From 1665054fed306e492945c499f1c772ecf7b56b26 Mon Sep 17 00:00:00 2001
From: jar-stripe <jar@stripe.com>
Date: Wed, 23 Oct 2024 17:02:44 -0700
Subject: [PATCH] Update webhook API version validation (#1940)

replaced api version check in webhook/client with isCompatibleApiVersion, which will test if the release identifier of the webhook event matches the pinned version, or return false for any event api version that does not have a release identifier
---
 webhook/client.go      | 16 ++++++++++-
 webhook/client_test.go | 63 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/webhook/client.go b/webhook/client.go
index e85232c623..27169f2a1f 100644
--- a/webhook/client.go
+++ b/webhook/client.go
@@ -187,6 +187,20 @@ type signedHeader struct {
 // Private functions
 //
 
+func isCompatibleAPIVersion(eventApiVersion string) bool {
+	// If the event api version is from before we started adding
+	// a release train, there's no way its compatible with this
+	// version
+	if !strings.Contains(eventApiVersion, ".") {
+		return false
+	}
+
+	// versions are yyyy-MM-dd.train
+	var eventReleaseTrain = strings.Split(eventApiVersion, ".")[1]
+	var currentReleaseTrain = strings.Split(stripe.APIVersion, ".")[1]
+	return eventReleaseTrain == currentReleaseTrain
+}
+
 func constructEvent(payload []byte, sigHeader string, secret string, options ConstructEventOptions) (stripe.Event, error) {
 	e := stripe.Event{}
 
@@ -203,7 +217,7 @@ func constructEvent(payload []byte, sigHeader string, secret string, options Con
 		return e, fmt.Errorf("Failed to parse webhook body json: %s", err.Error())
 	}
 
-	if !options.IgnoreAPIVersionMismatch && e.APIVersion != stripe.APIVersion {
+	if !options.IgnoreAPIVersionMismatch && !isCompatibleAPIVersion(e.APIVersion) {
 		return e, fmt.Errorf("Received event with API version %s, but stripe-go %s expects API version %s. We recommend that you create a WebhookEndpoint with this API version. Otherwise, you can disable this error by using `ConstructEventWithOptions(..., ConstructEventOptions{..., ignoreAPIVersionMismatch: true})`  but be wary that objects may be incorrectly deserialized.", e.APIVersion, stripe.ClientVersion, stripe.APIVersion)
 	}
 
diff --git a/webhook/client_test.go b/webhook/client_test.go
index fd91a08a75..accc5dd634 100644
--- a/webhook/client_test.go
+++ b/webhook/client_test.go
@@ -15,11 +15,25 @@ var testPayload = []byte(fmt.Sprintf(`{
   "object": "event",
   "api_version": "%s"
 }`, stripe.APIVersion))
+
+var testPayloadWithNewVersionInReleaseTrain = []byte(fmt.Sprintf(`{
+	"id": "evt_test_webhook",
+	"object": "event",
+	"api_version": "%s"
+  }`, "2099-10-10."+strings.Split(stripe.APIVersion, ".")[1]))
+
 var testPayloadWithAPIVersionMismatch = []byte(`{
 	"id": "evt_test_webhook",
 	"object": "event",
 	"api_version": "2020-01-01"
   }`)
+
+var testPayloadWithReleaseTrainVersionMismatch = []byte(`{
+	"id": "evt_test_webhook",
+	"object": "event",
+	"api_version": "2099-10-10.the_larch"
+  }`)
+
 var testSecret = "whsec_test_secret"
 
 func newSignedPayload(options ...func(*SignedPayload)) *SignedPayload {
@@ -179,7 +193,39 @@ func TestTokenNew(t *testing.T) {
 	}
 }
 
-func TestConstructEvent_ErrorOnAPIVersionMismatch(t *testing.T) {
+func TestConstructEvent_SuccessOnExpectedAPIVersion(t *testing.T) {
+	p := newSignedPayload(func(p *SignedPayload) {
+		p.Payload = testPayload
+	})
+
+	evt, err := ConstructEvent(p.Payload, p.Header, p.Secret)
+
+	if err != nil {
+		t.Errorf("Unexpected error in ConstructEvent: %v", err)
+	}
+
+	if evt.APIVersion != stripe.APIVersion {
+		t.Errorf("Expected API versions to match")
+	}
+}
+
+func TestConstructEvent_SuccessOnNewAPIVersionInExpectedReleaseTrain(t *testing.T) {
+	p := newSignedPayload(func(p *SignedPayload) {
+		p.Payload = testPayloadWithNewVersionInReleaseTrain
+	})
+
+	evt, err := ConstructEvent(p.Payload, p.Header, p.Secret)
+
+	if err != nil {
+		t.Errorf("Unexpected error in ConstructEvent: %v", err)
+	}
+
+	expectedSuffix := "." + strings.Split(stripe.APIVersion, ".")[1]
+	if !strings.HasSuffix(evt.APIVersion, expectedSuffix) {
+		t.Errorf("Expected API release trains to match")
+	}
+}
+func TestConstructEvent_ErrorOnLegacyAPIVersionMismatch(t *testing.T) {
 	p := newSignedPayload(func(p *SignedPayload) {
 		p.Payload = testPayloadWithAPIVersionMismatch
 	})
@@ -195,6 +241,21 @@ func TestConstructEvent_ErrorOnAPIVersionMismatch(t *testing.T) {
 	}
 }
 
+func TestConstructEvent_ErrorOnReleaseTrainMismatch(t *testing.T) {
+	p := newSignedPayload(func(p *SignedPayload) {
+		p.Payload = testPayloadWithReleaseTrainVersionMismatch
+	})
+
+	_, err := ConstructEvent(p.Payload, p.Header, p.Secret)
+
+	if err == nil {
+		t.Errorf("Expected error due to API version mismatch.")
+	}
+
+	if !strings.Contains(err.Error(), "Received event with API version") {
+		t.Errorf("Expected API version mismatch error but received %v", err)
+	}
+}
 func TestConstructEventWithOptions_IgnoreAPIVersionMismatch(t *testing.T) {
 
 	p := newSignedPayload(func(p *SignedPayload) {