苹果提供了两份关于收据验证的文档，其中似乎存在矛盾的陈述。
在"验证商店收据"中：
注意：在iOS上，商店收据的内容和格式是私有的且可能会更改。您的应用程序不应尝试直接解析收据数据。
然而，在"iOS应用内购买收据验证"的示例代码中，商店收据被解析并验证，作为一种安全漏洞的“缓解策略”：
// Check the validity of the receipt. If it checks out then also ensure the transaction is something
// we haven't seen before and then decode and save the purchaseInfo from the receipt for later receipt validation.
- (BOOL)isTransactionAndItsReceiptValid:(SKPaymentTransaction *)transaction
{
if (!(transaction && transaction.transactionReceipt && [transaction.transactionReceipt length] > 0))
{
// Transaction is not valid.
return NO;
}
// Pull the purchase-info out of the transaction receipt, decode it, and save it for later so
// it can be cross checked with the verifyReceipt.
NSDictionary *receiptDict = [self dictionaryFromPlistData:transaction.transactionReceipt];
NSString *transactionPurchaseInfo = [receiptDict objectForKey:@"purchase-info"];
NSString *decodedPurchaseInfo = [self decodeBase64:transactionPurchaseInfo length:nil];
NSDictionary *purchaseInfoDict = [self dictionaryFromPlistData:[decodedPurchaseInfo dataUsingEncoding:NSUTF8StringEncoding]];
NSString *transactionId = [purchaseInfoDict objectForKey:@"transaction-id"];
NSString *purchaseDateString = [purchaseInfoDict objectForKey:@"purchase-date"];
NSString *signature = [receiptDict objectForKey:@"signature"];
// Convert the string into a date
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss z"];
NSDate *purchaseDate = [dateFormat dateFromString:[purchaseDateString stringByReplacingOccurrencesOfString:@"Etc/" withString:@""]];
if (![self isTransactionIdUnique:transactionId])
{
// We've seen this transaction before.
// Had [transactionsReceiptStorageDictionary objectForKey:transactionId]
// Got purchaseInfoDict
return NO;
}
// Check the authenticity of the receipt response/signature etc.
BOOL result = checkReceiptSecurity(transactionPurchaseInfo, signature,
(__bridge CFDateRef)(purchaseDate));
if (!result)
{
return NO;
}
// Ensure the transaction itself is legit
if (![self doTransactionDetailsMatchPurchaseInfo:transaction withPurchaseInfo:purchaseInfoDict])
{
return NO;
}
// Make a note of the fact that we've seen the transaction id already
[self saveTransactionId:transactionId];
// Save the transaction receipt's purchaseInfo in the transactionsReceiptStorageDictionary.
[transactionsReceiptStorageDictionary setObject:purchaseInfoDict forKey:transactionId];
return YES;
}
如果我理解正确，如果我验证收据，当苹果决定更改收据格式时，我的应用程序可能会停止工作。
而如果我不验证收据，我就没有遵循苹果的“缓解策略”，我的应用程序就容易遭受攻击。
无论我怎么做都会受到惩罚。我是否漏掉了什么？