Ruby

Step 1: Configure the application server

1. Download the application server source code that is in Ruby.
2. Ubuntu 16.04 is used in the example. Decompress the source code to the /home/aliyun/aliyun-oss-appserver-ruby directory.
3. Go to the directory. Open the appserver.rb file that contains the source code. Modify the following snippet:

   # Enter your AccessKey ID.
   $access_key_id = '<yourAccessKeyId>'
   
   # Enter your AccessKey secret.
   $access_key_secret = '<yourAccessKeySecret>'
   
   # Set $host to a value that is in the format of bucketname.endpoint.
   $host = 'https://bucket-name.oss-cn-hangzhou.aliyuncs.com';
   
   # Set the URL of the server to which an upload callback request is sent. Replace the IP address and port number with your actual information.
   $callback_url = "http://88.88.88.88:8888";
   
   # Specify the prefix for the name of the object you want to upload.
   $upload_dir = 'user-dir-prefix/'

   • $access_key_id: Enter your AccessKey ID.
   • $access_key_secret: Enter your AccessKey secret.
   • $host: The format is https://bucketname.endpoint. Example: https://bucket-name.oss-cn-hangzhou.aliyuncs.com. For more information about endpoints, see the "Endpoint" section in Terms.
   • $callback_url: Set the URL of the server to which an upload callback request is sent. This URL is used to communicate between the application server and OSS. After an object is uploaded, OSS sends the object upload information to the application server by using this URL. In this example, set the URL to $callback_url="http://11.22.33.44:1234";.
   • $upload_dir: Specify the prefix for the name of the object. You can also leave this parameter unspecified.

Step 2: Configure the client

1. Download the client source code.
2. Decompress the package to a directory. The D:\aliyun\aliyun-oss-appserver-js directory is used in the example.
3. Go to the directory. Open the upload.js file. Find the following code:

   // serverUrl specifies the URL of the application server used to obtain information such as the signature and policy. Replace the IP address and port number with your actual information.
   serverUrl = 'http://88.88.88.88:8888'

4. Set severUrl to the URL of the application server. In this example, specify serverUrl = 'http://11.22.33.44:1234'.

Step 3: Modify CORS configurations

When you use form upload to upload data from the client to OSS, the client includes the Origin header in the request and sends the request to OSS by using the browser. OSS verifies the request message that includes the Origin header for cross-origin resource sharing (CORS) verification. To use the POST method, configure CORS rules for a bucket.

1. Log on to the OSS console.
2. Click Buckets, and then click the name of the target bucket.
3. Choose Access Control > Cross-Origin Resource Sharing (CORS). In the Cross-Origin Resource Sharing (CORS) section, click Configure.
4. Click Create Rule. The following figure shows the configurations of a rule.
   Note For data security reasons, enter a required domain name in the Sources field. For more information about CORS configurations, see Configure CORS rules.

Step 4: Send an upload callback request

1. Start the application server.
   In the /home/aliyun/aliyun-oss-appserver-ruby directory, run the ruby appserver.rb 11.22.33.44 1234 command to start the application server.

   Note Replace the IP address and port number with those of the application server you configured.
2. Start the client.
   On the PC, open the index.html file in the directory that contains the client source code.
   Notice The index.html file may be incompatible with Internet Explorer 10 or earlier. If you encounter any problems when you use Internet Explorer 10 or earlier, you must perform debugging.
3. Upload an object.
   Click Select File. Select the file of a specified type. Click Upload. After the object is uploaded, the content returned by the callback server is displayed.

Core code analysis of the application server

The source code of the application server is used to implement signature-based upload and upload callback.

• Signature-based upload

  During signature-based upload, the application server responds to the GET message that is sent from the client. An example of the snippet:

  def get_token()
      expire_syncpoint = Time.now.to_i + $expire_time
  
      expire = Time.at(expire_syncpoint).utc.iso8601()
      response.headers['expire'] = expire
  
      policy_dict = {}
      condition_arrary = Array.new
      array_item = Array.new
      array_item.push('starts-with')
      array_item.push('$key')
      array_item.push($upload_dir)
      condition_arrary.push(array_item)
      policy_dict["conditions"] = condition_arrary
      policy_dict["expiration"] = expire
      policy = hash_to_jason(policy_dict)
      policy_encode = Base64.strict_encode64(policy).chomp;
      h = OpenSSL::HMAC.digest('sha1', $access_key_secret, policy_encode)
      hs = Digest::MD5.hexdigest(h)
      sign_result = Base64.strict_encode64(h).strip()
  
      callback_dict = {}
      callback_dict['callbackBodyType'] = 'application/x-www-form-urlencoded';
      callback_dict['callbackBody'] = 'filename=${object}&size=${size}&mimeType=${mimeType}&height=${imageInfo.height}&width=${imageInfo.width}';
      callback_dict['callbackUrl'] = $callback_url;
      callback_param = hash_to_jason(callback_dict)
      base64_callback_body = Base64.strict_encode64(callback_param);
  
      token_dict = {}
      token_dict['accessid'] = $access_key_id
      token_dict['host'] = $host
      token_dict['policy'] = policy_encode
      token_dict['signature'] = sign_result 
      token_dict['expire'] = expire_syncpoint
      token_dict['dir'] = $upload_dir
      token_dict['callback'] = base64_callback_body
      response.headers["Access-Control-Allow-Methods"] = "POST"
      response.headers["Access-Control-Allow-Origin"] = "*"
      result = hash_to_jason(token_dict)
  
      result
  end
  
  get '/*' do
    puts "********************* GET "
    get_token()
  end

• Upload callback

  During upload callback, the application server responds to the POST message that is sent from OSS. An example of the snippet:

  post '/*' do
    puts "********************* POST"
    pub_key_url = Base64.decode64(get_header('x-oss-pub-key-url'))
    pub_key = get_public_key(pub_key_url)
    rsa = OpenSSL::PKey::RSA.new(pub_key)
  
    authorization = Base64.decode64(get_header('authorization'))
    req_body = request.body.read
    if request.query_string.empty? then
      auth_str = CGI.unescape(request.path) + "\n" + req_body
    else
      auth_str = CGI.unescape(request.path) + '?' + request.query_string + "\n" + req_body
    end
  
    valid = rsa.public_key.verify(
      OpenSSL::Digest::MD5.new, authorization, auth_str)
  
    if valid
      #body({'Status' => 'OK'}.to_json)
      body(hash_to_jason({'Status' => 'OK'}))
    else
      halt 400, "Authorization failed!"
    end
  end

  For more information, see the "(Optional) Step 4: Sign the callback request" section in Callback of the OSS API Reference.