Block requests by reverse DNS record
Problem this snippet solves: This iRule performs a reverse DNS lookup on the client IP address and blocks any which don't match a specific top level domain. This specific example sends an HTTP respo...
Published Mar 16, 2015
Version 1.0
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John_Beckmann
Employee
EmployeeThe bug ( BZ 340659 ) https://support.f5.com/kb/en-us/solutions/public/12000/300/sol12378.html was resolved in 10.2.2, so I am sharing an updated iRule to do this in 11.x
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when RULE_INIT {
Set debug to 0 for no logging
Set debug to 1 to just log blocks
Set debug to 2 to log blocks and valid requests
set static::debug 1
Ensure this points to your Data Group
set static::domain_blacklist_dg "domain_block_blacklist"
Set IP for your DNS Server
set static::my_dns 192.168.10.1
Set name of VS if using a local Virtual Server
set static::my_dns my_dns_vs
}
when CLIENT_ACCEPTED {
set do_lookup 1
set is_blocked 0
set full_domain ""
set base_domain ""
if { $static::debug > 1 } { log local0. "Connection Accepted from IP_Addr:[IP::remote_addr]" }
}
when HTTP_REQUEST {
if { $static::debug > 1 } {
log local0. "Processing Request from IP_Addr:[IP::remote_addr]"
log local0. "Do Lookup: $do_lookup Is Blocked: $is_blocked"
log local0. "My_DNS: $static::my_dns"
}
if { $do_lookup } {
grab the client base domain reverse lookup of IP Address
set full_domain [RESOLV::lookup @$static::my_dns inet -ptr [IP::remote_addr]]
grab the base domain (top level plus subdomain) from full_domain
set base_domain [join [lrange [split $full_domain .] end-1 end] .]
set do_lookup 0
}
if { $is_blocked } {
if { $static::debug > 0 } {
log local0. "IP_Addr:[IP::remote_addr] Reverse_Lookup:$base_domain blacklisted (Already Blocked)"
log local0. "Full Domain: $full_domain"
}
send a TCP reset
reject
} else {
if { [class match $base_domain contains $static::domain_blacklist_dg] } {
if { $static::debug > 0 } {
log local0. "IP_Addr:[IP::remote_addr] Reverse_Lookup:$base_domain blacklisted (Blocked)"
log local0. "Full Domian: $full_domain"
}
set is_blocked 1
send a TCP reset
reject
} else {
if { $static::debug > 1 } { log local0. "IP_Addr:[IP::remote_addr] Reverse_Lookup:$base_domain $full_domain Accepted" }
}
}
}
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