How to get the same output SMIME signing using PHP openssl commands (DER Format?)

Question

I've been trying to duplicate this command using PHP's built in openssl functions with no luck. I've tried variations of openssl_pkcs7_sign and openssl_pkcs7_encrypt. I believe the issue is that there is no flag to indicate the DER format output.

Here is the openssl command I am trying to replicate:

openssl smime -sign -signer mycert.pem -certfile mybundle.crt -inkey mykey.pem -nodetach -outform der -in file_in -out file_out

Answer 1

openssl_pkcs7_sign indeed signs the data in PEM format but you can just take the base64 chunk of the PEM data and convert it to DER by using base64_decode().

function get_base64($file_name) {
   $content = file($file_name, FILE_IGNORE_NEW_LINES);
   $base64_data = "";
   for ($i=5; $i<sizeof($content); $i++){ // take only the base64 chunk
        $base64_data .=  $content[$i];
   }
   return $base64_data;
}

function pem2der($base64_data) {
   $der = base64_decode($base64_data);
   return $der;
}

if (openssl_pkcs7_sign(           // Signs file_in and saves as file_out in PEM format
    "file_in",                    // Input file
    "file_out",                   // Output file (PEM format)
    "file://../.pki/company.crt", // Certificate (mycert.pem)
    "file://../.pki/company.key", // Private key (mykey.pem)
    array(),
    PKCS7_NOATTR,
    "../.pki/company.cacrt"       // Intermediate certificate (mybundle.crt)
    )) {
    $data = pem2der(get_base64("file_out"));  // converts content of file_out to DER format
    $out = fopen("file_out", "w") or die("Unable to open file!");
    fwrite($out,$data);           // output file (DER format)
    fclose($out);
    echo("File signed successfully!")
}
?>