Strip Azure EventHub connection string in debug logs (elastic#25066)

* Strip Azure EventHub connection string in debug logs

CHANGELOG.next.asciidoc

@@ -279,6 +279,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix a connection error in httpjson input. {pull}16123[16123]
 - Fix integer overflow in S3 offsets when collecting very large files. {pull}22523[22523]
 - Fix CredentialsJSON unpacking for `gcp-pubsub` and `httpjson` inputs. {pull}23277[23277]
+- Strip Azure Eventhub connection string in debug logs. {pulll}[]
 
 *Filebeat*
 

x-pack/filebeat/input/azureeventhub/input.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"strings"
 	"sync"
 	"time"
 
@@ -80,7 +81,7 @@ func NewInput(
 
 	in := &azureInput{
 		config:       config,
-		log:          logp.NewLogger(fmt.Sprintf("%s input", inputName)).With("connection string", config.ConnectionString),
+		log:          logp.NewLogger(fmt.Sprintf("%s input", inputName)).With("connection string", stripConnectionString(config.ConnectionString)),
 		context:      inputContext,
 		workerCtx:    workerCtx,
 		workerCancel: workerCancel,
@@ -235,3 +236,17 @@ func (a *azureInput) parseMultipleMessages(bMessage []byte) []string {
 	}
 	return messages
 }
+
+// Strip connection string to remove sensitive information
+// A connection string should look like this:
+// Endpoint=sb://dummynamespace.servicebus.windows.net/;SharedAccessKeyName=DummyAccessKeyName;SharedAccessKey=5dOntTRytoC24opYThisAsit3is2B+OGY1US/fuL3ly=
+// This code will remove everything after ';' so key information is stripped
+func stripConnectionString(c string) string {
+	if parts := strings.SplitN(c, ";", 2); len(parts) == 2 {
+		return parts[0]
+	}
+
+	// We actually expect the string to have the documented format
+	// if we reach here something is wrong, so let's stay on the safe side
+	return "(redacted)"
+}

x-pack/filebeat/input/azureeventhub/input_test.go

@@ -120,6 +120,30 @@ func TestNewInputDone(t *testing.T) {
 	inputtest.AssertNotStartedInputCanBeDone(t, NewInput, &config)
 }
 
+func TestStripConnectionString(t *testing.T) {
+	tests := []struct {
+		connectionString, expected string
+	}{
+		{
+			"Endpoint=sb://something",
+			"(redacted)",
+		},
+		{
+			"Endpoint=sb://dummynamespace.servicebus.windows.net/;SharedAccessKeyName=DummyAccessKeyName;SharedAccessKey=5dOntTRytoC24opYThisAsit3is2B+OGY1US/fuL3ly=",
+			"Endpoint=sb://dummynamespace.servicebus.windows.net/",
+		},
+		{
+			"Endpoint=sb://dummynamespace.servicebus.windows.net/;SharedAccessKey=5dOntTRytoC24opYThisAsit3is2B+OGY1US/fuL3ly=",
+			"Endpoint=sb://dummynamespace.servicebus.windows.net/",
+		},
+	}
+
+	for _, tt := range tests {
+		res := stripConnectionString(tt.connectionString)
+		assert.Equal(t, res, tt.expected)
+	}
+}
+
 type stubOutleter struct {
 	sync.Mutex
 	cond   *sync.Cond