Object Storage Service:Authorize access using OSS SDK for Ruby

Usage notes

• When you use an OSS SDK to generate a presigned URL, the OSS SDK uses a specific algorithm and the key information stored in the local computer to calculate a signature and adds the signature to a URL to ensure the validity and security of it. The operations performed to calculate the signature and construct the URL are completed on the client. You do not need to send requests to the server over the network. Therefore, you do not have to be granted specific permissions to generate a presigned URL. However, to prevent third-party users from being unable to perform the operation authorized by the presigned URL, you must have the corresponding permission.

  For example, to generate a presigned URL for an object download or preview, you must have the oss:PutObject permission.

• You can generate a presigned URL and provide the URL to a visitor for temporary access. When you generate a presigned URL, you can specify the validity period of the URL to limit the period of time during which the visitor can access specific data.

• To generate a presigned URL that is used to access resources over HTTPS, set the protocol in the endpoint to HTTPS.

• The presigned URL generated by using the following sample code may contain a plus sign (+). In this case, replace the plus sign (+) in the URL with %2B. Otherwise, the presigned URL may not be used to access the object as expected.

Generate a presigned URL and use it to download an object

1. Generate a presigned URL to download an object.

   require 'aliyun/oss'
   
   client = Aliyun::OSS::Client.new(
     # In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. 
     endpoint: 'https://oss-cn-hangzhou.aliyuncs.com',
     # Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. 
     access_key_id: ENV['OSS_ACCESS_KEY_ID'],
     access_key_secret: ENV['OSS_ACCESS_KEY_SECRET']
   )
   # Specify the name of the bucket. Example: examplebucket. 
   bucket = client.get_bucket('examplebucket')
   
   # Generate a presigned URL that is used to download the object and set its validity period to 3,600 seconds. 
   puts bucket.object_url('my-object', true, 3600)

2. Download an object by using a signed URL on mobile devices or browsers.
   Android-Java

   // Enter the generated signed URL. 
   String url = "";
   OkHttpClient client = new OkHttpClient();
   // Use the signed URL to download the object. 
   Request getRequest = new Request.Builder()
           .url(url)
           .get()
           .build();
   client.newCall(getRequest).enqueue(new Callback() {
       @Override
       public void onFailure(Call call, IOException e) {
           e.printStackTrace();
       }
   
       @Override
       public void onResponse(Call call, Response response) throws IOException {
           if (response.code() == 203 || response.code() >= 300) {
               Log.d("download", "fail");
               Log.d("download", response.body().string());
               return;
           }
           // The object is downloaded. 
           InputStream inputStream = response.body().byteStream();
   
           byte[] buffer = new byte[2048];
           int len;
   
           while ((len = inputStream.read(buffer)) != -1) {
               // Process the downloaded data. For example, display the image or perform a write operation on the object. 
           }
       }
   });

   Object C

   // Use the signed URL to download the object. 
   NSURL * url = [NSURL URLWithString:urlString];
   NSURLRequest * request = [NSURLRequest requestWithURL:url];
   NSURLSession * session = [NSURLSession sharedSession];
   NSURLSessionTask * sessionTask = [session dataTaskWithRequest:request
                                               completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
       if (error) {
           NSLog(@"download error: %@", error);
           return;
       } else if (((NSHTTPURLResponse*)response).statusCode == 203 ||
                  ((NSHTTPURLResponse*)response).statusCode >= 300) {
           NSString *body = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
           NSLog(@"download error: %@", body);
           return;
       }
       NSLog(@"download success");
   }];
   [sessionTask resume];

   JavaScript

   // You can also use the download attribute in the <a> tag of an HTML page or window.open of a web API to obtain an object URL.