GODRIVER-2758: Add documentation examples

mongo/client_examples_test.go

@@ -10,6 +10,7 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"os"
 
 	"go.mongodb.org/mongo-driver/bson"
 	"go.mongodb.org/mongo-driver/mongo"
@@ -468,3 +469,252 @@ func ExampleConnect_bSONOptions() {
 		panic(err)
 	}
 }
+
+func ExampleConnect_oIDC() {
+	// The `MONGODB-OIDC authentication mechanism` is available in MongoDB 7.0+
+	// on Linux platforms.
+	//
+	// The MONGODB-OIDC mechanism authenticates using an OpenID Connect (OIDC)
+	// access token. The driver supports OIDC for workload identity, defined as
+	// 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 driver also supports OIDC for workforce identity for a more secure
+	// flow with a human in the loop.
+
+	// Credentials can be configured through the MongoDB URI or as arguments in
+	// the options.ClientOptions struct that is passed into the mongo.Connect
+	// function.
+
+	// Built-in Support
+	// The driver has built-in support for Azure IMDS and GCP
+	// IMDS environments.  Other environments are supported with `Custom
+	// Callbacks`.
+
+	// Azure IMDS
+	// For an application running on an Azure VM or otherwise using the `Azure
+	// Internal Metadata Service`, you can use the built-in support for Azure,
+	// where "<client_id>" below is the client id of the Azure managed identity,
+	// and ``<audience>`` is the url-encoded ``audience`` `configured on your
+	// MongoDB deployment`.
+	{
+		uri := os.Getenv("MONGODB_URI")
+		props := map[string]string{
+			"ENVIRONMENT":    "azure",
+			"TOKEN_RESOURCE": "<audience>",
+		}
+		opts := options.Client().ApplyURI(uri)
+		opts.SetAuth(
+			options.Credential{
+				Username:                "<client_id>",
+				AuthMechanism:           "MONGODB-OIDC",
+				AuthMechanismProperties: props,
+			},
+		)
+		c, err := mongo.Connect(context.TODO(), opts)
+		if err != nil {
+			panic(err)
+		}
+		defer c.Disconnect(context.TODO())
+		c.Database("test").
+			Collection("test").
+			InsertOne(context.TODO(), bson.D{})
+	}
+
+	// If the application is running on an Azure VM and only one managed
+	// identity is associated with the VM, "username" can be omitted.
+
+	// GCP IMDS
+
+	// For an application running on an GCP VM or otherwise using the `GCP
+	// Internal Metadata Service`_, you can use the built-in support for GCP,
+	// where "<audience>" below is the url-encoded "audience" `configured on
+	// your MongoDB deployment`.
+	{
+		uri := os.Getenv("MONGODB_URI")
+		props := map[string]string{
+			"ENVIRONMENT":    "gcp",
+			"TOKEN_RESOURCE": "<audience>",
+		}
+		opts := options.Client().ApplyURI(uri)
+		opts.SetAuth(
+			options.Credential{
+				AuthMechanism:           "MONGODB-OIDC",
+				AuthMechanismProperties: props,
+			},
+		)
+		c, err := mongo.Connect(context.TODO(), opts)
+		if err != nil {
+			panic(err)
+		}
+		defer c.Disconnect(context.TODO())
+		c.Database("test").
+			Collection("test").
+			InsertOne(context.TODO(), bson.D{})
+	}
+
+	// Custom Callbacks
+
+	// For environments that are not directly supported by the driver, you can
+	// use options.OIDCCallback. Some examples are given below.
+
+	// AWS EKS
+
+	// For an EKS Cluster with a configured `IAM OIDC provider`, the token can
+	// be read from a path given by the "AWS_WEB_IDENTITY_TOKEN_FILE"
+	// environment variable.
+	{
+		eksCallback := func(_ context.Context,
+			_ *options.OIDCArgs) (*options.OIDCCredential, error) {
+			accessToken, err := os.ReadFile(
+				os.Getenv("AWS_WEB_IDENTITY_TOKEN_FILE"))
+			if err != nil {
+				return nil, err
+			}
+			return &options.OIDCCredential{
+				AccessToken: string(accessToken),
+			}, nil
+		}
+		uri := os.Getenv("MONGODB_URI")
+		props := map[string]string{
+			"ENVIRONMENT":    "gcp",
+			"TOKEN_RESOURCE": "<audience>",
+		}
+		opts := options.Client().ApplyURI(uri)
+		opts.SetAuth(
+			options.Credential{
+				AuthMechanism:           "MONGODB-OIDC",
+				AuthMechanismProperties: props,
+				OIDCMachineCallback:     eksCallback,
+			},
+		)
+		c, err := mongo.Connect(context.TODO(), opts)
+		if err != nil {
+			panic(err)
+		}
+		defer c.Disconnect(context.TODO())
+		c.Database("test").
+			Collection("test").
+			InsertOne(context.TODO(), bson.D{})
+	}
+
+	// Other Azure Environments
+
+	// For applications running on Azure Functions, App Service Environment
+	// (ASE), or Azure Kubernetes Service (AKS), you can use the `azidentity
+	// package`
+	// (https://pkg.go.dev/github.com/Azure/azure-sdk-for-go/sdk/azidentity) to
+	// fetch the credentials. In each case, the OIDCCallback function should
+	// return the AccessToken from the azidentity package.
+
+	// GCP GKE
+
+	// For a Google Kubernetes Engine cluster with a `configured service
+	// account`, the token can be read from the standard service account token
+	// file location.
+	{
+		gkeCallback := func(_ context.Context,
+			_ *options.OIDCArgs) (*options.OIDCCredential, error) {
+			accessToken, err := os.ReadFile(
+				"/var/run/secrets/kubernetes.io/serviceaccount/token")
+			if err != nil {
+				return nil, err
+			}
+			return &options.OIDCCredential{
+				AccessToken: string(accessToken),
+			}, nil
+		}
+		uri := os.Getenv("MONGODB_URI")
+		props := map[string]string{
+			"ENVIRONMENT":    "gcp",
+			"TOKEN_RESOURCE": "<audience>",
+		}
+		opts := options.Client().ApplyURI(uri)
+		opts.SetAuth(
+			options.Credential{
+				AuthMechanism:           "MONGODB-OIDC",
+				AuthMechanismProperties: props,
+				OIDCMachineCallback:     gkeCallback,
+			},
+		)
+		c, err := mongo.Connect(context.TODO(), opts)
+		if err != nil {
+			panic(err)
+		}
+		defer c.Disconnect(context.TODO())
+		c.Database("test").
+			Collection("test").
+			InsertOne(context.TODO(), bson.D{})
+	}
+
+	// For workforce identity, the Client must be configured with the
+	// OIDCHumanCallback rather than the OIDCMachineCallback. The
+	// OIDCHumanCallback is used by the driver in a process that is two step. In
+	// the first step, the driver retrieves the Identity Prodiver (IDP)
+	// Information (IDPInfo) for the passed username. The OIDCHumanCallback then
+	// needs to negotiate with the IDP in order to obtain an AccessToken,
+	// possible RefreshToken, any timeouts, and return them, similar to the
+	// OIDCMachineCallbacks seen above. See
+	// https://docs.hidglobal.com/dev/auth-service/integration/openid-authentication-flows.html
+	// for more information on various OIDC authentication flows.
+	{
+		humanCallback := func(ctx context.Context,
+			opts *options.OIDCArgs) (*options.OIDCCredential, error) {
+			// idpInfo passed from the driver by asking the MongoDB server for
+			// the info configured for the username
+			idpInfo := opts.IDPInfo
+			// negotiateWithIDP must work with the IdP to obtain an access
+			// token. In many cases this will involve opening a webbrowser or
+			// providing a URL on the command line to a human-in-the-loop who
+			// can give persmissions to the IdP.
+			accessToken, err := negotiateWithIDP(ctx, idpInfo.Issuer)
+			if err != nil {
+				return nil, err
+			}
+			return &options.OIDCCredential{
+				AccessToken: string(accessToken),
+			}, nil
+		}
+		uri := os.Getenv("MONGODB_URI")
+		props := map[string]string{
+			"ENVIRONMENT":    "gcp",
+			"TOKEN_RESOURCE": "<audience>",
+		}
+		opts := options.Client().ApplyURI(uri)
+		opts.SetAuth(
+			options.Credential{
+				AuthMechanism:           "MONGODB-OIDC",
+				AuthMechanismProperties: props,
+				OIDCHumanCallback:       humanCallback,
+			},
+		)
+		c, err := mongo.Connect(context.TODO(), opts)
+		if err != nil {
+			panic(err)
+		}
+		defer c.Disconnect(context.TODO())
+		c.Database("test").
+			Collection("test").
+			InsertOne(context.TODO(), bson.D{})
+	}
+
+	// * MONGODB-OIDC authentication mechanism:
+	// https://www.mongodb.com/docs/manual/core/security-oidc/
+	// * OIDC Identity Provider Configuration:
+	// https://www.mongodb.com/docs/manual/reference/parameters/#mongodb-parameter-param.oidcIdentityProviders
+	// * Azure Internal Metadata Service:
+	// https://learn.microsoft.com/en-us/azure/virtual-machines/instance-metadata-service
+	// * GCP Internal Metadata Service:
+	// https://cloud.google.com/compute/docs/metadata/querying-metadata
+	// * IAM OIDC provider:
+	// https://docs.aws.amazon.com/eks/latest/userguide/enable-iam-roles-for-service-accounts.html
+	// * azure-identity package:
+	// https://pkg.go.dev/github.com/Azure/azure-sdk-for-go/sdk/azidentity
+	// * configured service account:
+	// https://cloud.google.com/kubernetes-engine/docs/how-to/service-accounts
+}
+
+func negotiateWithIDP(_ context.Context, _ string) (string, error) {
+	return "", nil
+}