Firebase JWT-php 'Signature verification failed' on JWT::decode - php

Question

Here's my code generating the token:
public static function GenerateNewAuthTokens(User $user): string {
$issuedAt = new DateTimeImmutable();
$expire = $issuedAt->modify('+' . AuthenticationHelper::AUTH_EXPIRE_MINUTES . ' minutes');
$username = $user->Username;
$issuedAtTimestamp = $issuedAt->getTimestamp();
$auth_data = [
'iat' => $issuedAtTimestamp, // Issued at: time when the token was generated
'iss' => AuthenticationHelper::SERVER_NAME, // Issuer
'nbf' => $issuedAtTimestamp, // Not before
'exp' => $expire->getTimestamp(), // Expire
'userName' => $username, // User name
];
return JWT::encode(
$auth_data,
AuthenticationHelper::SECRET_KEY,
AuthenticationHelper::ALGORITHM
);
}
Here is my code attempting to decode the token:
public static function GetAuthData(): ?object {
$headers = getallheaders();
if (isset($headers) && count($headers) && isset($headers['Authorization']) && strlen($headers['Authorization']) > 7) {
try {
$token = explode(" ", $headers['Authorization'])[1];
$decodedToken = JWT::decode($token, new Key(AuthenticationHelper::SECRET_KEY, AuthenticationHelper::ALGORITHM));
return $decodedToken;
} catch (\Throwable $th) {
//TODO
$err = $th;
}
}
return null;
}
It throws the "Signature verification failed" error in the JWT code here.
So far as I can tell - I'm following the example given on the repo home screen to a reasonable approximation.
I am using HS512 but have tried HS256 as well with no difference.
I have confirmed that the token I'm attempting to decode is exactly what was generated in the first method.
It's failing the compare check here, due to $hash and $signature not matching.

Answer 1

So turns out I wasn't sending the exact same token back that I was receiving. When JWT encodes the token data, it trims off the = at the end of any of the base64 encoded strings.
What I had stored contains those = at the end (usually). Because of this, when it ran its compare - it failed.
In summary - dur - check the values better.