Update

vendor/tailscale.com/ipn/ipnauth/ipnauth.go

@@ -14,8 +14,8 @@ import (
 	"runtime"
 	"strconv"
 
-	"github.com/tailscale/peercred"
 	"tailscale.com/envknob"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/ipn"
 	"tailscale.com/safesocket"
 	"tailscale.com/types/logger"
@@ -63,8 +63,8 @@ type ConnIdentity struct {
 	notWindows bool // runtime.GOOS != "windows"
 
 	// Fields used when NotWindows:
-	isUnixSock bool            // Conn is a *net.UnixConn
-	creds      *peercred.Creds // or nil
+	isUnixSock bool      // Conn is a *net.UnixConn
+	creds      PeerCreds // or nil if peercred.Get was not implemented on this OS
 
 	// Used on Windows:
 	// TODO(bradfitz): merge these into the peercreds package and
@@ -78,6 +78,13 @@ type ConnIdentity struct {
 // It's suitable for passing to LookupUserFromID (os/user.LookupId) on any
 // operating system.
 func (ci *ConnIdentity) WindowsUserID() ipn.WindowsUserID {
+	if !buildfeatures.HasDebug && runtime.GOOS != "windows" {
+		// This function is only implemented on non-Windows for simulating
+		// Windows in tests. But that test (per comments below) is broken
+		// anyway. So disable this testing path in non-debug builds
+		// and just do the thing that optimizes away.
+		return ""
+	}
 	if envknob.GOOS() != "windows" {
 		return ""
 	}
@@ -97,9 +104,18 @@ func (ci *ConnIdentity) WindowsUserID() ipn.WindowsUserID {
 	return ""
 }
 
-func (ci *ConnIdentity) Pid() int               { return ci.pid }
-func (ci *ConnIdentity) IsUnixSock() bool       { return ci.isUnixSock }
-func (ci *ConnIdentity) Creds() *peercred.Creds { return ci.creds }
+func (ci *ConnIdentity) Pid() int         { return ci.pid }
+func (ci *ConnIdentity) IsUnixSock() bool { return ci.isUnixSock }
+func (ci *ConnIdentity) Creds() PeerCreds { return ci.creds }
+
+// PeerCreds is the interface for a github.com/tailscale/peercred.Creds,
+// if linked into the binary.
+//
+// (It's not used on some platforms, or if ts_omit_unixsocketidentity is set.)
+type PeerCreds interface {
+	UserID() (uid string, ok bool)
+	PID() (pid int, ok bool)
+}
 
 var metricIssue869Workaround = clientmetric.NewCounter("issue_869_workaround")
 

vendor/tailscale.com/ipn/ipnauth/ipnauth_omit_unixsocketidentity.go

@@ -1,14 +1,13 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build !windows
+//go:build !windows && ts_omit_unixsocketidentity
 
 package ipnauth
 
 import (
 	"net"
 
-	"github.com/tailscale/peercred"
 	"tailscale.com/types/logger"
 )
 
@@ -16,12 +15,7 @@ import (
 // based on the user who owns the other end of the connection.
 // and couldn't. The returned connIdentity has NotWindows set to true.
 func GetConnIdentity(_ logger.Logf, c net.Conn) (ci *ConnIdentity, err error) {
-	ci = &ConnIdentity{conn: c, notWindows: true}
-	_, ci.isUnixSock = c.(*net.UnixConn)
-	if ci.creds, _ = peercred.Get(c); ci.creds != nil {
-		ci.pid, _ = ci.creds.PID()
-	}
-	return ci, nil
+	return &ConnIdentity{conn: c, notWindows: true}, nil
 }
 
 // WindowsToken is unsupported when GOOS != windows and always returns

vendor/tailscale.com/ipn/ipnauth/ipnauth_unix_creds.go

@@ -0,0 +1,37 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !windows && !ts_omit_unixsocketidentity
+
+package ipnauth
+
+import (
+	"net"
+
+	"github.com/tailscale/peercred"
+	"tailscale.com/types/logger"
+)
+
+// GetConnIdentity extracts the identity information from the connection
+// based on the user who owns the other end of the connection.
+// and couldn't. The returned connIdentity has NotWindows set to true.
+func GetConnIdentity(_ logger.Logf, c net.Conn) (ci *ConnIdentity, err error) {
+	ci = &ConnIdentity{conn: c, notWindows: true}
+	_, ci.isUnixSock = c.(*net.UnixConn)
+	if creds, err := peercred.Get(c); err == nil {
+		ci.creds = creds
+		ci.pid, _ = ci.creds.PID()
+	} else if err == peercred.ErrNotImplemented {
+		// peercred.Get is not implemented on this OS (such as OpenBSD)
+		// Just leave creds as nil, as documented.
+	} else {
+		return nil, err
+	}
+	return ci, nil
+}
+
+// WindowsToken is unsupported when GOOS != windows and always returns
+// ErrNotImplemented.
+func (ci *ConnIdentity) WindowsToken() (WindowsToken, error) {
+	return nil, ErrNotImplemented
+}

vendor/tailscale.com/ipn/ipnauth/ipnauth_windows.go

@@ -25,6 +25,12 @@ func GetConnIdentity(logf logger.Logf, c net.Conn) (ci *ConnIdentity, err error)
 	if !ok {
 		return nil, fmt.Errorf("not a WindowsClientConn: %T", c)
 	}
+	if err := wcc.CheckToken(); err != nil {
+		// Failure to obtain a token means the client cannot be authenticated.
+		// We don't care about the exact error, but it typically means the client
+		// attempted to connect at the Anonymous impersonation level.
+		return nil, fmt.Errorf("authentication failed: %w", err)
+	}
 	ci.pid, err = wcc.ClientPID()
 	if err != nil {
 		return nil, err
@@ -169,26 +175,13 @@ func (t *token) IsUID(uid ipn.WindowsUserID) bool {
 // WindowsToken returns the WindowsToken representing the security context
 // of the connection's client.
 func (ci *ConnIdentity) WindowsToken() (WindowsToken, error) {
-	var wcc *safesocket.WindowsClientConn
-	var ok bool
-	if wcc, ok = ci.conn.(*safesocket.WindowsClientConn); !ok {
+	wcc, ok := ci.conn.(*safesocket.WindowsClientConn)
+	if !ok {
 		return nil, fmt.Errorf("not a WindowsClientConn: %T", ci.conn)
 	}
-
-	// We duplicate the token's handle so that the WindowsToken we return may have
-	// a lifetime independent from the original connection.
-	var h windows.Handle
-	if err := windows.DuplicateHandle(
-		windows.CurrentProcess(),
-		windows.Handle(wcc.Token()),
-		windows.CurrentProcess(),
-		&h,
-		0,
-		false,
-		windows.DUPLICATE_SAME_ACCESS,
-	); err != nil {
+	token, err := wcc.Token()
+	if err != nil {
 		return nil, err
 	}
-
-	return newToken(windows.Token(h)), nil
+	return newToken(token), nil
 }

vendor/tailscale.com/ipn/ipnauth/policy.go

@@ -8,9 +8,11 @@ import (
 	"fmt"
 
 	"tailscale.com/client/tailscale/apitype"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/ipn"
 	"tailscale.com/tailcfg"
-	"tailscale.com/util/syspolicy"
+	"tailscale.com/util/syspolicy/pkey"
+	"tailscale.com/util/syspolicy/policyclient"
 )
 
 type actorWithPolicyChecks struct{ Actor }
@@ -50,10 +52,13 @@ func (a actorWithPolicyChecks) CheckProfileAccess(profile ipn.LoginProfileView,
 // TODO(nickkhyl): unexport it when we move [ipn.Actor] implementations from [ipnserver]
 // and corp to this package.
 func CheckDisconnectPolicy(actor Actor, profile ipn.LoginProfileView, reason string, auditFn AuditLogFunc) error {
-	if alwaysOn, _ := syspolicy.GetBoolean(syspolicy.AlwaysOn, false); !alwaysOn {
+	if !buildfeatures.HasSystemPolicy {
 		return nil
 	}
-	if allowWithReason, _ := syspolicy.GetBoolean(syspolicy.AlwaysOnOverrideWithReason, false); !allowWithReason {
+	if alwaysOn, _ := policyclient.Get().GetBoolean(pkey.AlwaysOn, false); !alwaysOn {
+		return nil
+	}
+	if allowWithReason, _ := policyclient.Get().GetBoolean(pkey.AlwaysOnOverrideWithReason, false); !allowWithReason {
 		return errors.New("disconnect not allowed: always-on mode is enabled")
 	}
 	if reason == "" {

vendor/tailscale.com/ipn/ipnauth/self.go

@@ -13,6 +13,11 @@ import (
 // has unlimited access.
 var Self Actor = unrestricted{}
 
+// TODO is a caller identity used when the operation is performed on behalf of a user,
+// rather than by tailscaled itself, but the surrounding function is not yet extended
+// to accept an [Actor] parameter. It grants the same unrestricted access as [Self].
+var TODO Actor = unrestricted{}
+
 // unrestricted is an [Actor] that has unlimited access to the currently running
 // tailscaled instance. It's typically used for operations performed by tailscaled
 // on its own, or upon a request from the control plane, rather on behalf of a user.
@@ -49,3 +54,10 @@ func (unrestricted) IsLocalSystem() bool { return false }
 // Deprecated: this method exists for compatibility with the current (as of 2025-01-28)
 // permission model and will be removed as we progress on tailscale/corp#18342.
 func (unrestricted) IsLocalAdmin(operatorUID string) bool { return false }
+
+// IsTailscaled reports whether the given Actor represents Tailscaled itself,
+// such as [Self] or a [TODO] placeholder actor.
+func IsTailscaled(a Actor) bool {
+	_, ok := a.(unrestricted)
+	return ok
+}