mailsrvr.c

/* Synchronet Mail (SMTP/POP3) server and sendmail threads */

/* $Id: mailsrvr.c,v 1.735 2020/10/22 19:04:06 rswindell Exp $ */
// vi: tabstop=4

/****************************************************************************
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 * Copyright Rob Swindell - http://www.synchro.net/copyright.html			*
 *																			*
 * 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.					*
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/* ANSI C Library headers */
#include <limits.h>			/* UINT_MAX */
#include <stdio.h>
#include <stdlib.h>			/* ltoa in GNU C lib */
#include <stdarg.h>			/* va_list */
#include <string.h>			/* strrchr */
#include <ctype.h>			/* isdigit */
#include <fcntl.h>			/* Open flags */
#include <errno.h>			/* errno */

/* Synchronet-specific headers */
#undef SBBS	/* this shouldn't be defined unless building sbbs.dll/libsbbs.so */
#include "sbbs.h"
#include "mailsrvr.h"
#include "utf8.h"
#include "mime.h"
#include "md5.h"
#include "crc32.h"
#include "base64.h"
#include "ini_file.h"
#include "netwrap.h"	/* getNameServerList() */
#include "xpendian.h"
#include "js_rtpool.h"
#include "js_request.h"
#include "multisock.h"
#include "ssl.h"
#include "cryptlib.h"

/* Constants */
static const char*	server_name="Synchronet Mail Server";
#define FORWARD			"forward:"
#define NO_FORWARD		"local:"
#define NO_SPAM			"#nospam"

int dns_getmx(char* name, char* mx, char* mx2
			  ,DWORD intf, DWORD ip_addr, BOOL use_tcp, int timeout);

#define pop_error		"-ERR System Error: %s, try again later"
#define pop_auth_error	"-ERR Authentication failure"
#define ok_rsp			"250 OK"
#define auth_ok			"235 User Authenticated"
#define smtp_error		"421 System Error: %s, try again later"
#define insuf_stor		"452 Insufficient system storage"
#define badarg_rsp 		"501 Bad argument"
#define badseq_rsp		"503 Bad sequence of commands"
#define badauth_rsp		"535 Authentication failure"
#define badrsp_err		"%s replied with:\r\n\"%s\"\r\ninstead of the expected reply:\r\n\"%s ...\""

#define TIMEOUT_THREAD_WAIT		60		/* Seconds */
#define DNSBL_THROTTLE_VALUE	1000	/* Milliseconds */
#define SMTP_MAX_BAD_CMDS		9

#define STATUS_WFC	"Listening"

static mail_startup_t* startup=NULL;
static scfg_t	scfg;
static char*	text[TOTAL_TEXT];
static struct xpms_set	*mail_set=NULL;
static BOOL terminated=FALSE;
static protected_uint32_t active_clients;
static protected_uint32_t thread_count;
static volatile int		active_sendmail=0;
static volatile BOOL	sendmail_running=FALSE;
static volatile BOOL	terminate_server=FALSE;
static volatile BOOL	terminate_sendmail=FALSE;
static sem_t	sendmail_wakeup_sem;
static char		revision[16];
static volatile time_t	uptime;
static str_list_t recycle_semfiles;
static str_list_t shutdown_semfiles;
static int		mailproc_count;
static js_server_props_t js_server_props;
static link_list_t current_logins;
static link_list_t current_connections;

static const char* servprot_smtp = "SMTP";
static const char* servprot_submission = "SMTP";
static const char* servprot_submissions = "SMTPS";
static const char* servprot_pop3 = "POP3";
static const char* servprot_pop3s = "POP3S";

struct {
	volatile ulong	sockets;
	volatile ulong	errors;
	volatile ulong	crit_errors;
	volatile ulong	connections_exceeded;
	volatile ulong	connections_ignored;
	volatile ulong	connections_refused;
	volatile ulong	connections_served;
	volatile ulong	pop3_served;
	volatile ulong	smtp_served;
	/* SMTP: */
	volatile ulong	sessions_refused;
	volatile ulong	msgs_ignored;
	volatile ulong	msgs_refused;
	volatile ulong	msgs_received;
} stats;

struct mailproc {
	char		name[INI_MAX_VALUE_LEN];
	char		cmdline[INI_MAX_VALUE_LEN];
	char		eval[INI_MAX_VALUE_LEN];
	str_list_t	to;
	str_list_t	from;
	BOOL		passthru;
	BOOL		native;
	BOOL		ignore_on_error;	/* Ignore mail message if cmdline fails */
	BOOL		disabled;
	BOOL		process_spam;
	BOOL		process_dnsbl;
	uint8_t*	ar;
	ulong		handled;			/* counter (for stats display) */
} *mailproc_list;

typedef struct {
	SOCKET			socket;
	union xp_sockaddr	client_addr;
	socklen_t		client_addr_len;
	BOOL			tls_port;
} smtp_t,pop3_t;

#define GCES(status, server, sock, sess, action) do {                             \
	char *GCES_estr;                                                               \
	int GCES_level;                                                                 \
	get_crypt_error_string(status, sess, &GCES_estr, action, &GCES_level);  \
	if (GCES_estr) {                                                                  \
		lprintf(GCES_level, "%04d %s %s", sock, server, GCES_estr);                     \
		free_crypt_attrstr(GCES_estr);                                                  \
	}                                                                                    \
} while(0)

#define GCESH(status, server, sock, host, sess, action) do {                      \
	char *GCES_estr;                                                               \
	int GCES_level;                                                                 \
	get_crypt_error_string(status, sess, &GCES_estr, action, &GCES_level);  \
	if (GCES_estr) {                                                                  \
		lprintf(GCES_level, "%04d %s [%s] %s", sock, server, host, GCES_estr);         \
		free_crypt_attrstr(GCES_estr);                                                  \
	}                                                                                    \
} while(0)

#define GCESHL(status, server, sock, host, log_level, sess, action) do {                      \
	char *GCES_estr;                                                               \
	int GCES_level;                                                                 \
	get_crypt_error_string(status, sess, &GCES_estr, action, &GCES_level);  \
	if (GCES_estr) {                                                                  \
		lprintf(log_level, "%04d %s [%s] %s", sock, server, host, GCES_estr);         \
		free_crypt_attrstr(GCES_estr);                                                  \
	}                                                                                    \
} while(0)

#if defined(__GNUC__)   // Catch printf-format errors with lprintf
static int lprintf(int level, const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
#endif
static int lprintf(int level, const char *fmt, ...)
{
	va_list argptr;
	char sbuf[1024];

	va_start(argptr,fmt);
    vsnprintf(sbuf,sizeof(sbuf),fmt,argptr);
	sbuf[sizeof(sbuf)-1]=0;
    va_end(argptr);