feat: Password-protect assessment instance creation

middlewares/studentAssessmentAccess.js

@@ -51,27 +51,13 @@ router.all('/', function (req, res, next) {
     }
   }
 
-  // Password protect the assessment
-  if (
-    'authz_result' in res.locals &&
-    'password' in res.locals.authz_result &&
-    res.locals.authz_result.password &&
-    res.locals?.assessment_instance?.open
-  ) {
-    // No password yet case
-    if (req.cookies.pl_assessmentpw == null) {
-      return badPassword(res, req);
-    }
-
-    // Invalid or expired password case
-    var pwData = csrf.getCheckedData(req.cookies.pl_assessmentpw, config.secretKey, {
-      maxAge: timeout * 60 * 60 * 1000,
-    });
-    if (pwData == null || pwData.password !== res.locals.authz_result.password) {
-      return badPassword(res, req);
-    }
-
-    // Successful password case: falls though
+  // Password protect the assessment. Note that this only handles the general
+  // case of an existing assessment instance. This middleware can't handle
+  // the intricacies of creating a new assessment instance. We handle those
+  // cases on the `studentAssessmentExam` and `studentAssessmentHomework`
+  // pages.
+  if (res.locals?.assessment_instance?.open && !module.exports.checkPasswordOrRedirect(req, res)) {
+    return;
   }
 
   // Pass-through for everything else
@@ -80,6 +66,40 @@ router.all('/', function (req, res, next) {
 
 module.exports = router;
 
+/**
+ * Checks if the given request has the correct password. If not, redirects to
+ * a password input page.
+ *
+ * Returns `true` if the password is correct, `false` otherwise. If this
+ * function returns `false`, the caller should not continue with the request.
+ *
+ * @returns {boolean}
+ */
+module.exports.checkPasswordOrRedirect = function (req, res) {
+  if (!res.locals.authz_result?.password) {
+    // No password is required.
+    return true;
+  }
+
+  if (req.cookies.pl_assessmentpw == null) {
+    // The user has not entered a password yet.
+    badPassword(res, req);
+    return false;
+  }
+
+  var pwData = csrf.getCheckedData(req.cookies.pl_assessmentpw, config.secretKey, {
+    maxAge: timeout * 60 * 60 * 1000,
+  });
+  if (pwData == null || pwData.password !== res.locals.authz_result.password) {
+    // The password is incorrect or the cookie is expired.
+    badPassword(res, req);
+    return false;
+  }
+
+  // The password is correct and not expired!
+  return true;
+};
+
 function badPassword(res, req) {
   logger.verbose(`invalid password attempt for ${res.locals.user.uid}`);
   res.cookie('pl_pw_origUrl', req.originalUrl);

pages/studentAssessmentExam/studentAssessmentExam.js

@@ -2,6 +2,7 @@ var ERR = require('async-stacktrace');
 var express = require('express');
 var router = express.Router();
 
+const { checkPasswordOrRedirect } = require('../../middlewares/studentAssessmentAccess');
 var error = require('../../prairielib/lib/error');
 var assessment = require('../../lib/assessment');
 var sqldb = require('../../prairielib/lib/sql-db');
@@ -12,6 +13,14 @@ var sql = sqlLoader.loadSqlEquiv(__filename);
 router.get('/', function (req, res, next) {
   if (res.locals.assessment.type !== 'Exam') return next();
   if (res.locals.assessment.multiple_instance) {
+    // The user has landed on this page to create a new assessment instance.
+    //
+    // Before allowing the user to create a new assessment instance, we need
+    // to check if the current access rules require a password. If they do,
+    // we'll ensure that the password has already been entered before allowing
+    // students to create and start a new assessment instance.
+    if (!checkPasswordOrRedirect(req, res)) return;
+
     res.render(__filename.replace(/\.js$/, '.ejs'), res.locals);
   } else {
     var params = {
@@ -21,6 +30,12 @@ router.get('/', function (req, res, next) {
     sqldb.query(sql.select_single_assessment_instance, params, function (err, result) {
       if (ERR(err, next)) return;
       if (result.rowCount === 0) {
+        // Before allowing the user to create a new assessment instance, we need
+        // to check if the current access rules require a password. If they do,
+        // we'll ensure that the password has already been entered before allowing
+        // students to create and start a new assessment instance.
+        if (!checkPasswordOrRedirect(req, res)) return;
+
         res.render(__filename.replace(/\.js$/, '.ejs'), res.locals);
       } else {
         res.redirect(res.locals.urlPrefix + '/assessment_instance/' + result.rows[0].id);
@@ -42,6 +57,12 @@ router.post('/', function (req, res, next) {
   // permission required to create an assessment for the effective user.
 
   if (req.body.__action === 'new_instance') {
+    // Before allowing the user to create a new assessment instance, we need
+    // to check if the current access rules require a password. If they do,
+    // we'll ensure that the password has already been entered before allowing
+    // students to create and start a new assessment instance.
+    if (!checkPasswordOrRedirect(req, res)) return;
+
     assessment.makeAssessmentInstance(
       res.locals.assessment.id,
       res.locals.user.user_id,

pages/studentAssessmentHomework/studentAssessmentHomework.js

@@ -4,6 +4,7 @@ var router = express.Router();
 var path = require('path');
 var debug = require('debug')('prairielearn:' + path.basename(__filename, '.js'));
 
+const { checkPasswordOrRedirect } = require('../../middlewares/studentAssessmentAccess');
 var error = require('../../prairielib/lib/error');
 var assessment = require('../../lib/assessment');
 var sqldb = require('../../prairielib/lib/sql-db');
@@ -43,7 +44,8 @@ router.get('/', function (req, res, next) {
       // student data in the course instance (which has already been checked), exactly the
       // permission required to create an assessment for the effective user.
 
-      //if it is a group_work with no instance, jump to a confirm page.
+      // If this assessment is group work and there is no existing instance,
+      // show the group info page.
       if (res.locals.assessment.group_work) {
         sqldb.query(sql.get_config_info, params, function (err, result) {
           if (ERR(err, next)) return;
@@ -67,6 +69,12 @@ router.get('/', function (req, res, next) {
           });
         });
       } else {
+        // Before allowing the user to create a new assessment instance, we need
+        // to check if the current access rules require a password. If they do,
+        // we'll ensure that the password has already been entered before allowing
+        // students to create and start a new assessment instance.
+        if (!checkPasswordOrRedirect(req, res)) return;
+
         const time_limit_min = null;
         assessment.makeAssessmentInstance(
           res.locals.assessment.id,
@@ -100,6 +108,12 @@ router.post('/', function (req, res, next) {
     sqldb.query(sql.find_single_assessment_instance, params, function (err, result) {
       if (ERR(err, next)) return;
       if (result.rowCount === 0) {
+        // Before allowing the user to create a new assessment instance, we need
+        // to check if the current access rules require a password. If they do,
+        // we'll ensure that the password has already been entered before allowing
+        // students to create and start a new assessment instance.
+        if (!checkPasswordOrRedirect(req, res)) return;
+
         const time_limit_min = null;
         assessment.makeAssessmentInstance(
           res.locals.assessment.id,