openssl_pkcs7_sign

Sign an S/MIME message (PHP 4 >= 4.0.6, PHP 5)
bool openssl_pkcs7_sign ( string infilename, string outfilename, mixed signcert, mixed privkey, array headers [, int flags [, string extracerts]] )

openssl_pkcs7_sign() takes the contents of the file named infilename and signs them using the certificate and its matching private key specified by signcert and privkey parameters.

Parameters

infilename
outfilename
signcert
privkey
headers: headers is an array of headers that will be prepended to the data after it has been signed (see openssl_pkcs7_encrypt() for more information about the format of this parameter.
flags: flags can be used to alter the output - see PKCS7 constants - if not specified, it defaults to PKCS7_DETACHED.
extracerts: extracerts specifies the name of a file containing a bunch of extra certificates to include in the signature which can for example be used to help the recipient to verify the certificate that you used.

Return Values

Returns TRUE on success or FALSE on failure.

Examples

Example 1675. openssl_pkcs7_sign() example

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<?php
// the message you want to sign so that recipient can be sure it was you that

// sent it
$data = <<<EOD


You have my authorization to spend $10,000 on dinner expenses.


The CEO
EOD;
// save message to file
$fp = fopen("msg.txt", "w");
fwrite($fp, $data);
fclose($fp);
// encrypt it
if (openssl_pkcs7_sign("msg.txt", "signed.txt", "mycert.pem",

    array("file://mycert.pem", "mypassphrase"),

    array("To" => "joes@example.com", // keyed syntax

          "From: HQ <ceo@example.com>", // indexed syntax

          "Subject" => "Eyes only")

    )) {

    // message signed - send it!

    exec(ini_get("sendmail_path") . " < signed.txt");

}
?>

Code Examples / Notes » openssl_pkcs7_sign

Working example: <?php $data = <<< EOF Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit You have my authorization to spend 10,000 on dinner expenses. The CEO EOF; $fp = fopen("msg.txt", "w"); fwrite($fp, $data); fclose($fp); $headers = array("From" => "me@email.com"); openssl_pkcs7_sign("msg.txt", "signed.txt", "file://email.pem", array("file://email.pem", "123456"), $headers); $data = file_get_contents("signed.txt"); $parts = explode("\n\n", $data, 2); mail("you@email.com", "Signed message.", $parts[1], $parts[0]); echo "Email sent"; ?>

This command doesn't work correctly on WIN32 with IIS. Mails aren’t interpreted correctly by IIS SMTP Server (and by Outlook too). The reason is that UNIX and WINDOWS interpret the “enter to the next line” ascii code in a different way. Below I present an improved code: <?php $data = <<<EOD Testing 123 This is a test Test EOD; //save the message to a file $fp = fopen("msg.txt","w"); fwrite($fp,$data); fclose($fp); //sign the message using the sender's keys openssl_pkcs7_sign("msg.txt", "signed.eml", "file://c:/max/cert.pem", array("file://c:/max/priv.pem","your_password"), array("To" => "recipient <recipients@mail.com>", "From" => "sender <sender@mail.com>", "Subject" => "Order Notification - Test"),PKCS7_DETACHED,"c:\max\extra_cert.pem"); $file_arry = file("signed.eml"); $file = join ("", $file_arry); $message = preg_replace("/\r\n|\r|\n/", "\r\n", $file); $fp = fopen("c:\Inetpub\mailroot\Pickup\signed.eml", "wb"); flock($fp, 2); fputs($fp, $message); flock($fp, 3); fclose($fp); ?> Besides, if you want to use the keys created with Windows, you should export them (from IE) to the form of PKCS#12 file (*.pfx). Install OpenSSLWin32 from http://www.shininglightpro.com/search.php?searchname=Win32+OpenSSL execute: openssl.exe enter the commands: pkcs12 -in <pfx-file> -nokeys -out <pem-certs-file> pkcs12 -in <pfx-file> -nocerts -nodes -out <pem-key-file> Next export from IE Root CA certificate as Base-64 *.cer and rename the file to *.pem And that's all!

It is also possible to sign message including attachments. An easy way to do this: <? $boundary = md5(uniqid(time())); $boddy = "MIME-Version: 1.0\n"; $boddy .= "Content-Type: multipart/mixed; boundary=\"" . $boundary. "\"\n"; $boddy .= "Content-Transfer-Encoding: quoted-printable\n\n"; $boddy .= "This is a multi-part message in MIME format.\n\n"; $boddy .= "--$boundary\n"; $boddy .= "Content-Type: text/plain; charset=\"iso-8859-1\"\n"; $boddy .= "Content-Transfer-Encoding: quoted-printable\n\n"; $boddy .= $EmailText . "\n\n"; // Add the attachment to the message do { $boddy .= "--$boundary\n"; $boddy .= "Content-Type: application/pdf; name=\"FileName\"\n"; $boddy .= "Content-Transfer-Encoding: base64\n"; $boddy .= "Content-Disposition: attachment;\n\n"; $boddy .= chunk_split(base64_encode($file)) . "\n\n"; } while ( {files left to be attached} ); $boddy .= "--$boundary--\n"; // Save message to a file $msg = 'msg.txt'; $signed = 'signed.txt'; $fp = fopen($msg, "w"); fwrite($fp, $boddy); fclose($fp); // Sign it if (openssl_pkcs7_sign($msg, $signed, 'file://cert.pem', array('file://key.pem', 'test'), array("To" => "joes@example.com", // keyed syntax "From: HQ <ceo@example.com>", // indexed syntax "Subject" => "Eyes only"), PKCS7_DETACHED, 'intermediate_cert.pem' )) { exec(ini_get('sendmail_path') . ' < ' . $signed); } ?> The same can be established by using the PEAR package Mail_Mime in combination with openssl_pkcs7_sign.

I would like to make a modification from my previous note. Some clients prefer a certain order in which messages should be signed and encrypted (if both is desired). Newer email clients, such as Thunderbird and Outlook 2003 will accept the most secure method of "sign -> encrypt -> sign again". Why? The first signing authenticates the message saying that you did indeed write it. Then the email is encrypted so that only the recipient can open and read it. Then the second signing ensure confidentiality by identifying that the person encrypting is the one whom encrypted it, a message intended for the decrypting person. This is the most secure method. This ensures: Non-Repudiation of message (first sign), Confidentiality (encrypt), and Context Integrity [you were intended to be addressed] (second sign). If you only sign then encrypt, there is no way you can guarantee that (aside from the contents of the letter, headers are placed in plain text outside the message) that the message was intended for you by the original sender. For example: Bob signs a love letter and encrypts it to Amy saying only "I love you. -- Bob". Amy decrypts it, sees the message (and plays a joke) and forwards the message to John using John's public key, re-encrypting, but not tampering with the message contents keeping the signature valid. This allows Amy to make it look like Bob sent John a love letter and that Bob loves John, as you cannot verify whom sent it during encryption. That is not what you want! This is also analogous to someone taking a government document, put it in an envelope themselves and write the government address in the return address and send it to you. You know the letter is written by the government, but you don't know for sure whether the government sent it to you directly or was opened and relayed. While encrypting then signing has a problem, this is affectively signing on the envelope of a snail mail piece. I know you sent it, but is the message really from you? Or are you forwarding it? Sign - Encrypt - Sign Again method will make the first sign show that you know the writer of the message is the person, encrypt it to keep others from reading it, sign again to indicate the message was not relayed and that the sender intended to sent the mail to address you. Just make sure the headers of the mail is applied in the last step and not the second or third step. For more information about the security and integrity risks of this situation, please read this web page: http://world.std.com/~dtd/sign_encrypt/sign_encrypt7.html

openssl_pkcs7_sign

Sign an S/MIME message (PHP 4 >= 4.0.6, PHP 5) bool openssl_pkcs7_sign ( string infilename, string outfilename, mixed signcert, mixed privkey, array headers [, int flags [, string extracerts]] )

Parameters

Return Values

Examples

Example 1675. openssl_pkcs7_sign() example

Code Examples / Notes » openssl_pkcs7_sign

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Sign an S/MIME message (PHP 4 >= 4.0.6, PHP 5)
bool openssl_pkcs7_sign ( string infilename, string outfilename, mixed signcert, mixed privkey, array headers [, int flags [, string extracerts]] )