gristlabs_grist-core/app/server/lib/BootProbes.ts
Leslie H 24ce54b586
Improve session ID security (#1059)
Follow-up of #994. This PR revises the session ID generation logic to improve security in the absence of a secure session secret. It also adds a section in the admin panel "security" section to nag system admins when GRIST_SESSION_SECRET is not set.

Following is an excerpt from internal conversation.

TL;DR: Grist's current implementation generates semi-secure session IDs and uses a publicly known default signing key to sign them when the environment variable GRIST_SESSION_SECRET is not set. This PR generates cryptographically secure session IDs to dismiss security concerns around an insecure signing key, and encourages system admins to configure their own signing key anyway.

> The session secret is required by expressjs/session to sign its session IDs. It's designed as an extra protection against session hijacking by randomly guessing session IDs and hitting a valid one. While it is easy to encourage users to set a distinct session secret, this is unnecessary if session IDs are generated in a cryptographically secure way. As of now Grist uses version 4 UUIDs as session IDs (see app/server/lib/gristSessions.ts - it uses shortUUID.generate which invokes uuid.v4 under the hood). These contain 122 bits of entropy, technically insufficient to be considered cryptographically secure. In practice, this is never considered a real vulnerability. To compare, RSA2048 is still very commonly used in web servers, yet it only has 112 bits of security (>=128 bits = "secure", rule of thumb in cryptography). But for peace of mind I propose using crypto.getRandomValues to generate real 128-bit random values. This should render session ID signing unnecessary and hence dismiss security concerns around an insecure signing key.
2024-06-25 15:43:25 -04:00

303 lines
7.8 KiB
TypeScript

import { ApiError } from 'app/common/ApiError';
import { BootProbeIds, BootProbeResult } from 'app/common/BootProbe';
import { removeTrailingSlash } from 'app/common/gutil';
import { expressWrap, jsonErrorHandler } from 'app/server/lib/expressWrap';
import { GristServer } from 'app/server/lib/GristServer';
import * as express from 'express';
import WS from 'ws';
import fetch from 'node-fetch';
import { DEFAULT_SESSION_SECRET } from 'app/server/lib/coreCreator';
/**
* Self-diagnostics useful when installing Grist.
*/
export class BootProbes {
// List of probes.
public _probes = new Array<Probe>();
// Probes indexed by id.
public _probeById = new Map<string, Probe>();
public constructor(private _app: express.Application,
private _server: GristServer,
private _base: string,
private _middleware: express.Handler[] = []) {
this._addProbes();
}
public addEndpoints() {
// Return a list of available probes.
this._app.use(`${this._base}/probes$`,
...this._middleware,
expressWrap(async (_, res) => {
res.json({
'probes': this._probes.map(probe => {
return { id: probe.id, name: probe.name };
}),
});
}));
// Return result of running an individual probe.
this._app.use(`${this._base}/probes/:probeId`,
...this._middleware,
expressWrap(async (req, res) => {
const probe = this._probeById.get(req.params.probeId);
if (!probe) {
throw new ApiError('unknown probe', 400);
}
const result = await probe.apply(this._server, req);
res.json(result);
}));
// Fall-back for errors.
this._app.use(`${this._base}/probes`, jsonErrorHandler);
}
private _addProbes() {
this._probes.push(_homeUrlReachableProbe);
this._probes.push(_statusCheckProbe);
this._probes.push(_userProbe);
this._probes.push(_bootProbe);
this._probes.push(_hostHeaderProbe);
this._probes.push(_sandboxingProbe);
this._probes.push(_authenticationProbe);
this._probes.push(_webSocketsProbe);
this._probes.push(_sessionSecretProbe);
this._probeById = new Map(this._probes.map(p => [p.id, p]));
}
}
/**
* An individual probe has an id, a name, an optional description,
* and a method that returns a probe result.
*/
export interface Probe {
id: BootProbeIds;
name: string;
description?: string;
apply: (server: GristServer, req: express.Request) => Promise<BootProbeResult>;
}
const _homeUrlReachableProbe: Probe = {
id: 'reachable',
name: 'Is home page available at expected URL',
apply: async (server, req) => {
const url = server.getHomeInternalUrl();
const details: Record<string, any> = {
url,
};
try {
const resp = await fetch(url);
details.status = resp.status;
if (resp.status !== 200) {
throw new ApiError(await resp.text(), resp.status);
}
return {
status: 'success',
details,
};
} catch (e) {
return {
details: {
...details,
error: String(e),
},
status: 'fault',
};
}
}
};
const _webSocketsProbe: Probe = {
id: 'websockets',
name: 'Can we open a websocket with the server',
apply: async (server, req) => {
return new Promise((resolve) => {
const url = new URL(server.getHomeUrl(req));
url.protocol = (url.protocol === 'https:') ? 'wss:' : 'ws:';
const ws = new WS.WebSocket(url.href);
const details: Record<string, any> = {
url,
};
ws.on('open', () => {
ws.send('{"msg": "Just nod if you can hear me."}');
resolve({
status: 'success',
details,
});
ws.close();
});
ws.on('error', (ev) => {
details.error = ev.message;
resolve({
status: 'fault',
details,
});
ws.close();
});
});
}
};
const _statusCheckProbe: Probe = {
id: 'health-check',
name: 'Is an internal health check passing',
apply: async (server, req) => {
const baseUrl = server.getHomeInternalUrl();
const url = new URL(baseUrl);
url.pathname = removeTrailingSlash(url.pathname) + '/status';
const details: Record<string, any> = {
url: url.href,
};
try {
const resp = await fetch(url);
details.status = resp.status;
if (resp.status !== 200) {
throw new Error(`Failed with status ${resp.status}`);
}
const txt = await resp.text();
if (!txt.includes('is alive')) {
throw new Error(`Failed, page has unexpected content`);
}
return {
status: 'success',
details,
};
} catch (e) {
return {
details: {
...details,
error: String(e),
},
status: 'fault',
};
}
},
};
const _userProbe: Probe = {
id: 'system-user',
name: 'Is the system user following best practice',
apply: async () => {
const details = {
uid: process.getuid ? process.getuid() : 'unavailable',
};
if (process.getuid && process.getuid() === 0) {
return {
details,
verdict: 'User appears to be root (UID 0)',
status: 'warning',
};
} else {
return {
status: 'success',
details,
};
}
},
};
const _bootProbe: Probe = {
id: 'boot-page',
name: 'Is the boot page adequately protected',
apply: async (server) => {
const bootKey = server.getBootKey() || '';
const hasBoot = Boolean(bootKey);
const details: Record<string, any> = {
bootKeySet: hasBoot,
};
if (!hasBoot) {
return { status: 'success', details };
}
details.bootKeyLength = bootKey.length;
if (bootKey.length < 10) {
return {
verdict: 'Boot key length is shorter than 10.',
details,
status: 'fault',
};
}
return {
verdict: 'Boot key ideally should be removed after installation.',
details,
status: 'warning',
};
},
};
/**
* Based on:
* https://github.com/gristlabs/grist-core/issues/228#issuecomment-1803304438
*
* When GRIST_SERVE_SAME_ORIGIN is set, requests arriving to Grist need
* to have an accurate Host header.
*/
const _hostHeaderProbe: Probe = {
id: 'host-header',
name: 'Does the host header look correct',
apply: async (server, req) => {
const host = req.header('host');
const url = new URL(server.getHomeUrl(req));
const details = {
homeUrlHost: url.hostname,
headerHost: host,
};
if (url.hostname === 'localhost') {
return {
status: 'none',
details,
};
}
if (String(url.hostname).toLowerCase() !== String(host).toLowerCase()) {
return {
details,
status: 'hmm',
};
}
return {
status: 'none',
details,
};
},
};
const _sandboxingProbe: Probe = {
id: 'sandboxing',
name: 'Is document sandboxing effective',
apply: async (server, req) => {
const details = server.getSandboxInfo();
return {
status: (details?.configured && details?.functional) ? 'success' : 'fault',
details,
};
},
};
const _authenticationProbe: Probe = {
id: 'authentication',
name: 'Authentication system',
apply: async(server, req) => {
const loginSystemId = server.getInfo('loginMiddlewareComment');
return {
status: (loginSystemId != undefined) ? 'success' : 'fault',
details: {
loginSystemId,
}
};
},
};
const _sessionSecretProbe: Probe = {
id: 'session-secret',
name: 'Session secret',
apply: async(server, req) => {
const usingDefaultSessionSecret = server.create.sessionSecret() === DEFAULT_SESSION_SECRET;
return {
status: usingDefaultSessionSecret ? 'warning' : 'success',
details: {
"GRIST_SESSION_SECRET": process.env.GRIST_SESSION_SECRET ? "set" : "not set",
}
};
},
};