name.martingeisse.common.security.SecurityTokenUtil.java Source code

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Here is the source code for name.martingeisse.common.security.SecurityTokenUtil.java

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/**
 * Copyright (c) 2010 Martin Geisse
 *
 * This file is distributed under the terms of the MIT license.
 */

package name.martingeisse.common.security;

import java.util.Locale;
import name.martingeisse.common.util.HmacUtil;
import org.apache.commons.lang3.StringUtils;
import org.joda.time.ReadableInstant;
import org.joda.time.format.DateTimeFormatter;
import org.joda.time.format.ISODateTimeFormat;

/**
 * Some utility methods to handle signed security tokens.
 */
public final class SecurityTokenUtil {

    /**
     * the dateTimeFormatter
     */
    private static final DateTimeFormatter dateTimeFormatter = ISODateTimeFormat.dateTimeNoMillis()
            .withLocale(Locale.US).withZoneUTC();

    /**
     * Prevent instantiation.
     */
    private SecurityTokenUtil() {
    }

    /**
     * Cretes a signed token that contains a subject (a simple keyword that tells what
     * the token is about), a timestamp, and a HMAC that is generated from the payload
     * data and a secret.
     * 
     * This method makes no assumptions about whether the timestamp denotes the creation
     * time or the expiry time of the token. This is left to the methods that check
     * tokens for validity.
     * 
     * @param subject the subject. Should not contain pipe characters.
     * @param timestamp the timestamp
     * @param secret the secret used to generate the HMAC
     * @return the token
     */
    public static String createToken(String subject, ReadableInstant timestamp, String secret) {
        StringBuilder builder = new StringBuilder();
        builder.append(subject);
        builder.append('|');
        builder.append(dateTimeFormatter.print(timestamp));
        String payload = builder.toString();
        builder.append('|');
        builder.append(HmacUtil.generateHmacBase64(payload, secret, HmacUtil.ALGORITHM_SHA256));
        return builder.toString();
    }

    /**
     * Validates the specified security token. Returns the subject if the token is valid.
     * Throws an {@link IllegalArgumentException} if invalid. This exception contains
     * an error message about the problem.
     * 
     * @param token the token
     * @param minTimestamp the maximum allowed value for the token's timestamp
     * @param secret the secret used to generate the HMAC
     * @return the token's subject
     */
    public static String validateToken(String token, ReadableInstant minTimestamp, String secret) {

        // split the token into segments
        String[] tokenSegments = StringUtils.split(token, '|');
        if (tokenSegments.length != 3) {
            throw new IllegalArgumentException("malformed token (has " + tokenSegments.length + " segments)");
        }

        // validate the signature
        String payload = (tokenSegments[0] + '|' + tokenSegments[1]);
        String expectedSignatureBase64 = HmacUtil.generateHmacBase64(payload, secret, HmacUtil.ALGORITHM_SHA256);
        if (!expectedSignatureBase64.equals(tokenSegments[2])) {
            throw new IllegalArgumentException("invalid token signature");
        }

        // validate the timestamp
        ReadableInstant timestamp;
        try {
            timestamp = dateTimeFormatter.parseDateTime(tokenSegments[1]);
        } catch (IllegalArgumentException e) {
            throw new IllegalArgumentException("malformed timestamp: " + e.getMessage());
        }
        if (timestamp.isBefore(minTimestamp)) {
            throw new IllegalArgumentException("token has expired");
        }

        // return the subject
        return tokenSegments[0];

    }

}