Add GMSA support for V2 HCS schema xenon containers

* Add new UVM function 'UpdateHvSockServiceTable' to be able to hot add
Hvsocket service table entries.
* Add disabled field to HvSocketServiceConfig (used to be private in the schema)
* Remove hardcoded error if supplying a cred spec and the client asked for a
hypervisor isolated container.
* Misc refactors (comments, style)

Signed-off-by: Daniel Canter <[email protected]>

internal/hcsoci/credentials.go

@@ -28,26 +28,27 @@ import (
 // setting up instances manually is not needed, the GMSA credential specification
 // simply needs to be present in the V1 container document.
 
-// CCGInstance stores the id used when creating a ccg instance. Used when
+// CCGResource stores the id used when creating a ccg instance. Used when
 // closing a container to be able to release the instance.
-type CCGInstance struct {
+type CCGResource struct {
 	// ID of container that instance belongs to.
 	id string
 }
 
-// Release calls into hcs to remove the ccg instance. These do not get cleaned up automatically
-// they MUST be explicitly removed with a call to ModifyServiceSettings. The instances will persist
-// unless vmcompute.exe exits or they are removed manually as done here.
-func (instance *CCGInstance) Release(ctx context.Context) error {
-	if err := removeCredentialGuard(ctx, instance.id); err != nil {
+// Release calls into hcs to remove the ccg instance for the container matching CCGResource.id.
+// These do not get cleaned up automatically they MUST be explicitly removed with a call to
+// ModifyServiceSettings. The instances will persist unless vmcompute.exe exits or they are removed
+// manually as done here.
+func (ccgResource *CCGResource) Release(ctx context.Context) error {
+	if err := removeCredentialGuard(ctx, ccgResource.id); err != nil {
 		return fmt.Errorf("failed to remove container credential guard instance: %s", err)
 	}
 	return nil
 }
 
 // CreateCredentialGuard creates a container credential guard instance and
 // returns the state object to be placed in a v2 container doc.
-func CreateCredentialGuard(ctx context.Context, id, credSpec string, hypervisorIsolated bool) (*hcsschema.ContainerCredentialGuardState, *CCGInstance, error) {
+func CreateCredentialGuard(ctx context.Context, id, credSpec string, hypervisorIsolated bool) (*hcsschema.ContainerCredentialGuardInstance, *CCGResource, error) {
 	log.G(ctx).WithField("containerID", id).Debug("creating container credential guard instance")
 	// V2 schema ccg setup a little different as its expected to be passed
 	// through all the way to the gcs. Can no longer be enabled just through
@@ -56,19 +57,21 @@ func CreateCredentialGuard(ctx context.Context, id, credSpec string, hypervisorI
 	// 1. Call HcsModifyServiceSettings with a ModificationRequest set with a
 	// ContainerCredentialGuardAddInstanceRequest. This is where the cred spec
 	// gets passed in. Transport either "LRPC" (Argon) or "HvSocket" (Xenon).
+	//
 	// 2. Query the instance with a call to HcsGetServiceProperties with the
 	// PropertyType "ContainerCredentialGuard". This will return all instances
+	//
 	// 3. Parse for the id of our container to find which one correlates to the
 	// container we're building the doc for, then add to the V2 doc.
-	// 4. If xenon container the hvsocketconfig will need to be in the UVMs V2
-	// schema HcsComputeSystem document before being created/sent to HCS. It must
-	// be in the doc at creation time as we do not support hot adding hvsocket
-	// service table entries.
-	// This is currently a blocker for adding support for hyper-v gmsa.
+	//
+	// 4. If xenon container the CCG instance with the Hvsocket service table
+	// information is expected to be in the Utility VMs doc before being sent
+	// to HCS for creation. For pod scenarios currently we don't have the OCI
+	// spec of a container at UVM creation time, therefore the service table entry
+	// for the CCG instance will have to be hot added.
 	transport := "LRPC"
 	if hypervisorIsolated {
-		// TODO(Dcantah) Set transport to HvSocket here when this is supported
-		return nil, nil, errors.New("hypervisor isolated containers with v2 HCS schema do not support GMSA")
+		transport = "HvSocket"
 	}
 	req := hcsschema.ModificationRequest{
 		PropertyType: hcsschema.PTContainerCredentialGuard,
@@ -102,10 +105,10 @@ func CreateCredentialGuard(ctx context.Context, id, credSpec string, hypervisorI
 	}
 	for _, ccgInstance := range ccgSysInfo.Instances {
 		if ccgInstance.Id == id {
-			instance := &CCGInstance{
+			ccgResource := &CCGResource{
 				id,
 			}
-			return ccgInstance.CredentialGuard, instance, nil
+			return &ccgInstance, ccgResource, nil
 		}
 	}
 	return nil, nil, fmt.Errorf("failed to find credential guard instance with container ID %s", id)
@@ -124,8 +127,5 @@ func removeCredentialGuard(ctx context.Context, id string) error {
 			},
 		},
 	}
-	if err := hcs.ModifyServiceSettings(ctx, req); err != nil {
-		return err
-	}
-	return nil
+	return hcs.ModifyServiceSettings(ctx, req)
 }

internal/hcsoci/resources.go

@@ -92,15 +92,14 @@ func ReleaseResources(ctx context.Context, r *Resources, vm *uvm.UtilityVM, all
 				}
 				r.createdNetNS = false
 			}
-		case *CCGInstance:
+		case *CCGResource:
 			if err := r.resources[i].Release(ctx); err != nil {
 				log.G(ctx).WithError(err).Error("failed to release container resource")
 				releaseErr = true
 			}
 		default:
-			// Don't need to check if vm != nil here anymore as they wouldnt
-			// have been added in the first place. All resources have embedded
-			// vm they belong to.
+			// Don't need to check if vm != nil here as they wouldnt have been added
+			// in the first place. All resources have embedded vm they belong to.
 			if all {
 				if err := r.resources[i].Release(ctx); err != nil {
 					log.G(ctx).WithError(err).Error("failed to release container resource")

internal/hcsoci/resources_wcow.go

@@ -131,13 +131,27 @@ func allocateWindowsResources(ctx context.Context, coi *createOptionsInternal, r
 		// Only need to create a CCG instance for v2 containers
 		if schemaversion.IsV21(coi.actualSchemaVersion) {
 			hypervisorIsolated := coi.HostingSystem != nil
-			ccgState, ccgInstance, err := CreateCredentialGuard(ctx, coi.actualID, cs, hypervisorIsolated)
+			ccgInstance, ccgResource, err := CreateCredentialGuard(ctx, coi.actualID, cs, hypervisorIsolated)
 			if err != nil {
 				return err
 			}
-			coi.ccgState = ccgState
-			r.resources = append(r.resources, ccgInstance)
-			//TODO dcantah: If/when dynamic service table entries is supported register the RpcEndpoint with hvsocket here
+			coi.ccgState = ccgInstance.CredentialGuard
+			r.resources = append(r.resources, ccgResource)
+			if hypervisorIsolated {
+				// If hypervisor isolated we need to add an hvsocket service table entry
+				// By default HVSocket won't allow something inside the VM to connect
+				// back to a process on the host. We need to update the HVSocket service table
+				// to allow a connection to CCG.exe on the host, so that GMSA can function.
+				// We need to hot add this here because at UVM creation time we don't know what containers
+				// will be launched in the UVM, nonetheless if they will ask for GMSA. This is a workaround
+				// for the previous design requirement for CCG V2 where the service entry
+				// must be present in the UVM'S HCS document before being sent over as hot adding
+				// an HvSocket service was not possible.
+				hvSockConfig := ccgInstance.HvSocketConfig
+				if err := coi.HostingSystem.UpdateHvSocketService(ctx, hvSockConfig.ServiceId, hvSockConfig.ServiceConfig); err != nil {
+					return fmt.Errorf("failed to update hvsocket service: %s", err)
+				}
+			}
 		}
 	}
 	return nil

internal/schema2/hv_socket_service_config.go

@@ -19,4 +19,6 @@ type HvSocketServiceConfig struct {
 
 	//  If true, HvSocket will process wildcard binds for this service/system combination.  Wildcard binds are secured in the registry at  SOFTWARE/Microsoft/Windows NT/CurrentVersion/Virtualization/HvSocket/WildcardDescriptors
 	AllowWildcardBinds bool `json:"AllowWildcardBinds,omitempty"`
+
+	Disabled bool `json:"Disabled,omitempty"`
 }

internal/uvm/hvsocket.go

@@ -0,0 +1,45 @@
+package uvm
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/Microsoft/hcsshim/internal/requesttype"
+	hcsschema "github.com/Microsoft/hcsshim/internal/schema2"
+)
+
+// UpdateHvSocketService calls HCS to update/create the hvsocket service for
+// the UVM. Takes in a service ID and the hvsocket service configuration. If there is no
+// entry for the service ID already it will be created. The same call on HvSockets side
+// handles the Create/Update/Delete cases based on what is passed in. Here is the logic
+// for the call.
+//
+// 1. If the service ID does not currently exist in the service table, it will be created
+// with whatever descriptors and state was specified (disabled or not).
+// 2. If the service already exists and empty descriptors and Disabled is passed in for the
+// service config, the service will be removed.
+// 3. Otherwise any combination that is not Disabled && Empty descriptors will just update the
+// service.
+//
+// This function should preferably be called for the Update/Create flow but there isn't anything
+// stopping this being used for the delete case. Prefer RemoveHvSocketService as this sets the
+// relevant fields for the Delete case on HCS' side.
+// This is currently only used for updating the service table to allow the UVM to
+// communicate with the Container Credential Guard (ccg.exe) process on the host after being launched.
+func (uvm *UtilityVM) UpdateHvSocketService(ctx context.Context, sid string, doc *hcsschema.HvSocketServiceConfig) error {
+	request := &hcsschema.ModifySettingRequest{
+		RequestType:  requesttype.Update,
+		ResourcePath: fmt.Sprintf(hvsocketConfigResourceFormat, sid),
+		Settings:     doc,
+	}
+	return uvm.modify(ctx, request)
+}
+
+// RemoveHvSocketService will remove an hvsocket service entry if it exists.
+func (uvm *UtilityVM) RemoveHvSocketService(ctx context.Context, sid string) error {
+	request := &hcsschema.ModifySettingRequest{
+		RequestType:  requesttype.Remove,
+		ResourcePath: fmt.Sprintf(hvsocketConfigResourceFormat, sid),
+	}
+	return uvm.modify(ctx, request)
+}

internal/uvm/resourcepaths.go

@@ -18,4 +18,5 @@ const (
 	vPMemControllerResourceFormat    string = "VirtualMachine/Devices/VirtualPMem/Devices/%d"
 	vPMemDeviceResourceFormat        string = "VirtualMachine/Devices/VirtualPMem/Devices/%d/Mappings/%d"
 	vSmbShareResourcePath            string = "VirtualMachine/Devices/VirtualSmb/Shares"
+	hvsocketConfigResourceFormat     string = "VirtualMachine/Devices/HvSocket/HvSocketConfig/ServiceTable/%s"
 )