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/*
* Copyright (c) 2017-2018 Samsung Electronics Co., Ltd All Rights Reserved
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License
*/
package dryad
import (
"crypto/rand"
"crypto/rsa"
"os"
"path"
"strconv"
"golang.org/x/crypto/ssh"
)
// sizeRSA is a length of the RSA key.
// It is experimentally chosen value as it is the longest key while still being fast to generate.
const sizeRSA = 1024
// installPublicKey marshals and stores key in a proper location to be read by ssh daemon.
func installPublicKey(key ssh.PublicKey, homedir, uid, gid string) error {
sshDir := path.Join(homedir, ".ssh")
err := os.MkdirAll(sshDir, 0755)
if err != nil {
return err
}
f, err := os.OpenFile(path.Join(sshDir, "authorized_keys"),
os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
defer f.Close()
err = updateOwnership(f, sshDir, uid, gid)
if err != nil {
return err
}
_, err = f.Write(ssh.MarshalAuthorizedKey(key))
return err
}
// updateOwnership changes the owner of key and sshDir to uid:gid parsed from uidStr and gidStr.
func updateOwnership(key *os.File, sshDir, uidStr, gidStr string) (err error) {
uid, err := strconv.Atoi(uidStr)
if err != nil {
return
}
gid, err := strconv.Atoi(gidStr)
if err != nil {
return
}
err = os.Chown(sshDir, uid, gid)
if err != nil {
return
}
return key.Chown(uid, gid)
}
// generateAndInstallKey generates a new RSA key pair, installs the public part,
// changes its owner, and returns the private part.
func generateAndInstallKey(homedir, uid, gid string) (*rsa.PrivateKey, error) {
key, err := rsa.GenerateKey(rand.Reader, sizeRSA)
if err != nil {
return nil, err
}
sshPubKey, err := ssh.NewPublicKey(&key.PublicKey)
if err != nil {
return nil, err
}
err = installPublicKey(sshPubKey, homedir, uid, gid)
if err != nil {
return nil, err
}
return key, nil
}
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