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Configure secure token

Do the first three steps in Gcore Customer Portal on the Secure token tab.
Configure Secure Token
1. Enable the Secure token option in the resource settings. 2. Enter a key that contains between 6 and 32 characters. 3. If you want your content to be accessible from any IP address, leave the Add a client’s IP to the token unchecked. If you want to make your content available only from one IP, check the checkbox (you will specify the allowlisted IP address later at Step 4). 4. Do this step on your origin server. Insert a script on your website which generates secure links. The generated links should look like as below:
generated links
Where:
  • http://cdn.example.com/photo.jpeg is the path to the file,
  • DMF1ucDxtHCxwYQ is the output of the “MD5(String)” hash function, where String is the parameter obtained by merging elements: <link expiry time><file path><allowlisted IP address><key from Step 2>,
  • 2147483647 is the time in the UNIX timestamp format until which the link is considered valid.
We have prepared script templates for PHP, Python, and OpenSSL — just copy one of them from the Scripts for link generation section below. The script will start creating secure links to the content. 5. Do this step on your origin server. Arrange the content on your website to allow access to the protected files only over a secured link — that is, rule out the delivery of the required content over a link without a secure token. Moreover, make sure our CDN can access the content on your origin server regardless of whether a key is present or not.
WarningAfter enabling the secure token option, the cache hit ratio may decrease; to improve it, we recommend enabling the Ignore Query String option, which treats objects with different query parameters as a single cacheable object instead of multiple separate ones.

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How secure token URL matching works

Secure Token validates three things from the request URL:
  • md5: the token hash.
  • expires: the Unix timestamp until which the URL is valid.
  • Path: the file path or directory path that was used when the token was generated.
The path is important. The CDN validates the token against the path used in the hash string. If the token was generated for an exact file, it works only for that file. If the token was generated for a directory and Query String Forwarding is enabled, it can work for files inside that directory and pass the same query parameters to related HLS or MPEG-DASH files.

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Token for exact file

Use an exact file token for standalone files such as images, archives, MP4 files or one protected video manifest when you do not need to authorize nested requests with the same token. Example protected file: 
/images/poster.jpeg
Generate the token with this path: 
/images/poster.jpeg
The user requests: 
https://cdn.example.com/images/poster.jpeg?md5=TOKEN&expires=1777545540
This token is valid only for /images/poster.jpeg. This token does not provide access to adjacent files, for example: 
https://cdn.example.com/images/poster.webp 403 Forbidden
https://cdn.example.com/images/poster.png 403 Forbidden
https://cdn.example.com/images/master.m3u8 403 Forbidden

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Token with Query String Forwarding

Use a token with Query String Forwarding enabled for HLS and MPEG-DASH when the player must request a master manifest, nested rendition manifests, media segments, and subtitles under the same path. In this mode, do not include a filename in token generation. Generate the token for the full directory path only. For example, for files in: 
/videos/video-1/
use this path in the token generation script: For PHP: 
$path = '/videos/video-1/';
For Python: 
path = /videos/video-1/"
This token works only for files directly inside /videos/video-1/. It does not work for files in subdirectories such as /videos/video-1/360p/. If your HLS or MPEG-DASH files are split across subdirectories, generate and use tokens for those directories separately or place the related manifests and segments under one directory. Example HLS files: 
/videos/video-1/master.m3u8
/videos/video-1/rendition-1080.m3u8
/videos/video-1/segment-001.ts
/videos/video-1/segment-002.ts
Generate the token with the directory path: 
/videos/video-1/
The user requests only the master manifest with the token: 
https://cdn.example.com/videos/video-1/master.m3u8?md5=TOKEN&expires=1893456000
With Query String Forwarding enabled, the CDN automatically inserts the same query parameters into related manifest body links. The video player then requests nested files with the forwarded token: 
https://cdn.example.com/videos/video-1/rendition-1080.m3u8?md5=TOKEN&expires=1893456000
https://cdn.example.com/videos/video-1/segment-001.ts?md5=TOKEN&expires=1893456000
https://cdn.example.com/videos/video-1/segment-002.ts?md5=TOKEN&expires=1893456000
For HLS and MPEG-DASH, configure a CDN-resource to use Query String Forwarding with: 
{
  "forward_from_file_types": [
    "m3u8",
    "mpd"
  ],
  "forward_to_file_types": [
    "ts",
    "mp4",
    "m3u8",
    "m4s",
    "vtt"
  ],
  "forward_only_keys": [
    "md5",
    "expires"
  ]
}
To check how Query String Forwarding works in real life, open this demo HLS manifest: It will open the master file with nested files (note that &other=parameter is not forwarded): 
http://demo-files-protected.gvideo.io/coffee_run/master.m3u8?md5=eBx15p01_a9JNuo1iZpTfQ&expires=1893456000&other=parameter
http://demo-files-protected.gvideo.io/coffee_run/index-svod720n-v1-a1.m3u8?expires=1893456000&md5=eBx15p01_a9JNuo1iZpTfQ
http://demo-files-protected.gvideo.io/coffee_run/segment-1-svod720n-v1-a1.ts?expires=1893456000&md5=eBx15p01_a9JNuo1iZpTfQ
http://demo-files-protected.gvideo.io/coffee_run/segment-2-svod720n-v1-a1.ts?expires=1893456000&md5=eBx15p01_a9JNuo1iZpTfQ

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Token in a path

Tokens embedded into the URL path are not supported for now by CDN natively. This option is available for Gcore Video Streaming: 
https://cdn.example.com/secure/TOKEN/1777545540/coffee_run/master.m3u8
https://cdn.example.com/secure/TOKEN/1777545540/coffee_run/rendition-1080.m3u8
https://cdn.example.com/secure/TOKEN/1777545540/coffee_run/segment-001.ts
Example of token in path for Gcore Video Streaming: 
https://demo-protected.gvideo.io/videos/2675_pG8TfmKx2LU2qs/rI1224fiE3USCa8qYnMuGQ/1861919999/master.m3u8
Where:
  • https://demo-protected.gvideo.io is the CDN URL,
  • /videos/2675_pG8TfmKx2LU2qs/ is the video ID,
  • rI1224fiE3USCa8qYnMuGQ is the token,
  • 1861919999 is the expiration time in the UNIX timestamp format until which the link is considered valid.
Below is the script for creating temporary links with the IP-based access restriction. The files will be accessible only from an allowlisted IP address and only until the link expires. 
<?php
$secret = 'secret_key';
$ip = '1.2.3.4';
$path = '/live/133529_2/chunklist.m3u8';
$expires = time() + 10000;
$link = "$expires$path$ip $secret";
$md5 = md5($link, true);
$md5 = base64_encode($md5);
$md5 = strtr($md5, '+/', '-_');
$md5 = str_replace('=', '', $md5);
$url = "http://cdn.site.com{$path}?md5={$md5}&expires={$expires}";
 echo $url;
 echo "\n";
Below is the script for creating temporary links without any IP-based access restriction. The files will be accessible from any IP address, but only until the link expires. 
<?php
$secret = 'secret_key';
$path = '/live/133529_2/chunklist.m3u8';
$expires = time() + 10000;
$link = "$expires$path $secret";
$md5 = md5($link, true);
$md5 = base64_encode($md5);
$md5 = strtr($md5, '+/', '-_');
$md5 = str_replace('=', '', $md5);
$url = "http://cdn.site.com{$path}?md5={$md5}&expires={$expires}";
 echo $url;
 echo "\n"
In these scripts:
  • $secret is the secret key,
  • $path is the path to the file,
  • $ip is the IP address that is allowed to access the content,
  • $expires is the link expiry time (in seconds),
  • $url is the address of the file.
The script for creating temporary links with the IP-based access restriction. The files will be accessible only from an allowlisted IP address and only until the link expires. 
import base64
from hashlib import md5
from time import time
secret = 'secret_key'
path = "/images/1.jpg"
ip = '1.2.3.4'
# TTL of URL (in sec)
ttl = 100000
expires = int(time()) + ttl#Token generation
token_hash = md5(f"{expires}{path}{ip} {secret}".encode()).digest()
token = base64.b64encode(token_hash).decode().replace("\n", "").replace("+", "-").replace("/", "_").replace("=", "")
secured_url = f"http://cdn.site.com{path}?md5={token}&expires={expires}"# File's URL
print(secured_url)
Below is the script for creating temporary links without any IP-based access restriction. The files will be accessible from any IP address, but only until the link expires. 
import base64
from hashlib import md5
from time import time
secret = 'secret_key'
path = "/images/1.jpg"
# TTL of URL (in sec)
ttl = 100000
expires = int(time()) + ttl#Token generation
token_hash = md5(f"{expires}{path} {secret}".encode()).digest()
token = base64.b64encode(token_hash).decode().replace("\n", "").replace("+", "-").replace("/", "_").replace("=", "")
secured_url = f"http://cdn.site.com{path}?md5={token}&expires={expires}"# File's URL
print(secured_url)
In these scripts:
  • secret is the secret key,
  • path is the path to the file,
  • ip is the IP address that is allowed to access the content,
  • expires is the link expiry time (in seconds),
  • secured_url is the link to the file.

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Generate a secure token in OpenSSL

The script for creating a secure token that limits the link lifespan and allows access only to an allowlisted IP: 
echo -n '2147483647/images/1.jpg1.2.3.4 secret_key' | openssl md5 -binary | openssl base64 | tr +/ -_ | tr -d =
'2147483647/images/1.jpg1.2.3.4 secret_key' = '{expires}{path}{ip} {secret_key}'
The script for creating a secure token that only limits the link lifespan: 
echo -n '2147483647/images/1.jpg secret_key' | openssl md5 -binary | openssl base64 | tr +/ -_ | tr -d =
'2147483647/images/1.jpg secret_key' = '{expires}{path} {secret_key}'
In these scripts:
  • 2147483647/images/1.jpg is the path to the file,
  • 1.2.3.4 is the IP address that is allowed to access the content,
  • secret_key is a secret key you specified at Step 2 of the Configure Secure Token instruction.
The scripts above can only generate a secure token. You need to create a separate script that will add a secure token and expiry time to links. The script is supposed to create a link as shown below:
created a link
Where:
  • http://cdn.example.com/photo.jpeg is the path to the file,
  • DMF1ucDxtHCxwYQ is a secure token,
  • 2147483647 is the time in the UNIX timestamp format until which the link is considered valid.

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IP binding and mobile networks

When you bind a secure token to the client’s IP address, the CDN recomputes the hash using the IP address it sees on the incoming request. This becomes a problem on some mobile networks. In certain countries, mobile ISPs change a subscriber’s public IP address very aggressively — sometimes within minutes — because they route many subscribers through carrier-grade NAT (CGNAT) and rotate addresses across a pool. A token signed for one IP fails as soon as the carrier moves the user to another. The effect is most visible with Query String Forwarding for video. The player requests the manifest, gets a token, and the token is forwarded to the related sub-segments. If the mobile ISP switches the client IP between requests, the next segment is downloaded from a different IP and returns 403, while earlier segments returned 200. So a single user can receive 200 and 403 responses almost simultaneously, and this is a strong indicator that the cause is mobile IP rotation rather than an expired or malformed token. If you observe this pattern — 200 and 403 mixed together for the same user on a mobile network — we can change the default token behavior from binding to a dedicated IP to binding to a wider subnet mask, such as /24 or even /16 for very aggressive mobile operators. A wider mask still ties the URL to the user’s ISP block (so external sharing and hotlinking remain blocked) while tolerating IP rotation within that block. This option is available for Enterprise customers. To enable it, contact our support team or your account manager.