Class: Aws::S3::EncryptionV2::KmsCipherProvider Private

Inherits:
Object
  • Object
show all
Defined in:
lib/aws-sdk-s3/encryptionV2/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.



11
12
13
14
15
16
17
18
19
20
 
# File 'lib/aws-sdk-s3/encryptionV2/kms_cipher_provider.rb', line 11

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 = 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.



48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
 
# File 'lib/aws-sdk-s3/encryptionV2/kms_cipher_provider.rb', line 48

def decryption_cipher(envelope, options = {})
  encryption_context = Json.load(envelope['x-amz-matdesc'])
  cek_alg = envelope['x-amz-cek-alg']

  case envelope['x-amz-wrap-alg']
  when 'kms'
    unless options[:security_profile] == :v2_and_legacy
      raise Errors::LegacyDecryptionError
    end
  when 'kms+context'
    if cek_alg != encryption_context['aws:x-amz-cek-alg']
      raise Errors::CEKAlgMismatchError
    end

    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 'AES/GCM'
    raise ArgumentError, 'Key mismatch - Client is configured' \
            ' with a KMS key and the x-amz-wrap-alg is AES/GCM.'
  when 'RSA-OAEP-SHA1'
    raise ArgumentError, 'Key mismatch - Client is configured' \
            ' with a KMS key and the x-amz-wrap-alg is RSA-OAEP-SHA1.'
  else
    raise ArgumentError, 'Unsupported wrap-alg: ' \
        "#{envelope['x-amz-wrap-alg']}"
  end

  any_cmk_mode = false || options[:kms_allow_decrypt_with_any_cmk]
  decrypt_options = {
    ciphertext_blob: decode64(envelope['x-amz-key-v2']),
    encryption_context: encryption_context
  }
  unless any_cmk_mode
    decrypt_options[:key_id] = @kms_key_id
  end

  key = @kms_client.decrypt(decrypt_options).plaintext
  iv = decode64(envelope['x-amz-iv'])
  block_mode =
    case cek_alg
    when 'AES/CBC/PKCS5Padding'
      :CBC
    when 'AES/CBC/PKCS7Padding'
      :CBC
    when 'AES/GCM/NoPadding'
      :GCM
    else
      type = envelope['x-amz-cek-alg'].inspect
      msg = "unsupported content encrypting key (cek) format: #{type}"
      raise Errors::DecryptionError, msg
    end
  Utils.aes_decryption_cipher(block_mode, key, iv)
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.



24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
 
# File 'lib/aws-sdk-s3/encryptionV2/kms_cipher_provider.rb', line 24

def encryption_cipher(options = {})
  validate_key_for_encryption
  encryption_context = build_encryption_context(@content_encryption_schema, options)
  key_data = @kms_client.generate_data_key(
    key_id: @kms_key_id,
    encryption_context: encryption_context,
    key_spec: 'AES_256'
  )
  cipher = Utils.aes_encryption_cipher(:GCM)
  cipher.key = key_data.plaintext
  envelope = {
    'x-amz-key-v2' => encode64(key_data.ciphertext_blob),
    'x-amz-iv' => encode64(cipher.iv = cipher.random_iv),
    'x-amz-cek-alg' => @content_encryption_schema,
    'x-amz-tag-len' => (AES_GCM_TAG_LEN_BYTES * 8).to_s,
    'x-amz-wrap-alg' => @key_wrap_schema,
    'x-amz-matdesc' => Json.dump(encryption_context)
  }
  cipher.auth_data = '' # auth_data must be set after key and iv
  [envelope, cipher]
end