Object Storage Service:Upload a file using a signed URL (C# SDK V1)

Precautions

• In this topic, the public endpoint of the China (Hangzhou) region is used. To access OSS from other Alibaba Cloud services in the same region, use an internal endpoint. For details about supported regions and endpoints, see Regions and endpoints.

• This topic provides an example of how to read access credentials from environment variables. For more information about how to configure access credentials, see Configure access credentials.

• To generate a signed URL for an upload, you must have the oss:PutObject permission. For more information, see Grant custom access policies to a RAM user.

  Note

  When a signed URL is generated, the SDK uses the locally stored key to calculate a signature based on a specific algorithm. The SDK then appends the signature to the URL to ensure its validity and security. These calculation and URL construction operations are performed on the client. No network requests are sent to the server. Therefore, the caller does not need specific permissions to generate the signed URL. However, to ensure that third-party users can perform operations on the resources that are authorized by the signed URL, you must make sure that the entity that calls the API to generate the signed URL is granted the required permissions.

• This topic provides an example of a V4 signed URL. The maximum validity period of a V4 signed URL is 7 days. For more information, see Signature Version 4 (recommended).

• If a signed URL that is generated from the following examples contains a plus sign (+), the URL may be inaccessible. To resolve this issue, replace the plus sign (+) in the URL with %2B.

• To generate a signed URL that uses the HTTPS protocol, set the communication protocol in the Endpoint to HTTPS.

Procedure

The following procedure shows how to use a signed URL with the PUT method to upload a file:

Code examples

1. Generate a signed URL for an upload

   using Aliyun.OSS;
   using Aliyun.OSS.Common;
   // Specify the Endpoint for the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Endpoint to https://oss-cn-hangzhou.aliyuncs.com.
   var endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
   // Obtain access credentials from environment variables. Before you run this code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
   var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
   var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
   // Specify the bucket name, for example, examplebucket.
   var bucketName = "examplebucket";
   // Specify the full path of the object. The full path does not include the bucket name. For example, exampledir/exampleobject.txt.
   var objectName = "exampledir/exampleobject.txt";
   var objectContent = "More than just cloud.";
   // Specify the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the region to cn-hangzhou.
   const string region = "cn-hangzhou";
   
   // Create a ClientConfiguration instance and modify the default parameters as needed.
   var conf = new ClientConfiguration();
   
   // Set the signature version to V4.
   conf.SignatureVersion = SignatureVersion.V4;
   
   // Create an OssClient instance.
   var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
   client.SetRegion(region);
   try
   {
       // Generate a signed URL.
       var generatePresignedUriRequest = new GeneratePresignedUriRequest(bucketName, objectName, SignHttpMethod.Put)
       {
           // Set the expiration time of the signed URL. The default value is 3600 seconds.
           Expiration = DateTime.Now.AddHours(1),
       };
       var signedUrl = client.GeneratePresignedUri(generatePresignedUriRequest);
   }
   catch (OssException ex)
   {
       Console.WriteLine("Failed with error code: {0}; Error info: {1}. \nRequestID:{2}\tHostID:{3}",
           ex.ErrorCode, ex.Message, ex.RequestId, ex.HostId);
   }
   catch (Exception ex)
   {
       Console.WriteLine("Failed with error info: {0}", ex.Message);
   }

2. Another user uploads a file using the presigned URL for the PUT request.

   curl

   curl -X PUT -T /path/to/local/file "https://exampleobject.oss-cn-hangzhou.aliyuncs.com/exampleobject.txt?x-oss-date=20241112T083238Z&x-oss-expires=3599&x-oss-signature-version=OSS4-HMAC-SHA256&x-oss-credential=LTAI****************%2F20241112%2Fcn-hangzhou%2Foss%2Faliyun_v4_request&x-oss-signature=ed5a******************************************************"

   Java

   import org.apache.http.HttpEntity;
   import org.apache.http.client.methods.CloseableHttpResponse;
   import org.apache.http.client.methods.HttpPut;
   import org.apache.http.entity.FileEntity;
   import org.apache.http.impl.client.CloseableHttpClient;
   import org.apache.http.impl.client.HttpClients;
   import java.io.*;
   import java.net.URL;
   import java.util.*;
   
   public class SignUrlUpload {
       public static void main(String[] args) throws Throwable {
           CloseableHttpClient httpClient = null;
           CloseableHttpResponse response = null;
   
           // Replace <signedUrl> with the authorized URL.
           URL signedUrl = new URL("<signedUrl>");
   
           // Specify the full path of the local file. If you do not specify a local path, the file is uploaded from the project path of the sample program by default.
           String pathName = "C:\\Users\\demo.txt";
   
           try {
               HttpPut put = new HttpPut(signedUrl.toString());
               System.out.println(put);
               HttpEntity entity = new FileEntity(new File(pathName));
               put.setEntity(entity);
               httpClient = HttpClients.createDefault();
               response = httpClient.execute(put);
   
               System.out.println("Status code returned for the upload:"+response.getStatusLine().getStatusCode());
               if(response.getStatusLine().getStatusCode() == 200){
                   System.out.println("Upload successful using network library.");
               }
               System.out.println(response.toString());
           } catch (Exception e){
               e.printStackTrace();
           } finally {
               response.close();
               httpClient.close();
           }
       }
   }       

   Go

   package main
   
   import (
   	"fmt"
   	"io"
   	"net/http"
   	"os"
   )
   
   func uploadFile(signedUrl, filePath string) error {
   	// Open the file.
   	file, err := os.Open(filePath)
   	if err != nil {
   		return fmt.Errorf("Unable to open file: %w", err)
   	}
   	defer file.Close()
   
   	// Create a new HTTP client.
   	client := &http.Client{}
   
   	// Create a PUT request.
   	req, err := http.NewRequest("PUT", signedUrl, file)
   	if err != nil {
   		return fmt.Errorf("Failed to create request: %w", err)
   	}
   
   	// Send the request.
   	resp, err := client.Do(req)
   	if err != nil {
   		return fmt.Errorf("Failed to send request: %w", err)
   	}
   	defer resp.Body.Close()
   
   	// Read the response.
   	body, err := io.ReadAll(resp.Body)
   	if err != nil {
   		return fmt.Errorf("Failed to read response: %w", err)
   	}
   
   	fmt.Printf("Status code returned for the upload: %d\n", resp.StatusCode)
   	if resp.StatusCode == 200 {
   		fmt.Println("Upload successful using network library.")
   	}
   	fmt.Println(string(body))
   
   	return nil
   }
   
   func main() {
   	// Replace <signedUrl> with the authorized URL.
   	signedUrl := "<signedUrl>"
   
   	// Specify the full path of the local file. If you do not specify a local path, the file is uploaded from the project path of the sample program by default.
   	filePath := "C:\\Users\\demo.txt"
   
   	err := uploadFile(signedUrl, filePath)
   	if err != nil {
   		fmt.Println("An error occurred:", err)
   	}
   }
   

   python

   import requests
   
   def upload_file(signed_url, file_path):
       try:
           # Open the file.
           with open(file_path, 'rb') as file:
               # Send a PUT request to upload the file.
               response = requests.put(signed_url, data=file)
        
           print(f"Status code returned for the upload: {response.status_code}")
           if response.status_code == 200:
               print("Upload successful using network library.")
           print(response.text)
    
       except Exception as e:
           print(f"An error occurred: {e}")
   
   if __name__ == "__main__":
       # Replace <signedUrl> with the authorized URL.
       signed_url = "<signedUrl>"
       
       // Specify the full path of the local file. If you do not specify a local path, the file is uploaded from the project path of the sample program by default.
       file_path = "C:\\Users\\demo.txt"
   
       upload_file(signed_url, file_path)
   

   Node.js

   const fs = require('fs');
   const axios = require('axios');
   
   async function uploadFile(signedUrl, filePath) {
       try {
           // Create a read stream.
           const fileStream = fs.createReadStream(filePath);
           
           // Send a PUT request to upload the file.
           const response = await axios.put(signedUrl, fileStream, {
               headers: {
                   'Content-Type': 'application/octet-stream' // Adjust the Content-Type as needed.
               }
           });
   
           console.log(`Status code returned for the upload: ${response.status}`);
           if (response.status === 200) {
               console.log('Upload successful using network library.');
           }
           console.log(response.data);
       } catch (error) {
           console.error(`An error occurred: ${error.message}`);
       }
   }
   
   // Main function.
   (async () => {
       // Replace <signedUrl> with the authorized URL.
       const signedUrl = '<signedUrl>';
       
       // Specify the full path of the local file. If you do not specify a local path, the file is uploaded from the project path of the sample program by default.
       const filePath = 'C:\\Users\\demo.txt';
   
       await uploadFile(signedUrl, filePath);
   })();

   browser.js

   Important

   If you encounter a 403 signature mismatch error when you use Browser.js to upload a file, it is usually because the browser automatically adds the Content-Type request header, but this header was not specified when the presigned URL was generated. This causes a signature verification failure. To resolve this issue, you must specify the Content-Type request header when you generate the presigned URL.

   <!DOCTYPE html>
   <html lang="en">
   <head>
       <meta charset="UTF-8">
       <meta name="viewport" content="width=device-width, initial-scale=1.0">
       <title>File Upload Example</title>
   </head>
   <body>
       <h1>File Upload Example</h1>
   
       <!-- Select a file -->
       <input type="file" id="fileInput" />
       <button id="uploadButton">Upload File</button>
   
       <script>
           // Replace this with the presigned URL generated in Step 1.
           const signedUrl = "<signedUrl>"; 
   
   
           document.getElementById('uploadButton').addEventListener('click', async () => {
               const fileInput = document.getElementById('fileInput');
               const file = fileInput.files[0];
   
               if (!file) {
                   alert('Please select a file to upload.');
                   return;
               }
   
               try {
                   await upload(file, signedUrl);
                   alert('File uploaded successfully!');
               } catch (error) {
                   console.error('Error during upload:', error);
                   alert('Upload failed: ' + error.message);
               }
           });
   
           /**
            * Upload the file to OSS.
            * @param {File} file - The file to upload.
            * @param {string} presignedUrl - The presigned URL.
            */
           const upload = async (file, presignedUrl) => {
               const response = await fetch(presignedUrl, {
                   method: 'PUT',
                   body: file,  // Upload the entire file directly.
               });
   
               if (!response.ok) {
                   throw new Error(`Upload failed, status: ${response.status}`);
               }
   
               console.log('File uploaded successfully');
           };
       </script>
   </body>
   </html>

   C#

   using System.Net.Http.Headers;
   
   // Specify the full path of the local file. If you do not specify a local path, the file is uploaded from the project path of the sample program by default.
   var filePath = "C:\\Users\\demo.txt";
   // Replace <signedUrl> with the authorized URL.
   var presignedUrl = "<signedUrl>";
   
   // Create an HTTP client and open the local file stream.
   using var httpClient = new HttpClient(); 
   using var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
   using var content = new StreamContent(fileStream);
               
   // Create a PUT request.
   var request = new HttpRequestMessage(HttpMethod.Put, presignedUrl);
   request.Content = content;
   
   // Send the request.
   var response = await httpClient.SendAsync(request);
   
   // Process the response.
   if (response.IsSuccessStatusCode)
   {
       Console.WriteLine($"Upload successful! Status code: {response.StatusCode}");
       Console.WriteLine("Response headers:");
       foreach (var header in response.Headers)
       {
           Console.WriteLine($"{header.Key}: {string.Join(", ", header.Value)}");
       }
   }
   else
   {
       string responseContent = await response.Content.ReadAsStringAsync();
       Console.WriteLine($"Upload failed! Status code: {response.StatusCode}");
       Console.WriteLine("Response content: " + responseContent);
   }

   C++

   #include <iostream>
   #include <fstream>
   #include <curl/curl.h>
   
   void uploadFile(const std::string& signedUrl, const std::string& filePath) {
       CURL *curl;
       CURLcode res;
   
       curl_global_init(CURL_GLOBAL_DEFAULT);
       curl = curl_easy_init();
   
       if (curl) {
           // Set the URL.
           curl_easy_setopt(curl, CURLOPT_URL, signedUrl.c_str());
   
           // Set the request method to PUT.
           curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
   
           // Open the file.
           FILE *file = fopen(filePath.c_str(), "rb");
           if (!file) {
               std::cerr << "Unable to open file: " << filePath << std::endl;
               return;
           }
   
           // Get the file size.
           fseek(file, 0, SEEK_END);
           long fileSize = ftell(file);
           fseek(file, 0, SEEK_SET);
   
           // Set the file size.
           curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, (curl_off_t)fileSize);
   
           // Set the input file handle.
           curl_easy_setopt(curl, CURLOPT_READDATA, file);
   
           // Execute the request.
           res = curl_easy_perform(curl);
   
           if (res != CURLE_OK) {
               std::cerr << "curl_easy_perform() failed: " << curl_easy_strerror(res) << std::endl;
           } else {
               long httpCode = 0;
               curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &httpCode);
               std::cout << "Status code returned for the upload: " << httpCode << std::endl;
   
               if (httpCode == 200) {
                   std::cout << "Upload successful using network library." << std::endl;
               }
           }
   
           // Close the file.
           fclose(file);
   
           // Clean up.
           curl_easy_cleanup(curl);
       }
   
       curl_global_cleanup();
   }
   
   int main() {
       // Replace <signedUrl> with the authorized URL.
       std::string signedUrl = "<signedUrl>";
   
       // Specify the full path of the local file. If you do not specify a local path, the file is uploaded from the project path of the sample program by default.
       std::string filePath = "C:\\Users\\demo.txt";
   
       uploadFile(signedUrl, filePath);
   
       return 0;
   }
   

   Android

   package com.example.signurlupload;
   
   import android.os.AsyncTask;
   import android.util.Log;
   
   import java.io.DataOutputStream;
   import java.io.FileInputStream;
   import java.io.IOException;
   import java.net.HttpURLConnection;
   import java.net.URL;
   
   public class SignUrlUploadActivity {
   
       private static final String TAG = "SignUrlUploadActivity";
   
       public void uploadFile(String signedUrl, String filePath) {
           new UploadTask().execute(signedUrl, filePath);
       }
   
       private class UploadTask extends AsyncTask<String, Void, String> {
   
           @Override
           protected String doInBackground(String... params) {
               String signedUrl = params[0];
               String filePath = params[1];
   
               HttpURLConnection connection = null;
               DataOutputStream dos = null;
               FileInputStream fis = null;
   
               try {
                   URL url = new URL(signedUrl);
                   connection = (HttpURLConnection) url.openConnection();
                   connection.setRequestMethod("PUT");
                   connection.setDoOutput(true);
                   connection.setRequestProperty("Content-Type", "application/octet-stream");
   
                   fis = new FileInputStream(filePath);
                   dos = new DataOutputStream(connection.getOutputStream());
   
                   byte[] buffer = new byte[1024];
                   int length;
   
                   while ((length = fis.read(buffer)) != -1) {
                       dos.write(buffer, 0, length);
                   }
   
                   dos.flush();
                   dos.close();
                   fis.close();
   
                   int responseCode = connection.getResponseCode();
                   Log.d(TAG, "Status code returned for the upload: " + responseCode);
   
                   if (responseCode == 200) {
                       Log.d(TAG, "Upload successful using network library.");
                   }
   
                   return "Upload complete. Status code: " + responseCode;
   
               } catch (IOException e) {
                   e.printStackTrace();
                   return "Upload failed: " + e.getMessage();
               } finally {
                   if (connection != null) {
                       connection.disconnect();
                   }
               }
           }
   
           @Override
           protected void onPostExecute(String result) {
               Log.d(TAG, result);
           }
       }
   
       public static void main(String[] args) {
           SignUrlUploadActivity activity = new SignUrlUploadActivity();
           // Replace <signedUrl> with the authorized URL.
           String signedUrl = "<signedUrl>";
           // Specify the full path of the local file. If you do not specify a local path, the file is uploaded from the project path of the sample program by default.
           String filePath = "C:\\Users\\demo.txt";
           activity.uploadFile(signedUrl, filePath);
       }
   }
   

FAQ