DOCSP-45153 Add MONGODB-OIDC (#152)

(cherry picked from commit 6700bfd)

Author: stephmarie17

source/fundamentals/enterprise-auth.txt

@@ -108,6 +108,138 @@ a connection string URI by using the following placeholders:
 
    let uri = "mongodb://<username>:<password>@<hostname>/?authSource=$external&authMechanism=PLAIN";
 
+.. _rust-mongodb-oidc:
+
+MONGODB-OIDC
+------------
+
+.. important::
+
+   The MONGODB-OIDC authentication mechanism requires MongoDB Server
+   v7.0 or later running on a Linux platform.
+
+The {+driver-short+} supports OpenID Connect (**OIDC**) authentication for **workload
+identities**. A workload identity is an identity you assign to a
+software workload, such as an application, service, script, or
+container, to authenticate and access other services and resources.
+
+The following sections describe how to use the MONGODB-OIDC
+authentication mechanism to authenticate to various platforms.
+
+To learn more about the MONGODB-OIDC authentication mechanism, see
+:manual:`OpenID Connect Authentication </core/security-oidc/>` and
+:manual:`MongoDB Server Parameters </reference/parameters/#mongodb-parameter-param.oidcIdentityProviders>`
+in the Server manual.
+
+.. _rust-mongodb-oidc-azure-imds:
+
+Azure IMDS
+~~~~~~~~~~
+
+If your application runs on an Azure VM, or otherwise uses the
+`Azure Instance Metadata Service <https://learn.microsoft.com/en-us/azure/virtual-machines/instance-metadata-service>`__
+(IMDS), you can authenticate to MongoDB by using the {+driver-short+}'s
+built-in Azure support.
+
+You can configure OIDC for Azure IMDS by setting the ``mechanism`` field of your
+``Credential`` struct to ``AuthMechanism::MongoDbOidc``. This example specifies
+the authentication mechanism by using the following placeholders:
+
+- ``username``:  If you're using an Azure managed identity, set this to the
+  client ID of the managed identity. If you're using a service principal to
+  represent an enterprise application, set this to the application ID of the
+  service principal.
+- ``mechanism_properties``: Set the ``ENVIRONMENT`` property to ``azure`` and
+  the ``TOKEN_RESOURCE`` to the value of the audience parameter configured
+  on your MongoDB deployment.
+
+The following code example shows how to set these options when creating a
+``Client``:
+
+.. literalinclude:: /includes/fundamentals/code-snippets/enterprise-auth.rs
+   :language: rust
+   :dedent:
+   :start-after: start-azure-imds
+   :end-before: end-azure-imds
+   :emphasize-lines: 2-5
+
+.. _rust-mongodb-oidc-gcp-imds:
+
+GCP IMDS
+~~~~~~~~
+
+If your application runs on a Google Compute Engine VM, or otherwise uses the
+`GCP Instance Metadata Service <https://cloud.google.com/compute/docs/metadata/querying-metadata>`__,
+you can authenticate to MongoDB by using the {+driver-short+}'s built-in GCP
+support.
+
+You can configure OIDC for GCP IMDS by setting the ``mechanism`` field of your
+``Credential`` struct to ``AuthMechanism::MongoDbOidc``. Then, specify the
+authentication mechanism by setting the following values in the
+``mechanism_properties`` field:
+
+- ``ENVIRONMENT``: Set this property to ``gcp``.
+- ``TOKEN_RESOURCE``: Set this property to the value of the audience parameter configured
+  on your MongoDB deployment.
+
+The following code example shows how to set these options when creating a
+``Client``:
+
+.. literalinclude:: /includes/fundamentals/code-snippets/enterprise-auth.rs
+   :language: rust
+   :dedent:
+   :start-after: start-gcp-imds
+   :end-before: end-gcp-imds
+   :emphasize-lines: 2-4
+
+.. _rust-mongodb-oidc-custom-callback:
+
+Custom Callback
+~~~~~~~~~~~~~~~
+
+The {+driver-short+} doesn't offer built-in support for all platforms, including
+the AWS Elastic Kubernetes Service (EKS). To use OIDC to authenticate against
+unsupported platforms, you must define a custom callback function.
+
+The following code is an example implementation of a custom callback for an EKS
+cluster. First, set the ``oidc_callback`` field of your ``Credential`` struct to
+``oidc::Callback::machine``. Then, read the access token from a path set in the
+``AWS_WEB_IDENTITY_TOKEN_FILE`` environment variable. Finally, set the value of
+the ``access_token`` field of the ``IdpServerResponse`` struct. Optionally, set
+the values of the ``expires`` and ``refresh_token`` fields.
+
+.. literalinclude:: /includes/fundamentals/code-snippets/enterprise-auth.rs
+   :language: rust
+   :dedent:
+   :start-after: start-custom-callback-machine
+   :end-before: end-custom-callback-machine
+   :emphasize-lines: 3, 5-7
+
+When the workforce identity authentication process involves human interaction,
+you must configure the client by setting the ``oidc_callback`` field of your
+``Credential`` struct to ``oidc::Callback::human`` instead of
+``oidc::Callback::machine``. The {+driver-short+} uses the callback in the
+following process:
+
+1. The driver retrieves the Identity Provider Information (IDPInfo) for the
+   provided username.
+#. The callback negotiates with the IDP to obtain an ``access_token``, and any
+   potential ``refresh_token`` and timeout values, if configured. The callback
+   returns a ``Result<IdpServerInfo>``.
+
+The following example defines a custom callback to handle workforce identity. To
+customize this example for your use case, replace ``<human flow>`` with your own
+custom flow. Refer to `Authorization Code Flow with OIDC
+<https://auth0.com/docs/authenticate/login/oidc-conformant-authentication/oidc-adoption-auth-code-flow>`__
+for more details.
+
+.. literalinclude:: /includes/fundamentals/code-snippets/enterprise-auth.rs
+   :language: rust
+   :dedent:
+   :start-after: start-custom-callback-user
+   :end-before: end-custom-callback-user
+   :emphasize-lines: 3
+
 Additional Information
 ----------------------
 
@@ -129,3 +261,6 @@ guide, see the following API documentation:
 - `ClientOptions <{+api+}/options/struct.ClientOptions.html>`__
 - `Client <{+api+}/struct.Client.html>`__
 - `with_options() <{+api+}/struct.Client.html#method.with_options>`__
+- `CallbackContext <{+api+}/options/oidc/struct.CallbackContext.html>`__
+- `IdpServerResponse <{+api+}/options/oidc/struct.IdpServerResponse.html>`__
+- `IdpServerInfo <{+api+}/options/oidc/struct.IdpServerInfo.html>`__

source/includes/fundamentals/code-snippets/enterprise-auth.rs

@@ -1,4 +1,12 @@
-use mongodb::{ bson::doc, options::{ ClientOptions, Credential, AuthMechanism }, Client };
+use mongodb::options::oidc::{self, Callback, CallbackContext, IdpServerResponse};
+use mongodb::{ 
+    bson::doc, 
+    bson::Document,
+    options::{ClientOptions, Credential, AuthMechanism}, 
+    Client,
+};
+use std::error::Error;
+use futures::FutureExt;
 
 #[tokio::main]
 async fn main() -> mongodb::error::Result<()> {
@@ -17,5 +25,86 @@ async fn main() -> mongodb::error::Result<()> {
     let client = Client::with_options(client_options)?;
     // end-ldap
 
+    // start-azure-imds
+    let credential = Credential::builder()
+        .username("<username>".to_owned())
+        .mechanism(AuthMechanism::MongoDbOidc)
+        .mechanism_properties(
+            doc! { "ENVIRONMENT": "azure", "TOKEN_RESOURCE": "<audience>" }
+        )
+        .build();
+    
+    client_options.credential = Some(credential);
+    let client = Client::with_options(client_options)?;
+    let res = client
+        .database("test")
+        .collection::<Document>("test")
+        .find_one(doc! {})
+        .await?;
+    // end-azure-imds
+
+    // start-gcp-imds
+    let credential = Credential::builder()
+        .mechanism(AuthMechanism::MongoDbOidc)
+        .mechanism_properties(
+            doc! { "ENVIRONMENT": "gcp", "TOKEN_RESOURCE": "<audience>" }
+        )
+        .build();
+    
+    client_options.credential = Some(credential);
+    let client = Client::with_options(client_options)?;
+    let res = client
+        .database("test")
+        .collection::<Document>("test")
+        .find_one(doc! {})
+        .await?;
+    // end-gcp-imds
+
+    // start-custom-callback-machine
+    let credential = Credential::builder()
+    .mechanism(AuthMechanism::MongoDbOidc)
+    .oidc_callback(oidc::Callback::machine(move |_| {
+        async move {
+            let token_file_path = std::env::var("AWS_WEB_IDENTITY_TOKEN_FILE").map_err(mongodb::error::Error::custom)?;
+            let access_token = tokio::fs::read_to_string(token_file_path).await?;
+            Ok(IdpServerResponse::builder().access_token(access_token).build())
+        }
+        .boxed()
+    }))
+    .build()
+    .into();
+
+    client_options.credential = Some(credential);
+    let client = Client::with_options(client_options)?;
+
+    let res = client
+        .database("test")
+        .collection::<Document>("test")
+        .find_one(doc! {})
+        .await?;
+    // end-custom-callback-machine
+
+    // start-custom-callback-user
+    let callback = Callback::human(move |context| {
+        async move {
+            "<human flow>";
+            todo!("human flow")
+        }
+        .boxed()
+    });
+    let credential = Credential::builder()
+        .mechanism(AuthMechanism::MongoDbOidc)
+        .oidc_callback(callback)
+        .build();
+    client_options.credential = Some(credential);
+    let client = Client::with_options(client_options)?;
+
+    let res = client
+        .database("test")
+        .collection::<Document>("test")
+        .find_one(doc! {})
+        .await?;
+    // end-custom-callback-user
+
     Ok(())
 }