Pre-signed URL

Overview

The SDK for WeChat Mini Program provides samples for calculating signatures and getting object URLs and pre-signed request URLs.

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 object download:

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

Parameter Descriptions

Returned Value Description

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

Getting a Pre-signed Request URL

Upload Request Description

In a WeChat Mini Program, you can only upload files via the POST Object API. Getting a pre-signed URL is not applicable to this API. If you need to upload files by yourself, please refer to Uploading Directly Through a WeChat Mini Program.

Samples for Download Requests

Sample 1. Get an object URL without signature

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

Sample 2. Get a signed object URL

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

Sample 3. Get a signed URL through callback

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

cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: 'picture.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: 'picture.jpg',
    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',
    Region: 'ap-beijing',
    Key: 'picture.jpg',
    Sign: true
}, function (err, data) {
    if (!err) return console.log(err);
    wx.downloadFile({
        url: data.Url, // The “url” domain name needs to be added to the download whitelist
        success (res) {
            console.log(res.statusCode, res.tempFilePath);
        },
        fail: function (err) {
            console.log(err);
        },
    });
});

Parameter Descriptions

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) { ... }