netrc.go

     1  // Copyright 2019 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  package auth
     6  
     7  import (
     8  	"os"
     9  	"path/filepath"
    10  	"runtime"
    11  	"strings"
    12  	"sync"
    13  )
    14  
    15  type netrcLine struct {
    16  	machine  string
    17  	login    string
    18  	password string
    19  }
    20  
    21  func parseNetrc(data string) []netrcLine {
    22  	// See https://www.gnu.org/software/inetutils/manual/html_node/The-_002enetrc-file.html
    23  	// for documentation on the .netrc format.
    24  	var nrc []netrcLine
    25  	var l netrcLine
    26  	inMacro := false
    27  	for _, line := range strings.Split(data, "\n") {
    28  		if inMacro {
    29  			if line == "" {
    30  				inMacro = false
    31  			}
    32  			continue
    33  		}
    34  
    35  		f := strings.Fields(line)
    36  		i := 0
    37  		for ; i < len(f)-1; i += 2 {
    38  			// Reset at each "machine" token.
    39  			// “The auto-login process searches the .netrc file for a machine token
    40  			// that matches […]. Once a match is made, the subsequent .netrc tokens
    41  			// are processed, stopping when the end of file is reached or another
    42  			// machine or a default token is encountered.”
    43  			switch f[i] {
    44  			case "machine":
    45  				l = netrcLine{machine: f[i+1]}
    46  			case "default":
    47  				break
    48  			case "login":
    49  				l.login = f[i+1]
    50  			case "password":
    51  				l.password = f[i+1]
    52  			case "macdef":
    53  				// “A macro is defined with the specified name; its contents begin with
    54  				// the next .netrc line and continue until a null line (consecutive
    55  				// new-line characters) is encountered.”
    56  				inMacro = true
    57  			}
    58  			if l.machine != "" && l.login != "" && l.password != "" {
    59  				nrc = append(nrc, l)
    60  				l = netrcLine{}
    61  			}
    62  		}
    63  
    64  		if i < len(f) && f[i] == "default" {
    65  			// “There can be only one default token, and it must be after all machine tokens.”
    66  			break
    67  		}
    68  	}
    69  
    70  	return nrc
    71  }
    72  
    73  func netrcPath() (string, error) {
    74  	if env := os.Getenv("NETRC"); env != "" {
    75  		return env, nil
    76  	}
    77  	dir, err := os.UserHomeDir()
    78  	if err != nil {
    79  		return "", err
    80  	}
    81  
    82  	// Prioritize _netrc on Windows for compatibility.
    83  	if runtime.GOOS == "windows" {
    84  		legacyPath := filepath.Join(dir, "_netrc")
    85  		_, err := os.Stat(legacyPath)
    86  		if err == nil {
    87  			return legacyPath, nil
    88  		}
    89  		if !os.IsNotExist(err) {
    90  			return "", err
    91  		}
    92  
    93  	}
    94  	// Use the .netrc file (fall back to it if we're on Windows).
    95  	return filepath.Join(dir, ".netrc"), nil
    96  }
    97  
    98  var readNetrc = sync.OnceValues(func() ([]netrcLine, error) {
    99  	path, err := netrcPath()
   100  	if err != nil {
   101  		return nil, err
   102  	}
   103  
   104  	data, err := os.ReadFile(path)
   105  	if err != nil {
   106  		if os.IsNotExist(err) {
   107  			err = nil
   108  		}
   109  		return nil, err
   110  	}
   111  
   112  	return parseNetrc(string(data)), nil
   113  })
   114
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