/
authorisedkeys.go
353 lines (328 loc) · 9.33 KB
/
authorisedkeys.go
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// Copyright 2013 Canonical Ltd.
// Licensed under the LGPLv3, see LICENCE file for details.
package ssh
import (
"fmt"
"io/ioutil"
"os"
"os/user"
"path/filepath"
"runtime"
"strconv"
"strings"
"sync"
"github.com/juju/errors"
"github.com/juju/loggo"
"github.com/juju/utils/v3"
"golang.org/x/crypto/ssh"
)
var logger = loggo.GetLogger("juju.utils.ssh")
type ListMode bool
var (
FullKeys ListMode = true
Fingerprints ListMode = false
)
const (
authKeysFile = "authorized_keys"
)
type AuthorisedKey struct {
Type string
Key []byte
Comment string
}
func authKeysDir(username string) (string, error) {
homeDir, err := utils.UserHomeDir(username)
if err != nil {
return "", err
}
homeDir, err = utils.NormalizePath(homeDir)
if err != nil {
return "", err
}
return filepath.Join(homeDir, ".ssh"), nil
}
// ParseAuthorisedKey parses a non-comment line from an
// authorized_keys file and returns the constituent parts.
// Based on description in "man sshd".
func ParseAuthorisedKey(line string) (*AuthorisedKey, error) {
if strings.Contains(line, "\n") {
return nil, errors.NotValidf("newline in authorized_key %q", line)
}
key, comment, _, _, err := ssh.ParseAuthorizedKey([]byte(line))
if err != nil {
return nil, errors.Errorf("invalid authorized_key %q", line)
}
return &AuthorisedKey{
Type: key.Type(),
Key: key.Marshal(),
Comment: comment,
}, nil
}
// ConcatAuthorisedKeys will joing two or more authorised keys together to form
// a string based list of authorised keys that can be read by ssh programs. Keys
// joined with a newline as the separator.
func ConcatAuthorisedKeys(a, b string) string {
if a == "" {
return b
}
if b == "" {
return a
}
if a[len(a)-1] != '\n' {
return a + "\n" + b
}
return a + b
}
// SplitAuthorisedKeys extracts a key slice from the specified key data,
// by splitting the key data into lines and ignoring comments and blank lines.
func SplitAuthorisedKeys(keyData string) []string {
var keys []string
for _, key := range strings.Split(string(keyData), "\n") {
key = strings.Trim(key, " \r")
if len(key) == 0 {
continue
}
if key[0] == '#' {
continue
}
keys = append(keys, key)
}
return keys
}
func readAuthorisedKeys(username string) ([]string, error) {
keyDir, err := authKeysDir(username)
if err != nil {
return nil, err
}
sshKeyFile := filepath.Join(keyDir, authKeysFile)
logger.Debugf("reading authorised keys file %s", sshKeyFile)
keyData, err := ioutil.ReadFile(sshKeyFile)
if os.IsNotExist(err) {
return []string{}, nil
}
if err != nil {
return nil, errors.Annotate(err, "reading ssh authorised keys file")
}
var keys []string
for _, key := range strings.Split(string(keyData), "\n") {
if len(strings.Trim(key, " \r")) == 0 {
continue
}
keys = append(keys, key)
}
return keys, nil
}
func writeAuthorisedKeys(username string, keys []string) error {
keyDir, err := authKeysDir(username)
if err != nil {
return err
}
err = os.MkdirAll(keyDir, os.FileMode(0755))
if err != nil {
return errors.Annotate(err, "cannot create ssh key directory")
}
keyData := strings.Join(keys, "\n") + "\n"
// Get perms to use on auth keys file
sshKeyFile := filepath.Join(keyDir, authKeysFile)
perms := os.FileMode(0644)
info, err := os.Stat(sshKeyFile)
if err == nil {
perms = info.Mode().Perm()
}
logger.Debugf("writing authorised keys file %s", sshKeyFile)
err = utils.AtomicWriteFile(sshKeyFile, []byte(keyData), perms)
if err != nil {
return err
}
// TODO (wallyworld) - what to do on windows (if anything)
// TODO(dimitern) - no need to use user.Current() if username
// is "" - it will use the current user anyway.
if runtime.GOOS != "windows" {
// Ensure the resulting authorised keys file has its ownership
// set to the specified username.
var u *user.User
if username == "" {
u, err = user.Current()
} else {
u, err = user.Lookup(username)
}
if err != nil {
return err
}
// chown requires ints but user.User has strings for windows.
uid, err := strconv.Atoi(u.Uid)
if err != nil {
return err
}
gid, err := strconv.Atoi(u.Gid)
if err != nil {
return err
}
err = os.Chown(sshKeyFile, uid, gid)
if err != nil {
return err
}
}
return nil
}
// We need a mutex because updates to the authorised keys file are done by
// reading the contents, updating, and writing back out. So only one caller
// at a time can use either Add, Delete, List.
var keysMutex sync.Mutex
// AddKeys adds the specified ssh keys to the authorized_keys file for user.
// Returns an error if there is an issue with *any* of the supplied keys.
func AddKeys(user string, newKeys ...string) error {
keysMutex.Lock()
defer keysMutex.Unlock()
existingKeys, err := readAuthorisedKeys(user)
if err != nil {
return err
}
for _, newKey := range newKeys {
fingerprint, comment, err := KeyFingerprint(newKey)
if err != nil {
return err
}
if comment == "" {
return errors.Errorf("cannot add ssh key without comment")
}
for _, key := range existingKeys {
existingFingerprint, existingComment, err := KeyFingerprint(key)
if err != nil {
// Only log a warning if the unrecognised key line is not a comment.
if key[0] != '#' {
logger.Warningf("invalid existing ssh key %q: %v", key, err)
}
continue
}
if existingFingerprint == fingerprint {
return errors.Errorf("cannot add duplicate ssh key: %v", fingerprint)
}
if existingComment == comment {
return errors.Errorf("cannot add ssh key with duplicate comment: %v", comment)
}
}
}
sshKeys := append(existingKeys, newKeys...)
return writeAuthorisedKeys(user, sshKeys)
}
// DeleteKeys removes the specified ssh keys from the authorized ssh keys file for user.
// keyIds may be either key comments or fingerprints.
// Returns an error if there is an issue with *any* of the keys to delete.
func DeleteKeys(user string, keyIds ...string) error {
keysMutex.Lock()
defer keysMutex.Unlock()
existingKeyData, err := readAuthorisedKeys(user)
if err != nil {
return err
}
// Build up a map of keys indexed by fingerprint, and fingerprints indexed by comment
// so we can easily get the key represented by each keyId, which may be either a fingerprint
// or comment.
var keysToWrite []string
var sshKeys = make(map[string]string)
var keyComments = make(map[string]string)
for _, key := range existingKeyData {
fingerprint, comment, err := KeyFingerprint(key)
if err != nil {
logger.Debugf("keeping unrecognised existing ssh key %q: %v", key, err)
keysToWrite = append(keysToWrite, key)
continue
}
sshKeys[fingerprint] = key
if comment != "" {
keyComments[comment] = fingerprint
}
}
for _, keyId := range keyIds {
// assume keyId may be a fingerprint
fingerprint := keyId
_, ok := sshKeys[keyId]
if !ok {
// keyId is a comment
fingerprint, ok = keyComments[keyId]
}
if !ok {
return errors.Errorf("cannot delete non existent key: %v", keyId)
}
delete(sshKeys, fingerprint)
}
for _, key := range sshKeys {
keysToWrite = append(keysToWrite, key)
}
if len(keysToWrite) == 0 {
return errors.Errorf("cannot delete all keys")
}
return writeAuthorisedKeys(user, keysToWrite)
}
// ReplaceKeys writes the specified ssh keys to the authorized_keys file for user,
// replacing any that are already there.
// Returns an error if there is an issue with *any* of the supplied keys.
func ReplaceKeys(user string, newKeys ...string) error {
keysMutex.Lock()
defer keysMutex.Unlock()
existingKeyData, err := readAuthorisedKeys(user)
if err != nil {
return err
}
var existingNonKeyLines []string
for _, line := range existingKeyData {
_, _, err := KeyFingerprint(line)
if err != nil {
existingNonKeyLines = append(existingNonKeyLines, line)
}
}
return writeAuthorisedKeys(user, append(existingNonKeyLines, newKeys...))
}
// ListKeys returns either the full keys or key comments from the authorized ssh keys file for user.
func ListKeys(user string, mode ListMode) ([]string, error) {
keysMutex.Lock()
defer keysMutex.Unlock()
keyData, err := readAuthorisedKeys(user)
if err != nil {
return nil, err
}
var keys []string
for _, key := range keyData {
fingerprint, comment, err := KeyFingerprint(key)
if err != nil {
// Only log a warning if the unrecognised key line is not a comment.
if key[0] != '#' {
logger.Warningf("ignoring invalid ssh key %q: %v", key, err)
}
continue
}
if mode == FullKeys {
keys = append(keys, key)
} else {
shortKey := fingerprint
if comment != "" {
shortKey += fmt.Sprintf(" (%s)", comment)
}
keys = append(keys, shortKey)
}
}
return keys, nil
}
// Any ssh key added to the authorised keys list by Juju will have this prefix.
// This allows Juju to know which keys have been added externally and any such keys
// will always be retained by Juju when updating the authorised keys file.
const JujuCommentPrefix = "Juju:"
func EnsureJujuComment(key string) string {
ak, err := ParseAuthorisedKey(key)
// Just return an invalid key as is.
if err != nil {
logger.Warningf("invalid Juju ssh key %s: %v", key, err)
return key
}
if ak.Comment == "" {
return key + " " + JujuCommentPrefix + "sshkey"
} else {
// Add the Juju prefix to the comment if necessary.
if !strings.HasPrefix(ak.Comment, JujuCommentPrefix) {
commentIndex := strings.LastIndex(key, ak.Comment)
return key[:commentIndex] + JujuCommentPrefix + ak.Comment
}
}
return key
}