Generating Pre-Signed URL

Last updated: 2024-02-02 17:35:19

Overview
The JavaScript SDK provides the API for getting an object URL and the pre-signed URL for a request. 
Note: 
You are advised to use a temporary key to generate pre-signed URLs for the security of your requests such as uploads and downloads. When you apply for a temporary key, follow the Principle of Least Privilege to avoid leaking resources besides your buckets and objects. Note that the action for applying for a temporary key needs to be added with the "name/cos:GetObject" permission.
If you need to use a permanent key to generate a pre-signed URL, you are advised to limit the permission of the permanent key to uploads and downloads only to avoid risks.
Signature Calculation
In all COS XML API requests, the authentication credential Authorization is required for all operations on private resources for COS to determine whether a request is valid.
There are two ways to use the authentication credential:
1. Put it in the header parameter; field name: authorization.
2. Put it in the URL parameter; field name: sign.
The COS.getAuthorization method is used to calculate the authentication credential (Authorization), which is the signing information used to verify the validity of the request.
Note: 
 We recommend you use this method only for frontend debugging but not in actual projects, as it may disclose keys.
Sample code
Obtain the authentication credential for object download:
// Log in to https://console.tencentcloud.com/cam/capi to check and manage the SecretId and SecretKey of your project.
var Authorization = COS.getAuthorization({
  SecretId: 'SECRETID', // User `SecretId`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1.
  SecretKey: 'SECRETKEY', // User `SecretKey`. We recommend you use a sub-account key and follow the principle of least privilege to reduce risks. For information about how to obtain a sub-account key, visit https://www.tencentcloud.com/document/product/598/37140?from_cn_redirect=1.
  Method: 'get',
  Key: 'exampleobject',
  Expires: 60,
  Query: {},
  Headers: {},
});
Field description
Parameter
Description
Type
Required
SecretId
Your SecretId.
String
Yes
SecretKey
Your SecretKey.
String
Yes
Method
HTTP request method, such as GET, POST, DELETE, or HEAD.
String
Yes
Key
Object key (object name) is the unique ID of an object in a bucket. If the request operation is to be performed on a file, this parameter is required and should be a filename. If the operation is on a bucket, this parameter should be left empty.
String
No
Query
Request parameters to be included in the signature in the format of {key: 'val'}
Object
No
Headers
Request headers to be included in the signature in the format of {key: 'val'}
Object
No
Expires
Signature expiration time in seconds. Default value: 900.
Number
No
Return value description
The return value is the calculated authentication credential string authorization.
Getting a Pre-signed Request URL
Download request samples
Sample 1. Get an object URL without a signature
var url = cos.getObjectUrl({
  Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
  Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
  Key: 'Profile photo.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
  Sign: false,
});
Sample 2. Get a signed object URL
var url = cos.getObjectUrl({
  Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
  Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
  Key: 'Profile photo.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
});
Sample 3. Get a signed URL through callback
Note: 
 If the signing process is asynchronous, you need to get the signed URL through a callback.
cos.getObjectUrl(
  {
    Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
    Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
    Key: 'Profile photo.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
    Sign: false,
  },
  function (err, data) {
    console.log(err || data.Url);
  }
);
Sample 4. Specify the validity period of a link
cos.getObjectUrl(
  {
    Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
    Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
    Key: 'Profile photo.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
    Sign: true,
    Expires: 3600, // Unit: second
  },
  function (err, data) {
    console.log(err || data.Url);
  }
);
Sample 5. Get the object URL and download the object
cos.getObjectUrl(
  {
    Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
    Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
    Key: 'Profile photo.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
    Sign: true,
  },
  function (err, data) {
    if (err) return console.log(err);
    var downloadUrl =
      data.Url +
      (data.Url.indexOf('?') > -1 ? '&' : '?') +
      'response-content-disposition=attachment'; // Add the parameter for a forced download
    /* The filename can be concatenated to rename the object during download */
    /* downloadUrl += ';filename=myname'; */
    // (The window.open() mode is recommended.) This opens the URL in a new window. If you need to open the URL in the current window, you can use the hidden iframe for download, or use the <a> tag download attribute.
    window.open(downloadUrl);
  }
);
Sample 6. Generate the pre-signed URL with the signature containing Query and Header
cos.getObjectUrl(
  {
    Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
    Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
    Key: 'Profile photo.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
    Sign: true,
    /* The HTTP request parameters passed in should be the same as those of the actual request. This can prevent users from tampering with the HTTP request parameters. */
    Query: {
      'imageMogr2/thumbnail/200x/': '',
    },
    /* The HTTP request headers passed in should be included in the actual request. This can prevent users from tampering with the HTTP request headers that are signed here. */
    Headers: {
      host: 'xxx', /* Specified host for access. Error code 403 will be reported for access by a non-specified host. */
    },
  },
  function (err, data) {
    console.log(err || data.Url);
  }
);
Upload request samples
Sample 1. Get a pre-signed URL for Put Object upload
cos.getObjectUrl(
  {
    Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
    Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
    Key: 'Profile photo.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
    Method: 'PUT',
    Sign: true,
  },
  function (err, data) {
    if (err) return console.log(err);
    console.log(data.Url);
﻿
    /* After the URL is obtained, the object can be uploaded in the frontend using AJAX. */
    var xhr = new XMLHttpRequest();
    xhr.open('PUT', data.Url, true); /* `PUT` corresponds to the `Method` entered in `getObjectUrl` */
    xhr.onload = function (e) {
      console.log('Uploaded successfully', xhr.status, xhr.statusText);
    };
    xhr.onerror = function (e) {
      console.log('Upload failed', xhr.status, xhr.statusText);
    };
    xhr.send(file); /* "file" is the object to upload. */
  }
);
Field description
Parameter
Description
Type
Required
Bucket
Bucket name in the format of BucketName-APPID.
String
Yes
Region
Bucket region. For the enumerated values, see Regions and Access Endpoints.
String
Yes
Key
Object key (object name) is the unique ID of an object in a bucket. If the request operation is to be performed on a file, this parameter is required and should be a filename. If the operation is on a bucket, this parameter should be left empty.
String
Yes
Sign
Whether to return a signed URL. Default value: true.
Boolean
No
Protocol
Valid values: http: (default value), https:.
String
No
Domain
Bucket access domain name. Default value: {BucketName-APPID}.cos.{Region}.myqcloud.com.
String
No
Method
HTTP request method, such as GET, POST, DELETE, or HEAD. Default value: GET.
String
No
Query
Request parameters to be included in the signature in the format of {key: 'val'}
Object
No
Headers
Request headers to be included in the signature in the format of {key: 'val'}
Object
No
Expires
Signature expiration time in seconds. Default value: 900.
Number
No
Return value description
The return value is a string. There are two possible scenarios:
1. If the signature can be calculated synchronously (for example, the SecretId and SecretKey have been passed in during instantiation), the signed URL will be returned by default.
2. Otherwise, an unsigned URL will be returned.
Callback function description
function(err, data) { ... }
Parameter
Description
Type
err
Object returned when an error (network error or service error) occurs. If the request is successful, this parameter is empty. For more information, see Error Codes.
Object
data
The object returned when the request is successful. If an error occurs with the request, this parameter is empty.
Object
- Url
Calculated URL
String
﻿

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Generating Pre-Signed URL

Overview

Signature Calculation

Sample code

Field description

Return value description

Getting a Pre-signed Request URL

Download request samples

Upload request samples

Field description

Return value description

Callback function description

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Parameter	Description	Type	Required
SecretId	Your `SecretId`.	String	Yes
SecretKey	Your `SecretKey`.	String	Yes
Method	HTTP request method, such as `GET`, `POST`, `DELETE`, or `HEAD`.	String	Yes
Key	Object key (object name) is the unique ID of an object in a bucket. If the request operation is to be performed on a file, this parameter is required and should be a filename. If the operation is on a bucket, this parameter should be left empty.	String	No
Query	Request parameters to be included in the signature in the format of `{key: 'val'}`	Object	No
Headers	Request headers to be included in the signature in the format of `{key: 'val'}`	Object	No
Expires	Signature expiration time in seconds. Default value: `900`.	Number	No

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Recent Pages

Generating Pre-Signed URL

Overview

Signature Calculation

Sample code

Field description

Return value description

Getting a Pre-signed Request URL

Download request samples

Upload request samples

Field description

Return value description

Callback function description

Was this page helpful?

Was this page helpful?