matrix-js-sdk/src/oidc/validate.ts

Matrix Client-Server SDK for Javascript

/*
Copyright 2023 The Matrix.org Foundation C.I.C.

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.
*/

import { jwtDecode } from "jwt-decode";
import { type IdTokenClaims, type OidcMetadata, type SigninResponse } from "oidc-client-ts";

import { logger } from "../logger.ts";
import { OidcError } from "./error.ts";
import { OAuthGrantType } from "./index.ts";

/**
 * Metadata from OAuth 2.0 client authentication API as per
 * https://spec.matrix.org/v1.17/client-server-api/#get_matrixclientv1auth_metadata
 * With validated properties required in type
 */
export type ValidatedAuthMetadata = Partial<OidcMetadata> &
    Pick<
        // These values are from [RFC8414](https://datatracker.ietf.org/doc/html/rfc8414#section-2)
        // so we can reuse the OidcMetadata definitions from oidc-client-ts
        OidcMetadata,
        | "issuer"
        | "authorization_endpoint"
        | "token_endpoint"
        | "revocation_endpoint"
        | "response_types_supported"
        | "grant_types_supported"
        | "code_challenge_methods_supported"
    > & {
        // These values aren't part of RFC8414 so we add them here
        // Account management fields from stable MSC4191:
        account_management_uri?: string;
        account_management_actions_supported?: string[];
        // Value from [Initiating User Registration via OpenID Connect](https://openid.net/specs/openid-connect-prompt-create-1_0.html):
        prompt_values_supported?: string[];
        // Experimental MSC4341 value from [RFC8628](https://datatracker.ietf.org/doc/html/rfc8628#section-4):
        device_authorization_endpoint?: string;
    };

const isRecord = (value: unknown): value is Record<string, unknown> =>
    !!value && typeof value === "object" && !Array.isArray(value);
const requiredStringProperty = (wellKnown: Record<string, unknown>, key: string): boolean => {
    if (!wellKnown[key] || !optionalStringProperty(wellKnown, key)) {
        logger.error(`Missing or invalid property: ${key}`);
        return false;
    }
    return true;
};
const optionalStringProperty = (wellKnown: Record<string, unknown>, key: string): boolean => {
    if (!!wellKnown[key] && typeof wellKnown[key] !== "string") {
        logger.error(`Invalid property: ${key}`);
        return false;
    }
    return true;
};
const optionalStringArrayProperty = (wellKnown: Record<string, unknown>, key: string): boolean => {
    if (
        !!wellKnown[key] &&
        (!Array.isArray(wellKnown[key]) || !(<unknown[]>wellKnown[key]).every((v) => typeof v === "string"))
    ) {
        logger.error(`Invalid property: ${key}`);
        return false;
    }
    return true;
};
const requiredArrayValue = (wellKnown: Record<string, unknown>, key: string, value: any): boolean => {
    const array = wellKnown[key];
    if (!array || !Array.isArray(array) || !array.includes(value)) {
        logger.error(`Invalid property: ${key}. ${value} is required.`);
        return false;
    }
    return true;
};

/**
 * Validates OAuth 2.0 auth metadata as defined by
 * https://spec.matrix.org/v1.17/client-server-api/#get_matrixclientv1auth_metadata
 * is compatible with Element's OAuth/OIDC flow
 * @param authMetadata - json object
 * @returns valid issuer config
 * @throws Error - when issuer config is not found or is invalid
 */
export const validateAuthMetadata = (authMetadata: unknown): ValidatedAuthMetadata => {
    if (!isRecord(authMetadata)) {
        logger.error("Issuer configuration not found or malformed");
        throw new Error(OidcError.OpSupport);
    }

    const isInvalid = [
        requiredStringProperty(authMetadata, "issuer"),
        requiredStringProperty(authMetadata, "authorization_endpoint"),
        requiredStringProperty(authMetadata, "token_endpoint"),
        requiredStringProperty(authMetadata, "revocation_endpoint"),
        optionalStringProperty(authMetadata, "registration_endpoint"),
        optionalStringProperty(authMetadata, "account_management_uri"),
        optionalStringProperty(authMetadata, "device_authorization_endpoint"),
        optionalStringArrayProperty(authMetadata, "account_management_actions_supported"),
        requiredArrayValue(authMetadata, "response_types_supported", "code"),
        requiredArrayValue(authMetadata, "grant_types_supported", OAuthGrantType.AuthorizationCode),
        requiredArrayValue(authMetadata, "code_challenge_methods_supported", "S256"),
        optionalStringArrayProperty(authMetadata, "prompt_values_supported"),
    ].some((isValid) => !isValid);

    if (!isInvalid) {
        return authMetadata as ValidatedAuthMetadata;
    }

    logger.error("Issuer configuration not valid");
    throw new Error(OidcError.OpSupport);
};

export const decodeIdToken = (token: string): IdTokenClaims => {
    try {
        return jwtDecode<IdTokenClaims>(token);
    } catch (error) {
        logger.error("Could not decode id_token", error);
        throw error;
    }
};

/**
 * Validate idToken
 * https://openid.net/specs/openid-connect-core-1_0.html#IDTokenValidation
 * @param idToken - id token from token endpoint
 * @param issuer - issuer for the OP as found during discovery
 * @param clientId - this client's id as registered with the OP
 * @param nonce - nonce used in the authentication request
 * @throws when id token is invalid
 */
export const validateIdToken = (
    idToken: string | undefined,
    issuer: string,
    clientId: string,
    nonce: string | undefined,
): void => {
    try {
        if (!idToken) {
            throw new Error("No ID token");
        }
        const claims = decodeIdToken(idToken);

        // The Issuer Identifier for the OpenID Provider MUST exactly match the value of the iss (issuer) Claim.
        if (claims.iss !== issuer) {
            throw new Error("Invalid issuer");
        }
        /**
         * The Client MUST validate that the aud (audience) Claim contains its client_id value registered at the Issuer identified by the iss (issuer) Claim as an audience.
         * The aud (audience) Claim MAY contain an array with more than one element.
         * The ID Token MUST be rejected if the ID Token does not list the Client as a valid audience, or if it contains additional audiences not trusted by the Client.
         * EW: Don't accept tokens with other untrusted audiences
         * */
        const sanitisedAuds = typeof claims.aud === "string" ? [claims.aud] : claims.aud;
        if (!sanitisedAuds.includes(clientId)) {
            throw new Error("Invalid audience");
        }

        /**
         * If a nonce value was sent in the Authentication Request, a nonce Claim MUST be present and its value checked
         * to verify that it is the same value as the one that was sent in the Authentication Request.
         */
        if (nonce !== undefined && claims.nonce !== nonce) {
            throw new Error("Invalid nonce");
        }

        /**
         * The current time MUST be before the time represented by the exp Claim.
         *  exp is an epoch timestamp in seconds
         * */
        if (!claims.exp || Date.now() > claims.exp * 1000) {
            throw new Error("Invalid expiry");
        }
    } catch (error) {
        logger.error("Invalid ID token", error);
        throw new Error(OidcError.InvalidIdToken);
    }
};

/**
 * State we ask OidcClient to store when starting oidc authorization flow (in `generateOidcAuthorizationUrl`)
 * so that we can access it on return from the OP and complete login
 */
export type UserState = {
    /**
     * Remember which server we were trying to login to
     */
    homeserverUrl: string;
    identityServerUrl?: string;
    /**
     * Used to validate id token
     */
    nonce: string;
};
/**
 * Validate stored user state exists and is valid
 * @param userState - userState returned by oidcClient.processSigninResponse
 * @throws when userState is invalid
 */
export function validateStoredUserState(userState: unknown): asserts userState is UserState {
    if (!isRecord(userState)) {
        logger.error("Stored user state not found");
        throw new Error(OidcError.MissingOrInvalidStoredState);
    }
    const isInvalid = [
        requiredStringProperty(userState, "homeserverUrl"),
        requiredStringProperty(userState, "nonce"),
        optionalStringProperty(userState, "identityServerUrl"),
    ].some((isValid) => !isValid);

    if (isInvalid) {
        throw new Error(OidcError.MissingOrInvalidStoredState);
    }
}

/**
 * The expected response type from the token endpoint during authorization code flow
 * Normalized to always use capitalized 'Bearer' for token_type
 *
 * See https://datatracker.ietf.org/doc/html/rfc6749#section-4.1.4,
 * https://openid.net/specs/openid-connect-basic-1_0.html#TokenOK.
 */
export type BearerTokenResponse = {
    token_type: "Bearer";
    access_token: string;
    scope: string;
    refresh_token?: string;
    expires_in?: number;
    // from oidc-client-ts
    expires_at?: number;
    id_token: string;
};

/**
 * Make required properties required in type
 */
type ValidSignInResponse = SigninResponse &
    BearerTokenResponse & {
        token_type: "Bearer" | "bearer";
    };

const isValidBearerTokenResponse = (response: unknown): response is ValidSignInResponse =>
    isRecord(response) &&
    requiredStringProperty(response, "token_type") &&
    // token_type is case insensitive, some OPs return `token_type: "bearer"`
    (response["token_type"] as string).toLowerCase() === "bearer" &&
    requiredStringProperty(response, "access_token") &&
    requiredStringProperty(response, "refresh_token") &&
    (!("expires_in" in response) || typeof response["expires_in"] === "number");

export function validateBearerTokenResponse(response: unknown): asserts response is ValidSignInResponse {
    if (!isValidBearerTokenResponse(response)) {
        throw new Error(OidcError.InvalidBearerTokenResponse);
    }
}