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package server
import (
"sync"
"time"
gossh "golang.org/x/crypto/ssh"
)
const (
defaultAuthKeyTTL = 24 * time.Hour
defaultAuthKeyMaxPerUser = 5
)
type authKeyEntry struct {
pubKey gossh.PublicKey
registeredAt time.Time
}
var authKeyStore = NewAuthKeyStore(0, 0)
// AuthKeyStore is an in-memory, per-user cache of SSH public keys.
type AuthKeyStore struct {
mu sync.RWMutex
keysByUser map[string][]authKeyEntry
ttl time.Duration
maxKeysPerUser int
now func() time.Time
}
// AuthKeys returns the process-wide auth key cache used by the SSH server.
func AuthKeys() *AuthKeyStore {
return authKeyStore
}
// ConfigureAuthKeyStore reinitializes the process-wide auth key cache using config values.
func ConfigureAuthKeyStore(authKeyTTLSeconds, authKeyMaxPerUser int) {
authKeyStore = NewAuthKeyStore(time.Duration(authKeyTTLSeconds)*time.Second, authKeyMaxPerUser)
}
// NewAuthKeyStore builds a thread-safe auth key store.
func NewAuthKeyStore(ttl time.Duration, maxKeysPerUser int) *AuthKeyStore {
return newAuthKeyStoreWithClock(ttl, maxKeysPerUser, time.Now)
}
func newAuthKeyStoreWithClock(ttl time.Duration, maxKeysPerUser int,
nowFn func() time.Time) *AuthKeyStore {
if ttl <= 0 {
ttl = defaultAuthKeyTTL
}
if maxKeysPerUser <= 0 {
maxKeysPerUser = defaultAuthKeyMaxPerUser
}
if nowFn == nil {
nowFn = time.Now
}
return &AuthKeyStore{
keysByUser: make(map[string][]authKeyEntry),
ttl: ttl,
maxKeysPerUser: maxKeysPerUser,
now: nowFn,
}
}
// Add stores or refreshes a key for a user.
func (s *AuthKeyStore) Add(user string, pubKey gossh.PublicKey) {
if user == "" || pubKey == nil {
return
}
now := s.now()
offeredKey := marshalKey(pubKey)
s.mu.Lock()
defer s.mu.Unlock()
userEntries := s.pruneExpiredLocked(user, now)
newEntries := make([]authKeyEntry, 0, len(userEntries)+1)
for _, entry := range userEntries {
if marshalKey(entry.pubKey) == offeredKey {
continue
}
newEntries = append(newEntries, entry)
}
newEntries = append(newEntries, authKeyEntry{
pubKey: pubKey,
registeredAt: now,
})
if len(newEntries) > s.maxKeysPerUser {
newEntries = newEntries[len(newEntries)-s.maxKeysPerUser:]
}
s.keysByUser[user] = newEntries
}
// Has returns true if a non-expired key exists for a user.
func (s *AuthKeyStore) Has(user string, pubKey gossh.PublicKey) bool {
if user == "" || pubKey == nil {
return false
}
now := s.now()
offeredKey := marshalKey(pubKey)
s.mu.Lock()
defer s.mu.Unlock()
userEntries := s.pruneExpiredLocked(user, now)
for _, entry := range userEntries {
if marshalKey(entry.pubKey) == offeredKey {
return true
}
}
return false
}
// Remove deletes a key for a user if it exists.
func (s *AuthKeyStore) Remove(user string, pubKey gossh.PublicKey) {
if user == "" || pubKey == nil {
return
}
offeredKey := marshalKey(pubKey)
s.mu.Lock()
defer s.mu.Unlock()
userEntries := s.pruneExpiredLocked(user, s.now())
if len(userEntries) == 0 {
return
}
remaining := make([]authKeyEntry, 0, len(userEntries))
for _, entry := range userEntries {
if marshalKey(entry.pubKey) == offeredKey {
continue
}
remaining = append(remaining, entry)
}
if len(remaining) == 0 {
delete(s.keysByUser, user)
return
}
s.keysByUser[user] = remaining
}
func (s *AuthKeyStore) pruneExpiredLocked(user string, now time.Time) []authKeyEntry {
userEntries, ok := s.keysByUser[user]
if !ok || len(userEntries) == 0 {
delete(s.keysByUser, user)
return nil
}
hasExpiredEntries := false
for _, entry := range userEntries {
if s.expired(entry, now) {
hasExpiredEntries = true
break
}
}
if !hasExpiredEntries {
return userEntries
}
activeEntries := make([]authKeyEntry, 0, len(userEntries))
for _, entry := range userEntries {
if s.expired(entry, now) {
continue
}
activeEntries = append(activeEntries, entry)
}
if len(activeEntries) == 0 {
delete(s.keysByUser, user)
return nil
}
s.keysByUser[user] = activeEntries
return activeEntries
}
func (s *AuthKeyStore) expired(entry authKeyEntry, now time.Time) bool {
return !entry.registeredAt.Add(s.ttl).After(now)
}
func marshalKey(pubKey gossh.PublicKey) string {
return string(pubKey.Marshal())
}
|
