X-Git-Url: https://scripts.mit.edu/gitweb/autoinstallsdev/mediawiki.git/blobdiff_plain/19e297c21b10b1b8a3acad5e73fc71dcb35db44a..6932310fd58ebef145fa01eb76edf7150284d8ea:/includes/utils/ZipDirectoryReader.php

diff --git a/includes/utils/ZipDirectoryReader.php b/includes/utils/ZipDirectoryReader.php
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--- /dev/null
+++ b/includes/utils/ZipDirectoryReader.php
@@ -0,0 +1,717 @@
+<?php
+/**
+ * ZIP file directories reader, for the purposes of upload verification.
+ *
+ * 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
+ */
+
+/**
+ * A class for reading ZIP file directories, for the purposes of upload
+ * verification.
+ *
+ * Only a functional interface is provided: ZipFileReader::read(). No access is
+ * given to object instances.
+ */
+class ZipDirectoryReader {
+	/**
+	 * Read a ZIP file and call a function for each file discovered in it.
+	 *
+	 * Because this class is aimed at verification, an error is raised on
+	 * suspicious or ambiguous input, instead of emulating some standard
+	 * behavior.
+	 *
+	 * @param string $fileName The archive file name
+	 * @param array $callback The callback function. It will be called for each file
+	 *   with a single associative array each time, with members:
+	 *
+	 *      - name: The file name. Directories conventionally have a trailing
+	 *        slash.
+	 *
+	 *      - mtime: The file modification time, in MediaWiki 14-char format
+	 *
+	 *      - size: The uncompressed file size
+	 *
+	 * @param array $options An associative array of read options, with the option
+	 *    name in the key. This may currently contain:
+	 *
+	 *      - zip64: If this is set to true, then we will emulate a
+	 *        library with ZIP64 support, like OpenJDK 7. If it is set to
+	 *        false, then we will emulate a library with no knowledge of
+	 *        ZIP64.
+	 *
+	 *        NOTE: The ZIP64 code is untested and probably doesn't work. It
+	 *        turned out to be easier to just reject ZIP64 archive uploads,
+	 *        since they are likely to be very rare. Confirming safety of a
+	 *        ZIP64 file is fairly complex. What do you do with a file that is
+	 *        ambiguous and broken when read with a non-ZIP64 reader, but valid
+	 *        when read with a ZIP64 reader? This situation is normal for a
+	 *        valid ZIP64 file, and working out what non-ZIP64 readers will make
+	 *        of such a file is not trivial.
+	 *
+	 * @return Status A Status object. The following fatal errors are defined:
+	 *
+	 *      - zip-file-open-error: The file could not be opened.
+	 *
+	 *      - zip-wrong-format: The file does not appear to be a ZIP file.
+	 *
+	 *      - zip-bad: There was something wrong or ambiguous about the file
+	 *        data.
+	 *
+	 *      - zip-unsupported: The ZIP file uses features which
+	 *        ZipDirectoryReader does not support.
+	 *
+	 * The default messages for those fatal errors are written in a way that
+	 * makes sense for upload verification.
+	 *
+	 * If a fatal error is returned, more information about the error will be
+	 * available in the debug log.
+	 *
+	 * Note that the callback function may be called any number of times before
+	 * a fatal error is returned. If this occurs, the data sent to the callback
+	 * function should be discarded.
+	 */
+	public static function read( $fileName, $callback, $options = [] ) {
+		$zdr = new self( $fileName, $callback, $options );
+
+		return $zdr->execute();
+	}
+
+	/** The file name */
+	protected $fileName;
+
+	/** The opened file resource */
+	protected $file;
+
+	/** The cached length of the file, or null if it has not been loaded yet. */
+	protected $fileLength;
+
+	/** A segmented cache of the file contents */
+	protected $buffer;
+
+	/** The file data callback */
+	protected $callback;
+
+	/** The ZIP64 mode */
+	protected $zip64 = false;
+
+	/** Stored headers */
+	protected $eocdr, $eocdr64, $eocdr64Locator;
+
+	protected $data;
+
+	/** The "extra field" ID for ZIP64 central directory entries */
+	const ZIP64_EXTRA_HEADER = 0x0001;
+
+	/** The segment size for the file contents cache */
+	const SEGSIZE = 16384;
+
+	/** The index of the "general field" bit for UTF-8 file names */
+	const GENERAL_UTF8 = 11;
+
+	/** The index of the "general field" bit for central directory encryption */
+	const GENERAL_CD_ENCRYPTED = 13;
+
+	/**
+	 * Private constructor
+	 * @param string $fileName
+	 * @param callable $callback
+	 * @param array $options
+	 */
+	protected function __construct( $fileName, $callback, $options ) {
+		$this->fileName = $fileName;
+		$this->callback = $callback;
+
+		if ( isset( $options['zip64'] ) ) {
+			$this->zip64 = $options['zip64'];
+		}
+	}
+
+	/**
+	 * Read the directory according to settings in $this.
+	 *
+	 * @return Status
+	 */
+	function execute() {
+		$this->file = fopen( $this->fileName, 'r' );
+		$this->data = [];
+		if ( !$this->file ) {
+			return Status::newFatal( 'zip-file-open-error' );
+		}
+
+		$status = Status::newGood();
+		try {
+			$this->readEndOfCentralDirectoryRecord();
+			if ( $this->zip64 ) {
+				list( $offset, $size ) = $this->findZip64CentralDirectory();
+				$this->readCentralDirectory( $offset, $size );
+			} else {
+				if ( $this->eocdr['CD size'] == 0xffffffff
+					|| $this->eocdr['CD offset'] == 0xffffffff
+					|| $this->eocdr['CD entries total'] == 0xffff
+				) {
+					$this->error( 'zip-unsupported', 'Central directory header indicates ZIP64, ' .
+						'but we are in legacy mode. Rejecting this upload is necessary to avoid ' .
+						'opening vulnerabilities on clients using OpenJDK 7 or later.' );
+				}
+
+				list( $offset, $size ) = $this->findOldCentralDirectory();
+				$this->readCentralDirectory( $offset, $size );
+			}
+		} catch ( ZipDirectoryReaderError $e ) {
+			$status->fatal( $e->getErrorCode() );
+		}
+
+		fclose( $this->file );
+
+		return $status;
+	}
+
+	/**
+	 * Throw an error, and log a debug message
+	 * @param mixed $code
+	 * @param string $debugMessage
+	 * @throws ZipDirectoryReaderError
+	 */
+	function error( $code, $debugMessage ) {
+		wfDebug( __CLASS__ . ": Fatal error: $debugMessage\n" );
+		throw new ZipDirectoryReaderError( $code );
+	}
+
+	/**
+	 * Read the header which is at the end of the central directory,
+	 * unimaginatively called the "end of central directory record" by the ZIP
+	 * spec.
+	 */
+	function readEndOfCentralDirectoryRecord() {
+		$info = [
+			'signature' => 4,
+			'disk' => 2,
+			'CD start disk' => 2,
+			'CD entries this disk' => 2,
+			'CD entries total' => 2,
+			'CD size' => 4,
+			'CD offset' => 4,
+			'file comment length' => 2,
+		];
+		$structSize = $this->getStructSize( $info );
+		$startPos = $this->getFileLength() - 65536 - $structSize;
+		if ( $startPos < 0 ) {
+			$startPos = 0;
+		}
+
+		if ( $this->getFileLength() === 0 ) {
+			$this->error( 'zip-wrong-format', "The file is empty." );
+		}
+
+		$block = $this->getBlock( $startPos );
+		$sigPos = strrpos( $block, "PK\x05\x06" );
+		if ( $sigPos === false ) {
+			$this->error( 'zip-wrong-format',
+				"zip file lacks EOCDR signature. It probably isn't a zip file." );
+		}
+
+		$this->eocdr = $this->unpack( substr( $block, $sigPos ), $info );
+		$this->eocdr['EOCDR size'] = $structSize + $this->eocdr['file comment length'];
+
+		if ( $structSize + $this->eocdr['file comment length'] != strlen( $block ) - $sigPos ) {
+			$this->error( 'zip-bad', 'trailing bytes after the end of the file comment' );
+		}
+		if ( $this->eocdr['disk'] !== 0
+			|| $this->eocdr['CD start disk'] !== 0
+		) {
+			$this->error( 'zip-unsupported', 'more than one disk (in EOCDR)' );
+		}
+		$this->eocdr += $this->unpack(
+			$block,
+			[ 'file comment' => [ 'string', $this->eocdr['file comment length'] ] ],
+			$sigPos + $structSize );
+		$this->eocdr['position'] = $startPos + $sigPos;
+	}
+
+	/**
+	 * Read the header called the "ZIP64 end of central directory locator". An
+	 * error will be raised if it does not exist.
+	 */
+	function readZip64EndOfCentralDirectoryLocator() {
+		$info = [
+			'signature' => [ 'string', 4 ],
+			'eocdr64 start disk' => 4,
+			'eocdr64 offset' => 8,
+			'number of disks' => 4,
+		];
+		$structSize = $this->getStructSize( $info );
+
+		$start = $this->getFileLength() - $this->eocdr['EOCDR size'] - $structSize;
+		$block = $this->getBlock( $start, $structSize );
+		$this->eocdr64Locator = $data = $this->unpack( $block, $info );
+
+		if ( $data['signature'] !== "PK\x06\x07" ) {
+			// Note: Java will allow this and continue to read the
+			// EOCDR64, so we have to reject the upload, we can't
+			// just use the EOCDR header instead.
+			$this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory locator' );
+		}
+	}
+
+	/**
+	 * Read the header called the "ZIP64 end of central directory record". It
+	 * may replace the regular "end of central directory record" in ZIP64 files.
+	 */
+	function readZip64EndOfCentralDirectoryRecord() {
+		if ( $this->eocdr64Locator['eocdr64 start disk'] != 0
+			|| $this->eocdr64Locator['number of disks'] != 0
+		) {
+			$this->error( 'zip-unsupported', 'more than one disk (in EOCDR64 locator)' );
+		}
+
+		$info = [
+			'signature' => [ 'string', 4 ],
+			'EOCDR64 size' => 8,
+			'version made by' => 2,
+			'version needed' => 2,
+			'disk' => 4,
+			'CD start disk' => 4,
+			'CD entries this disk' => 8,
+			'CD entries total' => 8,
+			'CD size' => 8,
+			'CD offset' => 8
+		];
+		$structSize = $this->getStructSize( $info );
+		$block = $this->getBlock( $this->eocdr64Locator['eocdr64 offset'], $structSize );
+		$this->eocdr64 = $data = $this->unpack( $block, $info );
+		if ( $data['signature'] !== "PK\x06\x06" ) {
+			$this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory record' );
+		}
+		if ( $data['disk'] !== 0
+			|| $data['CD start disk'] !== 0
+		) {
+			$this->error( 'zip-unsupported', 'more than one disk (in EOCDR64)' );
+		}
+	}
+
+	/**
+	 * Find the location of the central directory, as would be seen by a
+	 * non-ZIP64 reader.
+	 *
+	 * @return array List containing offset, size and end position.
+	 */
+	function findOldCentralDirectory() {
+		$size = $this->eocdr['CD size'];
+		$offset = $this->eocdr['CD offset'];
+		$endPos = $this->eocdr['position'];
+
+		// Some readers use the EOCDR position instead of the offset field
+		// to find the directory, so to be safe, we check if they both agree.
+		if ( $offset + $size != $endPos ) {
+			$this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
+				'of central directory record' );
+		}
+
+		return [ $offset, $size ];
+	}
+
+	/**
+	 * Find the location of the central directory, as would be seen by a
+	 * ZIP64-compliant reader.
+	 *
+	 * @return array List containing offset, size and end position.
+	 */
+	function findZip64CentralDirectory() {
+		// The spec is ambiguous about the exact rules of precedence between the
+		// ZIP64 headers and the original headers. Here we follow zip_util.c
+		// from OpenJDK 7.
+		$size = $this->eocdr['CD size'];
+		$offset = $this->eocdr['CD offset'];
+		$numEntries = $this->eocdr['CD entries total'];
+		$endPos = $this->eocdr['position'];
+		if ( $size == 0xffffffff
+			|| $offset == 0xffffffff
+			|| $numEntries == 0xffff
+		) {
+			$this->readZip64EndOfCentralDirectoryLocator();
+
+			if ( isset( $this->eocdr64Locator['eocdr64 offset'] ) ) {
+				$this->readZip64EndOfCentralDirectoryRecord();
+				if ( isset( $this->eocdr64['CD offset'] ) ) {
+					$size = $this->eocdr64['CD size'];
+					$offset = $this->eocdr64['CD offset'];
+					$endPos = $this->eocdr64Locator['eocdr64 offset'];
+				}
+			}
+		}
+		// Some readers use the EOCDR position instead of the offset field
+		// to find the directory, so to be safe, we check if they both agree.
+		if ( $offset + $size != $endPos ) {
+			$this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
+				'of central directory record' );
+		}
+
+		return [ $offset, $size ];
+	}
+
+	/**
+	 * Read the central directory at the given location
+	 * @param int $offset
+	 * @param int $size
+	 */
+	function readCentralDirectory( $offset, $size ) {
+		$block = $this->getBlock( $offset, $size );
+
+		$fixedInfo = [
+			'signature' => [ 'string', 4 ],
+			'version made by' => 2,
+			'version needed' => 2,
+			'general bits' => 2,
+			'compression method' => 2,
+			'mod time' => 2,
+			'mod date' => 2,
+			'crc-32' => 4,
+			'compressed size' => 4,
+			'uncompressed size' => 4,
+			'name length' => 2,
+			'extra field length' => 2,
+			'comment length' => 2,
+			'disk number start' => 2,
+			'internal attrs' => 2,
+			'external attrs' => 4,
+			'local header offset' => 4,
+		];
+		$fixedSize = $this->getStructSize( $fixedInfo );
+
+		$pos = 0;
+		while ( $pos < $size ) {
+			$data = $this->unpack( $block, $fixedInfo, $pos );
+			$pos += $fixedSize;
+
+			if ( $data['signature'] !== "PK\x01\x02" ) {
+				$this->error( 'zip-bad', 'Invalid signature found in directory entry' );
+			}
+
+			$variableInfo = [
+				'name' => [ 'string', $data['name length'] ],
+				'extra field' => [ 'string', $data['extra field length'] ],
+				'comment' => [ 'string', $data['comment length'] ],
+			];
+			$data += $this->unpack( $block, $variableInfo, $pos );
+			$pos += $this->getStructSize( $variableInfo );
+
+			if ( $this->zip64 && (
+					$data['compressed size'] == 0xffffffff
+					|| $data['uncompressed size'] == 0xffffffff
+					|| $data['local header offset'] == 0xffffffff )
+			) {
+				$zip64Data = $this->unpackZip64Extra( $data['extra field'] );
+				if ( $zip64Data ) {
+					$data = $zip64Data + $data;
+				}
+			}
+
+			if ( $this->testBit( $data['general bits'], self::GENERAL_CD_ENCRYPTED ) ) {
+				$this->error( 'zip-unsupported', 'central directory encryption is not supported' );
+			}
+
+			// Convert the timestamp into MediaWiki format
+			// For the format, please see the MS-DOS 2.0 Programmer's Reference,
+			// pages 3-5 and 3-6.
+			$time = $data['mod time'];
+			$date = $data['mod date'];
+
+			$year = 1980 + ( $date >> 9 );
+			$month = ( $date >> 5 ) & 15;
+			$day = $date & 31;
+			$hour = ( $time >> 11 ) & 31;
+			$minute = ( $time >> 5 ) & 63;
+			$second = ( $time & 31 ) * 2;
+			$timestamp = sprintf( "%04d%02d%02d%02d%02d%02d",
+				$year, $month, $day, $hour, $minute, $second );
+
+			// Convert the character set in the file name
+			if ( $this->testBit( $data['general bits'], self::GENERAL_UTF8 ) ) {
+				$name = $data['name'];
+			} else {
+				$name = iconv( 'CP437', 'UTF-8', $data['name'] );
+			}
+
+			// Compile a data array for the user, with a sensible format
+			$userData = [
+				'name' => $name,
+				'mtime' => $timestamp,
+				'size' => $data['uncompressed size'],
+			];
+			call_user_func( $this->callback, $userData );
+		}
+	}
+
+	/**
+	 * Interpret ZIP64 "extra field" data and return an associative array.
+	 * @param string $extraField
+	 * @return array|bool
+	 */
+	function unpackZip64Extra( $extraField ) {
+		$extraHeaderInfo = [
+			'id' => 2,
+			'size' => 2,
+		];
+		$extraHeaderSize = $this->getStructSize( $extraHeaderInfo );
+
+		$zip64ExtraInfo = [
+			'uncompressed size' => 8,
+			'compressed size' => 8,
+			'local header offset' => 8,
+			'disk number start' => 4,
+		];
+
+		$extraPos = 0;
+		while ( $extraPos < strlen( $extraField ) ) {
+			$extra = $this->unpack( $extraField, $extraHeaderInfo, $extraPos );
+			$extraPos += $extraHeaderSize;
+			$extra += $this->unpack( $extraField,
+				[ 'data' => [ 'string', $extra['size'] ] ],
+				$extraPos );
+			$extraPos += $extra['size'];
+
+			if ( $extra['id'] == self::ZIP64_EXTRA_HEADER ) {
+				return $this->unpack( $extra['data'], $zip64ExtraInfo );
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * Get the length of the file.
+	 * @return int
+	 */
+	function getFileLength() {
+		if ( $this->fileLength === null ) {
+			$stat = fstat( $this->file );
+			$this->fileLength = $stat['size'];
+		}
+
+		return $this->fileLength;
+	}
+
+	/**
+	 * Get the file contents from a given offset. If there are not enough bytes
+	 * in the file to satisfy the request, an exception will be thrown.
+	 *
+	 * @param int $start The byte offset of the start of the block.
+	 * @param int $length The number of bytes to return. If omitted, the remainder
+	 *    of the file will be returned.
+	 *
+	 * @return string
+	 */
+	function getBlock( $start, $length = null ) {
+		$fileLength = $this->getFileLength();
+		if ( $start >= $fileLength ) {
+			$this->error( 'zip-bad', "getBlock() requested position $start, " .
+				"file length is $fileLength" );
+		}
+		if ( $length === null ) {
+			$length = $fileLength - $start;
+		}
+		$end = $start + $length;
+		if ( $end > $fileLength ) {
+			$this->error( 'zip-bad', "getBlock() requested end position $end, " .
+				"file length is $fileLength" );
+		}
+		$startSeg = floor( $start / self::SEGSIZE );
+		$endSeg = ceil( $end / self::SEGSIZE );
+
+		$block = '';
+		for ( $segIndex = $startSeg; $segIndex <= $endSeg; $segIndex++ ) {
+			$block .= $this->getSegment( $segIndex );
+		}
+
+		$block = substr( $block,
+			$start - $startSeg * self::SEGSIZE,
+			$length );
+
+		if ( strlen( $block ) < $length ) {
+			$this->error( 'zip-bad', 'getBlock() returned an unexpectedly small amount of data' );
+		}
+
+		return $block;
+	}
+
+	/**
+	 * Get a section of the file starting at position $segIndex * self::SEGSIZE,
+	 * of length self::SEGSIZE. The result is cached. This is a helper function
+	 * for getBlock().
+	 *
+	 * If there are not enough bytes in the file to satisfy the request, the
+	 * return value will be truncated. If a request is made for a segment beyond
+	 * the end of the file, an empty string will be returned.
+	 *
+	 * @param int $segIndex
+	 *
+	 * @return string
+	 */
+	function getSegment( $segIndex ) {
+		if ( !isset( $this->buffer[$segIndex] ) ) {
+			$bytePos = $segIndex * self::SEGSIZE;
+			if ( $bytePos >= $this->getFileLength() ) {
+				$this->buffer[$segIndex] = '';
+
+				return '';
+			}
+			if ( fseek( $this->file, $bytePos ) ) {
+				$this->error( 'zip-bad', "seek to $bytePos failed" );
+			}
+			$seg = fread( $this->file, self::SEGSIZE );
+			if ( $seg === false ) {
+				$this->error( 'zip-bad', "read from $bytePos failed" );
+			}
+			$this->buffer[$segIndex] = $seg;
+		}
+
+		return $this->buffer[$segIndex];
+	}
+
+	/**
+	 * Get the size of a structure in bytes. See unpack() for the format of $struct.
+	 * @param array $struct
+	 * @return int
+	 */
+	function getStructSize( $struct ) {
+		$size = 0;
+		foreach ( $struct as $type ) {
+			if ( is_array( $type ) ) {
+				list( , $fieldSize ) = $type;
+				$size += $fieldSize;
+			} else {
+				$size += $type;
+			}
+		}
+
+		return $size;
+	}
+
+	/**
+	 * Unpack a binary structure. This is like the built-in unpack() function
+	 * except nicer.
+	 *
+	 * @param string $string The binary data input
+	 *
+	 * @param array $struct An associative array giving structure members and their
+	 *    types. In the key is the field name. The value may be either an
+	 *    integer, in which case the field is a little-endian unsigned integer
+	 *    encoded in the given number of bytes, or an array, in which case the
+	 *    first element of the array is the type name, and the subsequent
+	 *    elements are type-dependent parameters. Only one such type is defined:
+	 *       - "string": The second array element gives the length of string.
+	 *          Not null terminated.
+	 *
+	 * @param int $offset The offset into the string at which to start unpacking.
+	 *
+	 * @throws MWException
+	 * @return array Unpacked associative array. Note that large integers in the input
+	 *    may be represented as floating point numbers in the return value, so
+	 *    the use of weak comparison is advised.
+	 */
+	function unpack( $string, $struct, $offset = 0 ) {
+		$size = $this->getStructSize( $struct );
+		if ( $offset + $size > strlen( $string ) ) {
+			$this->error( 'zip-bad', 'unpack() would run past the end of the supplied string' );
+		}
+
+		$data = [];
+		$pos = $offset;
+		foreach ( $struct as $key => $type ) {
+			if ( is_array( $type ) ) {
+				list( $typeName, $fieldSize ) = $type;
+				switch ( $typeName ) {
+					case 'string':
+						$data[$key] = substr( $string, $pos, $fieldSize );
+						$pos += $fieldSize;
+						break;
+					default:
+						throw new MWException( __METHOD__ . ": invalid type \"$typeName\"" );
+				}
+			} else {
+				// Unsigned little-endian integer
+				$length = intval( $type );
+
+				// Calculate the value. Use an algorithm which automatically
+				// upgrades the value to floating point if necessary.
+				$value = 0;
+				for ( $i = $length - 1; $i >= 0; $i-- ) {
+					$value *= 256;
+					$value += ord( $string[$pos + $i] );
+				}
+
+				// Throw an exception if there was loss of precision
+				if ( $value > pow( 2, 52 ) ) {
+					$this->error( 'zip-unsupported', 'number too large to be stored in a double. ' .
+						'This could happen if we tried to unpack a 64-bit structure ' .
+						'at an invalid location.' );
+				}
+				$data[$key] = $value;
+				$pos += $length;
+			}
+		}
+
+		return $data;
+	}
+
+	/**
+	 * Returns a bit from a given position in an integer value, converted to
+	 * boolean.
+	 *
+	 * @param int $value
+	 * @param int $bitIndex The index of the bit, where 0 is the LSB.
+	 * @return bool
+	 */
+	function testBit( $value, $bitIndex ) {
+		return (bool)( ( $value >> $bitIndex ) & 1 );
+	}
+
+	/**
+	 * Debugging helper function which dumps a string in hexdump -C format.
+	 * @param string $s
+	 */
+	function hexDump( $s ) {
+		$n = strlen( $s );
+		for ( $i = 0; $i < $n; $i += 16 ) {
+			printf( "%08X ", $i );
+			for ( $j = 0; $j < 16; $j++ ) {
+				print " ";
+				if ( $j == 8 ) {
+					print " ";
+				}
+				if ( $i + $j >= $n ) {
+					print "  ";
+				} else {
+					printf( "%02X", ord( $s[$i + $j] ) );
+				}
+			}
+
+			print "  |";
+			for ( $j = 0; $j < 16; $j++ ) {
+				if ( $i + $j >= $n ) {
+					print " ";
+				} elseif ( ctype_print( $s[$i + $j] ) ) {
+					print $s[$i + $j];
+				} else {
+					print '.';
+				}
+			}
+			print "|\n";
+		}
+	}
+}