70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
#include "TOTP.h"
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#include "sha1.h"
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uint8_t* _hmacKey;
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uint8_t _keyLength;
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uint8_t _timeZoneOffset;
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uint32_t _timeStep;
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// Init the library with the private key, its length and the timeStep duration
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void TOTP(uint8_t* hmacKey, uint8_t keyLength, uint32_t timeStep) {
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_hmacKey = hmacKey;
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_keyLength = keyLength;
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_timeStep = timeStep;
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}
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void setTimezone(uint8_t timezone){
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_timeZoneOffset = timezone;
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}
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uint32_t TimeStruct2Timestamp(struct tm time){
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//time.tm_mon -= 1;
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//time.tm_year -= 1900;
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return mktime(&(time)) - (_timeZoneOffset * 3600) - 2208988800;
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}
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// Generate a code, using the timestamp provided
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uint32_t getCodeFromTimestamp(uint32_t timeStamp) {
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uint32_t steps = timeStamp / _timeStep;
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return getCodeFromSteps(steps);
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}
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// Generate a code, using the timestamp provided
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uint32_t getCodeFromTimeStruct(struct tm time) {
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return getCodeFromTimestamp(TimeStruct2Timestamp(time));
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}
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// Generate a code, using the number of steps provided
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uint32_t getCodeFromSteps(uint32_t steps) {
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// STEP 0, map the number of steps in a 8-bytes array (counter value)
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uint8_t _byteArray[8];
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_byteArray[0] = 0x00;
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_byteArray[1] = 0x00;
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_byteArray[2] = 0x00;
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_byteArray[3] = 0x00;
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_byteArray[4] = (uint8_t)((steps >> 24) & 0xFF);
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_byteArray[5] = (uint8_t)((steps >> 16) & 0xFF);
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_byteArray[6] = (uint8_t)((steps >> 8) & 0XFF);
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_byteArray[7] = (uint8_t)((steps & 0XFF));
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// STEP 1, get the HMAC-SHA1 hash from counter and key
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initHmac(_hmacKey, _keyLength);
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writeArray(_byteArray, 8);
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uint8_t* _hash = resultHmac();
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// STEP 2, apply dynamic truncation to obtain a 4-bytes string
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uint32_t _truncatedHash = 0;
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uint8_t _offset = _hash[20 - 1] & 0xF;
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uint8_t j;
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for (j = 0; j < 4; ++j) {
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_truncatedHash <<= 8;
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_truncatedHash |= _hash[_offset + j];
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}
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// STEP 3, compute the OTP value
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_truncatedHash &= 0x7FFFFFFF; //Disabled
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_truncatedHash %= 1000000;
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return _truncatedHash;
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}
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