middleware: added client blacklist/whitelist middlewares

server/store/middleware/client/README.md

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+## Client Blacklisting/Whitelisting Middlewares
+
+This package provides the announce middlewares `client_whitelist` and `client_blacklist` for blacklisting or whitelisting clients for announces.
+
+### `client_blacklist`
+
+The `client_blacklist` middleware uses all clientIDs stored in the `ClientStore` to blacklist, i.e. block announces.
+
+The clientID part of the peerID of an announce is matched against the `ClientStore`, if it's contained within the `ClientStore`, the announce is aborted.
+
+### `client_whitelist`
+
+The `client_whitelist` middleware uses all clientIDs stored in the `ClientStore` to whitelist, i.e. allow announces.
+
+The clientID part of the peerID of an announce is matched against the `ClientStore`, if it's _not_ contained within the `ClientStore`, the announce is aborted.
+
+### Important things to notice
+
+Both middlewares operate on announce requests only.
+
+Both middlewares use the same `ClientStore`.
+It is therefore not advised to have both the `client_blacklist` and the `client_whitelist` middleware running.
+(If you add clientID to the `ClientStore`, it will be used for blacklisting and whitelisting.
+If your store contains no clientIDs, no announces will be blocked by the blacklist, but all announces will be blocked by the whitelist.
+If your store contains all clientIDs, no announces will be blocked by the whitelist, but all announces will be blocked by the blacklist.)

server/store/middleware/client/blacklist.go

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+// Copyright 2016 The Chihaya Authors. All rights reserved.
+// Use of this source code is governed by the BSD 2-Clause license,
+// which can be found in the LICENSE file.
+
+package ip
+
+import (
+	"github.com/chihaya/chihaya"
+	"github.com/chihaya/chihaya/config"
+	"github.com/chihaya/chihaya/server/store"
+	"github.com/chihaya/chihaya/tracker"
+)
+
+func init() {
+	tracker.RegisterAnnounceMiddleware("client_blacklist", blacklistAnnounceClient)
+}
+
+// ErrBlockedClient is returned by an announce middleware if the announcing
+// Client is disallowed.
+var ErrBlockedClient = tracker.ClientError("disallowed client")
+
+// blacklistAnnounceClient provides a middleware that only allows Clients to
+// announce that are not stored in a ClientStore.
+func blacklistAnnounceClient(next tracker.AnnounceHandler) tracker.AnnounceHandler {
+	return func(cfg *config.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) error {
+		blacklisted, err := store.MustGetStore().FindClient(req.PeerID)
+
+		if err != nil {
+			return err
+		} else if blacklisted {
+			return ErrBlockedClient
+		}
+		return next(cfg, req, resp)
+	}
+}

server/store/middleware/client/whitelist.go

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+// Copyright 2016 The Chihaya Authors. All rights reserved.
+// Use of this source code is governed by the BSD 2-Clause license,
+// which can be found in the LICENSE file.
+
+package ip
+
+import (
+	"github.com/chihaya/chihaya"
+	"github.com/chihaya/chihaya/config"
+	"github.com/chihaya/chihaya/server/store"
+	"github.com/chihaya/chihaya/tracker"
+)
+
+func init() {
+	tracker.RegisterAnnounceMiddleware("client_whitelist", whitelistAnnounceClient)
+}
+
+// whitelistAnnounceClient provides a middleware that only allows Clients to
+// announce that are stored in a ClientStore.
+func whitelistAnnounceClient(next tracker.AnnounceHandler) tracker.AnnounceHandler {
+	return func(cfg *config.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) error {
+		whitelisted, err := store.MustGetStore().FindClient(req.PeerID)
+
+		if err != nil {
+			return err
+		} else if !whitelisted {
+			return ErrBlockedClient
+		}
+		return next(cfg, req, resp)
+	}
+}