[management] Deny reverse proxy access to pending and blocked users (#7105)

A user in the Pending Approval state could complete SSO and reach any
SSO-protected reverse proxy service distributed to a group they belong
to, including the All Users group. The reverse proxy authorization path
checked the session token signature, that the user exists, that the
user's account matches the service's account, and group membership —
never the user's account status. The REST API (`permissions/manager.go`)
and peer registration both gate on that state, but the proxy gRPC
service does not go through the permissions manager, so neither gate
applied. A pending user is persisted as blocked and pending approval, so
blocked users reached those services the same way.

`ValidateSession` now denies on account status, reporting
`pending_approval` or `user_blocked` so the proxy access log and the
denied page carry the cause rather than a generic refusal.
`GenerateSessionToken` refuses to mint a token for such a user at all,
so the browser never receives a session cookie and the OIDC callback can
tell the user why instead of showing "Service configuration error".
`ValidateUserGroupAccess` and `ValidateTunnelPeer` close the same gap;
for the tunnel path this covers a user blocked after their peer was
registered, since peer group membership alone kept mesh-origin access
open.

A single helper produces both the denied reason for the RPC responses
and the sentinel error for the error-returning callers, so the four
entry points cannot drift apart. A user the store cannot resolve is
denied rather than passed through.

One thing deliberately left out: session cookies are validated locally
by the proxy against the service public key with no management
round-trip, so a cookie issued before a user is blocked stays valid
until it expires (24h by default). That is a revocation-propagation
problem rather than this authorization gap, and every option for it
(per-request validation with a cache, short-lived tokens with refresh,
push-based revocation) changes the proxy hot path or the
proxy/management protocol. Worth its own ticket.

management/internals/shared/grpc/proxy.go

@@ -29,6 +29,7 @@ import (
 
 	"github.com/netbirdio/netbird/shared/management/domain"
 
+	"github.com/netbirdio/netbird/management/internals/modules/agentnetwork"
 	"github.com/netbirdio/netbird/management/internals/modules/peers"
 	"github.com/netbirdio/netbird/management/internals/modules/reverseproxy/accesslogs"
 	"github.com/netbirdio/netbird/management/internals/modules/reverseproxy/proxy"
@@ -36,7 +37,6 @@ import (
 	"github.com/netbirdio/netbird/management/internals/modules/reverseproxy/sessionkey"
 	"github.com/netbirdio/netbird/management/server/idp"
 	"github.com/netbirdio/netbird/management/server/peer"
-	"github.com/netbirdio/netbird/management/internals/modules/agentnetwork"
 	"github.com/netbirdio/netbird/management/server/types"
 	"github.com/netbirdio/netbird/management/server/users"
 	proxyauth "github.com/netbirdio/netbird/proxy/auth"
@@ -1579,9 +1579,62 @@ func (s *ProxyServiceServer) ValidateState(state string) (verifier, redirectURL
 	return verifier, redirectURL, nil
 }
 
+// Denied reasons reported to the proxy when access is refused because of the
+// account status of the user behind the request.
+const (
+	deniedReasonPendingApproval = "pending_approval"
+	deniedReasonUserBlocked     = "user_blocked"
+	deniedReasonUserNotFound    = "user_not_found"
+)
+
+var (
+	// ErrUserPendingApproval reports a user whose account still awaits approval
+	// by an administrator and may therefore not hold a proxy session.
+	ErrUserPendingApproval = errors.New("user pending approval")
+
+	// ErrUserBlocked reports a blocked user, who may not hold a proxy session.
+	ErrUserBlocked = errors.New("user blocked")
+
+	errUserUnresolved = errors.New("user could not be resolved")
+)
+
+// checkUserStatus reports whether the user's account status permits reverse
+// proxy access, returning the denied reason for the proxy access log together
+// with the sentinel error callers match on. A user awaiting approval is stored
+// as both pending and blocked, so the pending state is reported first: it is
+// the one an administrator can act on.
+func checkUserStatus(user *types.User) (string, error) {
+	switch {
+	case user == nil:
+		return deniedReasonUserNotFound, errUserUnresolved
+	case user.PendingApproval:
+		return deniedReasonPendingApproval, ErrUserPendingApproval
+	case user.IsBlocked():
+		return deniedReasonUserBlocked, ErrUserBlocked
+	default:
+		return "", nil
+	}
+}
+
+// userStatusDeniedReason returns the denied reason for callers that report a
+// decision rather than an error, and an empty string when the user may proceed.
+func userStatusDeniedReason(user *types.User) string {
+	reason, _ := checkUserStatus(user)
+	return reason
+}
+
+// sameAccount reports whether a user belongs to a service's account. An empty
+// identifier on either side never matches: two unset accounts must not compare
+// equal into a grant.
+func sameAccount(userAccountID, serviceAccountID string) bool {
+	return userAccountID != "" && serviceAccountID != "" && userAccountID == serviceAccountID
+}
+
 // GenerateSessionToken creates a signed session JWT for the given domain and
 // user. The user's group memberships are embedded in the token so policy-aware
 // middlewares on the proxy can authorise without an extra management round-trip.
+// A user the store cannot resolve, or whose account is pending approval or
+// blocked, gets no token at all, so the browser never receives a session cookie.
 func (s *ProxyServiceServer) GenerateSessionToken(ctx context.Context, domain, userID string, method proxyauth.Method) (string, error) {
 	service, err := s.getServiceByDomain(ctx, domain)
 	if err != nil {
@@ -1592,25 +1645,37 @@ func (s *ProxyServiceServer) GenerateSessionToken(ctx context.Context, domain, u
 		return "", fmt.Errorf("no session key configured for domain: %s", domain)
 	}
 
-	var (
-		email      string
-		groupIDs   []string
-		groupNames []string
-	)
-	if s.usersManager != nil {
-		user, userGroups, uerr := s.usersManager.GetUserWithGroups(ctx, userID)
-		if uerr != nil {
-			log.WithContext(ctx).Debugf("session token mint: lookup user %s: %v", userID, uerr)
-		} else if user != nil {
-			email = user.Email
-			groupIDs, groupNames = pairGroupIDsAndNames(userGroups)
-		}
+	if s.usersManager == nil {
+		return "", errors.New("users manager not configured")
 	}
 
+	user, userGroups, err := s.usersManager.GetUserWithGroups(ctx, userID)
+	if err != nil {
+		return "", fmt.Errorf("get user %s: %w", userID, err)
+	}
+
+	if user == nil {
+		return "", fmt.Errorf("get user %s: %w", userID, errUserUnresolved)
+	}
+
+	// Bind the OIDC identity to the service's account before signing anything
+	// with that service's session key. The proxy validates an installed cookie
+	// locally against the service public key, so a token minted for a user of
+	// another account would be honoured without a management round-trip.
+	if !sameAccount(user.AccountID, service.AccountID) {
+		return "", fmt.Errorf("user %s does not belong to the service account", userID)
+	}
+
+	if _, err := checkUserStatus(user); err != nil {
+		return "", fmt.Errorf("session token for user %s: %w", userID, err)
+	}
+
+	groupIDs, groupNames := pairGroupIDsAndNames(userGroups)
+
 	return sessionkey.SignToken(
 		service.SessionPrivateKey,
 		userID,
-		email,
+		user.Email,
 		domain,
 		method,
 		groupIDs,
@@ -1628,6 +1693,10 @@ func (s *ProxyServiceServer) ValidateUserGroupAccess(ctx context.Context, domain
 		return fmt.Errorf("user not found: %s", userID)
 	}
 
+	if _, err := checkUserStatus(user); err != nil {
+		return fmt.Errorf("user %s denied access to domain %s: %w", userID, domain, err)
+	}
+
 	service, err := s.getAccountServiceByDomain(ctx, user.AccountID, domain)
 	if err != nil {
 		return err
@@ -1682,10 +1751,7 @@ func (s *ProxyServiceServer) ValidateSession(ctx context.Context, req *proto.Val
 	sessionToken := req.GetSessionToken()
 
 	if domain == "" || sessionToken == "" {
-		return &proto.ValidateSessionResponse{
-			Valid:        false,
-			DeniedReason: "missing domain or session_token",
-		}, nil
+		return deniedSessionResponse("missing domain or session_token"), nil
 	}
 
 	service, err := s.getServiceByDomain(ctx, domain)
@@ -1695,83 +1761,49 @@ func (s *ProxyServiceServer) ValidateSession(ctx context.Context, req *proto.Val
 			"error":  err.Error(),
 		}).Debug("ValidateSession: service not found")
 		//nolint:nilerr
-		return &proto.ValidateSessionResponse{
-			Valid:        false,
-			DeniedReason: "service_not_found",
-		}, nil
+		return deniedSessionResponse("service_not_found"), nil
 	}
 
 	if err := enforceAccountScope(ctx, service.AccountID); err != nil {
 		return nil, err
 	}
 
-	pubKeyBytes, err := base64.StdEncoding.DecodeString(service.SessionPublicKey)
-	if err != nil {
-		log.WithFields(log.Fields{
-			"domain": domain,
-			"error":  err.Error(),
-		}).Error("ValidateSession: decode public key")
-		//nolint:nilerr
-		return &proto.ValidateSessionResponse{
-			Valid:        false,
-			DeniedReason: "invalid_service_config",
-		}, nil
-	}
-
-	userID, _, _, _, _, err := proxyauth.ValidateSessionJWT(sessionToken, domain, pubKeyBytes)
-	if err != nil {
-		log.WithFields(log.Fields{
-			"domain": domain,
-			"error":  err.Error(),
-		}).Debug("ValidateSession: invalid session token")
-		//nolint:nilerr
-		return &proto.ValidateSessionResponse{
-			Valid:        false,
-			DeniedReason: "invalid_token",
-		}, nil
+	userID, reason := sessionTokenSubject(domain, service, sessionToken)
+	if reason != "" {
+		return deniedSessionResponse(reason), nil
 	}
 
 	user, userGroups, err := s.usersManager.GetUserWithGroups(ctx, userID)
-	if err != nil {
+	if err != nil || user == nil {
 		log.WithFields(log.Fields{
 			"domain":  domain,
 			"user_id": userID,
-			"error":   err.Error(),
+			"error":   err,
 		}).Debug("ValidateSession: user not found")
 		//nolint:nilerr
-		return &proto.ValidateSessionResponse{
-			Valid:        false,
-			DeniedReason: "user_not_found",
-		}, nil
+		return deniedSessionResponse(deniedReasonUserNotFound), nil
 	}
 
-	if user.AccountID != service.AccountID {
+	// A user from another account gets a bare response: none of their identity
+	// belongs in an answer to a proxy serving a different account.
+	if !sameAccount(user.AccountID, service.AccountID) {
 		log.WithFields(log.Fields{
 			"domain":          domain,
 			"user_id":         userID,
 			"user_account":    user.AccountID,
 			"service_account": service.AccountID,
 		}).Debug("ValidateSession: user account mismatch")
-		//nolint:nilerr
-		return &proto.ValidateSessionResponse{
-			Valid:        false,
-			DeniedReason: "account_mismatch",
-		}, nil
+		return deniedSessionResponse("account_mismatch"), nil
 	}
 
-	if err := s.checkGroupAccess(service, user); err != nil {
-		log.WithFields(log.Fields{
-			"domain":  domain,
-			"user_id": userID,
-			"error":   err.Error(),
-		}).Debug("ValidateSession: access denied")
-		groupIDs, groupNames := pairGroupIDsAndNames(userGroups)
-		//nolint:nilerr
+	groupIDs, groupNames := pairGroupIDsAndNames(userGroups)
+
+	if reason := s.accountUserDeniedReason(domain, service, user); reason != "" {
 		return &proto.ValidateSessionResponse{
 			Valid:          false,
 			UserId:         user.Id,
 			UserEmail:      user.Email,
-			DeniedReason:   "not_in_group",
+			DeniedReason:   reason,
 			PeerGroupIds:   groupIDs,
 			PeerGroupNames: groupNames,
 		}, nil
@@ -1783,7 +1815,6 @@ func (s *ProxyServiceServer) ValidateSession(ctx context.Context, req *proto.Val
 		"email":   user.Email,
 	}).Debug("ValidateSession: access granted")
 
-	groupIDs, groupNames := pairGroupIDsAndNames(userGroups)
 	return &proto.ValidateSessionResponse{
 		Valid:          true,
 		UserId:         user.Id,
@@ -1793,6 +1824,66 @@ func (s *ProxyServiceServer) ValidateSession(ctx context.Context, req *proto.Val
 	}, nil
 }
 
+// deniedSessionResponse builds a denial that carries no identity, for the
+// checks that run before a user of this service's account is resolved.
+func deniedSessionResponse(reason string) *proto.ValidateSessionResponse {
+	return &proto.ValidateSessionResponse{
+		Valid:        false,
+		DeniedReason: reason,
+	}
+}
+
+// sessionTokenSubject verifies the session token against the service's session
+// key and returns the user it was minted for, or the reason it cannot be
+// trusted.
+func sessionTokenSubject(domain string, service *rpservice.Service, sessionToken string) (userID, deniedReason string) {
+	pubKeyBytes, err := base64.StdEncoding.DecodeString(service.SessionPublicKey)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"domain": domain,
+			"error":  err.Error(),
+		}).Error("ValidateSession: decode public key")
+		return "", "invalid_service_config"
+	}
+
+	userID, _, _, _, _, err = proxyauth.ValidateSessionJWT(sessionToken, domain, pubKeyBytes)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"domain": domain,
+			"error":  err.Error(),
+		}).Debug("ValidateSession: invalid session token")
+		return "", "invalid_token"
+	}
+
+	return userID, ""
+}
+
+// accountUserDeniedReason gates a user of the service's own account, returning
+// an empty string when access is granted. Account status comes before group
+// membership: a user awaiting approval or blocked has no access regardless of
+// the groups they were auto-assigned.
+func (s *ProxyServiceServer) accountUserDeniedReason(domain string, service *rpservice.Service, user *types.User) string {
+	if reason := userStatusDeniedReason(user); reason != "" {
+		log.WithFields(log.Fields{
+			"domain":  domain,
+			"user_id": user.Id,
+			"reason":  reason,
+		}).Debug("ValidateSession: user status denies access")
+		return reason
+	}
+
+	if err := s.checkGroupAccess(service, user); err != nil {
+		log.WithFields(log.Fields{
+			"domain":  domain,
+			"user_id": user.Id,
+			"error":   err.Error(),
+		}).Debug("ValidateSession: access denied")
+		return "not_in_group"
+	}
+
+	return ""
+}
+
 func (s *ProxyServiceServer) getServiceByDomain(ctx context.Context, domain string) (*rpservice.Service, error) {
 	service, err := s.serviceManager.GetServiceByDomain(ctx, domain)
 	if err == nil {
@@ -1907,7 +1998,20 @@ func (s *ProxyServiceServer) ValidateTunnelPeer(ctx context.Context, req *proto.
 	}
 
 	groupIDs, groupNames := pairGroupIDsAndNames(peerGroups)
-	principalID, displayIdentity := s.getTunnelPeerInfo(ctx, domain, service, peer)
+	owner := s.resolvePeerOwner(ctx, peer, service.AccountID)
+	principalID, displayIdentity := s.getTunnelPeerInfo(ctx, domain, service, peer, owner)
+
+	if reason := peerOwnerDeniedReason(peer, owner); reason != "" {
+		log.WithFields(log.Fields{"domain": domain, "peer_id": peer.ID, "user_id": peer.UserID, "reason": reason}).Debug("ValidateTunnelPeer: owner status denies access")
+		return &proto.ValidateTunnelPeerResponse{
+			Valid:          false,
+			UserId:         principalID,
+			UserEmail:      displayIdentity,
+			DeniedReason:   reason,
+			PeerGroupIds:   groupIDs,
+			PeerGroupNames: groupNames,
+		}, nil
+	}
 
 	if err := checkPeerGroupAccess(service, groupIDs); err != nil {
 		log.WithFields(log.Fields{"domain": domain, "peer_id": peer.ID, "error": err.Error()}).Debug("ValidateTunnelPeer: access denied")
@@ -1944,9 +2048,55 @@ func (s *ProxyServiceServer) ValidateTunnelPeer(ctx context.Context, req *proto.
 	}, nil
 }
 
+// resolvePeerOwner returns the user a peer is linked to, once per request so
+// the status gate and the identity resolution below share a single lookup.
+// Unlinked peers (machine agents) have no owner. A lookup that fails returns
+// nil rather than an error: both callers treat an unresolved owner the same
+// way, and neither may trust one it could not read.
+func (s *ProxyServiceServer) resolvePeerOwner(ctx context.Context, peer *peer.Peer, accountID string) *types.User {
+	if peer.UserID == "" {
+		return nil
+	}
+
+	user, err := s.usersManager.GetUser(ctx, peer.UserID)
+	if err != nil {
+		log.WithContext(ctx).Debugf("ValidateTunnelPeer: look up owner %s of peer %s: %v", peer.UserID, peer.ID, err)
+		return nil
+	}
+
+	// The lookup is by user ID alone, so a peer row pointing outside the
+	// service's account would otherwise resolve a foreign user. Leave the owner
+	// unresolved instead: the gate denies it, and neither the response nor the
+	// minted token carries an identity from another account.
+	if !sameAccount(user.AccountID, accountID) {
+		log.WithContext(ctx).Debugf("ValidateTunnelPeer: owner %s of peer %s belongs to another account", peer.UserID, peer.ID)
+		return nil
+	}
+
+	return user
+}
+
+// peerOwnerDeniedReason gates the mesh fast-path on the account status of the
+// peer's owning user, so a user blocked after registering a peer loses
+// mesh-origin access too. Unlinked peers (machine agents) have no owner to gate
+// on and stay first-class callers. An owner the store cannot resolve denies:
+// an unavailable lookup must not grant access.
+func peerOwnerDeniedReason(peer *peer.Peer, owner *types.User) string {
+	if peer.UserID == "" {
+		return ""
+	}
+
+	if owner == nil {
+		return deniedReasonUserNotFound
+	}
+
+	return userStatusDeniedReason(owner)
+}
+
 // getTunnelPeerInfo returns the principal ID and display name for a peer, e.g. a
-// user or peer ID, and peer name or user email.
-func (s *ProxyServiceServer) getTunnelPeerInfo(ctx context.Context, domain string, service *rpservice.Service, peer *peer.Peer) (string, string) {
+// user or peer ID, and peer name or user email. owner is the already-resolved
+// user the peer is linked to, or nil.
+func (s *ProxyServiceServer) getTunnelPeerInfo(ctx context.Context, domain string, service *rpservice.Service, peer *peer.Peer, owner *types.User) (string, string) {
 	// Resolve the principal: when the peer is linked to a user, the human is the
 	// principal so multiple peers owned by the same user share a single
 	// identity. Unlinked peers (machine agents) are their own principal keyed on
@@ -1963,10 +2113,10 @@ func (s *ProxyServiceServer) getTunnelPeerInfo(ctx context.Context, domain strin
 	principalID := peer.UserID
 	displayIdentity := peer.Name
 	// Stored column first (cheap, but often empty for OIDC-provisioned users).
-	if user, uerr := s.usersManager.GetUser(ctx, peer.UserID); uerr == nil && user != nil {
-		principalID = user.Id
-		if user.Email != "" {
-			displayIdentity = user.Email
+	if owner != nil {
+		principalID = owner.Id
+		if owner.Email != "" {
+			displayIdentity = owner.Email
 		}
 	}
 	// IdP enrichment wins when available — the stored email column is a

management/internals/shared/grpc/proxy_group_access_test.go

@@ -119,11 +119,13 @@ func (m *mockReverseProxyManager) GetClusters(_ context.Context, _, _ string) ([
 }
 
 type mockUsersManager struct {
-	users map[string]*types.User
-	err   error
+	users        map[string]*types.User
+	err          error
+	getUserCalls int
 }
 
 func (m *mockUsersManager) GetUser(ctx context.Context, userID string) (*types.User, error) {
+	m.getUserCalls++
 	if m.err != nil {
 		return nil, m.err
 	}
@@ -350,6 +352,64 @@ func TestValidateUserGroupAccess(t *testing.T) {
 			},
 			expectErr: false,
 		},
+		{
+			name:   "user pending approval denied despite group membership",
+			domain: "app.example.com",
+			userID: "user1",
+			proxiesByAccount: map[string][]*service.Service{
+				"account1": {{
+					Domain:    "app.example.com",
+					AccountID: "account1",
+					Auth: service.AuthConfig{
+						BearerAuth: &service.BearerAuthConfig{
+							Enabled:            true,
+							DistributionGroups: []string{"group1"},
+						},
+					},
+				}},
+			},
+			users: map[string]*types.User{
+				// The approval flow stores a pending user as blocked as well.
+				"user1": {Id: "user1", AccountID: "account1", AutoGroups: []string{"group1"}, Blocked: true, PendingApproval: true},
+			},
+			expectErr:    true,
+			expectErrMsg: "user pending approval",
+		},
+		{
+			name:   "blocked user denied despite group membership",
+			domain: "app.example.com",
+			userID: "user1",
+			proxiesByAccount: map[string][]*service.Service{
+				"account1": {{
+					Domain:    "app.example.com",
+					AccountID: "account1",
+					Auth: service.AuthConfig{
+						BearerAuth: &service.BearerAuthConfig{
+							Enabled:            true,
+							DistributionGroups: []string{"group1"},
+						},
+					},
+				}},
+			},
+			users: map[string]*types.User{
+				"user1": {Id: "user1", AccountID: "account1", AutoGroups: []string{"group1"}, Blocked: true},
+			},
+			expectErr:    true,
+			expectErrMsg: "user blocked",
+		},
+		{
+			name:   "blocked user denied on a service with no auth configured",
+			domain: "app.example.com",
+			userID: "user1",
+			proxiesByAccount: map[string][]*service.Service{
+				"account1": {{Domain: "app.example.com", AccountID: "account1", Auth: service.AuthConfig{}}},
+			},
+			users: map[string]*types.User{
+				"user1": {Id: "user1", AccountID: "account1", Blocked: true},
+			},
+			expectErr:    true,
+			expectErrMsg: "user blocked",
+		},
 		{
 			name:             "proxy manager error",
 			domain:           "app.example.com",
@@ -421,17 +481,18 @@ func TestValidateTunnelPeerUserEmailEnrichment(t *testing.T) {
 	storedUserNoEmail := map[string]*types.User{userID: {Id: userID, AccountID: accountID, Email: ""}}
 
 	tests := []struct {
-		name         string
-		peerUserID   string
-		storedUsers  map[string]*types.User
-		storedErr    error
-		noIdP        bool
-		idpEmail     string
-		idpHasData   bool
-		idpErr       error
-		expectEmail  string
-		expectUserID string
-		expectIdPHit bool
+		name               string
+		peerUserID         string
+		storedUsers        map[string]*types.User
+		storedErr          error
+		noIdP              bool
+		idpEmail           string
+		idpHasData         bool
+		idpErr             error
+		expectEmail        string
+		expectUserID       string
+		expectIdPHit       bool
+		expectDeniedReason string
 	}{
 		{
 			name:         "idp email wins over stored email",
@@ -490,14 +551,17 @@ func TestValidateTunnelPeerUserEmailEnrichment(t *testing.T) {
 			expectIdPHit: true,
 		},
 		{
-			name:         "idp email when stored user missing keeps peer.UserID as principal",
-			peerUserID:   userID,
-			storedUsers:  map[string]*types.User{},
-			idpEmail:     "idp@example.com",
-			idpHasData:   true,
-			expectEmail:  "idp@example.com",
-			expectUserID: userID,
-			expectIdPHit: true,
+			// The identity still resolves from the IdP, but an owner the store
+			// cannot resolve denies the fast-path rather than granting it.
+			name:               "idp email when stored user missing keeps peer.UserID as principal",
+			peerUserID:         userID,
+			storedUsers:        map[string]*types.User{},
+			idpEmail:           "idp@example.com",
+			idpHasData:         true,
+			expectEmail:        "idp@example.com",
+			expectUserID:       userID,
+			expectIdPHit:       true,
+			expectDeniedReason: deniedReasonUserNotFound,
 		},
 		{
 			name:         "unlinked peer uses peer name and never consults idp",
@@ -545,9 +609,13 @@ func TestValidateTunnelPeerUserEmailEnrichment(t *testing.T) {
 
 			require.NoError(t, err)
 			require.NotNil(t, resp)
-			assert.True(t, resp.GetValid(), "expected access granted")
+			assert.Equal(t, tt.expectDeniedReason == "", resp.GetValid(), "unexpected access decision")
+			assert.Equal(t, tt.expectDeniedReason, resp.GetDeniedReason(), "unexpected denied reason")
 			assert.Equal(t, tt.expectEmail, resp.GetUserEmail())
 			assert.Equal(t, tt.expectUserID, resp.GetUserId())
+			if tt.expectDeniedReason != "" {
+				assert.Empty(t, resp.GetSessionToken(), "a denied peer must not receive a session token")
+			}
 
 			if idpMock != nil {
 				if tt.expectIdPHit {
@@ -562,6 +630,121 @@ func TestValidateTunnelPeerUserEmailEnrichment(t *testing.T) {
 	}
 }
 
+// TestDeniedReasonValues pins the wire values of the account status denied
+// reasons. The proxy logs them and operators filter access logs on them, so a
+// rename is a breaking change rather than an internal detail.
+// TestSameAccount pins the fail-closed behaviour of the account binding: an
+// unset account on either side must never compare equal into a grant.
+func TestSameAccount(t *testing.T) {
+	assert.True(t, sameAccount("account1", "account1"), "matching accounts should bind")
+	assert.False(t, sameAccount("account1", "account2"), "different accounts must not bind")
+	assert.False(t, sameAccount("", ""), "two unset accounts must not bind")
+	assert.False(t, sameAccount("account1", ""), "an unset service account must not bind")
+	assert.False(t, sameAccount("", "account1"), "an unset user account must not bind")
+}
+
+func TestDeniedReasonValues(t *testing.T) {
+	assert.Equal(t, "pending_approval", deniedReasonPendingApproval, "pending approval denied reason wire value")
+	assert.Equal(t, "user_blocked", deniedReasonUserBlocked, "blocked user denied reason wire value")
+	assert.Equal(t, "user_not_found", deniedReasonUserNotFound, "unresolved user denied reason wire value")
+}
+
+// TestValidateTunnelPeerOwnerStatus verifies that the mesh fast-path gates on
+// the account status of the peer's owning user. A peer whose owner was blocked
+// after the peer registered must lose access, while an unlinked machine peer
+// keeps it.
+func TestValidateTunnelPeerOwnerStatus(t *testing.T) {
+	const (
+		domain    = "app.example.com"
+		accountID = "account1"
+		peerID    = "peer1"
+		peerName  = "peer-display-name"
+		userID    = "user1"
+	)
+
+	tests := []struct {
+		name               string
+		peerUserID         string
+		owner              *types.User
+		expectDeniedReason string
+		expectEmail        string
+	}{
+		{
+			name:       "active owner allowed",
+			peerUserID: userID,
+			owner:      &types.User{Id: userID, AccountID: accountID, Email: "user@example.com"},
+		},
+		{
+			name:               "owner pending approval denied",
+			peerUserID:         userID,
+			owner:              &types.User{Id: userID, AccountID: accountID, Email: "user@example.com", Blocked: true, PendingApproval: true},
+			expectDeniedReason: deniedReasonPendingApproval,
+		},
+		{
+			name:               "owner blocked after registering the peer denied",
+			peerUserID:         userID,
+			owner:              &types.User{Id: userID, AccountID: accountID, Email: "user@example.com", Blocked: true},
+			expectDeniedReason: deniedReasonUserBlocked,
+		},
+		{
+			name:       "unlinked machine peer stays allowed",
+			peerUserID: "",
+			owner:      &types.User{Id: userID, AccountID: accountID, Blocked: true},
+		},
+		{
+			// The user lookup is not account-scoped, so a peer row pointing at
+			// another account's user must not resolve into an owner: the peer is
+			// denied and the foreign email never reaches the response.
+			name:               "owner in another account denied and not disclosed",
+			peerUserID:         userID,
+			owner:              &types.User{Id: userID, AccountID: "otherAccount", Email: "foreign@example.com"},
+			expectDeniedReason: deniedReasonUserNotFound,
+			expectEmail:        peerName,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			svc := &service.Service{Domain: domain, AccountID: accountID}
+			usersManager := &mockUsersManager{users: map[string]*types.User{userID: tt.owner}}
+			server := &ProxyServiceServer{
+				serviceManager: &mockReverseProxyManager{
+					proxiesByAccount: map[string][]*service.Service{accountID: {svc}},
+				},
+				peersManager: &mockTunnelPeersManager{
+					peer: &peer.Peer{ID: peerID, Name: peerName, UserID: tt.peerUserID},
+				},
+				usersManager: usersManager,
+			}
+
+			resp, err := server.ValidateTunnelPeer(context.Background(), &proto.ValidateTunnelPeerRequest{
+				Domain:   domain,
+				TunnelIp: "100.64.0.1",
+			})
+
+			require.NoError(t, err)
+			require.NotNil(t, resp)
+			assert.Equal(t, tt.expectDeniedReason, resp.GetDeniedReason(), "unexpected denied reason")
+			assert.Equal(t, tt.expectDeniedReason == "", resp.GetValid(), "unexpected access decision")
+			if tt.expectDeniedReason != "" {
+				assert.Empty(t, resp.GetSessionToken(), "a denied peer must not receive a session token")
+			}
+
+			if tt.expectEmail != "" {
+				assert.Equal(t, tt.expectEmail, resp.GetUserEmail(), "unexpected identity on the response")
+			}
+
+			// The status gate and the identity resolution share one lookup;
+			// an unlinked peer has no owner to look up at all.
+			wantLookups := 1
+			if tt.peerUserID == "" {
+				wantLookups = 0
+			}
+			assert.Equal(t, wantLookups, usersManager.getUserCalls, "owner must be resolved exactly once per request")
+		})
+	}
+}
+
 func TestGetAccountProxyByDomain(t *testing.T) {
 	tests := []struct {
 		name             string

management/internals/shared/grpc/validate_session_test.go

@@ -46,6 +46,7 @@ func setupValidateSessionTest(t *testing.T) *validateSessionTestSetup {
 	proxyService.SetServiceManager(serviceManager)
 
 	createTestProxies(t, ctx, testStore)
+	createStatusTestUsers(t, ctx, testStore)
 
 	return &validateSessionTestSetup{
 		proxyService: proxyService,
@@ -91,6 +92,82 @@ func createTestProxies(t *testing.T, ctx context.Context, testStore store.Store)
 		},
 	}
 	require.NoError(t, testStore.CreateService(ctx, restrictedProxy))
+
+	// Distributed to the account's "All" group, the configuration that hands a
+	// service to every user in the account.
+	allUsersProxy := &service.Service{
+		ID:                "allUsersProxyId",
+		AccountID:         "testAccountId",
+		Name:              "All Users Proxy",
+		Domain:            "all-users-proxy.example.com",
+		Enabled:           true,
+		SessionPrivateKey: privKey,
+		SessionPublicKey:  pubKey,
+		Auth: service.AuthConfig{
+			BearerAuth: &service.BearerAuthConfig{
+				Enabled:            true,
+				DistributionGroups: []string{allUsersGroupID},
+			},
+		},
+	}
+	require.NoError(t, testStore.CreateService(ctx, allUsersProxy))
+}
+
+const (
+	allUsersGroupID   = "allUsersGroupId"
+	pendingUserID     = "pendingUserId"
+	blockedUserID     = "blockedUserId"
+	pendingAllUsersID = "pendingAllUsersUserId"
+)
+
+// createStatusTestUsers adds the users whose account status must keep them out
+// of a proxy session. A user awaiting approval is persisted as both blocked and
+// pending approval, the way the approval flow stores one.
+func createStatusTestUsers(t *testing.T, ctx context.Context, testStore store.Store) {
+	t.Helper()
+
+	require.NoError(t, testStore.CreateGroup(ctx, &types.Group{
+		ID:        allUsersGroupID,
+		AccountID: "testAccountId",
+		Name:      "All",
+		Issued:    types.GroupIssuedAPI,
+	}))
+
+	users := []*types.User{
+		{
+			Id:              pendingUserID,
+			AccountID:       "testAccountId",
+			Role:            types.UserRoleUser,
+			AutoGroups:      []string{"allowedGroupId"},
+			Blocked:         true,
+			PendingApproval: true,
+			Issued:          "api",
+			CreatedAt:       time.Now(),
+		},
+		{
+			Id:              pendingAllUsersID,
+			AccountID:       "testAccountId",
+			Role:            types.UserRoleUser,
+			AutoGroups:      []string{allUsersGroupID},
+			Blocked:         true,
+			PendingApproval: true,
+			Issued:          "api",
+			CreatedAt:       time.Now(),
+		},
+		{
+			Id:              blockedUserID,
+			AccountID:       "testAccountId",
+			Role:            types.UserRoleUser,
+			AutoGroups:      []string{"allowedGroupId"},
+			Blocked:         true,
+			PendingApproval: false,
+			Issued:          "api",
+			CreatedAt:       time.Now(),
+		},
+	}
+	for _, user := range users {
+		require.NoError(t, testStore.SaveUser(ctx, user))
+	}
 }
 
 func generateSessionKeyPair(t *testing.T) (string, string) {
@@ -149,6 +226,114 @@ func TestValidateSession_UserNotInAllowedGroup(t *testing.T) {
 	assert.Empty(t, resp.GetPeerGroupIds(), "PeerGroupIds must mirror the resolved user's actual (empty) memberships on denial")
 }
 
+// TestValidateSession_PendingApprovalUserDenied covers a user who is a member of
+// the service's distribution group but is still waiting for an administrator to
+// approve the account. Group membership alone must not open the service.
+func TestValidateSession_PendingApprovalUserDenied(t *testing.T) {
+	setup := setupValidateSessionTest(t)
+	defer setup.cleanup()
+
+	proxy, err := setup.store.GetServiceByID(context.Background(), store.LockingStrengthNone, "testAccountId", "restrictedProxyId")
+	require.NoError(t, err)
+
+	token := createSessionToken(t, proxy.SessionPrivateKey, pendingUserID, "restricted-proxy.example.com")
+
+	resp, err := setup.proxyService.ValidateSession(context.Background(), &proto.ValidateSessionRequest{
+		Domain:       "restricted-proxy.example.com",
+		SessionToken: token,
+	})
+
+	require.NoError(t, err)
+	assert.False(t, resp.Valid, "User pending approval should be denied")
+	assert.Equal(t, deniedReasonPendingApproval, resp.DeniedReason, "Denied reason should name the pending approval state")
+	assert.Equal(t, pendingUserID, resp.UserId, "Denial should identify the user it applies to")
+	assert.Equal(t, []string{"allowedGroupId"}, resp.GetPeerGroupIds(), "PeerGroupIds must mirror the resolved user's group memberships on denial")
+	assert.Equal(t, []string{"Allowed Group"}, resp.GetPeerGroupNames(), "PeerGroupNames must pair with PeerGroupIds on denial")
+}
+
+// TestValidateSession_PendingApprovalUserInAllUsersGroupDenied covers the same
+// user against a service distributed to the account's "All" group, where every
+// user of the account is a member by default.
+func TestValidateSession_PendingApprovalUserInAllUsersGroupDenied(t *testing.T) {
+	setup := setupValidateSessionTest(t)
+	defer setup.cleanup()
+
+	proxy, err := setup.store.GetServiceByID(context.Background(), store.LockingStrengthNone, "testAccountId", "allUsersProxyId")
+	require.NoError(t, err)
+
+	token := createSessionToken(t, proxy.SessionPrivateKey, pendingAllUsersID, "all-users-proxy.example.com")
+
+	resp, err := setup.proxyService.ValidateSession(context.Background(), &proto.ValidateSessionRequest{
+		Domain:       "all-users-proxy.example.com",
+		SessionToken: token,
+	})
+
+	require.NoError(t, err)
+	assert.False(t, resp.Valid, "User pending approval should be denied even in the All Users group")
+	assert.Equal(t, deniedReasonPendingApproval, resp.DeniedReason, "Denied reason should name the pending approval state")
+	assert.Equal(t, pendingAllUsersID, resp.UserId, "Denial should identify the user it applies to")
+	assert.Equal(t, []string{allUsersGroupID}, resp.GetPeerGroupIds(), "PeerGroupIds must mirror the resolved user's group memberships on denial")
+}
+
+// TestValidateSession_BlockedUserDenied covers a user blocked after having been
+// approved, so PendingApproval is false and only the blocked flag is set.
+func TestValidateSession_BlockedUserDenied(t *testing.T) {
+	setup := setupValidateSessionTest(t)
+	defer setup.cleanup()
+
+	proxy, err := setup.store.GetServiceByID(context.Background(), store.LockingStrengthNone, "testAccountId", "restrictedProxyId")
+	require.NoError(t, err)
+
+	token := createSessionToken(t, proxy.SessionPrivateKey, blockedUserID, "restricted-proxy.example.com")
+
+	resp, err := setup.proxyService.ValidateSession(context.Background(), &proto.ValidateSessionRequest{
+		Domain:       "restricted-proxy.example.com",
+		SessionToken: token,
+	})
+
+	require.NoError(t, err)
+	assert.False(t, resp.Valid, "Blocked user should be denied")
+	assert.Equal(t, deniedReasonUserBlocked, resp.DeniedReason, "Denied reason should name the blocked state")
+	assert.Equal(t, blockedUserID, resp.UserId, "Denial should identify the user it applies to")
+}
+
+// TestValidateSession_UserAllowedAfterApproval walks the same session token
+// through the approval transition: denied while pending, allowed once an
+// administrator clears both flags.
+func TestValidateSession_UserAllowedAfterApproval(t *testing.T) {
+	setup := setupValidateSessionTest(t)
+	defer setup.cleanup()
+
+	ctx := context.Background()
+
+	proxy, err := setup.store.GetServiceByID(ctx, store.LockingStrengthNone, "testAccountId", "restrictedProxyId")
+	require.NoError(t, err)
+
+	token := createSessionToken(t, proxy.SessionPrivateKey, pendingUserID, "restricted-proxy.example.com")
+	req := &proto.ValidateSessionRequest{
+		Domain:       "restricted-proxy.example.com",
+		SessionToken: token,
+	}
+
+	resp, err := setup.proxyService.ValidateSession(ctx, req)
+	require.NoError(t, err)
+	require.False(t, resp.Valid, "User pending approval should be denied before approval")
+	assert.Equal(t, deniedReasonPendingApproval, resp.DeniedReason, "Denied reason should name the pending approval state")
+
+	user, err := setup.store.GetUserByUserID(ctx, store.LockingStrengthNone, pendingUserID)
+	require.NoError(t, err)
+	user.PendingApproval = false
+	user.Blocked = false
+	require.NoError(t, setup.store.SaveUser(ctx, user))
+
+	resp, err = setup.proxyService.ValidateSession(ctx, req)
+	require.NoError(t, err)
+	assert.True(t, resp.Valid, "Approved user should be allowed access")
+	assert.Empty(t, resp.DeniedReason)
+	assert.Equal(t, pendingUserID, resp.UserId, "Approved user should be identified in the response")
+	assert.Equal(t, []string{"allowedGroupId"}, resp.GetPeerGroupIds(), "PeerGroupIds must mirror the approved user's group memberships")
+}
+
 func TestValidateSession_UserInDifferentAccount(t *testing.T) {
 	setup := setupValidateSessionTest(t)
 	defer setup.cleanup()

management/server/http/handlers/proxy/auth.go

@@ -2,6 +2,7 @@ package proxy
 
 import (
 	"context"
+	"errors"
 	"net"
 	"net/http"
 	"net/netip"
@@ -108,7 +109,7 @@ func (h *AuthCallbackHandler) handleCallback(w http.ResponseWriter, r *http.Requ
 		redirectURL.Scheme = "https"
 		query := redirectURL.Query()
 		query.Set("error", "access_denied")
-		query.Set("error_description", "Service configuration error")
+		query.Set("error_description", sessionTokenErrorDescription(err))
 		redirectURL.RawQuery = query.Encode()
 		http.Redirect(w, r, redirectURL.String(), http.StatusFound)
 		return
@@ -124,6 +125,20 @@ func (h *AuthCallbackHandler) handleCallback(w http.ResponseWriter, r *http.Requ
 	http.Redirect(w, r, redirectURL.String(), http.StatusFound)
 }
 
+// sessionTokenErrorDescription maps a session token failure to the text the
+// proxy renders on its access denied page. Account status denials get a message
+// the user can act on, while everything else stays generic so a lookup or
+// signing failure does not describe management internals to the browser.
+func sessionTokenErrorDescription(err error) string {
+	if errors.Is(err, nbgrpc.ErrUserPendingApproval) {
+		return "Your account is pending approval by an administrator"
+	}
+	if errors.Is(err, nbgrpc.ErrUserBlocked) {
+		return "Your account is blocked"
+	}
+	return "Service configuration error"
+}
+
 func extractUserIDFromToken(ctx context.Context, provider *oidc.Provider, config nbgrpc.ProxyOIDCConfig, token *oauth2.Token) string {
 	rawIDToken, ok := token.Extra("id_token").(string)
 	if !ok {

management/server/http/handlers/proxy/auth_callback_integration_test.go

@@ -360,6 +360,51 @@ func createTestAccountsAndUsers(t *testing.T, ctx context.Context, testStore sto
 		Issued:     "api",
 	}
 	require.NoError(t, testStore.SaveUser(ctx, allowedUser))
+
+	// A second tenant, whose users must never be issued a token signed with
+	// the first tenant's service session key.
+	otherAccount := &types.Account{
+		Id:                     "otherAccountId",
+		Domain:                 "other.com",
+		DomainCategory:         "private",
+		IsDomainPrimaryAccount: true,
+		CreatedAt:              time.Now(),
+	}
+	require.NoError(t, testStore.SaveAccount(ctx, otherAccount))
+
+	otherAccountUser := &types.User{
+		Id:        "otherAccountUserId",
+		AccountID: "otherAccountId",
+		Role:      types.UserRoleUser,
+		CreatedAt: time.Now(),
+		Issued:    "api",
+	}
+	require.NoError(t, testStore.SaveUser(ctx, otherAccountUser))
+
+	// A user awaiting approval is stored as blocked and pending approval, and
+	// carries the same group membership as the approved one.
+	pendingUser := &types.User{
+		Id:              "pendingUserId",
+		AccountID:       "testAccountId",
+		Role:            types.UserRoleUser,
+		AutoGroups:      []string{"allowedGroupId"},
+		Blocked:         true,
+		PendingApproval: true,
+		CreatedAt:       time.Now(),
+		Issued:          "api",
+	}
+	require.NoError(t, testStore.SaveUser(ctx, pendingUser))
+
+	blockedUser := &types.User{
+		Id:         "blockedUserId",
+		AccountID:  "testAccountId",
+		Role:       types.UserRoleUser,
+		AutoGroups: []string{"allowedGroupId"},
+		Blocked:    true,
+		CreatedAt:  time.Now(),
+		Issued:     "api",
+	}
+	require.NoError(t, testStore.SaveUser(ctx, blockedUser))
 }
 
 // testServiceManager is a minimal implementation for testing.
@@ -490,6 +535,64 @@ func TestAuthCallback_UserAllowedToLogin(t *testing.T) {
 	require.Empty(t, parsedLocation.Query().Get("error"), "Should not have error parameter")
 }
 
+// TestAuthCallback_UserDeniedByAccountStatus asserts that a user whose account
+// is pending approval or blocked never receives a session token from the OIDC
+// callback, and that the redirect carries a description the proxy can render.
+func TestAuthCallback_UserDeniedByAccountStatus(t *testing.T) {
+	tests := []struct {
+		name            string
+		subject         string
+		expectErrorDesc string
+	}{
+		{
+			name:            "pending approval",
+			subject:         "pendingUserId",
+			expectErrorDesc: "Your account is pending approval by an administrator",
+		},
+		{
+			name:            "blocked",
+			subject:         "blockedUserId",
+			expectErrorDesc: "Your account is blocked",
+		},
+		{
+			name:            "unknown to management",
+			subject:         "userMissingFromStoreId",
+			expectErrorDesc: "Service configuration error",
+		},
+		{
+			// The account topology stays out of the browser-visible message.
+			name:            "belongs to another account",
+			subject:         "otherAccountUserId",
+			expectErrorDesc: "Service configuration error",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			setup := setupAuthCallbackTest(t)
+			defer setup.cleanup()
+
+			setup.oidcServer.tokenSubject = tt.subject
+
+			state := createTestState(t, setup.proxyService, "https://test-proxy.example.com/dashboard")
+
+			req := httptest.NewRequest(http.MethodGet, "/reverse-proxy/callback?code=test-auth-code&state="+url.QueryEscape(state), nil)
+			rec := httptest.NewRecorder()
+
+			setup.router.ServeHTTP(rec, req)
+
+			require.Equal(t, http.StatusFound, rec.Code)
+
+			parsedLocation, err := url.Parse(rec.Header().Get("Location"))
+			require.NoError(t, err)
+
+			require.Empty(t, parsedLocation.Query().Get("session_token"), "Denied user must not receive a session token")
+			require.Equal(t, "access_denied", parsedLocation.Query().Get("error"))
+			require.Equal(t, tt.expectErrorDesc, parsedLocation.Query().Get("error_description"))
+		})
+	}
+}
+
 func TestAuthCallback_ProxyNotFound(t *testing.T) {
 	setup := setupAuthCallbackTest(t)
 	defer setup.cleanup()