Python-解密S3图像文件，用CSE KMS进行加密

Question

是否有一种方法可以在Python中解密JPG或PNG文件，该文件是使用Java加密的CSE KMS -AmazonS3EccryptionClient并存储在S3中？它看起来像boto3和AWS Ecryption客户端仅支持密码文本，而不支持文件。

我尝试了以下代码，但失败了，

def get_decrypted_stream(s3_object):
  region_name = 'us-east-1'
  encryptedImageBytes = s3_object.get()['Body'].read() 
  print("Decoded file : {}".format(encryptedImageBytes))
  client = boto3.client('kms', region_name=region_name)
  response = client.decrypt( CiphertextBlob=encryptedImageBytes)
  data = meta[u'Plaintext']
  return io.BytesIO(data)

错误：

它在" client.decrypt（ciphertextblob = encryptedImage）"上失败，{" errirormessage"："调用解密操作时发生错误（413）：http content Length：http content Lengume超过200000 bytes bytes。"，}

参考：https://docs.aws.amazon.com/kms/latest/apieferference/api_decrypt.html https://github.com/aws/aws-aws-eccryption-sdk-python/https://docs.aws.aws.amazon.com/cryption-sdk/latest/developer-guide/python-example-code.html https://aws-encryption-sdk-python.readthedocs.io/en/latest/

Answer 1

根据您共享的文档，Encrypt和Decrypt API仅限于4K的有效载荷最大值：https：//docs.aws.aws.amazon.com/kms/kms/latest/latest/apireference/api_encrypt。html

使用KMS键编码文件时，理念是生成一个符号密钥，用Symetric键编码有效负载，用KMMS encrypt API对Symetric密钥进行编码，并将隐脚的Symetric Key存储在信封中，作为元 - ---例如，S3上的数据。

这是用于S3文件加密的代码示例：

    #
    # Generate a Data Key (encoded with my Master Key in KMS)
    #
    key = kms.generate_data_key(KeyId=MASTER_KEY_ARN,KeySpec='AES_256')
    keyPlain  = key['Plaintext']
    keyCipher = key['CiphertextBlob']
    #
    # Encode a file with the data key
    #
    print ("Initializing encryption engine")
    iv = ''.join(chr(random.randint(0, 0xFF)) for i in range(16))
    chunksize = 64*1024
    encryptor = AES.new(keyPlain, AES.MODE_CBC, iv)
    print ("KMS Plain text key = %s " % base64.b64encode(keyPlain))
    print ("KMS Encrypted key  = %s " % base64.b64encode(keyCipher))
    in_filename = os.path.join(DIRECTORY, FILENAME)
    out_filename = in_filename + '.enc'
    filesize = os.path.getsize(in_filename)
    print ("Encrypting file")
    with open(in_filename, 'rb') as infile:
        with open(out_filename, 'wb') as outfile:
            outfile.write(struct.pack('<Q', filesize))
            outfile.write(iv)
            chunk = infile.read(chunksize)
            while len(chunk) != 0:
                if len(chunk) % 16 != 0:
                    chunk += ' ' * (16 - len(chunk) % 16)
                outfile.write(encryptor.encrypt(chunk))
                chunk = infile.read(chunksize)
    #
    # Store encrypted file on S3
    # Encrypted Key will be stored as meta data
    #
    print ("Storing encrypted file on S3")
    metadata = {
        "key" : base64.b64encode(keyCipher)
    }
    #client = boto3.client('s3', 'us-west-2')
    s3 = session.client('s3')
    transfer = S3Transfer(s3)
    transfer.upload_file(out_filename, S3_BUCKET, out_filename, extra_args={"Metadata" : metadata})
    os.remove(out_filename)

和解密的示例代码：

    #
    # Download Encrypted File and it's metadata
    #
    print ("Download file and meta data from S3")
    transfer.download_file(S3_BUCKET, out_filename, out_filename)
    #retrieve meta data
    import boto3
    s3 = boto3.resource('s3')
    object = s3.Object(S3_BUCKET, out_filename)
    #print object.metadata
    keyCipher = base64.b64decode(object.metadata['key'])
    #decrypt encrypted key
    print ("Decrypt ciphered key")
    key = kms.decrypt(CiphertextBlob=keyCipher)
    keyPlain = key['Plaintext']
    print ("KMS Plain text key = %s " % base64.b64encode(keyPlain))
    print ("KMS Encrypted key  = %s " % base64.b64encode(keyCipher))
    #
    # Decrypt the file
    #
    print("Decrypt the file")
    in_filename = out_filename
    out_filename = in_filename + '.jpg'
    filesize = os.path.getsize(in_filename)
    with open(in_filename, 'rb') as infile:
        origsize = struct.unpack('<Q', infile.read(struct.calcsize('Q')))[0]
        iv = infile.read(16)
        decryptor = AES.new(keyPlain, AES.MODE_CBC, iv)
        with open(out_filename, 'wb') as outfile:
            chunk = infile.read(chunksize)
            while len(chunk) != 0:
                outfile.write(decryptor.decrypt(chunk))
                chunk = infile.read(chunksize)
            outfile.truncate(origsize)