openssl_x509_checkpurpose

(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)

openssl_x509_checkpurpose — Verifies if a certificate can be used for a particular purpose

Description

openssl_x509_checkpurpose(
    OpenSSLCertificate|string $certificate,
    int $purpose,
    array $ca_info = [],
    ?string $untrusted_certificates_file = null
): bool|int

openssl_x509_checkpurpose() examines a certificate to see if it can be used for the specified purpose.

Parameters

certificate

The examined certificate.

purpose

**openssl_x509_checkpurpose()** purposes
Constant	Description
X509_PURPOSE_SSL_CLIENT	Can the certificate be used for the client side of an SSL connection?
X509_PURPOSE_SSL_SERVER	Can the certificate be used for the server side of an SSL connection?
X509_PURPOSE_NS_SSL_SERVER	Can the cert be used for Netscape SSL server?
X509_PURPOSE_SMIME_SIGN	Can the cert be used to sign S/MIME email?
X509_PURPOSE_SMIME_ENCRYPT	Can the cert be used to encrypt S/MIME email?
X509_PURPOSE_CRL_SIGN	Can the cert be used to sign a certificate revocation list (CRL)?
X509_PURPOSE_ANY	Can the cert be used for Any/All purposes?

These options are not bitfields - you may specify one only!

ca_info

ca_info should be an array of trusted CA files/dirs as described in Certificate Verification.

untrusted_certificates_file

If specified, this should be the name of a PEM encoded file holding certificates that can be used to help verify the certificate, although no trust is placed in the certificates that come from that file.

Return Values

Returns true if the certificate can be used for the intended purpose, false if it cannot, or -1 on error.

Changelog

Version	Description
8.0.0	`certificate` accepts an OpenSSLCertificate instance now; previously, a resource of type `OpenSSL X.509` was accepted.
8.0.0	`untrusted_certificates_file` is nullable now.

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User Contributed Notes 2 notes

down

dingyuan at tencent dot com ¶

4 years ago

in one word ：if you set $purpose=0, you can use this function to verify certificate chain.

====================================================================

I want to verify a certificate chain. just like this: 
userCert.pem => middleCert.pem => rootCert.pem

I figured that none of these openssl functions provide this function directly. And some friends have same need as me,  "mikey at badpenguins dot com" even write his own code to verify certificate chain(you can see notes below openssl_verify). 

and I notice a note which has '-3' likes below openssl_verify, it says "validating an X509 certificate chain in php seems to be possible with openssl_x509_checkpurpose()", and I read the source code about this function, the given constant var about $purpose (like X509_PURPOSE_SSL_CLIENT ) is 1-7, and if you set $purpose among 1-7, you cannot verify the cert chain. Set $purpose=0 can get the truly result about verify a cert chain.

and I give that '-3' note a thumb-up, now it has -2 , lol.

down

adr at NOSPAM dot entropymatrix dot com ¶

11 years ago

The following is an example usage of openssl_x509_checkpurpose. It is equivalent to the openssl verify command as follows:
openssl verify -CApath $openssl_cadir -purpose sslserver $openssl_crtfile

<?php
$openssl_crtfile='auth.combined.pem';
$openssl_cadir='./ca';

$x509_res = openssl_x509_read(file_get_contents($openssl_crtfile));
if(empty($x509_res)) {
        echo 'x509 cert could not be read'."\n";
}
$valid = openssl_x509_checkpurpose($x509_res,X509_PURPOSE_SSL_SERVER,array($openssl_cadir));
if ($valid === true) {
        echo 'Certificate is valid for use as SSL server'."\n";
} else {
        echo 'Certificate validation returned'.$valid."\n";
}
?>

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