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, private resource operations require the authentication credential "authorization" which is used to determine whether the current request is legal.

There are two ways to use the authorization:

1. Put it in the header parameter (field name: authorization).
2. Put i in the URL parameter (field name: sign).

The COS.getAuthorization method is used to calculate the authorization, i.e., signing information used to verify the request validity.

This method is recommended only for frontend debugging. It is not recommended to use it in real projects as there may be a risk of key disclosure.

Use Cases

Obtain the authorization for object download:

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

Parameter Descriptions

Return Value Description

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

Getting a Pre-signed Request URL

Upload Request Description

Uploading files in a WeChat Mini Program can only be done via the POST Object API. Getting a pre-signed URL is not applicable to this API. If you need to upload files by yourself, do as described in WeChat Mini Program Upload Practices.

Sample Request for Download

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 the signed URL through callback

If the signing process is async, 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 validity period of the link

cos.getObjectUrl({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: 'picture.jpg',
    Sign: true,
    Expires: 3600, // In seconds
}, 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, // A domain name with a URL needs to be used as the download whitelist
        success (res) {
            console.log(res.statusCode, res.tempFilePath);
        },
        fail: function (err) {
            console.log(err);
        },
    });
});

Parameter Descriptions

Return Value Description

The return value is a string in the following two cases:

1. If the signature can be calculated synchronously (for example, passing in the SecretId and SecretKey through instantiation), the signed URL will be returned by default.
2. Otherwise; a URL with no signature will be returned.

Callback Function Description

function(err, data) { ... }