zish/uri_delay_throttle-irule.tcl

## uri_delay_throttle-irule.tcl
# Author: Jeremy Melanson <1080872+zish@users.noreply.github.com>

#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
#
# This is an iRule for the F5 Big-IP family of load-balancers. It creates
# a "greylisting" mechanism for individual URIs, by incrementally delaying
# the time it # takes to send the backend's response.
#
# This can be particularly useful for API calls that might contain a higher
# potential for denial-of-service attacks, without restricting non-matching
# requests.
#
# Configuration requires a "String" Data Group to be defined. The name
# of the Data Group should be added ad the value of
# "static::throttle_data_group", declared below.
#
# Each item key is a URI value, with corresponding throttling settings.
# Throttling settings are configured as follows:
#
# "TO:[timeout_seconds],MR:[max_requests],IN:[delay_increment],MS:[delay_multiplier_ms]".
# [timeout_seconds]:       The time in seconds when a recorded connection is removed.
# [max_requests]:          Maxium number of requests before the a 503 error is returned.
# [delay_increment]:       Length of applied delay increases by recorded connection count at this increement.
# [delay_multiplier_ms]:   Milliseconds by which the delay is increased per delay_increment.
# [up-front_delay]:        (OPTIONAL) Up-front delay to apply to all requests matching the given URI.
#
# Examples:
#
#  TO:10,MR:10,IN:3,MS:200 -
#     Delay (in milliseconds) will be Integer ([num_connections] / 3) * 200 .
#     Over a 10 second period:
#        0-2 connections will result in no delay.
#        3-5 connections will result in 200ms delay.
#        6-8 connections will result in 400ms delay.
#        9 connections will result in 600ms delay.
#        10 connections or more will cause subsequent connections to receive the 503 error.
#
#  TO:20,MR:30,IN:5,MS:100,UF:500 -
#     Delay (in milliseconds) will be Integer ([num_connections] / 2) * 100 .
#     Over a 20 second period:
#        0-4 connections will result in no delay.
#        5-9 connections will result in 100ms delay.
#        10-14 connections will result in 200ms delay.
#        15-19 connections will result in 300ms delay.
#        20-24 connections will result in 400ms delay.
#        25-29 connections will result in 500ms delay.
#        30 connections or more will cause subsequent connections to receive the 503 error.
#
#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-


#--- This makes us log at a maximum interval of 1 entry every 2 seconds,
# unless the status is different than the one previously recorded.
#
proc log_status { client_table status log_msg } {

   #-- Set an entry corresponding to "connlimit:[HTTP::uri]:[IP::client_addr]" in the "udt:lt" subtable.
   # Timeout after 2 seconds. This ensures that we log no more than once every 2 seconds (unless state changes).
   #
   if { $status != [table lookup -subtable "udt:lt" $client_table] } {
      table set -subtable "udt:lt" $client_table $status 2
      log local0. $log_msg
   }
}


#--- Some persistent settings for the iRule can be configured here..
#
when RULE_INIT {

   #-- Set an HTML response to sent to clients who make a request while the VIP is over the max connection count
   set static::block_response_content "<html>Maximum requests exceeded</html>\n"
   set static::block_response_code    503
   set static::throttle_data_group    "b2b_delay_throttle"
}


when HTTP_REQUEST {

   set uri_dg $static::throttle_data_group

   #-- List of throttled URIs can be found in the "uri_delay_throttle" Data Group.
   if { [matchclass [HTTP::uri] starts_with $uri_dg] } {

      set up_front_delay 0

      #- Pull the value from the Data Group. Format is "TO:[timeout_seconds],MR:[max_requests],IN:[delay_increment],MS:[delay_multiplier_ms]".
      scan [class match -value [HTTP::uri] starts_with $uri_dg] TO:%d,MR:%d,IN:%d,MS:%d,UF:%d timeout max_requests t_increment multiplier up_front_delay

      #- Individual tables are maintained for each URI/Client IP match.
      set client_table "connlimit:[HTTP::uri]:[IP::client_addr]"
      set client_port "[TCP::client_port]"

      set conn_count [table keys -subtable $client_table -count]

      #- Incrementally increase the amout of response delay.
      set delay [expr {($conn_count / $t_increment) * $multiplier}]

      set log_msg "Turi=[HTTP::uri] Tcip=[IP::client_addr] Tdlyms=$delay Tmaxdly=[expr {($max_requests / $t_increment) * $multiplier}] Tincr=$t_increment "

      #- Apply up-front-delay, if the URI's settings include it.
      if { $up_front_delay != 0 } {
         set log_msg "$log_msg Tufdly=$up_front_delay "
         after $up_front_delay
      }

      #- If we've hit the max request limit, don't add another entry to the table.
      # Return a notification, if the maximum connection limit was exceeded. Don't bother the back-end.
      # Rule /Common/uri_delay_throttle <HTTP_REQUEST>: turi=/jeremy tcip=10.10.60.211 Tdlyms=500 tcurconn=XXX tmaxdly=3000 tIncr=3 act=[throttle|drop]
      #
      if { $conn_count >= $max_requests } {
         call log_status $client_table "$delay:drop" "$log_msg Tact=drop"

         #- We still delay on denials.
         after $delay
         HTTP::respond $static::block_response_code content $static::block_response_content

      } else {

         #- Add port connection to "connlimit:[HTTP::uri]:[IP::client_addr]"
         table set -subtable $client_table $client_port 1 $timeout

         #- This is just for debugging the iRule, hence being commented out.
         #set debug_response "Tablename: $client_table\n"
         #set debug_response "$debug_response ConnCount: $conn_count\n"
         #set debug_response "$debug_response Upfront Delay: $up_front_delay\n"
         #set debug_response "$debug_response Timeout: $timeout\n"
         #set debug_response "$debug_response Max Req: $max_requests\n"
         #set debug_response "$debug_response Incr: $t_increment\n"
         #set debug_response "$debug_response Mult: $multiplier\n"
         #set debug_response "$debug_response Delay: $delay\n"
         #set debug_response "$debug_response LogMsg: $log_msg\n\n"
         #HTTP::respond 200 content $debug_response

         #- Log and delay, but only of the delay value is nonzero.
         if { $delay > 0 } {
            call log_status $client_table "$delay:throttle" "$log_msg Tact=throttle"

            #- Delay for calculated interval before servimg the page.
            after $delay
         }

      }
   }
}
	# Author: Jeremy Melanson <1080872+zish@users.noreply.github.com>

	#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
	#
	# This is an iRule for the F5 Big-IP family of load-balancers. It creates
	# a "greylisting" mechanism for individual URIs, by incrementally delaying
	# the time it # takes to send the backend's response.
	#
	# This can be particularly useful for API calls that might contain a higher
	# potential for denial-of-service attacks, without restricting non-matching
	# requests.
	#
	# Configuration requires a "String" Data Group to be defined. The name
	# of the Data Group should be added ad the value of
	# "static::throttle_data_group", declared below.
	#
	# Each item key is a URI value, with corresponding throttling settings.
	# Throttling settings are configured as follows:
	#
	# "TO:[timeout_seconds],MR:[max_requests],IN:[delay_increment],MS:[delay_multiplier_ms]".
	# [timeout_seconds]: The time in seconds when a recorded connection is removed.
	# [max_requests]: Maxium number of requests before the a 503 error is returned.
	# [delay_increment]: Length of applied delay increases by recorded connection count at this increement.
	# [delay_multiplier_ms]: Milliseconds by which the delay is increased per delay_increment.
	# [up-front_delay]: (OPTIONAL) Up-front delay to apply to all requests matching the given URI.
	#
	# Examples:
	#
	# TO:10,MR:10,IN:3,MS:200 -
	# Delay (in milliseconds) will be Integer ([num_connections] / 3) * 200 .
	# Over a 10 second period:
	# 0-2 connections will result in no delay.
	# 3-5 connections will result in 200ms delay.
	# 6-8 connections will result in 400ms delay.
	# 9 connections will result in 600ms delay.
	# 10 connections or more will cause subsequent connections to receive the 503 error.
	#
	# TO:20,MR:30,IN:5,MS:100,UF:500 -
	# Delay (in milliseconds) will be Integer ([num_connections] / 2) * 100 .
	# Over a 20 second period:
	# 0-4 connections will result in no delay.
	# 5-9 connections will result in 100ms delay.
	# 10-14 connections will result in 200ms delay.
	# 15-19 connections will result in 300ms delay.
	# 20-24 connections will result in 400ms delay.
	# 25-29 connections will result in 500ms delay.
	# 30 connections or more will cause subsequent connections to receive the 503 error.
	#
	#-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-


	#--- This makes us log at a maximum interval of 1 entry every 2 seconds,
	# unless the status is different than the one previously recorded.
	#
	proc log_status { client_table status log_msg } {

	#-- Set an entry corresponding to "connlimit:[HTTP::uri]:[IP::client_addr]" in the "udt:lt" subtable.
	# Timeout after 2 seconds. This ensures that we log no more than once every 2 seconds (unless state changes).
	#
	if { $status != [table lookup -subtable "udt:lt" $client_table] } {
	table set -subtable "udt:lt" $client_table $status 2
	log local0. $log_msg
	}
	}


	#--- Some persistent settings for the iRule can be configured here..
	#
	when RULE_INIT {

	#-- Set an HTML response to sent to clients who make a request while the VIP is over the max connection count
	set static::block_response_content "<html>Maximum requests exceeded</html>\n"
	set static::block_response_code 503
	set static::throttle_data_group "b2b_delay_throttle"
	}


	when HTTP_REQUEST {

	set uri_dg $static::throttle_data_group

	#-- List of throttled URIs can be found in the "uri_delay_throttle" Data Group.
	if { [matchclass [HTTP::uri] starts_with $uri_dg] } {

	set up_front_delay 0

	#- Pull the value from the Data Group. Format is "TO:[timeout_seconds],MR:[max_requests],IN:[delay_increment],MS:[delay_multiplier_ms]".
	scan [class match -value [HTTP::uri] starts_with $uri_dg] TO:%d,MR:%d,IN:%d,MS:%d,UF:%d timeout max_requests t_increment multiplier up_front_delay

	#- Individual tables are maintained for each URI/Client IP match.
	set client_table "connlimit:[HTTP::uri]:[IP::client_addr]"
	set client_port "[TCP::client_port]"

	set conn_count [table keys -subtable $client_table -count]

	#- Incrementally increase the amout of response delay.
	set delay [expr {($conn_count / $t_increment) * $multiplier}]

	set log_msg "Turi=[HTTP::uri] Tcip=[IP::client_addr] Tdlyms=$delay Tmaxdly=[expr {($max_requests / $t_increment) * $multiplier}] Tincr=$t_increment "

	#- Apply up-front-delay, if the URI's settings include it.
	if { $up_front_delay != 0 } {
	set log_msg "$log_msg Tufdly=$up_front_delay "
	after $up_front_delay
	}

	#- If we've hit the max request limit, don't add another entry to the table.
	# Return a notification, if the maximum connection limit was exceeded. Don't bother the back-end.
	# Rule /Common/uri_delay_throttle <HTTP_REQUEST>: turi=/jeremy tcip=10.10.60.211 Tdlyms=500 tcurconn=XXX tmaxdly=3000 tIncr=3 act=[throttle\|drop]
	#
	if { $conn_count >= $max_requests } {
	call log_status $client_table "$delay:drop" "$log_msg Tact=drop"

	#- We still delay on denials.
	after $delay
	HTTP::respond $static::block_response_code content $static::block_response_content

	} else {

	#- Add port connection to "connlimit:[HTTP::uri]:[IP::client_addr]"
	table set -subtable $client_table $client_port 1 $timeout

	#- This is just for debugging the iRule, hence being commented out.
	#set debug_response "Tablename: $client_table\n"
	#set debug_response "$debug_response ConnCount: $conn_count\n"
	#set debug_response "$debug_response Upfront Delay: $up_front_delay\n"
	#set debug_response "$debug_response Timeout: $timeout\n"
	#set debug_response "$debug_response Max Req: $max_requests\n"
	#set debug_response "$debug_response Incr: $t_increment\n"
	#set debug_response "$debug_response Mult: $multiplier\n"
	#set debug_response "$debug_response Delay: $delay\n"
	#set debug_response "$debug_response LogMsg: $log_msg\n\n"
	#HTTP::respond 200 content $debug_response

	#- Log and delay, but only of the delay value is nonzero.
	if { $delay > 0 } {
	call log_status $client_table "$delay:throttle" "$log_msg Tact=throttle"

	#- Delay for calculated interval before servimg the page.
	after $delay
	}

	}
	}
	}