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passwd.go
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passwd.go
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// Copyright 2022, 2023 Chainguard, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package passwd
import (
"bufio"
"fmt"
"io"
"io/fs"
"os"
"strconv"
"strings"
apkfs "github.com/chainguard-dev/go-apk/pkg/fs"
)
// UserEntry contains the parsed data from an /etc/passwd entry.
type UserEntry struct {
UserName string
Password string
UID uint32
GID uint32
Info string
HomeDir string
Shell string
}
// UserFile contains the entries from an /etc/passwd file.
type UserFile struct {
Entries []UserEntry
fsys apkfs.FullFS
}
// ReadOrCreateUserFile parses an /etc/passwd file into a UserFile.
// An empty file is created if /etc/passwd is missing.
func ReadOrCreateUserFile(fsys apkfs.FullFS, filePath string) (UserFile, error) {
uf := UserFile{fsys: fsys}
file, err := fsys.OpenFile(filePath, os.O_RDONLY|os.O_CREATE, 0o644)
if err != nil {
return uf, fmt.Errorf("failed to open %s: %w", filePath, err)
}
defer file.Close()
if err := uf.Load(file); err != nil {
return uf, err
}
return uf, nil
}
// ReadUserFile parses an /etc/passwd file into a UserFile.
// If it is missing, returns an error.
func ReadUserFile(fsys fs.FS, filePath string) (UserFile, error) {
uf := UserFile{}
file, err := fsys.Open(filePath)
if err != nil {
return uf, fmt.Errorf("failed to open %s: %w", filePath, err)
}
defer file.Close()
if err := uf.Load(file); err != nil {
return uf, err
}
return uf, nil
}
// Load loads an /etc/passwd file into a UserFile from an io.Reader.
func (uf *UserFile) Load(r io.Reader) error {
scanner := bufio.NewScanner(r)
for scanner.Scan() {
ue := UserEntry{}
if err := ue.Parse(scanner.Text()); err != nil {
return fmt.Errorf("unable to parse: %w", err)
}
uf.Entries = append(uf.Entries, ue)
}
if err := scanner.Err(); err != nil {
return fmt.Errorf("unable to parse: %w", err)
}
return nil
}
// WriteFile writes an /etc/passwd file from a UserFile.
func (uf *UserFile) WriteFile(filePath string) error {
file, err := uf.fsys.Create(filePath)
if err != nil {
return fmt.Errorf("unable to open %s for writing: %w", filePath, err)
}
defer file.Close()
return uf.Write(file)
}
// Write writes an /etc/passwd file into an io.Writer.
func (uf *UserFile) Write(w io.Writer) error {
for _, ue := range uf.Entries {
if err := ue.Write(w); err != nil {
return fmt.Errorf("unable to write passwd entry: %w", err)
}
}
return nil
}
// Parse parses an /etc/passwd line into a UserEntry.
func (ue *UserEntry) Parse(line string) error {
line = strings.TrimSpace(line)
parts := strings.Split(line, ":")
if len(parts) != 7 {
return fmt.Errorf("malformed line, contains %d parts, expecting 7", len(parts))
}
ue.UserName = parts[0]
ue.Password = parts[1]
uid, err := strconv.Atoi(parts[2])
if err != nil {
return fmt.Errorf("failed to parse UID %s", parts[2])
}
ue.UID = uint32(uid)
gid, err := strconv.Atoi(parts[3])
if err != nil {
return fmt.Errorf("failed to parse GID %s", parts[3])
}
ue.GID = uint32(gid)
ue.Info = parts[4]
ue.HomeDir = parts[5]
ue.Shell = parts[6]
return nil
}
// Write writes an /etc/passwd line into an io.Writer.
func (ue *UserEntry) Write(w io.Writer) error {
_, err := fmt.Fprintf(w, "%s:%s:%d:%d:%s:%s:%s\n", ue.UserName, ue.Password, ue.UID, ue.GID, ue.Info, ue.HomeDir, ue.Shell)
return err
}