On 2025-03-23 14:13, Herbert Xu wrote:
Hi Harald:
I'm working on making the export format of hash algorithms compatible
so that you can switch between implementations seamlessly.
I've got a question about the s390 hmac implementation. How does
the hardware tell if it's the first update (where the cv from the
param block contains undefined state) or not? Is it a bit in
s390_kmac_gr0 or is it the imbl?
Thanks,
Hi Herbert
that is the ikp bit in the s390_kmac_gr0 struct:
union s390_kmac_gr0 {
unsigned long reg;
struct {
unsigned long : 48;
unsigned long ikp : 1;
unsigned long iimp : 1;
unsigned long ccup : 1;
unsigned long : 6;
unsigned long fc : 7;
};
};
It needs to be initial 0 and the firmware sets it to 1 with
the inner key padding and the hashing done.
Holger's implementation in hmac_s390.c of the clear key hmac
holds this gr0 value as part of the running hash context:
struct s390_kmac_sha2_ctx {
u8 param[MAX_DIGEST_SIZE + MAX_IMBL_SIZE + MAX_BLOCK_SIZE];
union s390_kmac_gr0 gr0;
u8 buf[MAX_BLOCK_SIZE];
unsigned int buflen;
};
