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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package agent
import (
"bytes"
"crypto/rand"
"crypto/subtle"
"errors"
"fmt"
"sync"
"time"
"golang.org/x/crypto/ssh"
)
type privKey struct {
signer ssh.Signer
comment string
expire *time.Time
}
type keyring struct {
mu sync.Mutex
keys []privKey
locked bool
passphrase []byte
}
var errLocked = errors.New("agent: locked")
// NewKeyring returns an Agent that holds keys in memory. It is safe
// for concurrent use by multiple goroutines.
func NewKeyring() Agent {
return &keyring{}
}
// RemoveAll removes all identities.
func (r *keyring) RemoveAll() error {
r.mu.Lock()
defer r.mu.Unlock()
if r.locked {
return errLocked
}
r.keys = nil
return nil
}
// removeLocked does the actual key removal. The caller must already be holding the
// keyring mutex.
func (r *keyring) removeLocked(want []byte) error {
found := false
for i := 0; i < len(r.keys); {
if bytes.Equal(r.keys[i].signer.PublicKey().Marshal(), want) {
found = true
r.keys[i] = r.keys[len(r.keys)-1]
r.keys = r.keys[:len(r.keys)-1]
continue
} else {
i++
}
}
if !found {
return errors.New("agent: key not found")
}
return nil
}
// Remove removes all identities with the given public key.
func (r *keyring) Remove(key ssh.PublicKey) error {
r.mu.Lock()
defer r.mu.Unlock()
if r.locked {
return errLocked
}
return r.removeLocked(key.Marshal())
}
// Lock locks the agent. Sign and Remove will fail, and List will return an empty list.
func (r *keyring) Lock(passphrase []byte) error {
r.mu.Lock()
defer r.mu.Unlock()
if r.locked {
return errLocked
}
r.locked = true
r.passphrase = passphrase
return nil
}
// Unlock undoes the effect of Lock
func (r *keyring) Unlock(passphrase []byte) error {
r.mu.Lock()
defer r.mu.Unlock()
if !r.locked {
return errors.New("agent: not locked")
}
if len(passphrase) != len(r.passphrase) || 1 != subtle.ConstantTimeCompare(passphrase, r.passphrase) {
return fmt.Errorf("agent: incorrect passphrase")
}
r.locked = false
r.passphrase = nil
return nil
}
// expireKeysLocked removes expired keys from the keyring. If a key was added
// with a lifetimesecs contraint and seconds >= lifetimesecs seconds have
// ellapsed, it is removed. The caller *must* be holding the keyring mutex.
func (r *keyring) expireKeysLocked() {
for _, k := range r.keys {
if k.expire != nil && time.Now().After(*k.expire) {
r.removeLocked(k.signer.PublicKey().Marshal())
}
}
}
// List returns the identities known to the agent.
func (r *keyring) List() ([]*Key, error) {
r.mu.Lock()
defer r.mu.Unlock()
if r.locked {
// section 2.7: locked agents return empty.
return nil, nil
}
r.expireKeysLocked()
var ids []*Key
for _, k := range r.keys {
pub := k.signer.PublicKey()
ids = append(ids, &Key{
Format: pub.Type(),
Blob: pub.Marshal(),
Comment: k.comment})
}
return ids, nil
}
// Insert adds a private key to the keyring. If a certificate
// is given, that certificate is added as public key. Note that
// any constraints given are ignored.
func (r *keyring) Add(key AddedKey) error {
r.mu.Lock()
defer r.mu.Unlock()
if r.locked {
return errLocked
}
signer, err := ssh.NewSignerFromKey(key.PrivateKey)
if err != nil {
return err
}
if cert := key.Certificate; cert != nil {
signer, err = ssh.NewCertSigner(cert, signer)
if err != nil {
return err
}
}
p := privKey{
signer: signer,
comment: key.Comment,
}
if key.LifetimeSecs > 0 {
t := time.Now().Add(time.Duration(key.LifetimeSecs) * time.Second)
p.expire = &t
}
r.keys = append(r.keys, p)
return nil
}
// Sign returns a signature for the data.
func (r *keyring) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) {
r.mu.Lock()
defer r.mu.Unlock()
if r.locked {
return nil, errLocked
}
r.expireKeysLocked()
wanted := key.Marshal()
for _, k := range r.keys {
if bytes.Equal(k.signer.PublicKey().Marshal(), wanted) {
return k.signer.Sign(rand.Reader, data)
}
}
return nil, errors.New("not found")
}
// Signers returns signers for all the known keys.
func (r *keyring) Signers() ([]ssh.Signer, error) {
r.mu.Lock()
defer r.mu.Unlock()
if r.locked {
return nil, errLocked
}
r.expireKeysLocked()
s := make([]ssh.Signer, 0, len(r.keys))
for _, k := range r.keys {
s = append(s, k.signer)
}
return s, nil
}
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