feat: implement security, discovery, history, file transfer, web UI (P0-P3)

internal/clipboard/clipboard_windows.go

@@ -24,6 +24,7 @@ var (
 	procGlobalLock   = kernel32.NewProc("GlobalLock")
 	procGlobalUnlock = kernel32.NewProc("GlobalUnlock")
 	procGlobalFree   = kernel32.NewProc("GlobalFree")
+	procGlobalSize   = kernel32.NewProc("GlobalSize")
 )
 
 type windowsClipboard struct{}
@@ -52,9 +53,16 @@ func (c *windowsClipboard) Read() (string, error) {
 
 	defer func() { _, _, _ = procGlobalUnlock.Call(h) }()
 
+	// Query the actual size of the global memory block so we never read past it.
+	size, _, _ := procGlobalSize.Call(h)
+	if size == 0 {
+		return "", nil
+	}
+	units := size / 2 // bytes → UTF-16 code units
+
 	// Lock and read the global memory block.
 	// Use a helper to keep the uintptr→unsafe.Pointer conversion close to the syscall.
-	mem := lockAndRead(h)
+	mem := lockAndRead(h, units)
 	if mem == nil {
 		return "", fmt.Errorf("clipboard read: GlobalLock failed")
 	}
@@ -103,9 +111,10 @@ func (c *windowsClipboard) Write(text string) error {
 	return nil
 }
 
-// lockAndRead locks a global memory handle and returns its UTF-16 data.
-// Returns nil on failure. Caller must call GlobalUnlock after use.
-func lockAndRead(h uintptr) []uint16 {
+// lockAndRead locks a global memory handle and returns its UTF-16 data of the
+// given length (in code units). Returns nil on failure. Caller must call
+// GlobalUnlock after use.
+func lockAndRead(h uintptr, units uintptr) []uint16 {
 	p, _, _ := procGlobalLock.Call(h)
 	if p == 0 {
 		return nil
@@ -113,7 +122,7 @@ func lockAndRead(h uintptr) []uint16 {
 	// Use unsafe.Add to derive a pointer from nil; the uintptr came from
 	// GlobalLock (GMEM_FIXED) and is a valid virtual address, not a Go pointer.
 	ptr := unsafe.Add(unsafe.Pointer(nil), p)
-	return unsafe.Slice((*uint16)(ptr), 1<<20)
+	return unsafe.Slice((*uint16)(ptr), units)
 }
 
 // lockAndWrite locks a global memory handle and copies UTF-16 data into it.