p2-insta485-serverside

EECS485 P2: Server-side Dynamic Pages

Due 11:59pm ET May 19, 2023. This is a group project to be completed in groups of two to three.

Change Log

Initial Release for SP23

Introduction

An Instagram clone implemented with server-side dynamic pages. This is the second of an EECS 485 three project sequence: a static site generator from templates, server-side dynamic pages, and client-side dynamic pages.

Build an interactive website using server-side dynamic pages. Reuse the templates from project 1, rendering them on-demand when a user loads a page. New features include creating, updating, and deleting users, posts, comments, and likes.

The learning goals of this project include server-side dynamic pages, CRUD (Create, Read, Update, Delete), sessions, and basic SQL database usage.

Here’s a preview of what your finished project will look like. A database-backed interactive website will work (mostly) like the real Instagram.

$ ./bin/insta485run
 * Serving Flask app "insta485"
 * Running on http://127.0.0.1:8000/ (Press CTRL+C to quit)

Then you will navigate to http://localhost:8000 and see working, multi-user, interactive website that you created. screenshot accounts login small

This project adds lots features. For example, users can add likes and comments.

screenshot accounts login small

Setup

Group registration

Please register your group on the Autograder. You must register your group to access the office hours queue. The synchronization between the autograder and office hours queue happens daily so you will need to wait a day before your group can access the OH queue. The office hours queue will give first priority to groups asking a question for the first time in a day.

AWS account and instance

You will use Amazon Web Services (AWS) to deploy your project. AWS account setup may take up to 24 hours, so get started now. Create an account, Start EC2 instance, and configure the instance. Don’t deploy yet. Only one group member needs to set up an AWS account. AWS Tutorial.

Project folder

Create a folder for this project. Your folder location might be different.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside

Pitfall: Avoid paths that contain spaces. Spaces cause problems with some command line tools.

Bad Example Good Example
EECS 485/Project 2 Insta485 Server-side eecs485/p2-insta485-serverside

WSL Pitfall: Avoid project directories starting with /mnt/c/. This shared directory is slow.

Bad Example Good Example
/mnt/c/ ... /home/awdeorio/ ...

Version control

Set up version control using the Version control tutorial.

Be sure to check out the Version control for a team tutorial.

Only one group member needs to create the remote repository.

After you’re done, you should have a local repository with a “clean” status and your local repository should be connected to a remote GitHub repository.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ git status
On branch main
Your branch is up-to-date with 'origin/main'.

nothing to commit, working tree clean
$ git remote -v
origin	https://github.com/awdeorio/p2-insta485-serverside.git (fetch)
origin	https://github.com/awdeorio/p2-insta485-serverside.git (push)

You should have a .gitignore file (instructions).

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ head .gitignore
This is a sample .gitignore file that's useful for EECS 485 projects.
...

Starter files

Download and unpack the starter files. Only one group member needs to download and unpack the starter files and the rest of the group can clone the repository.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ wget https://eecs485staff.github.io/p2-insta485-serverside/starter_files.tar.gz
$ tar -xvzf starter_files.tar.gz

Move the starter files to your project directory and remove the original starter_files/ directory.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ mv starter_files/* .
$ rm -rf starter_files starter_files.tar.gz

You should see these files.

$ tree -I 'env|__pycache__|*.egg-info'
.
├── requirements.txt
├── pyproject.toml
├── sql
│   └── uploads
        ...
│       └── e1a7c5c32973862ee15173b0259e3efdb6a391af.jpg
└── tests
    ....
    └── util.py
requirements.txt Python package dependencies matching autograder
pyproject.toml Insta485 Python package configuration
sql/uploads/ Sample image uploads
tests/ Public unit tests

Before making any changes to the clean starter files, it’s a good idea to make a commit to your Git repository.

Fresh install

These instructions are useful for a group member who wants to check out a fresh copy of the code.

Check out a fresh copy of the code in the directory that you store all of your EECS485 projects. Note that cloning the repository will create a new directory for your project.

$ git clone <your git URL here>
$ cd p2-insta485-serverside/

You can now continue with the next sections.

Python virtual environment

Each group member should create a Python virtual environment inside of the project directory using the Project 1 Python Virtual Environment Tutorial.

You should now have Python tools and third party packages installed locally. Your versions and exact libraries might be different.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ ls
env
$ source env/bin/activate
$ which python
/Users/awdeorio/src/eecs485/p2-insta485-serverside/env/bin/python
$ which pip
/Users/awdeorio/src/eecs485/p2-insta485-serverside/env/bin/pip
$ pip list
Package            Version
------------------ ---------
astroid            2.4.2
...
zipp               3.1.0

Install utilities

All group members need to install these utilities.

Linux and Windows Subsystem for Linux

$ sudo apt-get install sqlite3 curl

MacOS

$ brew install sqlite3 curl

Database

If you’re new to SQL, take a look at the w3Schools SQL Intro.

Start by completing the SQLite Tutorial. After the tutorial, you should have the sqlite3 command line utility installed. Your version might be different.

$ sqlite3 --version
3.29.0 2019-07-10 17:32:03 fc82b73eaac8b36950e527f12c4b5dc1e147e6f4ad2217ae43ad82882a88bfa6

You should have these files.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ tree sql
sql
├── data.sql
├── schema.sql
└── uploads
    ...
    └── e1a7c5c32973862ee15173b0259e3efdb6a391af.jpg

insta485db script

As part of the SQLite Tutorial Database management shell script section, you should have written insta485db.

Your script should work like this example. Your output might be slightly different, but it should create the same files.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ ./bin/insta485db reset
+ rm -rf var/insta485.sqlite3 var/uploads
+ mkdir -p var/uploads
+ sqlite3 var/insta485.sqlite3 < sql/schema.sql
+ sqlite3 var/insta485.sqlite3 < sql/data.sql
+ cp sql/uploads/* var/uploads/
$ tree var
var
├── insta485.sqlite3
└── uploads
    ...
    └── e1a7c5c32973862ee15173b0259e3efdb6a391af.jpg

Schema

Update schema.sql, which will create 5 tables: users, posts, following, comments and likes. The following list describes the tables and columns

Data

Update sql/data.sql to add all initial data. You can find a complete dump of the initial data in insta485db-dump.txt. Your timestamps will be different. The passwords are all set to password.

Testing

Install the libraries needed to run the database tests.

$ source env/bin/activate  # Make sure virtual environment is activated
$ pip install pytest

Run the public autograder testcases on your database schema and data.

$ pytest -v tests/db_tests
...
========================== 2 passed in 1.76 seconds ===========================

Make sure these tests pass before moving on. The other unit tests rely on a fully functionally bin/insta485db script.

You should now submit your work to the autograder. Ignore errors about files that don’t exist when making the tarball.

Flask app setup

Complete the Flask Tutorial if you have not already.

You should now have a directory containing an insta485 Python module.

$ tree insta485 -I '__pycache__'
insta485
├── __init__.py
├── config.py
├── model.py
├── static
│   └── css
│   │   └── style.css
├── templates
│   └── index.html
└── views
    ├── __init__.py
    └── index.py

insta485run script

The insta485run script starts a development server and you can browse to http://localhost:8000/ where you’ll see your “hello world” app. The Flask Tutorial Run Script section describes this script.

$ ./bin/insta485run

Testing

Compliant HTML

Automatically generated HTML shall be W3C HTML5 compliant. To test dynamically generated pages, the test_style.py::test_html test cases renders each page and saves it to a file. Then, it runs html5validator on the files. When you’re working on the starter tutorial, this test will fail and that’s OK.

$ pytest -vvs tests/app_tests/test_style.py::test_html
...
GET / FROM /
GET /explore/ FROM /
GET /users/awdeorio/ FROM /
GET /posts/3/ FROM /
GET /users/jflinn/ FROM /
GET /users/michjc/ FROM /
GET /posts/2/ FROM /
GET /posts/1/ FROM /
GET /users/jag/ FROM /explore/
GET /accounts/edit/ FROM /users/awdeorio/
GET /users/awdeorio/followers/ FROM /users/awdeorio/
GET /users/awdeorio/following/ FROM /users/awdeorio/
GET /users/jflinn/followers/ FROM /users/jflinn/
GET /users/jflinn/following/ FROM /users/jflinn/
GET /users/michjc/followers/ FROM /users/michjc/
GET /users/michjc/following/ FROM /users/michjc/
GET /users/jag/followers/ FROM /users/jag/
GET /users/jag/following/ FROM /users/jag/
GET /posts/4/ FROM /users/jag/
GET /accounts/password/ FROM /accounts/edit/
GET /accounts/delete/ FROM /accounts/edit/
html5validator --root tmp/localhost
PASSED

insta485test script

Similar to project 1, all Python code must be PEP8 compliant, comments shall be PEP257 compliant, and code shall pass a pylint static analysis.

Write another script called bin/insta485test that does this:

  1. Stop on errors and prints commands
  2. Run pycodestyle insta485
  3. Run pydocstyle insta485
  4. Run pylint insta485
  5. Run all unit tests using pytest -v tests

Don’t forget to check for shell script pitfalls.

$ file bin/*
bin/insta485db:        Bourne-Again shell script text executable, ASCII text
bin/insta485run:       Bourne-Again shell script text executable, ASCII text
bin/insta485test:      Bourne-Again shell script text executable, ASCII text

Unit tests

Now that you have the framework of the project in place and your utility scripts written, we can run some of the unit tests. We have provided the public Autograder tests.

Run the public autograder testcases on your utility scripts.

$ pytest -v tests/app_tests/test_scripts.py
...
========================== 5 passed in 1.16 seconds ===========================

Note: if you get deprecation warnings from third party libraries, check out the pytest tutorial - deprecation warnings to suppress them.

Server-side Insta485

This project includes the same pages as project 1. The pages also include buttons to follow, unfollow, like, unlike and comment. We’ll also add pages for user account administration.

List of URLs from project 1. Keep these URLs in project 2.

List of new URLs in project 2.

All pages

Include a link to the main page /.

If not logged in, redirect to /accounts/login/ (unless your current page is the login or create page).

If logged in, include a link to /explore/.

If logged in, include a link to /users/<user_url_slug>/ where user_url_slug is the logged in user.

Hint: When linking to pages or static files look into flask’s url_for() function.

Hint: In order to serve images correctly, look into flask’s send_from_directory() function.

Access control

The server should reject POST requests to delete entities not owned by the logged in user. For example, only the logged in user should be able to delete their own posts and comments. To reject a request with a permissions error, use flask.abort(403). Users should be able to comment and like posts of users that they are not following.

The following examples assume you have a (mostly) working Insta485 project with a freshly reset database.

Using curl

Curl is a command line tool for making HTTP requests. You can make the same requests that browser would make from the CLI.

Use curl to log in to Insta485. This command issues a POST request to /accounts/ with a username and password. The -F KEY=VALUE sends a key-value pair just like a web form. The --cookie-jar cookies.txt will save the cookies set by the website to the file cookies.txt.

$ curl -X POST http://localhost:8000/accounts/ \
  -F username=awdeorio \
  -F password=password \
  -F operation=login \
  --cookie-jar cookies.txt

Always use HTTPS for user login pages. Never use HTTP, which transfers a password in plaintext where a network eavesdropper could read it. For simplicity, this project uses HTTP only.

View the index / page by issuing a GET request, sending the cookies set by the previous login (--cookie cookies.txt).

$ curl --cookie cookies.txt http://localhost:8000/
... <index.html page content here>

Delete a post by issuing a POST request.

$ curl -X POST http://localhost:8000/posts/ \
  -F postid=1 \
  -F operation=delete \
  --cookie cookies.txt

Malicious example

Even though the “Delete post” button is hidden on posts that the logged in user doesn’t own, any user can use a tool like curl to send a POST request to try to delete an Insta485 post.

Try to delete a post created by jflinn using awdeorio’s cookies. We get a 403 Forbidden error. This is a good thing!

$ curl -X POST http://localhost:8000/posts/ \
  -F postid=2 \
  -F operation=delete \
  --cookie cookies.txt
...
<title>403 Forbidden</title>
...

A 403 Forbidden error should also be returned when a malicious user attempts to delete another person’s comment.

Index GET /

screenshot

The index page should include all posts from the logged in user and all other users that the logged in user is following. The most recent post should be at the top. For each post:

Pro-tip: Returning the most recent posts can be tricky because database initialization creates many posts at nearly the same instant. Thus, ordering by timestamp can result in ties. Instead, use the fact that post ID is incremented automatically if set up properly in your schema.

Form for “like” button

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_LIKES_URL_HERE>?target=<FIXME_CURRENT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="hidden" name="operation" value="like"/>
  <input type="hidden" name="postid" value="<FIXME_POST_ID_HERE>"/>
  <input type="submit" name="like" value="like"/>
</form>

Form for “unlike” button

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_LIKES_URL_HERE>?target=<FIXME_CURRENT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="hidden" name="operation" value="unlike"/>
  <input type="hidden" name="postid" value="<FIXME_POST_ID_HERE>"/>
  <input type="submit" name="unlike" value="unlike"/>
</form>

Form for “comment” button

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_COMMENTS_URL_HERE>?target=<FIXME_CURRENT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="hidden" name="operation" value="create"/>
  <input type="hidden" name="postid" value="<FIXME_POST_ID_HERE>"/>
  <input type="text" name="text" required/>
  <input type="submit" name="comment" value="comment"/>
</form>

GET /users/<user_url_slug>/

screenshot1 screenshot2

Be sure to include

For a user’s own page, also include

If someone tries to access a user_url_slug that does not exist in the database, then abort(404).

Form for follow button

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_FOLLOWING_URL_HERE>?target=<FIXME_CURRENT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="submit" name="follow" value="follow"/>
  <input type="hidden" name="username" value="<FIXME_USERNAME_HERE>"/>
  <input type="hidden" name="operation" value="follow"/>
</form>

Form for unfollow button

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_FOLLOWING_URL_HERE>?target=<FIXME_CURRENT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="submit" name="unfollow" value="unfollow"/>
  <input type="hidden" name="username" value="<FIXME_USERNAME_HERE>"/>
  <input type="hidden" name="operation" value="unfollow"/>
</form>

Form for logout

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_LOGOUT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="submit" name="logout" value="Logout"/>
</form>

Form for file upload

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_POSTS_URL_HERE>?target=<FIXME_CURRENT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="file" name="file" accept="image/*" required/>
  <input type="submit" name="create_post" value="upload new post"/>
  <input type="hidden" name="operation" value="create"/>
</form>

GET /users/<user_url_slug>/followers/

screenshot

List the users that are following user_url_slug. For each, include:

If someone tries to access a user_url_slug that does not exist in the database, then abort(404).

GET /users/<user_url_slug>/following/

screenshot

List the users that user_url_slug is following. For each, include:

If someone tries to access a user_url_slug that does not exist in the database, then abort(404).

GET /posts/<postid_url_slug>/

screenshot1 screenshot2

This page shows one post. Include the same information for this one post as is shown on the main page /.

Include a “delete” button next to each comment owned by the logged in user.

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_COMMENTS_URL_HERE>?target=<FIXME_CURRENT_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="hidden" name="operation" value="delete"/>
  <input type="hidden" name="commentid" value="<FIXME_COMMENT_ID_HERE>"/>
  <input type="submit" name="uncomment" value="delete"/>
</form>

Include a “delete this post” button if the post is owned by the logged in user.`

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_POSTS_URL_HERE>?target=<FIXME_LOGGED_IN_USER_PAGE_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="hidden" name="operation" value="delete"/>
  <input type="hidden" name="postid" value="<FIXME_POST_ID_HERE>"/>
  <input type="submit" name="delete" value="delete this post"/>
</form>

GET /explore/

screenshot

This page lists all users not that the logged in user is not following and includes:

GET /accounts/login/

screenshot

If logged in, redirect to /.

Otherwise, include username and password inputs and a login button.

Also include a link to /accounts/create/ in the page.

Use this HTML form code. Feel free to style it and include placeholders.

<!-- DO NOT CHANGE THIS (aside from styling) -->
<form action="<FIXME_ACCOUNTS_URL_HERE>?target=<FIXME_INDEX_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="text" name="username" required/>
  <input type="password" name="password" required/>
  <input type="submit" value="login"/>
  <input type="hidden" name="operation" value="login"/>
</form>

POST /accounts/logout/

This endpoint only accepts POST requests.

Log out user. Immediately redirect to /accounts/login/.

GET /accounts/create/

screenshot

If a user is already logged in, redirect to /accounts/edit/.

Also include a link to /accounts/login/ in the page.

HTML form. Style as you like.

<!-- DO NOT CHANGE THIS (aside from styling) -->
<form action="<FIXME_ACCOUNTS_URL_HERE>?target=<FIXME_INDEX_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="file" name="file" required/>
  <input type="text" name="fullname" required/>
  <input type="text" name="username" required/>
  <input type="text" name="email" required/>
  <input type="password" name="password" required/>
  <input type="submit" name="signup" value="sign up"/>
  <input type="hidden" name="operation" value="create"/>
</form>

We’ve shipped one of the autograder tests so you can verify that login and logout mechanics work correctly. It’s in starter_files/tests/test_login_logout.py. Save it to tests/test_login_logout.py and run it like this:

$ pytest -v tests/app_tests/test_login_logout.py
== test session starts ==
...
== 4 passed in 0.91 seconds ==

GET /accounts/delete/

screenshot

Confirmation page includes username and this form:

<!-- DO NOT CHANGE THIS -->
<form action="<FIXME_ACCOUNTS_URL_HERE>?target=<FIXME_ACCOUNTS_CREATE_HERE>" method="post" enctype="multipart/form-data">
  <input type="submit" name="delete" value="confirm delete account"/>
  <input type="hidden" name="operation" value="delete"/>
</form>

GET /accounts/edit/

screenshot

Include user’s current photo and username. Include a form with photo upload, name and email. Name and email are automatically filled in with previous value. Username can not be edited.

Link to /accounts/password/.

Link to /accounts/delete/.

Use this form:

<!-- DO NOT CHANGE THIS (aside from where we say 'FIXME') -->
<form action="<FIXME_ACCOUNTS_URL_HERE>?target=<FIXME_CURRENT_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="file" name="file" accept="image/*"/>
  <input type="text" name="fullname" value="<FIXME_FULL_NAME_HERE>" required/>
  <input type="text" name="email" value="<FIXME_EMAIL_HERE>" required/>
  <input type="submit" name="update" value="submit"/>
  <input type="hidden" name="operation" value="edit_account"/>
</form>

GET /accounts/password/

screenshot

Include this form:

<!-- DO NOT CHANGE THIS -->
<form action="<FIXME_ACCOUNTS_URL_HERE>?target=<FIXME_EDIT_ACCOUNT_URL_HERE>" method="post" enctype="multipart/form-data">
  <input type="password" name="password" required/>
  <input type="password" name="new_password1" required/>
  <input type="password" name="new_password2" required/>
  <input type="submit" name="update_password" value="submit"/>
  <input type="hidden" name="operation" value="update_password"/>
</form>

Link to /accounts/edit/.

GET /accounts/auth/

Return a 200 status code with no content (i.e. an empty response) if the user is logged in. abort(403) if the user is not logged in. This route is only used when you deploy the app to AWS.

POST /likes/?target=URL

This endpoint only accepts POST requests. Create or delete a like and immediately redirect to URL.

Use the operation and postid values from the POST request form content.

If operation is like, create a like for postid. If operation is unlike, delete a like for postid.

Then, redirect to URL. If the value of ?target is not set, redirect to /.

If someone tries to like a post they have already liked or unlike a post they have not liked, then abort(409)

Hint: Any additional arguments passed to the url_for() function are appended to the URL as query parameters.

>>> flask.url_for("my_function", my_key="my_value")
/my_endpoint?my_key=my_value

You can also use url_for() in a jinja2 template HTML file.

POST /comments/?target=URL

This endpoint only accepts POST requests. Create or delete a comment on a post and immediately redirect to URL.

Use the operation, postid, commentid and text values from the POST request form content.

If operation is create, then create a new comment on postid with the content text. If operation is delete, then delete comment with ID commentid.

If a user tries to create an empty comment, then abort(400). 400 is the HTTP code indicating a Bad Request.

If a user tries to delete a comment that they do not own, then abort(403).

If the value of ?target is not set, redirect to /.

POST /posts/?target=URL

This endpoint only accepts POST requests. Create or delete a post and immediately redirect to URL.

Use the operation and postid values from the POST response form content.

If operation is create, save the image file to disk and redirect to URL.

If a user tries to create a post with an empty file, then abort(400).

If operation is delete, delete the image file for postid from the filesystem. Delete everything in the database related to this post. Redirect to URL.

If the value of ?target is not set, redirect to /users/<logname>/.

If a user tries to delete a post that they do not own, then abort(403).

UUID filenames

Use a universally unique identifier (UUID) for the filename when creating a post. A few reasons for UUID filenames are

  1. Avoid two uploads with the same name overwriting each other,
  2. Avoid filenames with characters that the filesystem doesn’t support.

Here’s how to compute filenames in your Flask app:

import pathlib
import uuid
import insta485

# Unpack flask object
fileobj = flask.request.files["file"]
filename = fileobj.filename

# Compute base name (filename without directory).  We use a UUID to avoid
# clashes with existing files, and ensure that the name is compatible with the
# filesystem. For best practive, we ensure uniform file extensions (e.g.
# lowercase).
stem = uuid.uuid4().hex
suffix = pathlib.Path(filename).suffix.lower()
uuid_basename = f"{stem}{suffix}"

# Save to disk
path = insta485.app.config["UPLOAD_FOLDER"]/uuid_basename
fileobj.save(path)

For example, if you upload the file awdeorio.JPG, the computed filename for this file would look something like fa0869c36f504c3fafd21d428185b387.jpg. Since UUID’s are generated randomly, your UUID will be different. Notice the lowercase file extension.

POST /following/?target=URL

This endpoint only accepts POST requests. Follows or unfollows a user and immediately redirect to URL.

Use the operation and username values from the POST request form content.

If operation is follow, then make user logname follow user username.

If operation is unfollow, then make user logname unfollow user username.

If a user tries to follow a user that they already follow or unfollow a user that they do not follow, then abort(409).

If the value of ?target is not set, redirect to /.

POST /accounts/?target=URL

This endpoint only accepts POST requests. Perform various account operations and immediately redirect to URL.

Use the operation value from the POST request form content to determine the type of action to take.

If the value of ?target is not set, redirect to /.

Operation: login

Use username and password from the POST request form content to log the user in.

If the username or password fields are empty, abort(400).

If username and password authentication fails, abort(403).

Set a session cookie. Reminder: only store minimal information in a session cookie!

Redirect to URL.

Operation: create

Use username, password, fullname, email and file from the POST request form content to create the user. See above for file upload and naming procedure.

If any of the above fields are empty, abort(400).

If a user tries to create an account with an existing username in the database, abort(409). 409 is the HTTP code indicating a Conflict Error.

Log the user in and redirect to URL.

Password storage

A password entry in the database contains the algorithm, salt and password hash separated by $. Use the sha512 algorithm like this:

import uuid
import hashlib
algorithm = 'sha512'
salt = uuid.uuid4().hex
hash_obj = hashlib.new(algorithm)
password_salted = salt + password
hash_obj.update(password_salted.encode('utf-8'))
password_hash = hash_obj.hexdigest()
password_db_string = "$".join([algorithm, salt, password_hash])
print(password_db_string)

Operation: delete

If the user is not logged in, abort(403).

Delete all post files created by this user. Delete user icon file. Delete all related entries in all tables. Hint: database tables set up properly with primary/foreign key relationships and ON DELETE CASCADE will do this automatically.

Upon successful submission, clear the user’s session, and redirect to URL.

Operation: edit_account

If the user is not logged in, abort(403).

Use fullname, email and file from the POST request form content to edit the user account.

If the fullname or email fields are empty, abort(400).

If no photo file is included, update only the user’s name and email.

If a photo file is included, then the server will update the user’s photo, name and email. Delete the old photo from the filesystem. See above for file upload and naming procedure.

Upon successful submission, redirect to URL.

Operation: update_password

If the user is not logged in, abort(403).

Use password, new_password1 and new_password2 from the POST request form content to update the user’s password.

If any of the above fields are empty, abort(400).

Verify password against the user’s password hash in the database. If verification fails, abort(403).

Verify both new passwords match. If verification fails, abort(401).

Update hashed password entry in database. See above for the password storage procedure.

Redirect to URL.

Static File Permissions

A user with the direct link to an uploaded file, /uploads/<filename>, should only be able to see that file if logged in.

If an unauthenticated user attempts to access an uploaded file, abort(403), regardless of whether the file exists.

If an authenticated user attempts to access a file that does not exist, abort(404).

Testing

Run the unit tests. Everything except for the deploy test should pass.

$ pytest -v

You should now submit your work to the autograder. Ignore errors about files that don’t exist when making the tarball.

Deploy to AWS

You should have already created an AWS account and instance (instructions). Resume the AWS Tutorial with Install Nginx and Install Flask App.

After you have deployed your site, download the main page along with a log. Do this from your local development machine, not while SSH’d into your EC2 instance.

$ pwd
/Users/awdeorio/src/eecs485/p2-insta485-serverside
$ hostname
awdeorio-laptop  # NOT AWS
$ curl -v <Public DNS (IPv4)>/accounts/login/ > deployed_insta485.html 2> deployed_insta485.log

Be sure to verify that the output in deployed_insta485.log doesn’t include errors like “Couldn’t connect to server”. If it does contain an error like this, it means curl couldn’t successfully connect with your flask app. Also be sure to check that the curl command points to your AWS instance URL and not to localhost.

Be sure to verify that the output in deployed_insta485.html looks like a successfully rendered login page and does not contain any errors.

Shutting down AWS instance

Be sure to shut down your instance when you’re done with it (Stop EC2 Instance Instructions).

Submitting and grading

One team member should register your group on the autograder using the create new invitation feature.

Submit a tarball to the autograder, which is linked from https://eecs485.org. Include the --disable-copyfile flag only on macOS.

$ tar \
  --disable-copyfile \
  --exclude '*__pycache__*' \
  -czvf submit.tar.gz \
  bin \
  insta485 \
  sql \
  deployed_insta485.html \
  deployed_insta485.log

The autograder will run pip install -e YOUR_SOLUTION. The exact library versions in the requirements.txt provided with the starter files is cached on the autograder, so be sure not to add extra library dependencies to requirements.txt or pyproject.toml.

Direct link to the Project 2 autograder: https://autograder.io/web/project/2055.

Rubric

This is an approximate rubric.

Deliverable Value
Handcoded SQL 10%
Python and HTML style 10%
Scripts 10%
insta485 (public) 30%
insta485 (private) 35%
AWS deployment 5%

Things we won’t test

The autograder focuses on the functionality of your solution. These are some specific optional aspects of the project that we won’t evaluate.

FAQ

Do trailing slashes in URLs matter?

Yes. Use them everywhere. See the “Unique URLs / Redirection Behavior” section in the Flask quickstart. Here’s a good example:

@insta485.app.route("/users/<username_url_slug>/", methods=["GET", "POST"])

Static files (like .jpg) should not have a trailing slash at the end. Use trailing slashes everywhere else.

Should I change HTML forms?

You can add HTML to style forms any way you choose. Don’t change the number, type or names of the inputs. This is because the autograder will make POST requests.

Use the flask.url_for function. Read documentation about this function online.

Can I disable any code style checks?

Do not disable any code style check from any code style tool (pycodestyle, pydocstyle, pylint). There are three exceptions listed here.

There are several pylint --disable options mentioned in the Testing Section, above. Use the exact commands provided.

In insta485/__init__.py, the Flask framework requires an import at the bottom of the file (reference). We’re going to tell pylint and pycodestyle to ignore this coding style violation.

import insta485.views  # noqa: E402  pylint: disable=wrong-import-position
import insta485.model  # noqa: E402  pylint: disable=wrong-import-position

In insta485/__init__.py, the Flask framework uses an object that is used throughout the module. Although its value never changes, it is not a constant in the classic sense. We’re going to tell pylint to ignore this coding style violation.

app = flask.Flask(__name__)  # pylint: disable=invalid-name

Why do I keep getting 404 Not Found?

A common reason to get 404 Not Found errors is if you forget to include the routes in your solution’s insta485/views/__init__.py file. Here’s a snippet of the instructor solution.

from insta485.views.index import show_index
from insta485.views.user import show_user
# ...

Acknowledgments

Original document written by Andrew DeOrio awdeorio@umich.edu.

This document is licensed under a Creative Commons Attribution-NonCommercial 4.0 License. You’re free to copy and share this document, but not to sell it. You may not share source code provided with this document.