fix: secure authentication request identity
Replace Better Auth's default trust of a caller-controlled X-Forwarded-For with a platform-owned client-address resolution boundary: direct mode (the safe default) trusts only the real socket peer, and an explicit trusted-proxy mode requires a header name, a concrete trusted-proxy list, and only honors a forwarded chain from an actual trusted peer. This closes a rate-limit bypass where rotating a spoofed header let a caller choose a fresh bucket on every request. Public sign-up is also disabled by default and requires an explicit typed opt-in, using Better Auth's own disableSignUp gate so no email-existence leak or second signup path is introduced. Co-Authored-By: Claude Sonnet 5 <[email protected]>
This commit is contained in:
ekklesia
co-authored by
Claude Sonnet 5
Claude Sonnet 5
parent
5e09330001
commit
cafd513019
@@ -0,0 +1,280 @@
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import net from "node:net";
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export type ClientAddressMode = "direct" | "trusted-proxy";
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export type ClientAddressConfigErrorCode =
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| "CLIENT_ADDRESS_DIRECT_MODE_CONTRADICTION"
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| "CLIENT_ADDRESS_HEADER_INVALID"
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| "CLIENT_ADDRESS_HEADER_MISSING"
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| "CLIENT_ADDRESS_MODE_INVALID"
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| "CLIENT_ADDRESS_TRUSTED_PROXIES_EMPTY"
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| "CLIENT_ADDRESS_TRUSTED_PROXY_INVALID";
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const clientAddressConfigErrorMessages: Readonly<Record<ClientAddressConfigErrorCode, string>> =
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Object.freeze({
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CLIENT_ADDRESS_DIRECT_MODE_CONTRADICTION:
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"Direct client-address mode must not also configure a header or trusted proxies.",
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CLIENT_ADDRESS_HEADER_INVALID: "The client-address header must be a valid HTTP header name.",
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CLIENT_ADDRESS_HEADER_MISSING:
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"Trusted-proxy client-address mode requires an explicit header name.",
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CLIENT_ADDRESS_MODE_INVALID: 'The client-address mode must be "direct" or "trusted-proxy".',
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CLIENT_ADDRESS_TRUSTED_PROXIES_EMPTY:
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"Trusted-proxy client-address mode requires at least one trusted proxy address or range.",
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CLIENT_ADDRESS_TRUSTED_PROXY_INVALID:
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"Every trusted proxy entry must be a valid IPv4/IPv6 address or CIDR range.",
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});
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/** Never carries the offending mode, header name, or trusted-proxy value. */
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export class ClientAddressConfigError extends Error {
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readonly code: ClientAddressConfigErrorCode;
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constructor(code: ClientAddressConfigErrorCode) {
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super(clientAddressConfigErrorMessages[code]);
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this.name = "ClientAddressConfigError";
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this.code = code;
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this.stack = `${this.name}: ${this.message}`;
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Object.freeze(this);
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}
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}
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export interface DirectClientAddressConfig {
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readonly mode: "direct";
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}
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/**
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* `header` is the one header name the reverse proxy is trusted to set — the platform transport
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* boundary (`apps/api/src/client-address.ts`) overwrites any externally supplied copy of it before
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* this policy ever sees the request, so it never needs to be `X-Forwarded-For` specifically, though
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* that remains the common choice. `trustedProxies` lists the proxy's own address(es)/range(s), never
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* a broad private range that also covers real clients.
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*/
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export interface TrustedProxyClientAddressConfig {
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readonly mode: "trusted-proxy";
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readonly header: string;
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readonly trustedProxies: readonly string[];
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}
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export type ClientAddressConfig = DirectClientAddressConfig | TrustedProxyClientAddressConfig;
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export interface ClientAddressConfigInput {
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readonly mode?: unknown;
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readonly header?: unknown;
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readonly trustedProxies?: unknown;
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}
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const HEADER_TOKEN_PATTERN = /^[a-z0-9-]+$/u;
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const CIDR_PREFIX_PATTERN = /^\d+$/u;
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const IPV4_MAPPED_PATTERN = /^::ffff:(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})$/iu;
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/**
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* Normalizes a single address token for consistent identity/comparison: plain IPv4 is returned
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* as-is, an IPv4-mapped IPv6 address (`::ffff:a.b.c.d` — the form Node's own `socket.remoteAddress`
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* and real reverse proxies actually emit for an IPv4 peer on a dual-stack listener) collapses to its
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* embedded IPv4 form, and any other valid IPv6 address is lowercased. A zone id (`%eth0`) is
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* rejected as ambiguous outside its own interface. Anything that is not a syntactically valid IPv4
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* or IPv6 address returns `undefined` rather than being guessed at.
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*/
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export function normalizeClientAddress(address: string): string | undefined {
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const trimmed = address.trim();
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if (trimmed.length === 0) {
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return undefined;
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}
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if (net.isIPv4(trimmed)) {
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return trimmed;
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}
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if (trimmed.includes("%")) {
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return undefined;
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}
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if (net.isIPv6(trimmed)) {
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const mapped = IPV4_MAPPED_PATTERN.exec(trimmed);
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if (mapped) {
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const embedded = mapped[1] as string;
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return net.isIPv4(embedded) ? embedded : undefined;
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}
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return trimmed.toLowerCase();
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}
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return undefined;
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}
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interface ParsedTrustedProxyEntry {
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readonly network: string;
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readonly prefix: number;
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readonly family: "ipv4" | "ipv6";
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}
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function parseTrustedProxyEntry(entry: string): ParsedTrustedProxyEntry | undefined {
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const slashIndex = entry.indexOf("/");
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const addressPart = slashIndex === -1 ? entry : entry.slice(0, slashIndex);
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const network = normalizeClientAddress(addressPart);
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if (!network) {
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return undefined;
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}
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const family: "ipv4" | "ipv6" = net.isIPv4(network) ? "ipv4" : "ipv6";
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const maxPrefix = family === "ipv4" ? 32 : 128;
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if (slashIndex === -1) {
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return { family, network, prefix: maxPrefix };
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}
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const prefixPart = entry.slice(slashIndex + 1);
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if (!CIDR_PREFIX_PATTERN.test(prefixPart)) {
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return undefined;
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}
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const prefix = Number(prefixPart);
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return prefix <= maxPrefix ? { family, network, prefix } : undefined;
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}
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/** Trusted-proxy entries that are not a valid IPv4/IPv6 address or CIDR range — used both by config
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* validation and, if ever needed diagnostically, by Doctor. */
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export function findInvalidTrustedProxies(entries: readonly string[]): readonly string[] {
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return entries.filter((entry) => parseTrustedProxyEntry(entry) === undefined);
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}
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/**
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* Validates explicit, typed client-address configuration. The safe default (`mode: "direct"`) is
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* used whenever `mode` is entirely omitted; every other field is validated strictly, and an
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* incomplete or contradictory combination (proxy details without proxy mode, proxy mode without
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* proxy details) is rejected outright rather than guessed at. `internalHeaderName` is the one
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* platform-owned header (`TRUSTED_CLIENT_ADDRESS_HEADER`, `./runtime.js`) a caller must never be
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* able to configure as its own "trusted" source header.
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*/
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export function createClientAddressConfig(
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input: ClientAddressConfigInput = {},
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internalHeaderName?: string,
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): ClientAddressConfig {
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const mode = input.mode ?? "direct";
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if (mode !== "direct" && mode !== "trusted-proxy") {
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throw new ClientAddressConfigError("CLIENT_ADDRESS_MODE_INVALID");
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}
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if (mode === "direct") {
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if (input.header !== undefined || input.trustedProxies !== undefined) {
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throw new ClientAddressConfigError("CLIENT_ADDRESS_DIRECT_MODE_CONTRADICTION");
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}
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return Object.freeze({ mode: "direct" });
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}
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if (typeof input.header !== "string" || input.header.trim().length === 0) {
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throw new ClientAddressConfigError("CLIENT_ADDRESS_HEADER_MISSING");
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}
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const header = input.header.trim().toLowerCase();
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if (!HEADER_TOKEN_PATTERN.test(header)) {
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throw new ClientAddressConfigError("CLIENT_ADDRESS_HEADER_INVALID");
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}
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if (internalHeaderName !== undefined && header === internalHeaderName) {
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// The internal sanitized header is never a valid *source* header — trusting it as the
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// caller-forwarded value would let a caller set its own "resolved" address directly.
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throw new ClientAddressConfigError("CLIENT_ADDRESS_HEADER_INVALID");
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}
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if (!Array.isArray(input.trustedProxies) || input.trustedProxies.length === 0) {
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throw new ClientAddressConfigError("CLIENT_ADDRESS_TRUSTED_PROXIES_EMPTY");
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}
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const trustedProxies = input.trustedProxies.map((entry) => {
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if (typeof entry !== "string" || entry.trim().length === 0) {
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throw new ClientAddressConfigError("CLIENT_ADDRESS_TRUSTED_PROXY_INVALID");
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}
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return entry.trim();
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});
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if (findInvalidTrustedProxies(trustedProxies).length > 0) {
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throw new ClientAddressConfigError("CLIENT_ADDRESS_TRUSTED_PROXY_INVALID");
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}
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return Object.freeze({
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header,
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mode: "trusted-proxy",
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trustedProxies: Object.freeze(trustedProxies),
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});
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}
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export type ClientAddressFailureReason =
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| "FORWARDED_CHAIN_EXHAUSTED"
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| "FORWARDED_HEADER_MALFORMED"
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| "FORWARDED_HEADER_MISSING"
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| "PEER_ADDRESS_UNAVAILABLE";
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export type ClientAddressResolution =
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| { readonly ok: true; readonly address: string }
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| { readonly ok: false; readonly reason: ClientAddressFailureReason };
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export interface ClientAddressResolver {
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resolve(input: {
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readonly peerAddress: string | undefined;
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readonly headers: Headers;
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}): ClientAddressResolution;
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}
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function buildTrustedProxyMatcher(trustedProxies: readonly string[]): (address: string) => boolean {
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const blockList = new net.BlockList();
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for (const entry of trustedProxies) {
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const parsed = parseTrustedProxyEntry(entry);
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if (!parsed) {
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// Config validation already rejects this at startup; a matcher is only ever built from an
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// already-validated config, so this can only mean the config was constructed unsafely.
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throw new ClientAddressConfigError("CLIENT_ADDRESS_TRUSTED_PROXY_INVALID");
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}
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blockList.addSubnet(parsed.network, parsed.prefix, parsed.family);
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}
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return (address: string): boolean =>
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blockList.check(address, net.isIPv4(address) ? "ipv4" : "ipv6");
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}
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/**
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* Builds the one server-owned client-address resolution policy this API runtime uses for every
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* request, from already-validated configuration. Built once at startup (never per-request) so the
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* trusted-proxy `BlockList` is compiled a single time. Depends only on `node:net` and the standard
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* Fetch `Headers` type — never Hono or `@hono/node-server` — so it stays reusable by Core's own
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* identity composition without pulling an HTTP framework into Core; the Node/Hono transport glue
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* that reads the actual socket peer and rewrites the request lives in `apps/api` instead
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* (`apps/api/src/client-address.ts`).
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*
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* Direct mode trusts only the actual immediate socket peer — never any request header. Trusted-proxy
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* mode trusts the configured forwarded header's content only when the actual immediate socket peer
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* matches a configured trusted-proxy address/range; otherwise it falls back to direct-mode behavior
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* (the peer address itself), exactly as if no forwarded header existed at all. A forwarded chain is
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* walked right to left: trailing hops that match a trusted proxy are skipped, and the first hop from
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* the right that does not match is the resolved client address. A chain that is missing, empty,
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* contains any malformed token, or consists entirely of trusted-proxy hops (no genuine client
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* address left to resolve) fails closed rather than guessing — never a caller-chosen bucket, and
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* never a silent collapse onto the proxy's own address.
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*/
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export function createClientAddressResolver(config: ClientAddressConfig): ClientAddressResolver {
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const isTrustedProxy =
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config.mode === "trusted-proxy" ? buildTrustedProxyMatcher(config.trustedProxies) : undefined;
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return {
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resolve({ peerAddress, headers }): ClientAddressResolution {
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const normalizedPeer =
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peerAddress === undefined ? undefined : normalizeClientAddress(peerAddress);
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if (!normalizedPeer) {
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return { ok: false, reason: "PEER_ADDRESS_UNAVAILABLE" };
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}
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if (config.mode === "direct" || !isTrustedProxy?.(normalizedPeer)) {
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return { ok: true, address: normalizedPeer };
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}
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const headerValue = headers.get(config.header);
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if (headerValue === null) {
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return { ok: false, reason: "FORWARDED_HEADER_MISSING" };
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}
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const tokens = headerValue.split(",").map((token) => token.trim());
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if (tokens.length === 0 || tokens.some((token) => token.length === 0)) {
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return { ok: false, reason: "FORWARDED_HEADER_MALFORMED" };
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}
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const normalizedTokens: string[] = [];
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for (const token of tokens) {
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const normalized = normalizeClientAddress(token);
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if (!normalized) {
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return { ok: false, reason: "FORWARDED_HEADER_MALFORMED" };
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}
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normalizedTokens.push(normalized);
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}
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for (let index = normalizedTokens.length - 1; index >= 0; index -= 1) {
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const candidate = normalizedTokens[index];
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if (candidate !== undefined && !isTrustedProxy(candidate)) {
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return { ok: true, address: candidate };
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}
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}
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return { ok: false, reason: "FORWARDED_CHAIN_EXHAUSTED" };
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},
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};
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}
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