121 lines
3.5 KiB
Go
121 lines
3.5 KiB
Go
// Mgmt
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// Copyright (C) James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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package util
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import (
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"bufio"
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"context"
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"fmt"
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"os"
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"os/exec"
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"strings"
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"syscall"
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)
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const (
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// EtcPasswdFile is the location of the /etc/passwd file.
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EtcPasswdFile = "/etc/passwd"
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// ErrUsernameNotFound means we couldn't find that username.
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ErrUsernameNotFound = Error("can't find username")
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)
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// UserShell returns shell of the user.
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// TODO: return a well-known error if the user is simply not found.
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func UserShell(ctx context.Context, username string) (string, error) {
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// TODO: use getpwnam_r ?
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// First see if we can use `getent` to get the passwd database.
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if shell, err := getentShell(ctx, username); err == nil {
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return shell, nil
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}
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// We can always look in /etc/passwd manually.
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shell, err := passwdShell(ctx, username)
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if err != nil {
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return "", err
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}
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return shell, nil
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}
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// getentShell gets a user shell by running the `getent` command.
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func getentShell(ctx context.Context, username string) (string, error) {
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if username == "" {
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return "", fmt.Errorf("empty username")
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}
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getent, err := exec.LookPath("getent")
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if err != nil {
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return "", err
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}
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args := []string{
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"passwd",
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username,
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}
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cmd := exec.CommandContext(ctx, getent, args...)
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cmd.SysProcAttr = &syscall.SysProcAttr{
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Setpgid: true,
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Pgid: 0,
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}
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// XXX: return ErrUsernameNotFound where appropriate
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output, err := cmd.Output()
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if err != nil {
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return "", err
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}
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fields := strings.SplitN(strings.TrimSuffix(string(output), "\n"), ":", 7)
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if len(fields) != 7 {
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return "", err
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}
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return fields[6], nil
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}
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// passwdShell gets a user shell by looking through the `/etc/passwd` file.
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func passwdShell(ctx context.Context, username string) (string, error) {
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f, err := os.Open(EtcPasswdFile)
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if err != nil {
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return "", err
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}
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defer f.Close()
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s := bufio.NewScanner(f)
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for s.Scan() {
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fields := strings.SplitN(strings.TrimSuffix(s.Text(), "\n"), ":", 7)
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if len(fields) == 7 && fields[0] == username {
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return fields[6], nil
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}
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}
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if err := s.Err(); err != nil {
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return "", err
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}
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return "", ErrUsernameNotFound
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}
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