openssl_seal

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

openssl_seal — Sellar (encriptar) información

Descripción

openssl_seal(
    string $data,
    string &$sealed_data,
    array &$env_keys,
    array $pub_key_ids,
    string $method = "RC4"
): int

openssl_seal() sella (encripta) la información dada por data mediante el método dado por method con una clave secreta generada aleatoriamente. La clave es encriptada con cada clave pública asociada con los identificadores de pub_key_ids y cada clave encriptada es devuelta en env_keys. Esto significa que se puede enviar información sellada a múltiples destinatarios (siempre que se hayan obtenido sus claves públicas). Cada destinatario debe recibir tanto la información sellada como la clave de sobre que fue encriptada con la clave publica del destinatario.

Parámetros

data: Los datos a sellar.
sealed_data: Los datos sellados.
env_keys: Un array de claves encriptadas.
pub_key_ids: Un array de identificadores de recursos de clave pública.
method: El método de cifrado.

Valores devueltos

Devuelve la longitud de la información sellada si se tuvo éxito, o false si se produjo un error. Si se tuvo éxito, la información sellada es devuelta en sealed_data, y las claves de sobre en env_keys.

Ejemplos

Ejemplo #1 Ejemplo de openssl_seal()

<?php
// se asume que $data contiene la información que va a ser sellada

// traer las claves públicas para nuestros destinatarios, y prepararlas
$fp = fopen("/src/openssl-0.9.6/demos/maurice/cert.pem", "r");
$cert = fread($fp, 8192);
fclose($fp);
$pk1 = openssl_get_publickey($cert);
// Repetir para el segundo destinatario
$fp = fopen("/src/openssl-0.9.6/demos/sign/cert.pem", "r");
$cert = fread($fp, 8192);
fclose($fp);
$pk2 = openssl_get_publickey($cert);

// sellar el mensaje, sólo los propietarios de $pk1 y $pk2 pueden desencriptar $sealed
// con las claves $ekeys[0] y $ekeys[1] respectivamente.
openssl_seal($data, $sealed, $ekeys, array($pk1, $pk2));

// liberar las claves de la memoria
openssl_free_key($pk1);
openssl_free_key($pk2);
?>

Historial de cambios

Versión	Descripción
5.3.0	Se añadió el parámetro `method`.

Ver también

openssl_open() - Abre información sellada

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User Contributed Notes 6 notes

down

Dominik M. ¶

4 years ago

Please note that openssl_seal() cannot be used for EC encryption.
Took me literally two hours to find out because the OpenSSL documentation is so bad.

down

amer.alhabsi AT gmail DOT com ¶

8 years ago

while the default is using RC4, it is possible to use other more secure algorithms. These are specified as the fifth parameter. Also, one needs to add an initialization vector (random bytes). Eg.

<?php
    $data = "This is top secret.";
    // fetch public keys for our recipients, and ready them
    $cert = file_get_contents('./cert.pem');

    $pk1 = openssl_get_publickey($cert);
    $iv = openssl_random_pseudo_bytes(32);
    openssl_seal($data, $sealed, $ekeys, array($pk1), "AES256", $iv);

    // free the keys from memory
    openssl_free_key($pk1);
    echo base64_encode($sealed);
?>

down

aaron dot lawrence at umajin dot com ¶

3 years ago

Some critical details that are not in the docs, nor widely written about elsewhere.

- The envelope key is a 128-bit RSA key, randomly generated.
- The data is encrypted with (A)RC4 using the envelope key.
- The envelope key is encrypted for transmission with PKCS1 v1.5. It is NOT the OAEP padding variant.  PKCS1 v1.5 is even older, and not widely supported anymore.

At least this was true for openssl_seal in PHP 7.2 that we are using.

(Note: In Python you can decrypt this envelope key with the Cryptography package, using padding.PKCS1v15())

The combination of RC4 and PKCS1 v1.5 make this function actually semi-obsolete for security use in my opinion.

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devel@no-spam ¶

19 years ago

"seals (encrypts) data by using RC4 with a randomly generated secret key"
It should be noted that the randomly generated secret key is 128 bits long (openssl: EVP_rc4(void):  RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.)

down

bowfingermail at gmx dot net ¶

9 years ago

According to several sources (e.g. crypto101.io or Wikipedia) RC4 is not safe and not supposed to be used anymore.
So, shouldn't openssl_seal use another stream cipher in place of RC4?

down

-4

hfuecks at nospam dot org ¶

17 years ago

openssl_seal() can work well when you need to pass data securely to other platforms / languages. What openssl_seal() does is;

1. Generate a random key
2. Encrypt the data symmetrically with RC4 using the random key
3. Encrypt the random key itself with RSA using the public key / certificate
4. Returns the encrypted data and the encrypted key

So to decrypt the steps are simply;

1. Decrypt the key using RSA and your private key
2. Decrypt the data using RC4 and the decrypted key

The trickiest part may be figuring out how handle the private key - BouncyCastle ( http://www.bouncycastle.org/ ) provides a PEMReader for Java and C# while Not Yet commons-ssl ( http://juliusdavies.ca/commons-ssl/ ) has a KeyStoreBuilder to build Java keystores out of a PEM certificate.

A complete example in Java is described at http://blog.local.ch/archive/2007/10/29/openssl-php-to-java.html

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