openssl_verify

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

openssl_verify — Verifica assinatura

Descrição

openssl_verify() verifica que a assinatura em signature está correta para os dados especificados em data usans a chave pública public_key. Esta precisa ser a chave pública correspondente à chave privada utilizada para assinatura.

Parâmetros

data

A sequência de dados usada para gerar a assinatura anteriormente

signature

Uma string binária bruta, gerada por openssl_sign() ou meios similares

public_key

OpenSSLAsymmetricKey - uma chave, retornada por openssl_get_publickey()

string - uma chave no formato PEM (por exemplo -----BEGIN PUBLIC KEY----- MIIBCgK...)

algorithm

int - um destes Algoritmos de Assinatura.

string - uma string válida retornada por openssl_get_md_methods(), por exemplo, "sha1WithRSAEncryption" ou "sha512".

Valor Retornado

Retorna 1 se a assinatura estiver correta, 0 se estiver incorreta e -1 ou false em caso de erro.

Registro de Alterações

Versão	Descrição
8.0.0	`public_key` agora aceita uma instância de OpenSSLAsymmetricKey ou OpenSSLCertificate; anteriormente, um resource do tipo `OpenSSL key` ou `OpenSSL X.509` era aceito.

Exemplos

Exemplo #1 Exemplo de openssl_verify()

<?php
// Presume-se que $data e $signature contenham os dados e a assinatura

// busca a chave pública do certificado e a prepara
$pubkeyid = openssl_pkey_get_public("file://src/openssl-0.9.6/demos/sign/cert.pem");

// afirma se a assinatura está correta ou não
$ok = openssl_verify($data, $signature, $pubkeyid);
if ($ok == 1) {
    echo "boa";
} elseif ($ok == 0) {
    echo "ruim";
} else {
    echo "erro ao verificar assinatura";
}
// libera a chave da memória
openssl_free_key($pubkeyid);
?>

Exemplo #2 Exemplo de openssl_verify()

<?php
// dados que você deseja assinar
$data = 'my data';

// cria uma nova chave privada e pública
$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']);

// cira assinatura
openssl_sign($data, $signature, $private_key_res, "sha256WithRSAEncryption");

// verifica assinatura
$ok = openssl_verify($data, $signature, $public_key_res, OPENSSL_ALGO_SHA256);
if ($ok == 1) {
    echo "válida";
} elseif ($ok == 0) {
    echo "inválida";
} else {
    echo "erro: ".openssl_error_string();
}
?>

Veja Também

openssl_sign() - Gera assinatura

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Notas Enviadas por Usuários (em inglês) 8 notes

down

Stiv ¶

18 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 ¶

14 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

meint dot post at bigfoot dot com ¶

23 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 :-)

down

peter dot labos at gmail dot com ¶

6 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
}

down

steve dot venable at lmco dot com ¶

22 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 ¶

3 years 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

down

attila dot m dot magyar at gmail dot com ¶

10 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 ¶

13 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.

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