通过shell_exec将二进制数据发送到php-cgi

Question

I have a script that sends a post request to /usr/bin/php-cgi. The script is working fine when dealing with plain text, but fails when the data is binary:

$data = file_get_contents('example.jpg');
$size = filesize('example.jpg') + 5; 
$post_data = 'file='.$data;
$response = shell_exec('echo "'.$post_data.'" | 
                        REDIRECT_STATUS=CGI
                        REQUEST_METHOD=POST
                        SCRIPT_FILENAME=/example/script.php 
                        SCRIPT_NAME=/script.php 
                        PATH_INFO=/ 
                        SERVER_NAME=localhost 
                        SERVER_PROTOCOL=HTTP/1.1 
                        REQUEST_URI=/example/index.html 
                        HTTP_HOST=example.com 
                        CONTENT_TYPE=application/x-www-form-urlencoded
                        CONTENT_LENGTH='.$size.' php-cgi');

I get the following error:

sh: -c: line 1: unexpected EOF while looking for matching `"'
sh: -c: line 5: syntax error: unexpected end of file

I guess this is because the data I'm trying to send is binary and must be encoded/escaped somehow.

Like I said the above code works if the data is plain text:

$post_data = "data=sample data to php-cgi";
$size = strlen($post_data);

I also tried to encode the data using base64_encode() but then I face another problem; the data must be decoded from within the receiving script. I was thinking that perhaps I could encode the data in base64 and then add some content or mime type header to force the php-cgi binary to make the conversation?

One other problem is that I like to send the data as an attachment and therefore I think we must set CONTENT_TYPE to multipart/form-data; boundary=<random_boundary> and CONTENT_DISPOSITION to form-data, but I'm not sure how to set these headers from the commandline.

Answer 1

Finally I got this working, the solution was to send a base64 encoded request which also contained a constant named field like ORIGINAL_QUERY_URI to a sort of gateway file that in turn would decode the request and bounce it to it's original destination.

Basically, the server does this:

1. encode any received file data in base64
2. add a form-data field named ORIGINAL_REQEUST_URI with the original url as value
3. assemble a valid http request body encoded as multipart/form-data based on above
4. send this data using shell_exec to a gateway file that will decode the content

Here is the command I used to send everything to php-cgi:

shell_exec('echo "' . $body . '" | 
            HOST=localhost 
            REDIRECT_STATUS=200 
            REQUEST_METHOD=POST 
            SCRIPT_FILENAME=/<path>/gate.php 
            SCRIPT_NAME=/gate.php 
            PATH_INFO=/ 
            SERVER_NAME=localhost 
            SERVER_PROTOCOL=HTTP/1.1 
            REQUEST_URI=/example.php 
            HTTP_HOST=localhost
            CONTENT_TYPE="multipart/form-data; boundary=' . $boundary . '"  
            CONTENT_LENGTH=' . $size . ' php-cgi');

Then inside the gate.php file I decoded the data and included the file pointed to by theORIGINAL_REQUEST_URI field.

// File: gate.php
if (isset($_FILES)) {
  foreach ($_FILES as $key => $value) {
     // decode the `base64` encoded file data
     $content = file_get_contents($_FILES[$key]['tmp_name']);
     $content = base64_decode($content);
     file_put_contents($_FILES[$key]['tmp_name'], $content);
  }
}
// bounce to original destination
include_once($_POST['ORIGINAL_REQUEST_URI']);