Class: Aws::S3::EncryptionV3::KmsCipherProvider Private

Inherits:
Object
  • Object
show all
Defined in:
lib/aws-sdk-s3/encryptionV3/kms_cipher_provider.rb

This class is part of a private API. You should avoid using this class if possible, as it may be removed or be changed in the future.

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ KmsCipherProvider

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns a new instance of KmsCipherProvider.



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# File 'lib/aws-sdk-s3/encryptionV3/kms_cipher_provider.rb', line 10

def initialize(options = {})
  @kms_key_id = validate_kms_key(options[:kms_key_id])
  @kms_client = options[:kms_client]
  @key_wrap_schema = validate_key_wrap(
    options[:key_wrap_schema]
  )
  @content_encryption_schema = Utils.validate_cek(
    options[:content_encryption_schema]
  )
end

Instance Method Details

#decryption_cipher(envelope, options = {}) ⇒ Cipher

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns Given an encryption envelope, returns a decryption cipher.

Returns:

  • (Cipher) —

    Given an encryption envelope, returns a decryption cipher.



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# File 'lib/aws-sdk-s3/encryptionV3/kms_cipher_provider.rb', line 51

def decryption_cipher(envelope, options = {})
  case envelope['x-amz-w']
  when '12'
    cek_alg = envelope['x-amz-c']
    encryption_context =
      if !envelope['x-amz-t'].nil?
        Json.load(envelope['x-amz-t'])
      else
        ##= ../specification/s3-encryption/data-format/content-metadata.md#v3-only
        ##% If the mapkey x-amz-t is not present, the default Material Description value MUST be set to an empty map (`{}`).
        {}
      end
    ##= ../specification/s3-encryption/data-format/content-metadata.md#v3-only
    ##% - The wrapping algorithm value "12" MUST be translated to kms+context upon retrieval, and vice versa on write.
    raise Errors::CEKAlgMismatchError if cek_alg != encryption_context['aws:x-amz-cek-alg']

    if encryption_context != build_encryption_context(cek_alg, options)
      raise Errors::DecryptionError, 'Value of encryption context from'\
        ' envelope does not match the provided encryption context'
    end
  when '02'
    raise ArgumentError, 'Key mismatch - Client is configured' \
            ' with a KMS key and the x-amz-wrap-alg is AES/GCM.'
  when '22'
    raise ArgumentError, 'Key mismatch - Client is configured' \
            ' with a KMS key and the x-amz-wrap-alg is RSA-OAEP-SHA1.'
  when nil
    raise ArgumentError, 'Plaintext passthrough not supported'
  else
    # assert !envelope['x-amz-w'].nil?
    # because of the when above
    raise ArgumentError, 'Unsupported wrapping algorithm: ' \
        "#{envelope['x-amz-w']}"
  end

  any_cmk_mode = options[:kms_allow_decrypt_with_any_cmk]
  decrypt_options = {
    ciphertext_blob: decode64(envelope['x-amz-3']),
    encryption_context: encryption_context
  }
  decrypt_options[:key_id] = @kms_key_id unless any_cmk_mode

  data_key = Aws::Plugins::UserAgent.metric('S3_CRYPTO_V3') do
    @kms_client.decrypt(decrypt_options).plaintext
  end

  message_id = decode64(envelope['x-amz-i'])
  commitment_key = decode64(envelope['x-amz-d'])

  Utils.derive_alg_aes_256_gcm_hkdf_sha512_commit_key_cipher(data_key, message_id, commitment_key)
end

#encryption_cipher(options = {}) ⇒ Array<Hash,Cipher>

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns Creates and returns a new encryption envelope and encryption cipher.

Returns:

  • (Array<Hash,Cipher>) —

    Creates and returns a new encryption envelope and encryption cipher.



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# File 'lib/aws-sdk-s3/encryptionV3/kms_cipher_provider.rb', line 23

def encryption_cipher(options = {})
  validate_key_for_encryption
  encryption_context = build_encryption_context(@content_encryption_schema, options)
  key_data = Aws::Plugins::UserAgent.metric('S3_CRYPTO_V3') do
    @kms_client.generate_data_key(
      key_id: @kms_key_id,
      encryption_context: encryption_context,
      key_spec: 'AES_256'
    )
  end
  cipher, message_id, commitment_key = Utils.generate_alg_aes_256_gcm_hkdf_sha512_commit_key_cipher(key_data.plaintext)
  ##= ../specification/s3-encryption/data-format/content-metadata.md#algorithm-suite-and-message-format-version-compatibility
  ##% Objects encrypted with ALG_AES_256_GCM_HKDF_SHA512_COMMIT_KEY MUST use the V3 message format version only.
  envelope = {
    'x-amz-3' => encode64(key_data.ciphertext_blob),
    'x-amz-c' => @content_encryption_schema,
    'x-amz-w' => @key_wrap_schema,
    'x-amz-d' => encode64(commitment_key),
    'x-amz-i' => encode64(message_id),
    ##= ../specification/s3-encryption/data-format/content-metadata.md#v3-only
    ##% The Encryption Context value MUST be used for wrapping algorithm `kms+context` or `12`.
    'x-amz-t' => Json.dump(encryption_context)
  }
  [envelope, cipher]
end