Hi Herbert, Eric, key derivation functions behave like a random number generator requiring a seed and can generate arbitrarily-sized bit sequences. As KDFs wrap ciphers, the first patch adds template support for the RNG part of the kernel crypto API. This allows the KDFs to be implemented as templates. The patches two through five add different KDFs. The immediate use in the kernel are: - SP800-108: security/keys/dh.c - HKDF: As Eric Biggers outlined, he wants to use HKDF for Ext4 FBE Other areas of the kernel implement KDFs which should be migrated to the common code base offered with this patch. The last patch adds the KDF invocation to tcrypt to allow an immediate test invocation of the KDFs which is at least needed for FIPS 140-2 compliance where the tcrypt module is insmod'ed during boot time to trigger the self tests. Eric, considering your request for supporting parallel use of HKDF, I instantiate the HMAC twice: once for the extract and once for the expand phase. The idea is that an extract operation does not collide too much with the expand operation (when using one instance of HMAC, the extract phase would invoke setkey with the salt and thus affect the expand phase). Though, the final extract phase setkey call with the PRK is non-atomic (at least in the software HMAC implementation). Thus, the caller would need to guarantee to invoke the extract phase while no expand phase operation is performed. So, maintaining two HMAC instances is not really required after all. What is your take on that? Stephan Mueller (6): crypto: add template handling for RNGs crypto: kdf - SP800-108 Key Derivation Function crypto: kdf - add known answer tests crypto: hkdf - RFC5869 Key Derivation Function crypto: hkdf - add known answer tests crypto: tcrypt - add KDF test invocation crypto/Kconfig | 13 + crypto/Makefile | 2 + crypto/hkdf.c | 290 ++++++++++++++++++++ crypto/kdf.c | 492 ++++++++++++++++++++++++++++++++++ crypto/rng.c | 44 +++ crypto/tcrypt.c | 8 + crypto/testmgr.c | 258 ++++++++++++++++++ crypto/testmgr.h | 225 ++++++++++++++++ include/crypto/internal/rng.h | 26 ++ 9 files changed, 1358 insertions(+) create mode 100644 crypto/hkdf.c create mode 100644 crypto/kdf.c -- 2.20.1
