Pre-signed URL

Last updated: 2020-03-24 11:01:29

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Overview

The SDK for Node.js provides APIs for getting object URLs and pre-signed request URLs. For details, see the descriptions and samples below.

Signature Calculation

In all COS XML API requests, the authentication credential "Authorization" is required for all the 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 request validity.

It is recommended to only use this method for frontend debugging and not in real projects as it involves key disclosure risks.

Use Cases

Obtain the authentication credential for file download:

var Authorization = COS.getAuthorization({
    SecretId: 'COS_SECRETID',
    SecretKey: 'COS_SECRETKEY',
    Method: 'get',
    Key: 'a.jpg',
    Expires: 60,
    Query: {},
    Headers: {}
});

Parameter Descriptions

Parameter Name Description Type Required
SecretId User's SecretId String Yes
SecretKey User's SecretKey String Yes
Method HTTP operation method such as GET, POST, DELETE, and HEAD String Yes
Key Object key (object name), a 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 Query parameter object of the request Object No
Headers Header parameter object of the request Object No
Expires Validity period of the signature; unit: second. Default value: 900 Number No

Returned Value Description

The returned value is the calculated authentication credential string "authorization".

Getting a Pre-signed Request URL

Samples for Download Requests

Sample 1. Get an object URL without signature

var url = cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: '1.jpg',
    Sign: false
});

Sample 2. Get a signed object URL

var url = cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: '1.jpg'
});

Sample 3. If the signing process is asynchronous, you need to get the signed URL through callback

cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: '1.jpg',
    Sign: false
}, function (err, data) {
    console.log(err || data.Url);
});

Sample 4. Specify the validity period of the link

cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: '1.jpg',
    Sign: true,
    Expires: 3600, // Unit: second
}, function (err, data) {
    console.log(err || data.Url);
});

Sample 5. Get the file URL and download the file

var request = require('request');
var fs = require('fs');
cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: '1.jpg',
    Sign: true
}, function (err, data) {
    if (err) return console.log(err);
    console.log(data.Url);
    var req = request(data.Url, function (err, response, body) {
        console.log(err || body);
    });
    var writeStream = fs.createWriteStream(__dirname + '/1.jpg');
    req.pipe(writeStream);
});

Samples for Upload Requests

Sample 1. Get a pre-signed URL for Put Object upload

var request = require('request');
var fs = require('fs');
cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Method: 'PUT',
    Key: '1.jpg',
    Sign: true
}, function (err, data) {
    if (err) return console.log(err);
    console.log(data.Url);
    var readStream = fs.createReadStream(__dirname + '/1.jpg');
    var req = request({
        method: 'PUT',
        url: data.Url,
    }, function (err, response, body) {
        console.log(err || body);
    });
    readStream.pipe(req);
});

Parameter Descriptions

Parameter Name 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 Domain Names String Yes
Key Object key (object name), a 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 Boolean No
Method HTTP operation method such as GET, POST, DELETE, and HEAD. Default value: GET String No
Query Query parameter object used in the signature calculation Object No
Headers Header parameter object used in the signature calculation Object No
Expires Validity period of the signature; unit: second. Default value: 900 Number No

Returned Value Description

The returned 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; a URL without a signature will be returned.

Callback Function Description

function(err, data) { ... }
Parameter Name Description Type
err Object returned when an error, a network error or service error, occurs. If the request is successful, this parameter will be empty. For more information, see Error Codes Object
data Object returned when the request succeeds. If the request fails, this will be empty Object
- Url Calculated URL String