Paypal development. encrypt transactions. php p12 - php

Question

when i take a look at the paypal documentation, they say "Note that the PayPal SDK for PHP does not require SSL encryption".
https://developer.paypal.com/docs/classic/api/apiCredentials/#encrypting-your-certificate
Is the statement of this phrase, that i don't have to create a p12 certificate when working with php, but use the public_key.pem and paypal_public_key.pem?
If yes:
Is it secure enough to create the encrypted form input elements without p12 certificate?
If no:
What do they mean? :-)
Before this question came up, i've tested this little programm.
http://www.softarea51.com/blog/how-to-integrate-your-custom-shopping-cart-with-paypal-website-payments-standard-using-php/
There is a config file paypal-wps-config.inc.php where i can define the paths to my certificates.
// tryed to use // 'paypal_cert.p12 ';
$config['private_key_path'] = '/home/folder/.cert/pp/prvkey.pem';
// must match the one you set when you created the private key
$config['private_key_password'] = ''; //'my_password';
When i try to use the p12 certificate, openssl_error_string() returns "Could not sign data: error:0906D06C:PEM routines:PEM_read_bio:no start line openssl_pkcs7_sign
When i instead use the prvkey.pem without password all works fine.
Here is the function, which signs and encrypt the data.
function signAndEncrypt($dataStr_, $ewpCertPath_, $ewpPrivateKeyPath_, $ewpPrivateKeyPwd_, $paypalCertPath_)
{
$dataStrFile = realpath(tempnam('/tmp', 'pp_'));
$fd = fopen($dataStrFile, 'w');
if(!$fd) {
$error = "Could not open temporary file $dataStrFile.";
return array("status" => false, "error_msg" => $error, "error_no" => 0);
}
fwrite($fd, $dataStr_);
fclose($fd);
$signedDataFile = realpath(tempnam('/tmp', 'pp_'));
**// here the error came from**
if(!#openssl_pkcs7_sign( $dataStrFile,
$signedDataFile,
"file://$ewpCertPath_",
array("file://$ewpPrivateKeyPath_", $ewpPrivateKeyPwd_),
array(),
PKCS7_BINARY)) {
unlink($dataStrFile);
unlink($signedDataFile);
$error = "Could not sign data: ".openssl_error_string();
return array("status" => false, "error_msg" => $error, "error_no" => 0);
}
unlink($dataStrFile);
$signedData = file_get_contents($signedDataFile);
$signedDataArray = explode("\n\n", $signedData);
$signedData = $signedDataArray[1];
$signedData = base64_decode($signedData);
unlink($signedDataFile);
$decodedSignedDataFile = realpath(tempnam('/tmp', 'pp_'));
$fd = fopen($decodedSignedDataFile, 'w');
if(!$fd) {
$error = "Could not open temporary file $decodedSignedDataFile.";
return array("status" => false, "error_msg" => $error, "error_no" => 0);
}
fwrite($fd, $signedData);
fclose($fd);
$encryptedDataFile = realpath(tempnam('/tmp', 'pp_'));
if(!#openssl_pkcs7_encrypt( $decodedSignedDataFile,
$encryptedDataFile,
file_get_contents($paypalCertPath_),
array(),
PKCS7_BINARY)) {
unlink($decodedSignedDataFile);
unlink($encryptedDataFile);
$error = "Could not encrypt data: ".openssl_error_string();
return array("status" => false, "error_msg" => $error, "error_no" => 0);
}
unlink($decodedSignedDataFile);
$encryptedData = file_get_contents($encryptedDataFile);
if(!$encryptedData) {
$error = "Encryption and signature of data failed.";
return array("status" => false, "error_msg" => $error, "error_no" => 0);
}
unlink($encryptedDataFile);
$encryptedDataArray = explode("\n\n", $encryptedData);
$encryptedData = trim(str_replace("\n", '', $encryptedDataArray[1]));
return array("status" => true, "encryptedData" => $encryptedData);
} // signAndEncrypt
} // PPCrypto
The main questions:
Is it possible to use p12 cert with php, or is it secure enough to work without it?
Why i become an error when using openssl_pkcs7_sign
Please help.
Greetings
ninchen

Answer 1

You should not confuse 'using SSL' with 'using SSL with a predefined client certificate'. The document you link to describes the latter. Simply calling an https URL will enable SSL and deliver browser-equivalent security. This is done by the SDK automatically.
Predefined client certificates guard against a sophisticated attacker performing a man-in-the-middle attack. Both methods will stop an unsophisticated attacker from reading your network traffic directly.
Client certificates also serve to authenticate you to PayPal, as an alternate for user/password/signature.