1<?php
2// This file is part of Moodle - http://moodle.org/
3//
4// Moodle is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8//
9// Moodle is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12// GNU General Public License for more details.
13//
14// You should have received a copy of the GNU General Public License
15// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
16
17/**
18 * Contains a simple class providing some useful internet protocol-related functions.
19 *
20 * @package   core
21 * @copyright 2016 Jake Dallimore
22 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
23 * @author    Jake Dallimore <jrhdallimore@gmail.com>
24 */
25
26namespace core;
27
28defined('MOODLE_INTERNAL') || exit();
29
30/**
31 * Static helper class providing some useful internet-protocol-related functions.
32 *
33 * @package   core
34 * @copyright 2016 Jake Dallimore
35 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
36 * @author    Jake Dallimore <jrhdallimore@gmail.com>
37 */
38final class ip_utils {
39    /**
40     * Syntax checking for domain names, including fully qualified domain names.
41     *
42     * This function does not verify the existence of the domain name. It only verifies syntactic correctness.
43     * This is based on RFC1034/1035 and does not provide support for validation of internationalised domain names (IDNs).
44     * All IDNs must be prior-converted to their ascii-compatible encoding before being passed to this function.
45     *
46     * @param string $domainname the input string to check.
47     * @return bool true if the string has valid syntax, false otherwise.
48     */
49    public static function is_domain_name($domainname) {
50        if (!is_string($domainname)) {
51            return false;
52        }
53        // Usually the trailing dot (null label) is omitted, but is valid if supplied. We'll just remove it and validate as normal.
54        $domainname = rtrim($domainname, '.');
55
56        // The entire name cannot exceed 253 ascii characters (255 octets, less the leading label-length byte and null label byte).
57        if (strlen($domainname) > 253) {
58            return false;
59        }
60        // Tertiary domain labels can have 63 octets max, and must not have begin or end with a hyphen.
61        // The TLD label cannot begin with a number, but otherwise, is only loosely restricted here (TLD list is not checked).
62        $domaintertiary = '([a-zA-Z0-9](([a-zA-Z0-9-]{0,61})[a-zA-Z0-9])?\.)*';
63        $domaintoplevel = '([a-zA-Z](([a-zA-Z0-9-]*)[a-zA-Z0-9])?)';
64        $address = '(' . $domaintertiary .  $domaintoplevel . ')';
65        $regexp = '#^' . $address . '$#i'; // Case insensitive matching.
66        return preg_match($regexp, $domainname, $match) == true; // False for error, 0 for no match - we treat the same.
67    }
68
69    /**
70     * Checks whether the input string is a valid wildcard domain matching pattern.
71     *
72     * A domain matching pattern is essentially a domain name with a single, leading wildcard (*) label, and at least one other
73     * label. The wildcard label is considered to match at least one label at or above (to the left of) its position in the string,
74     * but will not match the trailing domain (everything to its right).
75     *
76     * The string must be dot-separated, and the whole pattern must follow the domain name syntax rules defined in RFC1034/1035.
77     * Namely, the character type (ascii), total-length (253) and label-length (63) restrictions. This function only confirms
78     * syntactic correctness. It does not check for the existence of the domain/subdomains.
79     *
80     * For example, the string '*.example.com' is a pattern deemed to match any direct subdomain of
81     * example.com (such as test.example.com), any higher level subdomains (e.g. another.test.example.com) but will not match
82     * the 'example.com' domain itself.
83     *
84     * @param string $pattern the string to check.
85     * @return bool true if the input string is a valid domain wildcard matching pattern, false otherwise.
86     */
87    public static function is_domain_matching_pattern($pattern) {
88        if (!is_string($pattern)) {
89            return false;
90        }
91        // Usually the trailing dot (null label) is omitted, but is valid if supplied. We'll just remove it and validate as normal.
92        $pattern = rtrim($pattern, '.');
93
94        // The entire name cannot exceed 253 ascii characters (255 octets, less the leading label-length byte and null label byte).
95        if (strlen($pattern) > 253) {
96            return false;
97        }
98        // A valid pattern must left-positioned wildcard symbol (*).
99        // Tertiary domain labels can have 63 octets max, and must not have begin or end with a hyphen.
100        // The TLD label cannot begin with a number, but otherwise, is only loosely restricted here (TLD list is not checked).
101        $wildcard = '((\*)\.){1}';
102        $domaintertiary = '([a-zA-Z0-9](([a-zA-Z0-9-]{0,61})[a-zA-Z0-9])?\.)*';
103        $domaintoplevel = '([a-zA-Z](([a-zA-Z0-9-]*)[a-zA-Z0-9])?)';
104        $address = '(' . $wildcard . $domaintertiary .  $domaintoplevel . ')';
105        $regexp = '#^' . $address . '$#i'; // Case insensitive matching.
106        return preg_match($regexp, $pattern, $match) == true; // False for error, 0 for no match - we treat the same.
107    }
108
109    /**
110     * Syntax validation for IP addresses, supporting both IPv4 and Ipv6 formats.
111     *
112     * @param string $address the address to check.
113     * @return bool true if the address is a valid IPv4 of IPv6 address, false otherwise.
114     */
115    public static function is_ip_address($address) {
116        return filter_var($address, FILTER_VALIDATE_IP) !== false;
117    }
118
119    /**
120     * Syntax validation for IPv4 addresses.
121     *
122     * @param string $address the address to check.
123     * @return bool true if the address is a valid IPv4 address, false otherwise.
124     */
125    public static function is_ipv4_address($address) {
126        return filter_var($address, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4) !== false;
127    }
128
129    /**
130     * Syntax checking for IPv4 address ranges.
131     * Supports CIDR notation and last-group ranges.
132     * Eg. 127.0.0.0/24 or 127.0.0.80-255
133     *
134     * @param string $addressrange the address range to check.
135     * @return bool true if the string is a valid range representation, false otherwise.
136     */
137    public static function is_ipv4_range($addressrange) {
138        // Check CIDR notation.
139        if (preg_match('#^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\/(\d{1,2})$#', $addressrange, $match)) {
140            $address = "{$match[1]}.{$match[2]}.{$match[3]}.{$match[4]}";
141            return self::is_ipv4_address($address) && $match[5] <= 32;
142        }
143        // Check last-group notation.
144        if (preg_match('#^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})-(\d{1,3})$#', $addressrange, $match)) {
145            $address = "{$match[1]}.{$match[2]}.{$match[3]}.{$match[4]}";
146            return self::is_ipv4_address($address) && $match[5] <= 255 && $match[5] >= $match[4];
147        }
148        return false;
149    }
150
151    /**
152     * Syntax validation for IPv6 addresses.
153     * This function does not check whether the address is assigned, only its syntactical correctness.
154     *
155     * @param string $address the address to check.
156     * @return bool true if the address is a valid IPv6 address, false otherwise.
157     */
158    public static function is_ipv6_address($address) {
159        return filter_var($address, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6) !== false;
160    }
161
162    /**
163     * Syntax validation for IPv6 address ranges.
164     * Supports CIDR notation and last-group ranges.
165     * Eg. fe80::d98c/64 or fe80::d98c-ffee
166     *
167     * @param string $addressrange the IPv6 address range to check.
168     * @return bool true if the string is a valid range representation, false otherwise.
169     */
170    public static function is_ipv6_range($addressrange) {
171        // Check CIDR notation.
172        $ipv6parts = explode('/', $addressrange);
173        if (count($ipv6parts) == 2) {
174            $range = (int)$ipv6parts[1];
175            return self::is_ipv6_address($ipv6parts[0]) && (string)$range === $ipv6parts[1] && $range >= 0 && $range <= 128;
176        }
177        // Check last-group notation.
178        $ipv6parts = explode('-', $addressrange);
179        if (count($ipv6parts) == 2) {
180            $addressparts = explode(':', $ipv6parts[0]);
181            $rangestart = $addressparts[count($addressparts) - 1];
182            $rangeend = $ipv6parts[1];
183            return self::is_ipv6_address($ipv6parts[0]) && ctype_xdigit($rangestart) && ctype_xdigit($rangeend)
184            && strlen($rangeend) <= 4 && strlen($rangestart) <= 4 && hexdec($rangeend) >= hexdec($rangestart);
185        }
186        return false;
187    }
188
189    /**
190     * Checks the domain name against a list of allowed domains. The list of allowed domains is may use
191     * wildcards that match {@link is_domain_matching_pattern()}.
192     *
193     * @param  string $domain Domain address
194     * @param  array $alloweddomains An array of allowed domains.
195     * @return boolean True if the domain matches one of the entries in the allowed domains list.
196     */
197    public static function is_domain_in_allowed_list($domain, $alloweddomains) {
198
199        if (!self::is_domain_name($domain)) {
200            return false;
201        }
202
203        foreach ($alloweddomains as $alloweddomain) {
204            if (strpos($alloweddomain, '*') !== false) {
205                if (!self::is_domain_matching_pattern($alloweddomain)) {
206                    continue;
207                }
208                // Use of wildcard for possible subdomains.
209                $escapeperiods = str_replace('.', '\.', $alloweddomain);
210                $replacewildcard = str_replace('*', '.*', $escapeperiods);
211                $ultimatepattern = '/' . $replacewildcard . '$/';
212                if (preg_match($ultimatepattern, $domain)) {
213                    return true;
214                }
215            } else {
216                if (!self::is_domain_name($alloweddomain)) {
217                    continue;
218                }
219                // Strict domain setting.
220                if ($domain === $alloweddomain) {
221                    return true;
222                }
223            }
224        }
225        return false;
226    }
227
228    /**
229     * Is an ip in a given list of subnets?
230     *
231     * @param string $ip - the IP to test against the list
232     * @param string $list - the list of IP subnets
233     * @param string $delim a delimiter of the list
234     * @return bool
235     */
236    public static function is_ip_in_subnet_list($ip, $list, $delim = "\n") {
237        $list = explode($delim, $list);
238        foreach ($list as $line) {
239            $tokens = explode('#', $line);
240            $subnet = trim($tokens[0]);
241            if (address_in_subnet($ip, $subnet)) {
242                return true;
243            }
244        }
245        return false;
246    }
247
248    /**
249     * Return IP address for given hostname, or null on failure
250     *
251     * @param string $hostname
252     * @return string|null
253     */
254    public static function get_ip_address(string $hostname): ?string {
255        if (self::is_domain_name($hostname)) {
256            $address = gethostbyname($hostname);
257
258            // If address is different from hostname, we have success.
259            if (strcasecmp($address, $hostname) !== 0) {
260                return $address;
261            }
262        }
263
264        return null;
265    }
266}
267