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change IV generation to match NIST spec (issue #9)
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@bain3
bain3 committed Aug 29, 2022
1 parent 3fe4349 commit 6c755f8
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Showing 2 changed files with 72 additions and 54 deletions.
119 changes: 68 additions & 51 deletions static/js/file.js
View file
Original file line number Diff line number Diff line change
@@ -1,8 +1,9 @@
const KEY_ALPHABET = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-._~()'!*:@,;";
const PBKDF2_ITERATIONS = 500000;
const CIPHER_VERSION = "v1";

// this is the block size if UNENCRYPTED data (+48 if encrypted to account for IV and tag)
const BLOCK_SIZE = 5242880;
// block size of unencrypted data (encrypted +16 bytes for GCM tag)
const BLOCK_SIZE = 1024 * 1024; // 1 MiB
const PBKDF2_ITERATIONS = 1_000_000;

/**
* Progress handler
Expand Down Expand Up @@ -65,30 +66,33 @@ class CryptoPair {
* @type ArrayBuffer
* @readonly
*/
ogBlockIV;
blockIVBase;
/**
* @type ArrayBuffer
* @readonly
*/
filenameIV;
filenameIVBase;

/** @type boolean */
_filenameEncrypted;
_filenameEncrypted = false;

/** @type Uint8Array */
_currentIV;
/**
* @type Number
* @readonly
*/
blockNumber = 0;

/** @type Uint8Array */
_rollbackIV;
/**
* @type boolean
* @readonly
*/
rolledBack = false;

constructor(password, key, ogBlockIV, filenameIV) {
this.password = password;
constructor(password, key, blockIVBase, filenameIVBase) {
this.key = key;
this.ogBlockIV = ogBlockIV;
this.filenameIV = filenameIV;
this._filenameEncrypted = false;
this._currentIV = ogBlockIV;
this._rollbackIV = ogBlockIV;
this.password = password;
this.blockIVBase = blockIVBase;
this.filenameIVBase = filenameIVBase;
}

/**
Expand All @@ -108,21 +112,37 @@ class CryptoPair {
false,
["deriveBits"]
);
// strengthened password for 1 key (128 bits) and 2 IVs (both 64 bits)
const strengthened = await subtle.deriveBits(
{ name: "PBKDF2", hash: "SHA-256", salt: salt, iterations: PBKDF2_ITERATIONS },
importedPassword,
768
256
);

const key = await subtle.importKey(
"raw",
strengthened.slice(0, 32),
strengthened.slice(0, 16),
"AES-GCM",
false,
["encrypt", "decrypt"]
);

return new CryptoPair(password, key, strengthened.slice(32, 64), strengthened.slice(64, 96));
return new CryptoPair(password, key, strengthened.slice(16, 24), strengthened.slice(24, 32));
}

/**
* Generate a full IV from a 8 byte base and a 4 byte unsigned integer
* @param {Uint8Array} ivBase
* @param {Number} n
* @returns {Uint8Array}
*/
genFullIV(ivBase, n = 0) {
let iv = new Uint8Array(12);
iv.set(ivBase, 0);
// converting n to little Uint little endian
const n_bytes = new Uint8Array([n >> 24 & 0xff, n >> 16 & 0xff, n >> 8 & 0xff, n & 0xff]);
iv.set(n_bytes, 8);
return iv;
}

/**
Expand All @@ -137,7 +157,7 @@ class CryptoPair {
this._filenameEncrypted = true;

let enc_bytes = await window.crypto.subtle.encrypt(
{ name: "AES-GCM", iv: this.filenameIV, tagLength: 128 },
{ name: "AES-GCM", iv: this.genFullIV(this.filenameIVBase, 0), tagLength: 128 },
this.key,
new TextEncoder().encode(filename)
);
Expand All @@ -148,27 +168,21 @@ class CryptoPair {
}

/**
* Encrypts a block of 5242880 (5MiB) bytes according to the f.bain protocol.
* Generates a new IV for next use.
* @param {Uint8Array} blockData 5242880
* Encrypts a block (BLOCK_SIZE bytes) according to the f.bain protocol.
* @param {Uint8Array} blockData BLOCK_SIZE sized block of data
* @returns {Promise<ArrayBuffer>} ciphertext
*/
async encryptBlock(blockData) {
const newIv = new Uint8Array(32);
window.crypto.getRandomValues(newIv);

let block = new Uint8Array(newIv.byteLength + blockData.byteLength);
block.set(newIv, 0);
block.set(blockData, 32);

const cipher = await window.crypto.subtle.encrypt(
{ name: "AES-GCM", iv: this._currentIV, tagLength: 128 },
const cipher = await window.crypto.subtle.encrypt({
name: "AES-GCM",
iv: this.genFullIV(this.blockIVBase, this.blockNumber++),
tagLength: 128
},
this.key,
block
blockData
);

this._rollbackIV = this._currentIV;
this._currentIV = newIv;
this.rolledBack = false;

return cipher;
}
Expand All @@ -177,7 +191,10 @@ class CryptoPair {
* Rollback IV to the previous block (used when connection drops)
*/
async rollbackIV() {
this._currentIV = this._rollbackIV;
if (!this.rolledBack) {
this.blockNumber--;
this.rolledBack = true;
}
}

/**
Expand All @@ -191,23 +208,25 @@ class CryptoPair {
for (let i = 0; i < b64.length; i++) decoded_cipher[i] = b64.charCodeAt(i);

return new TextDecoder().decode(await window.crypto.subtle.decrypt(
{ name: "AES-GCM", iv: this.filenameIV, tagLength: 128 },
{ name: "AES-GCM", iv: this.genFullIV(this.filenameIVBase, 0), tagLength: 128 },
this.key,
decoded_cipher
));
}

/**
* Decrypts a block of 5242928 (~5MiB) bytes according to the f.bain protocol.
* Decrypts a block of BLOCK_SIZE bytes according to the f.bain protocol.
* @param {ArrayBuffer} cipher
* @returns {Promise<ArrayBuffer>} block
*/
async decryptBlock(cipher) {
const d_block = await window.crypto.subtle.decrypt(
{ "name": "AES-GCM", "iv": this._currentIV, "tagLength": 128 },
this.key, cipher);
this._currentIV = new Uint8Array(d_block.slice(0, 32)); // update iv for next iteration
return d_block.slice(32, cipher.byteLength);
return await window.crypto.subtle.decrypt({
"name": "AES-GCM",
"iv": this.genFullIV(this.blockIVBase, this.blockNumber++),
"tagLength": 128
},
this.key, cipher
);
}

}
Expand All @@ -226,16 +245,14 @@ class LocalFile {
/**
* Upload this file to a host.
* @param {number} keyLength length of the encryption key
* @param {ProgressHandler} progressHandler optional handler for progress updates
* @param {string} host file host in format <protocol>://<host> leave undefined to
* use the current address as the host, notice no / at the end
* @param {ProgressHandler} progressHandler optional handler for progress updates
*
* @return {Promise<{uuid: string, revocationToken: string, password: string}>}
* object containing the uuid, revocationToken, and password
*/
async upload(keyLength, host, progressHandler) {
if (host === undefined) host = ""; // set default for host if not provided

async upload(keyLength, progressHandler, host = "") {
if (window.crypto === undefined) {
throw "browser does not support necessary cryptographic API";
}
Expand All @@ -262,7 +279,7 @@ class LocalFile {
}

progressHandler({ statusText: "creating session" });
const contentLength = Math.ceil(this.file.size / BLOCK_SIZE) * 48 + this.file.size;
const contentLength = Math.ceil(this.file.size / BLOCK_SIZE) * 16 + this.file.size;
const session_token = await this._createUploadSession(host, encryptedFilename, salt, contentLength);
const response = await this._uploadWithSession(host, session_token, keyPair, progressHandler);

Expand Down Expand Up @@ -493,7 +510,7 @@ class ForeignFile {
reject("File was not found");
return;
}
socket.send(JSON.stringify({ "read": BLOCK_SIZE + 48, "seek": offset }));
socket.send(JSON.stringify({ "read": BLOCK_SIZE + 16, "seek": offset }));
first_msg = false;
return;
}
Expand All @@ -515,7 +532,7 @@ class ForeignFile {
return;
}

socket.send(JSON.stringify({ "read": BLOCK_SIZE + 48 }));
socket.send(JSON.stringify({ "read": BLOCK_SIZE + 16 }));
};

socket.onclose = _ => {
Expand Down
7 changes: 4 additions & 3 deletions static/js/script.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -58,12 +58,13 @@ async function sendRequest(file) {
}

// upload file
progress_bar.update({ statusText: "generating key" });
const localFile = new LocalFile(file);
let resp;
try {
resp = await localFile.upload(strength, "", p => progress_bar.update(p));
resp = await localFile.upload(strength, p => progress_bar.update(p));
} catch (e) {
progress_bar.update({ status: "error", statusText: e })
progress_bar.update({ status: "error", statusText: e });
console.log(e);
return;
}
Expand All @@ -85,7 +86,7 @@ async function getMaxFileSize() {
let magnitudes = ["", "K", "M", "G", "T"];
let current_mag = 0;
while (size >= 1000 && current_mag < 4) {
size /= 1000
size /= 1000;
current_mag++;
}
R('filesize').innerText = Math.round(size * 10) / 10 + magnitudes[current_mag] + "B";
Expand Down

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