php-json-signer

JSON Signer

This application can be used to sign JSON files, by adding some fields that can be used to determine their time of signing and the sequence number. The signature is "detached" so no complicated file syntax is needed to store the signature in the file itself.

Install

    $ git clone https://git.tuxed.net/fkooman/php-json-signer
    $ cd php-json-signer
    $ composer install

Configure

The public and secret key are stored in the XDG home data folder, typically this will be ${HOME}/.local/share/php-json-signer. They are automatically generated on first use of the application.

Sign

Sign a JSON file:

    $ echo '{"foo": "bar"}' > foo.json
    $ php bin/app.php --sign foo.json

This adds some additional fields:

    $ cat foo.json
    {
        "foo": "bar",
        "seq": 1,
        "signed_at": "2017-08-14 21:17:39"
    }

The field seq will be incremented by one, or added and set to 1 when it does not yet exist.

The signed_at field will be set to the current date/time (UTC).

A "detached" signature is generated with the extension .sig. From the example above there will be a (modified) foo.json with the seq and signed_at fields, and a signature file foo.json.sig.

Verify

Verify a JSON signature:

    $ php bin/app.php --verify foo.json

It is assumed that the signature file is placed in the same directory, i.e. foo.json.sig should be placed in the same directory as foo.json.

Show

To view the public key that is used to sign the JSON files:

    $ php bin/app.php --show

Multi Key

It is possible to use multiple keys for signing and verifying. You can use the flag --name with the name you want to use as extra parameter, e.g.:

    $ php bin/app.php --sign --name production foo.json

The --name flag also works for --verify and --show. Not specifying the --name flag will fall back to the "default" key.

Implementation

The PECL module libsodium is used. This module will be added to the default PHP installation starting with PHP 7.2.

This crypto library can be used on many platforms and in many programming languages and is considered very secure.