) == sizeof(int)) {
				ssize_t red;
				purple_debug_info("dnssrv","found %d TXT entries\n", size);
				res = g_new0(PurpleTxtResponse, 1);
				for (i = 0; i < size; i++) {
					red = read(source, res, sizeof(PurpleTxtResponse));
					if (red != sizeof(PurpleTxtResponse)) {
						purple_debug_error("dnssrv","unable to read txt "
								"response: %s\n", g_strerror(errno));
						size = 0;
						g_free(res);
						g_slist_foreach(responses, (GFunc)purple_txt_response_destroy, NULL);
						g_slist_free(responses);
						responses = NULL;
						break;
					}
				}
			} else {
				purple_debug_info("dnssrv","found 0 TXT entries; errno is %i\n", errno);
			}
			cb(responses, query_data->extradata);			
		} else {
			purple_debug_info("dnssrv","type unknown of DNS result entry; errno is %i\n", errno);
		}
	}

	waitpid(query_data->pid, &status, 0);
	purple_srv_cancel(query_data);
}

#else /* _WIN32 */

/** The Jabber Server code was inspiration for parts of this. */

static gboolean
res_main_thread_cb(gpointer data)
{
	PurpleSrvResponse *srvres = NULL;
	int size = 0;
	PurpleSrvQueryData *query_data = data;
	if(query_data->error_message != NULL)
		purple_debug_error("dnssrv", query_data->error_message);
	else {
		if (query_data->type == DNS_TYPE_SRV) {
			PurpleSrvResponse *srvres_tmp = NULL;
			GSList *lst = query_data->results;

			size = g_slist_length(lst);

			if(query_data->cb.srv && size > 0)
				srvres_tmp = srvres = g_new0(PurpleSrvResponse, size);
			while (lst) {
				if(query_data->cb.srv)
					memcpy(srvres_tmp++, lst->data, sizeof(PurpleSrvResponse));
				g_free(lst->data);
				lst = g_slist_remove(lst, lst->data);
			}

			query_data->results = NULL;

			purple_debug_info("dnssrv", "found %d SRV entries\n", size);
			
			if(query_data->cb.srv) query_data->cb.srv(srvres, size, query_data->extradata);
		} else if (query_data->type == DNS_TYPE_TXT) {
			GSList *lst = query_data->results;

			purple_debug_info("dnssrv", "found %d TXT entries\n", g_slist_length(lst));
			
			if (query_data->cb.txt) {
				query_data->results = NULL;
				query_data->cb.txt(lst, query_data->extradata);
			}
		} else {
			purple_debug_error("dnssrv", "unknown query type");
		}
	}

	query_data->resolver = NULL;
	query_data->handle = 0;

	purple_srv_cancel(query_data);

	return FALSE;
}

static gpointer
res_thread(gpointer data)
{
	PDNS_RECORD dr = NULL;
	int type;
	DNS_STATUS ds;
	PurpleSrvQueryData *query_data = data;
	type = query_data->type;
	ds = MyDnsQuery_UTF8(query_data->query, type, DNS_QUERY_STANDARD, NULL, &dr, NULL);
	if (ds != ERROR_SUCCESS) {
		gchar *msg = g_win32_error_message(ds);
		if (type == DNS_TYPE_SRV) {
			query_data->error_message = g_strdup_printf("Couldn't look up SRV record. %s (%lu).\n", msg, ds);
		} else if (type == DNS_TYPE_TXT) {
			query_data->error_message = g_strdup_printf("Couldn't look up TXT record. %s (%lu).\n", msg, ds);
		}
		g_free(msg);
	} else {
		if (type == DNS_TYPE_SRV) {
			PDNS_RECORD dr_tmp;
			GSList *lst = NULL;
			DNS_SRV_DATA *srv_data;
			PurpleSrvResponse *srvres;
			
			for (dr_tmp = dr; dr_tmp != NULL; dr_tmp = dr_tmp->pNext) {
				/* Discard any incorrect entries. I'm not sure if this is necessary */
				if (dr_tmp->wType != type || strcmp(dr_tmp->pName, query_data->query) != 0) {
					continue;
				}

				srv_data = &dr_tmp->Data.SRV;
				srvres = g_new0(PurpleSrvResponse, 1);
				strncpy(srvres->hostname, srv_data->pNameTarget, 255);
				srvres->hostname[255] = '\0';
				srvres->pref = srv_data->wPriority;
				srvres->port = srv_data->wPort;
				srvres->weight = srv_data->wWeight;
				
				lst = g_slist_insert_sorted(lst, srvres, responsecompare);
			}

			MyDnsRecordListFree(dr, DnsFreeRecordList);
			query_data->results = lst;
		} else if (type == DNS_TYPE_TXT) {
			PDNS_RECORD dr_tmp;
			GSList *lst = NULL;
			DNS_TXT_DATA *txt_data;
			PurpleTxtResponse *txtres;

			for (dr_tmp = dr; dr_tmp != NULL; dr_tmp = dr_tmp->pNext) {
				GString *s;
				int i;

				/* Discard any incorrect entries. I'm not sure if this is necessary */
				if (dr_tmp->wType != type || strcmp(dr_tmp->pName, query_data->query) != 0) {
					continue;
				}

				txt_data = &dr_tmp->Data.TXT;
				txtres = g_new0(PurpleTxtResponse, 1);

				s = g_string_new("");
				for (i = 0; i < txt_data->dwStringCount; ++i)
					s = g_string_append(s, txt_data->pStringArray[i]);
				txtres->content = g_string_free(s, FALSE);

				lst = g_slist_append(lst, txtres);
			}

			MyDnsRecordListFree(dr, DnsFreeRecordList);
			query_data->results = lst;
		} else {
			
		}
	}

	/* back to main thread */
	/* Note: this should *not* be attached to query_data->handle - it will cause leakage */
	purple_timeout_add(0, res_main_thread_cb, query_data);

	g_thread_exit(NULL);
	return NULL;
}

#endif

PurpleSrvQueryData *
purple_srv_resolve(const char *protocol, const char *transport, const char *domain, PurpleSrvCallback cb, gpointer extradata)
{
	char *query;
	PurpleSrvQueryData *query_data;
#ifndef _WIN32
	PurpleSrvInternalQuery internal_query;
	int in[2], out[2];
	int pid;
#else
	GError* err = NULL;
	static gboolean initialized = FALSE;
#endif

	if (!protocol || !*protocol || !transport || !*transport || !domain || !*domain) {
		purple_debug_error("dnssrv", "Wrong arguments\n");
		cb(NULL, 0, extradata);
		g_return_val_if_reached(NULL);
	}

	query = g_strdup_printf("_%s._%s.%s", protocol, transport, domain);
	purple_debug_info("dnssrv","querying SRV record for %s\n", query);

#ifndef _WIN32
	if(pipe(in) || pipe(out)) {
		purple_debug_error("dnssrv", "Could not create pipe\n");
		g_free(query);
		cb(NULL, 0, extradata);
		return NULL;
	}

	pid = fork();
	if (pid == -1) {
		purple_debug_error("dnssrv", "Could not create process!\n");
		cb(NULL, 0, extradata);
		g_free(query);
		return NULL;
	}

	/* Child */
	if (pid == 0)
	{
		g_free(query);

		close(out[0]);
		close(in[1]);
		resolve(in[0], out[1]);
		/* resolve() does not return */
	}

	close(out[1]);
	close(in[0]);

	internal_query.type = T_SRV;
	strncpy(internal_query.query, query, 255);
	
	if (write(in[1], &internal_query, sizeof(internal_query)) < 0)
		purple_debug_error("dnssrv", "Could not write to SRV resolver\n");
	

	query_data = g_new0(PurpleSrvQueryData, 1);
	query_data->type = T_SRV;
	query_data->cb.srv = cb;
	query_data->extradata = extradata;
	query_data->pid = pid;
	query_data->fd_out = out[0];
	query_data->fd_in = in[1];
	query_data->handle = purple_input_add(out[0], PURPLE_INPUT_READ, resolved, query_data);

	g_free(query);

	return query_data;
#else
	if (!initialized) {
		MyDnsQuery_UTF8 = (void*) wpurple_find_and_loadproc("dnsapi.dll", "DnsQuery_UTF8");
		MyDnsRecordListFree = (void*) wpurple_find_and_loadproc(
			"dnsapi.dll", "DnsRecordListFree");
		initialized = TRUE;
	}

	query_data = g_new0(PurpleSrvQueryData, 1);
	query_data->type = DNS_TYPE_SRV;
	query_data->cb.srv = cb;
	query_data->query = query;
	query_data->extradata = extradata;

	if (!MyDnsQuery_UTF8 || !MyDnsRecordListFree)
		query_data->error_message = g_strdup("System missing DNS API (Requires W2K+)\n");
	else {
		query_data->resolver = g_thread_create(res_thread, query_data, FALSE, &err);
		if (query_data->resolver == NULL) {
			query_data->error_message = g_strdup_printf("SRV thread create failure: %s\n", (err && err->message) ? err->message : "");
			g_error_free(err);
		}
	}

	/* The query isn't going to happen, so finish the SRV lookup now.
	 * Asynchronously call the callback since stuff may not expect
	 * the callback to be called before this returns */
	if (query_data->error_message != NULL)
		query_data->handle = purple_timeout_add(0, res_main_thread_cb, query_data);

	return query_data;
#endif
}

PurpleSrvQueryData *purple_txt_resolve(const char *owner, const char *domain, PurpleTxtCallback cb, gpointer extradata)
{
	char *query;
	PurpleSrvQueryData *query_data;
#ifndef _WIN32
	PurpleSrvInternalQuery internal_query;
	int in[2], out[2];
	int pid;
#else
	GError* err = NULL;
	static gboolean initialized = FALSE;
#endif

	query = g_strdup_printf("%s.%s", owner, domain);
	purple_debug_info("dnssrv","querying TXT record for %s\n", query);

#ifndef _WIN32
	if(pipe(in) || pipe(out)) {
		purple_debug_error("dnssrv", "Could not create pipe\n");
		g_free(query);
		cb(NULL, extradata);
		return NULL;
	}

	pid = fork();
	if (pid == -1) {
		purple_debug_error("dnssrv", "Could not create process!\n");
		cb(NULL, extradata);
		g_free(query);
		return NULL;
	}

	/* Child */
	if (pid == 0)
	{
		g_free(query);

		close(out[0]);
		close(in[1]);
		resolve(in[0], out[1]);
		/* resolve() does not return */
	}

	close(out[1]);
	close(in[0]);
	
	internal_query.type = T_TXT;
	strncpy(internal_query.query, query, 255);
	
	if (write(in[1], &internal_query, sizeof(internal_query)) < 0)
		purple_debug_error("dnssrv", "Could not write to TXT resolver\n");

	query_data = g_new0(PurpleSrvQueryData, 1);
	query_data->type = T_TXT;
	query_data->cb.txt = cb;
	query_data->extradata = extradata;
	query_data->pid = pid;
	query_data->fd_out = out[0];
	query_data->fd_in = in[1];
	query_data->handle = purple_input_add(out[0], PURPLE_INPUT_READ, resolved, query_data);

	g_free(query);

	return query_data;
#else
	if (!initialized) {
		MyDnsQuery_UTF8 = (void*) wpurple_find_and_loadproc("dnsapi.dll", "DnsQuery_UTF8");
		MyDnsRecordListFree = (void*) wpurple_find_and_loadproc(
			"dnsapi.dll", "DnsRecordListFree");
		initialized = TRUE;
	}

	query_data = g_new0(PurpleSrvQueryData, 1);
	query_data->type = DNS_TYPE_TXT;
	query_data->cb.txt = cb;
	query_data->query = query;
	query_data->extradata = extradata;

	if (!MyDnsQuery_UTF8 || !MyDnsRecordListFree)
		query_data->error_message = g_strdup("System missing DNS API (Requires W2K+)\n");
	else {
		query_data->resolver = g_thread_create(res_thread, query_data, FALSE, &err);
		if (query_data->resolver == NULL) {
			query_data->error_message = g_strdup_printf("TXT thread create failure: %s\n", (err && err->message) ? err->message : "");
			g_error_free(err);
		}
	}

	/* The query isn't going to happen, so finish the TXT lookup now.
	 * Asynchronously call the callback since stuff may not expect
	 * the callback to be called before this returns */
	if (query_data->error_message != NULL)
		query_data->handle = purple_timeout_add(0, res_main_thread_cb, query_data);

	return query_data;
#endif
}

void
purple_srv_cancel(PurpleSrvQueryData *query_data)
{
	if (query_data->handle > 0)
		purple_input_remove(query_data->handle);
#ifdef _WIN32
	if (query_data->resolver != NULL)
	{
		/*
		 * It's not really possible to kill a thread.  So instead we
		 * just set the callback to NULL and let the DNS lookup
		 * finish.
		 */
		query_data->cb.srv = NULL;
		return;
	}
	g_free(query_data->query);
	g_free(query_data->error_message);
#else
	close(query_data->fd_out);
	close(query_data->fd_in);
#endif
	g_free(query_data);
}

void
purple_txt_cancel(PurpleSrvQueryData *query_data)
{
	purple_srv_cancel(query_data);
}

const gchar *
purple_txt_response_get_content(PurpleTxtResponse *resp)
{
	g_return_val_if_fail(resp != NULL, NULL);

	return resp->content;
}

void purple_txt_response_destroy(PurpleTxtResponse *resp)
{
	g_return_if_fail(resp != NULL);

	g_free(resp->content);
	g_free(resp);
}