How to Use Openssl_x509_parse And Openssl_x509_verify on Php?

12 minutes read

To use openssl_x509_parse and openssl_x509_verify functions in PHP, you need to have the OpenSSL extension enabled in your PHP installation.

  1. openssl_x509_parse: This function parses an X.509 certificate and returns an associative array with its information. It allows you to extract various details from the certificate, such as subject, issuer, validity period, public key information, extensions, etc.


Here's an example of how to use openssl_x509_parse:

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$certPath = '/path/to/certificate.crt';
$certData = file_get_contents($certPath);

$certificateInfo = openssl_x509_parse($certData);
print_r($certificateInfo);


By specifying the path to the X.509 certificate file and reading its contents, you can pass it to the openssl_x509_parse function. It will then return an array containing information about the certificate, which you can further process based on your requirements.

  1. openssl_x509_verify: This function verifies the signature of an X.509 certificate using the certificate's public key. It can check whether the certificate has been signed by a trusted authority or if the signature is valid.


Here's an example of how to use openssl_x509_verify:

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$certPath = '/path/to/certificate.crt';
$certData = file_get_contents($certPath);

$certStorePath = '/path/to/trusted/certificates/';
$certStore = openssl_pkey_new(array(
    'verify_peer' => true,
    'capath' => $certStorePath
));

$verifyResult = openssl_x509_verify($certData, $certStore);
if ($verifyResult === 1) {
    echo "Certificate is valid and trusted.";
} elseif ($verifyResult === 0) {
    echo "Certificate is valid, but not trusted.";
} else {
    echo "Certificate verification failed.";
}


In this example, you first need to load a set of trusted certificates or a directory containing them. Then, by passing the X.509 certificate data and the certificate store, you can call openssl_x509_verify. It will determine if the certificate is valid, trusted, or if the verification fails.


Make sure to adjust the paths and the logic for loading trusted certificates based on your specific setup.


These functions provide a way to extract and verify information from X.509 certificates within a PHP application when the OpenSSL extension is available.

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What is the format of the "validFrom" key in the returned array from openssl_x509_parse in PHP?

The "validFrom" key in the returned array from the openssl_x509_parse function in PHP contains the valid start date for the certificate.


The format of the "validFrom" key is a Unix timestamp representing the start date of the certificate's validity period. It is an integer value that represents the number of seconds elapsed since January 1, 1970 (also known as the Unix epoch).


You can convert this Unix timestamp to a human-readable date and time format using the date function in PHP. Here is an example:

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$certificate = openssl_x509_parse($certData);
$validFromTimestamp = $certificate['validFrom_time_t'];
$validFrom = date('Y-m-d H:i:s', $validFromTimestamp);

echo $validFrom; // Outputs the start date of the certificate's validity period in a formatted date/time string


This example retrieves the Unix timestamp from the "validFrom_time_t" key and converts it to a human-readable date and time using the date function. The resulting string is then printed.


How to validate a certificate against a specific certificate authority using openssl_x509_verify in PHP?

To validate a certificate against a specific certificate authority in PHP using the openssl_x509_verify function, you can follow the steps below:

  1. Read the CA certificate file using the openssl_x509_read function. This function reads the certificate and returns a resource identifier for the certificate. $caCert = openssl_x509_read(file_get_contents('path/to/ca_certificate.crt'));
  2. Read the certificate you want to validate using the openssl_x509_read function. This function also returns a resource identifier for the certificate. $cert = openssl_x509_read(file_get_contents('path/to/certificate.crt'));
  3. Create an array of trusted CA certificates using the $caCert identifier created in step 1. $caCertArray = array($caCert);
  4. Configure the certificate verification options. You can set options such as the trusted CA certificates, the subject certificate, and any flags that control the verification process. $options = array( 'cafile' => null, // or path to a file containing trusted CA certificates 'capath' => null, // or path to a directory containing trusted CA certificates 'cert' => $cert, // the identifier of the subject certificate in step 2 'verify_peer' => true, // enable peer certificate verification );
  5. Validate the subject certificate against the CA using the openssl_x509_verify function. $result = openssl_x509_verify($cert, $caCertArray, $options); The $result variable will contain the result of the verification. A return value of 1 indicates success, 0 indicates a verification failure, and -1 indicates an error.
  6. Check the result and handle the verification outcome accordingly. if ($result === 1) { echo 'Certificate is valid and trusted by the specified CA.'; } elseif ($result === 0) { echo 'Certificate is not valid or not trusted by the specified CA.'; } elseif ($result === -1) { echo 'An error occurred during certificate verification.'; }


Note: Make sure you have the openssl extension enabled in your PHP installation.


Additionally, you may need to load the CA certificates using openssl.cafile and openssl.capath directives in the php.ini file or using ini_set function.


How to handle certificate revocation lists (CRLs) using openssl_x509_verify in PHP?

To handle Certificate Revocation Lists (CRLs) using openssl_x509_verify in PHP, you can follow these steps:

  1. Load the certificate and the CRL file:
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$certificate = file_get_contents('path/to/certificate.pem');
$crl = file_get_contents('path/to/crl.pem');


  1. Create an OpenSSL x509 resource from the loaded certificate:
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$certificateResource = openssl_x509_read($certificate);


  1. Create an OpenSSL X509_CRL resource from the loaded CRL:
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$crlResource = openssl_crl_read($crl);


  1. Set the CRL for the certificate verification context:
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$context = openssl_x509_checkpurpose($certificateResource, X509_PURPOSE_ANY, [$crlResource]);


  1. Verify the certificate using the certificate verification context:
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$result = openssl_x509_verify($certificateResource, -1, $context);


  1. Check the verification result:
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if ($result === 1) {
    echo "Certificate is valid.";
} elseif ($result === 0) {
    echo "Certificate is invalid.";
} else {
    echo "An error occurred while verifying the certificate.";
}


  1. Free the resources:
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openssl_x509_free($certificateResource);
openssl_crl_free($crlResource);


Note: Make sure to replace "path/to/certificate.pem" and "path/to/crl.pem" with the actual paths to your certificate and CRL files.


These steps will allow you to handle Certificate Revocation Lists (CRLs) using openssl_x509_verify in PHP.


What is the difference between openssl_x509_parse and openssl_x509_read in PHP?

The openssl_x509_parse and openssl_x509_read functions in PHP are both used for manipulating X.509 certificates, but they have different functions and return values:

  1. openssl_x509_parse: This function parses an X.509 certificate and extracts detailed information about it. The return value is an associative array containing information such as the subject name, issuer name, validity period, and extensions. It does not read the certificate from a file or string directly. You need to use openssl_x509_read to read the certificate first before using this function.
  2. openssl_x509_read: This function reads an X.509 certificate from a file or string. The return value is a resource handle that can be used for further operations such as parsing, verifying, or extracting information using other OpenSSL functions (like openssl_x509_parse). It can read certificates from a file (e.g., "cert.pem") or from a string containing the certificate itself.


In summary, openssl_x509_parse is used to extract information from a parsed X.509 certificate, while openssl_x509_read is used to read the X.509 certificate into a resource handle that can be used for various operations, including parsing.


How to check if a certificate is valid or expired using openssl_x509_parse in PHP?

To check if a certificate is valid or expired using openssl_x509_parse in PHP, you can follow these steps:

  1. Load the certificate from a file or a string using openssl_x509_parse function:
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$certData = file_get_contents('/path/to/certificate.pem'); // Load certificate from file
// OR
$certData = '-----BEGIN CERTIFICATE----- ... -----END CERTIFICATE-----'; // Load certificate from string

$certInfo = openssl_x509_parse($certData);


  1. Extract the start and end dates from the certificate information:
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$validFrom = $certInfo['validFrom_time_t'];
$validTo = $certInfo['validTo_time_t'];


  1. Get the current timestamp:
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$currentTimestamp = time();


  1. Compare the current timestamp with the start and end dates to determine if the certificate is valid or expired:
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if ($currentTimestamp < $validFrom) {
    echo "Certificate is not yet valid.";
} elseif ($currentTimestamp > $validTo) {
    echo "Certificate has expired.";
} else {
    echo "Certificate is valid.";
}


So, the full code would be:

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$certData = file_get_contents('/path/to/certificate.pem');
$certInfo = openssl_x509_parse($certData);

$validFrom = $certInfo['validFrom_time_t'];
$validTo = $certInfo['validTo_time_t'];

$currentTimestamp = time();

if ($currentTimestamp < $validFrom) {
    echo "Certificate is not yet valid.";
} elseif ($currentTimestamp > $validTo) {
    echo "Certificate has expired.";
} else {
    echo "Certificate is valid.";
}


Note: Make sure to replace /path/to/certificate.pem with the actual path to your certificate file.

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