source code from DEF CON Quals 2018 - Easy Pisy challenge
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<?php | |
include 'common.php'; | |
if ($_SERVER['REQUEST_METHOD'] === 'GET') { | |
print highlight_string(file_get_contents("execute.php"), TRUE); | |
exit(0); | |
} | |
$keys = get_keys(); | |
$privkey = $keys[0]; | |
$pubkey = $keys[1]; | |
$file_info = $_FILES['userfile']; | |
check_uploaded_file($file_info); | |
$data = file_get_contents($file_info['tmp_name']); | |
$signature = hex2bin($_POST['signature']); | |
if (openssl_verify($data, $signature, $pubkey)) { | |
print 'Signature is OK.<br/>'; | |
} else { | |
die('Bad signature.'); | |
} | |
$text = pdf_to_text($file_info['tmp_name']); | |
print "Text: \"$text\"<br/>"; | |
$execute_query = "EXECUTE "; | |
$echo_query = "ECHO "; | |
if (substr($text, 0, strlen($execute_query)) === $execute_query) { | |
$payload = substr($text, strlen($execute_query)); | |
print "About to execute: \"$payload\".<br/>"; | |
$out = shell_exec($payload); | |
print "Output: $out"; | |
} else if (substr($text, 0, strlen($echo_query)) === $echo_query) { | |
$payload = substr($text, strlen($echo_query)); | |
print "About to echo: \"$payload\".<br/>"; | |
echo $payload; | |
} else { | |
print "I can't recognize the command type. Go away.<br/>"; | |
} | |
?> |
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<?php | |
include 'common.php'; | |
if ($_SERVER['REQUEST_METHOD'] === 'GET') { | |
print highlight_string(file_get_contents("sign.php"), TRUE); | |
exit(0); | |
} | |
$keys = get_keys(); | |
$privkey = $keys[0]; | |
$pubkey = $keys[1]; | |
if ($privkey === FALSE || $pubkey === FALSE) { | |
die("Could not load keys. Contact admin.<br/>"); | |
} | |
$file_info = $_FILES['userfile']; | |
check_uploaded_file($file_info); | |
$text = pdf_to_text($file_info['tmp_name']); | |
print "Extracted text: \"$text\"<br/>"; | |
$execute_query = "EXECUTE "; | |
$echo_query = "ECHO "; | |
if (substr($text, 0, strlen($execute_query)) === $execute_query) { | |
print "I don't sign EXECUTE commands. Go away.<br/>"; | |
} else if (substr($text, 0, strlen($echo_query)) === $echo_query) { | |
print "I'm OK with ECHO commands. Here is the signature: <br/>"; | |
$data = file_get_contents($file_info['tmp_name']); | |
openssl_sign($data, $signature, $privkey); | |
print bin2hex($signature); | |
} else { | |
print "I can't recognize the command type. Go away.<br/>"; | |
} | |
?> |
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