haraka-plugin-helo.checks
v1.0.0
Published
Haraka plugin checks the HELO string.
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haraka-plugin-helo.checks
This plugin performs a number of checks on the HELO string.
HELO strings are very often forged or dubious in spam and so this can be a highly effective and false-positive free anti-spam measure.
Usage
helo.checks results can be accessed by subsequent plugins:
const h = connection.results.get('helo.checks');
if (h.pass && h.pass.length > 5) {
// nice job, you passed 6+ tests
}
if (h.fail && h.fail.length > 3) {
// yikes, you failed 4+ tests!
}
if (connection.results.has('helo.checks','pass', /^forward_dns/) {
// the HELO hostname is valid
}
Configuration
helo.checks.regexps
List of regular expressions to match against the HELO string. The regular expressions are automatically wrapped in
^
and$
so they always match the entire string.helo.checks.ini
cp node_modules/haraka-plugin-helo.checks/config/helo.checks.ini config/helo.checks.ini
$EDITOR config/helo.checks.ini
INI file which controls enabling of certain checks:
- dns_timeout=30
How many seconds to wait for DNS queries to timeout.
[check]
valid_hostname=true
Checks that the HELO has at least one '.' in it and the organizational name is possible (ie, a host within a Public Suffix).
bare_ip=true
Checks for HELO where the IP is not surrounded by square brackets. This is an RFC violation so should always be enabled.
dynamic=true
Checks to see if all or part the connecting IP address appears within the HELO argument to indicate that the client has a dynamic IP address.
literal_mismatch=1|2|3
Checks to see if the IP literal used matches the connecting IP address. If set to 1, the full IP must match. If set to 2, the /24 must match. If set to 3, the /24 may match, or the IP can be private (RFC 1918).
match_re=true
See above. This is merely an on/off toggle.
big_company=true
See below. This is merely an on/off toggle.
forward_dns=true
Perform a DNS lookup of the HELO hostname and validate that the IP of the remote is included in the IP(s) of the HELO hostname.
This test requires that the valid_hostname check is also enabled.
rdns_match=true
Sees if the HELO hostname (or at least the domain) match the rDNS hostname(s).
host_mismatch=true
If HELO is called multiple times, checks if the hostname differs between EHLO invocations.
proto_mismatch=true
If EHLO was sent and the host later tries to then send HELO or vice-versa.
[reject]
For all of the checks included above, a matching key in the reject section controls whether messages that fail the test are rejected.
Defaults shown:
[reject]
host_mismatch=false
literal_mismatch=false
proto_mismatch=false
rdns_match=false
dynamic=false
bare_ip=false
valid_hostname=false
forward_dns=false
big_company=false
[skip]
private_ip=true
Bypasses checks for clients within RFC1918, Loopback or APIPA IP address ranges.
relaying
Bypass checks for clients who have relaying privileges (whitelisted IP, SMTP-AUTH, etc).
[bigco]
A list of =[,...] to match against. If the HELO matches what's on the left hand side, the reverse-DNS must match one of the entries on the right hand side or the mail is blocked.
Example:
yahoo.com=yahoo.com,yahoo.co.jp
aol.com=aol.com
gmail.com=google.com