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<?php |
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namespace Bunq\Middleware; |
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use Bunq\Certificate\Certificate; |
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use Psr\Http\Message\ResponseInterface; |
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final class ResponseSignatureMiddleware |
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{ |
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const SIGNATURE_ALGORITHM = OPENSSL_ALGO_SHA256; |
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const VERIFY_IS_VALID = 1; |
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const VERIFY_IS_INVALID = 0; |
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const VERIFY_IS_ERROR = -1; |
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/** |
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* @var Certificate |
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*/ |
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private $publicKey; |
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/** |
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* @param Certificate $publicKey |
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*/ |
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public function __construct(Certificate $publicKey) |
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{ |
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$this->publicKey = $publicKey; |
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} |
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/** |
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* @param ResponseInterface $response |
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* |
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* @return ResponseInterface |
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* @throws \Exception |
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*/ |
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public function __invoke(ResponseInterface $response) |
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{ |
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$header = $response->getHeader('X-Bunq-Server-Signature'); |
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if (!isset($header[0])) { |
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return $response; |
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} |
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$decodedServerSignature = base64_decode($header[0]); |
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$signatureData = $this->createSignatureDataFromHeaders($response); |
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$verify = openssl_verify( |
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$signatureData, |
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$decodedServerSignature, |
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(string)$this->publicKey, |
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self::SIGNATURE_ALGORITHM |
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); |
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if ($verify !== self::VERIFY_IS_VALID) { |
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throw new \Exception('Server signature does not match response'); |
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} |
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return $response; |
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} |
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/** |
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* @param ResponseInterface $response |
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* |
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* @return string |
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*/ |
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private function createSignatureDataFromHeaders(ResponseInterface $response) |
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{ |
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$signatureData = $response->getStatusCode(); |
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$signatureData .= $this->convertHeadersToSignatureData($response); |
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$signatureData .= "\n\n"; |
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$signatureData .= (string)$response->getBody(); |
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return $signatureData; |
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} |
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/** |
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* @param ResponseInterface $response |
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* |
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* @return string |
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*/ |
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private function convertHeadersToSignatureData(ResponseInterface $response) |
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{ |
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$headers = $response->getHeaders(); |
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ksort($headers); |
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$signatureData = ''; |
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foreach ($headers as $header => $values) { |
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// Skip the server signature itself |
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if ($header === 'X-Bunq-Server-Signature') { |
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continue; |
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} |
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// Skip all headers that are not X-Bunq- |
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if (substr($header, 0, 7) !== 'X-Bunq-') { |
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continue; |
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} |
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// Add all header data to verify signature |
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foreach ($values as $value) { |
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$signatureData .= PHP_EOL . $header . ': ' . $value; |
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} |
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} |
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return $signatureData; |
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} |
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} |
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verschoof /
bunq-api
