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

    up
    10
    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.
    up
    6
    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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