Listo, ya lo logre!
Código PHP:
<?php
$c = curl_init('http://direccion/login.php);
$body = 'user=user&pass=pass';
curl_setopt($c, CURLOPT_HEADER, 1);
curl_setopt($c, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($c, CURLOPT_COOKIEJAR, '/tmp/cookies.txt');
curl_setopt($c, CURLOPT_COOKIEFILE, '/tmp/cookies.txt);
curl_setopt($c, CURLOPT_POST, true);
curl_setopt($c, CURLOPT_POSTFIELDS, $body);
$page = curl_exec($c);
curl_close($c);
echo $page;
?>
:D