阿里云函数计算签名认证（iOS实现细节备注）

1、使用第三方库 AFNetworking进行网络请求。
2、阿里云函数计算签名认证文档
3、文档中添加 CanonicalizedFCHeaders 可以不用添加，CanonicalizedResource如何没有设置Path，在末尾加入“/”就可以了。
4、主要还是 hmac-sha256 签名认证，在实现过程中转base64的问题。
下面则是实现代码：

+ (AFHTTPSessionManager *)httpSessionManager:(NSString *)url{AFHTTPSessionManager *sessionManager = [[AFHTTPSessionManager alloc] initWithBaseURL:[NSURL URLWithString:url]];sessionManager.requestSerializer = [AFJSONRequestSerializer serializer];sessionManager.responseSerializer = [AFJSONResponseSerializer serializer];sessionManager.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"application/json", nil];[sessionManager.requestSerializer setValue:[YTDWindingCalculatorHttp aliSignature:sessionManager] forHTTPHeaderField:@"Authorization"];return sessionManager;
}+ (NSString *)aliSignature:(AFHTTPSessionManager *)sessionManager{NSString *accessKeyID = @"xxxxxx";NSString *accessKeySecret = @"xxxx";NSString *authorization = [NSString stringWithFormat:@"FC %@:",accessKeyID];NSMutableArray *signatureArray = [NSMutableArray array];[signatureArray addObject:@"POST"];[signatureArray addObject:@""];[signatureArray addObject:@"application/json"];NSString *date = [YTDWindingCalculatorHttp rfc1123String];[signatureArray addObject:date];[signatureArray addObject:@"/\n"];//请求头添加content-type 和 date[sessionManager.requestSerializer setValue:sessionManager.responseSerializer.acceptableContentTypes.allObjects.firstObject forHTTPHeaderField:@"content-type"];[sessionManager.requestSerializer setValue:date forHTTPHeaderField:@"date"];NSString *signature = [signatureArray componentsJoinedByString:@"\n"];signature = [YTDWindingCalculatorHttp hmac:signature withKey:accessKeySecret];authorization = [NSString stringWithFormat:@"%@%@",authorization,signature];return authorization;
}+ (NSString *)hmac:(NSString *)content withKey:(NSString *)secret{const char *cKey  = [secret cStringUsingEncoding:NSUTF8StringEncoding];const char *cData = [content cStringUsingEncoding:NSUTF8StringEncoding];// 有可能有中文 所以用NSUTF8StringEncoding -> NSASCIIStringEncodingunsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];CCHmac(kCCHmacAlgSHA256, cKey, strlen(cKey), cData, strlen(cData), cHMAC);NSData *HMACData = [NSData dataWithBytes:cHMAC length:sizeof(cHMAC)];NSData *base64Data = [HMACData base64EncodedDataWithOptions:NSDataBase64Encoding64CharacterLineLength];return [[NSString alloc] initWithData:base64Data encoding:NSUTF8StringEncoding];
}+ (NSString *)rfc1123String{time_t date = (time_t)[[NSDate date] timeIntervalSince1970];struct tm timeinfo;gmtime_r(&date, &timeinfo);char buffer[32];size_t ret = strftime_l(buffer, sizeof(buffer), "%a, %d %b %Y %H:%M:%S GMT", &timeinfo, NULL);if (ret) {return @(buffer);} else {return nil;}
}