feat: HTTP Bearer Authorization for simple use cases

Add support for HTTP Bearer Authorization for simple use cases, where
HTTP Basic might not fit workflows.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

docs/web-config.yml

@@ -10,3 +10,9 @@ tls_server_config:
 basic_auth_users:
   alice: $2y$10$mDwo.lAisC94iLAyP81MCesa29IzH37oigHC/42V2pdJlUprsJPze
   bob: $2y$10$hLqFl9jSjoAAy95Z/zw8Ye8wkdMBM8c5Bn1ptYqP/AXyV0.oy0S8m
+
+# Tokens that have full access to the web server via Bearer authentication.
+# Multiple tokens are accepted, to support gradual credential rollover.
+# If empty, no Bearer authentication is required.
+bearer_auth_tokens:
+  - ExampleBearerToken

docs/web-configuration.md

@@ -125,6 +125,12 @@ http_server_config:
 # required. Passwords are hashed with bcrypt.
 basic_auth_users:
   [ <string>: <secret> ... ]
+
+# Tokens that have full access to the web server via Bearer authentication.
+# Multiple tokens are accepted, to support gradual credential rollover.
+# If empty, no Bearer authentication is required.
+bearer_auth_tokens:
+  [- <token>]
 ```
 
 [A sample configuration file](web-config.yml) is provided.
@@ -148,6 +154,6 @@ authenticated HTTP request and then cached.
 
 ## Performance
 
-Basic authentication is meant for simple use cases, with a few users.  If you
-need to authenticate a lot of users, it is recommended to use TLS client
+Basic & Bearer authentication are meant for simple use cases, with a few users.
+If you need to authenticate a lot of users, it is recommended to use TLS client
 certificates, or to use a proper reverse proxy to handle the authentication.

web/handler.go

@@ -24,6 +24,8 @@ import (
 
 	"github.com/go-kit/log"
 	"golang.org/x/crypto/bcrypt"
+
+	config_util "github.com/prometheus/common/config"
 )
 
 // extraHTTPHeaders is a map of HTTP headers that can be added to HTTP
@@ -53,6 +55,18 @@ func validateUsers(configPath string) error {
 	return nil
 }
 
+func validateTokens(configPath string) error {
+	//c, err := getConfig(configPath)
+	//if err != nil {
+	//	return err
+	//}
+
+	//for _, p := range c.Bearer {
+	//}
+
+	return nil
+}
+
 // validateHeaderConfig checks that the provided header configuration is correct.
 // It does not check the validity of all the values, only the ones which are
 // well-defined enumerations.
@@ -98,11 +112,19 @@ func (u *webHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set(k, v)
 	}
 
-	if len(c.Users) == 0 {
-		u.handler.ServeHTTP(w, r)
+	if len(c.Users) > 0 {
+		u.ServeHTTPAuthBasic(w, r, c)
+		return
+	}
+	if len(c.Tokens) > 0 {
+		u.ServeHTTPAuthBearer(w, r, c)
 		return
 	}
 
+	u.handler.ServeHTTP(w, r)
+}
+
+func (u *webHandler) ServeHTTPAuthBasic(w http.ResponseWriter, r *http.Request, c *Config) {
 	user, pass, auth := r.BasicAuth()
 	if auth {
 		hashedPassword, validUser := c.Users[user]
@@ -141,3 +163,19 @@ func (u *webHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("WWW-Authenticate", "Basic")
 	http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
 }
+
+func (u *webHandler) ServeHTTPAuthBearer(w http.ResponseWriter, r *http.Request, c *Config) {
+	rawHttpAuthorization := r.Header.Get("Authorization")
+	prefix := "Bearer "
+	if strings.HasPrefix(rawHttpAuthorization, prefix) {
+		token := config_util.Secret(strings.TrimPrefix(rawHttpAuthorization, prefix))
+		_, tokenExists := c.tokenMap[token]
+		if tokenExists {
+			u.handler.ServeHTTP(w, r)
+			return
+		}
+	}
+
+	w.Header().Set("WWW-Authenticate", "Bearer")
+	http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
+}

web/testdata/web_config_tokens.good.yml

@@ -0,0 +1,5 @@
+tls_server_config:
+  cert_file: "server.crt"
+  key_file: "server.key"
+bearer_auth_tokens:
+  - TokenTest12345

web/testdata/web_config_tokens_noTLS.good.yml

@@ -0,0 +1,2 @@
+bearer_auth_tokens:
+  - TokenTest12345

web/tls_config.go

@@ -40,6 +40,9 @@ type Config struct {
 	TLSConfig  TLSConfig                     `yaml:"tls_server_config"`
 	HTTPConfig HTTPConfig                    `yaml:"http_server_config"`
 	Users      map[string]config_util.Secret `yaml:"basic_auth_users"`
+	Tokens     []config_util.Secret          `yaml:"bearer_auth_tokens"`
+
+	tokenMap map[config_util.Secret]bool // Fast lookup for Bearer Tokens
 }
 
 type TLSConfig struct {
@@ -123,6 +126,14 @@ func getConfig(configPath string) (*Config, error) {
 	if err == nil {
 		err = validateHeaderConfig(c.HTTPConfig.Header)
 	}
+	// Convert tokens for fast lookup
+	if len(c.Tokens) > 0 {
+		c.tokenMap = make(map[config_util.Secret]bool, len(c.Tokens))
+		for _, t := range c.Tokens {
+			c.tokenMap[t] = true
+		}
+	}
+
 	c.TLSConfig.SetDirectory(filepath.Dir(configPath))
 	return c, err
 }
@@ -320,6 +331,9 @@ func Serve(l net.Listener, server *http.Server, flags *FlagConfig, logger log.Lo
 	if err := validateUsers(tlsConfigPath); err != nil {
 		return err
 	}
+	if err := validateTokens(tlsConfigPath); err != nil {
+		return err
+	}
 
 	// Setup basic authentication.
 	var handler http.Handler = http.DefaultServeMux
@@ -379,6 +393,9 @@ func Validate(tlsConfigPath string) error {
 	if err := validateUsers(tlsConfigPath); err != nil {
 		return err
 	}
+	if err := validateTokens(tlsConfigPath); err != nil {
+		return err
+	}
 	c, err := getConfig(tlsConfigPath)
 	if err != nil {
 		return err

web/tls_config_test.go

@@ -102,6 +102,8 @@ type TestInputs struct {
 	CurvePreferences    []tls.CurveID
 	Username            string
 	Password            string
+	Token               string
+	Authorization       string // Raw authorization
 	ClientCertificate   string
 }
 
@@ -516,6 +518,12 @@ func (test *TestInputs) Test(t *testing.T) {
 		if test.Username != "" {
 			req.SetBasicAuth(test.Username, test.Password)
 		}
+		if test.Token != "" {
+			req.Header.Set("Authorization", "Bearer "+test.Token)
+		}
+		if test.Authorization != "" {
+			req.Header.Set("Authorization", test.Authorization)
+		}
 		return client.Do(req)
 	}
 	go func() {
@@ -698,3 +706,93 @@ func TestUsers(t *testing.T) {
 		t.Run(testInputs.Name, testInputs.Test)
 	}
 }
+
+func TestTokens(t *testing.T) {
+	testTables := []*TestInputs{
+		{
+			Name:           `with correct token`,
+			YAMLConfigPath: "testdata/web_config_tokens_noTLS.good.yml",
+			Token:          "TokenTest12345",
+			ExpectedError:  nil,
+		},
+		{
+			Name:           `with incorrect token`,
+			YAMLConfigPath: "testdata/web_config_tokens_noTLS.good.yml",
+			Token:          "TokenTest12345",
+			ExpectedError:  nil,
+		},
+		{
+			Name:           `without token and TLS`,
+			YAMLConfigPath: "testdata/web_config_tokens.good.yml",
+			UseTLSClient:   true,
+			ExpectedError:  ErrorMap["Unauthorized"],
+		},
+		{
+			Name:           `with correct token and TLS`,
+			YAMLConfigPath: "testdata/web_config_tokens.good.yml",
+			UseTLSClient:   true,
+			Token:          "TokenTest12345",
+			ExpectedError:  nil,
+		},
+		{
+			Name:           `with incorrect token and TLS`,
+			YAMLConfigPath: "testdata/web_config_tokens.good.yml",
+			UseTLSClient:   true,
+			Token:          "nonexistent",
+			ExpectedError:  ErrorMap["Unauthorized"],
+		},
+	}
+	for _, testInputs := range testTables {
+		t.Run(testInputs.Name, testInputs.Test)
+	}
+}
+
+func TestRawAuthorization(t *testing.T) {
+	testTables := []*TestInputs{
+		{
+			Name:           `with raw authorization vs expected user`,
+			YAMLConfigPath: "testdata/web_config_users_noTLS.good.yml",
+			Authorization:  "FakeAuth FakeAuthMagic12345",
+			UseTLSClient:   false,
+			ExpectedError:  ErrorMap["Unauthorized"],
+		},
+		{
+			Name:           `with raw authorization and TLS vs expected user`,
+			YAMLConfigPath: "testdata/web_config_users.good.yml",
+			Authorization:  "FakeAuth FakeAuthMagic12345",
+			UseTLSClient:   true,
+			ExpectedError:  ErrorMap["Unauthorized"],
+		},
+		{
+			Name:           `with raw authorization vs expected token`,
+			YAMLConfigPath: "testdata/web_config_tokens_noTLS.good.yml",
+			Authorization:  "FakeAuth FakeAuthMagic12345",
+			UseTLSClient:   false,
+			ExpectedError:  ErrorMap["Unauthorized"],
+		},
+		{
+			Name:           `with raw authorization and TLS vs expected token`,
+			YAMLConfigPath: "testdata/web_config_tokens.good.yml",
+			Authorization:  "FakeAuth FakeAuthMagic12345",
+			UseTLSClient:   true,
+			ExpectedError:  ErrorMap["Unauthorized"],
+		},
+		{
+		    Name:           `with raw authorization vs no auth expected`,
+			YAMLConfigPath: "testdata/web_config_noAuth.good.yml",
+			Authorization:  "FakeAuth FakeAuthMagic12345",
+			UseTLSClient:   true,
+			ExpectedError:  nil,
+		},
+		{
+			Name:           `with raw authorization, no TLS, vs no auth expected`,
+			YAMLConfigPath: "testdata/web_config_empty.yml",
+			Authorization:  "FakeAuth FakeAuthMagic12345",
+			UseTLSClient:   false,
+			ExpectedError:  nil,
+		},
+	}
+	for _, testInputs := range testTables {
+		t.Run(testInputs.Name, testInputs.Test)
+	}
+}