Signing Method B

How It Works

Example signed URLs look like:

http://DomainName/timestamp/sha256/FileName

Verification Method

After receiving a request, a CDN server verifies the request as follows:

1. Checks whether the authentication parameter is included in the request. If not, the request is considered invalid and an HTTP 403 error code is returned.
2. Checks whether the value of timestamp plus the validity period specified in the signed URL is later than the current time.
   • If not, the signed URL is considered invalid and the HTTP 403 error is returned.
   • If yes, the time verification passes and CDN goes to step 3.
3. Constructs sstring, calculates HashValue using this string and the MD5 or SHA256 algorithm, and compares HashValue with the md5hash or sha256 value in the request. If the md5hash or sha256 value is the same as HashValue, the authentication is successful and the requested file is returned. Or, the authentication fails and an HTTP 403 error code is returned. HashValue is calculated as follows:

   sstring = "PrivateKeytimestampFilename"
   HashValue = sha256sum(sstring)

   Or

   sstring = "PrivateKeytimestampFilename"
   HashValue = md5sum(sstring)

Procedure

1. Log in to Huawei Cloud console. Choose Service List > Content Delivery & Edge Computing > Content Delivery Network.

   The CDN console is displayed.

2. In the navigation pane, choose Domains.
3. In the domain list, click the target domain name or click Configure in the Operation column.
4. Click the Access Control tab and click Configure under Token Authentication.
   Figure 1 Configuring token authentication
   
5. Turn on the Status switch.
6. Set the parameters according to the following table and click OK.

   Table 2 Parameter description

   Parameter	Description
   Signing Method	Select Method B.
   Authentication Scope	Files to be authenticated. Select All files, Specific files, or Specific files excluded.
   Inheritance	Add the authentication parameter to TS and MP4 files under M3U8/MPD index files, so that the files can be played after authentication succeeds. NOTE: If there are multi-layer M3U8/MPD files, only the first-layer M3U8/MPD files are parsed, and the TS/MP4 streams of M3U8/MPD files in other layers are not expanded. The standard M3U8 format is supported. M3U8 files are parsed by line. If the parsing fails, responses from the origin server are returned to users. URIs starting with the #EXT-X-MAP tag and URLs/URIs not starting with the pound key (#) are supported. The standard MPD format is supported. MPD files are parsed by line. If the parsing fails, responses from the origin server are returned to users. The URI between tags <BaseURL> and </BaseURL> is identified. The SegmentTemplate tag is not supported. If your M3U8/MPD index files contain special characters, CDN does not automatically transcode the characters during authentication calculation. If clients have the logic for automatically transcoding special characters, the access may fail due to the authentication failure. If the origin server returns resources compressed using gzip or Brotli to CDN PoPs, the authentication inheritance settings become invalid.
   Start Time	Same as user request: time when a user accesses the M3U8/MPD file. Current time: current time of the authentication server.
   File Name Extensions	Set this parameter when you select Specific files or Specific files excluded for Authentication Scope. Only requests for files with the specified file name extensions are authenticated or not authenticated. Only lowercase letters and digits are supported. Use semicolons (;) to separate multiple file name extensions.
   Signing Key	Authentication password. The value contains 6 to 32 characters, including letters and digits. NOTE: For security purposes, you are advised to use 8 to 32 characters.
   Secondary Key	(Optional) Secondary password for authentication. If you want the old and new keys to take effect, you can set the old key as the secondary key. Users can access content only after CDN verifies the primary or secondary key. A key contains 6 to 32 characters, including letters and digits. NOTE: For security purposes, you are advised to use 8 to 32 characters.
   Encryption Algorithm	MD5 or SHA256.
   Validity Period	How long the signed URL remains effective. The value ranges from 0s to 31,536,000s.

   Authentication Calculator

   Using the authentication calculator, you can generate a signed URL for users. Set parameters according to Table 2 and Table 3, and click Generate to generate a signed URL that will expire at a specific time.

   Table 3 Parameter description

   Parameter	Description
   Signing Key	Authentication password. Enter 6 to 32 characters, including letters and digits. The value must be the same as the signing key specified in the token authentication configuration.
   Access Path	Path of the content, which starts with a slash (/) and does not carry a query string.
   Encryption Algorithm	MD5 or SHA256.
   Start Time	Time when the signed URL will take effect.
   Validity Period	How long the signed URL remains effective. The value ranges from 0s to 31,536,000s. If this value is greater than the validity period set in the token authentication settings, the latter will be used. Example: If you set this parameter to 2,000s, but the validity period set in the token authentication settings is 1,800s, the validity period of signed URLs will be 1,800s.

   

   Escape special characters in the signed URL if any.

Disabling Token Authentication

Switch off Status to disable token authentication and clear all token authentication settings. You need to set related parameters when enabling this function again.

Example

The following uses the MD5 algorithm as an example:

1. The back-to-origin URL is as follows:

   http://hwcdn.example.com/T128_2_1_0_sdk/0210/M00/82/3E/test.mp3

2. The signing key is huaweicloud12345 (customizable).
3. timestamp is 201706301000.
4. The CDN server constructs a string for calculating md5hash.

   huaweicloud12345201706301000/T128_2_1_0_sdk/0210/M00/82/3E/test.mp3

5. The CDN server calculates md5hash according to the string.

   md5hash = md5sum("huaweicloud12345201706301000/T128_2_1_0_sdk/0210/M00/82/3E/test.mp3") =668f28d134ec6446a8ae83a43d0a554b 

6. The request URL is:

   http://hwcdn.example.com/201706301000/668f28d134ec6446a8ae83a43d0a554b/T128_2_1_0_sdk/0210/M00/82/3E/test.mp3

If a request is within the validity period (earlier than or equal to 10:30:00 on June 30, 2017) and the md5hash value in the request is the same as the calculated md5hash value (668f28d134ec6446a8ae83a43d0a554b), the authentication is successful.