Merge pull request #8384 from prometheus/beorn7/release-2.24

Merge release-2.24 forward into main branch

CHANGELOG.md

+## 2.24.1 / 2021-01-20
+
+* [ENHANCEMENT] Cache basic authentication results to significantly improve performance of HTTP endpoints (via an update of prometheus/exporter-toolkit).
+* [BUGFIX] Prevent user enumeration by timing requests sent to authenticated HTTP endpoints (via an update of prometheus/exporter-toolkit).
+
 ## 2.24.0 / 2021-01-06
 
 * [FEATURE] Add TLS and basic authentication to HTTP endpoints. #8316

VERSION

-2.24.0
+2.24.1

go.mod

@@ -52,7 +52,7 @@ require (
 	github.com/prometheus/client_golang v1.9.0
 	github.com/prometheus/client_model v0.2.0
 	github.com/prometheus/common v0.15.0
-	github.com/prometheus/exporter-toolkit v0.5.0
+	github.com/prometheus/exporter-toolkit v0.5.1
 	github.com/samuel/go-zookeeper v0.0.0-20201211165307-7117e9ea2414
 	github.com/shurcooL/httpfs v0.0.0-20190707220628-8d4bc4ba7749
 	github.com/shurcooL/vfsgen v0.0.0-20200824052919-0d455de96546

go.sum

@@ -711,8 +711,8 @@ github.com/prometheus/common v0.9.1/go.mod h1:yhUN8i9wzaXS3w1O07YhxHEBxD+W35wd8b
 github.com/prometheus/common v0.10.0/go.mod h1:Tlit/dnDKsSWFlCLTWaA1cyBgKHSMdTB80sz/V91rCo=
 github.com/prometheus/common v0.15.0 h1:4fgOnadei3EZvgRwxJ7RMpG1k1pOZth5Pc13tyspaKM=
 github.com/prometheus/common v0.15.0/go.mod h1:U+gB1OBLb1lF3O42bTCL+FK18tX9Oar16Clt/msog/s=
-github.com/prometheus/exporter-toolkit v0.5.0 h1:GwrxhCviqOl8Mm0vKqkh7Xy54m+FPlHEJacFs48M3gY=
-github.com/prometheus/exporter-toolkit v0.5.0/go.mod h1:OCkM4805mmisBhLmVFw858QYi3v0wKdY6/UxrT0pZVg=
+github.com/prometheus/exporter-toolkit v0.5.1 h1:9eqgis5er9xN613ZSADjypCJaDGj9ZlcWBvsIHa8/3c=
+github.com/prometheus/exporter-toolkit v0.5.1/go.mod h1:OCkM4805mmisBhLmVFw858QYi3v0wKdY6/UxrT0pZVg=
 github.com/prometheus/procfs v0.0.0-20181005140218-185b4288413d/go.mod h1:c3At6R/oaqEKCNdg8wHV1ftS6bRYblBhIjjI8uT2IGk=
 github.com/prometheus/procfs v0.0.0-20190117184657-bf6a532e95b1/go.mod h1:c3At6R/oaqEKCNdg8wHV1ftS6bRYblBhIjjI8uT2IGk=
 github.com/prometheus/procfs v0.0.2/go.mod h1:TjEm7ze935MbeOT/UhFTIMYKhuLP4wbCsTZCD3I8kEA=

vendor/github.com/prometheus/exporter-toolkit/web/cache.go

+// Copyright 2021 The Prometheus Authors
+// This code is partly borrowed from Caddy:
+//    Copyright 2015 Matthew Holt and The Caddy Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package web
+
+import (
+	weakrand "math/rand"
+	"sync"
+	"time"
+)
+
+var cacheSize = 100
+
+func init() {
+	weakrand.Seed(time.Now().UnixNano())
+}
+
+type cache struct {
+	cache map[string]bool
+	mtx   sync.Mutex
+}
+
+// newCache returns a cache that contains a mapping of plaintext passwords
+// to their hashes (with random eviction). This can greatly improve the
+// performance of traffic-heavy servers that use secure password hashing
+// algorithms, with the downside that plaintext passwords will be stored in
+// memory for a longer time (this should not be a problem as long as your
+// machine is not compromised, at which point all bets are off, since basicauth
+// necessitates plaintext passwords being received over the wire anyway).
+func newCache() *cache {
+	return &cache{
+		cache: make(map[string]bool),
+	}
+}
+
+func (c *cache) get(key string) (bool, bool) {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+	v, ok := c.cache[key]
+	return v, ok
+}
+
+func (c *cache) set(key string, value bool) {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+	c.makeRoom()
+	c.cache[key] = value
+}
+
+func (c *cache) makeRoom() {
+	if len(c.cache) < cacheSize {
+		return
+	}
+	// We delete more than just 1 entry so that we don't have
+	// to do this on every request; assuming the capacity of
+	// the cache is on a long tail, we can save a lot of CPU
+	// time by doing a whole bunch of deletions now and then
+	// we won't have to do them again for a while.
+	numToDelete := len(c.cache) / 10
+	if numToDelete < 1 {
+		numToDelete = 1
+	}
+	for deleted := 0; deleted <= numToDelete; deleted++ {
+		// Go maps are "nondeterministic" not actually random,
+		// so although we could just chop off the "front" of the
+		// map with less code, this is a heavily skewed eviction
+		// strategy; generating random numbers is cheap and
+		// ensures a much better distribution.
+		rnd := weakrand.Intn(len(c.cache))
+		i := 0
+		for key := range c.cache {
+			if i == rnd {
+				delete(c.cache, key)
+				break
+			}
+			i++
+		}
+	}
+}

vendor/github.com/prometheus/exporter-toolkit/web/tls_config.go

@@ -201,17 +201,19 @@ func Serve(l net.Listener, server *http.Server, tlsConfigPath string, logger log
 	if server.Handler != nil {
 		handler = server.Handler
 	}
-	server.Handler = &userAuthRoundtrip{
-		tlsConfigPath: tlsConfigPath,
-		logger:        logger,
-		handler:       handler,
-	}
 
 	c, err := getConfig(tlsConfigPath)
 	if err != nil {
 		return err
 	}
 
+	server.Handler = &userAuthRoundtrip{
+		tlsConfigPath: tlsConfigPath,
+		logger:        logger,
+		handler:       handler,
+		cache:         newCache(),
+	}
+
 	config, err := ConfigToTLSConfig(&c.TLSConfig)
 	switch err {
 	case nil:

vendor/github.com/prometheus/exporter-toolkit/web/users.go

 // Copyright 2020 The Prometheus Authors
+// This code is partly borrowed from Caddy:
+//    Copyright 2015 Matthew Holt and The Caddy Authors
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -14,7 +16,9 @@
 package web
 
 import (
+	"encoding/hex"
 	"net/http"
+	"sync"
 
 	"github.com/go-kit/kit/log"
 	"golang.org/x/crypto/bcrypt"
@@ -40,6 +44,10 @@ type userAuthRoundtrip struct {
 	tlsConfigPath string
 	handler       http.Handler
 	logger        log.Logger
+	cache         *cache
+	// bcryptMtx is there to ensure that bcrypt.CompareHashAndPassword is run
+	// only once in parallel as this is CPU intensive.
+	bcryptMtx sync.Mutex
 }
 
 func (u *userAuthRoundtrip) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -57,11 +65,31 @@ func (u *userAuthRoundtrip) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	user, pass, auth := r.BasicAuth()
 	if auth {
-		if hashedPassword, ok := c.Users[user]; ok {
-			if err := bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(pass)); err == nil {
-				u.handler.ServeHTTP(w, r)
-				return
-			}
+		hashedPassword, validUser := c.Users[user]
+
+		if !validUser {
+			// The user is not found. Use a fixed password hash to
+			// prevent user enumeration by timing requests.
+			// This is a bcrypt-hashed version of "fakepassword".
+			hashedPassword = "$2y$10$QOauhQNbBCuQDKes6eFzPeMqBSjb7Mr5DUmpZ/VcEd00UAV/LDeSi"
+		}
+
+		cacheKey := hex.EncodeToString(append(append([]byte(user), []byte(hashedPassword)...), []byte(pass)...))
+		authOk, ok := u.cache.get(cacheKey)
+
+		if !ok {
+			// This user, hashedPassword, password is not cached.
+			u.bcryptMtx.Lock()
+			err := bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(pass))
+			u.bcryptMtx.Unlock()
+
+			authOk = err == nil
+			u.cache.set(cacheKey, authOk)
+		}
+
+		if authOk && validUser {
+			u.handler.ServeHTTP(w, r)
+			return
 		}
 	}
 

vendor/modules.txt

@@ -395,7 +395,7 @@ github.com/prometheus/common/promlog/flag
 github.com/prometheus/common/route
 github.com/prometheus/common/server
 github.com/prometheus/common/version
-# github.com/prometheus/exporter-toolkit v0.5.0
+# github.com/prometheus/exporter-toolkit v0.5.1
 ## explicit
 github.com/prometheus/exporter-toolkit/web
 github.com/prometheus/exporter-toolkit/web/kingpinflag