spaces.php

aws/Aws/Crypto/AesDecryptingStream.php

@@ -0,0 +1,144 @@
+<?php
+namespace Aws\Crypto;
+
+use GuzzleHttp\Psr7\StreamDecoratorTrait;
+use \LogicException;
+use Psr\Http\Message\StreamInterface;
+use Aws\Crypto\Cipher\CipherMethod;
+
+/**
+ * @internal Represents a stream of data to be decrypted with passed cipher.
+ */
+class AesDecryptingStream implements AesStreamInterface
+{
+    const BLOCK_SIZE = 16; // 128 bits
+
+    use StreamDecoratorTrait;
+
+    /**
+     * @var string
+     */
+    private $buffer = '';
+
+    /**
+     * @var CipherMethod
+     */
+    private $cipherMethod;
+
+    /**
+     * @var string
+     */
+    private $key;
+
+    /**
+     * @var StreamInterface
+     */
+    private $stream;
+
+    /**
+     * @param StreamInterface $cipherText
+     * @param string $key
+     * @param CipherMethod $cipherMethod
+     */
+    public function __construct(
+        StreamInterface $cipherText,
+        $key,
+        CipherMethod $cipherMethod
+    ) {
+        $this->stream = $cipherText;
+        $this->key = $key;
+        $this->cipherMethod = clone $cipherMethod;
+    }
+
+    public function getOpenSslName()
+    {
+        return $this->cipherMethod->getOpenSslName();
+    }
+
+    public function getAesName()
+    {
+        return $this->cipherMethod->getAesName();
+    }
+
+    public function getCurrentIv()
+    {
+        return $this->cipherMethod->getCurrentIv();
+    }
+
+    public function getSize()
+    {
+        $plainTextSize = $this->stream->getSize();
+
+        if ($this->cipherMethod->requiresPadding()) {
+            // PKCS7 padding requires that between 1 and self::BLOCK_SIZE be
+            // added to the plaintext to make it an even number of blocks. The
+            // plaintext is between strlen($cipherText) - self::BLOCK_SIZE and
+            // strlen($cipherText) - 1
+            return null;
+        }
+
+        return $plainTextSize;
+    }
+
+    public function isWritable()
+    {
+        return false;
+    }
+
+    public function read($length)
+    {
+        if ($length > strlen($this->buffer)) {
+            $this->buffer .= $this->decryptBlock(
+                self::BLOCK_SIZE * ceil(($length - strlen($this->buffer)) / self::BLOCK_SIZE)
+            );
+        }
+
+        $data = substr($this->buffer, 0, $length);
+        $this->buffer = substr($this->buffer, $length);
+
+        return $data ? $data : '';
+    }
+
+    public function seek($offset, $whence = SEEK_SET)
+    {
+        if ($offset === 0 && $whence === SEEK_SET) {
+            $this->buffer = '';
+            $this->cipherMethod->seek(0, SEEK_SET);
+            $this->stream->seek(0, SEEK_SET);
+        } else {
+            throw new LogicException('AES encryption streams only support being'
+                . ' rewound, not arbitrary seeking.');
+        }
+    }
+
+    private function decryptBlock($length)
+    {
+        if ($this->stream->eof()) {
+            return '';
+        }
+
+        $cipherText = '';
+        do {
+            $cipherText .= $this->stream->read($length - strlen($cipherText));
+        } while (strlen($cipherText) < $length && !$this->stream->eof());
+
+        $options = OPENSSL_RAW_DATA;
+        if (!$this->stream->eof()
+            && $this->stream->getSize() !== $this->stream->tell()
+        ) {
+            $options |= OPENSSL_ZERO_PADDING;
+        }
+
+        $plaintext = openssl_decrypt(
+            $cipherText,
+            $this->cipherMethod->getOpenSslName(),
+            $this->key,
+            $options,
+            $this->cipherMethod->getCurrentIv()
+        );
+
+        $this->cipherMethod->update($cipherText);
+
+        return $plaintext;
+    }
+}