openssl_verify

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

openssl_verify — Verificar una firma

Descripción

openssl_verify(
    string $data,
    string $signature,
    mixed $pub_key_id,
    mixed $signature_alg = OPENSSL_ALGO_SHA1
): int

openssl_verify() verifica que la firma signature es correcta para la información data especificada usando la clave pública asociada con pub_key_id. Ésta debe ser la clave pública que se corresponde con la clave privada usada para firmar.

Parámetros

data

El string de datos utilizado anteriormente para generar la firma.

signature

Un string binario puro generado por openssl_sign() o por medios similares

pub_key_id

resource - una clave, devuelta por openssl_get_publickey()

string - una clave con formato PEM; p.ej., "-----BEGIN PUBLIC KEY----- MIIBCgK..."

signature_alg

int - uno de estos Algoritmos de firma.

string - un string válido devuelto por openssl_get_md_methods(); p.ej., "sha1WithRSAEncryption" o "sha512".

Valores devueltos

Devuelve 1 si la firma es correcta, 0 si es incorrecta, y -1 si se produjo un error.

Historial de cambios

Versión	Descripción
5.2.0	Se añadió el parámetro `signature_alg`.

Ejemplos

Ejemplo #1 Ejemplo de openssl_verify()


<?php
// se asume que $data y $signature contienen la información y la firma

// obtener la clave pública desde el certifiado y prepararla
$pubkeyid = openssl_pkey_get_public("file://src/openssl-0.9.6/demos/sign/cert.pem");

// especificar si la firma es correcta o no
$ok = openssl_verify($data, $signature, $pubkeyid);
if ($ok == 1) {
    echo "buena";
} elseif ($ok == 0) {
    echo "mala";
} else {
    echo "alarmante, error verificando la firma";
}
// liberar la clave de la memoria
openssl_free_key($pubkeyid);
?>

Ejemplo #2 openssl_verify() example


<?php
// datos que se quieren firmar
$datos = 'mis datos';

// crear unas claves pública y privada nuevas
$private_key_res = openssl_pkey_new(array(
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
));
$details = openssl_pkey_get_details($private_key_res);
$public_key_res = openssl_pkey_get_public($details['key']);

// crear la firma
openssl_sign($datos, $firma, $private_key_res, "sha1WithRSAEncryption");

// comprobar la firma
$ok = openssl_verify($datos, $firma, $public_key_res, OPENSSL_ALGO_SHA1);
if ($ok == 1) {
    echo "válida";
} elseif ($ok == 0) {
    echo "no válida";
} else {
    echo "error: ".openssl_error_string();
}
?>

Ver también

openssl_sign() - Genera una firma

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User Contributed Notes 8 notes

down

Stiv ¶

16 years ago


I've finally found a way to verify signature. Sample in the documentation doesn't work. Code bellow DOES work :)

<?php
// $data is assumed to contain the data to be signed

// fetch certificate from file and ready it
$fp = fopen("path/file.pem", "r");
$cert = fread($fp, 8192);
fclose($fp);

// state whether signature is okay or not
// use the certificate, not the public key
$ok = openssl_verify($data, $signature, $cert);
if ($ok == 1) {
    echo "good";
} elseif ($ok == 0) {
    echo "bad";
} else {
    echo "ugly, error checking signature";
}
?>

down

mikey at badpenguins dot com ¶

12 years ago


I spent days scouring the php openssl documentation trying to figure out how to do what sounds like a simple task - given two PEM encoded certificates, is one the signer of the other?  Nowhere in the openssl_verify() documentation or comments is it explained where to obtain the signature of an existing certificate.  The openssl_x509_parse() function looked promising, but it is an unstable API that may change.

I had to write my own code to determine if one cert signed another, it is located here: http://badpenguins.com/source/misc/isCertSigner.php?viewSource

In a nutshell here is what I learned...

The signature data in a signed X.509 certificate contains DER formatted data about the signature that is encrypted with the signers public key.  The data contains a hash of the original subject certificate and information about what encryption algorithm was used to create the signature.

So you need to get this signature data and a copy of the original certificate with the issuer and signature sequences removed.  Hash a copy of the original certificate (sans issuer/signature sequences) with the same algorithm the issuer used and if the hashes match, you have the issuer cert that signed the certificate.

down

steve dot venable at lmco dot com ¶

20 years ago


A note about the openssl_verify() (and some of the other functions).  The public key comes from a certificate in any of the support formats (as the example shows, use openssl_get_publickey() to get the resource id).  But after some trial and error I found the signature string MUST BE BINARY.  While no error occurs, passing a base64-formatted signature string (PEM format?), you simply get a mismatch.  When I did the base64 decode myself, the verify returned a match (return value 1).  You can simply drop the begin/end lines and take the output of the 'base64_decode()' function.

down

phpdev at fpierrat dot fr ¶

1 year ago


As stated from the doc: "Returns 1 if the signature is correct, 0 if it is incorrect, and -1 or false on error. "

In the second example as a well as in Stiv's note, following condition will match for both 0 or false, which have different meaning:
elseif ($ok == 0) {
    echo "bad";
}

On should do an identical test here (===) instead of an equal test (==):
elseif ($ok === 0) {
    echo "bad";
}
---
var_dump(0==false); //==> true
var_dump(0===false);//==> false

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peter dot labos at gmail dot com ¶

4 years ago


openssl_verify() is populating openssl_error_string() even on false. 

When openssl_verify() returns 0, openssl_error_string() is populated with 1.
I spent lot of time to understand, while my next call to openssl was failing with checks for error.

<?php
$c = file_get_contents($filename);
$publicKey = openssl_pkey_get_public($c);
$result = openssl_verify('freedom', 'someirrelevantnosign', $publicKey);

$error = "";

while ($msg = openssl_error_string() !== false) {
    $error .= $msg;
}

if (!empty($error)) {
    echo $error; // 1
}

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attila dot m dot magyar at gmail dot com ¶

8 years ago


mikey at badpenguins dot com -- validating an X509 certificate chain in php seems to be possible with openssl_x509_checkpurpose()

down

jeremie dot gomez at gmail dot com ¶

11 years ago


You can actually use the public key as third parameter and not the certificate.

If you can't make it work, make sure that :

1) Your public key is well formatted. It seems that it must have the ----BEGIN PUBLIC KEY---- and ----END PUBLIC KEY----

2) Your signature is in binary format. You can use the php base64_decode for this.

down

meint dot post at bigfoot dot com ¶

21 years ago


Anbybody trying to get a Win32 CryptoAPI based digital signature component to work with the openssl_verify() function should be aware that the CryptoAPI PKCS1 (RSA) method uses bytes in reverse order while the openssl_verify() method expects a correctly formatted PKCS1 digital signature (as should be). I learned this the hard way and it took me some time to dig this out. A simple solution in VBScript to reverse the byte order:



N = Len(Blob.Hex)



' reverse bytes in the signature using Hex format 

For i = 1 To N - 1 Step 2 

    s = Mid(Blob, i, 2) & s 

Next 



s contains the digital signature in reverse order. Blob is an arbitrary binary container.



Send the signature off in Hex format and use a hex2bin method in PHP to convert to the correct format for openssl_verify(), i.e.



function hex2bin($data) {



    $len = strlen($data);

    return pack("H" . $len, $data);



} 



That's it, hope it helps out. BTW I used ASPEncrypt to toy around with on Win32 platform. Works only with Internet Explorer but you could also use a Java applet and have none of the abovementioned problems :-)

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