65816-crypto/hmacimpl.h
2023-11-29 20:03:37 -06:00

88 lines
3.2 KiB
C

/*
* Copyright (c) 2023 Stephen Heumann
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This file is a template for computing HMACs using the hash functions
* from lib65816hash. It is #included from the files implementing the
* hash functions, with HASH_ALG defined to the name of the hash function.
*/
#define join(a,b) a##b
#define concat(a,b) join(a,b)
#define join3(a,b,c) a##b##c
#define concat3(a,b,c) join3(a,b,c)
#define hash_init concat(HASH_ALG,_init)
#define hash_update concat(HASH_ALG,_update)
#define hash_finalize concat(HASH_ALG,_finalize)
#define hmac_init concat3(hmac_,HASH_ALG,_init)
#define hmac_compute concat3(hmac_,HASH_ALG,_compute)
#define hmac_context concat3(hmac_,HASH_ALG,_context)
void hmac_init(struct hmac_context *context,
const unsigned char *key,
unsigned long key_length)
{
#define BLOCK_SIZE sizeof(context->u[0].ctx.block)
#define HASH_SIZE sizeof(context->u[0].ctx.hash)
unsigned i;
// Compute adjusted key (hashed from original key if necessary)
memset(context->u[0].k, 0, BLOCK_SIZE);
if (key_length <= BLOCK_SIZE) {
memcpy(context->u[0].k, key, key_length);
} else {
hash_init(&context->u[1].ctx);
hash_update(&context->u[1].ctx, key, key_length);
hash_finalize(&context->u[1].ctx);
memcpy(context->u[0].k, context->u[1].ctx.hash, HASH_SIZE);
}
// Set context->u[0].k to K XOR opad, context->u[1].k to K XOR ipad
for (i = 0; i < BLOCK_SIZE; i++) {
context->u[1].k[i] = context->u[0].k[i] ^ 0x36;
context->u[0].k[i] ^= 0x5C;
}
// Save inner hash context following initial block as context->u[2].ctx
hash_init(&context->u[2].ctx);
hash_update(&context->u[2].ctx, context->u[1].k, BLOCK_SIZE);
// Save outer hash context following initial block as context->u[1].ctx
hash_init(&context->u[1].ctx);
hash_update(&context->u[1].ctx, context->u[0].k, BLOCK_SIZE);
}
void hmac_compute(struct hmac_context *context,
const unsigned char *message,
unsigned long message_length)
{
// Compute inner hash
context->u[0].ctx = context->u[2].ctx;
hash_update(&context->u[0].ctx, message, message_length);
hash_finalize(&context->u[0].ctx);
memcpy(context->inner_hash, context->u[0].ctx.hash, HASH_SIZE);
// Compute outer hash
context->u[0].ctx = context->u[1].ctx;
hash_update(&context->u[0].ctx, context->inner_hash, HASH_SIZE);
hash_finalize(&context->u[0].ctx);
}