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fix: encrypted session race condition #177

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Merged
merged 1 commit into from
Jul 10, 2025
Merged

fix: encrypted session race condition #177

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128 changes: 52 additions & 76 deletions server/encrypted-session.js
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Original file line number Diff line number Diff line change
Expand Up @@ -49,63 +49,47 @@ async function encryptedSession(fastify) {
},
});

fastify.addHook('onRequest', (request, _reply, next) => {
const userEncryptionKey = getUserEncryptionKeyFromUserCookie(request);
if (!userEncryptionKey) {
request.log.info({ plugin: 'encrypted-session' }, 'user-side encryption key not found, creating new one');

let newEncryptionKey = generateSecureEncryptionKey();
setUserEncryptionKeyIntoUserCookie(request, newEncryptionKey);
request[REQUEST_DECORATOR] = createStore();
newEncryptionKey = undefined;
} else {
request.log.info({ plugin: 'encrypted-session' }, 'user-side encryption key found, using existing one');

const loadedEncryptionKey = Buffer.from(userEncryptionKey, 'base64');

const encryptedStore = request.session.get('encryptedStore');
if (encryptedStore) {
try {
const { cipherText, iv, tag } = encryptedStore;

const decryptedCypherText = decryptSymetric(cipherText, iv, tag, loadedEncryptionKey);
const decryptedStore = JSON.parse(decryptedCypherText);
request[REQUEST_DECORATOR] = createStore(decryptedStore);
} catch (error) {
request.log.error({ plugin: 'encrypted-session' }, 'Failed to parse encrypted session store', error);
request[REQUEST_DECORATOR] = createStore();
}
} else {
// we could not parse the encrypted store, so we create a new one and it would overwrite the previously stored store.
request.log.info({ plugin: 'encrypted-session' }, 'No encrypted store found, creating new empty store');
request[REQUEST_DECORATOR] = createStore();
}
await fastify.decorateRequest(REQUEST_DECORATOR, {
getter() {
return createStore(this);
}

next();
});
}

//TODO maybe move to onResponse after res is send. Lifecycle Doc https://fastify.dev/docs/latest/Reference/Lifecycle/
// onSend is called before the response is send. Here we take encrypt the Session object and store it in the fastify-session.
// Then we also want to make sure the unencrypted object is removed from memory
fastify.addHook('onSend', async (request, _reply, payload) => {
const encryptionKey = Buffer.from(getUserEncryptionKeyFromUserCookie(request), 'base64');
if (!encryptionKey) {
// if no encryption key is found in the secure session, we cannot encrypt the store. This should not happen since an encrption key is generated when the request arrived
request.log.error(
{ plugin: 'encrypted-session' },
'No encryption key found in secure session, cannot encrypt store',
);
throw new Error('No encryption key found in secure session, cannot encrypt store');
}
export default fp(encryptedSession);

//we store everything in one value in the session, that might be problematic for future redis with expiration times per key. we might want to split this
const stringifiedData = request[REQUEST_DECORATOR].stringify();
const { cipherText, iv, tag } = encryptSymetric(stringifiedData, encryptionKey);
function createStore(request) {
let unencryptedStore = {}; // Private variable

//read previous values
let userEncryptionKey = getUserEncryptionKeyFromUserCookie(request);
if (!userEncryptionKey) {
request.log.info({ plugin: 'encrypted-session' }, 'user-side encryption key not found, creating new one');

//remove unencrypted data from memory
delete request[REQUEST_DECORATOR];
request[REQUEST_DECORATOR] = null;
userEncryptionKey = generateSecureEncryptionKey();
setUserEncryptionKeyIntoUserCookie(request, userEncryptionKey);
}

const loadedEncryptionKey = Buffer.from(userEncryptionKey, 'base64');
const encryptedStore = request.session.get('encryptedStore');
if (encryptedStore) {
try {
const { cipherText, iv, tag } = encryptedStore;

const decryptedCypherText = decryptSymetric(cipherText, iv, tag, loadedEncryptionKey);
const decryptedStore = JSON.parse(decryptedCypherText);
unencryptedStore = decryptedStore;
} catch (error) {
request.log.error({ plugin: 'encrypted-session' }, 'Failed to parse encrypted session store', error);
}
} else {
// we could not parse the encrypted store, so we create a new one and it would overwrite the previously stored store.
request.log.info({ plugin: 'encrypted-session' }, 'No encrypted store found, creating new empty store');
}

async function save() {
const stringifiedData = JSON.stringify(unencryptedStore);
const { cipherText, iv, tag } = encryptSymetric(stringifiedData, loadedEncryptionKey);

request.session.set('encryptedStore', {
cipherText,
Expand All @@ -114,46 +98,38 @@ async function encryptedSession(fastify) {
});
await request.session.save();
request.log.info('store encrypted and set into request.session.encryptedStore');

return payload;
});

function getUserEncryptionKeyFromUserCookie(request) {
return request[ENCRYPTED_COOKIE_REQUEST_DECORATOR].get(ENCRYPTED_COOKIE_KEY_ENCRYPTION_KEY);
}

function setUserEncryptionKeyIntoUserCookie(request, key) {
request[ENCRYPTED_COOKIE_REQUEST_DECORATOR].set(ENCRYPTED_COOKIE_KEY_ENCRYPTION_KEY, key.toString('base64'));
}
}

export default fp(encryptedSession);

// use a closure to encapsulate the session data so noone can reference it and we are the only ones keeping a reference
function createStore(previousValue) {
let unencryptedStore = {}; // Private variable
if (previousValue) {
unencryptedStore = previousValue;
}
return {
set(key, value) {
async set(key, value) {
unencryptedStore[key] = value;
await save()
},
get(key) {
return unencryptedStore[key];
},
delete(key) {
async delete(key) {
delete unencryptedStore[key];
await save()
},
stringify() {
return JSON.stringify(unencryptedStore);
print() {
console.log("printing", unencryptedStore)
},
clear() {
async clear() {
unencryptedStore = {}; // Clear all data
await save()
},
};
}

function getUserEncryptionKeyFromUserCookie(request) {
return request[ENCRYPTED_COOKIE_REQUEST_DECORATOR].get(ENCRYPTED_COOKIE_KEY_ENCRYPTION_KEY);
}

function setUserEncryptionKeyIntoUserCookie(request, key) {
request[ENCRYPTED_COOKIE_REQUEST_DECORATOR].set(ENCRYPTED_COOKIE_KEY_ENCRYPTION_KEY, key.toString('base64'));
}

// generates a secure encryption key for aes-256-gcm.
// Returns a buffer of 32 bytes (256 bits).
function generateSecureEncryptionKey() {
Expand Down
8 changes: 4 additions & 4 deletions server/plugins/auth-utils.js
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@ async function authUtilsPlugin(fastify) {
};
});

fastify.decorate('prepareOidcLoginRedirect', (request, oidcConfig, authorizationEndpoint, stateKey) => {
fastify.decorate('prepareOidcLoginRedirect', async (request, oidcConfig, authorizationEndpoint, stateKey) => {
if (stateKey === undefined) {
stateKey = 'oauthState';
}
Expand All @@ -88,16 +88,16 @@ async function authUtilsPlugin(fastify) {
request.log.error(`Invalid redirectTo: "${redirectTo}".`);
throw new AuthenticationError('Invalid redirectTo.');
}
request.encryptedSession.set('postLoginRedirectRoute', redirectTo);
await request.encryptedSession.set('postLoginRedirectRoute', redirectTo);

const { clientId, redirectUri, scopes } = oidcConfig;

const state = crypto.randomBytes(16).toString('hex');
const codeVerifier = crypto.randomBytes(32).toString('base64url');
const codeChallenge = crypto.createHash('sha256').update(codeVerifier).digest('base64url');

request.encryptedSession.set(stateKey, state);
request.encryptedSession.set('codeVerifier', codeVerifier);
await request.encryptedSession.set(stateKey, state);
await request.encryptedSession.set('codeVerifier', codeVerifier);
request.log.info(
{
stateSet: Boolean(state),
Expand Down
14 changes: 7 additions & 7 deletions server/plugins/http-proxy.js
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ function proxyPlugin(fastify) {
const refreshToken = request.encryptedSession.get(keyRefreshToken);
if (!refreshToken) {
request.log.error('Missing refresh token; deleting encryptedSession.');
request.encryptedSession.clear(); //TODO: also clear user encrpytion key?
await request.encryptedSession.clear(); //TODO: also clear user encrpytion key?
return reply.unauthorized('Session expired without token refresh capability.');
}

Expand All @@ -61,23 +61,23 @@ function proxyPlugin(fastify) {
);
if (!refreshedTokenData || !refreshedTokenData.accessToken) {
request.log.error('Token refresh failed (no access token); deleting session.');
request.encryptedSession.clear(); //TODO: also clear user encrpytion key?
await request.encryptedSession.clear(); //TODO: also clear user encrpytion key?
return reply.unauthorized('Session expired and token refresh failed.');
}

request.log.info('Token refresh successful; updating the session.');

request.encryptedSession.set(keyAccessToken, refreshedTokenData.accessToken);
await request.encryptedSession.set(keyAccessToken, refreshedTokenData.accessToken);
if (refreshedTokenData.refreshToken) {
request.encryptedSession.set(keyRefreshToken, refreshedTokenData.refreshToken);
await request.encryptedSession.set(keyRefreshToken, refreshedTokenData.refreshToken);
} else {
request.encryptedSession.delete(keyRefreshToken);
await request.encryptedSession.delete(keyRefreshToken);
}
if (refreshedTokenData.expiresIn) {
const newExpiresAt = Date.now() + refreshedTokenData.expiresIn * 1000;
request.encryptedSession.set(keyTokenExpiresAt, newExpiresAt);
await request.encryptedSession.set(keyTokenExpiresAt, newExpiresAt);
} else {
request.encryptedSession.delete(keyTokenExpiresAt);
await request.encryptedSession.delete(keyTokenExpiresAt);
}

request.log.info('Token refresh successful and session updated; continuing with the HTTP request.');
Expand Down
12 changes: 6 additions & 6 deletions server/routes/auth-mcp.js
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ async function authPlugin(fastify) {
fastify.decorate('mcpIssuerConfiguration', mcpIssuerConfiguration);

fastify.get('/auth/mcp/login', async function (req, reply) {
const redirectUri = fastify.prepareOidcLoginRedirect(
const redirectUri = await fastify.prepareOidcLoginRedirect(
req,
{
clientId: OIDC_CLIENT_ID_MCP,
Expand All @@ -38,13 +38,13 @@ async function authPlugin(fastify) {
stateSessionKey,
);

req.encryptedSession.set('mcp_accessToken', callbackResult.accessToken);
req.encryptedSession.set('mcp_refreshToken', callbackResult.refreshToken);
await req.encryptedSession.set('mcp_accessToken', callbackResult.accessToken);
await req.encryptedSession.set('mcp_refreshToken', callbackResult.refreshToken);

if (callbackResult.expiresAt) {
req.encryptedSession.set('mcp_tokenExpiresAt', callbackResult.expiresAt);
await req.encryptedSession.set('mcp_tokenExpiresAt', callbackResult.expiresAt);
} else {
req.encryptedSession.delete('mcp_tokenExpiresAt');
await req.encryptedSession.delete('mcp_tokenExpiresAt');
}

return reply.redirect(POST_LOGIN_REDIRECT + callbackResult.postLoginRedirectRoute);
Expand All @@ -62,7 +62,7 @@ async function authPlugin(fastify) {
const accessToken = req.encryptedSession.get('mcp_accessToken');

const isAuthenticated = Boolean(accessToken);
reply.send({ isAuthenticated });
return reply.send({ isAuthenticated });
});
}

Expand Down
19 changes: 9 additions & 10 deletions server/routes/auth-onboarding.js
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ async function authPlugin(fastify) {
fastify.decorate('issuerConfiguration', issuerConfiguration);

fastify.get('/auth/onboarding/login', async function (req, reply) {
const redirectUri = fastify.prepareOidcLoginRedirect(
const redirectUri = await fastify.prepareOidcLoginRedirect(
req,
{
clientId: OIDC_CLIENT_ID,
Expand All @@ -37,14 +37,14 @@ async function authPlugin(fastify) {
stateSessionKey,
);

req.encryptedSession.set('onboarding_accessToken', callbackResult.accessToken);
req.encryptedSession.set('onboarding_refreshToken', callbackResult.refreshToken);
req.encryptedSession.set('onboarding_userInfo', callbackResult.userInfo);
await req.encryptedSession.set('onboarding_accessToken', callbackResult.accessToken);
await req.encryptedSession.set('onboarding_refreshToken', callbackResult.refreshToken);
await req.encryptedSession.set('onboarding_userInfo', callbackResult.userInfo);

if (callbackResult.expiresAt) {
req.encryptedSession.set('onboarding_tokenExpiresAt', callbackResult.expiresAt);
await req.encryptedSession.set('onboarding_tokenExpiresAt', callbackResult.expiresAt);
} else {
req.encryptedSession.delete('onboarding_tokenExpiresAt');
await req.encryptedSession.delete('onboarding_tokenExpiresAt');
}

return reply.redirect(POST_LOGIN_REDIRECT + callbackResult.postLoginRedirectRoute);
Expand All @@ -64,14 +64,13 @@ async function authPlugin(fastify) {

const isAuthenticated = Boolean(accessToken);
const user = isAuthenticated ? userInfo : null;

reply.send({ isAuthenticated, user });
return reply.send({ isAuthenticated, user });
});

fastify.post('/auth/logout', async function (req, reply) {
// TODO: Idp sign out flow
req.encryptedSession.clear();
reply.send({ message: 'Logged out' });
await req.encryptedSession.clear();
return reply.send({ message: 'Logged out' });
});
}

Expand Down
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