Implement script strategy (#117)

bin/example-script

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+# Example script for script strategy. Allows any username as long as the password is "$USERNAME-123".
+
+if [[ $PASSWORD != "$USERNAME-123" ]]; then
+  echo "{\"message\":\"Wrong password\"}"
+else
+  echo "{\"id\":\"$USERNAME\"}"
+fi

lib/script-strategy.js

@@ -0,0 +1,84 @@
+/**
+ * Script strategy that calls a local script to verify provided credentials.
+ *
+ * See: https://github.com/gbv/login-server/issues/117
+ *
+ * Requires a local path to the script.
+ */
+
+/**
+ * Module dependencies.
+ */
+import passport from "passport-strategy"
+import util from "node:util"
+
+import { exec as cpexec } from "node:child_process"
+/**
+ * A wrapper around child_process' exec function for async/await.
+ *
+ * @param {*} command
+ * @param {*} options
+ */
+async function exec(command, options) {
+  return new Promise((resolve, reject) => {
+    cpexec(command, options || {}, (error, stdout, stderr) => {
+      if (error) {
+        error.stdout = stdout
+        error.stderr = stderr
+        return reject(error)
+      }
+      resolve(stdout)
+    })
+  })
+}
+
+/**
+ * `Strategy` constructor.
+ *
+ * @param {Object} options
+ * @param {Function} callback
+ * @api public
+ */
+export function Strategy({ script, passReqToCallback }, callback) {
+  if (!script) {
+    throw new TypeError("Script strategy requires a script to run")
+  }
+  passport.Strategy.call(this)
+  this.name = "script"
+  this._passReqToCallback = passReqToCallback
+  this._script = script
+  this._cb = callback
+}
+
+/**
+ * Inherit from `passport.Strategy`.
+ */
+util.inherits(Strategy, passport.Strategy)
+
+/**
+ * Authenticate using supplied user.
+ *
+ * @param {Object} req
+ * @api protected
+ */
+Strategy.prototype.authenticate = async function(req) {
+  let username = (req.body && req.body.username) || req.query.username
+  let password = (req.body && req.body.password) || req.query.password
+  if (!username || !password) {
+    return this.fail({ message: "Missing credentials" }, 400)
+  }
+  try {
+    const result = JSON.parse(await exec(this._script, { env: { ...process.env, USERNAME: username, PASSWORD: password }}))
+    if (!result?.id) {
+      throw new Error(result.message || "Wrong credentials")
+    }
+    const user = result
+    let args = this._passReqToCallback ? [req] : []
+    args = args.concat([null, null, user, (error, user) => {
+      this.success(user)
+    }])
+    this._cb(...args)
+  } catch (error) {
+    return this.fail({ message: error.message }, 400)
+  }
+}

strategies/script.js

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+/**
+ * Script Stategy.
+ */
+
+import { Strategy } from "../lib/script-strategy.js"
+
+export default (options, provider, callback) => new Strategy(options, (req, token, tokenSecret, profile, done) => {
+  callback(req, token, tokenSecret, {
+    id: profile.id || profile.username,
+    name: profile.name,
+    username: profile.username,
+    uri: profile.uri,
+    provider: provider.id,
+  }, done)
+})