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

javen-yan/header-transform-upgrade