Class: IPAccess::List::Check

Inherits:
IPAccess::List show all
Defined in:
lib/ipaccess/ip_access_check.rb

Overview

This class maintains a simple access list containing rules and methods for checking access.

Rules management

Use instance methods to add or remove rules from the list. Both IPv4 and IPv6 addresses are supported. See IPAccess.cidrs for available formats of addresses.

Checking access

To check an access you may call methods that belong to this list.

There are different variants of this methods for different IP representations. That’s because speed is important here. If you have a socket object you want to test then you should use a method that checks sockets. If your IP is in a text format you may want to use a method that checks IP addresses written as strings.

Exceptions

Access checking methods throw exceptions that are kind of IPAccessDenied or derivative. You may also set the exception class using exception attribute of instances. Each exception contain IP address, rule that matched, diagnostic message and an optional object that points to so called originator described below. See IPAccessDenied to see all attributes present in an exception.

Accessing original object

You can pass an optional object to almost all of the access checking methods. It usually will be passed as the last argument called originator. The originator is intended to be used as a helpful reference to original object for which an access is checked.

You may want to ask why there is a need for originator when some object is tested already. The problem is that not just sockets can raise exceptions. If you want your program to block access before socket is even created (for outgoing traffic) then you may validate IP earlier. There are also some situations when you want to test something that represents network object’s IP but it’s not related to network object itself. For example, imagine that your program creates objects for HTTP sessions. In your HTTP class you may add some access checks but the tested object will be a socket. In that case you may want to pass HTTP object to an access checking method as the originator while performing access check on a socket.

Originator is transported within an exception so you can use it in rescue section to send some data or do other stuff before closing network object. In case of patched network objects and special variants of network classes that this library also provides, you may also find :opened_on_deny option helpful to achieve that.

In case of general purpose method like check you cannot pass the originator because it uses variant list of arguments of different kinds – in that case however the originators will be established using original, checked objects. The only disadvantage is that you cannot set the originators manually.

If the additional argument originator is nil or is not passed to the access checking method, the method will try to obtain it automagically. How? It will try to fetch it from the :Originator tag of NetAddr::CIDR object that had been used. This tag will be preset because the method will add :inclulde_origins option while calling IPAccess.to_cidrs on a list of arguments that are going to be checked. That magic works also for specialized access checking methods. In those cases the originator is not fetched from NetAddr::CIDR object’s tag but comes from a real object (Socket, String, etc.) that had been passed to method for testing.

Access checking methods will try to fill up missing :Originator tag in each processed object containing IP address while figuring out the original object. By object containing IP address we mean NetAddr::CIDR kind of object that is used by underlying routines to check access and reported during exception raising as peer_ip attribute. Checking methods will use private method setup_originator to decide which object should be choosen as the originator.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*addresses) ⇒ Check

Creates new IPAccess::List::Ch object. You may pass objects (containing IP information) to it. These objects will create black list rules. See IPAccess.to_cidrs description for more info on how to pass arguments.

IPAccess::List::Check object and/or NetAddr::CIDR object(s) may carry black or white list assignments inside. If such object(s) will be used to create initial ruleset then assignment found there would be used instead of default.

You should avoid passing hostnames as arguments since DNS is not reliable and responses may change with time,. That may cause security flaws.

Examples

IPAccess::List::Check.new '192.168.0.0/16', '127.0.0.1/255.0.0.0'
IPAccess::List::Check.new :private, :local
IPAccess::List::Check.new "randomseed.pl", :nonpublic



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# File 'lib/ipaccess/ip_access_check.rb', line 163

def initialize(*addresses)
  @exception = IPAccessDenied
  super(*addresses)
end

Instance Attribute Details

#exception ⇒ Object

This attribute contains default exception that this class should throw when an access is denied. It must be a kind of IPAccessDenied or derivative.



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# File 'lib/ipaccess/ip_access_check.rb', line 141

def exception
  @exception
end

Instance Method Details

#check(*addresses) ⇒ Object

This method checks IP access for CIDR objects. If the access is denied it raises an exception reporting first rejected IP. The exception class is taken from a exception attribute of this object – it should be IPAccessDenied or derivative kind of object.

If the access is granted it returns an array containing the given argument(s).

The argument called addresses should be a list of objects containing IP addresses. See the description of IPAccess.to_cidrs for more info about arguments you may pass.

This method will try to set up originators for tested addresses. That’s why it will pass :include_origins option to underlying methods which use IPAccess.to_cidrs to fetch IP addresses from many kinds of objects.

Tracking original network objects

Exception raises when some IP is denied. That IP comes from one, particular object passed as one of the arguments. This object is passed as originator attribute of the exception. That allows you to find the original network object that had been checked, not just its internal representation (peer_ip attribute) that is a kind of NetAddr::CIDR. Be aware that NetAddr::CIDR objects passed as arguments may also have originators set inside (check tag[:Originator]). In that case the originator is simply copied. Also remember that NetAddr::CIDR objects are never set nor reported as originators. In order to track originators the :include_origin option is used when calling IPAccess.to_cidrs.

Passing a block

Optional block may be passed to this method. It will be called once, when the access for a remote IP address turns out to be denied. If it will evaluate to true then no exception is raised, even if the IP is not allowed to connect. Remember to return false or nil in the block to avoid random admissions. The block may take the following arguments:

<br />

  • address of a denied IP (a kind of NetAddr::CIDR)

  • rule that matched (a kind of NetAddr::CIDR)

  • access_list pointing to a used access list (this object)

  • addresses containing an array of arguments (IP addresses)

  • originator indended to be placed as the originator attribute in an exception

<br />

Faster alternatives

This method is relatively easy to use but you may also try more efficient access checking methods if your object contains information about single IP and is a known kind.

See the protected check method description for more info about internals. See IPAccess.to_cidrs description for more info about arguments you may pass to this method.

Workflow

In order to understand this method’s logic properly you may look at the diagram:



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# File 'lib/ipaccess/ip_access_check.rb', line 387

def check(*addresses) # :yields: address, rule, list, addresses, originator
  return addresses if self.empty?
  addresses.push :include_origins
  pairs = self.denied(*addresses)
  unless pairs.empty?
    addr = pairs.first[:IP]
    rule = pairs.first[:Rule]
    originator  = setup_originator(addr, originator)
    dont_scream = false
    dont_scream = yield(addr, rule, self, addresses, originator) if block_given?
    scream!(addr, rule, @exception, originator, nil) unless dont_scream
  end
  return addresses
end

#check_cidr(cidr, originator = nil) ⇒ Object

This method checks access for a CIDR object. It works the same way as check_socket but tests NetAddr::CIDR objects.



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# File 'lib/ipaccess/ip_access_check.rb', line 464

def check_cidr(cidr, originator=nil) # :yields: address, rule, list, cidr, originator
  pair = self.denied_cidr(cidr, true)
  unless pair.empty?
    addr = pair[:IP]
    rule = pair[:Rule]
    originator  = setup_originator(addr, originator)
    dont_scream = false
    dont_scream = yield(addr, rule, self, cidr, originator) if block_given?
    scream!(addr, rule, @exception, originator, nil) unless dont_scream
  end
  return cidr
end

#check_fd(fd, originator = nil, &block) ⇒ Object

This method checks IP access but bases on file descriptor. It works the same way as check_socket but tests file descriptor.



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# File 'lib/ipaccess/ip_access_check.rb', line 499

def check_fd(fd, originator=nil, &block) # :yields: address, rule, access_list, socket, originator
  originator = fd if originator.nil?
  check_socket(::Socket.for_fd(fd), originator, &block)
  return fd
end

#check_ipstring(ipstring, originator = nil) ⇒ Object

This method checks access for a string containing IP address. It works the same way as check_socket but tests Strings containing IP addresses.



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# File 'lib/ipaccess/ip_access_check.rb', line 481

def check_ipstring(ipstring, originator=nil) # :yields: address, rule, list, ipstring, originator
  return ipstring if self.empty?
  addr = NetAddr::CIDR.create(ipstring.split('%').first)
  pair = self.denied_cidr(addr, true)
  unless pair.empty?
    addr = pair[:IP]
    rule = pair[:Rule]
    originator  = setup_originator(addr, originator, ipstring)
    dont_scream = false
    dont_scream = yield(addr, rule, self, ipstring, originator) if block_given?
    scream!(addr, rule, @exception, originator, nil) unless dont_scream
  end
  return ipstring
end

#check_sockaddr(sockaddr, originator = nil) ⇒ Object

This method checks access for a sockaddr. It works the same way as check_socket but tests sockaddr structures.



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# File 'lib/ipaccess/ip_access_check.rb', line 441

def check_sockaddr(sockaddr, originator=nil) # :yields: address, rule, list, sockaddr, orig
  return sockaddr if self.empty?
  begin
    peeraddr = Socket.unpack_sockaddr_in(sockaddr).last
  rescue ArgumentError # sockaddr is not INET
    return sockaddr
  end
  peer_ip = NetAddr::CIDR.create(peeraddr.split('%').first)
  pair    = self.denied_cidr(peer_ip, true)
  unless pair.empty?
    addr = pair[:IP]
    rule = pair[:Rule]
    originator  = setup_originator(addr, originator, sockaddr)
    dont_scream = false
    dont_scream = yield(addr, rule, self, sockaddr, originator) if block_given?
    scream!(addr, rule, @exception, originator, nil) unless dont_scream
  end
  return sockaddr
end

#check_socket(socket, originator = nil) ⇒ Object

This method checks access for a socket.

It works the same way as the check method but expects you to give a single Socket object instead of a list of arguments and an optional originator object to be used as an originator when raising an exception. If the last argument is not given then the originator will be set to tested object. To reset originator pass :none as the last argument. In order to understand this method’s logic properly you may look at the diagram:



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# File 'lib/ipaccess/ip_access_check.rb', line 416

def check_socket(socket, originator=nil) # :yields: address, rule, list, socket, originator
  if (self.empty? || !socket.respond_to?(:getpeername))
    return socket
  end
  begin
    peeraddr = Socket.unpack_sockaddr_in(socket.getpeername).last
  rescue IOError, Errno::ENOTCONN, Errno::ENOTSOCK, ArgumentError # socket is not INET, not a socket nor connected
    return socket
  end
  peer_ip = NetAddr::CIDR.create(peeraddr.split('%').first)
  pair    = self.denied_cidr(peer_ip, true)
  unless pair.empty?
    addr = pair[:IP]
    rule = pair[:Rule]
    originator  = setup_originator(addr, originator, socket)
    dont_scream = false
    dont_scream = yield(addr, rule, self, socket, originator) if block_given?
    scream!(addr, rule, @exception, originator, socket) unless dont_scream
  end
  return socket
end

#delete!(*addresses) ⇒ Object

This method removes CIDR rules specified by the given objects containing IP information. It returns an array of removed CIDR rules.

Make sure you will specify correct and exact netmasks in order to delete proper rules. This method will NOT remove rules that imprecisely match given address or rules that logically depends on specified rules, e.g. removing 192.168.0.0/16 will leave 192.168.0.0/24 untouched. To create access exceptions for some ranges and/or addresses whitelist them using permit method. This method removes rules matching exact addresses/masks.

If the first or last argument is a symbol and it’s :white or :black then the specified rule will be removed only from the given (white or black) list. If the list is not specified the rule will be removed from both lists.

Special case: some CIDR objects may carry information about access list they should belong to. If the last argument of this method does not specify access list and added rule is the kind of special CIDR containing information about assignment to some list then this extra sugar will be used while removing. These special CIDR objects are usualy result of passing IPAccess::List as an argument. To be sure, whichaccess list will be altered always give its name when passing IPAccess::List.

You should avoid passing hostnames as arguments since DNS is not reliable and responses may change with time, which may cause security flaws.

See IPAccess.to_cidrs description for more info about arguments you may pass to it.



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# File 'lib/ipaccess/ip_access_check.rb', line 211

def delete!(*addresses)
  removed = super(*addresses)
  return removed
end

#scream!(addr, rule, use_exception = IPAccessDenied, originator = nil, socket = nil) ⇒ Object

Raises default exception including important informations like remote IP address, rule that IP matched to, used access list and optional object passed as an argument.

First argument (addr) should be a testet IP address in CIDR object and second argument (rule) of the same kind should contain a matching rule. Third argument should be an exception class that will be used to raise an exception. The last originatorargument should be an object that will be stored within the exception’s object as originator. It’s recommended for it to be an object that was used for communication and therefore tested but not a socket. An underlying socket that caused an exception should be given as socket if the object is not direct cause of the exception but the socket is. In case of raw socket objects socket should be the same as originator.

Raises:

  • (use_exception) 


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# File 'lib/ipaccess/ip_access_check.rb', line 305

def scream!(addr, rule, use_exception=IPAccessDenied, originator=nil, socket=nil)
  raise use_exception.new(addr, rule, self, originator, socket)
end

#setup_originator(cidr, orig = nil, net_obj = nil) ⇒ Object (protected)

This method helps with setting up a proper originator for an object that is checked against access set. Originator is the original object that uses a checked IP address. This definition is very general and that’s why there is a need for a method like this, that will try to set it up properly. The cidr argument (containing the IP address) should be a kind of NetAddr::CIDR. It may also contain a special tag inside called :Originator. Any existing information about the originator contained in this object’s tag will never be overwritten. However, it may not be used if second argument, orig is given. This orig argument should be an object to which the IP address from cidr relates to. If it’s not given then the value found in the cidr‘s originator tag is assigned to it. The last argument, net_obj is intended to be “a rescue object” that will be treated as originator if everything else fails. If the orig is set to :none then the original object will always be returned as nil without affecting tag inside cidr.

Workflow

For better understanding how it works you may look at the workflow diagram:

To predict the logic in an easy way you may also find the input/output states table useful:

After calling this method you may find a reference to two original objects. First in a cidr‘s tag and second returned by the method. By converntion you should rely more on returned value since it may carry a real object (e.g. Net::Something) whereas tag may point to an underlying object that had been used to fetch IP from (e.g. TCPSocket).

This method returns the originator or nil.



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# File 'lib/ipaccess/ip_access_check.rb', line 270

def setup_originator(cidr, orig=nil, net_obj=nil)
  if orig.nil?
    if (cidr.respond_to?(:tag) && !cidr.tag[:Originator].nil?)
      orig = cidr.tag[:Originator]
    else
      unless net_obj.nil?
        orig = net_obj
        cidr.tag[:Originator] = orig
      end
    end
  elsif orig == :none
    orig = nil
  elsif (cidr.respond_to?(:tag) && cidr.tag[:Originator].nil?)
    cidr.tag[:Originator] = orig
  end
  
  return orig
end