Header transformation plugin for Traefik

This plugin allows to change, on the fly, the header's value of a request.

Dev traefik.yml configuration file for traefik

pilot:
  token: [REDACTED]

experimental:
  devPlugin:
    goPath: /home/tm/go
    moduleName: github.com/adyanth/header-transform

entryPoints:
  http:
    address: ":8000"
    forwardedHeaders:
      insecure: true

api:
  dashboard: true
  insecure: true

providers:
  file:
    filename: rules-header-transform.yaml

How to dev

$ docker run -d --network host containous/whoami -port 5000
# traefik --config-file traefik.yml

How to use

To choose a Rule you have to fill the Type field with one of the following:

• 'Rename' : to rename a header
• 'Set' : to Set a header
• 'Del' : to Delete a header

Each Rule can be named with the Name field Each Rule can be set to run only if the previous hop IP address belongs to a trusted range of IPs. Set this using the optional TrustedCIDR.

# Example
- Rule:
      Name: 'Test'
      ...
      TrustedCIDR:
        - 10.0.0.0/8
        - 172.16.0.0/12
        - 192.168.0.0/16

Rename

A Rule Rename needs two arguments and optionally the third.

• Header, the regex of the header you want to replace
• Value, the new header
• HeaderPrefix, the prefix to denote the new Header name is to be taken from another header value

# Example Rename
- Rule:
      Name: 'Header rename'
      Header: 'Cache-Control'
      Value: 'NewHeader'
      Type: 'Rename'

# Old header:
Cache-Control: gzip, deflate

# New header:
NewHeader: gzip, deflate

- Rule:
      Name: 'Header Renaming'
      Header: 'X-Traefik-*'
      Value: 'X-Traefik-merged'
      Type: 'Rename'

# Old header:
X-Traefik-uuid: 0
X-Traefik-date: mer. 21 oct. 2020 11:57:39 CEST
# New header:
X-Traefik-merged: 0 # A value from old headers

Set

A Set rule will either create or replace the header and value (if it already exists), appending multiple values with the separator if specified.

A Rule Set needs the first two arguments, and optionally the next three. Value can be skipped if specifying Values.

• Header, the header you want to create
• Value, the value of the new header
• Values, a list of values to add
• Sep, the separator you want to use
• HeaderPrefix, the prefix to denote the Value is to be taken from another header

# Example Set
- Rule:
      Name: 'Set Cache-Control'
      Header: 'Cache-Control'
      Value: 'Foo'
      Type: 'Set'

# New header:
Cache-Control: Foo

# Example Usage
- Rule:
  Name: 'Header set'
  Header: 'X-Forwarded-For'
  Value: '^CF-Connecting-IP'
  HeaderPrefix: "^"
  Type: 'Set'

# Old header:
CF-Connecting-IP: 1.1.1.1

# New headers:
CF-Connecting-IP: 1.1.1.1
X-Forwarded-For: 1.1.1.1

# Example Usage
- Rule:
  Name: 'Header XFF'
  Header: 'X-Forwarded-For'
  Value: '^CF-Connecting-IP'
  Values:
    - '^X-Forwarded-For'
    - '192.168.0.1'
  Sep: ', '
  HeaderPrefix: "^"
  Type: 'Set'

# Old header:
CF-Connecting-IP: 1.1.1.1
X-Forwarded-For: 10.0.0.1, 10.10.10.1
# New headers:
CF-Connecting-IP: 1.1.1.1
X-Forwarded-For: 1.1.1.1, 10.0.0.1, 10.10.10.1, 192.168.0.1

# Example Join
- Rule:
      Name: 'Header join'
      Header: 'Cache-Control'
      Sep: ','
      HeaderPrefix: "^"
      Values:
        - '^Cache-Control'
        - 'Foo'
        - 'Bar'
      Type: 'Set'

# Old header:
Cache-Control: gzip, deflate

# Joined header:
Cache-Control: gzip, deflate,Foo,Bar

Delete

A Rule Delete needs only one argument

• Header, the header you want to delete

# Example Del
- Rule:
      Name: 'Delete Cache-Control'
      Header: 'Cache-Control'
      Type: 'Del'

Point to note

The rules will be evaluated in the order of definition

#Example
- Rule:
  Name: 'Header addition'
  Header: 'X-Custom-2'
  Value: 'True'
  Type: 'Set'
- Rule:
  Name: 'Header deletion'
  Header: 'X-Custom-2'
  Type: 'Del'
- Rule:
  Name: 'Header join'
  Header: 'X-Custom-2'
  Value: 'False'
  Type: 'Set'

This will firstly set the header X-Custom-2 to 'True', then delete it and finally set it again but with False