From 42668f8804eb74f5c5cb257f88719f50f1370903 Mon Sep 17 00:00:00 2001
From: Anders Eknert <anders@eknert.com>
Date: Sat, 26 Mar 2022 08:25:28 +0100
Subject: [PATCH] logging: mask authorization header value in debug logs
 (#4496)

Fixes #4495

Signed-off-by: Anders Eknert <anders@eknert.com>
---
 plugins/rest/rest.go      | 30 +++++++++++++++++------
 plugins/rest/rest_test.go | 50 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+), 7 deletions(-)

diff --git a/plugins/rest/rest.go b/plugins/rest/rest.go
index eb66543fbb..41fc853dcd 100644
--- a/plugins/rest/rest.go
+++ b/plugins/rest/rest.go
@@ -293,16 +293,19 @@ func (c Client) Do(ctx context.Context, method, path string) (*http.Response, er
 		return nil, err
 	}
 
-	c.loggerFields = map[string]interface{}{
-		"method":  method,
-		"url":     url,
-		"headers": req.Header,
-	}
+	if c.logger.GetLevel() >= logging.Debug {
+		c.loggerFields = map[string]interface{}{
+			"method":  method,
+			"url":     url,
+			"headers": withMaskedAuthorizationHeader(req.Header),
+		}
 
-	c.logger.WithFields(c.loggerFields).Debug("Sending request.")
+		c.logger.WithFields(c.loggerFields).Debug("Sending request.")
+	}
 
 	resp, err := httpClient.Do(req)
-	if resp != nil {
+
+	if resp != nil && c.logger.GetLevel() >= logging.Debug {
 		// Only log for debug purposes. If an error occurred, the caller should handle
 		// that. In the non-error case, the caller may not do anything.
 		c.loggerFields["status"] = resp.Status
@@ -312,3 +315,16 @@ func (c Client) Do(ctx context.Context, method, path string) (*http.Response, er
 
 	return resp, err
 }
+
+func withMaskedAuthorizationHeader(headers http.Header) http.Header {
+	authzHeader := headers.Get("Authorization")
+	if authzHeader != "" {
+		masked := make(http.Header)
+		for k, v := range headers {
+			masked[k] = v
+		}
+		masked.Set("Authorization", "REDACTED")
+		return masked
+	}
+	return headers
+}
diff --git a/plugins/rest/rest_test.go b/plugins/rest/rest_test.go
index bf54476eee..2c3d497af9 100644
--- a/plugins/rest/rest_test.go
+++ b/plugins/rest/rest_test.go
@@ -34,9 +34,12 @@ import (
 	"github.com/open-policy-agent/opa/internal/jwx/jwa"
 	"github.com/open-policy-agent/opa/internal/jwx/jws"
 	"github.com/open-policy-agent/opa/keys"
+	"github.com/open-policy-agent/opa/logging"
 
 	"github.com/open-policy-agent/opa/internal/version"
 	"github.com/open-policy-agent/opa/util/test"
+
+	testlogger "github.com/open-policy-agent/opa/logging/test"
 )
 
 const keyID = "key1"
@@ -1514,6 +1517,53 @@ func TestS3SigningInstantiationInitializesLogger(t *testing.T) {
 	}
 }
 
+func TestDebugLoggingRequestMaskAuthorizationHeader(t *testing.T) {
+	token := "secret"
+	ts := testServer{t: t, expBearerToken: token}
+	ts.start()
+	defer ts.stop()
+
+	config := fmt.Sprintf(`{
+		"name": "foo",
+		"url": %q,
+		"credentials": {
+			"bearer": {
+				"token": %q
+			}
+		}
+	}`, ts.server.URL, token)
+	client, err := New([]byte(config), map[string]*keys.Config{})
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	logger := testlogger.New()
+	logger.SetLevel(logging.Debug)
+	client.logger = logger
+
+	ctx := context.Background()
+	if _, err := client.Do(ctx, "GET", "test"); err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	var reqLogFound bool
+	for _, entry := range logger.Entries() {
+		if entry.Fields["headers"] != nil {
+			headers := entry.Fields["headers"].(http.Header)
+			authzHeader := headers.Get("Authorization")
+			if authzHeader != "" {
+				reqLogFound = true
+				if authzHeader != "REDACTED" {
+					t.Errorf("Excpected redacted Authorization header value, got %v", authzHeader)
+				}
+			}
+		}
+	}
+	if !reqLogFound {
+		t.Fatalf("Expected log entry from request")
+	}
+}
+
 func newTestClient(t *testing.T, ts *testServer, certPath string, keypath string) *Client {
 	config := fmt.Sprintf(`{
 			"name": "foo",