Examine source code of Assinador do ePGM

{
  "name": "Assinador do ePGM",
  "version": "1.4resigned1",
  "manifest_version": 2,
  "description": "Assinador de documentos da PGM de Fortaleza.",
  "applications": {
    "gecko": {
      "id": "assinador@epgm.pgm.for.br",
      "strict_min_version": "50.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "128": "icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://homologacao.epgm.pgm.for.br/*/*/*",
        "http://epgm.pgm.fortaleza.ce.gov.br/",
        "http://epgm.pgm.for.br/usuarios/entrar",
        "http://epgm/",
        "*://*/*"
      ],
      "js": [
        "content-script.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "tabs",
    "*://*/*",
    "nativeMessaging"
  ]
}