exec_windows.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Fork, exec, wait, etc.
     6  
     7  package windows
     8  
     9  import (
    10  	errorspkg "errors"
    11  	"unsafe"
    12  )
    13  
    14  // EscapeArg rewrites command line argument s as prescribed
    15  // in http://msdn.microsoft.com/en-us/library/ms880421.
    16  // This function returns "" (2 double quotes) if s is empty.
    17  // Alternatively, these transformations are done:
    18  //   - every back slash (\) is doubled, but only if immediately
    19  //     followed by double quote (");
    20  //   - every double quote (") is escaped by back slash (\);
    21  //   - finally, s is wrapped with double quotes (arg -> "arg"),
    22  //     but only if there is space or tab inside s.
    23  func EscapeArg(s string) string {
    24  	if len(s) == 0 {
    25  		return `""`
    26  	}
    27  	n := len(s)
    28  	hasSpace := false
    29  	for i := 0; i < len(s); i++ {
    30  		switch s[i] {
    31  		case '"', '\\':
    32  			n++
    33  		case ' ', '\t':
    34  			hasSpace = true
    35  		}
    36  	}
    37  	if hasSpace {
    38  		n += 2 // Reserve space for quotes.
    39  	}
    40  	if n == len(s) {
    41  		return s
    42  	}
    43  
    44  	qs := make([]byte, n)
    45  	j := 0
    46  	if hasSpace {
    47  		qs[j] = '"'
    48  		j++
    49  	}
    50  	slashes := 0
    51  	for i := 0; i < len(s); i++ {
    52  		switch s[i] {
    53  		default:
    54  			slashes = 0
    55  			qs[j] = s[i]
    56  		case '\\':
    57  			slashes++
    58  			qs[j] = s[i]
    59  		case '"':
    60  			for ; slashes > 0; slashes-- {
    61  				qs[j] = '\\'
    62  				j++
    63  			}
    64  			qs[j] = '\\'
    65  			j++
    66  			qs[j] = s[i]
    67  		}
    68  		j++
    69  	}
    70  	if hasSpace {
    71  		for ; slashes > 0; slashes-- {
    72  			qs[j] = '\\'
    73  			j++
    74  		}
    75  		qs[j] = '"'
    76  		j++
    77  	}
    78  	return string(qs[:j])
    79  }
    80  
    81  // ComposeCommandLine escapes and joins the given arguments suitable for use as a Windows command line,
    82  // in CreateProcess's CommandLine argument, CreateService/ChangeServiceConfig's BinaryPathName argument,
    83  // or any program that uses CommandLineToArgv.
    84  func ComposeCommandLine(args []string) string {
    85  	if len(args) == 0 {
    86  		return ""
    87  	}
    88  
    89  	// Per https://learn.microsoft.com/en-us/windows/win32/api/shellapi/nf-shellapi-commandlinetoargvw:
    90  	// “This function accepts command lines that contain a program name; the
    91  	// program name can be enclosed in quotation marks or not.”
    92  	//
    93  	// Unfortunately, it provides no means of escaping interior quotation marks
    94  	// within that program name, and we have no way to report them here.
    95  	prog := args[0]
    96  	mustQuote := len(prog) == 0
    97  	for i := 0; i < len(prog); i++ {
    98  		c := prog[i]
    99  		if c <= ' ' || (c == '"' && i == 0) {
   100  			// Force quotes for not only the ASCII space and tab as described in the
   101  			// MSDN article, but also ASCII control characters.
   102  			// The documentation for CommandLineToArgvW doesn't say what happens when
   103  			// the first argument is not a valid program name, but it empirically
   104  			// seems to drop unquoted control characters.
   105  			mustQuote = true
   106  			break
   107  		}
   108  	}
   109  	var commandLine []byte
   110  	if mustQuote {
   111  		commandLine = make([]byte, 0, len(prog)+2)
   112  		commandLine = append(commandLine, '"')
   113  		for i := 0; i < len(prog); i++ {
   114  			c := prog[i]
   115  			if c == '"' {
   116  				// This quote would interfere with our surrounding quotes.
   117  				// We have no way to report an error, so just strip out
   118  				// the offending character instead.
   119  				continue
   120  			}
   121  			commandLine = append(commandLine, c)
   122  		}
   123  		commandLine = append(commandLine, '"')
   124  	} else {
   125  		if len(args) == 1 {
   126  			// args[0] is a valid command line representing itself.
   127  			// No need to allocate a new slice or string for it.
   128  			return prog
   129  		}
   130  		commandLine = []byte(prog)
   131  	}
   132  
   133  	for _, arg := range args[1:] {
   134  		commandLine = append(commandLine, ' ')
   135  		// TODO(bcmills): since we're already appending to a slice, it would be nice
   136  		// to avoid the intermediate allocations of EscapeArg.
   137  		// Perhaps we can factor out an appendEscapedArg function.
   138  		commandLine = append(commandLine, EscapeArg(arg)...)
   139  	}
   140  	return string(commandLine)
   141  }
   142  
   143  // DecomposeCommandLine breaks apart its argument command line into unescaped parts using CommandLineToArgv,
   144  // as gathered from GetCommandLine, QUERY_SERVICE_CONFIG's BinaryPathName argument, or elsewhere that
   145  // command lines are passed around.
   146  // DecomposeCommandLine returns an error if commandLine contains NUL.
   147  func DecomposeCommandLine(commandLine string) ([]string, error) {
   148  	if len(commandLine) == 0 {
   149  		return []string{}, nil
   150  	}
   151  	utf16CommandLine, err := UTF16FromString(commandLine)
   152  	if err != nil {
   153  		return nil, errorspkg.New("string with NUL passed to DecomposeCommandLine")
   154  	}
   155  	var argc int32
   156  	argv, err := commandLineToArgv(&utf16CommandLine[0], &argc)
   157  	if err != nil {
   158  		return nil, err
   159  	}
   160  	defer LocalFree(Handle(unsafe.Pointer(argv)))
   161  
   162  	var args []string
   163  	for _, p := range unsafe.Slice(argv, argc) {
   164  		args = append(args, UTF16PtrToString(p))
   165  	}
   166  	return args, nil
   167  }
   168  
   169  // CommandLineToArgv parses a Unicode command line string and sets
   170  // argc to the number of parsed arguments.
   171  //
   172  // The returned memory should be freed using a single call to LocalFree.
   173  //
   174  // Note that although the return type of CommandLineToArgv indicates 8192
   175  // entries of up to 8192 characters each, the actual count of parsed arguments
   176  // may exceed 8192, and the documentation for CommandLineToArgvW does not mention
   177  // any bound on the lengths of the individual argument strings.
   178  // (See https://go.dev/issue/63236.)
   179  func CommandLineToArgv(cmd *uint16, argc *int32) (argv *[8192]*[8192]uint16, err error) {
   180  	argp, err := commandLineToArgv(cmd, argc)
   181  	argv = (*[8192]*[8192]uint16)(unsafe.Pointer(argp))
   182  	return argv, err
   183  }
   184  
   185  func CloseOnExec(fd Handle) {
   186  	SetHandleInformation(Handle(fd), HANDLE_FLAG_INHERIT, 0)
   187  }
   188  
   189  // FullPath retrieves the full path of the specified file.
   190  func FullPath(name string) (path string, err error) {
   191  	p, err := UTF16PtrFromString(name)
   192  	if err != nil {
   193  		return "", err
   194  	}
   195  	n := uint32(100)
   196  	for {
   197  		buf := make([]uint16, n)
   198  		n, err = GetFullPathName(p, uint32(len(buf)), &buf[0], nil)
   199  		if err != nil {
   200  			return "", err
   201  		}
   202  		if n <= uint32(len(buf)) {
   203  			return UTF16ToString(buf[:n]), nil
   204  		}
   205  	}
   206  }
   207  
   208  // NewProcThreadAttributeList allocates a new ProcThreadAttributeListContainer, with the requested maximum number of attributes.
   209  func NewProcThreadAttributeList(maxAttrCount uint32) (*ProcThreadAttributeListContainer, error) {
   210  	var size uintptr
   211  	err := initializeProcThreadAttributeList(nil, maxAttrCount, 0, &size)
   212  	if err != ERROR_INSUFFICIENT_BUFFER {
   213  		if err == nil {
   214  			return nil, errorspkg.New("unable to query buffer size from InitializeProcThreadAttributeList")
   215  		}
   216  		return nil, err
   217  	}
   218  	alloc, err := LocalAlloc(LMEM_FIXED, uint32(size))
   219  	if err != nil {
   220  		return nil, err
   221  	}
   222  	// size is guaranteed to be ≥1 by InitializeProcThreadAttributeList.
   223  	al := &ProcThreadAttributeListContainer{data: (*ProcThreadAttributeList)(unsafe.Pointer(alloc))}
   224  	err = initializeProcThreadAttributeList(al.data, maxAttrCount, 0, &size)
   225  	if err != nil {
   226  		return nil, err
   227  	}
   228  	return al, err
   229  }
   230  
   231  // Update modifies the ProcThreadAttributeList using UpdateProcThreadAttribute.
   232  func (al *ProcThreadAttributeListContainer) Update(attribute uintptr, value unsafe.Pointer, size uintptr) error {
   233  	al.pointers = append(al.pointers, value)
   234  	return updateProcThreadAttribute(al.data, 0, attribute, value, size, nil, nil)
   235  }
   236  
   237  // Delete frees ProcThreadAttributeList's resources.
   238  func (al *ProcThreadAttributeListContainer) Delete() {
   239  	deleteProcThreadAttributeList(al.data)
   240  	LocalFree(Handle(unsafe.Pointer(al.data)))
   241  	al.data = nil
   242  	al.pointers = nil
   243  }
   244  
   245  // List returns the actual ProcThreadAttributeList to be passed to StartupInfoEx.
   246  func (al *ProcThreadAttributeListContainer) List() *ProcThreadAttributeList {
   247  	return al.data
   248  }
   249
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