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";
}
?>
openssl_verify
(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)
openssl_verify — Verificar una firma
Descripción
openssl_verify(
string
string
mixed
mixed
): int
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();
}
?>
add a note
User Contributed Notes 8 notes
Stiv ¶
16 years ago
steve dot venable at lmco dot com ¶
19 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.
mikey at badpenguins dot com ¶
11 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.
phpdev at fpierrat dot fr ¶
8 months 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
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 $error; // 1
}
meint dot post at bigfoot dot com ¶
20 years ago
Anbybody trying to get a Win32 CryptoAPI based digital signature component to work with the openssl_verify() function should be aware that the CryptoAPI PKCS1 (RSA) method uses bytes in reverse order while the openssl_verify() method expects a correctly formatted PKCS1 digital signature (as should be). I learned this the hard way and it took me some time to dig this out. A simple solution in VBScript to reverse the byte order:
N = Len(Blob.Hex)
' reverse bytes in the signature using Hex format
For i = 1 To N - 1 Step 2
s = Mid(Blob, i, 2) & s
Next
s contains the digital signature in reverse order. Blob is an arbitrary binary container.
Send the signature off in Hex format and use a hex2bin method in PHP to convert to the correct format for openssl_verify(), i.e.
function hex2bin($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 :-)
attila dot m dot magyar at gmail dot com ¶
7 years ago
mikey at badpenguins dot com -- validating an X509 certificate chain in php seems to be possible with openssl_x509_checkpurpose()
jeremie dot gomez at gmail dot com ¶
10 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.
