feat: Add GSS-TSIG server functionality

gss/apcera.go

@@ -17,6 +17,54 @@ import (
 	"github.com/openshift/gssapi"
 )
 
+func generate(lib *gssapi.Lib, ctx *gssapi.CtxId, msg []byte) ([]byte, error) {
+	message, err := lib.MakeBufferBytes(msg)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		err = multierror.Append(err, message.Release()).ErrorOrNil()
+	}()
+
+	token, err := ctx.GetMIC(gssapi.GSS_C_QOP_DEFAULT, message)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		err = multierror.Append(err, token.Release()).ErrorOrNil()
+	}()
+
+	return token.Bytes(), nil
+}
+
+func verify(lib *gssapi.Lib, ctx *gssapi.CtxId, stripped, mac []byte) error {
+	message, err := lib.MakeBufferBytes(stripped)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		err = multierror.Append(err, message.Release()).ErrorOrNil()
+	}()
+
+	token, err := lib.MakeBufferBytes(mac)
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		err = multierror.Append(err, token.Release()).ErrorOrNil()
+	}()
+
+	if _, err = ctx.VerifyMIC(message, token); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 // Client maps the TKEY name to the context that negotiated it as
 // well as any other internal state.
 type Client struct {
@@ -28,16 +76,14 @@ type Client struct {
 }
 
 // WithConfig sets the Kerberos configuration used.
-func WithConfig(_ string) func(*Client) error {
-	return func(c *Client) error {
-		return errNotSupported
-	}
+func WithConfig[T Client](_ string) Option[T] {
+	return unsupportedOption[T]
 }
 
 // NewClient performs any library initialization necessary.
 // It returns a context handle for any further functions along with any error
 // that occurred.
-func NewClient(dnsClient *dns.Client, options ...func(*Client) error) (*Client, error) {
+func NewClient(dnsClient *dns.Client, options ...Option[Client]) (*Client, error) {
 	client, err := util.CopyDNSClient(dnsClient)
 	if err != nil {
 		return nil, err
@@ -57,8 +103,10 @@ func NewClient(dnsClient *dns.Client, options ...func(*Client) error) (*Client,
 		logger: logr.Discard(),
 	}
 
-	if err := c.setOption(options...); err != nil {
-		return nil, multierror.Append(err, c.lib.Unload())
+	for _, option := range options {
+		if err := option(c); err != nil {
+			return nil, multierror.Append(err, c.lib.Unload())
+		}
 	}
 
 	return c, nil
@@ -72,54 +120,11 @@ func (c *Client) Close() error {
 }
 
 func (c *Client) generate(ctx *gssapi.CtxId, msg []byte) ([]byte, error) {
-	message, err := c.lib.MakeBufferBytes(msg)
-	if err != nil {
-		return nil, err
-	}
-
-	defer func() {
-		err = multierror.Append(err, message.Release()).ErrorOrNil()
-	}()
-
-	token, err := ctx.GetMIC(gssapi.GSS_C_QOP_DEFAULT, message)
-	if err != nil {
-		return nil, err
-	}
-
-	defer func() {
-		err = multierror.Append(err, token.Release()).ErrorOrNil()
-	}()
-
-	return token.Bytes(), nil
+	return generate(c.lib, ctx, msg)
 }
 
 func (c *Client) verify(ctx *gssapi.CtxId, stripped, mac []byte) error {
-	// Turn the TSIG-stripped message bytes into a *gssapi.Buffer
-	message, err := c.lib.MakeBufferBytes(stripped)
-	if err != nil {
-		return err
-	}
-
-	defer func() {
-		err = multierror.Append(err, message.Release()).ErrorOrNil()
-	}()
-
-	// Turn the TSIG MAC bytes into a *gssapi.Buffer
-	token, err := c.lib.MakeBufferBytes(mac)
-	if err != nil {
-		return err
-	}
-
-	defer func() {
-		err = multierror.Append(err, token.Release()).ErrorOrNil()
-	}()
-
-	// This is the actual verification bit
-	if _, err = ctx.VerifyMIC(message, token); err != nil {
-		return err
-	}
-
-	return nil
+	return verify(c.lib, ctx, stripped, mac)
 }
 
 // NegotiateContext exchanges RFC 2930 TKEY records with the indicated DNS
@@ -260,3 +265,150 @@ func (c *Client) DeleteContext(keyname string) error {
 
 	return nil
 }
+
+// Server maps the TKEY name to the context that negotiated it as
+// well as any other internal state.
+type Server struct {
+	m      sync.RWMutex
+	lib    *gssapi.Lib
+	ctx    map[string]*gssapi.CtxId
+	logger logr.Logger
+}
+
+// NewServer performs any library initialization necessary.
+// It returns a context handle for any further functions along with any error
+// that occurred.
+func NewServer(options ...Option[Server]) (*Server, error) {
+	lib, err := gssapi.Load(nil)
+	if err != nil {
+		return nil, err
+	}
+
+	s := &Server{
+		lib:    lib,
+		ctx:    make(map[string]*gssapi.CtxId),
+		logger: logr.Discard(),
+	}
+
+	for _, option := range options {
+		if err := option(s); err != nil {
+			return nil, multierror.Append(err, s.lib.Unload())
+		}
+	}
+
+	return s, nil
+}
+
+// Close deletes any active contexts and unloads any underlying libraries as
+// necessary.
+// It returns any error that occurred.
+func (s *Server) Close() error {
+	return multierror.Append(s.close(true), s.lib.Unload()).ErrorOrNil()
+}
+
+func (s *Server) newContext() (*gssapi.CtxId, error) {
+	//nolint:nilnil
+	return nil, nil
+}
+
+//nolint:funlen
+func (s *Server) update(ctx *gssapi.CtxId, input []byte) (*gssapi.CtxId, []byte, error) {
+	/*var cred *gssapi.CredId
+
+	// equivalent of GSSAPIStrictAcceptorCheck
+	if s.strict { //nolint:nestif
+		hostname, err := osHostname()
+		if err != nil {
+			return nil, "", false, err
+		}
+
+		buffer, err := s.lib.MakeBufferString("host@" + hostname)
+		if err != nil {
+			return nil, "", false, err
+		}
+
+		defer func() {
+			err = multierror.Append(err, buffer.Release()).ErrorOrNil()
+		}()
+
+		service, err := buffer.Name(s.lib.GSS_C_NT_HOSTBASED_SERVICE)
+		if err != nil {
+			return nil, "", false, err
+		}
+
+		defer func() {
+			err = multierror.Append(err, service.Release()).ErrorOrNil()
+		}()
+
+		oids, err := s.lib.MakeOIDSet(s.lib.GSS_MECH_KRB5)
+		if err != nil {
+			return nil, "", false, err
+		}
+
+		defer func() {
+			err = multierror.Append(err, oids.Release()).ErrorOrNil()
+		}()
+
+		cred, _, _, err = s.lib.AcquireCred(service, gssapi.GSS_C_INDEFINITE, oids, gssapi.GSS_C_ACCEPT)
+		if err != nil {
+			return nil, "", false, err
+		}
+
+		defer func() {
+			err = multierror.Append(err, cred.Release()).ErrorOrNil()
+		}()
+	} else {*/
+	cred := s.lib.GSS_C_NO_CREDENTIAL
+	//}
+
+	token, err := s.lib.MakeBufferBytes(input)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	defer func() {
+		err = multierror.Append(err, token.Release()).ErrorOrNil()
+	}()
+
+	//nolint:dogsled
+	nctx, _, _, output, _, _, _, err := s.lib.AcceptSecContext(ctx, cred, token, s.lib.GSS_C_NO_CHANNEL_BINDINGS)
+	if err != nil && !s.lib.LastStatus.Major.ContinueNeeded() {
+		return nil, nil, err
+	}
+
+	defer func() {
+		err = multierror.Append(err, output.Release()).ErrorOrNil()
+	}()
+
+	return nctx, output.Bytes(), nil
+}
+
+func (s *Server) generate(ctx *gssapi.CtxId, msg []byte) ([]byte, error) {
+	return generate(s.lib, ctx, msg)
+}
+
+func (s *Server) verify(ctx *gssapi.CtxId, stripped, mac []byte) error {
+	return verify(s.lib, ctx, stripped, mac)
+}
+
+func (s *Server) established(ctx *gssapi.CtxId) (established bool, err error) {
+	if ctx != nil {
+		_, _, _, _, _, _, established, err = ctx.InquireContext()
+	}
+
+	return
+}
+
+func (s *Server) expired(ctx *gssapi.CtxId) (expired bool, err error) {
+	if ctx != nil {
+		var duration time.Duration
+		_, _, duration, _, _, _, _, err = ctx.InquireContext()
+		expired = duration <= 0
+	}
+
+	return
+}
+
+func (s *Server) delete(ctx *gssapi.CtxId) error {
+	return ctx.DeleteSecContext()
+}

gss/apcera_test.go

@@ -29,3 +29,11 @@ func TestNewClientWithConfig(t *testing.T) {
 	_, err := gss.NewClient(new(dns.Client), gss.WithConfig(""))
 	assert.NotNil(t, err)
 }
+
+func TestNewServer(t *testing.T) {
+	t.Parallel()
+
+	if err := testNewServer(t); err != nil {
+		t.Fatal(err)
+	}
+}

gss/client.go

@@ -68,12 +68,12 @@ func (c *Client) close() error {
 
 	c.m.RUnlock()
 
-	var errs error
+	var err *multierror.Error
 	for _, k := range keys {
-		errs = multierror.Append(errs, c.DeleteContext(k))
+		err = multierror.Append(err, c.DeleteContext(k))
 	}
 
-	return errs
+	return err.ErrorOrNil()
 }
 
 func (c *Client) setOption(options ...func(*Client) error) error {
@@ -87,20 +87,15 @@ func (c *Client) setOption(options ...func(*Client) error) error {
 }
 
 // SetConfig sets the Kerberos configuration used by c.
+//
+// Deprecated: FIXME.
 func (c *Client) SetConfig(config string) error {
 	return c.setOption(WithConfig(config))
 }
 
-// WithLogger sets the logger used.
-func WithLogger(logger logr.Logger) func(*Client) error {
-	return func(c *Client) error {
-		c.logger = logger.WithName("client")
-
-		return nil
-	}
-}
-
 // SetLogger sets the logger used by c.
+//
+// Deprecated: FIXME.
 func (c *Client) SetLogger(logger logr.Logger) error {
-	return c.setOption(WithLogger(logger))
+	return c.setOption(WithLogger[Client](logger))
 }