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<?php |
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/** |
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* This file is part of the ocra-implementations package. |
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* |
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* More information: https://github.com/SURFnet/ocra-implementations/ |
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* |
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* @author Ivo Jansch <[email protected]> |
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* |
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* @license See the LICENSE file in the source distribution |
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*/ |
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/** |
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* This a PHP port of the example implementation of the |
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* OATH OCRA algorithm. |
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* Visit www.openauthentication.org for more information. |
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* |
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* @author Johan Rydell, PortWise (original Java) |
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* @author Ivo Jansch, Egeniq (PHP port) |
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*/ |
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class OCRA { |
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private function __construct() { |
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} |
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/** |
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* This method uses the hmac_hash function to provide the crypto |
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* algorithm. |
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* HMAC computes a Hashed Message Authentication Code with the |
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* crypto hash algorithm as a parameter. |
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* |
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* @param String crypto the crypto algorithm (sha1, sha256 or sha512) |
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* @param String keyBytes the bytes to use for the HMAC key |
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* @param String text the message or text to be authenticated. |
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* @throws Exception |
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*/ |
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private static function _hmac(string $crypto, string $keyBytes, string $text) : string |
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{ |
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$hash = hash_hmac($crypto, $text, $keyBytes); |
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if (false === $hash) { |
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throw new Exception("calculating hash_hmac failed"); |
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} |
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return $hash; |
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} |
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/** |
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* This method converts HEX string to Byte[] |
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* |
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* @param string $hex The hex string to decode |
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* @param int $maxBytes The maximum length of the resulting decoded string |
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* @param string $parameterName A descriptive name for the $hex parameter, used in exception error message |
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* @return String a string with the decoded raw bytes of $hex |
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* @throws InvalidArgumentException |
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* |
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* The length of the returned string will always be length($hex)/2 bytes |
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* Note that $maxBytes is the max length of the returned string, not the max number of hex digits in $hex |
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*/ |
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private static function _hexStr2Bytes(string $hex, int $maxBytes, string $parameterName) : string |
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{ |
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$len = strlen($hex); |
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if ( ($len !== 0) && (! ctype_xdigit($hex)) ) { |
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throw new InvalidArgumentException("Parameter '$parameterName' contains non hex digits"); |
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} |
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if ( $len % 2 !== 0 ) { |
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throw new InvalidArgumentException("Parameter '$parameterName' contains odd number of hex digits"); |
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} |
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if ( $len > $maxBytes * 2) { |
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throw new InvalidArgumentException("Parameter '$parameterName' too long"); |
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} |
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// hex2bin logs PHP warnings when $hex contains invalid characters or has uneven length. Because we |
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// check for these conditions above hex2bin() should always be silent |
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$res=hex2bin($hex); |
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if (false === $res) { |
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throw new InvalidArgumentException("Parameter '$parameterName' could not be decoded"); |
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} |
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return $res; |
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} |
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/** |
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* Calculate the OCRA (RFC 6287) response for the given set of parameters |
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* This implementation uses the same interface as the Java reference implementation from the RFC |
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* |
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* @param string $ocraSuite the OCRASuite |
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* @param string $key the shared OCRA secret, HEX encoded |
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* @param string $counter the counter (C), HEX encoded |
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* @param string $question the challenge question (Q), HEX encoded |
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* @param string $password the Hashed version of PIN/password (P), HEX encoded |
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* @param string $sessionInformation the session information (S), HEX encoded |
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* @param string $timeStamp the timestamp (T), HEX encoded |
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* |
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* @return string The Response, A numeric String in base 10 that includes number of digits specified in the OCRASuite |
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* @throws InvalidArgumentException|Exception InvalidArgumentException is thrown when a HEX encoded parameter does not contain hex or when it exceeds its maximum length |
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* |
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* Note: The OCRA secret and the parameters C, Q, P, S and T must be provided as HEX encoded strings. |
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* How each parameter must be encoded is specified in the RFC |
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* |
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* In addition to the RFC reference implementation this implementation supports using "-S" in OCRASuite as an |
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* alternative to "-S064" |
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*/ |
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static function generateOCRA(string $ocraSuite, |
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string $key, |
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string $counter, |
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string $question, |
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string $password, |
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string $sessionInformation, |
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string $timeStamp) : string |
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{ |
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$codeDigits = 0; |
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$crypto = ""; |
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$result = null; |
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$ocraSuiteLength = strlen($ocraSuite); |
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$counterLength = 0; |
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$questionLength = 0; |
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$passwordLength = 0; |
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$sessionInformationLength = 0; |
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$timeStampLength = 0; |
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// How many digits should we return |
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$components = explode(":", $ocraSuite); |
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$cryptoFunction = $components[1]; |
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$dataInput = strtolower($components[2]); // lower here so we can do case insensitive comparisons |
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if(stripos($cryptoFunction, "sha1")!==false) |
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$crypto = "sha1"; |
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if(stripos($cryptoFunction, "sha256")!==false) |
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$crypto = "sha256"; |
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if(stripos($cryptoFunction, "sha512")!==false) |
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$crypto = "sha512"; |
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$codeDigits = substr($cryptoFunction, strrpos($cryptoFunction, "-")+1); |
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// The size of the byte array message to be encrypted |
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// Counter |
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if($dataInput[0] == "c" ) { |
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// Fix the length of the HEX string |
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while(strlen($counter) < 16) |
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$counter = "0" . $counter; |
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$counterLength=8; |
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} |
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// Question |
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if($dataInput[0] == "q" || |
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stripos($dataInput, "-q")!==false) { |
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while(strlen($question) < 256) |
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$question = $question . "0"; |
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$questionLength=128; |
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} |
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// Password |
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if(stripos($dataInput, "psha1")!==false) { |
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while(strlen($password) < 40) |
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$password = "0" . $password; |
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$passwordLength=20; |
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} |
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if(stripos($dataInput, "psha256")!==false) { |
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while(strlen($password) < 64) |
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$password = "0" . $password; |
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$passwordLength=32; |
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} |
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if(stripos($dataInput, "psha512")!==false) { |
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while(strlen($password) < 128) |
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$password = "0" . $password; |
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$passwordLength=64; |
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} |
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// sessionInformation |
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if(stripos($dataInput, "s064") !==false) { |
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while(strlen($sessionInformation) < 128) |
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$sessionInformation = "0" . $sessionInformation; |
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$sessionInformationLength=64; |
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} else if(stripos($dataInput, "s128") !==false) { |
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while(strlen($sessionInformation) < 256) |
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$sessionInformation = "0" . $sessionInformation; |
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$sessionInformationLength=128; |
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} else if(stripos($dataInput, "s256") !==false) { |
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while(strlen($sessionInformation) < 512) |
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$sessionInformation = "0" . $sessionInformation; |
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$sessionInformationLength=256; |
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} else if(stripos($dataInput, "s512") !==false) { |
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while(strlen($sessionInformation) < 128) |
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$sessionInformation = "0" . $sessionInformation; |
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$sessionInformationLength=64; |
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} else if (stripos($dataInput, "-s") !== false ) { |
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// deviation from spec. Officially 's' without a length indicator is not in the reference implementation. |
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// RFC is ambigious. However we have supported this in Tiqr since day 1, so we continue to support it. |
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// See the format of the datainput below. "[]" denotes optional. |
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// Because Q is mandatory, s will always be preceded by the separator "-". Matching "-s" is required |
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// to prevent matching the "s" in the password input e.g. "psha1". |
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// [C] | QFxx | [PH | Snnn | TG] : Challenge-Response computation |
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// [C] | QFxx | [PH | TG] : Plain Signature computation |
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while(strlen($sessionInformation) < 128) |
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$sessionInformation = "0" . $sessionInformation; |
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$sessionInformationLength=64; |
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} |
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// TimeStamp |
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if($dataInput[0] == "t" || |
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stripos($dataInput, "-t") !== false) { |
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while(strlen($timeStamp) < 16) |
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$timeStamp = "0" . $timeStamp; |
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$timeStampLength=8; |
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} |
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// Put the bytes of "ocraSuite" parameters into the message |
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$msg = array_fill(0,$ocraSuiteLength+$counterLength+$questionLength+$passwordLength+$sessionInformationLength+$timeStampLength+1, 0); |
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for($i=0;$i<strlen($ocraSuite);$i++) { |
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$msg[$i] = $ocraSuite[$i]; |
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} |
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// Delimiter |
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$msg[strlen($ocraSuite)] = "\0"; |
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// Put the bytes of "Counter" to the message |
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// Input is HEX encoded |
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if($counterLength > 0 ) { |
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$bArray = self::_hexStr2Bytes($counter, $counterLength, 'counter'); |
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for ($i=0;$i<strlen($bArray);$i++) { |
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$msg [$i + $ocraSuiteLength + 1] = $bArray[$i]; |
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} |
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} |
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// Put the bytes of "question" to the message |
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// Input is text encoded |
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if($questionLength > 0 ) { |
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$bArray = self::_hexStr2Bytes($question, $questionLength, 'question'); |
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for ($i=0;$i<strlen($bArray);$i++) { |
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$msg [$i + $ocraSuiteLength + 1 + $counterLength] = $bArray[$i]; |
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} |
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} |
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// Put the bytes of "password" to the message |
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// Input is HEX encoded |
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if($passwordLength > 0){ |
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$bArray = self::_hexStr2Bytes($password, $passwordLength, 'password'); |
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for ($i=0;$i<strlen($bArray);$i++) { |
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$msg [$i + $ocraSuiteLength + 1 + $counterLength + $questionLength] = $bArray[$i]; |
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} |
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} |
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// Put the bytes of "sessionInformation" to the message |
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// Input is HEX encoded |
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if($sessionInformationLength > 0 ){ |
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$bArray = self::_hexStr2Bytes($sessionInformation, $sessionInformationLength, 'sessionInformation'); |
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for ($i=0;$i<strlen($bArray);$i++) { |
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$msg [$i + $ocraSuiteLength + 1 + $counterLength + $questionLength + $passwordLength] = $bArray[$i]; |
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} |
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} |
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// Put the bytes of "time" to the message |
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// Input is HEX encoded value of minutes |
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if($timeStampLength > 0){ |
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$bArray = self::_hexStr2Bytes($timeStamp, $timeStampLength, 'timeStamp'); |
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for ($i=0;$i<strlen($bArray);$i++) { |
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$msg [$i + $ocraSuiteLength + 1 + $counterLength + $questionLength + $passwordLength + $sessionInformationLength] = $bArray[$i]; |
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} |
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} |
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$byteKey = self::_hexStr2Bytes($key, strlen($key)/2, 'key'); |
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$msg = implode("", $msg); |
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$hash = self::_hmac($crypto, $byteKey, $msg); |
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$result = self::_oath_truncate($hash, $codeDigits); |
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return $result; |
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} |
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/** |
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* Implementation of the Truncate function from RFC4226 |
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* Truncate a hex encoded (hash) result to a string of digital digits of $length |
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* |
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* @param string $hash hex encoded (hash) value to truncate. Minimum length is 20 bytes (i.e. a string of 40 hex digits) |
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* @param int $length number of decimal digits to truncate to |
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* @return string of $length digits |
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*/ |
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static function _oath_truncate(string $hash, int $length = 6) : string |
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{ |
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// Convert to dec |
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foreach(str_split($hash,2) as $hex) |
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{ |
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$hmac_result[]=hexdec($hex); |
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} |
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// Find offset |
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$offset = $hmac_result[count($hmac_result) - 1] & 0xf; |
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$v = strval( |
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(($hmac_result[$offset+0] & 0x7f) << 24 ) | |
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(($hmac_result[$offset+1] & 0xff) << 16 ) | |
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(($hmac_result[$offset+2] & 0xff) << 8 ) | |
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($hmac_result[$offset+3] & 0xff) |
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); |
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// Prefix truncated string with 0's to ensure it always has the required length |
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$v=str_pad($v, $length, "0", STR_PAD_LEFT); |
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$v = substr($v, strlen($v) - $length); |
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return $v; |
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} |
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} |
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Adding explicit visibility (
private
,protected
, orpublic
) is generally recommend to communicate to other developers how, and from where this method is intended to be used.