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<?php |
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/* |
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* This file is part of the PHP EcryptFS library. |
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* (c) 2017 by Dennis Birkholz |
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* All rights reserved. |
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* For the license to use this library, see the provided LICENSE file. |
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*/ |
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namespace Iqb\Ecryptfs; |
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/** |
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* Class to convert binary data to/from base256 to base64 with filename save alphabet. |
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* Used to create encrypted filenames. |
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* |
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* @author Dennis Birkholz <[email protected]> |
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*/ |
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final class BaseConverter |
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{ |
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const PORTABLE_FILENAME_CHARS = '-.0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'; |
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const FILENAME_REVERSE_MAPPING = [ |
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 7 */ |
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 15 */ |
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 23 */ |
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 31 */ |
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 39 */ |
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* 47 */ |
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0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, /* 55 */ |
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0x0A, 0x0B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* 63 */ |
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0x00, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, /* 71 */ |
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0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, /* 79 */ |
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0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, /* 87 */ |
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0x23, 0x24, 0x25, 0x00, 0x00, 0x00, 0x00, 0x00, /* 95 */ |
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0x00, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, /* 103 */ |
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0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, /* 111 */ |
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0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, /* 119 */ |
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0x3D, 0x3E, 0x3F, 0x00, 0x00, 0x00, 0x00, 0x00, /* 123 - 255 initialized to 0x00 */ |
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]; |
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/** |
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* Decode the base64 encoded string into a base256 binary string |
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* |
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* @param string $encoded |
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* @return string |
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*/ |
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public static function decode(string $encoded) : string |
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{ |
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36 |
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$srcSize = \strlen($encoded); |
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36 |
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$currentBitOffset = 0; |
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$dstByteOffset = 0; |
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$dst = []; |
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for ($srcByteOffset=0; $srcByteOffset<$srcSize; $srcByteOffset++) { |
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$byte = self::FILENAME_REVERSE_MAPPING[\ord($encoded[$srcByteOffset])]; |
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switch ($currentBitOffset) { |
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36 |
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case 0: |
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$dst[$dstByteOffset] = ($byte << 2); |
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$currentBitOffset = 6; |
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break; |
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case 6: |
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$dst[$dstByteOffset++] |= ($byte >> 4); |
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$dst[$dstByteOffset] = (($byte & 0xF) << 4); |
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$currentBitOffset = 4; |
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break; |
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case 4: |
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$dst[$dstByteOffset++] |= ($byte >> 2); |
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$dst[$dstByteOffset] = ($byte << 6); |
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$currentBitOffset = 2; |
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break; |
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case 2: |
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$dst[$dstByteOffset++] |= ($byte); |
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$currentBitOffset = 0; |
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break; |
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} |
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} |
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return \implode('', \array_map('\\chr', $dst)); |
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} |
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/** |
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* Encode a (base256) binary string into a base64 string (using the filename save alphabet) |
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* |
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* @param string $decoded |
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* @return string |
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*/ |
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public static function encode(string $decoded) : string |
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{ |
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$inputLength = \mb_strlen($decoded, '8bit'); |
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// Each encoded char holds only 6 bit of the original 8 bit |
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// so a block of 3 original chars results in 4 encoded chars. |
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// Pad the input with \0-bytes so string can be split in 3 char blocks. |
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if (($inputLength % 3) > 0) { |
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$padding = (3 - ($inputLength % 3)); |
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$decoded .= \str_repeat("\0", $padding); |
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$inputLength += $padding; |
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} |
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$encoded = ''; |
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for ($i=0; $i<$inputLength; $i+=3) { |
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$code1 = (\ord($decoded[$i]) >> 2) & 0x3F; |
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$code2 = ((\ord($decoded[$i]) << 4) & 0x30) | ((\ord($decoded[$i+1]) >> 4) & 0x0F); |
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$code3 = ((\ord($decoded[$i+1]) << 2) & 0x3C) | ((\ord($decoded[$i+2]) >> 6) & 0x03); |
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$code4 = \ord($decoded[$i+2]) & 0x3F; |
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$encoded .= self::PORTABLE_FILENAME_CHARS[$code1]; |
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$encoded .= self::PORTABLE_FILENAME_CHARS[$code2]; |
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$encoded .= self::PORTABLE_FILENAME_CHARS[$code3]; |
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$encoded .= self::PORTABLE_FILENAME_CHARS[$code4]; |
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} |
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return $encoded; |
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} |
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} |
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iqb /
ecryptfs
