Windows: Fix crash due to unterminated string (#58) (1.0.2)

This fixes a crash when fetching a process arguments. The command-line
string read from the target process memory sometimes is not terminated.
It can cause bogus characters appended to the command-line or a crash.

CHANGELOG.md

@@ -16,10 +16,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-- Fixed a leak when calling the CommandLineToArgv function. [#51](https://github.com/elastic/go-sysinfo/pull/51)
-
 ### Security
 
+## [1.0.2] - 2019-07-09
+
+### Fixed
+
+- Fixed a leak when calling the CommandLineToArgv function. [#51](https://github.com/elastic/go-sysinfo/pull/51)
+- Fixed a crash when calling the CommandLineToArgv function. [#58](https://github.com/elastic/go-sysinfo/pull/58)
+
 ## [1.0.1] - 2019-05-08
 
 ### Fixed

providers/windows/process_windows.go

@@ -207,8 +207,14 @@ func getUserProcessParams(handle syscall.Handle, pbi windows.ProcessBasicInforma
 // read an UTF-16 string from another process memory. Result is an []byte
 // with the UTF-16 data.
 func readProcessUnicodeString(handle syscall.Handle, s *windows.UnicodeString) ([]byte, error) {
-	buf := make([]byte, s.Size)
-	nRead, err := windows.ReadProcessMemory(handle, s.Buffer, buf)
+	// Allocate an extra UTF-16 null character at the end in case the read string
+	// is not terminated.
+	extra := 2
+	if s.Size&1 != 0 {
+		extra = 3 // If size is odd, need 3 nulls to terminate.
+	}
+	buf := make([]byte, int(s.Size)+extra)
+	nRead, err := windows.ReadProcessMemory(handle, s.Buffer, buf[:s.Size])
 	if err != nil {
 		return nil, err
 	}
@@ -221,9 +227,23 @@ func readProcessUnicodeString(handle syscall.Handle, s *windows.UnicodeString) (
 // Use Windows' CommandLineToArgv API to split an UTF-16 command line string
 // into a list of parameters.
 func splitCommandline(utf16 []byte) ([]string, error) {
-	if len(utf16) == 0 {
+	n := len(utf16)
+	// Discard odd byte
+	if n&1 != 0 {
+		n--
+		utf16 = utf16[:n]
+	}
+	if n == 0 {
 		return nil, nil
 	}
+	terminated := false
+	for i := 0; i < n && !terminated; i += 2 {
+		terminated = utf16[i] == 0 && utf16[i+1] == 0
+	}
+	if !terminated {
+		// Append a null uint16 at the end if terminator is missing
+		utf16 = append(utf16, 0, 0)
+	}
 	var numArgs int32
 	argsWide, err := syscall.CommandLineToArgv((*uint16)(unsafe.Pointer(&utf16[0])), &numArgs)
 	if err != nil {