[136] | 1 | /*
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| 2 | ###############################################################################
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| 3 | #
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| 4 | # Temboo Arduino library
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| 5 | #
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| 6 | # Copyright 2014, Temboo Inc.
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| 7 | #
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| 8 | # Licensed under the Apache License, Version 2.0 (the "License");
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| 9 | # you may not use this file except in compliance with the License.
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| 10 | # You may obtain a copy of the License at
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| 11 | #
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| 12 | # http://www.apache.org/licenses/LICENSE-2.0
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| 13 | #
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| 14 | # Unless required by applicable law or agreed to in writing,
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| 15 | # software distributed under the License is distributed on an
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| 16 | # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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| 17 | # either express or implied. See the License for the specific
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| 18 | # language governing permissions and limitations under the License.
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| 19 | #
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| 20 | ###############################################################################
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| 21 | */
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| 22 |
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| 23 | #include <string.h>
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| 24 | #include <avr/pgmspace.h>
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| 25 | #include "tmbhmac.h"
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| 26 |
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| 27 | HMAC::HMAC() {
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| 28 | }
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| 29 |
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| 30 | HMAC::HMAC(const uint8_t* key, uint32_t keyLength) {
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| 31 | init(key, keyLength);
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| 32 | }
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| 33 |
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| 34 | void HMAC::init(const uint8_t* key, uint32_t keyLength) {
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| 35 |
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| 36 | m_key = key;
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| 37 | m_keyLength = keyLength;
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| 38 |
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| 39 | uint8_t iKeyPad[HMAC_BLOCK_SIZE_BYTES];
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| 40 |
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| 41 | constructKeyPad(iKeyPad, key, keyLength, (uint8_t)0x36);
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| 42 |
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| 43 | m_md5.init();
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| 44 | m_md5.process(iKeyPad, HMAC_BLOCK_SIZE_BYTES);
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| 45 | }
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| 46 |
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| 47 | void HMAC::process(const uint8_t* msg, uint32_t msgLength) {
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| 48 | // hmac = hash(o_key_pad + hash(i_key_pad + message))
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| 49 | // continue hashing the message
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| 50 | m_md5.process(msg, msgLength);
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| 51 | }
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| 52 |
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| 53 | void HMAC::finish(uint8_t* dest) {
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| 54 | //hmac = hash(o_key_pad + hash(i_key_pad + message))
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| 55 | //
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| 56 | // Construct the o_key_pad
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| 57 | uint8_t finalBlock[HMAC_BLOCK_SIZE_BYTES + HMAC_HASH_SIZE_BYTES];
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| 58 | constructKeyPad(finalBlock, m_key, m_keyLength, (uint8_t)0x5C);
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| 59 | m_md5.finish(finalBlock + HMAC_BLOCK_SIZE_BYTES);
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| 60 |
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| 61 | m_md5.init();
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| 62 | m_md5.process(finalBlock, HMAC_BLOCK_SIZE_BYTES + HMAC_HASH_SIZE_BYTES);
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| 63 | m_md5.finish(dest);
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| 64 | }
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| 65 |
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| 66 | void HMAC::finishHex(char* dest) {
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| 67 | uint8_t binDest[HMAC_HASH_SIZE_BYTES];
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| 68 | finish(binDest);
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| 69 | toHex(binDest, dest);
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| 70 | }
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| 71 |
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| 72 | void HMAC::toHex(uint8_t* hmac, char* dest) {
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| 73 | static const char hex[17] PROGMEM = "0123456789abcdef";
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| 74 | uint16_t i;
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| 75 | for (i = 0; i < HMAC_HASH_SIZE_BYTES; i++) {
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| 76 | dest[i*2] = pgm_read_byte(&hex[hmac[i] >> 4]);
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| 77 | dest[(i*2) + 1] = pgm_read_byte(&hex[hmac[i] & 0x0F]);
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| 78 | }
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| 79 | dest[HMAC_HASH_SIZE_BYTES * 2] = '\0';
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| 80 | }
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| 81 |
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| 82 | /*
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| 83 | * dest MUST be big enough to hold HMAC_BLOCK_SIZE_BYTES
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| 84 | */
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| 85 | void HMAC::constructKeyPad(uint8_t* dest, const uint8_t* key, uint32_t keyLength, uint8_t padByte) {
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| 86 |
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| 87 | if (keyLength > HMAC_BLOCK_SIZE_BYTES) {
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| 88 | // If the key is bigger than 1 block,
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| 89 | // replace the key with the hash of the key.
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| 90 | MD5 md5;
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| 91 | md5.process(key, keyLength);
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| 92 | md5.finish(dest);
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| 93 | keyLength = HMAC_HASH_SIZE_BYTES;
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| 94 | } else {
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| 95 | // If the key length is <= to the HMAC block length,
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| 96 | // just use the key as-is.
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| 97 | memcpy(dest, key, keyLength);
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| 98 | }
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| 99 | // pad the remaining space with 0s
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| 100 | if (keyLength < HMAC_BLOCK_SIZE_BYTES) {
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| 101 | memset(dest + keyLength, 0, HMAC_BLOCK_SIZE_BYTES-keyLength);
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| 102 | }
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| 103 |
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| 104 | for (int i = 0; i < HMAC_BLOCK_SIZE_BYTES; i++) {
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| 105 | dest[i] ^= padByte;
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| 106 | }
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| 107 | }
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