move login block functionality into its own rpc module
ansuz
5 years ago
parent
c765362744
commit
bb7e8e4512
@ -0,0 +1,172 @@
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/*jshint esversion: 6 */
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/* globals Buffer*/
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var Block = module.exports;
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const Fs = require("fs");
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const Fse = require("fs-extra");
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const Path = require("path");
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const Nacl = require("tweetnacl/nacl-fast");
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const nThen = require("nthen");
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const Util = require("../common-util");
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/*
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We assume that the server is secured against MitM attacks
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via HTTPS, and that malicious actors do not have code execution
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capabilities. If they do, we have much more serious problems.
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The capability to replay a block write or remove results in either
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a denial of service for the user whose block was removed, or in the
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case of a write, a rollback to an earlier password.
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Since block modification is destructive, this can result in loss
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of access to the user's drive.
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So long as the detached signature is never observed by a malicious
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party, and the server discards it after proof of knowledge, replays
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are not possible. However, this precludes verification of the signature
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at a later time.
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Despite this, an integrity check is still possible by the original
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author of the block, since we assume that the block will have been
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encrypted with xsalsa20-poly1305 which is authenticated.
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*/
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Block.validateLoginBlock = function (Env, publicKey, signature, block, cb) { // FIXME BLOCKS
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// convert the public key to a Uint8Array and validate it
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if (typeof(publicKey) !== 'string') { return void cb('E_INVALID_KEY'); }
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var u8_public_key;
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try {
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u8_public_key = Nacl.util.decodeBase64(publicKey);
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} catch (e) {
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return void cb('E_INVALID_KEY');
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}
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var u8_signature;
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try {
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u8_signature = Nacl.util.decodeBase64(signature);
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} catch (e) {
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Env.Log.error('INVALID_BLOCK_SIGNATURE', e);
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return void cb('E_INVALID_SIGNATURE');
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}
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// convert the block to a Uint8Array
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var u8_block;
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try {
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u8_block = Nacl.util.decodeBase64(block);
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} catch (e) {
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return void cb('E_INVALID_BLOCK');
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}
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// take its hash
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var hash = Nacl.hash(u8_block);
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// validate the signature against the hash of the content
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var verified = Nacl.sign.detached.verify(hash, u8_signature, u8_public_key);
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// existing authentication ensures that users cannot replay old blocks
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// call back with (err) if unsuccessful
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if (!verified) { return void cb("E_COULD_NOT_VERIFY"); }
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return void cb(null, u8_block);
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};
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var createLoginBlockPath = function (Env, publicKey) { // FIXME BLOCKS
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// prepare publicKey to be used as a file name
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var safeKey = Util.escapeKeyCharacters(publicKey);
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// validate safeKey
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if (typeof(safeKey) !== 'string') {
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return;
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}
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// derive the full path
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// /home/cryptpad/cryptpad/block/fg/fg32kefksjdgjkewrjksdfksjdfsdfskdjfsfd
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return Path.join(Env.paths.block, safeKey.slice(0, 2), safeKey);
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};
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Block.writeLoginBlock = function (Env, msg, cb) { // FIXME BLOCKS
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//console.log(msg);
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var publicKey = msg[0];
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var signature = msg[1];
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var block = msg[2];
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Block.validateLoginBlock(Env, publicKey, signature, block, function (e, validatedBlock) {
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if (e) { return void cb(e); }
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if (!(validatedBlock instanceof Uint8Array)) { return void cb('E_INVALID_BLOCK'); }
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// derive the filepath
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var path = createLoginBlockPath(Env, publicKey);
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// make sure the path is valid
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if (typeof(path) !== 'string') {
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return void cb('E_INVALID_BLOCK_PATH');
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}
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var parsed = Path.parse(path);
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if (!parsed || typeof(parsed.dir) !== 'string') {
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return void cb("E_INVALID_BLOCK_PATH_2");
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}
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nThen(function (w) {
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// make sure the path to the file exists
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Fse.mkdirp(parsed.dir, w(function (e) {
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if (e) {
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w.abort();
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cb(e);
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}
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}));
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}).nThen(function () {
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// actually write the block
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// flow is dumb and I need to guard against this which will never happen
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/*:: if (typeof(validatedBlock) === 'undefined') { throw new Error('should never happen'); } */
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/*:: if (typeof(path) === 'undefined') { throw new Error('should never happen'); } */
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Fs.writeFile(path, Buffer.from(validatedBlock), { encoding: "binary", }, function (err) {
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if (err) { return void cb(err); }
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cb();
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});
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});
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});
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};
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/*
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When users write a block, they upload the block, and provide
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a signature proving that they deserve to be able to write to
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the location determined by the public key.
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When removing a block, there is nothing to upload, but we need
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to sign something. Since the signature is considered sensitive
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information, we can just sign some constant and use that as proof.
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*/
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Block.removeLoginBlock = function (Env, msg, cb) { // FIXME BLOCKS
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var publicKey = msg[0];
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var signature = msg[1];
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var block = Nacl.util.decodeUTF8('DELETE_BLOCK'); // clients and the server will have to agree on this constant
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Block.validateLoginBlock(Env, publicKey, signature, block, function (e /*::, validatedBlock */) {
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if (e) { return void cb(e); }
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// derive the filepath
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var path = createLoginBlockPath(Env, publicKey);
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// make sure the path is valid
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if (typeof(path) !== 'string') {
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return void cb('E_INVALID_BLOCK_PATH');
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}
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// FIXME COLDSTORAGE
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Fs.unlink(path, function (err) {
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Env.Log.info('DELETION_BLOCK_BY_OWNER_RPC', {
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publicKey: publicKey,
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path: path,
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status: err? String(err): 'SUCCESS',
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});
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if (err) { return void cb(err); }
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cb();
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});
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});
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};
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