antispam.c File Reference

several helper functions for spam filters More...

#include <qsmtpd/antispam.h>
#include <control.h>
#include <fmt.h>
#include <libowfatconn.h>
#include <log.h>
#include <match.h>
#include <mmap.h>
#include <netio.h>
#include <qsmtpd/qsmtpd.h>
#include <tls.h>
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <openssl/ssl.h>
#include <poll.h>
#include <string.h>
#include <sys/file.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <syslog.h>
#include <unistd.h>

Typedefs
typedef int(*	ip_matchnet) (const struct in6_addr *ip, const void *ipbuf, const unsigned char netmask)

Functions
static void	nibbletohex (char *dest, const char n)
void	dotip6 (char *buffer)
static int	reverseip4 (char *buf)
int	check_rbl (char *const *rbls, char **txt)
void	tarpit (void)
static int	check_ipbl_file (const size_t iplen, const off_t flen, const unsigned char *buf, ip_matchnet matchfunc)
static int	check_ip4 (const unsigned char *buf, const off_t len)
static int	check_ip6 (const unsigned char *buf, const unsigned int len)
int	domainmatch (const char *fqdn, const size_t len, const char **list)
int	lookupipbl (int fd)

Variables
static unsigned int	tarpitcount = 0

Detailed Description

several helper functions for spam filters

Function Documentation

static int check_ip4 ( const unsigned char *  buf, const off_t  len  )

static

check an IPv4 mapped IPv6 address against a local blocklist

Parameters

buf	buffer of local blocklist, each entry is 5 bytes long
len	length of the buffer

Returns

• 1 if match
• 0 if no match
• -1 if data malformed

IP entries in the buffer must be network byte order

static int check_ip6 ( const unsigned char *  buf, const unsigned int  len  )

static

check an IPv6 address against a local blocklist

Parameters

buf	buffer of local blocklist, each entry is 9 bytes long
len	length of the buffer

Returns

1 if match, 0 if not, -1 if data malformed

int check_rbl	(	char *const *	rbls,
		char **	txt
	)

do a rbl lookup for remoteip

Parameters

rbls	a NULL terminated array of rbls
txt	pointer to "char *" where the TXT record of the listing will be stored if existent

Returns

index of first match

Return values

-1	if not listed or error (if not listed errno is set to 0)

If no match was found but temporary DNS errors were encountered errno is set to EAGAIN.

If txt is NULL no TXT record lookup will be performed.

int domainmatch	(	const char *	fqdn,
		const size_t	len,
		const char **	list
	)

check if a given host name matches against domain list

Parameters

fqdn	hostname to check
len	length of fqdn
list	list of domains and hosts to check against, NULL terminated

Returns

1 on match, 0 otherwise

-if list is NULL terminated and every list[x] and fqdn are 0-terminated there can't be any errors

void dotip6

(

char *

buffer

)

print IPv6 address of remote host in dotted form in buffer

Parameters

buffer

buffer to store result

int lookupipbl

(

int

fd

)

check if the remote host is listed in local IP map file given by fd

Parameters

fd	file descriptor to file

Return values

<0	on error
>0	on match
0	no match

fd will always be closed.

static void nibbletohex ( char *  dest, const char  n  )

inlinestatic

take a nibble and output it as hex to a buffer, followed by '.'

Parameters

dest	pointer where the output should go to
n	the input value. Must really be a nibble, anything else makes strange output

static int reverseip4 ( char *  buf )

static

print client IPv4 address in reverse order into a given buffer

Parameters

buf	buffer to write in (must have at least INET_ADDRSTRLEN (16) bytes)

Returns

length of string in buffer

void tarpit

(

void

)

delay the next reply to the client

This should be used in all places where the client seems to be a spammer. This will delay him so he can't send so much spams.

tarpit does not sleep if there is input pending. If the client is using pipelining or (more likely) a worm or spambot ignoring our replies we kick him earlier and save some traffic.