Decode Rule

Explanation

Commit 4ee6eb7 (1.3.5) introduced the decode option to rules. This is used to bypass base64 encoded click-jacking links such as:

https://www.emjcd.com/links-i/?d=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%3D%3D

The decoded result for the d parameter results in the following json object:

{
  "surfer": "00000:VPSlYT7rAxzl",
  "lastClickName": "LCLK",
  "lastClickValue": "cjo!xi59-00000",
  "destinationUrl": "https://www.vudu.com/content/movies/details/Moonlight-Season-1/133120",
  "sid": "[subid_value]",
  "type": "dlg",
  "pid": 9011673,
  "eventId": "0acda5d0f73e11ec02ac749b0a1c0e0e",
  "cjSession": "2f0c0ccb-e0ef-04c2-b23c-673cf0616e16",
  "loyaltyExpiration": 0,
  "redirectedToLiveramp": false,
  "cjConsentEnum": "NEVER_ASKED"
}

Using this information we can create the decode rule:

{ "param": "d", "lookFor": "destinationUrl" }

When applied, tidy-url will attempt to decode, parse and extract the destinationUrl using the d parameter. If any part of this process fails the rule will be skipped and an error will be logged to the console (assuming silent is false).

Note

If the string was successfully decoded and parsed it will be stored in the response data.info.decoded, even if the destinationUrl key was not located. This is helpful for debugging.

Changes

This method is currently very simple and will likely change to support more URLs in the future, as many simply encode the url instead of an object.

Example

The following is a working rule for the link at the top of this page.

const rule = {
  name: 'emjcd.com',
  match: /^www.emjcd.com/i,
  decode: { param: 'd', lookFor: 'destinationUrl' }
}