koa-jwt2

Koa middleware that validates JsonWebTokens and sets ctx.state.user.

This module lets you authenticate HTTP requests using JWT tokens in your Node.js applications. JWTs are typically used to protect API endpoints, and are often issued using OpenID Connect.

Install

$ npm install koa-jwt2 --save

Usage

The JWT authentication middleware authenticates callers using a JWT. If the token is valid, ctx.state.user will be set with the JSON object decoded to be used by later middleware for authorization and access control.

For example,

var jwt = require("koa-jwt2");

app.get("/protected", jwt({ secret: "shhhhhhared-secret" }), async function(
  ctx
) {
  if (!ctx.state.user.admin) return (ctx.status = 401);
  ctx.status = 200;
});

You can specify audience and/or issuer as well:

jwt({
  secret: "shhhhhhared-secret",
  audience: "http://myapi/protected",
  issuer: "http://issuer"
});

If the JWT has an expiration (exp), it will be checked.

If you are using a base64 URL-encoded secret, pass a Buffer with base64 encoding as the secret instead of a string:

jwt({ secret: new Buffer("shhhhhhared-secret", "base64") });

Optionally you can make some paths unprotected as follows:

app.use(jwt({ secret: "shhhhhhared-secret" }).unless({ path: ["/token"] }));

This is especially useful when applying to multiple routes. In the example above, path can be a string, a regexp, or an array of any of those.

For more details on the .unless syntax including additional options, please see koa-unless.

This module also support tokens signed with public/private key pairs. Instead of a secret, you can specify a Buffer with the public key

var publicKey = fs.readFileSync("/path/to/public.pub");
jwt({ secret: publicKey });

By default, the decoded token is attached to ctx.state.user but can be configured with the property option.

jwt({ secret: publicKey, property: "auth" });

A custom function for extracting the token from a request can be specified with the getToken option. This is useful if you need to pass the token through a query parameter or a cookie. You can throw an error in this function and it will be handled by koa-jwt2.

app.use(
  jwt({
    secret: "hello world !",
    credentialsRequired: false,
    getToken: function fromHeaderOrQuerystring(ctx) {
      if (
        ctx.headers.authorization &&
        ctx.headers.authorization.split(" ")[0] === "Bearer"
      ) {
        return ctx.headers.authorization.split(" ")[1];
      } else if (ctx.query && ctx.query.token) {
        return ctx.query.token;
      }
      return null;
    }
  })
);

Multi-tenancy

If you are developing an application in which the secret used to sign tokens is not static, you can provide a async function as the secret parameter. The function has the signature: async function(ctx, payload):

• ctx (Object) - The koa ctx object.
• payload (Object) - An object with the JWT claims.

need to return a secret string or promise to use to verify the JWT.

For example, if the secret varies based on the JWT issuer:

const jwt = require("koa-jwt2");
const data = require("./data");
const utilities = require("./utilities");

const secretAsync = async function(ctx, payload) {
  const issuer = payload.iss;

  return new Promise((resolve, reject) => {
    data.getTenantByIdentifier(issuer, function(err, tenant) {
      if (err) {
        return reject(err);
      }
      if (!tenant) {
        reject(new Error("missing_secret"));
      }

      const secret = utilities.decrypt(tenant.secret);
      resolve(secret);
    });
  });
};

app.get("/protected", jwt({ secret: secretCallback }), async function(ctx) {
  if (!ctx.state.user.admin) {
    ctx.throw(401);
  }
  ctx.status = 200;
  ctx.body = "";
});

Revoked tokens

It is possible that some tokens will need to be revoked so they cannot be used any longer. You can provide a function as the isRevoked option. The signature of the function is async function(ctx, payload):

• ctx (Object) - The koa context object.
• payload (Object) - An object with the JWT claims.

For example, if the (iss, jti) claim pair is used to identify a JWT:

const jwt = require("koa-jwt2");
const data = require("./data");
const utilities = require("./utilities");

const isRevokedAsync = function(req, payload, done) {
  const issuer = payload.iss;
  const tokenId = payload.jti;

  return new Promise((resolve, reject) => {
    data.getRevokedToken(issuer, tokenId, function(err, token) {
      if (err) {
        return reject(err);
      }
      resolve(!!token);
    });
  });
};

app.get(
  "/protected",
  jwt({
    secret: "shhhhhhared-secret",
    isRevoked: isRevokedAsync
  }),
  async function(ctx) {
    if (!ctx.state.user.admin) {
      ctx.throw(401);
    }
    ctx.status = 200;
    ctx.body = "";
  }
);

Error handling

The default behavior is to throw an error when the token is invalid, so you can add your custom logic to manage unauthorized access as follows:

app.use(async function(ctx, next) {
  try {
    await next();
  } catch (err) {
    if (err.name === "UnauthorizedError") {
      ctx.status = 401;
      ctx.body = "invalid token...";
    }
  }
});

You might want to use this module to identify registered users while still providing access to unregistered users. You can do this by using the option credentialsRequired:

app.use(
  jwt({
    secret: "hello world !",
    credentialsRequired: false
  })
);

Related Modules

• jsonwebtoken — JSON Web Token sign and verification

Tests

$ npm install
$ npm test

Contributors

Check them out here

License

This project is licensed under the MIT license. See the LICENSE file for more info.