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credential_authority.go
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credential_authority.go
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package auth
import (
libkb "github.com/keybase/client/go/libkb"
logger "github.com/keybase/client/go/logger"
keybase1 "github.com/keybase/client/go/protocol"
context "golang.org/x/net/context"
"time"
)
const (
userTimeout = 5 * time.Minute
cacheTimeout = 8 * time.Minute
)
// CredentialAuthority should be allocated as a singleton object. It validates UID<->Username<->ActiveKey
// triples for all users across a service. It keeps a cache and subscribes for updates,
// so you can call into it as much as you'd like without fear of spamming the network.
type CredentialAuthority struct {
log logger.Logger
api UserKeyAPIer
invalidateCh chan keybase1.UID
checkCh chan checkArg
shutdownCh chan struct{}
cleanItemCh chan cleanItem
users map[keybase1.UID](*userWrapper)
cleanSchedule []cleanItem
eng engine
}
// checkArgs are sent over the checkCh to the core loop of a CredentialAuthority
type checkArg struct {
uid keybase1.UID
username libkb.NormalizedUsername
kid keybase1.KID
retCh chan error
}
// userWrapper contains two fields -- one is the user object itself, which will
// spawn a go-routine that is largely off-limits to the main thread aside from
// over channels. the second field is the `atime`, or *access* time, which the main
// thread can touch to compute eviction mechanics.
type userWrapper struct {
u *user
atime time.Time
}
// cleanItems are items to consider cleaning out of the cache. they sit in a queue
// until they are up for review. When the review happens, the user object they
// refer to can still persist in the cache, if it's been accessed recently.
type cleanItem struct {
uid keybase1.UID
ctime time.Time
}
// user wraps a user who is currently active in the system. Each user has a run
// method that runs its own goRoutine, so many items, aside from the two channels,
// are off-limits to the main thread.
type user struct {
uid keybase1.UID
username libkb.NormalizedUsername
keys map[keybase1.KID]struct{}
isOK bool
ctime time.Time
ca *CredentialAuthority
checkCh chan checkArg
stopCh chan struct{}
}
// newUser makes a new user with the given UID for use in the given
// CredentialAuthority. This constructor sets up the necessary maps and
// channels to make the user work as expected.
func newUser(uid keybase1.UID, ca *CredentialAuthority) *user {
ret := &user{
uid: uid,
keys: make(map[keybase1.KID]struct{}),
ca: ca,
checkCh: make(chan checkArg),
stopCh: make(chan struct{}),
}
go ret.run()
return ret
}
// UserKeyAPIer is an interface that specifies the UserKeyAPI that
// will eventually be used to get information about the users from the trusted
// server authority.
type UserKeyAPIer interface {
// GetUser looks up the username and KIDS active for the given user.
GetUser(context.Context, keybase1.UID) (libkb.NormalizedUsername, []keybase1.KID, error)
// PollForChanges returns the UIDs that have recently changed on the server
// side. It will be called in a poll loop.
PollForChanges(context.Context) ([]keybase1.UID, error)
}
// engine specifies the internal mechanics of how this CredentialAuthority
// works. It's only really useful for testing, since tests will want to change
// the definition of time, poke the main loop into action at certain points,
// and get callback hooks when items are evicted.
type engine interface {
Now() time.Time // we can overload this for debugging
Evicted(uid keybase1.UID) // called when this uid is evicted
GetPokeCh() <-chan struct{} // Return a channel that can poke the main loop
}
// standardEngine is the engine that's used in production when the CredentailAuthority
// actually runs. It does very little.
type standardEngine struct {
pokeCh <-chan struct{}
}
// Now returns time.Now
func (se *standardEngine) Now() time.Time { return time.Now() }
// Evicted is a Noop, called whenever a user object for the given UID is evicted.
func (se *standardEngine) Evicted(uid keybase1.UID) {}
// GetPokeCh returns a dummy channel that's never sent to
func (se *standardEngine) GetPokeCh() <-chan struct{} { return se.pokeCh }
// newStandardEngine creates and initializes a standardEngine for use in the
// production run of a CredentialAuthority.
func newStandardEngine() engine {
return &standardEngine{
pokeCh: make(chan struct{}),
}
}
// NewCredentialAuthority makes a new signleton CredentialAuthority an start it running. It takes as input
// a logger and an API for making keybase API calls
func NewCredentialAuthority(log logger.Logger, api UserKeyAPIer) *CredentialAuthority {
return newCredentialAuthorityWithEngine(log, api, newStandardEngine())
}
// newCredentialAuthoirutyWithEngine is an internal call that can specify the non-standard
// engine. We'd only need to call this directly from testing to specify a testingEngine.
func newCredentialAuthorityWithEngine(log logger.Logger, api UserKeyAPIer, eng engine) *CredentialAuthority {
ret := &CredentialAuthority{
log: log,
api: api,
invalidateCh: make(chan keybase1.UID, 100),
checkCh: make(chan checkArg),
shutdownCh: make(chan struct{}),
users: make(map[keybase1.UID](*userWrapper)),
cleanItemCh: make(chan cleanItem),
eng: eng,
}
ret.run()
return ret
}
// run two loops in goroutines: one to poll for updates from the server, and
// another to poll for incoming requests and maintenance events.
func (v *CredentialAuthority) run() {
go v.pollLoop()
go v.runLoop()
}
// pollOnce polls the API server once for which users have changed.
func (v *CredentialAuthority) pollOnce() error {
var err error
var uids []keybase1.UID
err = v.runWithCancel(func(ctx context.Context) error {
var err error
uids, err = v.api.PollForChanges(ctx)
return err
})
if err == nil {
for _, uid := range uids {
v.invalidateCh <- uid
}
}
return err
}
// runWithCancel runs an API call while listening for a shutdown of the CredentialAuthority.
// If it gets one, it uses context-based cancelation to cancel the outstanding API call
// (or sleep in the case of Poll()'ing).
func (v *CredentialAuthority) runWithCancel(body func(ctx context.Context) error) error {
ctx, cancel := context.WithCancel(context.Background())
doneCh := make(chan struct{})
var err error
go func() {
err = body(ctx)
doneCh <- struct{}{}
}()
select {
case <-doneCh:
case <-v.shutdownCh:
cancel()
err = ErrShutdown
}
return err
}
// pollLoop() keeps running until the CA is shut down via Shutdown(). It calls Poll()
// on the UserKeyAPIer once per iteration.
func (v *CredentialAuthority) pollLoop() {
var err error
for err != ErrShutdown {
err = v.pollOnce()
}
}
// runLoop() keeps running until the CA is shut down via Shutdown(). It listens
// for incoming client requests, and also for various maintenance takes, and
// cache invalidations.
func (v *CredentialAuthority) runLoop() {
done := false
for !done {
select {
case <-v.eng.GetPokeCh():
// Noop, but poke main loop for testing.
case <-v.shutdownCh:
done = true
case ca := <-v.checkCh:
u := v.makeUser(ca.uid)
go u.sendCheck(ca)
case uid := <-v.invalidateCh:
if uw := v.users[uid]; uw != nil {
delete(v.users, uid)
go uw.u.sendStop()
}
case ci := <-v.cleanItemCh:
v.cleanSchedule = append(v.cleanSchedule, ci)
}
v.clean()
}
}
// clean out in-memory data, going through in FIFO order. Stop once we've hit
// a cleanItem that's too recent. When we iterate over cleanItems, we don't
// need to throw them out necessarily, if they've been accessed recently. In that
// case, just skip and keep going.
//
// We'll get an entry in the cleanSchedule once for ever call to GetUser() on
// the API server.
func (v *CredentialAuthority) clean() {
cutoff := v.eng.Now().Add(-cacheTimeout)
for i, e := range v.cleanSchedule {
if e.ctime.After(cutoff) {
v.cleanSchedule = v.cleanSchedule[i:]
return
}
if uw := v.users[e.uid]; uw != nil && !uw.atime.After(e.ctime) {
delete(v.users, e.uid)
go uw.u.sendStop()
}
}
v.cleanSchedule = nil
}
// makeUser either pulls a user from the in-memory table, or constructs a new
// one. In either case, it updates the CA's `atime` bit for now for this user
// record.
func (v *CredentialAuthority) makeUser(uid keybase1.UID) *user {
uw := v.users[uid]
if uw == nil {
u := newUser(uid, v)
uw = &userWrapper{u: u}
v.users[uid] = uw
}
uw.atime = v.eng.Now()
return uw.u
}
// sendCheck sends a message to the user object that it should check the given
// user.
func (u *user) sendCheck(ca checkArg) {
u.checkCh <- ca
}
// sendStop sends a message to a user object that it has been evicted, and
// therefore, that it should stop whatever it's doing and just exit its
// go routine.
func (u *user) sendStop() {
u.stopCh <- struct{}{}
}
// Each user object has its own run() routine. It handles requests for checks,
// requests to stop, or requests to shutdown.
func (u *user) run() {
done := false
for !done {
select {
case ca := <-u.checkCh:
u.check(ca)
case <-u.stopCh:
done = true
case <-u.ca.shutdownCh:
done = true
}
}
u.ca.eng.Evicted(u.uid)
}
// Now return this CA's idea of what time Now is.
func (u user) Now() time.Time { return u.ca.eng.Now() }
// repopulate is intended to repopulate our representation of the user with the
// server's up-to-date notion of what the user looks like. If our version is recent
// enough, this is a no-op. If not, we'll go to the server and send the main loop
// a "Cleanup" event to eventually clean us out.
func (u *user) repopulate() error {
if u.isPopulated() {
return nil
}
// Register that this item should eventually be cleaned out by the cleaner
// thread. Don't block on the send, though, since that could deadlock the process
// (since the process is blocked on sending to us).
ctime := u.Now()
go func() {
u.ca.cleanItemCh <- cleanItem{uid: u.uid, ctime: ctime}
}()
un, keys, err := u.ca.getUserFromServer(u.uid)
if err != nil {
u.isOK = false
return err
}
u.username = un
for _, k := range keys {
u.keys[k] = struct{}{}
}
u.isOK = true
u.ctime = ctime
return nil
}
// isPopulated returned true if this user is populated and current enough to
// trust.
func (u *user) isPopulated() bool {
return u.isOK && u.Now().Sub(u.ctime) <= userTimeout
}
// check that a user matches the given username and has the given key as one of
// its valid keys. This is where the actually work of this whole library happens.
func (u *user) check(ca checkArg) {
var err error
defer func() {
ca.retCh <- err
}()
if err = u.repopulate(); err != nil {
return
}
if err = u.checkUsername(ca.username); err != nil {
return
}
if err = u.checkKey(ca.kid); err != nil {
return
}
return
}
// getUserFromServer runs the UserKeyAPIer GetUser() API call while paying
// attention to any shutdown events that might interrupt it.
func (v *CredentialAuthority) getUserFromServer(uid keybase1.UID) (un libkb.NormalizedUsername, kids []keybase1.KID, err error) {
err = v.runWithCancel(func(ctx context.Context) error {
var err error
un, kids, err = v.api.GetUser(ctx, uid)
return err
})
return un, kids, err
}
// checkUsername checks that a username is a match for this user.
func (u *user) checkUsername(un libkb.NormalizedUsername) error {
var err error
if !u.username.Eq(un) {
err = BadUsernameError{u.username, un}
}
return err
}
// checkKey checks that the given key is still valid for this user.
func (u *user) checkKey(kid keybase1.KID) error {
var err error
if _, ok := u.keys[kid]; !ok {
err = BadKeyError{u.uid, kid}
}
return err
}
// Check is the main point of entry to this library. It takes as input a UID, a
// username and a kid that should refer to a current valid triple, perhaps
// extracted from a signed authentication statement. It returns an error if the
// check fails, and nil otherwise.
func (v *CredentialAuthority) Check(ctx context.Context, uid keybase1.UID, username libkb.NormalizedUsername, kid keybase1.KID) (err error) {
retCh := make(chan error)
v.checkCh <- checkArg{uid: uid, username: username, kid: kid, retCh: retCh}
select {
case <-ctx.Done():
err = ErrCanceled
case err = <-retCh:
}
return err
}
// Shutdown the credentialAuthority and delete all internal state.
func (v *CredentialAuthority) Shutdown() {
close(v.shutdownCh)
}