Add redis lock feature (#1063)

* Add sensible logging flag to default setup for logger

* Add Redis lock

* Fix default value flag for sensitive logging

* Split RefreshSessionIfNeeded in two methods and use Redis lock

* Small adjustments to doc and code

* Remove sensible logging

* Fix method names in ticket.go

* Revert "Fix method names in ticket.go"

This reverts commit 408ba1a1a5.

* Fix methods name in ticket.go

* Remove block in Redis client get

* Increase lock time to 1 second

* Perform retries, if session store is locked

* Reverse if condition, because it should return if session does not have to be refreshed

* Update go.sum

* Update MockStore

* Return error if loading session fails

* Fix and update tests

* Change validSession to session in docs and strings

* Change validSession to session in docs and strings

* Fix docs

* Fix wrong field name

* Fix linting

* Fix imports for linting

* Revert changes except from locking functionality

* Add lock feature on session state

* Update from master

* Remove errors package, because it is not used

* Only pass context instead of request to lock

* Use lock key

* By default use NoOpLock

* Remove debug output

* Update ticket_test.go

* Map internal error to sessions error

* Add ErrLockNotObtained

* Enable lock peek for all redis clients

* Use lock key prefix consistent

* Fix imports

* Use exists method for peek lock

* Fix imports

* Fix imports

* Fix imports

* Remove own Dockerfile

* Fix imports

* Fix tests for ticket and session store

* Fix session store test

* Update pkg/apis/sessions/interfaces.go

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

* Do not wrap lock method

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

* Use errors package for lock constants

* Use better naming for initLock function

* Add comments

* Add session store lock test

* Fix tests

* Fix tests

* Fix tests

* Fix tests

* Add cookies after saving session

* Add mock lock

* Fix imports for mock_lock.go

* Store mock lock for key

* Apply elapsed time on mock lock

* Check if lock is initially applied

* Reuse existing lock

* Test all lock methods

* Update CHANGELOG.md

* Use redis client methods in redis.lock for release an refresh

* Use lock key suffix instead of prefix for lock key

* Add comments for Lock interface

* Update comment for Lock interface

* Update CHANGELOG.md

* Change LockSuffix to const

* Check lock on already loaded session

* Use global var for loadedSession in lock tests

* Use lock instance for refreshing and releasing of lock

* Update possible error type for Refresh

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

pkg/sessions/redis/lock.go

@@ -0,0 +1,84 @@
+package redis
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/bsm/redislock"
+	"github.com/go-redis/redis/v8"
+	"github.com/oauth2-proxy/oauth2-proxy/v7/pkg/apis/sessions"
+)
+
+const LockSuffix = "lock"
+
+type Lock struct {
+	client redis.Cmdable
+	locker *redislock.Client
+	lock   *redislock.Lock
+	key    string
+}
+
+// NewLock instantiate a new lock instance. This will not yet apply a lock on Redis side.
+// For that you have to call Obtain(ctx context.Context, expiration time.Duration)
+func NewLock(client redis.Cmdable, key string) sessions.Lock {
+	return &Lock{
+		client: client,
+		locker: redislock.New(client),
+		key:    key,
+	}
+}
+
+// Obtain obtains a distributed lock on Redis for the configured key.
+func (l *Lock) Obtain(ctx context.Context, expiration time.Duration) error {
+	lock, err := l.locker.Obtain(ctx, l.lockKey(), expiration, nil)
+	if errors.Is(err, redislock.ErrNotObtained) {
+		return sessions.ErrLockNotObtained
+	}
+	if err != nil {
+		return err
+	}
+	l.lock = lock
+	return nil
+}
+
+// Refresh refreshes an already existing lock.
+func (l *Lock) Refresh(ctx context.Context, expiration time.Duration) error {
+	if l.lock == nil {
+		return sessions.ErrNotLocked
+	}
+	err := l.lock.Refresh(ctx, expiration, nil)
+	if errors.Is(err, redislock.ErrNotObtained) {
+		return sessions.ErrNotLocked
+	}
+	return err
+}
+
+// Peek returns true, if the lock is still applied.
+func (l *Lock) Peek(ctx context.Context) (bool, error) {
+	v, err := l.client.Exists(ctx, l.lockKey()).Result()
+	if err != nil {
+		return false, err
+	}
+	if v == 0 {
+		return false, nil
+	}
+	return true, nil
+}
+
+// Release releases the lock on Redis side.
+func (l *Lock) Release(ctx context.Context) error {
+	if l.lock == nil {
+		return sessions.ErrNotLocked
+	}
+	err := l.lock.Release(ctx)
+	if errors.Is(err, redislock.ErrLockNotHeld) {
+		return sessions.ErrNotLocked
+	}
+	return err
+}
+
+func (l *Lock) lockKey() string {
+	return fmt.Sprintf("%s.%s", l.key, LockSuffix)
+}