cryptpad/lib/commands/block.js

173 lines
5.7 KiB
JavaScript

/*jshint esversion: 6 */
/* globals Buffer*/
var Block = module.exports;
const Fs = require("fs");
const Fse = require("fs-extra");
const Path = require("path");
const Nacl = require("tweetnacl/nacl-fast");
const nThen = require("nthen");
const Util = require("../common-util");
/*
We assume that the server is secured against MitM attacks
via HTTPS, and that malicious actors do not have code execution
capabilities. If they do, we have much more serious problems.
The capability to replay a block write or remove results in either
a denial of service for the user whose block was removed, or in the
case of a write, a rollback to an earlier password.
Since block modification is destructive, this can result in loss
of access to the user's drive.
So long as the detached signature is never observed by a malicious
party, and the server discards it after proof of knowledge, replays
are not possible. However, this precludes verification of the signature
at a later time.
Despite this, an integrity check is still possible by the original
author of the block, since we assume that the block will have been
encrypted with xsalsa20-poly1305 which is authenticated.
*/
var validateLoginBlock = function (Env, publicKey, signature, block, cb) { // FIXME BLOCKS
// convert the public key to a Uint8Array and validate it
if (typeof(publicKey) !== 'string') { return void cb('E_INVALID_KEY'); }
var u8_public_key;
try {
u8_public_key = Nacl.util.decodeBase64(publicKey);
} catch (e) {
return void cb('E_INVALID_KEY');
}
var u8_signature;
try {
u8_signature = Nacl.util.decodeBase64(signature);
} catch (e) {
Env.Log.error('INVALID_BLOCK_SIGNATURE', e);
return void cb('E_INVALID_SIGNATURE');
}
// convert the block to a Uint8Array
var u8_block;
try {
u8_block = Nacl.util.decodeBase64(block);
} catch (e) {
return void cb('E_INVALID_BLOCK');
}
// take its hash
var hash = Nacl.hash(u8_block);
// validate the signature against the hash of the content
var verified = Nacl.sign.detached.verify(hash, u8_signature, u8_public_key);
// existing authentication ensures that users cannot replay old blocks
// call back with (err) if unsuccessful
if (!verified) { return void cb("E_COULD_NOT_VERIFY"); }
return void cb(null, u8_block);
};
var createLoginBlockPath = function (Env, publicKey) { // FIXME BLOCKS
// prepare publicKey to be used as a file name
var safeKey = Util.escapeKeyCharacters(publicKey);
// validate safeKey
if (typeof(safeKey) !== 'string') {
return;
}
// derive the full path
// /home/cryptpad/cryptpad/block/fg/fg32kefksjdgjkewrjksdfksjdfsdfskdjfsfd
return Path.join(Env.paths.block, safeKey.slice(0, 2), safeKey);
};
Block.writeLoginBlock = function (Env, safeKey, msg, cb) { // FIXME BLOCKS
//console.log(msg);
var publicKey = msg[0];
var signature = msg[1];
var block = msg[2];
validateLoginBlock(Env, publicKey, signature, block, function (e, validatedBlock) {
if (e) { return void cb(e); }
if (!(validatedBlock instanceof Uint8Array)) { return void cb('E_INVALID_BLOCK'); }
// derive the filepath
var path = createLoginBlockPath(Env, publicKey);
// make sure the path is valid
if (typeof(path) !== 'string') {
return void cb('E_INVALID_BLOCK_PATH');
}
var parsed = Path.parse(path);
if (!parsed || typeof(parsed.dir) !== 'string') {
return void cb("E_INVALID_BLOCK_PATH_2");
}
nThen(function (w) {
// make sure the path to the file exists
Fse.mkdirp(parsed.dir, w(function (e) {
if (e) {
w.abort();
cb(e);
}
}));
}).nThen(function () {
// actually write the block
// flow is dumb and I need to guard against this which will never happen
/*:: if (typeof(validatedBlock) === 'undefined') { throw new Error('should never happen'); } */
/*:: if (typeof(path) === 'undefined') { throw new Error('should never happen'); } */
Fs.writeFile(path, Buffer.from(validatedBlock), { encoding: "binary", }, function (err) {
if (err) { return void cb(err); }
cb();
});
});
});
};
/*
When users write a block, they upload the block, and provide
a signature proving that they deserve to be able to write to
the location determined by the public key.
When removing a block, there is nothing to upload, but we need
to sign something. Since the signature is considered sensitive
information, we can just sign some constant and use that as proof.
*/
Block.removeLoginBlock = function (Env, safeKey, msg, cb) { // FIXME BLOCKS
var publicKey = msg[0];
var signature = msg[1];
var block = Nacl.util.decodeUTF8('DELETE_BLOCK'); // clients and the server will have to agree on this constant
validateLoginBlock(Env, publicKey, signature, block, function (e /*::, validatedBlock */) {
if (e) { return void cb(e); }
// derive the filepath
var path = createLoginBlockPath(Env, publicKey);
// make sure the path is valid
if (typeof(path) !== 'string') {
return void cb('E_INVALID_BLOCK_PATH');
}
// FIXME COLDSTORAGE
Fs.unlink(path, function (err) {
Env.Log.info('DELETION_BLOCK_BY_OWNER_RPC', {
publicKey: publicKey,
path: path,
status: err? String(err): 'SUCCESS',
});
if (err) { return void cb(err); }
cb();
});
});
};