package user
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"os"
"strconv"
"strings"
)
const (
minID = 0
maxID = 1<<31 - 1 // for 32-bit systems compatibility
)
var (
// ErrNoPasswdEntries is returned if no matching entries were found in /etc/group.
ErrNoPasswdEntries = errors.New("no matching entries in passwd file")
// ErrNoGroupEntries is returned if no matching entries were found in /etc/passwd.
ErrNoGroupEntries = errors.New("no matching entries in group file")
// ErrRange is returned if a UID or GID is outside of the valid range.
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
}
// SubID represents an entry in /etc/sub{u,g}id
type SubID struct {
Name string
SubID int64
Count int64
}
// IDMap represents an entry in /proc/PID/{u,g}id_map
type IDMap struct {
ID int64
ParentID int64
Count int64
}
func parseLine(line []byte, v ...interface{}) {
parseParts(bytes.Split(line, []byte(":")), v...)
}
func parseParts(parts [][]byte, v ...interface{}) {
if len(parts) == 0 {
return
}
for i, p := range parts {
// Ignore cases where we don't have enough fields to populate the arguments.
// Some configuration files like to misbehave.
if len(v) <= i {
break
}
// Use the type of the argument to figure out how to parse it, scanf() style.
// This is legit.
switch e := v[i].(type) {
case *string:
*e = string(p)
case *int:
// "numbers", with conversion errors ignored because of some misbehaving configuration files.
*e, _ = strconv.Atoi(string(p))
case *int64:
*e, _ = strconv.ParseInt(string(p), 10, 64)
case *[]string:
// Comma-separated lists.
if len(p) != 0 {
*e = strings.Split(string(p), ",")
} else {
*e = []string{}
}
default:
// Someone goof'd when writing code using this function. Scream so they can hear us.
panic(fmt.Sprintf("parseLine only accepts {*string, *int, *int64, *[]string} as arguments! %#v is not a pointer!", e))
}
}
}
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, errors.New("nil source for passwd-formatted data")
}
var (
s = bufio.NewScanner(r)
out = []User{}
)
for s.Scan() {
line := bytes.TrimSpace(s.Bytes())
if len(line) == 0 {
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(line, &p.Name, &p.Pass, &p.Uid, &p.Gid, &p.Gecos, &p.Home, &p.Shell)
if filter == nil || filter(p) {
out = append(out, p)
}
}
if err := s.Err(); err != nil {
return nil, err
}
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, errors.New("nil source for group-formatted data")
}
rd := bufio.NewReader(r)
out := []Group{}
// Read the file line-by-line.
for {
var (
isPrefix bool
wholeLine []byte
err error
)
// 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 no error if EOF is reached
// without a match.
if err == io.EOF {
err = nil
}
return out, 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 already.
if !isPrefix {
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
}
// 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(wholeLine, &p.Name, &p.Pass, &p.Gid, &p.List)
if filter == nil || filter(p) {
out = append(out, p)
}
}
}
type ExecUser struct {
Uid int
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) {
var passwd, group io.Reader
if passwdFile, err := os.Open(passwdPath); err == nil {
passwd = passwdFile
defer passwdFile.Close()
}
if groupFile, err := os.Open(groupPath); err == nil {
group = groupFile
defer groupFile.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"
//
// It should be noted that if you specify a numeric user or group id, they will
// not be evaluated as usernames (only the metadata will be filled). So attempting
// to parse a user with user.Name = "1337" will produce the user with a UID of
// 1337.
func GetExecUser(userSpec string, defaults *ExecUser, passwd, group io.Reader) (*ExecUser, error) {
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
var userArg, groupArg string
parseLine([]byte(userSpec), &userArg, &groupArg)
// Convert userArg and groupArg to be numeric, so we don't have to execute
// Atoi *twice* for each iteration over lines.
uidArg, uidErr := strconv.Atoi(userArg)
gidArg, gidErr := strconv.Atoi(groupArg)
// Find the matching user.
users, err := ParsePasswdFilter(passwd, func(u User) bool {
if userArg == "" {
// Default to current state of the user.
return u.Uid == user.Uid
}
if uidErr == nil {
// If the userArg is numeric, always treat it as a UID.
return uidArg == u.Uid
}
return u.Name == userArg
})
// If we can't find the user, we have to bail.
if err != nil && passwd != nil {
if userArg == "" {
userArg = strconv.Itoa(user.Uid)
}
return nil, fmt.Errorf("unable to find user %s: %w", userArg, err)
}
var matchedUserName string
if len(users) > 0 {
// First match wins, even if there's more than one matching entry.
matchedUserName = users[0].Name
user.Uid = users[0].Uid
user.Gid = users[0].Gid
user.Home = users[0].Home
} else if userArg != "" {
// If we can't find a user with the given username, the only other valid
// option is if it's a numeric username with no associated entry in passwd.
if uidErr != nil {
// Not numeric.
return nil, fmt.Errorf("unable to find user %s: %w", userArg, ErrNoPasswdEntries)
}
user.Uid = uidArg
// Must be inside valid uid range.
if user.Uid < minID || user.Uid > maxID {
return nil, ErrRange
}
// Okay, so it's numeric. We can just roll with this.
}
// On to the groups. If we matched a username, we need to do this because of
// the supplementary group IDs.
if groupArg != "" || matchedUserName != "" {
groups, err := ParseGroupFilter(group, func(g Group) bool {
// If the group argument isn't explicit, we'll just search for it.
if groupArg == "" {
// Check if user is a member of this group.
for _, u := range g.List {
if u == matchedUserName {
return true
}
}
return false
}
if gidErr == nil {
// If the groupArg is numeric, always treat it as a GID.
return gidArg == g.Gid
}
return g.Name == groupArg
})
if err != nil && group != nil {
return nil, fmt.Errorf("unable to find groups for spec %v: %w", matchedUserName, err)
}
// Only start modifying user.Gid if it is in explicit form.
if groupArg != "" {
if len(groups) > 0 {
// First match wins, even if there's more than one matching entry.
user.Gid = groups[0].Gid
} else {
// If we can't find a group with the given name, the only other valid
// option is if it's a numeric group name with no associated entry in group.
if gidErr != nil {
// Not numeric.
return nil, fmt.Errorf("unable to find group %s: %w", groupArg, ErrNoGroupEntries)
}
user.Gid = gidArg
// Must be inside valid gid range.
if user.Gid < minID || user.Gid > maxID {
return nil, ErrRange
}
// Okay, so it's numeric. We can just roll with this.
}
} else if len(groups) > 0 {
// Supplementary group ids only make sense if in the implicit form.
user.Sgids = make([]int, len(groups))
for i, group := range groups {
user.Sgids[i] = group.Gid
}
}
}
return user, nil
}
// GetAdditionalGroups looks up a list of groups by name or group id
// against the given /etc/group formatted data. If a group name cannot
// be found, an error will be returned. If a group id cannot be found,
// or the given group data is nil, the id will be returned as-is
// provided it is in the legal range.
func GetAdditionalGroups(additionalGroups []string, group io.Reader) ([]int, error) {
groups := []Group{}
if group != nil {
var err error
groups, err = ParseGroupFilter(group, 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: %w", 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.ParseInt(ag, 10, 64)
if err != nil {
// Not a numeric ID either.
return nil, fmt.Errorf("Unable to find group %s: %w", ag, ErrNoGroupEntries)
}
// Ensure gid is inside gid range.
if gid < minID || gid > maxID {
return nil, ErrRange
}
gidMap[int(gid)] = struct{}{}
}
}
gids := []int{}
for gid := range gidMap {
gids = append(gids, gid)
}
return gids, nil
}
// GetAdditionalGroupsPath is a wrapper around GetAdditionalGroups
// that opens the groupPath given and gives it as an argument to
// GetAdditionalGroups.
func GetAdditionalGroupsPath(additionalGroups []string, groupPath string) ([]int, error) {
var group io.Reader
if groupFile, err := os.Open(groupPath); err == nil {
group = groupFile
defer groupFile.Close()
}
return GetAdditionalGroups(additionalGroups, group)
}
func ParseSubIDFile(path string) ([]SubID, error) {
subid, err := os.Open(path)
if err != nil {
return nil, err
}
defer subid.Close()
return ParseSubID(subid)
}
func ParseSubID(subid io.Reader) ([]SubID, error) {
return ParseSubIDFilter(subid, nil)
}
func ParseSubIDFileFilter(path string, filter func(SubID) bool) ([]SubID, error) {
subid, err := os.Open(path)
if err != nil {
return nil, err
}
defer subid.Close()
return ParseSubIDFilter(subid, filter)
}
func ParseSubIDFilter(r io.Reader, filter func(SubID) bool) ([]SubID, error) {
if r == nil {
return nil, errors.New("nil source for subid-formatted data")
}
var (
s = bufio.NewScanner(r)
out = []SubID{}
)
for s.Scan() {
line := bytes.TrimSpace(s.Bytes())
if len(line) == 0 {
continue
}
// see: man 5 subuid
p := SubID{}
parseLine(line, &p.Name, &p.SubID, &p.Count)
if filter == nil || filter(p) {
out = append(out, p)
}
}
if err := s.Err(); err != nil {
return nil, err
}
return out, nil
}
func ParseIDMapFile(path string) ([]IDMap, error) {
r, err := os.Open(path)
if err != nil {
return nil, err
}
defer r.Close()
return ParseIDMap(r)
}
func ParseIDMap(r io.Reader) ([]IDMap, error) {
return ParseIDMapFilter(r, nil)
}
func ParseIDMapFileFilter(path string, filter func(IDMap) bool) ([]IDMap, error) {
r, err := os.Open(path)
if err != nil {
return nil, err
}
defer r.Close()
return ParseIDMapFilter(r, filter)
}
func ParseIDMapFilter(r io.Reader, filter func(IDMap) bool) ([]IDMap, error) {
if r == nil {
return nil, errors.New("nil source for idmap-formatted data")
}
var (
s = bufio.NewScanner(r)
out = []IDMap{}
)
for s.Scan() {
line := bytes.TrimSpace(s.Bytes())
if len(line) == 0 {
continue
}
// see: man 7 user_namespaces
p := IDMap{}
parseParts(bytes.Fields(line), &p.ID, &p.ParentID, &p.Count)
if filter == nil || filter(p) {
out = append(out, p)
}
}
if err := s.Err(); err != nil {
return nil, err
}
return out, nil
}
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