src

dll_windows.go (10522B)

---

 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package windows
 
 import (
 	"sync"
 	"sync/atomic"
 	"syscall"
 	"unsafe"
 )
 
 // We need to use LoadLibrary and GetProcAddress from the Go runtime, because
 // the these symbols are loaded by the system linker and are required to
 // dynamically load additional symbols. Note that in the Go runtime, these
 // return syscall.Handle and syscall.Errno, but these are the same, in fact,
 // as windows.Handle and windows.Errno, and we intend to keep these the same.
 
 //go:linkname syscall_loadlibrary syscall.loadlibrary
 func syscall_loadlibrary(filename *uint16) (handle Handle, err Errno)
 
 //go:linkname syscall_getprocaddress syscall.getprocaddress
 func syscall_getprocaddress(handle Handle, procname *uint8) (proc uintptr, err Errno)
 
 // DLLError describes reasons for DLL load failures.
 type DLLError struct {
 	Err     error
 	ObjName string
 	Msg     string
 }
 
 func (e *DLLError) Error() string { return e.Msg }
 
 func (e *DLLError) Unwrap() error { return e.Err }
 
 // A DLL implements access to a single DLL.
 type DLL struct {
 	Name   string
 	Handle Handle
 }
 
 // LoadDLL loads DLL file into memory.
 //
 // Warning: using LoadDLL without an absolute path name is subject to
 // DLL preloading attacks. To safely load a system DLL, use [NewLazySystemDLL],
 // or use [LoadLibraryEx] directly.
 func LoadDLL(name string) (dll *DLL, err error) {
 	namep, err := UTF16PtrFromString(name)
 	if err != nil {
 		return nil, err
 	}
 	h, e := syscall_loadlibrary(namep)
 	if e != 0 {
 		return nil, &DLLError{
 			Err:     e,
 			ObjName: name,
 			Msg:     "Failed to load " + name + ": " + e.Error(),
 		}
 	}
 	d := &DLL{
 		Name:   name,
 		Handle: h,
 	}
 	return d, nil
 }
 
 // MustLoadDLL is like LoadDLL but panics if load operation fails.
 func MustLoadDLL(name string) *DLL {
 	d, e := LoadDLL(name)
 	if e != nil {
 		panic(e)
 	}
 	return d
 }
 
 // FindProc searches DLL d for procedure named name and returns *Proc
 // if found. It returns an error if search fails.
 func (d *DLL) FindProc(name string) (proc *Proc, err error) {
 	namep, err := BytePtrFromString(name)
 	if err != nil {
 		return nil, err
 	}
 	a, e := syscall_getprocaddress(d.Handle, namep)
 	if e != 0 {
 		return nil, &DLLError{
 			Err:     e,
 			ObjName: name,
 			Msg:     "Failed to find " + name + " procedure in " + d.Name + ": " + e.Error(),
 		}
 	}
 	p := &Proc{
 		Dll:  d,
 		Name: name,
 		addr: a,
 	}
 	return p, nil
 }
 
 // MustFindProc is like FindProc but panics if search fails.
 func (d *DLL) MustFindProc(name string) *Proc {
 	p, e := d.FindProc(name)
 	if e != nil {
 		panic(e)
 	}
 	return p
 }
 
 // FindProcByOrdinal searches DLL d for procedure by ordinal and returns *Proc
 // if found. It returns an error if search fails.
 func (d *DLL) FindProcByOrdinal(ordinal uintptr) (proc *Proc, err error) {
 	a, e := GetProcAddressByOrdinal(d.Handle, ordinal)
 	name := "#" + itoa(int(ordinal))
 	if e != nil {
 		return nil, &DLLError{
 			Err:     e,
 			ObjName: name,
 			Msg:     "Failed to find " + name + " procedure in " + d.Name + ": " + e.Error(),
 		}
 	}
 	p := &Proc{
 		Dll:  d,
 		Name: name,
 		addr: a,
 	}
 	return p, nil
 }
 
 // MustFindProcByOrdinal is like FindProcByOrdinal but panics if search fails.
 func (d *DLL) MustFindProcByOrdinal(ordinal uintptr) *Proc {
 	p, e := d.FindProcByOrdinal(ordinal)
 	if e != nil {
 		panic(e)
 	}
 	return p
 }
 
 // Release unloads DLL d from memory.
 func (d *DLL) Release() (err error) {
 	return FreeLibrary(d.Handle)
 }
 
 // A Proc implements access to a procedure inside a DLL.
 type Proc struct {
 	Dll  *DLL
 	Name string
 	addr uintptr
 }
 
 // Addr returns the address of the procedure represented by p.
 // The return value can be passed to Syscall to run the procedure.
 func (p *Proc) Addr() uintptr {
 	return p.addr
 }
 
 //go:uintptrescapes
 
 // Call executes procedure p with arguments a. It will panic, if more than 15 arguments
 // are supplied.
 //
 // The returned error is always non-nil, constructed from the result of GetLastError.
 // Callers must inspect the primary return value to decide whether an error occurred
 // (according to the semantics of the specific function being called) before consulting
 // the error. The error will be guaranteed to contain windows.Errno.
 func (p *Proc) Call(a ...uintptr) (r1, r2 uintptr, lastErr error) {
 	return syscall.SyscallN(p.Addr(), a...)
 }
 
 // A LazyDLL implements access to a single DLL.
 // It will delay the load of the DLL until the first
 // call to its Handle method or to one of its
 // LazyProc's Addr method.
 type LazyDLL struct {
 	Name string
 
 	// System determines whether the DLL must be loaded from the
 	// Windows System directory, bypassing the normal DLL search
 	// path.
 	System bool
 
 	mu  sync.Mutex
 	dll *DLL // non nil once DLL is loaded
 }
 
 // Load loads DLL file d.Name into memory. It returns an error if fails.
 // Load will not try to load DLL, if it is already loaded into memory.
 func (d *LazyDLL) Load() error {
 	// Non-racy version of:
 	// if d.dll != nil {
 	if atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&d.dll))) != nil {
 		return nil
 	}
 	d.mu.Lock()
 	defer d.mu.Unlock()
 	if d.dll != nil {
 		return nil
 	}
 
 	// kernel32.dll is special, since it's where LoadLibraryEx comes from.
 	// The kernel already special-cases its name, so it's always
 	// loaded from system32.
 	var dll *DLL
 	var err error
 	if d.Name == "kernel32.dll" {
 		dll, err = LoadDLL(d.Name)
 	} else {
 		dll, err = loadLibraryEx(d.Name, d.System)
 	}
 	if err != nil {
 		return err
 	}
 
 	// Non-racy version of:
 	// d.dll = dll
 	atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&d.dll)), unsafe.Pointer(dll))
 	return nil
 }
 
 // mustLoad is like Load but panics if search fails.
 func (d *LazyDLL) mustLoad() {
 	e := d.Load()
 	if e != nil {
 		panic(e)
 	}
 }
 
 // Handle returns d's module handle.
 func (d *LazyDLL) Handle() uintptr {
 	d.mustLoad()
 	return uintptr(d.dll.Handle)
 }
 
 // NewProc returns a LazyProc for accessing the named procedure in the DLL d.
 func (d *LazyDLL) NewProc(name string) *LazyProc {
 	return &LazyProc{l: d, Name: name}
 }
 
 // NewLazyDLL creates new LazyDLL associated with DLL file.
 //
 // Warning: using NewLazyDLL without an absolute path name is subject to
 // DLL preloading attacks. To safely load a system DLL, use [NewLazySystemDLL].
 func NewLazyDLL(name string) *LazyDLL {
 	return &LazyDLL{Name: name}
 }
 
 // NewLazySystemDLL is like NewLazyDLL, but will only
 // search Windows System directory for the DLL if name is
 // a base name (like "advapi32.dll").
 func NewLazySystemDLL(name string) *LazyDLL {
 	return &LazyDLL{Name: name, System: true}
 }
 
 // A LazyProc implements access to a procedure inside a LazyDLL.
 // It delays the lookup until the Addr method is called.
 type LazyProc struct {
 	Name string
 
 	mu   sync.Mutex
 	l    *LazyDLL
 	proc *Proc
 }
 
 // Find searches DLL for procedure named p.Name. It returns
 // an error if search fails. Find will not search procedure,
 // if it is already found and loaded into memory.
 func (p *LazyProc) Find() error {
 	// Non-racy version of:
 	// if p.proc == nil {
 	if atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&p.proc))) == nil {
 		p.mu.Lock()
 		defer p.mu.Unlock()
 		if p.proc == nil {
 			e := p.l.Load()
 			if e != nil {
 				return e
 			}
 			proc, e := p.l.dll.FindProc(p.Name)
 			if e != nil {
 				return e
 			}
 			// Non-racy version of:
 			// p.proc = proc
 			atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&p.proc)), unsafe.Pointer(proc))
 		}
 	}
 	return nil
 }
 
 // mustFind is like Find but panics if search fails.
 func (p *LazyProc) mustFind() {
 	e := p.Find()
 	if e != nil {
 		panic(e)
 	}
 }
 
 // Addr returns the address of the procedure represented by p.
 // The return value can be passed to Syscall to run the procedure.
 // It will panic if the procedure cannot be found.
 func (p *LazyProc) Addr() uintptr {
 	p.mustFind()
 	return p.proc.Addr()
 }
 
 //go:uintptrescapes
 
 // Call executes procedure p with arguments a. It will panic, if more than 15 arguments
 // are supplied. It will also panic if the procedure cannot be found.
 //
 // The returned error is always non-nil, constructed from the result of GetLastError.
 // Callers must inspect the primary return value to decide whether an error occurred
 // (according to the semantics of the specific function being called) before consulting
 // the error. The error will be guaranteed to contain windows.Errno.
 func (p *LazyProc) Call(a ...uintptr) (r1, r2 uintptr, lastErr error) {
 	p.mustFind()
 	return p.proc.Call(a...)
 }
 
 var canDoSearchSystem32Once struct {
 	sync.Once
 	v bool
 }
 
 func initCanDoSearchSystem32() {
 	// https://msdn.microsoft.com/en-us/library/ms684179(v=vs.85).aspx says:
 	// "Windows 7, Windows Server 2008 R2, Windows Vista, and Windows
 	// Server 2008: The LOAD_LIBRARY_SEARCH_* flags are available on
 	// systems that have KB2533623 installed. To determine whether the
 	// flags are available, use GetProcAddress to get the address of the
 	// AddDllDirectory, RemoveDllDirectory, or SetDefaultDllDirectories
 	// function. If GetProcAddress succeeds, the LOAD_LIBRARY_SEARCH_*
 	// flags can be used with LoadLibraryEx."
 	canDoSearchSystem32Once.v = (modkernel32.NewProc("AddDllDirectory").Find() == nil)
 }
 
 func canDoSearchSystem32() bool {
 	canDoSearchSystem32Once.Do(initCanDoSearchSystem32)
 	return canDoSearchSystem32Once.v
 }
 
 func isBaseName(name string) bool {
 	for _, c := range name {
 		if c == ':' || c == '/' || c == '\\' {
 			return false
 		}
 	}
 	return true
 }
 
 // loadLibraryEx wraps the Windows LoadLibraryEx function.
 //
 // See https://msdn.microsoft.com/en-us/library/windows/desktop/ms684179(v=vs.85).aspx
 //
 // If name is not an absolute path, LoadLibraryEx searches for the DLL
 // in a variety of automatic locations unless constrained by flags.
 // See: https://msdn.microsoft.com/en-us/library/ff919712%28VS.85%29.aspx
 func loadLibraryEx(name string, system bool) (*DLL, error) {
 	loadDLL := name
 	var flags uintptr
 	if system {
 		if canDoSearchSystem32() {
 			flags = LOAD_LIBRARY_SEARCH_SYSTEM32
 		} else if isBaseName(name) {
 			// WindowsXP or unpatched Windows machine
 			// trying to load "foo.dll" out of the system
 			// folder, but LoadLibraryEx doesn't support
 			// that yet on their system, so emulate it.
 			systemdir, err := GetSystemDirectory()
 			if err != nil {
 				return nil, err
 			}
 			loadDLL = systemdir + "\\" + name
 		}
 	}
 	h, err := LoadLibraryEx(loadDLL, 0, flags)
 	if err != nil {
 		return nil, err
 	}
 	return &DLL{Name: name, Handle: h}, nil
 }