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Legacy encryption key support for when KMS is on #1223

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Merged
pkarman merged 1 commit into from
Mar 15, 2017
Merged

Legacy encryption key support for when KMS is on #1223

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12 changes: 10 additions & 2 deletions app/services/encrypted_key_maker.rb
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Original file line number Diff line number Diff line change
@@ -1,6 +1,10 @@
class EncryptedKeyMaker
include Pii::Encodable

KEY_TYPE = {
KMS: 'KMSx',
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@zachmargolis zachmargolis Mar 15, 2017

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Since there's only one value in KEY_TYPE for now, should we just make this KMS_KEY_TYPE = 'KMSx'? Or is this part of the plan to refactor EncryptedKeyMaker to allow locally-encrypted keys too?

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@pkarman pkarman Mar 15, 2017

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the latter. we wanted to provide structure for future refactor.

}.freeze

# Creates an encrypted encryption key.
#
# @param user_access_key [UserAccessKey]
Expand Down Expand Up @@ -34,7 +38,7 @@ def unlock(user_access_key, encryption_key)
private

def unlock_key(user_access_key, encryption_key)
if FeatureManagement.use_kms?
if FeatureManagement.use_kms? && looks_like_kms?(user_access_key, encryption_key)
unlock_kms(user_access_key, encryption_key)
else
unlock_local(user_access_key, encryption_key)
Expand All @@ -51,7 +55,7 @@ def make_kms(user_access_key)
key_id: Figaro.env.aws_kms_key_id,
plaintext: user_access_key.random_r
).ciphertext_blob
build_user_access_key(user_access_key, encrypted_key)
build_user_access_key(user_access_key, KEY_TYPE[:KMS] + encrypted_key)
end

def unlock_kms(user_access_key, encryption_key)
Expand All @@ -72,6 +76,10 @@ def unlock_local(user_access_key, encryption_key)
user_access_key.unlock(encryptor.decrypt(ciphertext, Figaro.env.password_pepper))
end

def looks_like_kms?(user_access_key, encryption_key)
user_access_key.xor(decode(encryption_key)).start_with?(KEY_TYPE[:KMS])
end

def aws_client
@_aws_client ||= Aws::KMS::Client.new(region: Figaro.env.aws_region)
end
Expand Down
9 changes: 9 additions & 0 deletions spec/services/encrypted_key_maker_spec.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,15 @@

expect(subject.unlock(user_access_key, encryption_key)).to eq hash_E
end

it 'recognizes locally-encrypted legacy keys' do
allow(FeatureManagement).to receive(:use_kms?).and_return(false)
subject.make(user_access_key)
encryption_key = user_access_key.encryption_key

allow(FeatureManagement).to receive(:use_kms?).and_return(true)
expect(subject.unlock(user_access_key, encryption_key)).to eq hash_E
end
end
end
end
8 changes: 5 additions & 3 deletions spec/services/pii/nist_encryption_spec.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,8 @@
allow(FeatureManagement).to receive(:use_kms?).and_return(true)
end

let(:kms_prefix) { '{}cH' } # XOR of 'KMSx' and '0000'

describe 'password hashing' do
it 'creates two substrings Z1 and Z2 via scrypt of password and salt' do
# Generate and store a 128-bit salt S.
Expand Down Expand Up @@ -61,7 +63,7 @@
encrypted_key_maker = EncryptedKeyMaker.new
encrypted_key_maker.make(user_access_key)

expect(user_access_key.encrypted_d).to eq encrypted_D
expect(user_access_key.encrypted_d).to eq(kms_prefix + encrypted_D)
expect(user_access_key.hash_e).to eq hash_E
end
end
Expand Down Expand Up @@ -92,7 +94,7 @@

encrypted_D = Base64.strict_decode64(user.encryption_key)

expect(user.user_access_key.xor(ciphered_R)).to eq encrypted_D
expect(kms_prefix + user.user_access_key.xor(ciphered_R)).to eq(encrypted_D)
end
end

Expand Down Expand Up @@ -121,7 +123,7 @@
# encrypted_payload is an envelope that contains C and D.
encrypted_key, encrypted_C = open_envelope(encrypted_payload)

expect(Base64.strict_decode64(encrypted_key)).to eq encrypted_D
expect(Base64.strict_decode64(encrypted_key)).to eq(kms_prefix + encrypted_D)

# unroll encrypted_C to verify it was encrypted with hash_E
cipher = Pii::Cipher.new
Expand Down