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send idempotency keys with redirect checkout #8736

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11e2295
initial commit
atavism May 6, 2026
56592f5
Merge remote-tracking branch 'origin/main' into atavism/payment-redirect
atavism May 6, 2026
72a8026
payment: clean redirect idempotency plumbing
atavism May 6, 2026
3ae3fa2
code review updates
atavism May 6, 2026
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7 changes: 6 additions & 1 deletion android/app/src/main/kotlin/org/getlantern/lantern/handler/MethodHandler.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -467,10 +467,15 @@ class MethodHandler : FlutterPlugin,
scope.launch {
result.runCatching {
val map = call.arguments as Map<*, *>
val idempotencyKey = map["idempotencyKey"] as? String
if (idempotencyKey.isNullOrBlank()) {
throw IllegalArgumentException("Payment redirect idempotency key is required")
}
val url = Mobile.paymentRedirect(
map["provider"] as String,
map["planId"] as String,
map["email"] as String
map["email"] as String,
idempotencyKey
)
withContext(Dispatchers.Main) {
success(url)
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2 changes: 1 addition & 1 deletion go.mod
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@ replace github.com/quic-go/qpack => github.com/quic-go/qpack v0.5.1
require (
github.com/alecthomas/assert/v2 v2.3.0
github.com/getlantern/lantern-server-provisioner v0.0.0-20251031121934-8ea031fccfa9
github.com/getlantern/radiance v0.0.0-20260506180721-4445a2040ede
github.com/getlantern/radiance v0.0.0-20260506192624-6309530dece6
github.com/sagernet/sing-box v1.12.22
golang.org/x/mobile v0.0.0-20250711185624-d5bb5ecc55c0
golang.org/x/sys v0.41.0
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2 changes: 2 additions & 0 deletions go.sum
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Expand Up @@ -263,6 +263,8 @@ github.com/getlantern/publicip v0.0.0-20260328175246-2c460fe80c6b h1:gMYJzEhLrmI
github.com/getlantern/publicip v0.0.0-20260328175246-2c460fe80c6b/go.mod h1:NpfXdK4ldEKkjQ4P1R+DBF4ua5VFOlxmgHROTnYrApg=
github.com/getlantern/radiance v0.0.0-20260506180721-4445a2040ede h1:RCf7U3JiNDMuhbS/lPp4qP6CbA2xmXBXEVk4gvRMysM=
github.com/getlantern/radiance v0.0.0-20260506180721-4445a2040ede/go.mod h1:RG9PNWlBmS4HPFf6JTQ9CnsCD98zy75vvm7PnBIsdQI=
github.com/getlantern/radiance v0.0.0-20260506192624-6309530dece6 h1:8139ZlUwUemO0whyBaGsmRP9kzzIyDENrEmwJsRQIqY=
github.com/getlantern/radiance v0.0.0-20260506192624-6309530dece6/go.mod h1:RG9PNWlBmS4HPFf6JTQ9CnsCD98zy75vvm7PnBIsdQI=
github.com/getlantern/samizdat v0.0.3-0.20260327203406-ef7323341974 h1:k+/qNo5YNO+8M8LVUp6G5Evm1OQdEs3Z4ye8top4AhI=
github.com/getlantern/samizdat v0.0.3-0.20260327203406-ef7323341974/go.mod h1:uEeykQSW2/6rTjfPlj3MTTo59poSHXfAHTGgzYDkbr0=
github.com/getlantern/semconv v0.0.0-20260327040646-21845dda05cb h1:c5YM7b3a4r2J8Eh89KkI6M/iTFe6Bi+b8AJlfkKdFq4=
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44 changes: 31 additions & 13 deletions lantern-core/core.go
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Expand Up @@ -119,10 +119,10 @@ type Payment interface {
StripeBillingPortalUrl() (string, error)
AcknowledgeGooglePurchase(purchaseToken, planId string) (string, error)
AcknowledgeApplePurchase(receipt, planII string) (string, error)
PaymentRedirect(provider, planID, email string) (string, error)
PaymentRedirect(provider, planID, email, idempotencyKey string) (string, error)
ActivationCode(email, resellerCode string) error
SubscriptionPaymentRedirectURL(redirectBody account.PaymentRedirectData) (string, error)
StripeSubscriptionPaymentRedirect(subscriptionType, planID, email string) (string, error)
StripeSubscriptionPaymentRedirect(subscriptionType, planID, email, idempotencyKey string) (string, error)
}

type SplitTunnel interface {
Expand Down Expand Up @@ -866,29 +866,47 @@ func (lc *LanternCore) SubscriptionPaymentRedirectURL(redirectBody account.Payme
return lc.client.SubscriptionPaymentRedirectURL(lc.ctx, redirectBody)
}

func (lc *LanternCore) StripeSubscriptionPaymentRedirect(subscriptionType, planID, email string) (string, error) {
func (lc *LanternCore) StripeSubscriptionPaymentRedirect(subscriptionType, planID, email, idempotencyKey string) (string, error) {
idempotencyKey, err := normalizePaymentRedirectIdempotencyKey(idempotencyKey)
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@jigar-f jigar-f May 7, 2026

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@atavism Do you think we should just create the idempotencyKey key here, since generation is basically the same, so we don't have to pass it through all the platforms? Is there any issue with that?

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@atavism atavism May 7, 2026

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@jigar-f I put the key generation in Flutter to tie the key to the user’s checkout attempt. If core creates a new key every time PaymentRedirect is called, two duplicate calls could still become two different payment requests. Do you think the extra platform plumbing is fine given this context?

if err != nil {
return "", err
}
deviceID := lc.MyDeviceId()
redirectBody := account.PaymentRedirectData{
Provider: "stripe",
Plan: planID,
DeviceName: deviceID,
Email: email,
BillingType: account.SubscriptionType(subscriptionType),
Provider: "stripe",
Plan: planID,
DeviceName: deviceID,
Email: email,
BillingType: account.SubscriptionType(subscriptionType),
IdempotencyKey: idempotencyKey,
}
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return lc.SubscriptionPaymentRedirectURL(redirectBody)
}

func (lc *LanternCore) PaymentRedirect(provider, planId, email string) (string, error) {
func (lc *LanternCore) PaymentRedirect(provider, planId, email, idempotencyKey string) (string, error) {
idempotencyKey, err := normalizePaymentRedirectIdempotencyKey(idempotencyKey)
if err != nil {
return "", err
}
deviceName := lc.MyDeviceId()
body := account.PaymentRedirectData{
Provider: provider,
Plan: planId,
DeviceName: deviceName,
Email: email,
Provider: provider,
Plan: planId,
DeviceName: deviceName,
Email: email,
IdempotencyKey: idempotencyKey,
}
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return lc.client.PaymentRedirect(lc.ctx, body)
}

func normalizePaymentRedirectIdempotencyKey(idempotencyKey string) (string, error) {
idempotencyKey = strings.TrimSpace(idempotencyKey)
if idempotencyKey == "" {
return "", fmt.Errorf("payment redirect idempotency key is required")
}
return idempotencyKey, nil
}

func (lc *LanternCore) ActivationCode(email, resellerCode string) error {
purchase, err := lc.client.ActivationCode(lc.ctx, email, resellerCode)
if err != nil {
Expand Down
10 changes: 6 additions & 4 deletions lantern-core/ffi/ffi.go
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Expand Up @@ -633,16 +633,17 @@ func fetchUserData() *C.char {
// Fetch stipe subscription payment redirect link
//
//export stripeSubscriptionPaymentRedirect
func stripeSubscriptionPaymentRedirect(subType, _planId, _email *C.char) *C.char {
func stripeSubscriptionPaymentRedirect(subType, _planId, _email, _idempotencyKey *C.char) *C.char {
subscriptionType := C.GoString(subType)
planID := C.GoString(_planId)
email := C.GoString(_email)
idempotencyKey := C.GoString(_idempotencyKey)
return runOnGoStack(func() *C.char {
c, errStr := requireCore()
if errStr != nil {
return errStr
}
redirect, err := c.StripeSubscriptionPaymentRedirect(subscriptionType, planID, email)
redirect, err := c.StripeSubscriptionPaymentRedirect(subscriptionType, planID, email, idempotencyKey)
if err != nil {
return SendError(err)
}
Expand All @@ -653,16 +654,17 @@ func stripeSubscriptionPaymentRedirect(subType, _planId, _email *C.char) *C.char
// Fetch payment redirect link for providers like alipay
//
//export paymentRedirect
func paymentRedirect(_plan, _provider, _email *C.char) *C.char {
func paymentRedirect(_plan, _provider, _email, _idempotencyKey *C.char) *C.char {
plan := C.GoString(_plan)
provider := C.GoString(_provider)
email := C.GoString(_email)
idempotencyKey := C.GoString(_idempotencyKey)
return runOnGoStack(func() *C.char {
c, errStr := requireCore()
if errStr != nil {
return errStr
}
redirect, err := c.PaymentRedirect(provider, plan, email)
redirect, err := c.PaymentRedirect(provider, plan, email, idempotencyKey)
if err != nil {
return SendError(err)
}
Expand Down
11 changes: 6 additions & 5 deletions lantern-core/mobile/mobile.go
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Original file line number Diff line number Diff line change
Expand Up @@ -555,17 +555,18 @@ func AcknowledgeApplePurchase(receipt, planII string) (string, error) {
})
}

func PaymentRedirect(provider, planId, email string) (string, error) {
return withCoreR(func(c lanterncore.Core) (string, error) { return c.PaymentRedirect(provider, planId, email) })

func PaymentRedirect(provider, planId, email, idempotencyKey string) (string, error) {
return withCoreR(func(c lanterncore.Core) (string, error) {
return c.PaymentRedirect(provider, planId, email, idempotencyKey)
})
}

// /This is specifically for stripe subscriptions that require a redirect to complete the payment
// This is only used for macos
func StripeSubscriptionPaymentRedirect(subType, planId, email string) (string, error) {
func StripeSubscriptionPaymentRedirect(subType, planId, email, idempotencyKey string) (string, error) {
slog.Debug("stripeSubscriptionPaymentRedirect called")
return withCoreR(func(c lanterncore.Core) (string, error) {
return c.StripeSubscriptionPaymentRedirect(subType, planId, email)
return c.StripeSubscriptionPaymentRedirect(subType, planId, email, idempotencyKey)
})
}

Expand Down
8 changes: 8 additions & 0 deletions lib/core/common/common.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,14 @@ String generatePassword() {
).join();
}

String generatePaymentRedirectIdempotencyKey() {
final random = Random.secure();
return List.generate(
16,
(_) => random.nextInt(256).toRadixString(16).padLeft(2, '0'),
).join();
}

bool isStoreVersion() {
if (!PlatformUtils.isMobile) {
return false;
Expand Down
10 changes: 9 additions & 1 deletion lib/features/plans/provider/payment_notifier.dart
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Expand Up @@ -54,12 +54,14 @@ class PaymentNotifier extends _$PaymentNotifier {
String planId,
String email,
) async {
final idempotencyKey = generatePaymentRedirectIdempotencyKey();
return ref
.read(lanternServiceProvider)
.stipeSubscriptionPaymentRedirect(
type: type,
planId: planId,
email: email,
idempotencyKey: idempotencyKey,
);
}

Expand All @@ -77,9 +79,15 @@ class PaymentNotifier extends _$PaymentNotifier {
required String planId,
required String email,
}) async {
final idempotencyKey = generatePaymentRedirectIdempotencyKey();
return ref
.read(lanternServiceProvider)
.paymentRedirect(provider: provider, planId: planId, email: email);
.paymentRedirect(
provider: provider,
planId: planId,
email: email,
idempotencyKey: idempotencyKey,
);
}

Future<Either<Failure, String?>> startUpgradeFlow({
Expand Down
12 changes: 7 additions & 5 deletions lib/lantern/lantern_core_service.dart
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Expand Up @@ -84,17 +84,19 @@ abstract class LanternCoreService {

Future<Either<Failure, String>> getOAuthProvider();


///Payments methods
Future<Either<Failure, String>> stipeSubscriptionPaymentRedirect(
{required BillingType type,
required String planId,
required String email});
Future<Either<Failure, String>> stipeSubscriptionPaymentRedirect({
required BillingType type,
required String planId,
required String email,
required String idempotencyKey,
});

Future<Either<Failure, String>> paymentRedirect({
required String provider,
required String planId,
required String email,
required String idempotencyKey,
});

// this is used for stripe subscription
Expand Down
4 changes: 4 additions & 0 deletions lib/lantern/lantern_ffi_service.dart
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Expand Up @@ -738,6 +738,7 @@ class LanternFFIService implements LanternCoreService {
required BillingType type,
required String planId,
required String email,
required String idempotencyKey,
}) async {
try {
appLogger.debug('Starting Stripe Subscription Payment Redirect');
Expand All @@ -747,6 +748,7 @@ class LanternFFIService implements LanternCoreService {
type.name.toCharPtr,
planId.toCharPtr,
email.toCharPtr,
idempotencyKey.toCharPtr,
)
.toDartString();
});
Expand Down Expand Up @@ -889,6 +891,7 @@ class LanternFFIService implements LanternCoreService {
required String provider,
required String planId,
required String email,
required String idempotencyKey,
}) async {
try {
final result = await runInBackground<String>(() async {
Expand All @@ -897,6 +900,7 @@ class LanternFFIService implements LanternCoreService {
planId.toCharPtr,
provider.toCharPtr,
email.toCharPtr,
idempotencyKey.toCharPtr,
)
.toDartString();
});
Expand Down
15 changes: 13 additions & 2 deletions lib/lantern/lantern_generated_bindings.dart
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Expand Up @@ -5669,8 +5669,14 @@ class LanternBindings {
ffi.Pointer<ffi.Char> subType,
ffi.Pointer<ffi.Char> _planId,
ffi.Pointer<ffi.Char> _email,
ffi.Pointer<ffi.Char> _idempotencyKey,
) {
return _stripeSubscriptionPaymentRedirect(subType, _planId, _email);
return _stripeSubscriptionPaymentRedirect(
subType,
_planId,
_email,
_idempotencyKey,
);
}

late final _stripeSubscriptionPaymentRedirectPtr =
Expand All @@ -5680,6 +5686,7 @@ class LanternBindings {
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
)
>
>('stripeSubscriptionPaymentRedirect');
Expand All @@ -5690,15 +5697,17 @@ class LanternBindings {
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
)
>();

ffi.Pointer<ffi.Char> paymentRedirect(
ffi.Pointer<ffi.Char> _plan,
ffi.Pointer<ffi.Char> _provider,
ffi.Pointer<ffi.Char> _email,
ffi.Pointer<ffi.Char> _idempotencyKey,
) {
return _paymentRedirect(_plan, _provider, _email);
return _paymentRedirect(_plan, _provider, _email, _idempotencyKey);
}

late final _paymentRedirectPtr =
Expand All @@ -5708,6 +5717,7 @@ class LanternBindings {
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
)
>
>('paymentRedirect');
Expand All @@ -5717,6 +5727,7 @@ class LanternBindings {
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
ffi.Pointer<ffi.Char>,
)
>();

Expand Down
16 changes: 14 additions & 2 deletions lib/lantern/lantern_platform_service.dart
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Expand Up @@ -651,6 +651,7 @@ class LanternPlatformService implements LanternCoreService {
required BillingType type,
required String planId,
required String email,
required String idempotencyKey,
}) async {
if (!PlatformUtils.isMacOS) {
return left(
Expand All @@ -663,7 +664,12 @@ class LanternPlatformService implements LanternCoreService {
try {
final redirectUrl = await _methodChannel.invokeMethod<String>(
'stripeSubscriptionPaymentRedirect',
{"type": type.name, "planId": planId, "email": email},
{
"type": type.name,
"planId": planId,
"email": email,
"idempotencyKey": idempotencyKey,
},
);
return Right(redirectUrl!);
} catch (e) {
Expand Down Expand Up @@ -758,14 +764,20 @@ class LanternPlatformService implements LanternCoreService {
required String provider,
required String planId,
required String email,
required String idempotencyKey,
}) async {
if (PlatformUtils.isIOS) {
throw UnimplementedError("This not supported on IOS");
}
try {
final redirectUrl = await _methodChannel.invokeMethod<String>(
'paymentRedirect',
{'provider': provider, 'planId': planId, 'email': email},
{
'provider': provider,
'planId': planId,
'email': email,
'idempotencyKey': idempotencyKey,
},
);
return Right(redirectUrl!);
} catch (e, stackTrace) {
Expand Down
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