Mail::SpamAssassin::Plugin::URIDNSBL (3)

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NAME

URIDNSBL - look up URLs against DNS blocklists

SYNOPSIS

  loadplugin    Mail::SpamAssassin::Plugin::URIDNSBL
  uridnsbl      URIBL_SBLXBL    sbl-xbl.spamhaus.org.   TXT

DESCRIPTION

This works by analysing message text and for URLs, extracting host names from those, then querying various blocklists for either: addresses of these hosts (uridnsbl,a) or their nameservers (uridnsbl,ns), or domain names of these hosts (urirhsbl), or domain names of their nameservers (urinsrhsbl, urifullnsrhsbl).

USER SETTINGS

skip_uribl_checks ( 0 | 1 ) (default: 0)

Turning on the skip_uribl_checks setting will disable the

URIDNSBL

plugin.

By default, SpamAssassin will run

URI DNSBL

checks. Individual

URI

blocklists may be disabled selectively by setting a score of a corresponding rule to 0 or through the uridnsbl_skip_domain parameter.

See also a related configuration parameter skip_rbl_checks, which controls the DNSEval plugin (documented in the Conf man page).

uridnsbl_skip_domain domain1 domain2 ...

Specify a domain, or a number of domains, which should be skipped for the

URIBL

checks. This is very useful to specify very common domains which are not going to be listed in URIBLs.

clear_uridnsbl_skip_domain [domain1 domain2 ...]

If no argument is given, then clears the entire list of domains declared by uridnsbl_skip_domain configuration directives so far. Any subsequent uridnsbl_skip_domain directives will start creating a new list of skip domains.

When given a list of domains as arguments, only the specified domains are removed from the list of skipped domains.

RULE DEFINITIONS AND PRIVILEGED SETTINGS

uridnsbl

NAME_OF_RULE

dnsbl_zone lookuptype

Specify a lookup. "NAME_OF_RULE" is the name of the rule to be used, "dnsbl_zone" is the zone to look up IPs in, and "lookuptype" is the type of lookup (

TXT

or A). Note that you must also define a body-eval rule calling "check_uridnsbl()" to use this.

This works by collecting domain names from URLs and querying

DNS

blocklists with an

IP

address of host names found in URLs or with

IP

addresses of their name servers, according to tflags as follows.

If the corresponding body rule has a tflag 'a', the

DNS

blocklist will be queried with an

IP

address of a host found in URLs.

If the corresponding body rule has a tflag 'ns',

DNS

will be queried for name servers (

NS

records) of a domain name found in URLs, then these name server names will be resolved to their

IP

addresses, which in turn will be sent to

DNS

blocklist.

Tflags directive may specify either 'a' or 'ns' or both flags. In absence of any of these two flags, a default is a 'ns', which is compatible with pre-3.4 versions of SpamAssassin.

The choice of tflags must correspond to the policy and expected use of each

DNS

blocklist and is normally not a local decision. As an example, a blocklist expecting queries resulting from an 'a' tflag is a ``black_a.txt'' ( www.uribl.com/datasets.shtml ).

Example:

 uridnsbl        URIBL_SBLXBL    sbl-xbl.spamhaus.org.   TXT
 body            URIBL_SBLXBL    eval:check_uridnsbl('URIBL_SBLXBL')
 describe        URIBL_SBLXBL    Contains a URL listed in the SBL/XBL blocklist
 tflags          URIBL_SBLXBL    net ns

uridnssub

NAME_OF_RULE

dnsbl_zone lookuptype subtest

Specify a DNSBL-style domain lookup with a sub-test. "NAME_OF_RULE" is the name of the rule to be used, "dnsbl_zone" is the zone to look up IPs in, and "lookuptype" is the type of lookup (

TXT

or A).

Tflags 'ns' and 'a' on a corresponding body rule are recognized and have the same meaning as in the uridnsbl directive.

"subtest" is a sub-test to run against the returned data. The sub-test may be in one of the following forms: m, n1-n2, or n/m, where n,n1,n2,m can be any of: decimal digits, 0x followed by up to 8 hexadecimal digits, or an IPv4 address in quad-dot form. The 'A' records (IPv4 dotted address) as returned by DNSBLs lookups are converted into a numerical form (r) and checked against the specified sub-test as follows: for a range n1-n2 the following must be true: (r >= n1 && r <= n2); for a n/m form the following must be true: (r & m) == (n & m); for a single value in quad-dot form the following must be true: r == n; for a single decimal or hex form the following must be true:
  ((r & n) != 0) && ((r & 0xff000000) == 0x7f000000), i.e. within 127.0.0.0/8

Some typical examples of a sub-test are: 127.0.1.2, 127.0.1.20-127.0.1.39, 127.0.1.0/255.255.255.0, 0.0.0.16/0.0.0.16, 0x10/0x10, 16, 0x10 .

Note that, as with "uridnsbl", you must also define a body-eval rule calling "check_uridnsbl()" to use this.

Example:

  uridnssub   URIBL_DNSBL_4    dnsbl.example.org.   A    127.0.0.4
  uridnssub   URIBL_DNSBL_8    dnsbl.example.org.   A    8

urirhsbl

NAME_OF_RULE

rhsbl_zone lookuptype

Specify a RHSBL-style domain lookup. "NAME_OF_RULE" is the name of the rule to be used, "rhsbl_zone" is the zone to look up domain names in, and "lookuptype" is the type of lookup (

TXT

or A). Note that you must also define a body-eval rule calling "check_uridnsbl()" to use this.

An

RHSBL

zone is one where the domain name is looked up, as a string; e.g. a

URI

using the domain "foo.com" will cause a lookup of "foo.com.uriblzone.net". Note that hostnames are stripped from the domain used in the

URIBL

lookup, so the domain "foo.bar.com" will look up "bar.com.uriblzone.net", and "foo.bar.co.uk" will look up "bar.co.uk.uriblzone.net".

If an

URI

consists of an

IP

address instead of a hostname, the

IP

address is looked up (using the standard reversed quads method) in each "rhsbl_zone".

Example:

  urirhsbl        URIBL_RHSBL    rhsbl.example.org.   TXT

urirhssub

NAME_OF_RULE

rhsbl_zone lookuptype subtest

Specify a RHSBL-style domain lookup with a sub-test. "NAME_OF_RULE" is the name of the rule to be used, "rhsbl_zone" is the zone to look up domain names in, and "lookuptype" is the type of lookup (

TXT

or A).

"subtest" is a sub-test to run against the returned data. The sub-test may be in one of the following forms: m, n1-n2, or n/m, where n,n1,n2,m can be any of: decimal digits, 0x followed by up to 8 hexadecimal digits, or an IPv4 address in quad-dot form. The 'A' records (IPv4 dotted address) as returned by DNSBLs lookups are converted into a numerical form (r) and checked against the specified sub-test as follows: for a range n1-n2 the following must be true: (r >= n1 && r <= n2); for a n/m form the following must be true: (r & m) == (n & m); for a single value in quad-dot form the following must be true: r == n; for a single decimal or hex form the following must be true:
  ((r & n) != 0) && ((r & 0xff000000) == 0x7f000000), i.e. within 127.0.0.0/8

Some typical examples of a sub-test are: 127.0.1.2, 127.0.1.20-127.0.1.39, 127.2.3.0/255.255.255.0, 0.0.0.16/0.0.0.16, 0x10/0x10, 16, 0x10 .

Note that, as with "urirhsbl", you must also define a body-eval rule calling "check_uridnsbl()" to use this.

Example:

  urirhssub   URIBL_RHSBL_4    rhsbl.example.org.   A    127.0.0.4
  urirhssub   URIBL_RHSBL_8    rhsbl.example.org.   A    8

urinsrhsbl

NAME_OF_RULE

rhsbl_zone lookuptype

Perform a RHSBL-style domain lookup against the contents of the

NS

records for each

URI.

In other words, a

URI

using the domain "foo.com" will cause an

NS

lookup to take place; assuming that domain has an

NS

of "ns0.bar.com", that will cause a lookup of "bar.com.uriblzone.net". Note that hostnames are stripped from both the domain used in the

URI,

and the domain in the lookup.

"NAME_OF_RULE" is the name of the rule to be used, "rhsbl_zone" is the zone to look up domain names in, and "lookuptype" is the type of lookup (

TXT

or A).

Note that, as with "urirhsbl", you must also define a body-eval rule calling "check_uridnsbl()" to use this.

urinsrhssub

NAME_OF_RULE

rhsbl_zone lookuptype subtest

Specify a RHSBL-style domain-NS lookup, as above, with a sub-test. "NAME_OF_RULE" is the name of the rule to be used, "rhsbl_zone" is the zone to look up domain names in, and "lookuptype" is the type of lookup (

TXT

or A). "subtest" is the sub-test to run against the returned data; see <urirhssub>.

Note that, as with "urirhsbl", you must also define a body-eval rule calling "check_uridnsbl()" to use this.

urifullnsrhsbl

NAME_OF_RULE

rhsbl_zone lookuptype

Perform a RHSBL-style domain lookup against the contents of the

NS

records for each

URI.

In other words, a

URI

using the domain "foo.com" will cause an

NS

lookup to take place; assuming that domain has an

NS

of "ns0.bar.com", that will cause a lookup of "ns0.bar.com.uriblzone.net". Note that hostnames are stripped from the domain used in the

URI.

"NAME_OF_RULE" is the name of the rule to be used, "rhsbl_zone" is the zone to look up domain names in, and "lookuptype" is the type of lookup (

TXT

or A).

Note that, as with "urirhsbl", you must also define a body-eval rule calling "check_uridnsbl()" to use this.

urifullnsrhssub

NAME_OF_RULE

rhsbl_zone lookuptype subtest

Specify a RHSBL-style domain-NS lookup, as above, with a sub-test. "NAME_OF_RULE" is the name of the rule to be used, "rhsbl_zone" is the zone to look up domain names in, and "lookuptype" is the type of lookup (

TXT

or A). "subtest" is the sub-test to run against the returned data; see <urirhssub>.

Note that, as with "urirhsbl", you must also define a body-eval rule calling "check_uridnsbl()" to use this.

tflags

NAME_OF_RULE

ips_only

Only URIs containing

IP

addresses as the ``host'' component will be matched against the named ``urirhsbl''/``urirhssub'' rule.

tflags

NAME_OF_RULE

domains_only

Only URIs containing a non-IP-address ``host'' component will be matched against the named ``urirhsbl''/``urirhssub'' rule.

tflags

NAME_OF_RULE

ns

The 'ns' flag may be applied to rules corresponding to uridnsbl and uridnssub directives. Host names from URLs will be mapped to their name server

IP

addresses (a

NS

lookup followed by an A lookup), which in turn will be sent to blocklists. This is a default when neither 'a' nor 'ns' flags are specified.

tflags

NAME_OF_RULE

a

The 'a' flag may be applied to rules corresponding to uridnsbl and uridnssub directives. Host names from URLs will be mapped to their

IP

addresses, which will be sent to blocklists. When both 'ns' and 'a' flags are specified, both queries will be performed.

ADMINISTRATOR SETTINGS

uridnsbl_max_domains N               (default: 20)

The maximum number of domains to look up.

NOTES

The "uridnsbl_timeout" option has been obsoleted by the "rbl_timeout" option. See the "Mail::SpamAssassin::Conf" for details on "rbl_timeout".