├── README.txt ├── Filter.php └── LICENSE /README.txt: -------------------------------------------------------------------------------- 1 | $filter = new Filter(); 2 | 3 | $allowed_protocols = array('http', 'ftp', 'mailto'); 4 | $allowed_tags = array('a', 'i', 'b', 'em', 'span', 'strong', 'ul', 'ol', 'li', 'table', 'tr', 'td', 'thead', 'th', 'tbody'); 5 | 6 | $filter->addAllowedProtocols($allowed_protocols); 7 | $filter->addAllowedTags($allowed_tags); 8 | 9 | $filtered_string = $filter->xss($string); -------------------------------------------------------------------------------- /Filter.php: -------------------------------------------------------------------------------- 1 | allowed_protocols = (array)$protocols; 10 | } 11 | 12 | public function addAllowedTags($tags) 13 | { 14 | $this->allowed_tags = (array)$tags; 15 | } 16 | 17 | public function xss($string) 18 | { 19 | // Only operate on valid UTF-8 strings. This is necessary to prevent cross 20 | // site scripting issues on Internet Explorer 6. 21 | if (!$this->isUtf8($string)) { 22 | return ''; 23 | } 24 | 25 | // Remove NULL characters (ignored by some browsers). 26 | $string = str_replace(chr(0), '', $string); 27 | 28 | // Remove Netscape 4 JS entities. 29 | $string = preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string); 30 | 31 | // Defuse all HTML entities. 32 | $string = str_replace('&', '&', $string); 33 | 34 | // Change back only well-formed entities in our whitelist: 35 | // Decimal numeric entities. 36 | $string = preg_replace('/&#([0-9]+;)/', '&#\1', $string); 37 | 38 | // Hexadecimal numeric entities. 39 | $string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string); 40 | 41 | // Named entities. 42 | $string = preg_replace('/&([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string); 43 | 44 | return preg_replace_callback('% 45 | ( 46 | <(?=[^a-zA-Z!/]) # a lone < 47 | | # or 48 | # a comment 49 | | # or 50 | <[^>]*(>|$) # a string that starts with a <, up until the > or the end of the string 51 | | # or 52 | > # just a > 53 | )%x', array($this, 'split'), $string); 54 | } 55 | 56 | private function isUtf8($string) 57 | { 58 | if (strlen($string) == 0) { 59 | return true; 60 | } 61 | 62 | return (preg_match('/^./us', $string) == 1); 63 | } 64 | 65 | private function split($m) 66 | { 67 | $string = $m[1]; 68 | 69 | if (substr($string, 0, 1) != '<') { 70 | // We matched a lone ">" character. 71 | return '>'; 72 | } elseif (strlen($string) == 1) { 73 | // We matched a lone "<" character. 74 | return '<'; 75 | } 76 | 77 | if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9\-]+)([^>]*)>?|()$%', $string, $matches)) { 78 | // Seriously malformed. 79 | return ''; 80 | } 81 | 82 | $slash = trim($matches[1]); 83 | $elem = &$matches[2]; 84 | $attrlist = &$matches[3]; 85 | $comment = &$matches[4]; 86 | 87 | if ($comment) { 88 | $elem = '!--'; 89 | } 90 | 91 | if (!in_array(strtolower($elem), $this->allowed_tags, true)) { 92 | // Disallowed HTML element. 93 | return ''; 94 | } 95 | 96 | if ($comment) { 97 | return $comment; 98 | } 99 | 100 | if ($slash != '') { 101 | return ""; 102 | } 103 | 104 | // Is there a closing XHTML slash at the end of the attributes? 105 | $attrlist = preg_replace('%(\s?)/\s*$%', '\1', $attrlist, -1, $count); 106 | $xhtml_slash = $count ? ' /' : ''; 107 | 108 | // Clean up attributes. 109 | $attr2 = implode(' ', $this->attributes($attrlist)); 110 | $attr2 = preg_replace('/[<>]/', '', $attr2); 111 | $attr2 = strlen($attr2) ? ' ' . $attr2 : ''; 112 | 113 | return "<$elem$attr2$xhtml_slash>"; 114 | } 115 | 116 | private function attributes($attr) { 117 | 118 | $attrarr = array(); 119 | $mode = 0; 120 | $attrname = ''; 121 | 122 | while (strlen($attr) != 0) { 123 | // Was the last operation successful? 124 | $working = 0; 125 | 126 | switch ($mode) { 127 | case 0: 128 | // Attribute name, href for instance. 129 | if (preg_match('/^([-a-zA-Z]+)/', $attr, $match)) { 130 | $attrname = strtolower($match[1]); 131 | $skip = ($attrname == 'style' || substr($attrname, 0, 2) == 'on'); 132 | $working = $mode = 1; 133 | $attr = preg_replace('/^[-a-zA-Z]+/', '', $attr); 134 | } 135 | break; 136 | case 1: 137 | // Equals sign or valueless ("selected"). 138 | if (preg_match('/^\s*=\s*/', $attr)) { 139 | $working = 1; 140 | $mode = 2; 141 | $attr = preg_replace('/^\s*=\s*/', '', $attr); 142 | break; 143 | } 144 | 145 | if (preg_match('/^\s+/', $attr)) { 146 | $working = 1; 147 | $mode = 0; 148 | 149 | if (!$skip) { 150 | $attrarr[] = $attrname; 151 | } 152 | 153 | $attr = preg_replace('/^\s+/', '', $attr); 154 | } 155 | break; 156 | case 2: 157 | // Attribute value, a URL after href= for instance. 158 | if (preg_match('/^"([^"]*)"(\s+|$)/', $attr, $match)) { 159 | $thisval = $this->badProtocol($match[1]); 160 | 161 | if (!$skip) { 162 | $attrarr[] = "$attrname=\"$thisval\""; 163 | } 164 | 165 | $working = 1; 166 | $mode = 0; 167 | $attr = preg_replace('/^"[^"]*"(\s+|$)/', '', $attr); 168 | break; 169 | } 170 | 171 | if (preg_match("/^'([^']*)'(\s+|$)/", $attr, $match)) { 172 | $thisval = $this->badProtocol($match[1]); 173 | 174 | if (!$skip) { 175 | $attrarr[] = "$attrname='$thisval'"; 176 | } 177 | 178 | $working = 1; 179 | $mode = 0; 180 | $attr = preg_replace("/^'[^']*'(\s+|$)/", '', $attr); 181 | break; 182 | } 183 | 184 | if (preg_match("%^([^\s\"']+)(\s+|$)%", $attr, $match)) { 185 | $thisval = $this->badProtocol($match[1]); 186 | 187 | if (!$skip) { 188 | $attrarr[] = "$attrname=\"$thisval\""; 189 | } 190 | 191 | $working = 1; 192 | $mode = 0; 193 | $attr = preg_replace("%^[^\s\"']+(\s+|$)%", '', $attr); 194 | } 195 | break; 196 | } 197 | 198 | if ($working == 0) { 199 | // Not well formed; remove and try again. 200 | $attr = preg_replace('/ 201 | ^ 202 | ( 203 | "[^"]*("|$) # - a string that starts with a double quote, up until the next double quote or the end of the string 204 | | # or 205 | \'[^\']*(\'|$)| # - a string that starts with a quote, up until the next quote or the end of the string 206 | | # or 207 | \S # - a non-whitespace character 208 | )* # any number of the above three 209 | \s* # any number of whitespaces 210 | /x', '', $attr); 211 | 212 | $mode = 0; 213 | } 214 | } 215 | 216 | // The attribute list ends with a valueless attribute like "selected". 217 | if ($mode == 1 && !$skip) { 218 | $attrarr[] = $attrname; 219 | } 220 | 221 | return $attrarr; 222 | } 223 | 224 | private function badProtocol($string) { 225 | 226 | $string = html_entity_decode($string, ENT_QUOTES, 'UTF-8'); 227 | return htmlspecialchars($this->stripDangerousProtocols($string), ENT_QUOTES, 'UTF-8'); 228 | } 229 | 230 | private function stripDangerousProtocols($uri) 231 | { 232 | 233 | // Iteratively remove any invalid protocol found. 234 | do { 235 | $before = $uri; 236 | $colonpos = strpos($uri, ':'); 237 | 238 | if ($colonpos > 0) { 239 | // We found a colon, possibly a protocol. Verify. 240 | $protocol = substr($uri, 0, $colonpos); 241 | 242 | // If a colon is preceded by a slash, question mark or hash, it cannot 243 | // possibly be part of the URL scheme. This must be a relative URL, which 244 | // inherits the (safe) protocol of the base document. 245 | if (preg_match('![/?#]!', $protocol)) { 246 | break; 247 | } 248 | 249 | // Check if this is a disallowed protocol. Per RFC2616, section 3.2.3 250 | // (URI Comparison) scheme comparison must be case-insensitive. 251 | if (!in_array(strtolower($protocol), $this->allowed_protocols, true)) { 252 | $uri = substr($uri, $colonpos + 1); 253 | } 254 | } 255 | } while ($before != $uri); 256 | 257 | return $uri; 258 | } 259 | } -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 2, June 1991 3 | 4 | Copyright (C) 1989, 1991 Free Software Foundation, Inc., 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | Preamble 10 | 11 | The licenses for most software are designed to take away your 12 | freedom to share and change it. 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You may copy and distribute verbatim copies of the Program's 80 | source code as you receive it, in any medium, provided that you 81 | conspicuously and appropriately publish on each copy an appropriate 82 | copyright notice and disclaimer of warranty; keep intact all the 83 | notices that refer to this License and to the absence of any warranty; 84 | and give any other recipients of the Program a copy of this License 85 | along with the Program. 86 | 87 | You may charge a fee for the physical act of transferring a copy, and 88 | you may at your option offer warranty protection in exchange for a fee. 89 | 90 | 2. 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You may copy and distribute the Program (or a work based on it, 135 | under Section 2) in object code or executable form under the terms of 136 | Sections 1 and 2 above provided that you also do one of the following: 137 | 138 | a) Accompany it with the complete corresponding machine-readable 139 | source code, which must be distributed under the terms of Sections 140 | 1 and 2 above on a medium customarily used for software interchange; or, 141 | 142 | b) Accompany it with a written offer, valid for at least three 143 | years, to give any third party, for a charge no more than your 144 | cost of physically performing source distribution, a complete 145 | machine-readable copy of the corresponding source code, to be 146 | distributed under the terms of Sections 1 and 2 above on a medium 147 | customarily used for software interchange; or, 148 | 149 | c) Accompany it with the information you received as to the offer 150 | to distribute corresponding source code. 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Any attempt 174 | otherwise to copy, modify, sublicense or distribute the Program is 175 | void, and will automatically terminate your rights under this License. 176 | However, parties who have received copies, or rights, from you under 177 | this License will not have their licenses terminated so long as such 178 | parties remain in full compliance. 179 | 180 | 5. You are not required to accept this License, since you have not 181 | signed it. However, nothing else grants you permission to modify or 182 | distribute the Program or its derivative works. These actions are 183 | prohibited by law if you do not accept this License. Therefore, by 184 | modifying or distributing the Program (or any work based on the 185 | Program), you indicate your acceptance of this License to do so, and 186 | all its terms and conditions for copying, distributing or modifying 187 | the Program or works based on it. 188 | 189 | 6. Each time you redistribute the Program (or any work based on the 190 | Program), the recipient automatically receives a license from the 191 | original licensor to copy, distribute or modify the Program subject to 192 | these terms and conditions. You may not impose any further 193 | restrictions on the recipients' exercise of the rights granted herein. 194 | You are not responsible for enforcing compliance by third parties to 195 | this License. 196 | 197 | 7. If, as a consequence of a court judgment or allegation of patent 198 | infringement or for any other reason (not limited to patent issues), 199 | conditions are imposed on you (whether by court order, agreement or 200 | otherwise) that contradict the conditions of this License, they do not 201 | excuse you from the conditions of this License. If you cannot 202 | distribute so as to satisfy simultaneously your obligations under this 203 | License and any other pertinent obligations, then as a consequence you 204 | may not distribute the Program at all. For example, if a patent 205 | license would not permit royalty-free redistribution of the Program by 206 | all those who receive copies directly or indirectly through you, then 207 | the only way you could satisfy both it and this License would be to 208 | refrain entirely from distribution of the Program. 209 | 210 | If any portion of this section is held invalid or unenforceable under 211 | any particular circumstance, the balance of the section is intended to 212 | apply and the section as a whole is intended to apply in other 213 | circumstances. 214 | 215 | It is not the purpose of this section to induce you to infringe any 216 | patents or other property right claims or to contest validity of any 217 | such claims; this section has the sole purpose of protecting the 218 | integrity of the free software distribution system, which is 219 | implemented by public license practices. Many people have made 220 | generous contributions to the wide range of software distributed 221 | through that system in reliance on consistent application of that 222 | system; it is up to the author/donor to decide if he or she is willing 223 | to distribute software through any other system and a licensee cannot 224 | impose that choice. 225 | 226 | This section is intended to make thoroughly clear what is believed to 227 | be a consequence of the rest of this License. 228 | 229 | 8. If the distribution and/or use of the Program is restricted in 230 | certain countries either by patents or by copyrighted interfaces, the 231 | original copyright holder who places the Program under this License 232 | may add an explicit geographical distribution limitation excluding 233 | those countries, so that distribution is permitted only in or among 234 | countries not thus excluded. In such case, this License incorporates 235 | the limitation as if written in the body of this License. 236 | 237 | 9. The Free Software Foundation may publish revised and/or new versions 238 | of the General Public License from time to time. Such new versions will 239 | be similar in spirit to the present version, but may differ in detail to 240 | address new problems or concerns. 241 | 242 | Each version is given a distinguishing version number. If the Program 243 | specifies a version number of this License which applies to it and "any 244 | later version", you have the option of following the terms and conditions 245 | either of that version or of any later version published by the Free 246 | Software Foundation. If the Program does not specify a version number of 247 | this License, you may choose any version ever published by the Free Software 248 | Foundation. 249 | 250 | 10. If you wish to incorporate parts of the Program into other free 251 | programs whose distribution conditions are different, write to the author 252 | to ask for permission. For software which is copyrighted by the Free 253 | Software Foundation, write to the Free Software Foundation; we sometimes 254 | make exceptions for this. Our decision will be guided by the two goals 255 | of preserving the free status of all derivatives of our free software and 256 | of promoting the sharing and reuse of software generally. 257 | 258 | NO WARRANTY 259 | 260 | 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY 261 | FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN 262 | OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES 263 | PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED 264 | OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 265 | MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS 266 | TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE 267 | PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, 268 | REPAIR OR CORRECTION. 269 | 270 | 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 271 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR 272 | REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, 273 | INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING 274 | OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED 275 | TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY 276 | YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER 277 | PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE 278 | POSSIBILITY OF SUCH DAMAGES. 279 | 280 | END OF TERMS AND CONDITIONS 281 | 282 | How to Apply These Terms to Your New Programs 283 | 284 | If you develop a new program, and you want it to be of the greatest 285 | possible use to the public, the best way to achieve this is to make it 286 | free software which everyone can redistribute and change under these terms. 287 | 288 | To do so, attach the following notices to the program. It is safest 289 | to attach them to the start of each source file to most effectively 290 | convey the exclusion of warranty; and each file should have at least 291 | the "copyright" line and a pointer to where the full notice is found. 292 | 293 | {description} 294 | Copyright (C) {year} {fullname} 295 | 296 | This program is free software; you can redistribute it and/or modify 297 | it under the terms of the GNU General Public License as published by 298 | the Free Software Foundation; either version 2 of the License, or 299 | (at your option) any later version. 300 | 301 | This program is distributed in the hope that it will be useful, 302 | but WITHOUT ANY WARRANTY; without even the implied warranty of 303 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 304 | GNU General Public License for more details. 305 | 306 | You should have received a copy of the GNU General Public License along 307 | with this program; if not, write to the Free Software Foundation, Inc., 308 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 309 | 310 | Also add information on how to contact you by electronic and paper mail. 311 | 312 | If the program is interactive, make it output a short notice like this 313 | when it starts in an interactive mode: 314 | 315 | Gnomovision version 69, Copyright (C) year name of author 316 | Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 317 | This is free software, and you are welcome to redistribute it 318 | under certain conditions; type `show c' for details. 319 | 320 | The hypothetical commands `show w' and `show c' should show the appropriate 321 | parts of the General Public License. Of course, the commands you use may 322 | be called something other than `show w' and `show c'; they could even be 323 | mouse-clicks or menu items--whatever suits your program. 324 | 325 | You should also get your employer (if you work as a programmer) or your 326 | school, if any, to sign a "copyright disclaimer" for the program, if 327 | necessary. Here is a sample; alter the names: 328 | 329 | Yoyodyne, Inc., hereby disclaims all copyright interest in the program 330 | `Gnomovision' (which makes passes at compilers) written by James Hacker. 331 | 332 | {signature of Ty Coon}, 1 April 1989 333 | Ty Coon, President of Vice 334 | 335 | This General Public License does not permit incorporating your program into 336 | proprietary programs. If your program is a subroutine library, you may 337 | consider it more useful to permit linking proprietary applications with the 338 | library. If this is what you want to do, use the GNU Lesser General 339 | Public License instead of this License. 340 | 341 | --------------------------------------------------------------------------------