CiscoAclIntp

CiscoAclIntp is a interpreter of Cisco IOS access control list (ACL).

CiscoAclIntp can...

• parse ACL types of below
  • Numbered ACL (standard/extended)
  • Named ACL (standard/extended)
• parse almost ACL syntax.
  • basic IPv4 acl (protocol ip/tcp/udp)

CiscoAclIntp CANNOT...

• handle IPv4 tcp-flags-qualifier, object-groups, and other specific qualifiers (dscp, ttl, tos, ...). These features are not implemented yet.
• handle IPv6 ACL (ip access-list ipv6) (not implemented yet)

Supports

• Ruby/2.0.0 or later. (Development and testing is being conducted in Ruby/2.0.0 and 2.1.1. It does NOT support Ruby/1.8.x and 1.9.x)
• Racc/1.4.9 or later.

Add this line to your application's Gemfile:

gem 'cisco_acl_intp'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cisco_acl_intp

One of application using CiscoAclIntp is in tools/check_acl.rb. The script works as ACL validator. It reads a ACL file, parse it with CiscoAclIntp parser and output parser results.

In directory acl_examples, there are some Cisco IOS ACL sample files. Run check_acl.rb with ACL sample files, like below.

$ ruby tools/check_acl.rb -c term -f acl_examples/err-acl.txt
--------------------
in acl: 100, line: 6, near value: udp, (token: "udp")
in acl: 100, line: 8, near value: 100, (token: NUMBER)
in acl: 100, line: 11, Wrong protocol number: 256
in acl: 100, line: 14, near value: hoge, (token: error)
in acl: FA8-OUT, line: 4, Wrong protocol number: 65536
in acl: FA8-OUT, line: 7, Provided wildcard mask failed validation: 0.0.240.256 is invalid (IPv4 octets should be between 0 and 255).
in acl: FA8-OUT, line: 13, near value: up, (token: error)
--------------------
acl name : 1
access-list 1 permit 192.168.0.0 0.0.255.255
access-list 1 deny any log
acl name : 100
access-list 100 remark General Internet Access
access-list 100 permit icmp any any
access-list 100 permit ip 192.168.0.0 0.0.255.255 any
access-list 100 permit tcp any host 210.197.74.200
access-list 100 remark !wrong acl number!
access-list 100 remark !------cleared------!
access-list 100 remark !wrong header! caccess-list
access-list 100 remark !------cleared------!
access-list 100 permit 41 any host 192.88.99.1
access-list 100 remark !wrong ip proto number!
access-list 100 !! error !! 192.88.99.1
access-list 100 remark !------cleared------!
access-list 100 remark !wrong ip proto!
access-list 100 !! error !! 192.88.99.1
access-list 100 remark !------cleared------!
access-list 100 permit ip any host 192.88.99.1
access-list 100 remark others
access-list 100 permit tcp any eq 0 any eq 0
access-list 100 permit udp any eq 0 any eq 0
access-list 100 deny ip any any log
acl name : 10
access-list 10 !! error !! ntp
acl name : 110
access-list 110 remark SPLIT_VPN
access-list 110 permit ip 192.168.0.0 0.0.255.255 any
acl name : FA8-OUT
ip access-list extended FA8-OUT
 deny udp any any eq bootpc
 deny udp any any eq bootps
 remark !argment error! 65536
 !! error !! 65536
 remark !------cleared------!
 remark !argment error! 255 => 256
 !! error !! 80
 remark !------cleared------!
 remark network access-list remark!!
 permit tcp any any established
 deny tcp any any syn rst
 remark !syntax error! tcp -> tp (typo)
 !! error !! hoge
 remark !------cleared------!
 permit ip any any log
acl name : remote-ipv4
ip access-list standard remote-ipv4
 permit 192.168.0.0 0.0.255.255
 remark standard access-list last deny!?
 deny any log
$

By putting -c (--color) option, check_acl.rb outputs color-coded ACL according to type of each word. It can parse multiple ACLs at the same time. In addition, in the case of the parsing of a ACL that contains errors, CiscoAclIntp parser outputs corresponding error messages. Please try to run using sample ACL file, acl_examples/err-acl.txt, that contains some kind of errors.

You can get short usage with -h option. If it runs without -f (--file) option, it reads ACLs from standard input.

require 'optparse'
require 'cisco_acl_intp'

## CUT: option handling

parser = CiscoAclIntp::Parser.new(popts)

# read acl from file or STDIN
if opts[:file]
  parser.parse_file opts[:file]
else
  parser.parse_file $stdin
end

# print acl data
aclt = parser.acl_table
aclt.each do |name, acl|
  puts "acl name : #{name}"
  puts acl.to_s
end

In the script, generate CiscoAclIntp::Parser instance and it reads ACLs from a file (or $stdin). The parser instance generate ACL objects (as Hash table of ACL name and ACL objects). An element of the table is "ACL object". "ACL object" is build by ACL components. For example, source/destination address obj, action obj, tcp/udp protocol obj,... See more detail in documents (see also, Documents section)

Web front-end of ACL Varidator is at my github repository. It not only can parse (with CLI tool, it can only parse), but also search for ACL(ACE).

A CIDR-IP-Subnet, IP address with wildcard mask, TCP/UDP port numbere(s) with operator (any, eq, neq, lt, gt, range), these are set of IPs and/or ports. In CiscoAclIntp, contains? methods are implemented some ACL/ACE class. It is a set operation method of IP address and TCP/UDP port (to check set inclusion relation).

Example:

src = AceSrcDstSpec.new(
  ipaddr: '192.168.15.15', wildcard: '0.0.7.6',
  operator: 'gt', port: AceTcpProtoSpec.new(32_767)
)
dst = AceSrcDstSpec.new(
  ipaddr: '192.168.30.3', wildcard: '0.0.0.0',
  operator: 'range',
  begin_port: AceTcpProtoSpec.new(1_024),
  end_port: AceTcpProtoSpec.new(65_535)
)

# permit tcp 192.168.15.15 0.0.7.6 gt 32767 host 192.168.30.3 range 1024 65535
ace = ExtendedAce.new(
  action: 'permit', protocol: 'tcp', src: src, dst: dst
)

ace.contains?(
  protocol: 'tcp',
  src_operator: :eq, src_ip: '192.168.9.11', src_port: 51234
)
#=> true

See NetAddr::CIDR#matches? for CIDR subnet operation and NetAddr::CIDR#contains? for IP with wildcard mask.

In below table, "P" column is the argument of #contains?, and operators at table header are receiver of #contains?. The table shows case patterns with port_X.contains?(port_P). (port_X is a instance of AceUnaryOpBase and it has port match operator and port number information.)

For example,[gt X].contains?([eq P]) will be true if port X < P. It means the ACL [gt X] permit (or deny) the flow [eq P]. You can search ACEs which matches a flows specified by search conditions.

:strict_any is a special operator to search acl, the operator is matches only :any operator.

• API document generated with YARD

It can generate documents with YARD.

$ rake yard

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request