[bearertokenauthextension] Implement configauth ServerAuthenticator (open-telemetry#22739)

Closes open-telemetry#22737

---------

Signed-off-by: Benedikt Bongartz <[email protected]>

Author: frzifus

.chloggen/bearertokenauthextension_impl_server_authenticator.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: bearertokenauthextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Extension now implements configauth.ServerAuthenticator
+
+# One or more tracking issues related to the change
+issues: [22737]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

extension/bearertokenauthextension/README.md

@@ -13,7 +13,7 @@
 
 
 
-This extension implements `configauth.ClientAuthenticator` and can be used in both http and gRPC exporters inside the `auth` settings, as a means to embed a static token for every RPC call that will be made.
+This extension implements  both `configauth.ServerAuthenticator` and `configauth.ClientAuthenticator`. It can be used in both http and gRPC exporters inside the `auth` settings, as a means to embed a static token for every RPC call that will be made.
 
 The authenticator type has to be set to `bearertokenauth`.
 

extension/bearertokenauthextension/bearertokenauth.go

@@ -5,6 +5,7 @@ package bearertokenauthextension // import "github.com/open-telemetry/openteleme
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net/http"
 	"os"
@@ -34,6 +35,11 @@ func (c *PerRPCAuth) RequireTransportSecurity() bool {
 	return true
 }
 
+var (
+	_ auth.Server = (*BearerTokenAuth)(nil)
+	_ auth.Client = (*BearerTokenAuth)(nil)
+)
+
 // BearerTokenAuth is an implementation of auth.Client. It embeds a static authorization "bearer" token in every rpc call.
 type BearerTokenAuth struct {
 	muTokenString sync.RWMutex
@@ -171,6 +177,23 @@ func (b *BearerTokenAuth) RoundTripper(base http.RoundTripper) (http.RoundTrippe
 	}, nil
 }
 
+// Authenticate checks whether the given context contains valid auth data.
+func (b *BearerTokenAuth) Authenticate(ctx context.Context, headers map[string][]string) (context.Context, error) {
+	auth, ok := headers["authorization"]
+	if !ok || len(auth) == 0 {
+		return ctx, errors.New("authentication didn't succeed")
+	}
+	token := auth[0]
+	expect := b.tokenString
+	if len(b.scheme) != 0 {
+		expect = fmt.Sprintf("%s %s", b.scheme, expect)
+	}
+	if expect != token {
+		return ctx, fmt.Errorf("scheme or token does not match: %s", token)
+	}
+	return ctx, nil
+}
+
 // BearerAuthRoundTripper intercepts and adds Bearer token Authorization headers to each http request.
 type BearerAuthRoundTripper struct {
 	baseTransport   http.RoundTripper

extension/bearertokenauthextension/bearertokenauth_test.go

@@ -200,3 +200,54 @@ func TestBearerTokenFileContentUpdate(t *testing.T) {
 	authHeaderValue = resp.Header.Get("Authorization")
 	assert.Equal(t, authHeaderValue, fmt.Sprintf("%s %s", scheme, string(token)))
 }
+
+func TestBearerServerAuthenticateWithScheme(t *testing.T) {
+	const token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..." // #nosec
+	cfg := createDefaultConfig().(*Config)
+	cfg.Scheme = "Bearer"
+	cfg.BearerToken = token
+
+	bauth := newBearerTokenAuth(cfg, nil)
+	assert.NotNil(t, bauth)
+
+	ctx := context.Background()
+	assert.Nil(t, bauth.Start(ctx, componenttest.NewNopHost()))
+
+	_, err := bauth.Authenticate(ctx, map[string][]string{"authorization": {"Bearer " + token}})
+	assert.NoError(t, err)
+
+	_, err = bauth.Authenticate(ctx, map[string][]string{"authorization": {"Bearer " + "1234"}})
+	assert.Error(t, err)
+
+	_, err = bauth.Authenticate(ctx, map[string][]string{"authorization": {"" + token}})
+	assert.Error(t, err)
+
+	assert.Nil(t, bauth.Shutdown(context.Background()))
+}
+
+func TestBearerServerAuthenticate(t *testing.T) {
+	const token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..." // #nosec
+	cfg := createDefaultConfig().(*Config)
+	cfg.Scheme = ""
+	cfg.BearerToken = token
+
+	bauth := newBearerTokenAuth(cfg, nil)
+	assert.NotNil(t, bauth)
+
+	ctx := context.Background()
+	assert.Nil(t, bauth.Start(ctx, componenttest.NewNopHost()))
+
+	_, err := bauth.Authenticate(ctx, map[string][]string{"authorization": {"Bearer " + token}})
+	assert.Error(t, err)
+
+	_, err = bauth.Authenticate(ctx, map[string][]string{"authorization": {"Bearer " + "1234"}})
+	assert.Error(t, err)
+
+	_, err = bauth.Authenticate(ctx, map[string][]string{"authorization": {"invalidtoken"}})
+	assert.Error(t, err)
+
+	_, err = bauth.Authenticate(ctx, map[string][]string{"authorization": {token}})
+	assert.NoError(t, err)
+
+	assert.Nil(t, bauth.Shutdown(context.Background()))
+}