aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/go/_std_1.21/src/os/user/lookup_unix.go
blob: a4308269e04b33a7328acb4ec40c9098ba4c9c99 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
// Copyright 2016 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.

//go:build ((unix && !android) || (js && wasm) || wasip1) && ((!cgo && !darwin) || osusergo)

package user

import (
	"bufio"
	"bytes"
	"errors"
	"io"
	"os"
	"strconv"
	"strings"
)

// lineFunc returns a value, an error, or (nil, nil) to skip the row.
type lineFunc func(line []byte) (v any, err error)

// readColonFile parses r as an /etc/group or /etc/passwd style file, running
// fn for each row. readColonFile returns a value, an error, or (nil, nil) if
// the end of the file is reached without a match.
//
// readCols is the minimum number of colon-separated fields that will be passed
// to fn; in a long line additional fields may be silently discarded.
func readColonFile(r io.Reader, fn lineFunc, readCols int) (v any, err error) {
	rd := bufio.NewReader(r)

	// Read the file line-by-line.
	for {
		var isPrefix bool
		var wholeLine []byte

		// Read the next line. We do so in chunks (as much as reader's
		// buffer is able to keep), check if we read enough columns
		// already on each step and store final result in wholeLine.
		for {
			var line []byte
			line, isPrefix, err = rd.ReadLine()

			if err != nil {
				// We should return (nil, nil) if EOF is reached
				// without a match.
				if err == io.EOF {
					err = nil
				}
				return nil, err
			}

			// Simple common case: line is short enough to fit in a
			// single reader's buffer.
			if !isPrefix && len(wholeLine) == 0 {
				wholeLine = line
				break
			}

			wholeLine = append(wholeLine, line...)

			// Check if we read the whole line (or enough columns)
			// already.
			if !isPrefix || bytes.Count(wholeLine, []byte{':'}) >= readCols {
				break
			}
		}

		// There's no spec for /etc/passwd or /etc/group, but we try to follow
		// the same rules as the glibc parser, which allows comments and blank
		// space at the beginning of a line.
		wholeLine = bytes.TrimSpace(wholeLine)
		if len(wholeLine) == 0 || wholeLine[0] == '#' {
			continue
		}
		v, err = fn(wholeLine)
		if v != nil || err != nil {
			return
		}

		// If necessary, skip the rest of the line
		for ; isPrefix; _, isPrefix, err = rd.ReadLine() {
			if err != nil {
				// We should return (nil, nil) if EOF is reached without a match.
				if err == io.EOF {
					err = nil
				}
				return nil, err
			}
		}
	}
}

func matchGroupIndexValue(value string, idx int) lineFunc {
	var leadColon string
	if idx > 0 {
		leadColon = ":"
	}
	substr := []byte(leadColon + value + ":")
	return func(line []byte) (v any, err error) {
		if !bytes.Contains(line, substr) || bytes.Count(line, colon) < 3 {
			return
		}
		// wheel:*:0:root
		parts := strings.SplitN(string(line), ":", 4)
		if len(parts) < 4 || parts[0] == "" || parts[idx] != value ||
			// If the file contains +foo and you search for "foo", glibc
			// returns an "invalid argument" error. Similarly, if you search
			// for a gid for a row where the group name starts with "+" or "-",
			// glibc fails to find the record.
			parts[0][0] == '+' || parts[0][0] == '-' {
			return
		}
		if _, err := strconv.Atoi(parts[2]); err != nil {
			return nil, nil
		}
		return &Group{Name: parts[0], Gid: parts[2]}, nil
	}
}

func findGroupId(id string, r io.Reader) (*Group, error) {
	if v, err := readColonFile(r, matchGroupIndexValue(id, 2), 3); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*Group), nil
	}
	return nil, UnknownGroupIdError(id)
}

func findGroupName(name string, r io.Reader) (*Group, error) {
	if v, err := readColonFile(r, matchGroupIndexValue(name, 0), 3); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*Group), nil
	}
	return nil, UnknownGroupError(name)
}

// returns a *User for a row if that row's has the given value at the
// given index.
func matchUserIndexValue(value string, idx int) lineFunc {
	var leadColon string
	if idx > 0 {
		leadColon = ":"
	}
	substr := []byte(leadColon + value + ":")
	return func(line []byte) (v any, err error) {
		if !bytes.Contains(line, substr) || bytes.Count(line, colon) < 6 {
			return
		}
		// kevin:x:1005:1006::/home/kevin:/usr/bin/zsh
		parts := strings.SplitN(string(line), ":", 7)
		if len(parts) < 6 || parts[idx] != value || parts[0] == "" ||
			parts[0][0] == '+' || parts[0][0] == '-' {
			return
		}
		if _, err := strconv.Atoi(parts[2]); err != nil {
			return nil, nil
		}
		if _, err := strconv.Atoi(parts[3]); err != nil {
			return nil, nil
		}
		u := &User{
			Username: parts[0],
			Uid:      parts[2],
			Gid:      parts[3],
			Name:     parts[4],
			HomeDir:  parts[5],
		}
		// The pw_gecos field isn't quite standardized. Some docs
		// say: "It is expected to be a comma separated list of
		// personal data where the first item is the full name of the
		// user."
		u.Name, _, _ = strings.Cut(u.Name, ",")
		return u, nil
	}
}

func findUserId(uid string, r io.Reader) (*User, error) {
	i, e := strconv.Atoi(uid)
	if e != nil {
		return nil, errors.New("user: invalid userid " + uid)
	}
	if v, err := readColonFile(r, matchUserIndexValue(uid, 2), 6); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*User), nil
	}
	return nil, UnknownUserIdError(i)
}

func findUsername(name string, r io.Reader) (*User, error) {
	if v, err := readColonFile(r, matchUserIndexValue(name, 0), 6); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*User), nil
	}
	return nil, UnknownUserError(name)
}

func lookupGroup(groupname string) (*Group, error) {
	f, err := os.Open(groupFile)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return findGroupName(groupname, f)
}

func lookupGroupId(id string) (*Group, error) {
	f, err := os.Open(groupFile)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return findGroupId(id, f)
}

func lookupUser(username string) (*User, error) {
	f, err := os.Open(userFile)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return findUsername(username, f)
}

func lookupUserId(uid string) (*User, error) {
	f, err := os.Open(userFile)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return findUserId(uid, f)
}