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/*
 * oauth2-oidc-sdk
 *
 * Copyright 2012-2016, Connect2id Ltd and contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use
 * this file except in compliance with the License. You may obtain a copy of the
 * License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed
 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */

package com.nimbusds.openid.connect.sdk.id;


import java.util.AbstractMap;
import java.util.Map;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import com.nimbusds.jose.util.Base64URL;
import com.nimbusds.jose.util.ByteUtils;
import com.nimbusds.oauth2.sdk.id.Subject;
import net.jcip.annotations.ThreadSafe;
import org.cryptomator.siv.SivMode;


/**
 * SIV AES - based encoder / decoder of pairwise subject identifiers. Requires
 * a 256, 384, or 512-bit secret key. Reversal is supported.
 *
 * 

The plain text is formatted as follows ('|' as delimiter): * *

 * sector_id|local_sub
 * 
* *

The encoder can be configured to pad the local subject up to a certain * string length, typically the maximum expected length of the local subject * identifiers, to ensure the output pairwise subject identifiers are output * with a length that is uniform and doesn't vary with the local subject * identifier length. This is intended as an additional measure against leaking * end-user information and hence correlation. Note that local subjects that * are longer than the configured length will appear as proportionally longer * pairwise identifiers. * *

Pad local subjects that are shorter than 50 characters in length: * *

 * new SIVAESBasedPairwiseSubjectCodec(secretKey, 50);
 * 
* *

Related specifications: * *

    *
  • Synthetic Initialization Vector (SIV) Authenticated Encryption Using * the Advanced Encryption Standard (AES) (RFC 5297). *
  • OpenID Connect Core 1.0, section 8.1. *
*/ @ThreadSafe public class SIVAESBasedPairwiseSubjectCodec extends PairwiseSubjectCodec { /** * The AES SIV crypto engine. */ private static final SivMode AES_SIV = new SivMode(); /** * The AES CTR key (1st half). */ private final byte[] aesCtrKey; /** * The MAC key (2nd half). */ private final byte[] macKey; /** * Pads the local subject to the specified length, -1 for no padding. */ private final int padSubjectToLength; /** * Creates a new SIV AES - based codec for pairwise subject * identifiers. Local subjects are not padded up to a certain length. * * @param secretKey A 256, 384, or 512-bit secret key. Must not be * {@code null}. */ public SIVAESBasedPairwiseSubjectCodec(final SecretKey secretKey) { this(secretKey, -1); } /** * Creates a new SIV AES - based codec for pairwise subject * identifiers. * * @param secretKey A 256, 384, or 512-bit secret key. Must * not be {@code null}. * @param padSubjectToLength Pads the local subject to the specified * length, -1 (negative integer) for no * padding. */ public SIVAESBasedPairwiseSubjectCodec(final SecretKey secretKey, final int padSubjectToLength) { super(null); if (secretKey == null) { throw new IllegalArgumentException("The SIV AES secret key must not be null"); } byte[] keyBytes = secretKey.getEncoded(); switch (keyBytes.length) { case 32: aesCtrKey = ByteUtils.subArray(keyBytes, 0, 16); macKey = ByteUtils.subArray(keyBytes, 16, 16); break; case 48: aesCtrKey = ByteUtils.subArray(keyBytes, 0, 24); macKey = ByteUtils.subArray(keyBytes, 24, 24); break; case 64: aesCtrKey = ByteUtils.subArray(keyBytes, 0, 32); macKey = ByteUtils.subArray(keyBytes, 32, 32); break; default: throw new IllegalArgumentException("The SIV AES secret key length must be 256, 384 or 512 bits"); } this.padSubjectToLength = padSubjectToLength; } /** * Returns the secret key. * * @return The key. */ public SecretKey getSecretKey() { return new SecretKeySpec(ByteUtils.concat(aesCtrKey, macKey), "AES"); } /** * Returns the optional padded string length of local subjects. * * @return The padding string length, -1 (negative integer) for no * padding. */ public int getPadSubjectToLength() { return padSubjectToLength; } private static String escapeSeparator(final String s) { return s.replace("|", "\\|"); } @Override public Subject encode(final SectorID sectorID, final Subject localSub) { // Escape separator chars final String escapedSectorIDString = escapeSeparator(sectorID.getValue()); final String escapedLocalSub = escapeSeparator(localSub.getValue()); StringBuilder optionalPadding = new StringBuilder(); if (padSubjectToLength > 0) { // Apply padding int paddingLength = padSubjectToLength - escapedLocalSub.length(); if (paddingLength == 1) { optionalPadding = new StringBuilder("|"); } else if (paddingLength > 1) { optionalPadding = new StringBuilder("|"); int i = paddingLength; while (--i > 0) { optionalPadding.append("0"); // pad with 0 } } } // Join parameters, delimited by '|' final String plainTextString = (escapedSectorIDString + '|' + escapedLocalSub + optionalPadding); byte[] plainText = plainTextString.getBytes(CHARSET); byte[] cipherText = AES_SIV.encrypt(aesCtrKey, macKey, plainText); return new Subject(Base64URL.encode(cipherText).toString()); } @Override public Map.Entry decode(final Subject pairwiseSubject) throws InvalidPairwiseSubjectException { byte[] cipherText = new Base64URL(pairwiseSubject.getValue()).decode(); byte[] plainText; try { plainText = AES_SIV.decrypt(aesCtrKey, macKey, cipherText); } catch (Exception e) { throw new InvalidPairwiseSubjectException("Decryption failed: " + e.getMessage(), e); } // Split along the '|' delimiter String[] parts = new String(plainText, CHARSET).split("(? 3) { throw new InvalidPairwiseSubjectException("Invalid format: Unexpected number of tokens: " + parts.length); } return new AbstractMap.SimpleImmutableEntry<>(new SectorID(parts[0]), new Subject(parts[1])); } }




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