PHP Manual: Sign a CSR with another certificate (or itself) and generate a certificate

Description

OpenSSLCertificatefalse openssl_csr_sign(
    OpenSSLCertificateSigningRequeststring $csr,
    OpenSSLCertificatestringnull $ca_certificate,
    #[\SensitiveParameter]OpenSSLAsymmetricKeyOpenSSLCertificatearraystring $private_key,
    int $days,
    arraynull $options = null,
    int $serial = 0,
    stringnull $serial_hex = null
)

openssl_csr_sign generates an x509 certificate from the given CSR.

Note: You need to have a valid openssl.cnf installed for this function to operate correctly. See the notes under the installation section for more information.

Parameters

csr: A CSR previously generated by openssl_csr_new. It can also be the path to a PEM encoded CSR when specified as file://path/to/csr or an exported string generated by openssl_csr_export.
ca_certificate: The generated certificate will be signed by ca_certificate. If ca_certificate is null, the generated certificate will be a self-signed certificate.
private_key: private_key is the private key that corresponds to ca_certificate.
days: days specifies the length of time for which the generated certificate will be valid, in days.
options: You can finetune the CSR signing by options. See openssl_csr_new for more information about options.
serial: An optional the serial number of issued certificate. If not specified it will default to 0.
serial_hex: An optional hexadecimal string representing the serial number of the issued certificate. If set, it takes precedence over the serial parameter value. If not specified or set to null, the serial parameter value is used instead.

Return Values

Returns an OpenSSLCertificate on success, false on failure.

Changelog

Version	Description
8.4.0	The `serial_hex` parameter is added.
8.0.0	On success, this function returns an OpenSSLCertificate instance now; previously, a resource of type `OpenSSL X.509` was returned.
8.0.0	`csr` accepts an OpenSSLCertificateSigningRequest instance now; previously, a resource of type `OpenSSL X.509 CSR` was accepted.
8.0.0	`ca_certificate` accepts an OpenSSLCertificate instance now; previously, a resource of type `OpenSSL X.509` was accepted.
8.0.0	`private_key` accepts an OpenSSLAsymmetricKey or OpenSSLCertificate instance now; previously, a resource of type `OpenSSL key` or `OpenSSL X.509` was accepted.

Examples

Example #1 openssl_csr_sign example - signing a CSR (how to implement your own CA)

<?php
// Let's assume that this script is set to receive a CSR that has
// been pasted into a textarea from another page
$csrdata = $_POST["CSR"];

// We will sign the request using our own "certificate authority"
// certificate.  You can use any certificate to sign another, but
// the process is worthless unless the signing certificate is trusted
// by the software/users that will deal with the newly signed certificate

// We need our CA cert and its private key
$cacert = "file://path/to/ca.crt";
$privkey = array("file://path/to/ca.key", "your_ca_key_passphrase");

$usercert = openssl_csr_sign($csrdata, $cacert, $privkey, 365, array('digest_alg'=>'sha256') );

// Now display the generated certificate so that the user can
// copy and paste it into their local configuration (such as a file
// to hold the certificate for their SSL server)
openssl_x509_export($usercert, $certout);
echo $certout;

// Show any errors that occurred here
while (($e = openssl_error_string()) !== false) {
    echo $e . "\n";
}
?>