/**************************** hmac.c ***************************/
/***************** See RFC 6234 for details. *******************/
/* Copyright (c) 2011 IETF Trust and the persons identified as */
/* authors of the code. All rights reserved. */
/* See sha.h for terms of use and redistribution. */
/*
* Description:
* This file implements the HMAC algorithm (Keyed-Hashing for
* Message Authentication, [RFC 2104]), expressed in terms of
* the various SHA algorithms.
*/
#include "sha.h"
#include <stddef.h>
/*
* hmac
*
* Description:
* This function will compute an HMAC message digest.
*
* Parameters:
* whichSha: [in]
* One of SHA1, SHA224, SHA256, SHA384, SHA512
* message_array[ ]: [in]
* An array of octets representing the message.
* Note: in RFC 2104, this parameter is known
* as 'text'.
* length: [in]
* The length of the message in message_array.
* key[ ]: [in]
* The secret shared key.
* key_len: [in]
* The length of the secret shared key.
* digest[ ]: [out]
* Where the digest is to be returned.
* NOTE: The length of the digest is determined by
* the value of whichSha.
*
* Returns:
* sha Error Code.
*
*/
int hmac(SHAversion whichSha,
const unsigned char *message_array, size_t length,
const unsigned char *key, size_t key_len,
uint8_t digest[USHAMaxHashSize])
{
HMACContext context;
return hmacReset(&context, whichSha, key, key_len) ||
hmacInput(&context, message_array, length) ||
hmacResult(&context, digest);
}
/*
* hmacReset
*
* Description:
* This function will initialize the hmacContext in preparation
* for computing a new HMAC message digest.
*
* Parameters:
* context: [in/out]
* The context to reset.
* whichSha: [in]
* One of SHA1, SHA224, SHA256, SHA384, SHA512
* key[ ]: [in]
* The secret shared key.
* key_len: [in]
* The length of the secret shared key.
*
* Returns:
* sha Error Code.
*
*/
int hmacReset(HMACContext *context, enum SHAversion whichSha,
const unsigned char *key, size_t key_len)
{
size_t i, blocksize, hashsize;
int ret;
/* inner padding - key XORd with ipad */
unsigned char k_ipad[USHA_Max_Message_Block_Size];
/* temporary buffer when keylen > blocksize */
unsigned char tempkey[USHAMaxHashSize];
if (!context) return shaNull;
context->Computed = 0;
context->Corrupted = shaSuccess;
blocksize = context->blockSize = USHABlockSize(whichSha);
hashsize = context->hashSize = USHAHashSize(whichSha);
context->whichSha = whichSha;
/*
* If key is longer than the hash blocksize,
* reset it to key = HASH(key).
*/
if (key_len > blocksize) {
USHAContext tcontext;
int err = USHAReset(&tcontext, whichSha) ||
USHAInput(&tcontext, key, key_len) ||
USHAResult(&tcontext, tempkey);
if (err != shaSuccess) return err;
key = tempkey;
key_len = hashsize;
}
/*
* The HMAC transform looks like:
*
* SHA(K XOR opad, SHA(K XOR ipad, text))
*
* where K is an n byte key, 0-padded to a total of blocksize bytes,
* ipad is the byte 0x36 repeated blocksize times,
* opad is the byte 0x5c repeated blocksize times,
* and text is the data being protected.
*/
/* store key into the pads, XOR'd with ipad and opad values */
for (i = 0; i < key_len; i++) {
k_ipad[i] = key[i] ^ 0x36;
context->k_opad[i] = key[i] ^ 0x5c;
}
/* remaining pad bytes are '\0' XOR'd with ipad and opad values */
for (; i < blocksize; i++) {
k_ipad[i] = 0x36;
context->k_opad[i] = 0x5c;
}
/* perform inner hash */
/* init context for 1st pass */
ret = USHAReset(&context->shaContext, whichSha) ||
/* and start with inner pad */
USHAInput(&context->shaContext, k_ipad, blocksize);
return context->Corrupted = ret;
}
/*
* hmacInput
*
* Description:
* This function accepts an array of octets as the next portion
* of the message. It may be called multiple times.
*
* Parameters:
* context: [in/out]
* The HMAC context to update.
* text[ ]: [in]
* An array of octets representing the next portion of
* the message.
* text_len: [in]
* The length of the message in text.
*
* Returns:
* sha Error Code.
*
*/
int hmacInput(HMACContext *context, const unsigned char *text,
size_t text_len)
{
if (!context) return shaNull;
if (context->Corrupted) return context->Corrupted;
if (context->Computed) return context->Corrupted = shaStateError;
/* then text of datagram */
return context->Corrupted =
USHAInput(&context->shaContext, text, text_len);
}
/*
* hmacFinalBits
*
* Description:
* This function will add in any final bits of the message.
*
* Parameters:
* context: [in/out]
* The HMAC context to update.
* message_bits: [in]
* The final bits of the message, in the upper portion of the
* byte. (Use 0b###00000 instead of 0b00000### to input the
* three bits ###.)
* length: [in]
* The number of bits in message_bits, between 1 and 7.
*
* Returns:
* sha Error Code.
*/
int hmacFinalBits(HMACContext *context,
uint8_t bits, unsigned int bit_count)
{
if (!context) return shaNull;
if (context->Corrupted) return context->Corrupted;
if (context->Computed) return context->Corrupted = shaStateError;
/* then final bits of datagram */
return context->Corrupted =
USHAFinalBits(&context->shaContext, bits, bit_count);
}
/*
* hmacResult
*
* Description:
* This function will return the N-byte message digest into the
* Message_Digest array provided by the caller.
*
* Parameters:
* context: [in/out]
* The context to use to calculate the HMAC hash.
* digest[ ]: [out]
* Where the digest is returned.
* NOTE 2: The length of the hash is determined by the value of
* whichSha that was passed to hmacReset().
*
* Returns:
* sha Error Code.
*
*/
int hmacResult(HMACContext *context, uint8_t *digest)
{
int ret;
if (!context) return shaNull;
if (context->Corrupted) return context->Corrupted;
if (context->Computed) return context->Corrupted = shaStateError;
/* finish up 1st pass */
/* (Use digest here as a temporary buffer.) */
ret =
USHAResult(&context->shaContext, digest) ||
/* perform outer SHA */
/* init context for 2nd pass */
USHAReset(&context->shaContext, context->whichSha) ||
/* start with outer pad */
USHAInput(&context->shaContext, context->k_opad,
context->blockSize) ||
/* then results of 1st hash */
USHAInput(&context->shaContext, digest, context->hashSize) ||
/* finish up 2nd pass */
USHAResult(&context->shaContext, digest);
context->Computed = 1;
return context->Corrupted = ret;
}