<?php
include("config.php");
include_once("ppcl.php");

function send_message($type, $message) {
    header("Content-type: application/pprf");
    echo("PPRF\x00");
    $len = strlen($message) + 1;
    echo(pack("PC", $len, $type));
    echo($message);
    exit();
}

function send_failure($code, $message) {
    $len = strlen($message);
    $msg = pack("vv", $code, $len);
    $msg .= $message;
    send_message(193, $msg);
}

function send_confirmation() {
    send_message(192, "");
}

function get_ppcl() {
    $ppcl = new Ppcl();
    $ppcl->from_string(file_get_contents(PUBLICATION_DIR . "/collection.ppcl"));
    return $ppcl;
}

function get_member($ppcl, $name) {
    foreach($ppcl->members as $m) {
        if($m->name == $name) {
            return $m;
        }
    }
    send_failure(3, "No member \"" . $member_name . "\" in collection");
}

function verify_collection_message($handle, $ppcl) {
    $id = fread($handle, SODIUM_CRYPTO_SIGN_PUBLICKEYBYTES);
    if($ppcl->identifier != $id) {
        send_failure(2, "Provided collection not hosted by this server");
    }
}

function read_upload_session_message($handle) {
    $data = array();
    $tsize = unpack("v", fread($handle, 2))[1];
    $data["token"] = fread($handle, $tsize);

    $asize = unpack("v", fread($handle, 2))[1];
    $data["auth"] = fread($handle, $asize);
    return $data;
}

function get_upload_session($session_header) {
    $file = fopen(PPRF_DATA_DIR . "/upload-session-info-" . bin2hex($session_header["token"]), 'rb');
    if($file == null) {
        send_failure(4, "Invalid upload session token");
    }
    $session = array();
    $session["file_size"] = unpack("P", fread($file, 8))[1];
    $session["key"] = fread($file, SODIUM_CRYPTO_BOX_KEYPAIRBYTES);
    $name_size = unpack("C", fread($file, 1))[1];
    $session["member_name"] = fread($file, $name_size);
    return $session;
}

function verify_upload_auth($session_header, $session, $member, $checksum) {
    $decrypted = sodium_crypto_box_seal_open($session_header["auth"], $session["key"]);
    if($decrypted == null) {
        send_failure(5, "Could not decrypt upload chunk auth");
    }
    $verified = sodium_crypto_sign_open($decrypted, $member->signing_public_key);
    if($verified == null) {
        send_failure(5, "Could not verify upload chunk auth");
    }

    if($verified != $checksum) {
        send_failure(5, "Invalid checksum on upload chunk auth");
    }
}

function cleanup_upload_session($token) {
    unlink(PPRF_DATA_DIR . "/upload-session-info-" . bin2hex($token));
    unlink(PPRF_DATA_DIR . "/upload-session-file-" . bin2hex($token));
}


if(!ENABLE_PPRF) {
    send_failure(1, "PPRF has been disabled on this server");
}

$handle = fopen("php://input", "rb");
if(fread($handle, 5) != "PPRF\x00") {
    send_failure(0, "Stream did not begin with PPRF magic number.");
}

$message_info = unpack("Psize/Ctype", fread($handle, 9));

// Register name
if($message_info["type"] == 32) {
    $ppcl = get_ppcl();
    verify_collection_message($handle, $ppcl);
    $member_name_size = unpack("C", fread($handle, 1))[1];
    $member_name = fread($handle, $member_name_size);
    $member = get_member($ppcl, $member_name);

    $signed_name_size = unpack("v", fread($handle, 2))[1];
    $signed_name = fread($handle, $signed_name_size);

    $name = sodium_crypto_sign_open($signed_name, $member->signing_public_key);
    if($name == null) {
        send_failure(11, "Could not verify signed name");
    }

    if(strtolower(substr($name, strlen($name)-5, 5)) != ".ppub") {
        send_failure(7, "Name must end in \".ppub\"");
    }

    $path = PUBLICATION_DIR . "/" . $name;
    if(file_exists($path)) {
        send_failure(8, "Name already exists");
    }

    file_put_contents($path, "");
    send_confirmation();
}

// Begin upload
if($message_info["type"] == 33) {
    $ppcl = get_ppcl();
    verify_collection_message($handle, $ppcl);
    $details = unpack("Pfile_size/Cname_size", fread($handle, 9));
    $member_name = fread($handle, $details["name_size"]);
    $member = get_member($ppcl, $member_name);

    // Create upload session
    $token = random_bytes(16);
    $key = sodium_crypto_box_keypair();

    $session_data = pack("P", $details["file_size"]);
    $session_data .= $key;
    $session_data .= pack("C", $details["name_size"]);
    $session_data .= $member_name;
    file_put_contents(PPRF_DATA_DIR . "/upload-session-info-" . bin2hex($token), $session_data);
    file_put_contents(PPRF_DATA_DIR . "/upload-session-file-" . bin2hex($token), "");

    $session_auth = sodium_crypto_box_publickey($key);
    $session_auth .= $token;
    
    // Build and send reply
    $challenge = sodium_crypto_box_seal($session_auth, $member->sealing_public_key);
    $reply = pack("v", strlen($challenge));
    $reply .= $challenge;
    $reply .= pack("V", PPRF_MAX_UPLOAD_CHUNK_SIZE);
    send_message(160, $reply);
}

// Upload message
if($message_info["type"] == 35) {
    $ppcl = get_ppcl();
    verify_collection_message($handle, $ppcl);
    $session_header = read_upload_session_message($handle);
    $session = get_upload_session($session_header);
    $path = PPRF_DATA_DIR . "/upload-session-file-" . bin2hex($session_header["token"]);
    $offset = unpack("P", fread($handle, 8))[1];

    $member = get_member($ppcl, $session["member_name"]);

    if($offset != filesize($path)) {
        send_failure(6, "Invalid offset, got " . $offset . " expected " . filesize($path));
    }

    $data_size = $message_info["size"] - 9; // Message size minus headers
    $data = fread($handle, $data_size);

    // Verify data
    $checksum = hash("sha512", $data, true);
    verify_upload_auth($session_header, $session, $member, $checksum);

    file_put_contents($path, $data, FILE_APPEND);
    send_confirmation();
}

// Finalise upload message
if($message_info["type"] == 34) {
    $ppcl = get_ppcl();
    verify_collection_message($handle, $ppcl);
    $session_header = read_upload_session_message($handle);
    $session = get_upload_session($session_header);
    $upload_path = PPRF_DATA_DIR . "/upload-session-file-" . bin2hex($session_header["token"]);
    $member = get_member($ppcl, $session["member_name"]);
    
    $flags = unpack('C', fread($handle, 1))[1];
    $dest_len = unpack('v', fread($handle, 2))[1];
    $dest_name = fread($handle, $dest_len);
    $dest_path = PUBLICATION_DIR . "/" . $dest_name;
    $bsdiff_old_checksum = null;

    // If cancel flag set
    if(($flags & 1 << 0) != 0) {    
        cleanup_upload_session($session_header["token"]);
        send_confirmation();
    }

    // If BSDIFF flag set
    if(($flags & 1 << 2) != 0) {
        $bsdiff_old_checksum = fread($handle, 64);
    }

    if(!file_exists($dest_path)) {
        cleanup_upload_session($session_header["token"]);
        send_failure(9, "The name \"" . $dest_name . "\" is not registered");
    }

    // If overwrite flag NOT set, and file is not empty
    if(($flags & 1 << 1) == 0 && filesize($dest_path) != 0) {
        cleanup_upload_session($session_header["token"]);
        send_failure(10, "The destination \"" . $dest_name . "\" is not empty");
    }

    // Verify data
    $checksum = hash_file("sha512", $upload_path, true);
    verify_upload_auth($session_header, $session, $member, $checksum);

    // Copy to destination
    if($bsdiff_old_checksum == null) {
        rename($upload_path, $dest_path);
    }
    else if(!ENABLE_PPRF_BSPATCH) {
        send_failure(1, "BSPATCH is not supported by this server");
    }
    else {
        $old_hash = hash_file("sha512", $dest_path, true);
        if($bsdiff_old_checksum != $old_hash) {
            cleanup_upload_session($session_header["token"]);
            send_failure(12, "Destination file does not match provided checksum");
        }
        $patched_path = PPRF_DATA_DIR . "/upload-session-patch-" . bin2hex($session_header["token"]);
        $output=null;
        $retval=null;
        exec(BSPATCH_PATH . " " . escapeshellarg($dest_path) . " " . escapeshellarg($patched_path) . " " . escapeshellarg($upload_path), $output, $retval);
        if($retval != 0) {
            cleanup_upload_session($session_header["token"]);
            send_failure(13, "bspatch failed with exit code " . $retval);
        }

        rename($patched_path, $dest_path);
    }

    cleanup_upload_session($session_header["token"]);
    send_confirmation();
}


send_failure(1, "Messages of type " . $message_info["type"] . " are not supported by this server");

?>