138 lines
3.2 KiB
PHP
138 lines
3.2 KiB
PHP
<?php
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error_reporting(0);
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function get_spf_allowed_hosts($check_domain)
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{
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$hosts = array();
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$records = dns_get_record($check_domain, DNS_TXT);
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foreach ($records as $record)
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{
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$txt = explode(' ', $record['entries'][0]);
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if (array_shift($txt) != 'v=spf1') // only handle SPF records
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continue;
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foreach ($txt as $mech)
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{
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$qual = substr($mech, 0, 1);
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if ($qual == '-' || $qual == '~') // only handle pass or neutral records
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continue(2);
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if ($qual == '+' || $qual == '?')
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$mech = substr($mech, 1); // remove the qualifier
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if (strpos($mech, '=') !== FALSE) // handle a modifier
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{
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$mod = explode('=', $mech);
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if ($mod[0] == 'redirect') // handle a redirect
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{
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$hosts = get_spf_allowed_hosts($mod[1]);
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return $hosts;
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}
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}
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else
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{
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unset($cidr);
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if (strpos($mech, ':') !== FALSE) // handle a domain specification
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{
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$split = explode(':', $mech);
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$mech = array_shift($split);
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$domain = implode(':', $split);
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if (strpos($domain, '/') !== FALSE) // remove CIDR specification
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{
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$split = explode('/', $domain);
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$domain = $split[0];
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$cidr = $split[1];
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}
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}
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$new_hosts = array();
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if ($mech == 'include' && $check_domain != $domain) // handle an inclusion
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{
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$new_hosts = get_spf_allowed_hosts($domain);
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}
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elseif ($mech == 'a') // handle a mechanism
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{
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$new_hosts = get_a_hosts($domain);
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}
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elseif ($mech == 'mx') // handle mx mechanism
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{
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$new_hosts = get_mx_hosts($domain);
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}
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elseif ($mech == 'ip4' || $mech == 'ip6') // handle ip mechanism
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{
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$new_hosts = array($domain);
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}
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if (isset($cidr)) // add CIDR specification if present
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{
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foreach ($new_hosts as &$host)
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{
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$host .= '/' . $cidr;
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}
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unset($host);
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}
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$hosts = array_unique(array_merge($hosts,$new_hosts), SORT_REGULAR);
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}
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}
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}
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return $hosts;
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}
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function get_mx_hosts($domain)
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{
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$hosts = array();
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try {
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$mx_records = dns_get_record($domain, DNS_MX);
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if ($mx_records) {
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foreach ($mx_records as $mx_record) {
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$new_hosts = get_a_hosts($mx_record['target']);
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$hosts = array_unique(array_merge($hosts,$new_hosts), SORT_REGULAR);
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}
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}
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}
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catch (Exception $e) {
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if ($e->getMessage() !== 'dns_get_record(): A temporary server error occurred.') {
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throw $e;
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}
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$mx_records = false;
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}
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return $hosts;
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}
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function get_a_hosts($domain)
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{
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$hosts = array();
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$a_records = dns_get_record($domain, DNS_A);
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foreach ($a_records as $a_record)
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{
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$hosts[] = $a_record['ip'];
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}
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$a_records = dns_get_record($domain, DNS_AAAA);
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foreach ($a_records as $a_record)
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{
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$hosts[] = $a_record['ipv6'];
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}
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return $hosts;
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}
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function get_outgoing_hosts_best_guess($domain)
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{
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// try the SPF record to get hosts that are allowed to send outgoing mails for this domain
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$hosts = get_spf_allowed_hosts($domain);
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if ($hosts) return $hosts;
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// try the MX record to get mail servers for this domain
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$hosts = get_mx_hosts($domain);
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if ($hosts) return $hosts;
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// fall back to the A record to get the host name for this domain
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return get_a_hosts($domain);
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}
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?>
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