cryptpad/www/file/file-crypto.js

210 lines
5.9 KiB
JavaScript

define([
'/bower_components/tweetnacl/nacl-fast.min.js',
], function () {
var Nacl = window.nacl;
//var PARANOIA = true;
var plainChunkLength = 128 * 1024;
var cypherChunkLength = 131088;
var computeEncryptedSize = function (bytes, meta) {
var metasize = Nacl.util.decodeUTF8(JSON.stringify(meta)).length;
var chunks = Math.ceil(bytes / plainChunkLength);
return metasize + 18 + (chunks * 16) + bytes;
};
var encodePrefix = function (p) {
return [
65280, // 255 << 8
255,
].map(function (n, i) {
return (p & n) >> ((1 - i) * 8);
});
};
var decodePrefix = function (A) {
return (A[0] << 8) | A[1];
};
var slice = function (A) {
return Array.prototype.slice.call(A);
};
var createNonce = function () {
return new Uint8Array(new Array(24).fill(0));
};
var increment = function (N) {
var l = N.length;
while (l-- > 1) {
/* our linter suspects this is unsafe because we lack types
but as long as this is only used on nonces, it should be safe */
if (N[l] !== 255) { return void N[l]++; } // jshint ignore:line
if (l === 0) { throw new Error('E_NONCE_TOO_LARGE'); }
N[l] = 0;
}
};
var joinChunks = function (chunks) {
return new Blob(chunks);
};
var decrypt = function (u8, key, done, progress) {
var MAX = u8.length;
var _progress = function (offset) {
if (typeof(progress) !== 'function') { return; }
progress(Math.min(1, offset / MAX));
};
var nonce = createNonce();
var i = 0;
var prefix = u8.subarray(0, 2);
var metadataLength = decodePrefix(prefix);
var res = {
metadata: undefined,
};
var cancelled = false;
var cancel = function () {
cancelled = true;
};
var metaBox = new Uint8Array(u8.subarray(2, 2 + metadataLength));
var metaChunk = Nacl.secretbox.open(metaBox, nonce, key);
increment(nonce);
try {
res.metadata = JSON.parse(Nacl.util.encodeUTF8(metaChunk));
} catch (e) {
return window.setTimeout(function () {
done('E_METADATA_DECRYPTION');
});
}
if (!res.metadata) {
return void setTimeout(function () {
done('NO_METADATA');
});
}
var takeChunk = function (cb) {
setTimeout(function () {
var start = i * cypherChunkLength + 2 + metadataLength;
var end = start + cypherChunkLength;
i++;
var box = new Uint8Array(u8.subarray(start, end));
// decrypt the chunk
var plaintext = Nacl.secretbox.open(box, nonce, key);
increment(nonce);
if (!plaintext) { return cb('DECRYPTION_ERROR'); }
_progress(end);
cb(void 0, plaintext);
});
};
var chunks = [];
var again = function () {
if (cancelled) { return; }
takeChunk(function (e, plaintext) {
if (e) {
return setTimeout(function () {
done(e);
});
}
if (plaintext) {
if ((2 + metadataLength + i * cypherChunkLength) < u8.length) { // not done
chunks.push(plaintext);
return setTimeout(again);
}
chunks.push(plaintext);
res.content = joinChunks(chunks);
return done(void 0, res);
}
done('UNEXPECTED_ENDING');
});
};
again();
return {
cancel: cancel
};
};
// metadata
/* { filename: 'raccoon.jpg', type: 'image/jpeg' } */
var encrypt = function (u8, metadata, key) {
var nonce = createNonce();
// encode metadata
var plaintext = Nacl.util.decodeUTF8(JSON.stringify(metadata));
// if metadata is too large, drop the thumbnail.
if (plaintext.length > 65535) {
var temp = JSON.parse(JSON.stringify(metadata));
delete metadata.thumbnail;
plaintext = Nacl.util.decodeUTF8(JSON.stringify(temp));
}
var i = 0;
var state = 0;
var next = function (cb) {
if (state === 2) { return void setTimeout(cb); }
var start;
var end;
var part;
var box;
if (state === 0) { // metadata...
part = new Uint8Array(plaintext);
box = Nacl.secretbox(part, nonce, key);
increment(nonce);
if (box.length > 65535) {
return void cb('METADATA_TOO_LARGE');
}
var prefixed = new Uint8Array(encodePrefix(box.length)
.concat(slice(box)));
state++;
return void setTimeout(function () {
cb(void 0, prefixed);
});
}
// encrypt the rest of the file...
start = i * plainChunkLength;
end = start + plainChunkLength;
part = u8.subarray(start, end);
box = Nacl.secretbox(part, nonce, key);
increment(nonce);
i++;
// regular data is done
if (i * plainChunkLength >= u8.length) { state = 2; }
setTimeout(function () {
cb(void 0, box);
});
};
return next;
};
return {
decrypt: decrypt,
encrypt: encrypt,
joinChunks: joinChunks,
computeEncryptedSize: computeEncryptedSize,
};
});