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/*
* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* 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 io.undertow.security.impl;
import static io.undertow.UndertowMessages.MESSAGES;
import io.undertow.security.api.SessionNonceManager;
import io.undertow.server.HttpServerExchange;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Random;
import java.util.Set;
import java.util.WeakHashMap;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;
import org.xnio.XnioExecutor;
import org.xnio.XnioExecutor.Key;
import org.xnio.XnioIoThread;
import io.undertow.util.FlexBase64;
import io.undertow.util.WorkerUtils;
/**
* A default {@link io.undertow.security.api.NonceManager} implementation to provide reasonable single host management of nonces.
*
* This {@link io.undertow.security.api.NonceManager} manages nonces in two groups, the first is the group that are allocated to new requests, this group
* is a problem as we want to be able to limit how many we distribute so we don't have a DOS storing too many but we also don't
* a high number of requests to to push the other valid nonces out faster than they can be used.
*
* The second group is the set of nonces actively in use - these should be maintained as we can also maintain the nonce count
* and even track the next nonce once invalid.
*
* Maybe group one should be a timestamp and private key hashed together, if used with a nonce count they move to be tracked to
* ensure the same count is not used again - if successfully used without a nonce count add to a blacklist until expiration? A
* nonce used without a nonce count will essentially be single use with each request getting a new nonce.
*
* @author Darran Lofthouse
*/
public class SimpleNonceManager implements SessionNonceManager {
private static final String DEFAULT_HASH_ALG = "MD5";
/**
* List of invalid nonces, this list contains the nonces that have been used without a nonce count.
*
* In that situation they are considered single use and must not be used again.
*/
private final Set invalidNonces = Collections.synchronizedSet(new HashSet());
/**
* Map of known currently valid nonces, a SortedMap is used to order the nonces by their creation time stamp allowing a
* simple iteration over the keys to identify expired nonces.
*/
private final Map knownNonces = Collections.synchronizedMap(new HashMap());
/**
* A WeakHashMap to map expired nonces to their replacement nonce. For an item to be added to this Collection the value will
* have been removed from the knownNonces map.
*
* A replacement nonce will have been added to knownNonces that references the key used here - once the replacement nonce is
* removed from knownNonces then the key will be eligible for garbage collection allowing it to be removed from this map as
* well.
*
* The value in this Map is a plain String, this is to avoid inadvertently creating a long term reference to the key we
* expect to be garbage collected at some point in the future.
*/
private final Map forwardMapping = Collections.synchronizedMap(new WeakHashMap());
private final String secret;
private final String hashAlg;
private final int hashLength;
/**
* After a nonce is issued the first authentication response MUST be received within 5 minutes.
*/
private static final long firstUseTimeOut = 5 * 60 * 1000;
/**
* Overall a nonce is valid from 15 minutes from first being issued, if used after this then a new nonce will be issued.
*/
private static final long overallTimeOut = 15 * 60 * 1000;
/**
* A previously used nonce will be allowed to remain in the knownNonces list for up to 5 minutes.
*
* The nonce will be accepted during this 5 minute window but will immediately be replaced causing any additional requests
* to be forced to use the new nonce.
*
* This is primarily for session based digests where loosing the cached session key would be bad.
*/
private static final long cacheTimePostExpiry = 5 * 60 * 1000;
public SimpleNonceManager() {
this(DEFAULT_HASH_ALG);
}
public SimpleNonceManager(final String hashAlg) {
// Verify it is a valid algorithm (at least for now)
MessageDigest digest = getDigest(hashAlg);
this.hashAlg = hashAlg;
this.hashLength = digest.getDigestLength();
// Create a new secret only valid within this NonceManager instance.
Random rand = new SecureRandom();
byte[] secretBytes = new byte[32];
rand.nextBytes(secretBytes);
secret = FlexBase64.encodeString(digest.digest(secretBytes), false);
}
private MessageDigest getDigest(final String hashAlg) {
try {
return MessageDigest.getInstance(hashAlg);
} catch (NoSuchAlgorithmException e) {
throw MESSAGES.hashAlgorithmNotFound(hashAlg);
}
}
/**
*
* @see io.undertow.security.api.NonceManager#nextNonce(java.lang.String, io.undertow.server.HttpServerExchange)
*/
public String nextNonce(String lastNonce, HttpServerExchange exchange) {
if (lastNonce == null) {
return createNewNonceString();
}
if (invalidNonces.contains(lastNonce)) {
// The nonce supplied has already been used.
return createNewNonceString();
}
String nonce = lastNonce;
// Loop the forward mappings.
synchronized (forwardMapping) {
NonceHolder holder = new NonceHolder(lastNonce);
while (forwardMapping.containsKey(holder)) {
nonce = forwardMapping.get(holder);
// The final NonceHolder will then be used if a forwardMapping needs to be set.
holder = new NonceHolder(nonce);
}
synchronized (knownNonces) {
Nonce value = knownNonces.get(nonce);
if (value == null) {
// Not a likely scenario but if this occurs then most likely the nonce mapped to has also expired so we will
// just send a new nonce.
nonce = createNewNonceString();
} else {
long now = System.currentTimeMillis();
// The cacheTimePostExpiry is not included here as this is our opportunity to inform the client to use a
// replacement nonce without a stale round trip.
long earliestAccepted = now - firstUseTimeOut;
if (value.timeStamp < earliestAccepted || value.timeStamp > now) {
Nonce replacement = createNewNonce(holder);
if (value.executorKey != null) {
// The outcome doesn't matter - if we have the value we have all we need.
value.executorKey.remove();
}
nonce = replacement.nonce;
// Create a record of the forward mapping so if any requests do need to be marked stale they can be
// pointed towards the correct nonce to use.
forwardMapping.put(holder, nonce);
// Bring over any existing session key.
replacement.setSessionKey(value.getSessionKey());
// At this point we will not accept the nonce again so remove it from the list of known nonces but do
// register the replacement.
knownNonces.remove(holder.nonce);
// There are two reasons for registering the replacement 1 - to preserve any session key, 2 - To keep a
// reference to the now invalid key so it
// can be used as a key in a weak hash map.
knownNonces.put(nonce, replacement);
earliestAccepted = now - (overallTimeOut + cacheTimePostExpiry);
long timeTillExpiry = replacement.timeStamp - earliestAccepted;
replacement.executorKey = WorkerUtils.executeAfter(exchange.getIoThread(), new KnownNonceCleaner(nonce), timeTillExpiry,
TimeUnit.MILLISECONDS);
}
}
}
}
return nonce;
}
private String createNewNonceString() {
return createNewNonce(null).nonce;
}
private Nonce createNewNonce(NonceHolder previousNonce) {
byte[] prefix = new byte[8];
// A pseudo-random generator for creating the nonces, a secure random is not required here as this is used purely to
// minimise the chance of collisions should two nonces be generated at exactly the same time.
ThreadLocalRandom.current().nextBytes(prefix);
long timeStamp = System.currentTimeMillis();
byte[] now = Long.toString(timeStamp).getBytes(StandardCharsets.UTF_8);
String nonce = createNonce(prefix, now);
return new Nonce(nonce, timeStamp, previousNonce);
}
/**
*
* @see io.undertow.security.api.NonceManager#validateNonce(java.lang.String, int, io.undertow.server.HttpServerExchange)
*/
@Override
public boolean validateNonce(String nonce, int nonceCount, HttpServerExchange exchange) {
if (nonceCount < 0) {
if (invalidNonces.contains(nonce)) {
// Without a nonce count the nonce is only usable once.
return false;
}
// Not already known so will drop into first use validation.
} else if (knownNonces.containsKey(nonce)) {
// At this point we need to validate that the nonce is still within it's time limits,
// If a new nonce had been selected then a known nonce would not have been found.
// The nonce will also have it's nonce count checked.
return validateNonceWithCount(new Nonce(nonce), nonceCount, exchange.getIoThread());
} else if (forwardMapping.containsKey(new NonceHolder(nonce))) {
// We could have let this drop through as the next validation would fail anyway but
// why waste the time if we already know a replacement nonce has been issued.
return false;
}
// This is not a nonce currently known to us so start the validation process.
Nonce value = verifyUnknownNonce(nonce, nonceCount);
if (value == null) {
return false;
}
long now = System.currentTimeMillis();
// NOTE - This check is for the first use, overall validity is checked in validateNonceWithCount.
long earliestAccepted = now - firstUseTimeOut;
if (value.timeStamp < earliestAccepted || value.timeStamp > now) {
// The embedded timestamp is either expired or somehow is after now.
return false;
}
if (nonceCount < 0) {
// Allow a single use but reject all further uses.
return addInvalidNonce(value, exchange.getIoThread());
} else {
return validateNonceWithCount(value, nonceCount, exchange.getIoThread());
}
}
private boolean validateNonceWithCount(Nonce nonce, int nonceCount, final XnioIoThread executor) {
// This point could have been reached either because the knownNonces map contained the key or because
// it didn't and a count was supplied - either way need to double check the contents of knownNonces once
// the lock is in place.
synchronized (knownNonces) {
Nonce value = knownNonces.get(nonce.nonce);
long now = System.currentTimeMillis();
// For the purpose of this validation we also add the cacheTimePostExpiry - when nextNonce is subsequently
// called it will decide if we are in the interval to replace the nonce.
long earliestAccepted = now - (overallTimeOut + cacheTimePostExpiry);
if (value == null) {
if (nonce.timeStamp < 0) {
// Means it was in there, now it isn't - most likely a timestamp expiration mid check - abandon validation.
return false;
}
if (nonce.timeStamp > earliestAccepted && nonce.timeStamp <= now) {
knownNonces.put(nonce.nonce, nonce);
long timeTillExpiry = nonce.timeStamp - earliestAccepted;
nonce.executorKey = WorkerUtils.executeAfter(executor, new KnownNonceCleaner(nonce.nonce), timeTillExpiry,
TimeUnit.MILLISECONDS);
return true;
}
return false;
} else {
// We have it, just need to verify that it has not expired and that the nonce key is valid.
if (value.timeStamp < earliestAccepted || value.timeStamp > now) {
// The embedded timestamp is either expired or somehow is after now!!
return false;
}
if (value.getMaxNonceCount() < nonceCount) {
value.setMaxNonceCount(nonceCount);
return true;
}
return false;
}
}
}
private boolean addInvalidNonce(final Nonce nonce, final XnioExecutor executor) {
long now = System.currentTimeMillis();
long invalidBefore = now - firstUseTimeOut;
long timeTillInvalid = nonce.timeStamp - invalidBefore;
if (timeTillInvalid > 0) {
if (invalidNonces.add(nonce.nonce)) {
executor.executeAfter(new InvalidNonceCleaner(nonce.nonce), timeTillInvalid, TimeUnit.MILLISECONDS);
return true;
} else {
return false;
}
} else {
// So close to expiring any record of this nonce being used could have been cleared so
// don't take a chance and just say no.
return false;
}
}
/**
* Verify a previously unknown nonce and return the {@link NonceKey} representation for the nonce.
*
* Later when a nonce is re-used we can match based on the String alone - the information embedded within the nonce will be
* cached with it.
*
* This stage of the verification simply extracts the prefix and the embedded timestamp and recreates a new hashed and
* Base64 nonce based on the local secret - if the newly generated nonce matches the supplied one we accept it was created
* by this nonce manager.
*
* This verification does not validate that the timestamp is within a valid time period.
*
* @param nonce -
* @return
*/
private Nonce verifyUnknownNonce(final String nonce, final int nonceCount) {
byte[] complete;
int offset;
int length;
try {
ByteBuffer decode = FlexBase64.decode(nonce);
complete = decode.array();
offset = decode.arrayOffset();
length = decode.limit() - offset;
} catch (IOException e) {
throw MESSAGES.invalidBase64Token(e);
}
int timeStampLength = complete[offset + 8];
// A sanity check to try and verify the sizes we expect from the arrays are correct.
if (hashLength > 0) {
int expectedLength = 9 + timeStampLength + hashLength;
if (length != expectedLength) {
throw MESSAGES.invalidNonceReceived();
} else if (timeStampLength + 1 >= length)
throw MESSAGES.invalidNonceReceived();
}
byte[] prefix = new byte[8];
System.arraycopy(complete, offset, prefix, 0, 8);
byte[] timeStampBytes = new byte[timeStampLength];
System.arraycopy(complete, offset + 9, timeStampBytes, 0, timeStampBytes.length);
String expectedNonce = createNonce(prefix, timeStampBytes);
if (expectedNonce.equals(nonce)) {
try {
long timeStamp = Long.parseLong(new String(timeStampBytes, StandardCharsets.UTF_8));
return new Nonce(expectedNonce, timeStamp, nonceCount);
} catch (NumberFormatException dropped) {
}
}
return null;
}
private String createNonce(final byte[] prefix, final byte[] timeStamp) {
byte[] hashedPart = generateHash(prefix, timeStamp);
byte[] complete = new byte[9 + timeStamp.length + hashedPart.length];
System.arraycopy(prefix, 0, complete, 0, 8);
complete[8] = (byte) timeStamp.length;
System.arraycopy(timeStamp, 0, complete, 9, timeStamp.length);
System.arraycopy(hashedPart, 0, complete, 9 + timeStamp.length, hashedPart.length);
return FlexBase64.encodeString(complete, false);
}
private byte[] generateHash(final byte[] prefix, final byte[] timeStamp) {
MessageDigest digest = getDigest(hashAlg);
digest.update(prefix);
digest.update(timeStamp);
return digest.digest(secret.getBytes(StandardCharsets.UTF_8));
}
public void associateHash(String nonce, byte[] hash) {
// TODO Auto-generated method stub
}
public byte[] lookupHash(String nonce) {
// TODO Auto-generated method stub
return null;
}
/**
* A simple wrapper around a nonce to allow it to be used as a key in a weak map.
*/
private static class NonceHolder {
private final String nonce;
private NonceHolder(final String nonce) {
if (nonce == null) {
throw new NullPointerException("nonce must not be null.");
}
this.nonce = nonce;
}
@Override
public int hashCode() {
return nonce.hashCode();
}
@Override
public boolean equals(Object obj) {
return (obj instanceof NonceHolder) ? nonce.equals(((NonceHolder) obj).nonce) : false;
}
}
/**
* The state associated with a nonce.
*
* A NonceKey for a preciously valid nonce is also referenced, this is so that a WeakHashMap can be used to maintain a
* mapping from the original NonceKey to the new nonce value.
*/
private static class Nonce {
private final String nonce;
private final long timeStamp;
// TODO we will also add a mechanism to track the gaps as the only restriction is that a NC can only be used one.
private int maxNonceCount;
// We keep this as it is used in the weak hash map as a forward mapping as long as the nonce to map to is still alive.
@SuppressWarnings("unused")
private final NonceHolder previousNonce;
private byte[] sessionKey;
private Key executorKey;
private Nonce(final String nonce) {
this(nonce, -1, -1);
}
private Nonce(final String nonce, final long timeStamp, final int initialNC) {
this(nonce, timeStamp, initialNC, null);
}
private Nonce(final String nonce, final long timeStamp, final NonceHolder previousNonce) {
this(nonce, timeStamp, -1, previousNonce);
}
private Nonce(final String nonce, final long timeStamp, final int initialNC, final NonceHolder previousNonce) {
this.nonce = nonce;
this.timeStamp = timeStamp;
this.maxNonceCount = initialNC;
this.previousNonce = previousNonce;
}
byte[] getSessionKey() {
return sessionKey;
}
void setSessionKey(final byte[] sessionKey) {
this.sessionKey = sessionKey;
}
int getMaxNonceCount() {
return maxNonceCount;
}
void setMaxNonceCount(int maxNonceCount) {
this.maxNonceCount = maxNonceCount;
}
}
private class InvalidNonceCleaner implements Runnable {
private final String nonce;
private InvalidNonceCleaner(final String nonce) {
if (nonce == null) {
throw new NullPointerException("nonce must not be null.");
}
this.nonce = nonce;
}
public void run() {
invalidNonces.remove(nonce);
}
}
private class KnownNonceCleaner implements Runnable {
private final String nonce;
private KnownNonceCleaner(final String nonce) {
if (nonce == null) {
throw new NullPointerException("nonce must not be null.");
}
this.nonce = nonce;
}
public void run() {
knownNonces.remove(nonce);
}
}
}
