limit User-Agent max length 1024 and add ...TRUNCATED suffix

staging/src/k8s.io/apiserver/pkg/audit/request.go

@@ -37,16 +37,20 @@ import (
 	"k8s.io/apiserver/pkg/authorization/authorizer"
 )
 
+const (
+	maxUserAgentLength      = 1024
+	userAgentTruncateSuffix = "...TRUNCATED"
+)
+
 func NewEventFromRequest(req *http.Request, level auditinternal.Level, attribs authorizer.Attributes) (*auditinternal.Event, error) {
 	ev := &auditinternal.Event{
 		RequestReceivedTimestamp: metav1.NewMicroTime(time.Now()),
 		Verb:       attribs.GetVerb(),
 		RequestURI: req.URL.RequestURI(),
-		UserAgent:  req.UserAgent(),
+		UserAgent:  maybeTruncateUserAgent(req),
+		Level:      level,
 	}
 
-	ev.Level = level
-
 	// prefer the id from the headers. If not available, create a new one.
 	// TODO(audit): do we want to forbid the header for non-front-proxy users?
 	ids := req.Header.Get(auditinternal.HeaderAuditID)
@@ -234,3 +238,13 @@ func LogAnnotations(ae *auditinternal.Event, annotations map[string]string) {
 		LogAnnotation(ae, key, value)
 	}
 }
+
+// truncate User-Agent if too long, otherwise return it directly.
+func maybeTruncateUserAgent(req *http.Request) string {
+	ua := req.UserAgent()
+	if len(ua) > maxUserAgentLength {
+		ua = ua[:maxUserAgentLength] + userAgentTruncateSuffix
+	}
+
+	return ua
+}

staging/src/k8s.io/apiserver/pkg/audit/request_test.go

@@ -17,9 +17,11 @@ limitations under the License.
 package audit
 
 import (
+	"net/http"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+
 	auditinternal "k8s.io/apiserver/pkg/apis/audit"
 )
 
@@ -36,3 +38,19 @@ func TestLogAnnotation(t *testing.T) {
 	LogAnnotation(ev, "qux", "baz")
 	assert.Equal(t, "", ev.Annotations["qux"], "audit annotation should not be overwritten.")
 }
+
+func TestMaybeTruncateUserAgent(t *testing.T) {
+	req := &http.Request{}
+	req.Header = http.Header{}
+
+	ua := "short-agent"
+	req.Header.Set("User-Agent", ua)
+	assert.Equal(t, ua, maybeTruncateUserAgent(req))
+
+	ua = ""
+	for i := 0; i < maxUserAgentLength*2; i++ {
+		ua = ua + "a"
+	}
+	req.Header.Set("User-Agent", ua)
+	assert.NotEqual(t, ua, maybeTruncateUserAgent(req))
+}