Object Storage Service:Authorize access (Ruby SDK)

Notes

• When an SDK generates a presigned URL, it uses locally stored key information to calculate a signature based on a specific algorithm. The SDK then appends this signature to the URL to ensure its validity and security. This process of calculating the signature and constructing the URL is completed on the client and does not involve network requests. Therefore, the caller does not need specific permissions to generate the presigned URL. However, to ensure that third-party users can perform the intended operations on the resources using the presigned URL, you must make sure that the identity used to generate the URL has the required permissions.

  For example, to download or preview a file using a presigned URL, the oss:GetObject permission is required.

• 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 a file

1. Generate a presigned URL for downloading a file.

   require 'aliyun/oss'
   
   client = Aliyun::OSS::Client.new(
     # The China (Hangzhou) endpoint is used as an example. Specify the endpoint based on your actual region.
     endpoint: 'https://oss-cn-hangzhou.aliyuncs.com',
     # Obtain access credentials from environment variables. Before you run this sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set.
     access_key_id: ENV['OSS_ACCESS_KEY_ID'],
     access_key_secret: ENV['OSS_ACCESS_KEY_SECRET']
   )
   # Specify the bucket name. For example, examplebucket.
   bucket = client.get_bucket('examplebucket')
   
   # Generate a presigned URL and set its validity period to 1 hour (3600 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.