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user_ek_box_storage.go
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user_ek_box_storage.go
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package ephemeral
import (
"fmt"
"sort"
"sync"
"time"
"github.com/keybase/client/go/libkb"
"github.com/keybase/client/go/protocol/gregor1"
"github.com/keybase/client/go/protocol/keybase1"
)
const userEKBoxStorageDBVersion = 4
type userEKBoxCacheItem struct {
UserEKBoxed keybase1.UserEkBoxed
Err *EphemeralKeyError
}
func newUserEKBoxCacheItem(userEKBoxed keybase1.UserEkBoxed, err error) userEKBoxCacheItem {
var ekErr *EphemeralKeyError
e, ok := err.(EphemeralKeyError)
if !ok && err != nil {
e = newEphemeralKeyError(err.Error(), DefaultHumanErrMsg,
EphemeralKeyErrorKindUNKNOWN, UserEKKind)
}
if err != nil {
ekErr = &e
}
return userEKBoxCacheItem{
UserEKBoxed: userEKBoxed,
Err: ekErr,
}
}
func (c userEKBoxCacheItem) HasError() bool {
return c.Err != nil
}
func (c userEKBoxCacheItem) Error() error {
if c.HasError() {
return *c.Err
}
return nil
}
type userEKBoxCache map[keybase1.EkGeneration]userEKBoxCacheItem
type UserEKBoxMap map[keybase1.EkGeneration]keybase1.UserEkBoxed
type UserEKUnboxedMap map[keybase1.EkGeneration]keybase1.UserEk
// We cache UserEKBoxes from the server in memory and a persist to a local
// KVStore.
type UserEKBoxStorage struct {
sync.Mutex
indexed bool
cache userEKBoxCache
}
func NewUserEKBoxStorage() *UserEKBoxStorage {
return &UserEKBoxStorage{
cache: make(userEKBoxCache),
}
}
func (s *UserEKBoxStorage) dbKey(mctx libkb.MetaContext) (dbKey libkb.DbKey, err error) {
uv, err := mctx.G().GetMeUV(mctx.Ctx())
if err != nil {
return dbKey, err
}
key := fmt.Sprintf("userEphemeralKeyBox-%s-%s-%d", mctx.G().Env.GetUsername(), uv.EldestSeqno, userEKBoxStorageDBVersion)
return libkb.DbKey{
Typ: libkb.DBUserEKBox,
Key: key,
}, nil
}
func (s *UserEKBoxStorage) getCache(mctx libkb.MetaContext) (cache userEKBoxCache, err error) {
if !s.indexed {
key, err := s.dbKey(mctx)
if err != nil {
return s.cache, err
}
if _, err = mctx.G().GetKVStore().GetInto(&s.cache, key); err != nil {
return s.cache, err
}
s.indexed = true
}
return s.cache, nil
}
func (s *UserEKBoxStorage) Get(mctx libkb.MetaContext, generation keybase1.EkGeneration,
contentCtime *gregor1.Time) (userEK keybase1.UserEk, err error) {
defer mctx.Trace(fmt.Sprintf("UserEKBoxStorage#Get: generation:%v", generation), &err)()
s.Lock()
cache, err := s.getCache(mctx)
if err != nil {
s.Unlock()
return userEK, err
}
// Try cache first
cacheItem, ok := cache[generation]
if !ok {
// We don't have anything in our cache, fetch from the server
s.Unlock() // release the lock while we fetch
return s.fetchAndStore(mctx, generation)
}
defer s.Unlock() // release the lock after we unbox
if cacheItem.HasError() {
return userEK, cacheItem.Error()
}
userEK, err = s.unbox(mctx, generation, cacheItem.UserEKBoxed, contentCtime)
switch err.(type) {
case EphemeralKeyError: // if we can no longer unbox this, store the error
if perr := s.putLocked(mctx, generation, keybase1.UserEkBoxed{}, err); perr != nil {
mctx.Debug("unable to store unboxing error %v", perr)
}
default:
// don't store
}
return userEK, err
}
type UserEKBoxedResponse struct {
Result *struct {
Box string `json:"box"`
DeviceEKGeneration keybase1.EkGeneration `json:"device_ek_generation"`
Sig string `json:"sig"`
} `json:"result"`
}
func (s *UserEKBoxStorage) fetchAndStore(mctx libkb.MetaContext, generation keybase1.EkGeneration) (userEK keybase1.UserEk, err error) {
defer mctx.Trace(fmt.Sprintf("UserEKBoxStorage#fetchAndStore: generation: %v", generation), &err)()
// cache unboxing/missing box errors so we don't continually try to fetch
// something nonexistent.
defer func() {
if _, ok := err.(EphemeralKeyError); ok {
s.Lock()
defer s.Unlock()
if perr := s.putLocked(mctx, generation, keybase1.UserEkBoxed{}, err); perr != nil {
mctx.Debug("unable to store error %v", perr)
}
}
}()
apiArg := libkb.APIArg{
Endpoint: "user/user_ek_box",
SessionType: libkb.APISessionTypeREQUIRED,
Args: libkb.HTTPArgs{
"generation": libkb.U{Val: uint64(generation)},
"recipient_device_id": libkb.S{Val: string(mctx.ActiveDevice().DeviceID())},
},
}
var result UserEKBoxedResponse
res, err := mctx.G().GetAPI().Get(mctx, apiArg)
if err != nil {
err = errFromAppStatus(err)
return userEK, err
}
if err = res.Body.UnmarshalAgain(&result); err != nil {
return userEK, err
}
if result.Result == nil {
err = newEKMissingBoxErr(mctx, UserEKKind, generation)
return userEK, err
}
// Although we verify the signature is valid, it's possible that this key
// was signed with a PUK that is not our latest and greatest. We allow this
// when we are using this ek for *decryption*. When getting a key for
// *encryption* callers are responsible for verifying the signature is
// signed by the latest PUK or generating a new EK. This logic currently
// lives in ephemeral/lib.go#KeygenIfNeeded (#newUserEKNeeded)
_, userEKStatement, err := extractUserEKStatementFromSig(result.Result.Sig)
if err != nil {
return userEK, err
} else if userEKStatement == nil { // shouldn't happen
return userEK, fmt.Errorf("unable to fetch valid userEKStatement")
}
userEKMetadata := userEKStatement.CurrentUserEkMetadata
if generation != userEKMetadata.Generation {
// sanity check that we got the right generation
return userEK, newEKCorruptedErr(mctx, UserEKKind, generation, userEKMetadata.Generation)
}
userEKBoxed := keybase1.UserEkBoxed{
Box: result.Result.Box,
DeviceEkGeneration: result.Result.DeviceEKGeneration,
Metadata: userEKMetadata,
}
userEK, err = s.unbox(mctx, generation, userEKBoxed, nil)
if err != nil {
return userEK, err
}
seed := UserEKSeed(userEK.Seed)
keypair := seed.DeriveDHKey()
if !keypair.GetKID().Equal(userEKMetadata.Kid) {
return userEK, fmt.Errorf("Failed to verify server given seed [%s] against signed KID [%s]. Box %+v",
userEKMetadata.Kid, keypair.GetKID(), userEKBoxed)
}
// Store the boxed version, return the unboxed
err = s.Put(mctx, generation, userEKBoxed)
return userEK, err
}
func (s *UserEKBoxStorage) Put(mctx libkb.MetaContext, generation keybase1.EkGeneration, userEKBoxed keybase1.UserEkBoxed) (err error) {
s.Lock()
defer s.Unlock()
return s.putLocked(mctx, generation, userEKBoxed, nil /* ekErr */)
}
func (s *UserEKBoxStorage) putLocked(mctx libkb.MetaContext, generation keybase1.EkGeneration,
userEKBoxed keybase1.UserEkBoxed, ekErr error) (err error) {
defer mctx.Trace(fmt.Sprintf("UserEKBoxStorage#putLocked: generation:%v", generation), &err)()
// sanity check that we got the right generation
if userEKBoxed.Metadata.Generation != generation && ekErr == nil {
return newEKCorruptedErr(mctx, UserEKKind, generation, userEKBoxed.Metadata.Generation)
}
key, err := s.dbKey(mctx)
if err != nil {
return err
}
cache, err := s.getCache(mctx)
if err != nil {
return err
}
cache[generation] = newUserEKBoxCacheItem(userEKBoxed, ekErr)
return mctx.G().GetKVStore().PutObj(key, nil, cache)
}
func (s *UserEKBoxStorage) unbox(mctx libkb.MetaContext, userEKGeneration keybase1.EkGeneration,
userEKBoxed keybase1.UserEkBoxed, contentCtime *gregor1.Time) (userEK keybase1.UserEk, err error) {
defer mctx.Trace(fmt.Sprintf("UserEKBoxStorage#unbox: generation:%v", userEKGeneration), &err)()
deviceEKStorage := mctx.G().GetDeviceEKStorage()
deviceEK, err := deviceEKStorage.Get(mctx, userEKBoxed.DeviceEkGeneration)
if err != nil {
mctx.Debug("unable to get from deviceEKStorage %v", err)
if _, ok := err.(libkb.UnboxError); ok {
return userEK, newEKUnboxErr(mctx, UserEKKind, userEKGeneration, DeviceEKKind,
userEKBoxed.DeviceEkGeneration, contentCtime)
}
return userEK, err
}
deviceSeed := DeviceEKSeed(deviceEK.Seed)
deviceKeypair := deviceSeed.DeriveDHKey()
msg, _, err := deviceKeypair.DecryptFromString(userEKBoxed.Box)
if err != nil {
mctx.Debug("unable to decrypt userEKBoxed %v", err)
return userEK, newEKUnboxErr(mctx, UserEKKind, userEKGeneration, DeviceEKKind,
userEKBoxed.DeviceEkGeneration, contentCtime)
}
seed, err := newUserEKSeedFromBytes(msg)
if err != nil {
return userEK, err
}
return keybase1.UserEk{
Seed: keybase1.Bytes32(seed),
Metadata: userEKBoxed.Metadata,
}, nil
}
func (s *UserEKBoxStorage) Delete(mctx libkb.MetaContext, generation keybase1.EkGeneration) (err error) {
s.Lock()
defer s.Unlock()
return s.deleteMany(mctx, []keybase1.EkGeneration{generation})
}
func (s *UserEKBoxStorage) deleteMany(mctx libkb.MetaContext, generations []keybase1.EkGeneration) (err error) {
defer mctx.Trace(fmt.Sprintf("UserEKBoxStorage#deleteMany: generations:%v", generations), &err)()
cache, err := s.getCache(mctx)
if err != nil {
return err
}
for _, generation := range generations {
delete(cache, generation)
}
key, err := s.dbKey(mctx)
if err != nil {
return err
}
return mctx.G().GetKVStore().PutObj(key, nil, cache)
}
func (s *UserEKBoxStorage) GetAll(mctx libkb.MetaContext) (userEKs UserEKUnboxedMap, err error) {
defer mctx.Trace("UserEKBoxStorage#GetAll", &err)()
s.Lock()
defer s.Unlock()
cache, err := s.getCache(mctx)
if err != nil {
return userEKs, err
}
userEKs = make(UserEKUnboxedMap)
for generation, cacheItem := range cache {
if cacheItem.HasError() {
continue
}
userEK, err := s.unbox(mctx, generation, cacheItem.UserEKBoxed, nil)
if err != nil {
return userEKs, err
}
userEKs[generation] = userEK
}
return userEKs, err
}
func (s *UserEKBoxStorage) ClearCache() {
s.Lock()
defer s.Unlock()
s.cache = make(userEKBoxCache)
s.indexed = false
}
func (s *UserEKBoxStorage) MaxGeneration(mctx libkb.MetaContext, includeErrs bool) (maxGeneration keybase1.EkGeneration, err error) {
defer mctx.Trace("UserEKBoxStorage#MaxGeneration", &err)()
s.Lock()
defer s.Unlock()
maxGeneration = -1
cache, err := s.getCache(mctx)
if err != nil {
return maxGeneration, err
}
for generation, cacheItem := range cache {
if cacheItem.HasError() && !includeErrs {
continue
}
if generation > maxGeneration {
maxGeneration = generation
}
}
return maxGeneration, nil
}
func (s *UserEKBoxStorage) DeleteExpired(mctx libkb.MetaContext, merkleRoot libkb.MerkleRoot) (expired []keybase1.EkGeneration, err error) {
defer mctx.Trace("DeviceEKStorage#DeleteExpired", &err)()
s.Lock()
defer s.Unlock()
cache, err := s.getCache(mctx)
if err != nil {
return nil, err
}
keyMap := make(keyExpiryMap)
// We delete expired and invalid cache entries but only return the expired.
toDelete := []keybase1.EkGeneration{}
for generation, cacheItem := range cache {
// purge any cached errors here so they don't stick around forever.
if cacheItem.HasError() {
toDelete = append(toDelete, generation)
} else {
keyMap[generation] = cacheItem.UserEKBoxed.Metadata.Ctime
}
}
now := keybase1.TimeFromSeconds(merkleRoot.Ctime()).Time()
expired = s.getExpiredGenerations(mctx, keyMap, now)
toDelete = append(toDelete, expired...)
return expired, s.deleteMany(mctx, toDelete)
}
// getExpiredGenerations calculates which keys have expired and are safe to
// delete. Keys normally expire after `libkb.MaxEphemeralContentLifetime`
// unless there has been a gap in their generation. If there has been a gap of
// more than a day (the normal generation time), a key can be re-used for up to
// `libkb.MaxEphemeralKeyStaleness` until it is considered expired. To
// determine expiration, we look at all of the current keys and account for any
// gaps since we don't want to expire a key if it is still used to encrypt a
// different key or ephemeral content.
func (s *UserEKBoxStorage) getExpiredGenerations(mctx libkb.MetaContext, keyMap keyExpiryMap, now time.Time) (expired []keybase1.EkGeneration) {
// Sort the generations we have so we can walk through them in order.
var keys []keybase1.EkGeneration
for k := range keyMap {
keys = append(keys, k)
}
sort.Slice(keys, func(i, j int) bool { return keys[i] < keys[j] })
for i, generation := range keys {
keyCtime := keyMap[generation].Time()
expiryOffset := libkb.MaxEphemeralKeyStaleness
if i < len(keys)-1 {
expiryOffset = keyMap[keys[i+1]].Time().Sub(keyCtime)
// Offset can be max libkb.MaxEphemeralKeyStaleness
if expiryOffset > libkb.MaxEphemeralKeyStaleness {
expiryOffset = libkb.MaxEphemeralKeyStaleness
}
}
if now.Sub(keyCtime) >= (libkb.MinEphemeralKeyLifetime + expiryOffset) {
mctx.Debug("getExpiredGenerations: expired generation:%v, now: %v, keyCtime:%v, expiryOffset:%v, keyMap: %v, i:%v, %v, %v",
generation, now, keyCtime, expiryOffset, keyMap, i, now.Sub(keyCtime), (libkb.MinEphemeralKeyLifetime + expiryOffset))
expired = append(expired, generation)
}
}
return expired
}