php - OpenSSL won't create private keys?

Question

Okay, well, this is my first time working with encryption on a project. I am using my hosting provider for SSL, but I also want to encrypt portions of the database that are sensitive. For this, I was told to use OpenSSL. I am testing it on my localhost (WAMP), and have installed OpenSSL and turned on the PHP and Apache SSL mods. Okay, so i've been following tutorials and, using several suggested methods, have been able to generate the public key and store it as a file. For some reason, I can't seem to generate the private key. I will post two versions of code that i've tried:

// generate private key
$privateKey = openssl_pkey_new(array(
    'private_key_bits' => 1024,
    'private_key_type' => OPENSSL_KEYTYPE_RSA,
));
// write private key to file
openssl_pkey_export_to_file($privateKey, 'private.key');
// generate public key from private key
$publicKey = openssl_pkey_get_details($privateKey);
// write public key to file
file_put_contents('public.key', $publicKey['key']);
// clear key
echo $privateKey;

?>

This generates a public.key file, but provides me the warnings "openssl_pkey_export_to_file(): cannot get key from parameter 1:" and " openssl_pkey_get_details() expects parameter 1 to be resource, boolean."

I also tried an alternative method:

$config = array(
    "config" => "E:/wamp/bin/apache/apache2.2.22/conf/openssl.cnf",
    "digest_alg" => "sha512",
    "private_key_bits" => 1024,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
);

// Create the private and public key
$res = openssl_pkey_new($config);

// Extract the private key from $res to $privKey
openssl_pkey_export($res, $privKey, NULL);
echo "Private Key: ".$privKey;
// Extract the public key from $res to $pubKey
$pubKey = openssl_pkey_get_details($res);
$pubKey = $pubKey["key"];
echo "Public Key: ".$pubKey;
$data = 'plaintext data goes here';
echo "Data: ".$data;
// Encrypt the data to $encrypted using the public key
openssl_public_encrypt($data, $encrypted, $pubKey);
echo "Encrypted: ".$encrypted;
// Decrypt the data using the private key and store the results in $decrypted
openssl_private_decrypt($encrypted, $decrypted, $privKey);

echo "Decrypted: ".$decrypted;

This was supposed to echo everything, unfortunately my result was a blank private key, a fine public key, plaintext, and encrypted text, and an error when trying to decrypt: "openssl_private_decrypt(): key parameter is not a valid private key"

Clearly, i'm having a problem with private key creation. I've searched the internet thoroughly and haven't been able to fix it, even though I've implemented simple code that seems to work for everyone else.

Thanks in advance, Elie Zeitouni

Answer 1

I know that it has been a while and you may have already solved it but I think that my answer can be helpful for other people who faced the same problem (Like I did).

So if you take a look at the openssl_pkey_export() documentation you can find that it takes four different parameters. If we take a look at your second implementation we can see that you have only provided three.

openssl_pkey_export($res, $privKey, NULL);

This would be just as fine if only your server have the right environment variables for OPENSSL_CONF. Linking to the openssl.cnf file, which as quoted in the README-SSL.txt file that is downloaded with XAMPP is required to make use of CSR and key generation functions from PHP.

To use the CSR and key generation functions from PHP, you will need to install an openssl.cnf file. We have included a sample file that can be used for this purpose in this folder alongside this readme file.

For this reason just as you did for the openssl_pkey_new($config); you must create a associative array containing the config => '/path/to/openssl.cnf'. Just like this:

openssl_pkey_export($res, $privKey, NULL, $config);

I would like to also add that the path of openssl.cnf in my case is inside:

C:xamppphpextrasopensslopenssl.cnf

Inside here you will also be able to find a README-SSL.txt file which give a good explaination of how to configure OPENSSL.

Hope it helps. :)