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#include "ArduinoJsonJWT.h"
ArduinoJsonJWT::ArduinoJsonJWT(String secret) : _secret(secret) { }
void ArduinoJsonJWT::setSecret(String secret) { _secret = secret; }
String ArduinoJsonJWT::getSecret() { return _secret; }
/*
* ESP32 uses mbedtls, ESP2866 uses bearssl. * * Both come with decent HMAC implmentations supporting sha256, as well as others. * * No need to pull in additional crypto libraries - lets use what we already have. */ String ArduinoJsonJWT::sign(String& payload) { unsigned char hmacResult[32]; { #ifdef ESP32
mbedtls_md_context_t ctx; mbedtls_md_type_t md_type = MBEDTLS_MD_SHA256; mbedtls_md_init(&ctx); mbedtls_md_setup(&ctx, mbedtls_md_info_from_type(md_type), 1); mbedtls_md_hmac_starts(&ctx, (unsigned char*)_secret.c_str(), _secret.length()); mbedtls_md_hmac_update(&ctx, (unsigned char*)payload.c_str(), payload.length()); mbedtls_md_hmac_finish(&ctx, hmacResult); mbedtls_md_free(&ctx); #elif defined(ESP8266)
br_hmac_key_context keyCtx; br_hmac_key_init(&keyCtx, &br_sha256_vtable, _secret.c_str(), _secret.length()); br_hmac_context hmacCtx; br_hmac_init(&hmacCtx, &keyCtx, 0); br_hmac_update(&hmacCtx, payload.c_str(), payload.length()); br_hmac_out(&hmacCtx, hmacResult); #endif
} return encode((char*)hmacResult, 32); }
String ArduinoJsonJWT::buildJWT(JsonObject& payload) { // serialize, then encode payload
String jwt; serializeJson(payload, jwt); jwt = encode(jwt.c_str(), jwt.length());
// add the header to payload
jwt = JWT_HEADER + '.' + jwt;
// add signature
jwt += '.' + sign(jwt);
return jwt; }
void ArduinoJsonJWT::parseJWT(String jwt, JsonDocument& jsonDocument) { // clear json document before we begin, jsonDocument wil be null on failure
jsonDocument.clear();
// must have the correct header and delimiter
if (!jwt.startsWith(JWT_HEADER) || jwt.indexOf('.') != JWT_HEADER_SIZE) { return; }
// check there is a signature delimieter
int signatureDelimiterIndex = jwt.lastIndexOf('.'); if (signatureDelimiterIndex == JWT_HEADER_SIZE) { return; }
// check the signature is valid
String signature = jwt.substring(signatureDelimiterIndex + 1); jwt = jwt.substring(0, signatureDelimiterIndex); if (sign(jwt) != signature) { return; }
// decode payload
jwt = jwt.substring(JWT_HEADER_SIZE + 1); jwt = decode(jwt);
// parse payload, clearing json document after failure
DeserializationError error = deserializeJson(jsonDocument, jwt); if (error != DeserializationError::Ok || !jsonDocument.is<JsonObject>()) { jsonDocument.clear(); } }
String ArduinoJsonJWT::encode(const char* cstr, int inputLen) { // prepare encoder
base64_encodestate _state; #ifdef ESP32
base64_init_encodestate(&_state); size_t encodedLength = base64_encode_expected_len(inputLen) + 1; #elif defined(ESP8266)
base64_init_encodestate_nonewlines(&_state); size_t encodedLength = base64_encode_expected_len_nonewlines(inputLen) + 1; #endif
// prepare buffer of correct length, returning an empty string on failure
char* buffer = (char*)malloc(encodedLength * sizeof(char)); if (buffer == nullptr) { return ""; }
// encode to buffer
int len = base64_encode_block(cstr, inputLen, &buffer[0], &_state); len += base64_encode_blockend(&buffer[len], &_state); buffer[len] = 0;
// convert to arduino string, freeing buffer
String value = String(buffer); free(buffer); buffer = nullptr;
// remove padding and convert to URL safe form
while (value.length() > 0 && value.charAt(value.length() - 1) == '=') { value.remove(value.length() - 1); } value.replace('+', '-'); value.replace('/', '_');
// return as string
return value; }
String ArduinoJsonJWT::decode(String value) { // convert to standard base64
value.replace('-', '+'); value.replace('_', '/');
// prepare buffer of correct length
char buffer[base64_decode_expected_len(value.length()) + 1];
// decode
int len = base64_decode_chars(value.c_str(), value.length(), &buffer[0]); buffer[len] = 0;
// return as string
return String(buffer); }
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