amazon_api.php

<?php

class AwsV4 {

private $accessKey = null;
private $secretKey = null;
private $path = null;
private $regionName = null;
private $serviceName = null;
private $httpMethodName = null;
private $queryParametes = array ();
private $awsHeaders = array ();
private $payload = "";

private $HMACAlgorithm = "AWS4-HMAC-SHA256";
private $aws4Request = "aws4_request";
private $strSignedHeader = null;
private $xAmzDate = null;
private $currentDate = null;

public function __construct($accessKey, $secretKey) {
    $this->accessKey = $accessKey;
    $this->secretKey = $secretKey;
    $this->xAmzDate = $this->getTimeStamp ();
    $this->currentDate = $this->getDate ();
}

function setPath($path) {
    $this->path = $path;
}

function setServiceName($serviceName) {
    $this->serviceName = $serviceName;
}

function setRegionName($regionName) {
    $this->regionName = $regionName;
}

function setPayload($payload) {
    $this->payload = $payload;
}

function setRequestMethod($method) {
    $this->httpMethodName = $method;
}

function addHeader($headerName, $headerValue) {
    $this->awsHeaders [$headerName] = $headerValue;
}

private function prepareCanonicalRequest() {
    $canonicalURL = "";
    $canonicalURL .= $this->httpMethodName . "\n";
    $canonicalURL .= $this->path . "\n" . "\n";
    $signedHeaders = '';
    foreach ( $this->awsHeaders as $key => $value ) {
        $signedHeaders .= $key . ";";
        $canonicalURL .= $key . ":" . $value . "\n";
    }
    $canonicalURL .= "\n";
    $this->strSignedHeader = substr ( $signedHeaders, 0, - 1 );
    $canonicalURL .= $this->strSignedHeader . "\n";
    $canonicalURL .= $this->generateHex ( $this->payload );
    return $canonicalURL;
}

private function prepareStringToSign($canonicalURL) {
    $stringToSign = '';
    $stringToSign .= $this->HMACAlgorithm . "\n";
    $stringToSign .= $this->xAmzDate . "\n";
    $stringToSign .= $this->currentDate . "/" . $this->regionName . "/" . $this->serviceName . "/" . $this->aws4Request . "\n";
    $stringToSign .= $this->generateHex ( $canonicalURL );
    return $stringToSign;
}

private function calculateSignature($stringToSign) {
    $signatureKey = $this->getSignatureKey ( $this->secretKey, $this->currentDate, $this->regionName, $this->serviceName );
    $signature = hash_hmac ( "sha256", $stringToSign, $signatureKey, true );
    $strHexSignature = strtolower ( bin2hex ( $signature ) );
    return $strHexSignature;
}

public function getHeaders() {
    $this->awsHeaders ['x-amz-date'] = $this->xAmzDate;
    ksort ( $this->awsHeaders );

    // Step 1: CREATE A CANONICAL REQUEST
    $canonicalURL = $this->prepareCanonicalRequest ();

    // Step 2: CREATE THE STRING TO SIGN
    $stringToSign = $this->prepareStringToSign ( $canonicalURL );

    // Step 3: CALCULATE THE SIGNATURE
    $signature = $this->calculateSignature ( $stringToSign );

    // Step 4: CALCULATE AUTHORIZATION HEADER
    if ($signature) {
        $this->awsHeaders ['Authorization'] = $this->buildAuthorizationString ( $signature );
        return $this->awsHeaders;
    }
}

private function buildAuthorizationString($strSignature) {
    return $this->HMACAlgorithm . " " . "Credential=" . $this->accessKey . "/" . $this->getDate () . "/" . $this->regionName . "/" . $this->serviceName . "/" . $this->aws4Request . "," . "SignedHeaders=" . $this->strSignedHeader . "," . "Signature=" . $strSignature;
}

private function generateHex($data) {
    return strtolower ( bin2hex ( hash ( "sha256", $data, true ) ) );
}

private function getSignatureKey($key, $date, $regionName, $serviceName) {
    $kSecret = "AWS4" . $key;
    $kDate = hash_hmac ( "sha256", $date, $kSecret, true );
    $kRegion = hash_hmac ( "sha256", $regionName, $kDate, true );
    $kService = hash_hmac ( "sha256", $serviceName, $kRegion, true );
    $kSigning = hash_hmac ( "sha256", $this->aws4Request, $kService, true );

    return $kSigning;
}

private function getTimeStamp() {
    return gmdate ( "Ymd\THis\Z" );
}

private function getDate() {
    return gmdate ( "Ymd" );
}
}
?>