mirror of
https://github.com/hedgedoc/hedgedoc.git
synced 2024-12-01 15:02:06 -05:00
60 lines
2.6 KiB
Markdown
60 lines
2.6 KiB
Markdown
# API Authentication
|
|
|
|
!!! info "Design Document"
|
|
This is a design document, explaining the design and vision for a HedgeDoc 2
|
|
feature. It is not a user guide and may or may not be fully implemented.
|
|
|
|
## Public API
|
|
|
|
All requests to the public API require authentication using a [bearer token](https://datatracker.ietf.org/doc/html/rfc6750).
|
|
|
|
This token can be generated using the profile page in the frontend
|
|
(which in turn uses the private API to generate the token).
|
|
|
|
### Token generation
|
|
|
|
When a new token is requested via the private API, the backend generates a 64 bytes-long secret of
|
|
cryptographically secure data and returns it as a base64url-encoded string, along with an identifier.
|
|
That string can then be used by clients as a bearer token.
|
|
|
|
A SHA-512 hash of the secret is stored in the database. To validate tokens, the backend computes the hash of the provided
|
|
secret and checks it against the stored hash for the provided identifier.
|
|
|
|
#### Choosing a hash function
|
|
|
|
Unfortunately, there does not seem to be any explicit documentation about our exact use-case.
|
|
Most docs describe classic password-saving scenarios and recommend bcrypt, scrypt or argon2.
|
|
These hashing functions are slow to stop brute-force or dictionary attacks, which would expose the original,
|
|
user-provided password, that may have been reused across multiple services.
|
|
|
|
We have a very different scenario:
|
|
Our API tokens are 64 bytes of cryptographically strong pseudorandom data.
|
|
Brute-force or dictionary attacks are therefore virtually impossible, and tokens are not reused across multiple services.
|
|
We therefore need to only guard against one scenario:
|
|
An attacker gains read-only access to the database. Saving only hashes in the database prevents the attacker
|
|
from authenticating themselves as a user. The hash-function does not need to be very slow,
|
|
as the randomness of the original token prevents inverting the hash. The function actually needs to be reasonably fast,
|
|
as the hash must be computed on every request to the public API.
|
|
SHA-512 (or alternatively SHA3) fits this use-case.
|
|
|
|
## Private API
|
|
|
|
The private API uses a session cookie to authenticate the user.
|
|
Sessions are handled using [passport.js](https://www.passportjs.org/).
|
|
|
|
The backend hands out a new session token after the user has successfully authenticated
|
|
using one of the supported authentication methods:
|
|
|
|
- Username & Password (`local`)
|
|
- LDAP
|
|
- SAML
|
|
- OAuth2
|
|
- GitLab
|
|
- GitHub
|
|
- Facebook
|
|
- Twitter
|
|
- Dropbox
|
|
- Google
|
|
|
|
The `SessionGuard`, which is added to each (appropriate) controller method of the private API,
|
|
checks if the provided session is still valid and provides the controller method with the correct user.
|