http-wokou/pkg/pagemod.go

/*
		GNU GENERAL PUBLIC LICENSE
                 Version 3, 29 June 2007

 Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

 http-wokou, An HTTP Proxying framework for bypassing DNS Security
 Copyright (C) 2024 Russell Hrubesky, ChiralWorks Software LLC

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <https://www.gnu.org/licenses/>.

*/

package httpserver

import (
	"bytes"
	"encoding/json"
	"io"
	"log"
	"os"
)

type PageMod struct {
	Target string `json:"target"`
	Search string `json:"search"`
	Sub    string `json:"sub"`
}

type AllPageMods struct {
	Content []*PageMod          `json:"modifications"`
	Bypass  map[string]struct{} `json:"bypass"`
}

/*
Load page modifications from the config/pagemod directory

	:param loc: the path to the pagemods directory
*/
func LoadPageMods(loc string) *AllPageMods {
	b, err := os.ReadFile(loc)
	if err != nil {
		log.Fatal("Couldnt load the page modification config from: ", loc, ". Error: ", err)
	}
	var pgMod AllPageMods
	err = json.Unmarshal(b, &pgMod)
	if err != nil {
		log.Fatal("There was an error loading the configuration: ", err)
	}
	return &pgMod

}

/*
Rewrite all occurences of these values into the response body
*/
func (c *Controller) pageMod(data []byte) []byte {
	for idx := range c.PageMods.Content {
		if c.PageMods.Content[idx].Target == "content" {
			data = bytes.ReplaceAll(data, []byte(c.PageMods.Content[idx].Search), []byte(c.PageMods.Content[idx].Sub))
		}
	}
	return data
}

/*
perform any request body rewrites as per described in the pagemod config

	:param data: a byte array to modify
*/
func (c *Controller) requestBodyRewrites(data io.Reader) io.Reader {
	b, err := io.ReadAll(data)
	if err != nil {
		log.Fatal("couldnt read POST body data: ", err)
	}
	for idx := range c.PageMods.Content {
		if c.PageMods.Content[idx].Target == "body" {
			b = bytes.ReplaceAll(b, []byte(c.PageMods.Content[idx].Search), []byte(c.PageMods.Content[idx].Sub))
		}
	}
	return bytes.NewReader(b)
}