Sending Encrypted Email S/MIME with PHP - php

Question

I have been looking a lot online but I didn't find an answer, is it possible to send encrypted emails S/MIME using PHP? if it is, how? (im using cakephp 2.x)
Thank you very much in advance

Answer 1

I managed to find a solution to this using PHPMailer, It applies to regular PHP as well. It will sign and encrypt the email, I couldn't find a way to do both with PHPMailer (sign and encrypt) only sign so I added some code to class.phpmailer.php. It stills need to add some error handling in case of an encryption error but so far works good.
for CakePHP 2.x:
Download PHPMailer and add it to your Vendors folder (project_name/app/vendor)
Add this line at the beginning of your function:
App::import('Vendor','PHPMailer/PHPMailerAutoload');
From here its the same for PHP or CakePHP:
$mail = new PHPMailer();
$mail->setFrom('from_who#email', 'Intranet');
//Set who the message is to be sent to
$mail->addAddress('to_who#email', 'Ricardo V');
//Set the subject line
$mail->Subject = 'PHPMailer signing test';
//Replace the plain text body with one created manually
$mail->Body = "some encrypted text...";
//Attach an image file
$mail->addAttachment('D:/path_to_file/test.pdf');
$mail->sign(
'app/webroot/cert/cert.crt', //The location of your certificate file
'app/webroot/cert/private.key', //The location of your private key
file
'password', //The password you protected your private key with (not
//the Import Password! may be empty but parameter must not be omitted!)
'app/webroot/cert/certchain.pem', //the certificate chain.
'1', //Encrypt the email as well, (1 = encrypt, 0 = dont encrypt)
'app/webroot/cert/rvarilias.crt'//The location of public certificate
//to encrypt the email with.
);
if (!$mail->send()) {
echo "Mailer Error: " . $mail->ErrorInfo;
} else {
echo "Message sent!";
}
Then we need to make some changes to class.phpmailer.php
replace the lines from 2368 to 2390 with:
$sign = #openssl_pkcs7_sign(
$file,
$signed,
'file://' . realpath($this->sign_cert_file),
array('file://' . realpath($this->sign_key_file),
$this->sign_key_pass),
null,
PKCS7_DETACHED,
$this->sign_extracerts_file
);
if ($this->encrypt_file == 1) {
$encrypted = tempnam(sys_get_temp_dir(), 'encrypted');
$encrypt = #openssl_pkcs7_encrypt(
$signed,
$encrypted,
file_get_contents($this->encrypt_cert_file),
null,
0,
1
);
if ($encrypted) {
#unlink($file);
$body = file_get_contents($encrypted);
#unlink($signed);
#unlink($encrypted);
//The message returned by openssl contains both headers
and body, so need to split them up
$parts = explode("\n\n", $body, 2);
$this->MIMEHeader .= $parts[0] . $this->LE . $this->LE;
$body = $parts[1];
} else {
#unlink($file);
#unlink($signed);
#unlink($encrypted);
throw new phpmailerException($this->lang('signing') .
openssl_error_string());
}
} else {
if ($signed) {
#unlink($file);
$body = file_get_contents($signed);
#unlink($signed);
//The message returned by openssl contains both headers
and body, so need to split them up
$parts = explode("\n\n", $body, 2);
$this->MIMEHeader .= $parts[0] . $this->LE . $this->LE;
$body = $parts[1];
} else {
#unlink($file);
#unlink($signed);
throw new phpmailerException($this->lang('signing') .
openssl_error_string());
}
}
}
then look for:
public function sign($cert_filename, $key_filename, $key_pass,
$extracerts_filename = '')
{
$this->sign_cert_file = $cert_filename;
$this->sign_key_file = $key_filename;
$this->sign_key_pass = $key_pass;
$this->sign_extracerts_file = $extracerts_filename;
}
and change it for:
public function sign($cert_filename, $key_filename, $key_pass,
$extracerts_filename = '', $and_encrypt ='0', $encrypt_cert = '')
{
$this->sign_cert_file = $cert_filename;
$this->sign_key_file = $key_filename;
$this->sign_key_pass = $key_pass;
$this->sign_extracerts_file = $extracerts_filename;
$this->encrypt_file = $and_encrypt;
$this->encrypt_cert_file = $encrypt_cert;
}
look for:
protected $sign_extracerts_file = '';
and add these lines after it:
protected $encrypt_cert = '';
protected $and_encrypt = '';
With these changes to phpmailer you can send a signed email or a signed and encrypted email. It works with attachments too.
I hope it is help ful to somebody.
*for regular php just don't add the line:
App::import('Vendor','PHPMailer/PHPMailerAutoload');