ios - 通过 Obj-c 查询 REST API 时出现 Azure DocumentDB 间歇性 401 错误

Question

我负责使用 REST API 方案实现 Azure DocumentDB 系统的基于 Objective-C 的 iOS 查询。利用在 github 上找到的代码，特别是 https://github.com/Azure/azure-storage-ios我能够生成一个请求，适本地验证并返回适当的数据......有时。

问题:我间歇性地从服务器收到 401(身份验证失败)错误响应。通过 Node.js 发出相同的请求不会遇到这种行为，所以我认为这是我的 objective-c 实现的问题。

- (NSMutableURLRequest *) RequestWithQuery:(NSString*)query Parameters:(NSArray*)parameters {

NSError* error;
NSDictionary* dictionaryOfBodyContents = @{@"query":query,
                                           @"parameters":parameters};
NSData* body = [NSJSONSerialization dataWithJSONObject:dictionaryOfBodyContents
                                               options:NSJSONWritingPrettyPrinted
                                                 error:&error];

if(error != nil) {
    NSLog(@"AzureRequestWithQueryParameters error generating the body: %@",error);
    return nil;
}

char buffer[30];
struct tm * timeptr;

time_t time = (time_t) [[NSDate date] timeIntervalSince1970];
timeptr = gmtime(&time);
if (!strftime_l(buffer, 30, [@"%a, %d %b %Y %T GMT" UTF8String], timeptr, NULL))
{
    NSException* myException = [NSException
                                exceptionWithName:@"Error in date/time format"
                                reason:@"Unknown"
                                userInfo:nil];
    @throw myException;
}
NSString* date = [NSString stringWithUTF8String:buffer];
// generate auth token
NSString* authorizationToken = [self AuthorizationTokenForTableQueryWithDate:date];

// generate header contents
NSDictionary* dictionaryOfHeaderContents = @{@"authorization":authorizationToken,
                                             @"connection":AZURE_CONNECTION_HEADER_CONNECTION,
                                             @"content-type":AZURE_CONNECTION_HEADER_CONTENTTYPE,
                                             @"content-length":[NSString stringWithFormat:@"%lu",(unsigned long)[body length]],
                                             @"x-ms-version":AZURE_CONNECTION_APIVERSION,
                                             @"x-ms-documentdb-isquery":@"true",
                                             @"x-ms-date":date.lowercaseString,
                                             @"cache-control":@"no-cache",
                                             @"user-agent":AZURE_CONNECTION_HEADER_USERAGENT,
                                             @"accept":@"application/json"};

// generate url contents
NSString* urlString = [NSString stringWithFormat:@"https://%@:%@/%@", AZURE_URL_HOST, AZURE_URL_PORT, AZURE_URL_DOCUMENTS];
NSURL* url = [NSURL URLWithString:urlString];

NSMutableURLRequest* request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:AZURE_CONNECTION_METHOD];
[request setAllHTTPHeaderFields:dictionaryOfHeaderContents];
[request setHTTPBody:body];
return request;
}

- (NSString*) AuthorizationTokenForTableQueryWithDate:(NSString*)date {
//
//  Based on https://msdn.microsoft.com/en-us/library/azure/dd179428.aspx under "Table Service (Shared Key Authentication)"
//
//    generating a authentication token is a Hash-based Message Authentication Code (HMAC) constructed from the request
//      and computed by using the SHA256 algorithm, and then encoded by using Base64 encoding.
//
//    StringToSign =  VERB + "\n" +
//                    Content-MD5 + "\n" +
//                    Content-Type + "\n" +
//                    Date + "\n" +
//                    CanonicalizedHeaders +
//                    CanonicalizedResource;
//
NSString* StringToSign = [NSString stringWithFormat:@"%@\n%@\n%@\n%@\n\n",
                          AZURE_CONNECTION_METHOD.lowercaseString?:@"",
                          AZURE_RESOURCE_TYPE.lowercaseString?:@"",
                          AZURE_URL_COLLECTIONS.lowercaseString?:@"",
                          date.lowercaseString?:@""];

// Generate Key/Message pair
NSData* keyData = [[NSData alloc] initWithBase64EncodedString:AZURE_AUTH_KEY options:NSDataBase64DecodingIgnoreUnknownCharacters];
NSData* messageData = [StringToSign dataUsingEncoding:NSUTF8StringEncoding];

// Encrypt your Key/Message using HMAC SHA256
NSMutableData* HMACData = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
CCHmac(kCCHmacAlgSHA256, keyData.bytes, keyData.length, messageData.bytes, messageData.length, HMACData.mutableBytes);

// Take your encrypted data, and generate a token that Azure likes.
NSString* signature = [HMACData base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
NSString* unencodedToken = [NSString stringWithFormat:@"type=master&ver=1.0&sig=%@",signature];
NSString* authorizationToken = [unencodedToken stringByReplacingOccurrencesOfString:@"&" withString:@"%26"];
authorizationToken = [authorizationToken stringByReplacingOccurrencesOfString:@"=" withString:@"%3D"];

return authorizationToken;
}

如果有人遇到类似的间歇性 401 并且能够解决任何帮助，我们将不胜感激。或者考虑到上述代码的调试步骤的建议，我尝试将时间戳减少几秒钟，类似的间歇性故障。

虽然在失败时简单地重试几次，同时减少秒数会导致 1-2 次重试中得到 200 个响应，但我认为无论如何这都不是一个理想的解决方案。

感谢您的宝贵时间。

更新:失败的原因请看下方Andrew Liu的解释。我已将他的回复标记为答案，下面是更新后的代码片段。

NSString* unencodedToken = [NSString stringWithFormat:@"type=master&ver=1.0&sig=%@",signature];
//    NSString* authorizationToken = [unencodedToken stringByReplacingOccurrencesOfString:@"&" withString:@"%26"];
//    authorizationToken = [authorizationToken stringByReplacingOccurrencesOfString:@"=" withString:@"%3D"];
NSString* authorizationToken = [unencodedToken stringByAddingPercentEncodingWithAllowedCharacters:[[NSCharacterSet characterSetWithCharactersInString:@"&+="] invertedSet]];
return authorizationToken;

Answer 1

401(身份验证失败)通常表示身份验证 token 有问题。

请务必注意，身份验证 token 是 Base64 编码的字符串 - 这意味着它可以包含 + 字符。

数据库服务器期望身份验证 token 中的 + 字符被 url 编码(%2B)...一些但不是所有的 HTTP 客户端会自动编码 HTTP header 你。

我怀疑以下变量的 url 编码或将 + 转换为 %2B 将解决间歇性 401 问题:

NSString* signature = [HMACData base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];