Example of CASL integration in expressjs app

Read CASL in Expressjs app for details.

CASL is an isomorphic authorization JavaScript library which restricts what resources a given user is allowed to access.

This is an example application which shows how integrate CASL in blog application. There are 3 entities:

• User
• Post
• Comment

Application uses passport-jwt for authentication. Permission logic (i.e., abilities) are define in src/auth/abilities.js. Rules can be specified for authenticated and anonymous users, so potentially it's quite easy to give access anonymous users to leave comments in blog. The main logic is built on top of modules (src/modules)

Note: refactored to use CASL 2.0. See @casl/ability and @casl/mongoose for details. Warning: this code is just an example and doesn't follow best practices everywhere (e.g. it stores passwords without hashing).

Note #2: in order to use with Vuex example switch to branch vue-api

Installation

The shell used here is Bash under Linux. However, the npm scripts should work under any other OS.

Mongodb must be at least installed on the workstation, if not running:

• the script start will use a ``blogdatabase on an already running instance of Mongo with URLmongodb://localhost:27017/blog`
• the script dev will start a dedicated instance, eg:

git clone https://github.com/atao-web/casl-express-example.git && cd casl-express-example

npm install
npm run mongo:bson2json # fill embedded database if empty in development mode
npm run dev

Instruction to login

Used tools: curl, json-parse-cli , jq. This tools are just convenient to this presentation and in no way required to run the application.

1. Create new user

NEW_USER=$(curl -X POST "http://localhost:3002/users" -H "Content-Type: application/json" -d '{"user":{"email":"[email protected]","password":"dummy"}}' -w '\n' -sS)

echo $NEW_USER | json-parse -f json -i 4
# {
#     "user": {
#         "_id": "5de0b86f76ce2519553449ef",
#         "email": "[email protected]",
#         "password": "dummy",
#         "createdAt": "2019-11-29T06:19:27.205Z",
#         "updatedAt": "2019-11-29T06:19:27.205Z",
#         "__v": 0
#     }
# }

ID_USER=$(echo $NEW_USER | jq -r '.user._id')

echo $ID_USER
# 5de0b86f76ce2519553449ef

2. Create new session

SESSION=$(curl -H "Content-Type: application/json" -d '{"session":{"email":"[email protected]","password":"dummy"}}' -X POST "http://localhost:3002/session" -w '\n' -sSv)
# *   Trying ::1...
# * TCP_NODELAY set
# * Connected to localhost (::1) port 3002 (#0)
# > POST /session HTTP/1.1
# > Host: localhost:3002
# > User-Agent: curl/7.58.0
# > Accept: */*
# > Content-Type: application/json
# > Content-Length: 60
# > 
# } [60 bytes data]
# * upload completely sent off: 60 out of 60 bytes
# < HTTP/1.1 200 OK
# < Content-Type: application/json; charset=utf-8
# < Content-Length: 215
# < ETag: W/"d7-fol5aTHrxD40x6Yndb/BHRazDEU"
# < Date: Fri, 29 Nov 2019 06:20:42 GMT
# < Connection: keep-alive
# < 
# { [215 bytes data]
# * Connection #0 to host localhost left intact

echo $SESSION | json-parse -f json -i 4
# {
#     "accessToken": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjVkZTBiODZmNzZjZTI1MTk1NTM0NDllZiIsImlhdCI6MTU3NTAwODQ0MiwiYXVkIjoiY2FzbC5pbyIsImlzcyI6IkNBU0wuRXhwcmVzcyJ9.Y_y_lGgOm9UP3c1T6-CLVEVC4YpCZjOjdkox9L9WUuU"
# }

ACCESS_TOKEN=$(echo $SESSION | jq -r '.accessToken')

echo $ACCESS_TOKEN
# eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjVkZTBiODZmNzZjZTI1MTk1NTM0NDllZiIsImlhdCI6MTU3NTAwODQ0MiwiYXVkIjoiY2FzbC5pbyIsImlzcyI6IkNBU0wuRXhwcmVzcyJ9.Y_y_lGgOm9UP3c1T6-CLVEVC4YpCZjOjdkox9L9WUuU

3. Put access token in Authorization header for all future requests

Available entry points:

• /posts
• /posts/:id/comments
• /users
• /session

To create or update an entity you need to send parameters in wrapper object, which key equals entity name. For example, to get current user data:

curl -X GET "http://localhost:3002/users/$ID_USER" -H "Authorization: $ACCESS_TOKEN" -H "Content-Type: application/json" -w '\n' -sS | json-parse -f json -i 4
# {
#     "user": {
#         "_id": "5de0b86f76ce2519553449ef",
#         "email": "[email protected]",
#         "password": "dummy",
#         "createdAt": "2019-11-29T06:19:27.205Z",
#         "updatedAt": "2019-11-29T06:19:27.205Z",
#         "__v": 0
#     }
# }

To create a comment on a existing post:

curl -X POST "http://localhost:3002/posts/59761ba80203fb638e9bd85c/comments" -H "Content-Type: application/json" -H "Authorization: $ACCESS_TOKEN" -d '{"comment":{"text":"Ouahh ... Too good!"}}' -w '\n' -sS | json-parse -f json -i 4
# {
#     "comment": {
#         "_id": "5de0b92676ce2519553449f0",
#         "text": "Ouahh ... Too good!",
#         "post": "59761ba80203fb638e9bd85c",
#         "author": "5de0b86f76ce2519553449ef",
#         "createdAt": "2019-11-29T06:22:30.427Z",
#         "updatedAt": "2019-11-29T06:22:30.427Z",
#         "__v": 0
#     }
# }

curl -X GET "http://localhost:3002/posts/59761ba80203fb638e9bd85c/comments" -H "Content-Type: application/json" -w '\n' -sS | json-parse -f json -i 4
# {
#     "comments": [
#         {
#             "_id": "59763c7f6882927829c9265e",
#             "updatedAt": "2017-07-24T18:29:19.646Z",
#             "createdAt": "2017-07-24T18:29:19.646Z",
#             "text": "[Updated] opa?",
#             "post": "59761ba80203fb638e9bd85c",
#             "author": "5975b833a9c0631a35509bbf",
#             "__v": 0
#         },
#         {
#             "_id": "5de0b92676ce2519553449f0",
#             "text": "Ouahh ... Too good!",
#             "post": "59761ba80203fb638e9bd85c",
#             "author": "5de0b86f76ce2519553449ef",
#             "createdAt": "2019-11-29T06:22:30.427Z",
#             "updatedAt": "2019-11-29T06:22:30.427Z",
#             "__v": 0
#         }
#     ]
# }

References