9ebea46300
* totp : rework and add SHA256/512 * totp : comment code * totp : fix SHA224/SHA384 and examples * totp : fix bug in totp_face_lfs * totp : init_totp_record to SHA1 * totp : move TOTP-MCU to TOTP, update README and example * totp : SHAX, use size_t n instead of harcoded 8 * clarify what to put in TOTP face Co-authored-by: Emilien <Emilien> Co-authored-by: joeycastillo <joeycastillo@utexas.edu>
69 lines
2.9 KiB
Markdown
69 lines
2.9 KiB
Markdown
TOTP Pure C Library
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====================
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Library to generate Time-based One-Time Passwords.
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Implements the Time-based One-Time Password algorithm specified in [RFC 6238](https://tools.ietf.org/html/rfc6238).
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Supports different time steps and is compatible with tokens that use the same standard (including software ones, like the Google Authenticator app).
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The code is made of :
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- [TOTP-MCU](https://github.com/Netthaw/TOTP-MCU) for `TimeStruct2Timestamp`, `getCodeFromTimestamp`, `getCodeFromTimeStruct`, part of `getCodeFromSteps` and `TOTP_HMAC_SHA*` functions
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- [mbedtls](https://github.com/Mbed-TLS/mbedtls) for SHA1/SHA224/SHA256/SHA384/SHA512 implementations
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- [this project](https://github.com/mygityf/cipher/blob/master/cipher/hmac.c) as an inspiration for writing the code to compute the TOTP using the key and the text to hash
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Supported algorithms are SHA1/SHA224/SHA256/SHA384/SHA512.
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Installation & usage:
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--------------------
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First include header to your file
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```c
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#include "TOTP.h"
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```
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After included, define key ex. Key is ```MyLegoDoor```
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- Note: The format of hmacKey is array of hexadecimal bytes.
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- Most websites provide the key encoded in base32 - RFC3548/RFC4648, either upper or lower case. You can use [this site](https://cryptii.com/pipes/base32-to-hex) to convert the base32 string to hex (make sure you upcase it first if it's lowercase and remove all whitespaces).
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```c
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uint8_t hmacKey[] = {0x4d, 0x79, 0x4c, 0x65, 0x67, 0x6f, 0x44, 0x6f, 0x6f, 0x72}; // Secret key
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```
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Instantiate the TOTP class by providing the secret hmacKey, the length of the hmacKey, the Timestep between codes and the algorithm used (most of the time, `SHA1`).
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```c
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TOTP(hmacKey, 10, 30, SHA1); // Secret key, Secret key length, Timestep (30s), Algorithm
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```
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Use the ```getCodeFromTimestamp()``` function to get a TOTP from a unix epoch timestamp
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```c
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uint32_t newCode = getCodeFromTimestamp(1557414000); // Current timestamp since Unix epoch in seconds
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```
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Or ```getCodeFromTimeStruct()``` if you want to get a TOTP from a tm struct (Time Struct in C),
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```c
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struct tm datetime;
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datetime.tm_hour = 9;
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datetime.tm_min = 0;
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datetime.tm_sec = 0;
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datetime.tm_mday = 13;
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datetime.tm_mon = 5;
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datetime.tm_year = 2019;
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uint32_t newCode = getCodeFromTimeStruct(datetime);
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```
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If the provided unix timestamp isn't in UTC±0, use ```setTimezone()``` before ```getCodeFromTimestamp()``` or ```getCodeFromTimeStruct()``` to offset the time.
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```c
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setTimezone(9); // Set timezone +9 Japan
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```
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You can see an example in example.c (compile it with `gcc -o example example.c sha1.c sha256.c sha512.c TOTP.c -I.`)
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Thanks to:
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----------
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* Netthaw, https://github.com/Netthaw/TOTP-MCU
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* Mbed-TLS, https://github.com/Mbed-TLS/mbedtls
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* mygityf, https://github.com/mygityf/cipher/blob/master/cipher/hmac.c
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* susam, https://github.com/susam/mintotp
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