442 lines
11 KiB
Go
442 lines
11 KiB
Go
package user
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import (
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"bufio"
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"fmt"
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"io"
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"os"
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"strconv"
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"strings"
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)
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const (
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minId = 0
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maxId = 1<<31 - 1 //for 32-bit systems compatibility
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)
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var (
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ErrRange = fmt.Errorf("uids and gids must be in range %d-%d", minId, maxId)
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)
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type User struct {
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Name string
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Pass string
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Uid int
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Gid int
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Gecos string
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Home string
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Shell string
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}
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type Group struct {
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Name string
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Pass string
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Gid int
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List []string
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}
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func parseLine(line string, v ...interface{}) {
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if line == "" {
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return
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}
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parts := strings.Split(line, ":")
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for i, p := range parts {
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// Ignore cases where we don't have enough fields to populate the arguments.
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// Some configuration files like to misbehave.
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if len(v) <= i {
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break
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}
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// Use the type of the argument to figure out how to parse it, scanf() style.
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// This is legit.
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switch e := v[i].(type) {
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case *string:
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*e = p
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case *int:
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// "numbers", with conversion errors ignored because of some misbehaving configuration files.
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*e, _ = strconv.Atoi(p)
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case *[]string:
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// Comma-separated lists.
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if p != "" {
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*e = strings.Split(p, ",")
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} else {
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*e = []string{}
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}
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default:
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// Someone goof'd when writing code using this function. Scream so they can hear us.
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panic(fmt.Sprintf("parseLine only accepts {*string, *int, *[]string} as arguments! %#v is not a pointer!", e))
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}
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}
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}
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func ParsePasswdFile(path string) ([]User, error) {
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passwd, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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defer passwd.Close()
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return ParsePasswd(passwd)
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}
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func ParsePasswd(passwd io.Reader) ([]User, error) {
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return ParsePasswdFilter(passwd, nil)
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}
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func ParsePasswdFileFilter(path string, filter func(User) bool) ([]User, error) {
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passwd, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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defer passwd.Close()
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return ParsePasswdFilter(passwd, filter)
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}
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func ParsePasswdFilter(r io.Reader, filter func(User) bool) ([]User, error) {
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if r == nil {
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return nil, fmt.Errorf("nil source for passwd-formatted data")
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}
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var (
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s = bufio.NewScanner(r)
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out = []User{}
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)
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for s.Scan() {
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if err := s.Err(); err != nil {
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return nil, err
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}
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line := strings.TrimSpace(s.Text())
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if line == "" {
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continue
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}
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// see: man 5 passwd
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// name:password:UID:GID:GECOS:directory:shell
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// Name:Pass:Uid:Gid:Gecos:Home:Shell
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// root:x:0:0:root:/root:/bin/bash
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// adm:x:3:4:adm:/var/adm:/bin/false
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p := User{}
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parseLine(line, &p.Name, &p.Pass, &p.Uid, &p.Gid, &p.Gecos, &p.Home, &p.Shell)
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if filter == nil || filter(p) {
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out = append(out, p)
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}
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}
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return out, nil
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}
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func ParseGroupFile(path string) ([]Group, error) {
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group, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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defer group.Close()
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return ParseGroup(group)
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}
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func ParseGroup(group io.Reader) ([]Group, error) {
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return ParseGroupFilter(group, nil)
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}
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func ParseGroupFileFilter(path string, filter func(Group) bool) ([]Group, error) {
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group, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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defer group.Close()
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return ParseGroupFilter(group, filter)
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}
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func ParseGroupFilter(r io.Reader, filter func(Group) bool) ([]Group, error) {
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if r == nil {
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return nil, fmt.Errorf("nil source for group-formatted data")
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}
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var (
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s = bufio.NewScanner(r)
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out = []Group{}
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)
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for s.Scan() {
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if err := s.Err(); err != nil {
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return nil, err
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}
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text := s.Text()
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if text == "" {
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continue
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}
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// see: man 5 group
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// group_name:password:GID:user_list
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// Name:Pass:Gid:List
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// root:x:0:root
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// adm:x:4:root,adm,daemon
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p := Group{}
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parseLine(text, &p.Name, &p.Pass, &p.Gid, &p.List)
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if filter == nil || filter(p) {
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out = append(out, p)
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}
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}
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return out, nil
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}
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type ExecUser struct {
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Uid int
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Gid int
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Sgids []int
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Home string
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}
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// GetExecUserPath is a wrapper for GetExecUser. It reads data from each of the
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// given file paths and uses that data as the arguments to GetExecUser. If the
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// files cannot be opened for any reason, the error is ignored and a nil
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// io.Reader is passed instead.
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func GetExecUserPath(userSpec string, defaults *ExecUser, passwdPath, groupPath string) (*ExecUser, error) {
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var passwd, group io.Reader
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if passwdFile, err := os.Open(passwdPath); err == nil {
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passwd = passwdFile
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defer passwdFile.Close()
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}
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if groupFile, err := os.Open(groupPath); err == nil {
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group = groupFile
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defer groupFile.Close()
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}
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return GetExecUser(userSpec, defaults, passwd, group)
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}
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// GetExecUser parses a user specification string (using the passwd and group
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// readers as sources for /etc/passwd and /etc/group data, respectively). In
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// the case of blank fields or missing data from the sources, the values in
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// defaults is used.
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//
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// GetExecUser will return an error if a user or group literal could not be
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// found in any entry in passwd and group respectively.
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//
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// Examples of valid user specifications are:
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// * ""
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// * "user"
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// * "uid"
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// * "user:group"
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// * "uid:gid
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// * "user:gid"
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// * "uid:group"
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//
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// It should be noted that if you specify a numeric user or group id, they will
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// not be evaluated as usernames (only the metadata will be filled). So attempting
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// to parse a user with user.Name = "1337" will produce the user with a UID of
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// 1337.
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func GetExecUser(userSpec string, defaults *ExecUser, passwd, group io.Reader) (*ExecUser, error) {
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if defaults == nil {
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defaults = new(ExecUser)
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}
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// Copy over defaults.
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user := &ExecUser{
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Uid: defaults.Uid,
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Gid: defaults.Gid,
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Sgids: defaults.Sgids,
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Home: defaults.Home,
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}
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// Sgids slice *cannot* be nil.
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if user.Sgids == nil {
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user.Sgids = []int{}
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}
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// Allow for userArg to have either "user" syntax, or optionally "user:group" syntax
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var userArg, groupArg string
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parseLine(userSpec, &userArg, &groupArg)
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// Convert userArg and groupArg to be numeric, so we don't have to execute
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// Atoi *twice* for each iteration over lines.
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uidArg, uidErr := strconv.Atoi(userArg)
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gidArg, gidErr := strconv.Atoi(groupArg)
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// Find the matching user.
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users, err := ParsePasswdFilter(passwd, func(u User) bool {
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if userArg == "" {
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// Default to current state of the user.
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return u.Uid == user.Uid
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}
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if uidErr == nil {
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// If the userArg is numeric, always treat it as a UID.
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return uidArg == u.Uid
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}
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return u.Name == userArg
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})
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// If we can't find the user, we have to bail.
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if err != nil && passwd != nil {
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if userArg == "" {
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userArg = strconv.Itoa(user.Uid)
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}
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return nil, fmt.Errorf("unable to find user %s: %v", userArg, err)
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}
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var matchedUserName string
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if len(users) > 0 {
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// First match wins, even if there's more than one matching entry.
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matchedUserName = users[0].Name
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user.Uid = users[0].Uid
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user.Gid = users[0].Gid
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user.Home = users[0].Home
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} else if userArg != "" {
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// If we can't find a user with the given username, the only other valid
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// option is if it's a numeric username with no associated entry in passwd.
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if uidErr != nil {
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// Not numeric.
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return nil, fmt.Errorf("unable to find user %s: %v", userArg, ErrNoPasswdEntries)
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}
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user.Uid = uidArg
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// Must be inside valid uid range.
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if user.Uid < minId || user.Uid > maxId {
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return nil, ErrRange
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}
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// Okay, so it's numeric. We can just roll with this.
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}
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// On to the groups. If we matched a username, we need to do this because of
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// the supplementary group IDs.
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if groupArg != "" || matchedUserName != "" {
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groups, err := ParseGroupFilter(group, func(g Group) bool {
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// If the group argument isn't explicit, we'll just search for it.
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if groupArg == "" {
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// Check if user is a member of this group.
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for _, u := range g.List {
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if u == matchedUserName {
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return true
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}
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}
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return false
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}
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if gidErr == nil {
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// If the groupArg is numeric, always treat it as a GID.
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return gidArg == g.Gid
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}
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return g.Name == groupArg
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})
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if err != nil && group != nil {
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return nil, fmt.Errorf("unable to find groups for spec %v: %v", matchedUserName, err)
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}
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// Only start modifying user.Gid if it is in explicit form.
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if groupArg != "" {
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if len(groups) > 0 {
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// First match wins, even if there's more than one matching entry.
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user.Gid = groups[0].Gid
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} else {
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// If we can't find a group with the given name, the only other valid
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// option is if it's a numeric group name with no associated entry in group.
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if gidErr != nil {
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// Not numeric.
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return nil, fmt.Errorf("unable to find group %s: %v", groupArg, ErrNoGroupEntries)
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}
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user.Gid = gidArg
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// Must be inside valid gid range.
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if user.Gid < minId || user.Gid > maxId {
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return nil, ErrRange
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}
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// Okay, so it's numeric. We can just roll with this.
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}
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} else if len(groups) > 0 {
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// Supplementary group ids only make sense if in the implicit form.
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user.Sgids = make([]int, len(groups))
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for i, group := range groups {
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user.Sgids[i] = group.Gid
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}
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}
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}
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return user, nil
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}
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// GetAdditionalGroups looks up a list of groups by name or group id
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// against the given /etc/group formatted data. If a group name cannot
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// be found, an error will be returned. If a group id cannot be found,
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// or the given group data is nil, the id will be returned as-is
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// provided it is in the legal range.
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func GetAdditionalGroups(additionalGroups []string, group io.Reader) ([]int, error) {
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var groups = []Group{}
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if group != nil {
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var err error
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groups, err = ParseGroupFilter(group, func(g Group) bool {
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for _, ag := range additionalGroups {
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if g.Name == ag || strconv.Itoa(g.Gid) == ag {
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return true
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}
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}
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return false
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})
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if err != nil {
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return nil, fmt.Errorf("Unable to find additional groups %v: %v", additionalGroups, err)
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}
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}
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gidMap := make(map[int]struct{})
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for _, ag := range additionalGroups {
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var found bool
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for _, g := range groups {
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// if we found a matched group either by name or gid, take the
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// first matched as correct
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if g.Name == ag || strconv.Itoa(g.Gid) == ag {
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if _, ok := gidMap[g.Gid]; !ok {
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gidMap[g.Gid] = struct{}{}
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found = true
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break
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}
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}
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}
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// we asked for a group but didn't find it. let's check to see
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// if we wanted a numeric group
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if !found {
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gid, err := strconv.Atoi(ag)
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if err != nil {
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return nil, fmt.Errorf("Unable to find group %s", ag)
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}
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// Ensure gid is inside gid range.
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if gid < minId || gid > maxId {
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return nil, ErrRange
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}
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gidMap[gid] = struct{}{}
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}
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}
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gids := []int{}
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for gid := range gidMap {
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gids = append(gids, gid)
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}
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return gids, nil
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}
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// GetAdditionalGroupsPath is a wrapper around GetAdditionalGroups
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// that opens the groupPath given and gives it as an argument to
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// GetAdditionalGroups.
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func GetAdditionalGroupsPath(additionalGroups []string, groupPath string) ([]int, error) {
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var group io.Reader
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if groupFile, err := os.Open(groupPath); err == nil {
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group = groupFile
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defer groupFile.Close()
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}
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return GetAdditionalGroups(additionalGroups, group)
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}
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