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