A library that authenticates Azure JWT tokens.

Crates.io Chrono on docs.rs

This library will fetch public keys from Microsoft and validate the authenticity of the Tokens and verify that they are issued by Azure and are not tampered with. See further down for details on what this library validates and whay you need to take care of yourself.

This library will send requests to the Microsoft api to get updated keys. The default is to expire the stored keys after 24 hours and fetch new ones since that correspond with the normal key rotation scheme. There is also a default retry fallback where key that doesn't match wil trigger one refresh of the keys (limited to once an hour), just in case the set default is badly synced with the rotation of the Microsoft public keys or Microsoft decides to rotate the keys immideately for some reason. Both of these settings can be configured.

Example

```rust

use azureauthrs::*;

let clientid = "my client id from Azure"; let mut azauth = AzureAuth::new(client_id).unwrap();

let decoded = azauth.validatetoken(TEST_TOKEN)?;

```

Features

```toml

azure_jwt = {version="0.1, default-features = false, features = ["vendored"]}

```

OpenSSL

This library depends on the openssl crate. There are two options: 1. If you have an installation of OpenSSL installed you can most likely compile this library with its default settings. 2. If you don't have OpenSSL libraries installed you can use the vendored feature that will in turn compile the OpenSSL with its vendored feature enabled. This will compile and statically link OpenSSL to the library. You will need a C compiler, Make and Perl installed for it to build.

Windows

Most Windows system will not have OpenSSL installed by default so the easiest way to get the library working is compiling with the vendored feature. Beware that building OpenSSL the first time will require some time.

On windows, the vendored feature requires a small workaround to find the systems root certificates so we will add an additional dependency to fix that. For more information see: https://github.com/alexcrichton/openssl-probe

Alternatives

There is another library: alcoholic_jwt that provides much of the same functionality but on a slightly lower level allowing for using it with other providers as well. If you need more control then take a look at that library.

Performance

When you create a new AzureAuth instance in its default configuration it will trigger two calls to microsoft endpoints (one to get the open connect metadata to get the current jwks_uri and one to fetch the jwk sets). You should create these objects with care and prefer using a reference to one instance. If you're using it on a webserver you should avoid creating a new instance on every connection and rather instanciate one on server start and use a mutex or channels to do validation. Once the keys are loaded the operations should be very fast. More benchmarks are however needed to confirm this, but the current benchmark indicates around 74 nanoseconds to perform a validation on my 2013 Intel Core 2 processor and 36 nanoseconds on a newer i7 3.7 GHz, once the public keys are retrieved (which should only occur every 24h if set up correctly).

Security

This library validates five things: 1. That the token is issued by Azure and is not tampered with 2. That this token is issued for use in your application 3. That the token is not expired 4. That the token is not used before it's valid 5. That the token is not issued in the future 6. That the algorithm the token header specifies the right algorithm*

The validation will Error on a failed validation providing more granularity for library users to find out why the token was rejected.

You'll need:

You will need a private client_id created by Azure for your application to be able to verify that the token is created for your application (and not anyone with a valid Azure token can log in). This is the ID this library needs from you to authenticate that the token vas issued for your application.

You get a verified token parsed for you in return.

You still must take care of:

  1. Validating that the user has the right access to your system
  2. Validating any other information that is important for your use case
  3. If you ask for more information about the user than what is defined in Microsoft ID tokens reference you will need to make a struct that maps to all the fields in the token and use the custom_validation method.

For more information, see this artice: https://docs.microsoft.com/en-us/azure/active-directory/develop/id-tokens

Todo

There are no known errors in the library but there are a few things that could be done to make it better: