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[Mikrotik] RouterOS: il firewall

#1
Information 
Il firewall implementa il filtraggio dei pacchetti e, quindi, fornisce funzioni di sicurezza che vengono utilizzati per gestire il flusso di dati da, verso e attraverso il router. Insieme con il Network Address Translation (NAT) serve come strumento per prevenire l'accesso non autorizzato alle reti direttamente attaccati.
I firewall sono usati come un mezzo per prevenire o ridurre al minimo i rischi per la sicurezza inerenti il collegamento ad altre reti. Il firewall configurato correttamente gioca un ruolo chiave nella distribuzione.
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RouterOS ha un potente firewall con molte funzionalità, fra cui ricordiamo:

stateful packet inspection
Layer-7 protocol detection
peer-to-peer protocols filtering
traffic classification by:
source MAC address
IP addresses (network or list) and address types (broadcast, local, multicast, unicast)
port or port range
IP protocols
protocol options (ICMP type and code fields, TCP flags, IP options and MSS)
interface the packet arrived from or left through
internal flow and connection marks
DSCP byte
packet content
rate at which packets arrive and sequence numbers
packet size
packet arrival time

Chains:

ll firewall funziona per mezzo di regole. Ogni regola consiste di due parti - il matcher e l'azione.

Le regole di filtraggio del firewall sono raggruppati in catene. Tali regole consentono ad un pacchetto di essere confrontato con un criterio comune a una catena successivamente passa nei criteri comuni ad una catena (chains).
Ad esempio: / ip filtro firewall add src-address = 1.1.1.2/32 jump-target = "mychain" nel caso in cui corrisponde a questa regola passa alla chain successiva appartenete alla stessa catena.

Ci sono tre chain predefinite che non possono essere eliminate:

input - utilizzato per elaborare i pacchetti che entrano nel router attraverso una delle interfacce con l'indirizzo IP di destinazione;
forward - usato per i pacchetti che passano attraverso il router;
output - usato per i pacchetti di processo originato dal router.

Durante l'elaborazione di una chain, le regole sono prese analizzate nell'ordine in cui sono elencati (dalla prima all'ultima). Se un pacchetto soddisfa i criteri della regola, quindi l'azione specificata viene eseguita su di esso, i pacchetti non attraversano più altre regole (a meno che non è selezionata la voce passthrough). Se un pacchetto non è abbinato ad alcuna regola all'interno della chain, allora è accettato.

Proprietà:

action (action name; Default: accept) Action to take if packet is matched by the rule:
  • accept - accept the packet. Packet is not passed to next firewall rule.
  • add-dst-to-address-list - add destination address to address list specified by address-list parameter
  • add-src-to-address-list - add source address to address list specified by address-list parameter
  • drop - silently drop the packet
  • jump - jump to the user defined chain specified by the value of jump-target parameter
  • log - add a message to the system log containing following data: in-interface, out-interface, src-mac, protocol, src-ip:port->dst-ip:port and length of the packet. After packet is matched it is passed to next rule in the list, similar as passthrough
  • passthrough - ignore this rule and go to next one (useful for statistics).
  • reject - drop the packet and send an ICMP reject message
  • return - passes control back to the chain from where the jump took place
  • tarpit - captures and holds TCP connections (replies with SYN/ACK to the inbound TCP SYN packet)
address-list (string; Default: ) Name of the address list to be used. Applicable if action is add-dst-to-address-list or add-src-to-address-list
address-list-timeout (time; Default: 00:00:00) Time interval after which the address will be removed from the address list specified by address-list parameter. Used in conjunction with add-dst-to-address-list or add-src-to-address-list actions
Value of 00:00:00 will leave the address in the address list forever
chain (name; Default: ) Specifies to which chain rule will be added. If the input does not match the name of an already defined chain, a new chain will be created.
comment (string; Default: ) Descriptive comment for the rule.
connection-bytes (integer-integer; Default: ) Matches packets only if a given amount of bytes has been transfered through the particular connection. 0 - means infinity, for example connection-bytes=2000000-0 means that the rule matches if more than 2MB has been transfered through the relevant connection
connection-limit (integer,netmask; Default: ) Restrict connection limit per address or address block
connection-mark (no-mark | string; Default: ) Matches packets marked via mangle facility with particular connection mark. If no-mark is set, rule will match any unmarked connection.
connection-rate (Integer 0..4294967295; Default: ) Connection Rate is a firewall matcher that allow to capture traffic based on present speed of the connection.
connection-state (estabilished | invalid | new | related; Default: ) Interprets the connection tracking analysis data for a particular packet:
  • established - a packet which belongs to an existing connection
  • invalid - a packet which could not be identified for some reason
  • new - the packet has started a new connection, or otherwise
    associated with a connection which has not seen packets in both directions.
  • related - a packet which is related to, but not part of an existing connection, such as ICMP errors or a packet which begins FTP data connection
connection-type (ftp | h323 | irc | pptp | quake3 | sip | tftp; Default: ) Matches packets from related connections based on information from their connection tracking helpers. A relevant connection helper must be enabled under /ip firewall service-port
content (string; Default: ) Match packets that contain specified text
dscp (integer: 0..63; Default: ) Matches DSCP IP header field.
dst-address (IP/netmask | IP range; Default: ) Matches packets which destination is equal to specified IP or falls into specified IP range.
dst-address-list (name; Default: ) Matches destination address of a packet against user-defined address list
dst-address-type (unicast | local | broadcast | multicast; Default: ) Matches destination address type:
  • unicast - IP address used for point to point transmission
  • local - if dst-address is assigned to one of router's interfaces
  • broadcast - packet is sent to all devices in subnet
  • multicast - packet is forwarded to defined group of devices
dst-limit (integer,time,integer,dst-address | dst-port | src-address, time; Default: ) Matches packets within given pps limit. As opposed to the limit matcher, every destination IP address / destination port has it's own limit. Parameters are written in following format: count,time,burst,mode,expire.
  • count - maximum average packet rate measured in packets per time interval
  • time - specifies the time interval in which the packet rate is measured
  • burst - number of packets which are not counted by packet rate
  • mode - the classifier for packet rate limiting
  • expire - specifies interval after which recored ip address /port will be deleted
dst-port (integer[-integer]: 0..65535; Default: ) List of destination port numbers or port number ranges
fragment (yes|no; Default: ) Matches fragmented packets. First (starting) fragment does not count. If connection tracking is enabled there will be no fragments as system automatically assembles every packet
hotspot (auth | from-client | http | local-dst | to-client; Default: )
icmp-options (integer:integer; Default: ) Matches ICMP type:code fileds
in-bridge-port (name; Default: ) Actual interface the packet has entered the router, if incoming interface is bridge. Works only if use-ip-firewall is enabled in bridge settings.
in-interface (name; Default: ) Interface the packet has entered the router
ingress-priority (integer: 0..63; Default: ) Matches ingress priority of the packet. Priority may be derived from VLAN, WMM or MPLS EXP bit.
ipv4-options (any | loose-source-routing | no-record-route | no-router-alert | no-source-routing | no-timestamp | none | record-route | router-alert | strict-source-routing | timestamp; Default: ) Matches IPv4 header options.
  • any - match packet with at least one of the ipv4 options
  • loose-source-routing - match packets with loose source routing option. This option is used to route the internet datagram based on information supplied by the source
  • no-record-route - match packets with no record route option. This option is used to route the internet datagram based on information supplied by the source
  • no-router-alert - match packets with no router alter option
  • no-source-routing - match packets with no source routing option
  • no-timestamp - match packets with no timestamp option
  • record-route - match packets with record route option
  • router-alert - match packets with router alter option
  • strict-source-routing - match packets with strict source routing option
  • timestamp - match packets with timestamp
jump-target (name; Default: ) Name of the target chain to jump to. Applicable only if action=jump
layer7-protocol (name; Default: ) Layer7 filter name defined in layer7 protocol menu.
limit (integer,time,integer; Default: ) Matches packets within given pps limit. Parameters are written in following format: count,time,burst.
  • count - maximum average packet rate measured in packets per time interval
  • time - specifies the time interval in which the packet rate is measured
  • burst - number of packets which are not counted by packet rate
log-prefix (string; Default: ) Adds specified text at the beginning of every log message. Applicable if action=log
nth (integer,integer; Default: ) Matches every nth packet.
out-bridge-port (name; Default: ) Actual interface the packet is leaving the router, if outgoing interface is bridge. Works only if use-ip-firewall is enabled in bridge settings.
out-interface (; Default: ) Interface the packet is leaving the router
p2p (all-p2p | bit-torrent | blubster | direct-connect | edonkey | fasttrack | gnutella | soulseek | warez | winmx; Default: ) Matches packets from various peer-to-peer (P2P) protocols. Does not work on encrypted p2p packets.
packet-mark (no-mark | string; Default: ) Matches packets marked via mangle facility with particular packet mark. If no-mark is set, rule will match any unmarked packet.
packet-size (integer[-integer]:0..65535; Default: ) Matches packets of specified size or size range in bytes.
per-connection-classifier (ValuesToHashBig Grinenominator/Remainder; Default: ) PCC matcher allows to divide traffic into equal streams with ability to keep packets with specific set of options in one particular stream.
port (integer[-integer]: 0..65535; Default: ) Matches if any (source or destination) port matches the specified list of ports or port ranges. Applicable only if protocol is TCP or UDP
protocol (name or protocol ID; Default: tcp) Matches particular IP protocol specified by protocol name or number
psd (integer,time,integer,integer; Default: ) Attempts to detect TCP and UDP scans. Parameters are in following format WeightThreshold, DelayThreshold, LopPortWeight, HighPortWeight
  • WeightThreshold - total weight of the latest TCP/UDP packets with different destination ports coming from the same host to be treated as port scan sequence
  • DelayThreshold - delay for the packets with different destination ports coming from the same host to be treated as possible port scan subsequence
  • LowPortWeight - weight of the packets with privileged (<=1024) destination port
  • HighPortWeight - weight of the packet with non-priviliged destination port
random (integer: 1..99; Default: ) Matches packets randomly with given probability.
reject-with (; Default: ) Specifies error to be sent back if packet is rejected. Applicable if action=reject
routing-mark (string; Default: ) Matches packets marked by mangle facility with particular routing mark
src-address (Ip/Netmaks, Ip range; Default: ) Matches packets which source is equal to specified IP or falls into specified IP range.
src-address-list (name; Default: ) Matches source address of a packet against user-defined address list
src-address-type (unicast | local | broadcast | multicast; Default: )

Matches source address type:

  • unicast - IP address used for point to point transmission
  • local - if address is assigned to one of router's interfaces
  • broadcast - packet is sent to all devices in subnet
  • multicast - packet is forwarded to defined group of devices
src-port (integer[-integer]: 0..65535; Default: ) List of source ports and ranges of source ports. Applicable only if protocol is TCP or UDP.
src-mac-address (MAC address; Default: ) Matches source MAC address of the packet
tcp-flags (ack | cwr | ece | fin | psh | rst | syn | urg; Default: ) Matches specified TCP flags
  • ack - acknowledging data
  • cwr - congestion window reduced
  • ece - ECN-echo flag (explicit congestion notification)
  • fin - close connection
  • psh - push function
  • rst - drop connection
  • syn - new connection
  • urg - urgent data
tcp-mss (integer: 0..65535; Default: ) Matches TCP MSS value of an IP packet
time (time-time,sat | fri | thu | wed | tue | mon | sun; Default: ) Allows to create filter based on the packets' arrival time and date or, for locally generated packets, departure time and date
ttl (integer: 0..255; Default: ) Matches packets TTL value

Stats:

/ip firewall filter print stats mostra le statistiche (solo lettura)

bytes (integer) Total amount of bytes matched by the rule
packets (integer) Total amount of packets matched by the rule

By default print is equivalent to print static and shows only static rules.
Di default print mpostrerà solo le regole statiche:

Codice:
[admin@dzeltenais_burkaans] /ip firewall mangle> print stats
Flags: X - disabled, I - invalid, D - dynamic
#   CHAIN              ACTION                  BYTES           PACKETS        
0   prerouting         mark-routing            17478158        127631        
1   prerouting         mark-routing            782505          4506
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