| Mail::SpamAssassin::Plugin::URIDNSBL(3pm) | User Contributed Perl Documentation | Mail::SpamAssassin::Plugin::URIDNSBL(3pm) |
URIDNSBL - look up URLs against DNS blocklists
loadplugin Mail::SpamAssassin::Plugin::URIDNSBL uridnsbl URIBL_SBLXBL sbl-xbl.spamhaus.org. TXT
This works by analysing message text and HTML for URLs, extracting host names from those, then querying various DNS blocklists for either: IP 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).
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).
In addition to trimmed domain, the full hostname is also checked from the list.
When given a list of domains as arguments, only the specified domains are removed from the list of skipped domains.
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" ( http://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
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
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 trimmed to the domain portion 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". Using tflag "notrim" will force full hostname lookup, but the specific uribl must support this method.
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
"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. Hostname to domain trimming is also done similarly.
Example:
urirhssub URIBL_RHSBL_4 rhsbl.example.org. A 127.0.0.4
urirhssub URIBL_RHSBL_8 rhsbl.example.org. A 8
"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.
Note that, as with "urirhsbl", you must also define a body-eval rule calling check_uridnsbl() to use this.
"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.
Note that, as with "urirhsbl", you must also define a body-eval rule calling check_uridnsbl() to use this.
The "uridnsbl_timeout" option has been obsoleted by the "rbl_timeout" option. See the "Mail::SpamAssassin::Conf" POD for details on "rbl_timeout".
| 2024-04-12 | perl v5.38.2 |