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[mediawiki.git] / includes / libs / IPSet.php

<?php
/**
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @author Brandon Black <blblack@gmail.com>
 */

/**
 * Matches IP addresses against a set of CIDR specifications
 *
 * Usage:
 *   // At startup, calculate the optimized data structure for the set:
 *   $ipset = new IPSet( $wgSquidServersNoPurge );
 *   // runtime check against cached set (returns bool):
 *   $allowme = $ipset->match( $ip );
 *
 * In rough benchmarking, this takes about 80% more time than
 * in_array() checks on a short (a couple hundred at most) array
 * of addresses.  It's fast either way at those levels, though,
 * and IPSet would scale better than in_array if the array were
 * much larger.
 *
 * For mixed-family CIDR sets, however, this code gives well over
 * 100x speedup vs iterating IP::isInRange() over an array
 * of CIDR specs.
 *
 * The basic implementation is two separate binary trees
 * (IPv4 and IPv6) as nested php arrays with keys named 0 and 1.
 * The values false and true are terminal match-fail and match-success,
 * otherwise the value is a deeper node in the tree.
 *
 * A simple depth-compression scheme is also implemented: whole-byte
 * tree compression at whole-byte boundaries only, where no branching
 * occurs during that whole byte of depth.  A compressed node has
 * keys 'comp' (the byte to compare) and 'next' (the next node to
 * recurse into if 'comp' matched successfully).
 *
 * For example, given these inputs:
 * 25.0.0.0/9
 * 25.192.0.0/10
 *
 * The v4 tree would look like:
 * root4 => array(
 *     'comp' => 25,
 *     'next' => array(
 *         0 => true,
 *         1 => array(
 *             0 => false,
 *             1 => true,
 *         ),
 *     ),
 * );
 *
 * (multi-byte compression nodes were attempted as well, but were
 * a net loss in my test scenarios due to additional match complexity)
 *
 * @since 1.24
 */
class IPSet {
        /** @var array $root4: the root of the IPv4 matching tree */
        private $root4 = array( false, false );

        /** @var array $root6: the root of the IPv6 matching tree */
        private $root6 = array( false, false );

        /**
         * __construct() instantiate the object from an array of CIDR specs
         *
         * @param array $cfg array of IPv[46] CIDR specs as strings
         * @return IPSet new IPSet object
         *
         * Invalid input network/mask values in $cfg will result in issuing
         * E_WARNING and/or E_USER_WARNING and the bad values being ignored.
         */
        public function __construct( array $cfg ) {
                foreach ( $cfg as $cidr ) {
                        $this->addCidr( $cidr );
                }

                self::recOptimize( $this->root4 );
                self::recCompress( $this->root4, 0, 24 );
                self::recOptimize( $this->root6 );
                self::recCompress( $this->root6, 0, 120 );
        }

        /**
         * Add a single CIDR spec to the internal matching trees
         *
         * @param string $cidr string CIDR spec, IPv[46], optional /mask (def all-1's)
         */
        private function addCidr( $cidr ) {
                // v4 or v6 check
                if ( strpos( $cidr, ':' ) === false ) {
                        $node =& $this->root4;
                        $defMask = '32';
                } else {
                        $node =& $this->root6;
                        $defMask = '128';
                }

                // Default to all-1's mask if no netmask in the input
                if ( strpos( $cidr, '/' ) === false ) {
                        $net = $cidr;
                        $mask = $defMask;
                } else {
                        list( $net, $mask ) = explode( '/', $cidr, 2 );
                        if ( !ctype_digit( $mask ) || intval( $mask ) > $defMask ) {
                                trigger_error( "IPSet: Bad mask '$mask' from '$cidr', ignored", E_USER_WARNING );
                                return;
                        }
                }
                $mask = intval( $mask ); // explicit integer convert, checked above

                // convert $net to an array of integer bytes, length 4 or 16:
                $raw = inet_pton( $net );
                if ( $raw === false ) {
                        return; // inet_pton() sends an E_WARNING for us
                }
                $rawOrd = array_map( 'ord', str_split( $raw ) );

                // special-case: zero mask overwrites the whole tree with a pair of terminal successes
                if ( $mask == 0 ) {
                        $node = array( true, true );
                        return;
                }

                // iterate the bits of the address while walking the tree structure for inserts
                $curBit = 0;
                while ( 1 ) {
                        $maskShift = 7 - ( $curBit & 7 );
                        $node =& $node[( $rawOrd[$curBit >> 3] & ( 1 << $maskShift ) ) >> $maskShift];
                        ++$curBit;
                        if ( $node === true ) {
                                // already added a larger supernet, no need to go deeper
                                return;
                        } elseif ( $curBit == $mask ) {
                                // this may wipe out deeper subnets from earlier
                                $node = true;
                                return;
                        } elseif ( $node === false ) {
                                // create new subarray to go deeper
                                $node = array( false, false );
                        }
                }
        }

        /**
         * Match an IP address against the set
         *
         * @param string $ip string IPv[46] address
         * @return bool true is match success, false is match failure
         *
         * If $ip is unparseable, inet_pton may issue an E_WARNING to that effect
         */
        public function match( $ip ) {
                $raw = inet_pton( $ip );
                if ( $raw === false ) {
                        return false; // inet_pton() sends an E_WARNING for us
                }

                $rawOrd = array_map( 'ord', str_split( $raw ) );
                if ( count( $rawOrd ) == 4 ) {
                        $node =& $this->root4;
                } else {
                        $node =& $this->root6;
                }

                $curBit = 0;
                while ( 1 ) {
                        if ( isset( $node['comp'] ) ) {
                                // compressed node, matches 1 whole byte on a byte boundary
                                if ( $rawOrd[$curBit >> 3] != $node['comp'] ) {
                                        return false;
                                }
                                $curBit += 8;
                                $node =& $node['next'];
                        } else {
                                // uncompressed node, walk in the correct direction for the current bit-value
                                $maskShift = 7 - ( $curBit & 7 );
                                $node =& $node[( $rawOrd[$curBit >> 3] & ( 1 << $maskShift ) ) >> $maskShift];
                                ++$curBit;
                        }

                        if ( $node === true || $node === false ) {
                                return $node;
                        }
                }
        }

        /**
         * Recursively merges adjacent nets into larger supernets
         *
         * @param array &$node Tree node to optimize, by-reference
         *
         *  e.g.: 8.0.0.0/8 + 9.0.0.0/8 -> 8.0.0.0/7
         */
        private static function recOptimize( &$node ) {
                if ( $node[0] !== false && $node[0] !== true && self::recOptimize( $node[0] ) ) {
                        $node[0] = true;
                }
                if ( $node[1] !== false && $node[1] !== true && self::recOptimize( $node[1] ) ) {
                        $node[1] = true;
                }
                if ( $node[0] === true && $node[1] === true ) {
                        return true;
                }
                return false;
        }

        /**
         * Recursively compresses a tree
         *
         * @param array &$node Tree node to compress, by-reference
         * @param integer $curBit current depth in the tree
         * @param integer $maxCompStart maximum depth at which compression can start, family-specific
         *
         * This is a very simplistic compression scheme: if we go through a whole
         * byte of address starting at a byte boundary with no real branching
         * other than immediate false-vs-(node|true), compress that subtree down to a single
         * byte-matching node.
         * The $maxCompStart check elides recursing the final 7 levels of depth (family-dependent)
         */
        private static function recCompress( &$node, $curBit, $maxCompStart ) {
                if ( !( $curBit & 7 ) ) { // byte boundary, check for depth-8 single path(s)
                        $byte = 0;
                        $cnode =& $node;
                        $i = 8;
                        while ( $i-- ) {
                                if ( $cnode[0] === false ) {
                                        $byte |= 1 << $i;
                                        $cnode =& $cnode[1];
                                } elseif ( $cnode[1] === false ) {
                                        $cnode =& $cnode[0];
                                } else {
                                        // partial-byte branching, give up
                                        break;
                                }
                        }
                        if ( $i == -1 ) { // means we did not exit the while() via break
                                $node = array(
                                        'comp' => $byte,
                                        'next' => &$cnode,
                                );
                                $curBit += 8;
                                if ( $cnode !== true ) {
                                        self::recCompress( $cnode, $curBit, $maxCompStart );
                                }
                                return;
                        }
                }

                ++$curBit;
                if ( $curBit <= $maxCompStart ) {
                        if ( $node[0] !== false && $node[0] !== true ) {
                                self::recCompress( $node[0], $curBit, $maxCompStart );
                        }
                        if ( $node[1] !== false && $node[1] !== true ) {
                                self::recCompress( $node[1], $curBit, $maxCompStart );
                        }
                }
        }
}