feat(hardening): M-Hard 1-5 — crypto, auth, rate limit, fingerprints, rotation

M-Hard 1: Cryptographic Hardening
- constantTimeEqual, zeroize, randomUint32 on CryptoProvider
- Fix Math.random() → crypto.randomUint32() for registrationId
- Zero message keys and chain keys after use in ratchet.ts
- Constant-time trust comparison in MemoryStorage + SQLiteStorage
- Timing variance test catches early-exit regressions

M-Hard 2: Self-Authenticated Prekey Server
- Ed25519 signature verification on all write routes
- signPayload/verifyPayload with canonical JSON, ±5 min replay window
- Address validation (NFKC, alphanumeric + :_-.)
- Global ShadeError → HTTP status mapping
- ShadeFetchTransport signs requests when signingPrivateKey provided
- Anonymous bundle fetches still allowed (read-only)

M-Hard 3: Rate Limiting + DoS Protection
- Token bucket rate limiter with pluggable store
- Per-route limits: register 5/h/IP, fetch 60/min/IP, replenish 10/min/id
- 64KB body size limit on POST
- Retry-After header on 429 responses

M-Hard 4: Auto-replenish + Fingerprints + Session Reset
- Safety numbers (12 groups × 5 digits, Signal-style)
- ensurePreKeyStock, resetSession, acceptIdentityChange
- verifyRemoteIdentity for out-of-band comparison

M-Hard 5: Identity Rotation with Grace Period
- rotateIdentity archives old identity, generates fresh signed prekey
- RetiredIdentity storage with addRetired/getRetired/pruneRetired
- 7-day default grace period for decrypting old sessions
- pruneExpiredIdentities for cleanup

M-Hard 8: Error Hierarchy
- New error types: Network, Storage, Validation, Timeout, RateLimit,
  Configuration, Unauthorized, Replay, IdentityRotation
- All errors have stable SHADE_* codes
- errorToHttpStatus for consistent HTTP mapping
- toJSON() for network serialization

188 tests passing, zero failures.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
2026-04-10 17:45:34 +02:00
parent 7d214dc614
commit 96a8c210b2
25 changed files with 1835 additions and 257 deletions

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@@ -1,3 +1,17 @@
/**
* Constant-time byte array comparison (standalone utility).
* Same semantics as CryptoProvider.constantTimeEqual but usable
* in contexts that don't have a provider instance.
*/
export function constantTimeEqual(a: Uint8Array, b: Uint8Array): boolean {
if (a.length !== b.length) return false;
let diff = 0;
for (let i = 0; i < a.length; i++) {
diff |= a[i]! ^ b[i]!;
}
return diff === 0;
}
/**
* CryptoProvider — platform-agnostic interface for all cryptographic primitives.
*
@@ -59,4 +73,26 @@ export interface CryptoProvider {
/** Generate cryptographically secure random bytes */
randomBytes(length: number): Uint8Array;
// ─── Hardening ─────────────────────────────────────────────
/**
* Constant-time byte array comparison. No early exit on mismatch.
* Use this for ALL comparisons involving secret data (keys, MACs, tokens).
* Returns false if lengths differ (timing leak on length is acceptable).
*/
constantTimeEqual(a: Uint8Array, b: Uint8Array): boolean;
/**
* Overwrite a buffer with zeros. Use after a key is no longer needed.
* Note: V8 may not actually zero the backing memory due to GC/optimization,
* but this is the best we can do in JS/TS without native bindings.
*/
zeroize(buf: Uint8Array): void;
/**
* Cryptographically secure random 32-bit unsigned integer.
* Use for registrationId, keyId generation, etc. (NEVER Math.random()).
*/
randomUint32(): number;
}

View File

@@ -1,63 +1,175 @@
/** Base class for all Shade errors */
/**
* Shade error hierarchy.
*
* All errors have:
* - `name`: class name for `instanceof` checks
* - `code`: stable string code for error mapping (e.g. HTTP status)
* - `toJSON()`: serializable form for network transmission
*/
export class ShadeError extends Error {
constructor(message: string) {
/** Stable error code for mapping to HTTP status or UI strings */
readonly code: string;
constructor(code: string, message: string) {
super(message);
this.name = 'ShadeError';
this.code = code;
}
toJSON(): { name: string; code: string; message: string } {
return { name: this.name, code: this.code, message: this.message };
}
}
/** Signature verification failed (e.g. invalid signed prekey) */
// ─── Crypto / Protocol Errors ────────────────────────────────
export class InvalidSignatureError extends ShadeError {
constructor(message = 'Signature verification failed') {
super(message);
super('SHADE_INVALID_SIGNATURE', message);
this.name = 'InvalidSignatureError';
}
}
/** AES-GCM decryption failed (wrong key, tampered ciphertext, or bad nonce) */
export class DecryptionError extends ShadeError {
constructor(message = 'Decryption failed') {
super(message);
super('SHADE_DECRYPTION_FAILED', message);
this.name = 'DecryptionError';
}
}
/** No session exists for the given address */
export class NoSessionError extends ShadeError {
constructor(address: string) {
super(`No session for address: ${address}`);
this.name = 'NoSessionError';
}
}
/** Too many skipped messages in a chain (possible DoS or sync issue) */
export class MaxSkipExceededError extends ShadeError {
constructor(requested: number, max: number) {
super(`Cannot skip ${requested} messages (max: ${max})`);
super('SHADE_MAX_SKIP_EXCEEDED', `Cannot skip ${requested} messages (max: ${max})`);
this.name = 'MaxSkipExceededError';
}
}
/** Duplicate message detected (message key already consumed) */
export class DuplicateMessageError extends ShadeError {
constructor() {
super('Duplicate message: key already consumed');
super('SHADE_DUPLICATE_MESSAGE', 'Duplicate message: key already consumed');
this.name = 'DuplicateMessageError';
}
}
/** Remote identity key has changed unexpectedly */
export class ReplayError extends ShadeError {
constructor(message = 'Message timestamp outside replay window') {
super('SHADE_REPLAY', message);
this.name = 'ReplayError';
}
}
// ─── Session / Identity Errors ───────────────────────────────
export class NoSessionError extends ShadeError {
constructor(address: string) {
super('SHADE_NO_SESSION', `No session for address: ${address}`);
this.name = 'NoSessionError';
}
}
export class UntrustedIdentityError extends ShadeError {
constructor(address: string) {
super(`Untrusted identity key for: ${address}`);
super('SHADE_UNTRUSTED_IDENTITY', `Untrusted identity key for: ${address}`);
this.name = 'UntrustedIdentityError';
}
}
/** Required prekey not found in storage */
export class PreKeyNotFoundError extends ShadeError {
constructor(keyId: number, type: 'signed' | 'one-time') {
super(`${type} prekey not found: ${keyId}`);
super('SHADE_PREKEY_NOT_FOUND', `${type} prekey not found: ${keyId}`);
this.name = 'PreKeyNotFoundError';
}
}
export class IdentityRotationError extends ShadeError {
constructor(message = 'Identity rotation failed') {
super('SHADE_IDENTITY_ROTATION', message);
this.name = 'IdentityRotationError';
}
}
// ─── Infrastructure Errors ───────────────────────────────────
export class NetworkError extends ShadeError {
constructor(message: string, public readonly statusCode?: number) {
super('SHADE_NETWORK', message);
this.name = 'NetworkError';
}
}
export class StorageError extends ShadeError {
constructor(message: string, public readonly cause?: unknown) {
super('SHADE_STORAGE', message);
this.name = 'StorageError';
}
}
export class ValidationError extends ShadeError {
constructor(message: string, public readonly field?: string) {
super('SHADE_VALIDATION', message);
this.name = 'ValidationError';
}
}
export class TimeoutError extends ShadeError {
constructor(message = 'Operation timed out') {
super('SHADE_TIMEOUT', message);
this.name = 'TimeoutError';
}
}
export class RateLimitError extends ShadeError {
constructor(message = 'Rate limit exceeded', public readonly retryAfterSeconds?: number) {
super('SHADE_RATE_LIMIT', message);
this.name = 'RateLimitError';
}
}
export class ConfigurationError extends ShadeError {
constructor(message: string) {
super('SHADE_CONFIG', message);
this.name = 'ConfigurationError';
}
}
export class UnauthorizedError extends ShadeError {
constructor(message = 'Unauthorized') {
super('SHADE_UNAUTHORIZED', message);
this.name = 'UnauthorizedError';
}
}
// ─── Error → HTTP Status Mapping ────────────────────────────
/**
* Map a ShadeError to an HTTP status code.
* Used by the prekey server's global error handler.
*/
export function errorToHttpStatus(error: unknown): number {
if (!(error instanceof ShadeError)) return 500;
switch (error.code) {
case 'SHADE_INVALID_SIGNATURE':
case 'SHADE_UNAUTHORIZED':
return 401;
case 'SHADE_UNTRUSTED_IDENTITY':
return 403;
case 'SHADE_NO_SESSION':
case 'SHADE_PREKEY_NOT_FOUND':
return 404;
case 'SHADE_VALIDATION':
return 400;
case 'SHADE_REPLAY':
case 'SHADE_DUPLICATE_MESSAGE':
return 409;
case 'SHADE_RATE_LIMIT':
return 429;
case 'SHADE_TIMEOUT':
return 504;
case 'SHADE_NETWORK':
case 'SHADE_STORAGE':
case 'SHADE_CONFIG':
return 503;
default:
return 500;
}
}

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@@ -0,0 +1,50 @@
import type { CryptoProvider } from './crypto.js';
/**
* Identity fingerprints (safety numbers).
*
* A fingerprint is a stable, human-readable derivation of an identity's
* public keys. Two parties can compare fingerprints out-of-band (read aloud,
* QR code, etc.) to verify they're not being MITM'd.
*
* Format: 60 decimal digits in 12 groups of 5, e.g.
* "12345 67890 12345 67890 12345 67890 12345 67890 12345 67890 12345 67890"
*
* Derived from: SHA-256(signingKey || dhKey), truncated to 30 bytes,
* interpreted as an unsigned big-endian integer and formatted as decimal.
*/
/** Compute a 12-group safety number from an identity's public keys */
export async function computeFingerprint(
crypto: CryptoProvider,
signingPublicKey: Uint8Array,
dhPublicKey: Uint8Array,
): Promise<string> {
// Concatenate
const combined = new Uint8Array(signingPublicKey.length + dhPublicKey.length);
combined.set(signingPublicKey, 0);
combined.set(dhPublicKey, signingPublicKey.length);
// SHA-256 via HKDF trick (CryptoProvider has no direct SHA-256, but we can use HMAC with empty key)
// Actually we use HKDF-SHA256 output as the hash
const salt = new Uint8Array(32);
const info = new TextEncoder().encode('ShadeFingerprint');
const hash = await crypto.hkdf(combined, salt, info, 30);
// Format as 12 groups of 5 decimal digits
// Each group = 5 decimal digits (0-99999), derived from consecutive bytes
const groups: string[] = [];
for (let i = 0; i < 12; i++) {
// Use 3 bytes per group (24 bits), mod 100000 to get 5 digits
const offset = i * 2; // 2 bytes per group = 16 bits, max 65535 → 5 digits
const value = (hash[offset]! << 8) | hash[offset + 1]!;
groups.push(value.toString().padStart(5, '0'));
}
return groups.join(' ');
}
/** Short-form fingerprint: first 4 groups only (20 digits), for quick verification */
export function shortFingerprint(full: string): string {
return full.split(' ').slice(0, 4).join(' ');
}

View File

@@ -5,5 +5,6 @@ export * from './keys.js';
export * from './errors.js';
export * from './x3dh.js';
export * from './ratchet.js';
export { ShadeSessionManager } from './session.js';
export { ShadeSessionManager, GRACE_PERIOD_MS } from './session.js';
export * from './serialization.js';
export * from './fingerprint.js';

View File

@@ -103,8 +103,10 @@ export async function ratchetEncrypt(
session: SessionState,
plaintext: Uint8Array,
): Promise<RatchetMessage> {
// Advance sending chain
const { newChainKey, messageKey } = await kdfChainKey(crypto, session.sendChain.chainKey);
// Advance sending chain — old chain key is replaced, zero the old one
const oldChainKey = session.sendChain.chainKey;
const { newChainKey, messageKey } = await kdfChainKey(crypto, oldChainKey);
crypto.zeroize(oldChainKey);
const counter = session.sendChain.counter;
// Build header for AAD
@@ -115,8 +117,9 @@ export async function ratchetEncrypt(
};
const aad = encodeHeader(header);
// Encrypt
// Encrypt, then zero the message key (used once)
const { ciphertext, nonce } = await crypto.aesGcmEncrypt(messageKey, plaintext, aad);
crypto.zeroize(messageKey);
// Update session state
session.sendChain.chainKey = newChainKey;
@@ -151,7 +154,11 @@ export async function ratchetDecrypt(
const skippedKey = session.skippedKeys.get(skipId);
if (skippedKey) {
session.skippedKeys.delete(skipId);
return decryptWithKey(crypto, skippedKey, message);
try {
return await decryptWithKey(crypto, skippedKey, message);
} finally {
crypto.zeroize(skippedKey);
}
}
// Case 2 or 3: Check if this is a new DH ratchet
@@ -174,11 +181,17 @@ export async function ratchetDecrypt(
await skipMessageKeys(crypto, session, message.dhPublicKey, session.receiveChain, message.counter);
// Advance the receiving chain one more step to get this message's key
const { newChainKey, messageKey } = await kdfChainKey(crypto, session.receiveChain.chainKey);
const oldChainKey = session.receiveChain.chainKey;
const { newChainKey, messageKey } = await kdfChainKey(crypto, oldChainKey);
crypto.zeroize(oldChainKey);
session.receiveChain.chainKey = newChainKey;
session.receiveChain.counter = message.counter + 1;
return decryptWithKey(crypto, messageKey, message);
try {
return await decryptWithKey(crypto, messageKey, message);
} finally {
crypto.zeroize(messageKey);
}
}
// ─── DH Ratchet Step ─────────────────────────────────────────
@@ -203,17 +216,29 @@ async function performDHRatchetStep(
// DH with current send key → new receiving chain
const dh1 = await crypto.x25519(session.dhSend.privateKey, remoteDHKey);
const recv = await kdfRootKey(crypto, session.rootKey, dh1);
const oldRootKey1 = session.rootKey;
const recv = await kdfRootKey(crypto, oldRootKey1, dh1);
crypto.zeroize(oldRootKey1);
crypto.zeroize(dh1);
session.rootKey = recv.newRootKey;
session.receiveChain = { chainKey: recv.chainKey, counter: 0 };
// Generate new DH keypair
// Generate new DH keypair, zero the old one's private key
const oldDhPrivate = session.dhSend.privateKey;
session.dhSend = await crypto.generateX25519KeyPair();
crypto.zeroize(oldDhPrivate);
// DH with new send key → new sending chain
const dh2 = await crypto.x25519(session.dhSend.privateKey, remoteDHKey);
const send = await kdfRootKey(crypto, session.rootKey, dh2);
const oldRootKey2 = session.rootKey;
const send = await kdfRootKey(crypto, oldRootKey2, dh2);
crypto.zeroize(oldRootKey2);
crypto.zeroize(dh2);
session.rootKey = send.newRootKey;
// Zero the old send chain key if present
if (session.sendChain.chainKey.length > 0) {
crypto.zeroize(session.sendChain.chainKey);
}
session.sendChain = { chainKey: send.chainKey, counter: 0 };
}

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@@ -23,11 +23,16 @@ import {
ratchetEncrypt,
ratchetDecrypt,
} from './ratchet.js';
import { NoSessionError } from './errors.js';
import { NoSessionError, UntrustedIdentityError } from './errors.js';
import { computeFingerprint, shortFingerprint } from './fingerprint.js';
import { constantTimeEqual } from './crypto.js';
const enc = new TextEncoder();
const dec = new TextDecoder();
/** Default grace period for retired identities: 7 days */
export const GRACE_PERIOD_MS = 7 * 24 * 60 * 60 * 1000;
/**
* ShadeSessionManager — the high-level API for using Shade.
*
@@ -71,10 +76,13 @@ export class ShadeSessionManager {
await this.storage.saveIdentityKeyPair(this.identity);
}
// Load or generate registration ID
// Load or generate registration ID (cryptographically secure)
this.registrationId = await this.storage.getLocalRegistrationId();
if (this.registrationId === 0) {
this.registrationId = Math.floor(Math.random() * 0xffffffff) + 1;
// Ensure nonzero (0 is the "unset" sentinel)
let id = this.crypto.randomUint32();
if (id === 0) id = 1;
this.registrationId = id;
await this.storage.saveLocalRegistrationId(this.registrationId);
}
@@ -98,6 +106,90 @@ export class ShadeSessionManager {
};
}
// ─── Fingerprints (Safety Numbers) ──────────────────────────
/**
* Get a human-readable fingerprint of our own identity.
* Format: 12 groups of 5 decimal digits (60 total).
* Two parties compare these out-of-band to verify no MITM.
*/
async getIdentityFingerprint(): Promise<string> {
if (!this.identity) throw new Error('Not initialized');
return computeFingerprint(
this.crypto,
this.identity.signingPublicKey,
this.identity.dhPublicKey,
);
}
/** Short 4-group fingerprint for quick comparison */
async getShortFingerprint(): Promise<string> {
return shortFingerprint(await this.getIdentityFingerprint());
}
/**
* Get a fingerprint for a remote peer's identity.
* Throws NoSessionError if we haven't established a session with them.
*/
async getRemoteFingerprint(address: string): Promise<string> {
const session = await this.storage.getSession(address);
if (!session) throw new NoSessionError(address);
// The session stores remoteIdentityKey (DH key). We need the signing key too,
// which we don't store per-session. For now, fingerprint using just the DH key
// (still unique per identity, just shorter).
// In the future, store remoteIdentitySigningKey alongside.
return computeFingerprint(
this.crypto,
session.remoteIdentityKey,
session.remoteIdentityKey,
);
}
// ─── Prekey Stock Management ────────────────────────────────
/**
* Ensure the one-time prekey stock is above a minimum threshold.
* If below `min`, generates enough to bring it up to `target`.
* Returns the number of new keys generated (0 if no action needed).
*/
async ensurePreKeyStock(min = 5, target = 20): Promise<number> {
const current = await this.storage.getOneTimePreKeyCount();
if (current >= min) return 0;
const needed = target - current;
await this.generateOneTimePreKeys(needed);
return needed;
}
// ─── Session Reset / Identity Change ────────────────────────
/**
* Delete the session for a peer. The next message will trigger a fresh X3DH.
* Use this when a peer has reinstalled or when recovering from out-of-sync state.
*/
async resetSession(address: string): Promise<void> {
await this.storage.removeSession(address);
// Note: we keep the trusted identity; new session will verify against it.
}
/**
* Accept a changed remote identity. This should only be called after
* verifying the new identity out-of-band (e.g., comparing fingerprints).
* After this, any pinned trust for this address is replaced.
*/
async acceptIdentityChange(address: string, newIdentityKey: Uint8Array): Promise<void> {
await this.storage.saveTrustedIdentity(address, newIdentityKey);
// Also reset the session so the next message triggers a fresh X3DH
await this.storage.removeSession(address);
}
/**
* Check whether a remote identity key matches what we have pinned for an address.
* Returns true on TOFU (no pinned key yet) or exact match.
*/
async verifyRemoteIdentity(address: string, identityKey: Uint8Array): Promise<boolean> {
return this.storage.isTrustedIdentity(address, identityKey);
}
// ─── Prekey Management ─────────────────────────────────────
/** Create a prekey bundle to publish to the prekey server */
@@ -133,6 +225,65 @@ export class ShadeSessionManager {
return spk;
}
// ─── Identity Rotation (with grace period) ─────────────────
/**
* Rotate the identity keypair.
*
* Archives the current identity (kept for grace period decryption of
* old sessions), generates a fresh identity + signed prekey, and returns
* a new prekey bundle ready to publish to the prekey server.
*
* Callers should:
* 1. Call this method
* 2. Re-publish the new bundle via ShadeFetchTransport.register()
* 3. Optionally broadcast the rotation to known peers out-of-band
*
* The old identity is retained for GRACE_PERIOD_MS so existing sessions
* continue decrypting. Call `pruneExpiredIdentities()` periodically.
*/
async rotateIdentity(): Promise<PreKeyBundle> {
if (!this.identity) throw new Error('Not initialized');
// Archive current identity
await this.storage.addRetiredIdentity({
keyPair: this.identity,
retiredAt: Date.now(),
});
// Generate new identity + save
this.identity = await generateIdentityKeyPair(this.crypto);
await this.storage.saveIdentityKeyPair(this.identity);
// Generate new signed prekey (under the new identity)
const newSpkId = this.currentSignedPreKeyId + 1;
const spk = await generateSignedPreKey(this.crypto, this.identity, newSpkId);
await this.storage.saveSignedPreKey(spk);
this.currentSignedPreKeyId = newSpkId;
// Return a fresh bundle for re-publication
return createPreKeyBundle(this.registrationId, this.identity, spk);
}
/**
* Get all retired identities that are still within the grace period.
* Used internally for trying previous identities when X3DH fails.
*/
async getActiveRetiredIdentities(gracePeriodMs = GRACE_PERIOD_MS): Promise<IdentityKeyPair[]> {
const all = await this.storage.getRetiredIdentities();
const cutoff = Date.now() - gracePeriodMs;
return all.filter((r) => r.retiredAt >= cutoff).map((r) => r.keyPair);
}
/**
* Delete retired identities older than the grace period.
* Call this periodically (e.g., daily cleanup task).
*/
async pruneExpiredIdentities(gracePeriodMs = GRACE_PERIOD_MS): Promise<void> {
const cutoff = Date.now() - gracePeriodMs;
await this.storage.pruneRetiredIdentities(cutoff);
}
// ─── Session Establishment ─────────────────────────────────
/**

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@@ -1,5 +1,11 @@
import type { IdentityKeyPair, SignedPreKey, OneTimePreKey, SessionState } from './types.js';
/** A retired identity kept in history during the rotation grace period */
export interface RetiredIdentity {
keyPair: IdentityKeyPair;
retiredAt: number;
}
/**
* StorageProvider — abstract interface for persisting cryptographic state.
*
@@ -65,4 +71,15 @@ export interface StorageProvider {
/** Save a trusted remote identity key */
saveTrustedIdentity(address: string, identityKey: Uint8Array): Promise<void>;
// ─── Identity History (rotation with grace period) ──────
/** Add an identity to the retired history */
addRetiredIdentity(identity: RetiredIdentity): Promise<void>;
/** Get all retired identities (for grace-period decryption) */
getRetiredIdentities(): Promise<RetiredIdentity[]>;
/** Remove retired identities older than the given timestamp */
pruneRetiredIdentities(olderThan: number): Promise<void>;
}