* EaR: Implement Key Check Value semantics
Description
Key Check Value (KCV) is a checksum of cryptographic encryption key
used to validate encryption keys's integrity. FDB Encryption at-rest
relies on external KMS to supply encryption keys.
Patch proposes following major changes:
1. Implement Sha256 based KCV implementation to protect against
'baseCipher' corruption in two possible scenarios:
a) potential corruption external to FDB
b) potential corruption within FDB processes.
2. Scheme persists computed KCV token in block encryption header,
which then gets validated as part of header validation during
decryption.
3. FDB Encryption key derivation uses HMAC_SHA256 digest generation
scheme, which allows max 64 bytes of 'cipher buffer', patch add
required check to ensure 'baseCipher' length are within bounds.
OpenSSL HMAC underlying call ignores extra length if supplied, however,
it weakens the security guarantees, hence, disallowed.
Testing
devRunCorrectness - multiple 500K runs
Valgrind & Asan - BlobCipherUnit, RESTKMSUnit, BlobGranuleCorrectness*,
EncryptionOps, EncryptKeyProxyTest
* Upgrade AES 128 GCM -> AES 256, StreamCipher code refactor
Major changes proposed are:
1. Refactor StreamCipher code to enable instantiation of
multiple encryption keys. However, code still retains
a globalEncryption key semantics used in Backup file
encryption usecase.
2. Enhance StreamCipher to provide HMAC signature digest
generation. Further, the class implements HMAC encryption
key derivation function.
3. Upgrade StreamCipher to use AES 256 GCM mode from currently
supported AES 128 GCM mode.
Note: The code changes the encryption key size, however, the
feature is NOT currently in use, hence, should be OK.
3. Add EncryptionOps validation and benchmark toml supported
workload, it does the following:
a. Allow user to configure encrypt-decrypt of a fixed size
buffer or variable size buffer [100, 512K]
b. Allow user to configure number of interactions of the runs,
in each iteration: generate random data, derive an encryption
key using HMAC SHA256 method, encrypt data and
then decrypt data. It collects following metrics:
i) time taken to derive encryption key.
ii) time taken to encrypt the buffer.
iii) time taken to decrypt the buffer.
iv) total bytes encrypted and/or decrypted
c. Along with stats it basic basic validations on the encrypted
and decrypted buffer
d. On completion for test, records the above mentioned metrics
in trace files.
Ata E Husain Bohra