Validación de firmas digitales

Ejemplo validación.ipynb

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   "source": [
    "## Ejemplo de verificación de firma\n",
    "\n",
    "Este programa valida firmas digitales generadas mediante la función `openssl_sign` de PHP usando el algoritmo SHA256."
   ]
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     "text": [
      "Certificado válido\n"
     ]
    }
   ],
   "source": [
    "from base64 import b64encode,b64decode\n",
    "\n",
    "from Crypto.Hash import SHA256\n",
    "from Crypto.Signature import PKCS1_v1_5\n",
    "from Crypto.PublicKey import RSA\n",
    "\n",
    "# La llave pública de la autoridad que firma el certificado\n",
    "public_key = \"\"\"-----BEGIN PUBLIC KEY-----\n",
    "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDjzf06Cgd8KZevWQVraikO5u+3\n",
    "r+JzygUB9ooAml2CV4jnU3KxQZjGvnLBi2EYzx43hkz6O6xvYDn17+gJs5OnjhP0\n",
    "iWj0qgoN1m3tBG71/Vzs+1sBs6T26Q3/imj2NZ9xlkq0oECsobN/iUKxtYnOXLuv\n",
    "qVxkeNsqwrKVdoHTswIDAQAB\n",
    "-----END PUBLIC KEY-----\"\"\"\n",
    "\n",
    "# El certificado a verificar\n",
    "cert = \"\"\"###\n",
    "-id_cert:d45bde575fafad5895e5ff9e64af4c3e563aa5d360d4289c2745f5c00959223f\n",
    "-id_elec:gatoperro\n",
    "-roles:{Estudiante:2009-1,Profesor:2021-1}\n",
    "--- FIRMA ---\n",
    "yamW5Ew+C71srrsGNVQF69QMYbnYA94ll6LAVJZWBa0mzajr6Uaa/xH3/SqD4RzCFe8Jj2l5X5Q3yDToFYw40hqml84Yvq4jjpO8T3NoHuuh2iexaZGvht3vbi0Y3Lu6Dfy+ZJ9SY8njO+rJ+S3IdktF+GYopR4ysOKqsG99iUo=\n",
    "###\"\"\"\n",
    "\n",
    "# Separar la firma y el contenido del mensage\n",
    "message, signature = cert.strip(\"#\\n\").split(\"\\n--- FIRMA ---\\n\")\n",
    "message = bytes(message,'utf-8')\n",
    "signature = bytes(signature,'utf-8')\n",
    "\n",
    "# Obtener un resumen del mensaje\n",
    "digest = SHA256.new()\n",
    "digest.update(message)\n",
    "\n",
    "# Generar el verificador de firmas\n",
    "rsapubkey = RSA.importKey(public_key) \n",
    "verifier = PKCS1_v1_5.new(rsapubkey)\n",
    "\n",
    "# Verificar la firma\n",
    "verified = verifier.verify(digest, b64decode(signature))\n",
    "\n",
    "if verified:\n",
    "    print(\"Certificado válido\")\n",
    "else:\n",
    "    print(\"Certificado no válido\")"
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