Nvram-cfg-parser NPM

nvram-cfg-parser

Command line parser for Tomato Firmware NVRAM cfg backups

What it does

Decodes Tomato cfg files into JSON so they can be changed and compared against other backups. Encodes JSON-formatted Tomato cfg key/value pairs into the Tomato cfg format.

Installation

nvram-cfg-parser is available from npm, the standard package manager included with nodejs.

Install from npm:

# npm install -g nvram-cfg-parser

Usage:

decode

nvramcfg decode <filename>

Command example:

$ nvramcfg decode tomato_v128_m943394.cfg

Output example (keys in no particular order):

{
  "0|31|||word text\n^begins-with.domain.\n.ends-with.net$\n^www.exact-domain.net$|0|exampl": "|1320|300|31|||word text\n^begins-with.domain.\n.ends-with.net$\n^www.exact-domain.net$|0|example",
  "wl_mac_deny": "",
  "wl_radius_port": "1812",
  "sb/1/ofdm2gpo": "0x44444444",
  "pptp_client_mru": "1450",
  "https_crt": "",
  "qos_reset": "1",
  ...

decode to file

$ nvramcfg decode tomato_v128_m943394.cfg > tomato_v128_m943394.json

encode

nvramcfg encode <format> <filename>

Command example:

$ nvramcfg encode arm tomato_v128_m943394-altered.json > tomato_v128_m943394-altered.cfg

Supported formats are original and arm.

colorized json diff

nvramcfg diff <filename1> <filename2>

Command example:

$ nvramcfg diff tomato_v128_m943394.json tomato_v128_m943394-altered.json

Output example

 {
-  router_name: "TomatoUSB"
+  router_name: "ExampleName"
 }

How it works

Original

The tomato_vxxx_xxxxx.cfg files are gzipped utf-8 text with null characters bounding and separating the key=value pair sets. We unzip the file, strip the header and footer, and read the null-separated key=value pairs.

ARM

The tomato_vxxx_xxxxx.cfg files are not gzipped, but are an obfuscated version of the original utf-8-with-null-separators. We read the random value and de-obfuscate back to the original format.

Programmatic usage in JavaScript

Decode and encode are available from the NvramParser class. See comments in src/nvram-parser.iced, src/nvram-arm-parser.iced, for details.

FAQ

How to tell if my router build is ARM format?
The tomato builds for your router contain ARM in the filename. Example: tomato-RT-AC56U-AT-ARM-2.7-128-AIO-64K.trx