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Generating Pre-Signed URLs

Last updated: 2022-01-10 14:27:53

    Overview

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

    Note:

    • You are advised to use a temporary key to generate a pre-signed URL 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.
    • 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:

    It is recommended that this method is only used for frontend debugging but not in actual projects, as it may disclose keys.

    Sample code

    Obtaining the authentication credential for file download:

    // Log in to the [CAM console](https://console.tencentcloud.com/cam/capi) to check and manage the `SecretId` and `SecretKey` of your project.
    var COS = require('cos-nodejs-sdk-v5');
    var Authorization = COS.getAuthorization({
       SecretId: 'SECRETID',
       SecretKey: 'SECRETKEY',
       Method: 'get',
       Key: 'a.jpg',
       Expires: 60,
       Query: {},
       Headers: {}
    });
    

    Parameter description

    Parameter Description Type Required
    SecretId User SecretId String Yes
    SecretKey User's 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 include in the signature. Format: {key: 'val'} Object No
    Headers Request headers to include in the signature. Format: {key: 'val'} Object No
    Expires Signature expiration time in seconds. Default value: 900 Number No

    Return value description

    The returned value is the calculated authentication credential string authorization.

    Getting a Pre-signed Request URL

    Download request samples

    Sample 1. Get an unsigned object URL

    var url = cos.getObjectUrl({
       Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
       Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
       Key: '1.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: '1.jpg',  /* Object key stored in the bucket (such as `1.jpg` and `a/b/test.txt`). Required. */
    });
    

    Sample 3. 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: '1.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: '1.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 file URL and download the file

    var request = require('request');
    var fs = require('fs');
    cos.getObjectUrl({
       Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
       Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
       Key: '1.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);
       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);
    });
    

    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: '1.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

    var request = require('request');
    var fs = require('fs');
    cos.getObjectUrl({
       Bucket: 'examplebucket-1250000000', /* Your bucket name. Required. */
       Region: 'COS_REGION',  /* Bucket region, such as `ap-beijing`. Required. */
       Key: '1.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);
       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 description

    Parameter Description Type Required
    Bucket Bucket name in the format of BucketName-APPID. String Yes
    Region Bucket region. For the enumerated values, please 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 It can be http: (default) or https: String No
    Domain Bucket access domain. 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 include in the signature. Format: {key: 'val'} Object No
    Headers Request headers to include in the signature. Format: {key: 'val'} Object No
    Expires Signature expiration time in seconds. Default value: 900 Number No

    Returned value description

    A string is returned in one of the two ways:

    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 Error code, which is returned when an error (network error or service error) occurs. If the request is successful, this parameter is empty. For more information, please see Error Codes. Object
    data Content returned when the request is successful. If the request fails, this parameter is empty. Object
    - Url Calculated URL String
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