/*
 * LITLS -- HMAC-SHA256 and HMAC-SHA384 (RFC 2104)
 */

#include "litls.h"
#include <string.h>

void litls_hmac_sha256(const uint8_t *key, size_t key_len, const uint8_t *msg, size_t msg_len, uint8_t out[32]) {
    uint8_t k_pad[LITLS_SHA256_BLOCK_SIZE];
    uint8_t inner_hash[32];
    litls_sha256_ctx ctx;

    /* If key is longer than block size, hash it */
    uint8_t key_hash[32];
    if (key_len > LITLS_SHA256_BLOCK_SIZE) {
        litls_sha256(key, key_len, key_hash);
        key     = key_hash;
        key_len = 32;
    }

    /* ipad = key XOR 0x36 */
    memset(k_pad, 0x36, LITLS_SHA256_BLOCK_SIZE);
    for (size_t i = 0; i < key_len; i++)
        k_pad[i] ^= key[i];

    litls_sha256_init(&ctx);
    litls_sha256_update(&ctx, k_pad, LITLS_SHA256_BLOCK_SIZE);
    litls_sha256_update(&ctx, msg, msg_len);
    litls_sha256_final(&ctx, inner_hash);

    /* opad = key XOR 0x5c */
    memset(k_pad, 0x5c, LITLS_SHA256_BLOCK_SIZE);
    for (size_t i = 0; i < key_len; i++)
        k_pad[i] ^= key[i];

    litls_sha256_init(&ctx);
    litls_sha256_update(&ctx, k_pad, LITLS_SHA256_BLOCK_SIZE);
    litls_sha256_update(&ctx, inner_hash, 32);
    litls_sha256_final(&ctx, out);
}

void litls_hmac_sha384(const uint8_t *key, size_t key_len, const uint8_t *msg, size_t msg_len, uint8_t out[48]) {
    uint8_t k_pad[LITLS_SHA384_BLOCK_SIZE];
    uint8_t inner_hash[48];
    litls_sha384_ctx ctx;

    uint8_t key_hash[48];
    if (key_len > LITLS_SHA384_BLOCK_SIZE) {
        litls_sha384(key, key_len, key_hash);
        key     = key_hash;
        key_len = 48;
    }

    memset(k_pad, 0x36, LITLS_SHA384_BLOCK_SIZE);
    for (size_t i = 0; i < key_len; i++)
        k_pad[i] ^= key[i];

    litls_sha384_init(&ctx);
    litls_sha384_update(&ctx, k_pad, LITLS_SHA384_BLOCK_SIZE);
    litls_sha384_update(&ctx, msg, msg_len);
    litls_sha384_final(&ctx, inner_hash);

    memset(k_pad, 0x5c, LITLS_SHA384_BLOCK_SIZE);
    for (size_t i = 0; i < key_len; i++)
        k_pad[i] ^= key[i];

    litls_sha384_init(&ctx);
    litls_sha384_update(&ctx, k_pad, LITLS_SHA384_BLOCK_SIZE);
    litls_sha384_update(&ctx, inner_hash, 48);
    litls_sha384_final(&ctx, out);
}