Enable login from Azure VMs with user-assigned identities (#33)

* accept principal ids from user-assigned identities as well as system-assigned

* vendor after bump to 2019 azure paths

azure.go

@@ -11,7 +11,7 @@ import (
 	"sync"
 	"time"
 
-	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2017-12-01/compute"
+	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2019-07-01/compute"
 	"github.com/Azure/go-autorest/autorest"
 	"github.com/Azure/go-autorest/autorest/azure"
 	"github.com/Azure/go-autorest/autorest/azure/auth"

azure_test.go

@@ -7,7 +7,7 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2017-12-01/compute"
+	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2019-07-01/compute"
 	oidc "github.com/coreos/go-oidc"
 )
 

path_login.go

@@ -6,7 +6,7 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2017-12-01/compute"
+	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2019-07-01/compute"
 	"github.com/Azure/go-autorest/autorest/to"
 	"github.com/hashicorp/errwrap"
 	"github.com/hashicorp/vault/sdk/framework"
@@ -208,7 +208,8 @@ func (b *azureAuthBackend) verifyResource(ctx context.Context, subscriptionID, r
 		return errors.New("subscription_id and resource_group_name are required")
 	}
 
-	var principalID, location *string
+	var location *string
+	principalIDs := map[string]struct{}{}
 
 	switch {
 	// If vmss name is specified, the vm name will be ignored and only the scale set
@@ -224,21 +225,25 @@ func (b *azureAuthBackend) verifyResource(ctx context.Context, subscriptionID, r
 			return errwrap.Wrapf("unable to retrieve virtual machine scale set metadata: {{err}}", err)
 		}
 
-		if vmss.Identity == nil {
-			return errors.New("vmss client did not return identity information")
-		}
-		if vmss.Identity.PrincipalID == nil {
-			return errors.New("vmss principal id is empty")
-		}
-
 		// Check bound scale sets
 		if len(role.BoundScaleSets) > 0 && !strListContains(role.BoundScaleSets, vmssName) {
 			return errors.New("scale set not authorized")
 		}
 
-		principalID = vmss.Identity.PrincipalID
 		location = vmss.Location
 
+		if vmss.Identity == nil {
+			return errors.New("vmss client did not return identity information")
+		}
+		// if system-assigned identity's principal id is available
+		if vmss.Identity.PrincipalID != nil {
+			principalIDs[to.String(vmss.Identity.PrincipalID)] = struct{}{}
+			break
+		}
+		// if not, look for user-assigned identities
+		for _, userIdentity := range vmss.Identity.UserAssignedIdentities {
+			principalIDs[to.String(userIdentity.PrincipalID)] = struct{}{}
+		}
 	case vmName != "":
 		client, err := b.provider.ComputeClient(subscriptionID)
 		if err != nil {
@@ -250,29 +255,32 @@ func (b *azureAuthBackend) verifyResource(ctx context.Context, subscriptionID, r
 			return errwrap.Wrapf("unable to retrieve virtual machine metadata: {{err}}", err)
 		}
 
+		location = vm.Location
+
 		if vm.Identity == nil {
 			return errors.New("vm client did not return identity information")
 		}
-
-		if vm.Identity.PrincipalID == nil {
-			return errors.New("vm principal id is empty")
-		}
-
 		// Check bound scale sets
 		if len(role.BoundScaleSets) > 0 {
 			return errors.New("bound scale set defined but this vm isn't in a scale set")
 		}
-
-		principalID = vm.Identity.PrincipalID
-		location = vm.Location
-
+		// if system-assigned identity's principal id is available
+		if vm.Identity.PrincipalID != nil {
+			principalIDs[to.String(vm.Identity.PrincipalID)] = struct{}{}
+			break
+		}
+		// if not, look for user-assigned identities
+		for _, userIdentity := range vm.Identity.UserAssignedIdentities {
+			principalIDs[to.String(userIdentity.PrincipalID)] = struct{}{}
+		}
 	default:
 		return errors.New("either vm_name or vmss_name is required")
 	}
 
-	// Ensure the principal id for the VM matches the verified token OID
-	if to.String(principalID) != claims.ObjectID {
-		return errors.New("token object id does not match virtual machine principal id")
+	// Ensure the token OID is the principal id of the system-assigned identity
+	// or one of the user-assigned identities of the VM
+	if _, ok := principalIDs[claims.ObjectID]; !ok {
+		return errors.New("token object id does not match virtual machine identities")
 	}
 
 	// Check bound subscriptions

path_login_test.go

@@ -8,7 +8,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2017-12-01/compute"
+	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2019-07-01/compute"
 	oidc "github.com/coreos/go-oidc"
 	"github.com/hashicorp/vault/sdk/helper/policyutil"
 	"github.com/hashicorp/vault/sdk/logical"
@@ -216,6 +216,78 @@ func TestLogin_BoundResourceGroup(t *testing.T) {
 	testLoginFailure(t, b, s, loginData, claims, roleData)
 }
 
+func TestLogin_BoundResourceGroupWithUserAssignedID(t *testing.T) {
+	principalID := "prinID"
+	badPrincipalID := "badID"
+	c := func(vmName string) (compute.VirtualMachine, error) {
+		id := compute.VirtualMachineIdentity{
+			UserAssignedIdentities: map[string]*compute.VirtualMachineIdentityUserAssignedIdentitiesValue{
+				"mockuserassignedmsi": &compute.VirtualMachineIdentityUserAssignedIdentitiesValue{
+					PrincipalID: &principalID,
+				},
+			},
+		}
+		return compute.VirtualMachine{
+			Identity: &id,
+		}, nil
+	}
+	v := func(vmName string) (compute.VirtualMachineScaleSet, error) {
+		id := compute.VirtualMachineScaleSetIdentity{
+			UserAssignedIdentities: map[string]*compute.VirtualMachineScaleSetIdentityUserAssignedIdentitiesValue{
+				"mockuserassignedmsi": &compute.VirtualMachineScaleSetIdentityUserAssignedIdentitiesValue{
+					PrincipalID: &principalID,
+				},
+			},
+		}
+		return compute.VirtualMachineScaleSet{
+			Identity: &id,
+		}, nil
+	}
+	b, s := getTestBackendWithComputeClient(t, c, v)
+
+	roleName := "testrole"
+	rg := "rg"
+	roleData := map[string]interface{}{
+		"name":                  roleName,
+		"policies":              []string{"dev", "prod"},
+		"bound_resource_groups": []string{rg},
+	}
+	testRoleCreate(t, b, s, roleData)
+
+	claims := map[string]interface{}{
+		"exp": time.Now().Add(60 * time.Second).Unix(),
+		"nbf": time.Now().Add(-60 * time.Second).Unix(),
+		"oid": principalID,
+	}
+	badClaims := map[string]interface{}{
+		"exp": time.Now().Add(60 * time.Second).Unix(),
+		"nbf": time.Now().Add(-60 * time.Second).Unix(),
+		"oid": badPrincipalID,
+	}
+
+	loginData := map[string]interface{}{
+		"role": roleName,
+	}
+	testLoginFailure(t, b, s, loginData, claims, roleData)
+
+	loginData["subscription_id"] = "sub"
+	testLoginFailure(t, b, s, loginData, claims, roleData)
+
+	loginData["resource_group_name"] = rg
+	testLoginFailure(t, b, s, loginData, claims, roleData)
+
+	loginData["vmss_name"] = "vmss"
+	testLoginSuccess(t, b, s, loginData, claims, roleData)
+	delete(loginData, "vmss_name")
+
+	loginData["vm_name"] = "vm"
+	testLoginSuccess(t, b, s, loginData, claims, roleData)
+	testLoginFailure(t, b, s, loginData, badClaims, roleData)
+
+	loginData["resource_group_name"] = "bad rg"
+	testLoginFailure(t, b, s, loginData, claims, roleData)
+}
+
 func TestLogin_BoundLocation(t *testing.T) {
 	principalID := "prinID"
 	location := "loc"