accounts: prevent early drops and zero keys in memory when dropping
Private keys would be locked early if SignLocked was called more than once because the unlockLater was still running. Terminate it properly.
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d6a7332993
commit
3750ec7b7d
@ -53,17 +53,24 @@ type Account struct {
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}
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type AccountManager struct {
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keyStore crypto.KeyStore2
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unlockedKeys map[string]crypto.Key
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unlockTime time.Duration
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mutex sync.RWMutex
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keyStore crypto.KeyStore2
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unlocked map[string]*unlocked
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unlockTime time.Duration
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mutex sync.RWMutex
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}
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type unlocked struct {
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addr []byte
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abort chan struct{}
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*crypto.Key
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}
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func NewAccountManager(keyStore crypto.KeyStore2, unlockTime time.Duration) *AccountManager {
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return &AccountManager{
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keyStore: keyStore,
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unlockedKeys: make(map[string]crypto.Key),
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unlockTime: unlockTime,
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keyStore: keyStore,
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unlocked: make(map[string]*unlocked),
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unlockTime: unlockTime,
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}
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}
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@ -97,9 +104,9 @@ func (am *AccountManager) DeleteAccount(address []byte, auth string) error {
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func (am *AccountManager) Sign(a Account, toSign []byte) (signature []byte, err error) {
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am.mutex.RLock()
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unlockedKey := am.unlockedKeys[string(a.Address)]
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unlockedKey, found := am.unlocked[string(a.Address)]
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am.mutex.RUnlock()
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if unlockedKey.Address == nil {
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if !found {
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return nil, ErrLocked
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}
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signature, err = crypto.Sign(toSign, unlockedKey.PrivateKey)
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@ -111,10 +118,8 @@ func (am *AccountManager) SignLocked(a Account, keyAuth string, toSign []byte) (
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if err != nil {
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return nil, err
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}
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am.mutex.Lock()
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am.unlockedKeys[string(a.Address)] = *key
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am.mutex.Unlock()
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go unlockLater(am, a.Address)
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u := am.addUnlocked(a.Address, key)
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go am.dropLater(u)
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signature, err = crypto.Sign(toSign, key.PrivateKey)
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return signature, err
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}
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@ -143,14 +148,40 @@ func (am *AccountManager) Accounts() ([]Account, error) {
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return accounts, err
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}
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func unlockLater(am *AccountManager, addr []byte) {
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select {
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case <-time.After(am.unlockTime):
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}
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func (am *AccountManager) addUnlocked(addr []byte, key *crypto.Key) *unlocked {
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u := &unlocked{addr: addr, abort: make(chan struct{}), Key: key}
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am.mutex.Lock()
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// TODO: how do we know the key is actually gone from memory?
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delete(am.unlockedKeys, string(addr))
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prev, found := am.unlocked[string(addr)]
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if found {
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// terminate dropLater for this key to avoid unexpected drops.
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close(prev.abort)
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zeroKey(prev.PrivateKey)
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}
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am.unlocked[string(addr)] = u
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am.mutex.Unlock()
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return u
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}
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func (am *AccountManager) dropLater(u *unlocked) {
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t := time.NewTimer(am.unlockTime)
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defer t.Stop()
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select {
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case <-u.abort:
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// just quit
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case <-t.C:
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am.mutex.Lock()
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if am.unlocked[string(u.addr)] == u {
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zeroKey(u.PrivateKey)
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delete(am.unlocked, string(u.addr))
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}
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am.mutex.Unlock()
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}
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}
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// zeroKey zeroes a private key in memory.
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func zeroKey(k *ecdsa.PrivateKey) {
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b := k.D.Bits()
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for i := range b {
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b[i] = 0
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}
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}
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