OAuth 2.0. No session? (stateless)

Question

I\'m going to implement OAuth 2.0 and REST API with it

to grant different permissions per users and also to scale well.

To scal

Answer 1

A more recent innovation is JWT - JSON Web Token.

Here is a link to the spec: JWT - JSON Web Token

JWT is a method of using Hashed tokens using a Hashing method such as HMAC which stands for a Hash-based Message Authentication Code. Because the token is hashed using a secret key, the server can determine if the token has been tampered with.

Here is an example method to create a Hashed token for JWT:

    public String createTokenForUser(User user) {
        byte[] userBytes = toJSON(user);
        byte[] hash = createHmac(userBytes);
        final StringBuilder sb = new StringBuilder(170);
        sb.append(toBase64(userBytes));
        sb.append(SEPARATOR);
        sb.append(toBase64(hash));
        return sb.toString();
    }

Here is an example of decoding a token to ensure it was not tampered with:

public User parseUserFromToken(String token) {
    final String[] parts = token.split(SEPARATOR_SPLITTER);
    if (parts.length == 2 && parts[0].length() > 0 && parts[1].length() > 0) {
        try {
            final byte[] userBytes = fromBase64(parts[0]);
            final byte[] hash = fromBase64(parts[1]);

            boolean validHash = Arrays.equals(createHmac(userBytes), hash);
            if (validHash) {
                final User user = fromJSON(userBytes);
                if (new Date().getTime() < user.getExpires()) {
                    return user;
                }
            }
        } catch (IllegalArgumentException e) {
            //log tampering attempt here
        }
    }
    return null;
}

Here is an article with a more complete example: Stateless Authentication