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package user
import (
"bufio"
"fmt"
"io"
"os"
"strconv"
"strings"
)
const (
minId = 0
maxId = 1<<31 - 1 //for 32-bit systems compatibility
)
var (
ErrRange = fmt.Errorf("Uids and gids must be in range %d-%d", minId, maxId)
)
type User struct {
Name string
Pass string
Uid int
Gid int
Gecos string
Home string
Shell string
}
type Group struct {
Name string
Pass string
Gid int
List []string
}
func parseLine(line string, v ...interface{}) {
if line == "" {
return
}
parts := strings.Split(line, ":")
for i, p := range parts {
if len(v) <= i {
// if we have more "parts" than we have places to put them, bail for great "tolerance" of naughty configuration files
break
}
switch e := v[i].(type) {
case *string:
// "root", "adm", "/bin/bash"
*e = p
case *int:
// "0", "4", "1000"
// ignore string to int conversion errors, for great "tolerance" of naughty configuration files
*e, _ = strconv.Atoi(p)
case *[]string:
// "", "root", "root,adm,daemon"
if p != "" {
*e = strings.Split(p, ",")
} else {
*e = []string{}
}
default:
// panic, because this is a programming/logic error, not a runtime one
panic("parseLine expects only pointers! argument " + strconv.Itoa(i) + " is not a pointer!")
}
}
}
func ParsePasswdFile(path string) ([]User, error) {
passwd, err := os.Open(path)
if err != nil {
return nil, err
}
defer passwd.Close()
return ParsePasswd(passwd)
}
func ParsePasswd(passwd io.Reader) ([]User, error) {
return ParsePasswdFilter(passwd, nil)
}
func ParsePasswdFileFilter(path string, filter func(User) bool) ([]User, error) {
passwd, err := os.Open(path)
if err != nil {
return nil, err
}
defer passwd.Close()
return ParsePasswdFilter(passwd, filter)
}
func ParsePasswdFilter(r io.Reader, filter func(User) bool) ([]User, error) {
if r == nil {
return nil, fmt.Errorf("nil source for passwd-formatted data")
}
var (
s = bufio.NewScanner(r)
out = []User{}
)
for s.Scan() {
if err := s.Err(); err != nil {
return nil, err
}
text := strings.TrimSpace(s.Text())
if text == "" {
continue
}
// see: man 5 passwd
// name:password:UID:GID:GECOS:directory:shell
// Name:Pass:Uid:Gid:Gecos:Home:Shell
// root:x:0:0:root:/root:/bin/bash
// adm:x:3:4:adm:/var/adm:/bin/false
p := User{}
parseLine(
text,
&p.Name, &p.Pass, &p.Uid, &p.Gid, &p.Gecos, &p.Home, &p.Shell,
)
if filter == nil || filter(p) {
out = append(out, p)
}
}
return out, nil
}
func ParseGroupFile(path string) ([]Group, error) {
group, err := os.Open(path)
if err != nil {
return nil, err
}
defer group.Close()
return ParseGroup(group)
}
func ParseGroup(group io.Reader) ([]Group, error) {
return ParseGroupFilter(group, nil)
}
func ParseGroupFileFilter(path string, filter func(Group) bool) ([]Group, error) {
group, err := os.Open(path)
if err != nil {
return nil, err
}
defer group.Close()
return ParseGroupFilter(group, filter)
}
func ParseGroupFilter(r io.Reader, filter func(Group) bool) ([]Group, error) {
if r == nil {
return nil, fmt.Errorf("nil source for group-formatted data")
}
var (
s = bufio.NewScanner(r)
out = []Group{}
)
for s.Scan() {
if err := s.Err(); err != nil {
return nil, err
}
text := s.Text()
if text == "" {
continue
}
// see: man 5 group
// group_name:password:GID:user_list
// Name:Pass:Gid:List
// root:x:0:root
// adm:x:4:root,adm,daemon
p := Group{}
parseLine(
text,
&p.Name, &p.Pass, &p.Gid, &p.List,
)
if filter == nil || filter(p) {
out = append(out, p)
}
}
return out, nil
}
type ExecUser struct {
Uid, Gid int
Sgids []int
Home string
}
// GetExecUserPath is a wrapper for GetExecUser. It reads data from each of the
// given file paths and uses that data as the arguments to GetExecUser. If the
// files cannot be opened for any reason, the error is ignored and a nil
// io.Reader is passed instead.
func GetExecUserPath(userSpec string, defaults *ExecUser, passwdPath, groupPath string) (*ExecUser, error) {
passwd, err := os.Open(passwdPath)
if err != nil {
passwd = nil
} else {
defer passwd.Close()
}
group, err := os.Open(groupPath)
if err != nil {
group = nil
} else {
defer group.Close()
}
return GetExecUser(userSpec, defaults, passwd, group)
}
// GetExecUser parses a user specification string (using the passwd and group
// readers as sources for /etc/passwd and /etc/group data, respectively). In
// the case of blank fields or missing data from the sources, the values in
// defaults is used.
//
// GetExecUser will return an error if a user or group literal could not be
// found in any entry in passwd and group respectively.
//
// Examples of valid user specifications are:
// * ""
// * "user"
// * "uid"
// * "user:group"
// * "uid:gid
// * "user:gid"
// * "uid:group"
func GetExecUser(userSpec string, defaults *ExecUser, passwd, group io.Reader) (*ExecUser, error) {
var (
userArg, groupArg string
name string
)
if defaults == nil {
defaults = new(ExecUser)
}
// Copy over defaults.
user := &ExecUser{
Uid: defaults.Uid,
Gid: defaults.Gid,
Sgids: defaults.Sgids,
Home: defaults.Home,
}
// Sgids slice *cannot* be nil.
if user.Sgids == nil {
user.Sgids = []int{}
}
// allow for userArg to have either "user" syntax, or optionally "user:group" syntax
parseLine(userSpec, &userArg, &groupArg)
users, err := ParsePasswdFilter(passwd, func(u User) bool {
if userArg == "" {
return u.Uid == user.Uid
}
return u.Name == userArg || strconv.Itoa(u.Uid) == userArg
})
if err != nil && passwd != nil {
if userArg == "" {
userArg = strconv.Itoa(user.Uid)
}
return nil, fmt.Errorf("Unable to find user %v: %v", userArg, err)
}
haveUser := users != nil && len(users) > 0
if haveUser {
// if we found any user entries that matched our filter, let's take the first one as "correct"
name = users[0].Name
user.Uid = users[0].Uid
user.Gid = users[0].Gid
user.Home = users[0].Home
} else if userArg != "" {
// we asked for a user but didn't find them... let's check to see if we wanted a numeric user
user.Uid, err = strconv.Atoi(userArg)
if err != nil {
// not numeric - we have to bail
return nil, fmt.Errorf("Unable to find user %v", userArg)
}
// Must be inside valid uid range.
if user.Uid < minId || user.Uid > maxId {
return nil, ErrRange
}
// if userArg couldn't be found in /etc/passwd but is numeric, just roll with it - this is legit
}
if groupArg != "" || name != "" {
groups, err := ParseGroupFilter(group, func(g Group) bool {
// Explicit group format takes precedence.
if groupArg != "" {
return g.Name == groupArg || strconv.Itoa(g.Gid) == groupArg
}
// Check if user is a member.
for _, u := range g.List {
if u == name {
return true
}
}
return false
})
if err != nil && group != nil {
return nil, fmt.Errorf("Unable to find groups for user %v: %v", users[0].Name, err)
}
haveGroup := groups != nil && len(groups) > 0
if groupArg != "" {
if haveGroup {
// if we found any group entries that matched our filter, let's take the first one as "correct"
user.Gid = groups[0].Gid
} else {
// we asked for a group but didn't find id... let's check to see if we wanted a numeric group
user.Gid, err = strconv.Atoi(groupArg)
if err != nil {
// not numeric - we have to bail
return nil, fmt.Errorf("Unable to find group %v", groupArg)
}
// Ensure gid is inside gid range.
if user.Gid < minId || user.Gid > maxId {
return nil, ErrRange
}
// if groupArg couldn't be found in /etc/group but is numeric, just roll with it - this is legit
}
} else if haveGroup {
// If implicit group format, fill supplementary gids.
user.Sgids = make([]int, len(groups))
for i, group := range groups {
user.Sgids[i] = group.Gid
}
}
}
return user, nil
}
// GetAdditionalGroupsPath looks up a list of groups by name or group id
// against the group file. If a group name cannot be found, an error will be
// returned. If a group id cannot be found, it will be returned as-is.
func GetAdditionalGroupsPath(additionalGroups []string, groupPath string) ([]int, error) {
groupReader, err := os.Open(groupPath)
if err != nil {
return nil, fmt.Errorf("Failed to open group file: %v", err)
}
defer groupReader.Close()
groups, err := ParseGroupFilter(groupReader, func(g Group) bool {
for _, ag := range additionalGroups {
if g.Name == ag || strconv.Itoa(g.Gid) == ag {
return true
}
}
return false
})
if err != nil {
return nil, fmt.Errorf("Unable to find additional groups %v: %v", additionalGroups, err)
}
gidMap := make(map[int]struct{})
for _, ag := range additionalGroups {
var found bool
for _, g := range groups {
// if we found a matched group either by name or gid, take the
// first matched as correct
if g.Name == ag || strconv.Itoa(g.Gid) == ag {
if _, ok := gidMap[g.Gid]; !ok {
gidMap[g.Gid] = struct{}{}
found = true
break
}
}
}
// we asked for a group but didn't find it. let's check to see
// if we wanted a numeric group
if !found {
gid, err := strconv.Atoi(ag)
if err != nil {
return nil, fmt.Errorf("Unable to find group %s", ag)
}
// Ensure gid is inside gid range.
if gid < minId || gid > maxId {
return nil, ErrRange
}
gidMap[gid] = struct{}{}
}
}
gids := []int{}
for gid := range gidMap {
gids = append(gids, gid)
}
return gids, nil
}