[management] Add a proxy-connect authorizer seam (#7136)

At proxy connect time, the declared cluster address is validated for
shape and checked for availability (`IsClusterAddressAvailable`), and
from then on the declaration is what routes the cluster's mappings to
the connection. Deployments that embed management through the
integrations seam may need a policy on that claim — deciding which
credential is allowed to declare which address.

This adds an optional `ProxyConnectAuthorizer` hook on
`ProxyServiceServer`, following the pattern of the existing `Set*` seams
(`SetServiceManager`, `SetAgentNetworkSynthesizer`,
`SetAgentNetworkLimitsService`, `SetProxyController`):

- A nil-able interface field plus `SetProxyConnectAuthorizer`, guarded
by the existing mutex.
- One call at the end of `validateProxyConnect`, so both
`GetMappingUpdate` and `SyncMappings` are covered by a single site.
- **Nothing installs it by default** — with the hook unset (always, in
this repo), behavior is byte-for-byte unchanged, which the tests pin.

Design details:

- The authorizer runs **last** — after input validation and the
availability check — and **outside** the account-scoped branch, so
management-wide tokens and token-less connects are also presented to it
rather than bypassing policy.
- The authorizer receives the presented `*types.ProxyAccessToken` (nil
when none), the proxy ID, and the declared address. Everything it needs
is already in the request/context; no proto or schema change.
- A plain error from the authorizer surfaces as `PermissionDenied`,
keeping an authorization rejection distinguishable from the
`AlreadyExists` used for address conflicts in proxy logs. A status error
passes through unchanged so implementations can pick their own code.

management/internals/shared/grpc/proxy.go

@@ -61,6 +61,17 @@ type ProxyTokenChecker interface {
 	IsProxyAccessTokenValid(ctx context.Context, tokenID string) (bool, error)
 }
 
+// ProxyConnectAuthorizer authorizes a proxy's claim to the cluster address it
+// declares at connect time. Implementations are supplied by integrations; none
+// is installed by default, so every well-formed claim is authorized — the
+// declared address is otherwise only checked for availability. token is nil
+// when the connection carries no proxy access token. A returned status error
+// is sent to the proxy unchanged; any other error is wrapped as
+// PermissionDenied.
+type ProxyConnectAuthorizer interface {
+	AuthorizeProxyConnect(ctx context.Context, token *types.ProxyAccessToken, proxyID, address string) error
+}
+
 // ProxyServiceServer implements the ProxyService gRPC server
 // AgentNetworkSynthesizer produces in-memory reverse-proxy services from
 // Agent Network provider/policy state for the proxy snapshot path; synthesised
@@ -99,6 +110,9 @@ type ProxyServiceServer struct {
 	// and the post-flight consumption write (RecordLLMUsage). Optional — when
 	// nil both RPCs return Unimplemented.
 	agentNetworkLimits AgentNetworkLimitsService
+	// connectAuthorizer authorizes address claims at proxy connect time.
+	// Optional — when nil every well-formed claim is authorized.
+	connectAuthorizer ProxyConnectAuthorizer
 	// ProxyController for service updates and cluster management
 	proxyController proxy.Controller
 
@@ -262,6 +276,23 @@ func (s *ProxyServiceServer) agentNetworkSynthesizer() AgentNetworkSynthesizer {
 	return s.agentNetworkSynth
 }
 
+// SetProxyConnectAuthorizer wires the connect-time address-claim authorizer.
+// Optional — when nil (the default) every well-formed claim is authorized,
+// which is the behavior without the hook. The modules layer injects this
+// after the proxy server is constructed, like the other setters.
+func (s *ProxyServiceServer) SetProxyConnectAuthorizer(authorizer ProxyConnectAuthorizer) {
+	s.mu.Lock()
+	s.connectAuthorizer = authorizer
+	s.mu.Unlock()
+}
+
+// proxyConnectAuthorizer returns the connect authorizer under read lock.
+func (s *ProxyServiceServer) proxyConnectAuthorizer() ProxyConnectAuthorizer {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return s.connectAuthorizer
+}
+
 // CheckLLMPolicyLimits is the pre-flight policy gate the proxy calls before
 // forwarding an LLM request upstream. Delegates to the agent-network selector,
 // which scores applicable policies by remaining headroom and returns the
@@ -446,8 +477,9 @@ func recvSyncInit(stream proto.ProxyService_SyncMappingsServer) (*proto.SyncMapp
 	return init, nil
 }
 
-// validateProxyConnect validates the proxy ID and address, and checks cluster
-// address availability for account-scoped tokens.
+// validateProxyConnect validates the proxy ID and address, checks cluster
+// address availability for account-scoped tokens, and finally consults the
+// connect authorizer (when installed) on the address claim.
 func (s *ProxyServiceServer) validateProxyConnect(proxyID, address string, ctx context.Context) (proxyConnectParams, error) {
 	if proxyID == "" {
 		return proxyConnectParams{}, status.Errorf(codes.InvalidArgument, "proxy_id is required")
@@ -467,6 +499,19 @@ func (s *ProxyServiceServer) validateProxyConnect(proxyID, address string, ctx c
 		}
 	}
 
+	// The authorizer runs last, outside the account-scoped branch, so it also
+	// sees management-wide and token-less connects. PermissionDenied keeps an
+	// authorization rejection distinguishable from the AlreadyExists address
+	// conflict above in proxy logs.
+	if authorizer := s.proxyConnectAuthorizer(); authorizer != nil {
+		if err := authorizer.AuthorizeProxyConnect(ctx, token, proxyID, address); err != nil {
+			if _, ok := status.FromError(err); ok {
+				return proxyConnectParams{}, err
+			}
+			return proxyConnectParams{}, status.Errorf(codes.PermissionDenied, "proxy connect not authorized: %v", err)
+		}
+	}
+
 	return proxyConnectParams{proxyID: proxyID, address: address}, nil
 }
 

management/internals/shared/grpc/proxy_connect_authorizer_test.go

@@ -0,0 +1,168 @@
+package grpc
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/codes"
+	grpcstatus "google.golang.org/grpc/status"
+
+	"github.com/netbirdio/netbird/management/internals/modules/reverseproxy/proxy"
+	"github.com/netbirdio/netbird/management/server/types"
+)
+
+// capturingAuthorizer records the arguments of the last AuthorizeProxyConnect
+// call and returns a fixed error.
+type capturingAuthorizer struct {
+	called  int
+	token   *types.ProxyAccessToken
+	proxyID string
+	address string
+	err     error
+}
+
+func (a *capturingAuthorizer) AuthorizeProxyConnect(_ context.Context, token *types.ProxyAccessToken, proxyID, address string) error {
+	a.called++
+	a.token = token
+	a.proxyID = proxyID
+	a.address = address
+	return a.err
+}
+
+// authorizerServer builds a ProxyServiceServer whose proxy manager reports
+// every cluster address as available, so the authorizer is the only thing
+// standing between a claim and success.
+func authorizerServer(t *testing.T) *ProxyServiceServer {
+	t.Helper()
+	ctrl := gomock.NewController(t)
+	mgr := proxy.NewMockManager(ctrl)
+	mgr.EXPECT().IsClusterAddressAvailable(gomock.Any(), gomock.Any(), gomock.Any()).Return(true, nil).AnyTimes()
+	return &ProxyServiceServer{proxyManager: mgr}
+}
+
+// TestValidateProxyConnect_NilAuthorizerUnchanged guards the no-behavior-change
+// claim: with no authorizer installed — the OSS default — a well-formed claim
+// succeeds and malformed input is rejected exactly as before the hook existed.
+func TestValidateProxyConnect_NilAuthorizerUnchanged(t *testing.T) {
+	s := authorizerServer(t)
+
+	params, err := s.validateProxyConnect("proxy-1", "cluster.example.com", scopedCtx("acc-1"))
+	require.NoError(t, err)
+	assert.Equal(t, "proxy-1", params.proxyID)
+	assert.Equal(t, "cluster.example.com", params.address)
+
+	_, err = s.validateProxyConnect("", "cluster.example.com", scopedCtx("acc-1"))
+	require.Error(t, err)
+	st, ok := grpcstatus.FromError(err)
+	require.True(t, ok)
+	assert.Equal(t, codes.InvalidArgument, st.Code(), "missing proxy_id must stay InvalidArgument")
+
+	_, err = s.validateProxyConnect("proxy-1", "not a hostname", scopedCtx("acc-1"))
+	require.Error(t, err)
+	st, ok = grpcstatus.FromError(err)
+	require.True(t, ok)
+	assert.Equal(t, codes.InvalidArgument, st.Code(), "invalid address must stay InvalidArgument")
+}
+
+// TestValidateProxyConnect_AuthorizerReceivesClaim pins the hook contract: the
+// authorizer sees the presented token and the claimed proxy ID and address,
+// and an authorized claim proceeds.
+func TestValidateProxyConnect_AuthorizerReceivesClaim(t *testing.T) {
+	s := authorizerServer(t)
+	auth := &capturingAuthorizer{}
+	s.SetProxyConnectAuthorizer(auth)
+
+	params, err := s.validateProxyConnect("proxy-1", "cluster.example.com", scopedCtx("acc-1"))
+	require.NoError(t, err)
+	assert.Equal(t, "cluster.example.com", params.address)
+
+	require.Equal(t, 1, auth.called, "authorizer must be consulted exactly once per connect")
+	assert.Equal(t, "proxy-1", auth.proxyID)
+	assert.Equal(t, "cluster.example.com", auth.address)
+	require.NotNil(t, auth.token, "the presented token must be handed to the authorizer")
+	require.NotNil(t, auth.token.AccountID)
+	assert.Equal(t, "acc-1", *auth.token.AccountID)
+}
+
+// TestValidateProxyConnect_PlainErrorBecomesPermissionDenied pins the error
+// mapping: a non-status error from the authorizer surfaces as
+// PermissionDenied — distinguishable from the AlreadyExists used for address
+// conflicts — and the claim does not proceed even though the address itself
+// was available.
+func TestValidateProxyConnect_PlainErrorBecomesPermissionDenied(t *testing.T) {
+	s := authorizerServer(t)
+	s.SetProxyConnectAuthorizer(&capturingAuthorizer{err: errors.New("not the assigned credential")})
+
+	_, err := s.validateProxyConnect("proxy-1", "cluster.example.com", scopedCtx("acc-1"))
+	require.Error(t, err)
+	st, ok := grpcstatus.FromError(err)
+	require.True(t, ok)
+	assert.Equal(t, codes.PermissionDenied, st.Code())
+	assert.Contains(t, st.Message(), "not the assigned credential", "the authorizer's reason must survive into the status message")
+}
+
+// TestValidateProxyConnect_StatusErrorPassesThrough pins that an authorizer
+// which chooses its own status code is not second-guessed.
+func TestValidateProxyConnect_StatusErrorPassesThrough(t *testing.T) {
+	s := authorizerServer(t)
+	s.SetProxyConnectAuthorizer(&capturingAuthorizer{
+		err: grpcstatus.Errorf(codes.ResourceExhausted, "try later"),
+	})
+
+	_, err := s.validateProxyConnect("proxy-1", "cluster.example.com", scopedCtx("acc-1"))
+	require.Error(t, err)
+	st, ok := grpcstatus.FromError(err)
+	require.True(t, ok)
+	assert.Equal(t, codes.ResourceExhausted, st.Code(), "a status error must pass through unchanged")
+	assert.Equal(t, "try later", st.Message())
+}
+
+// TestValidateProxyConnect_AuthorizerSeesGlobalAndTokenlessConnects pins the
+// call-site placement: the authorizer sits outside the account-scoped branch,
+// so management-wide tokens (AccountID == nil) and connections without any
+// token are also presented to it rather than bypassing policy.
+func TestValidateProxyConnect_AuthorizerSeesGlobalAndTokenlessConnects(t *testing.T) {
+	s := &ProxyServiceServer{} // no proxy manager: neither path may reach the availability check
+
+	auth := &capturingAuthorizer{}
+	s.SetProxyConnectAuthorizer(auth)
+
+	_, err := s.validateProxyConnect("proxy-1", "cluster.example.com", globalCtx())
+	require.NoError(t, err)
+	require.Equal(t, 1, auth.called, "a management-wide token must still be presented to the authorizer")
+	require.NotNil(t, auth.token)
+	assert.Nil(t, auth.token.AccountID)
+
+	_, err = s.validateProxyConnect("proxy-1", "cluster.example.com", context.Background())
+	require.NoError(t, err)
+	require.Equal(t, 2, auth.called, "a token-less connect must still be presented to the authorizer")
+	assert.Nil(t, auth.token, "no token in context must surface as a nil token, not a zero value")
+}
+
+// TestValidateProxyConnect_AuthorizerRunsLast pins the ordering: input
+// validation and the availability check precede policy, so the authorizer is
+// never consulted about a claim that is malformed or already rejected.
+func TestValidateProxyConnect_AuthorizerRunsLast(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	mgr := proxy.NewMockManager(ctrl)
+	mgr.EXPECT().IsClusterAddressAvailable(gomock.Any(), gomock.Any(), gomock.Any()).Return(false, nil)
+	s := &ProxyServiceServer{proxyManager: mgr}
+
+	auth := &capturingAuthorizer{}
+	s.SetProxyConnectAuthorizer(auth)
+
+	_, err := s.validateProxyConnect("proxy-1", "not a hostname", scopedCtx("acc-1"))
+	require.Error(t, err)
+	assert.Zero(t, auth.called, "a malformed address must be rejected before policy runs")
+
+	_, err = s.validateProxyConnect("proxy-1", "cluster.example.com", scopedCtx("acc-1"))
+	require.Error(t, err)
+	st, ok := grpcstatus.FromError(err)
+	require.True(t, ok)
+	assert.Equal(t, codes.AlreadyExists, st.Code(), "an address conflict must keep its own status")
+	assert.Zero(t, auth.called, "a conflicting address must be rejected before policy runs")
+}