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keyfork-shard: generate nonce using hkdf

This commit is contained in:
Ryan Heywood 2024-04-09 19:46:37 -04:00
parent 2bca0a1580
commit 9394500f2f
Signed by: ryan
GPG Key ID: 8E401478A3FBEF72
4 changed files with 37 additions and 39 deletions
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2
Cargo.lock generated
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@ -1830,7 +1830,7 @@ dependencies = [
[[package]]
name = "keyfork-shard"
version = "0.1.0"
version = "0.2.0"
dependencies = [
"aes-gcm",
"anyhow",

2
crates/keyfork-shard/Cargo.toml
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@ -1,6 +1,6 @@
[package]
name = "keyfork-shard"
version = "0.1.0"
version = "0.2.0"
edition = "2021"
license = "AGPL-3.0-only"

70
crates/keyfork-shard/src/lib.rs
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@ -7,14 +7,17 @@ use std::{
};
use aes_gcm::{
aead::{consts::U12, Aead, AeadCore, OsRng},
aead::{consts::U12, Aead},
Aes256Gcm, KeyInit, Nonce,
};
use hkdf::Hkdf;
use keyfork_bug::{bug, POISONED_MUTEX};
use keyfork_mnemonic_util::{English, Mnemonic};
use keyfork_prompt::{
validators::{mnemonic::MnemonicSetValidator, Validator},
validators::{
mnemonic::{MnemonicSetValidator, MnemonicValidator, WordLength},
Validator,
},
Message as PromptMessage, PromptHandler, Terminal,
};
use sha2::Sha256;
@ -194,7 +197,6 @@ pub trait Format {
let encrypted_messages = self.parse_shard_file(reader)?;
// establish AES-256-GCM key via ECDH
let mut nonce_data: Option<[u8; 12]> = None;
let mut pubkey_data: Option<[u8; 32]> = None;
// receive remote data via scanning QR code from camera
@ -207,9 +209,8 @@ pub trait Format {
if let Ok(Some(hex)) =
keyfork_qrcode::scan_camera(std::time::Duration::from_secs(30), 0)
{
let decoded_data = smex::decode(&hex)?;
nonce_data = Some(decoded_data[..12].try_into().map_err(|_| InvalidData)?);
pubkey_data = Some(decoded_data[12..].try_into().map_err(|_| InvalidData)?)
let decoded_data = smex::decode(hex)?;
pubkey_data = Some(decoded_data.try_into().map_err(|_| InvalidData)?)
} else {
prompt
.lock()
@ -219,30 +220,23 @@ pub trait Format {
}
// if QR code scanning failed or was unavailable, read from a set of mnemonics
let (nonce, their_pubkey) = match (nonce_data, pubkey_data) {
(Some(nonce), Some(pubkey)) => (nonce, pubkey),
_ => {
let validator = MnemonicSetValidator {
word_lengths: [9, 24],
let their_pubkey = match pubkey_data {
Some(pubkey) => pubkey,
None => {
let validator = MnemonicValidator {
word_length: Some(WordLength::Count(24)),
};
let [nonce_mnemonic, pubkey_mnemonic] = prompt
prompt
.lock()
.expect(bug!(POISONED_MUTEX))
.prompt_validated_wordlist::<English, _>(
QRCODE_COULDNT_READ,
3,
validator.to_fn(),
)?;
let nonce = nonce_mnemonic
)?
.as_bytes()
.try_into()
.map_err(|_| InvalidData)?;
let pubkey = pubkey_mnemonic
.as_bytes()
.try_into()
.map_err(|_| InvalidData)?;
(nonce, pubkey)
.map_err(|_| InvalidData)?
}
};
@ -253,9 +247,14 @@ pub trait Format {
.diffie_hellman(&PublicKey::from(their_pubkey))
.to_bytes();
let hkdf = Hkdf::<Sha256>::new(None, &shared_secret);
let mut hkdf_output = [0u8; 256 / 8];
hkdf.expand(&[], &mut hkdf_output)?;
let shared_key = Aes256Gcm::new_from_slice(&hkdf_output)?;
let mut shared_key_data = [0u8; 256 / 8];
hkdf.expand(b"key", &mut shared_key_data)?;
let shared_key = Aes256Gcm::new_from_slice(&shared_key_data)?;
let mut nonce_data = [0u8; 12];
hkdf.expand(b"nonce", &mut nonce_data)?;
let nonce = Nonce::<U12>::from_slice(&nonce_data);
// decrypt a single shard and create the payload
let (share, threshold) =
@ -269,7 +268,6 @@ pub trait Format {
);
// encrypt data
let nonce = Nonce::<U12>::from_slice(&nonce);
let payload_bytes = shared_key.encrypt(nonce, payload.as_slice())?;
// convert data to a static-size payload
@ -432,16 +430,13 @@ pub fn remote_decrypt(w: &mut impl Write) -> Result<(), Box<dyn std::error::Erro
while iter_count.is_none() || iter_count.is_some_and(|i| i > 0) {
iter += 1;
let nonce = Aes256Gcm::generate_nonce(&mut OsRng);
let nonce_mnemonic = unsafe { Mnemonic::from_raw_bytes(nonce.as_slice()) };
let our_key = EphemeralSecret::random();
let key_mnemonic = Mnemonic::from_bytes(PublicKey::from(&our_key).as_bytes())?;
#[cfg(feature = "qrcode")]
{
use keyfork_qrcode::{qrencode, ErrorCorrection};
let mut qrcode_data = nonce_mnemonic.to_bytes();
qrcode_data.extend(key_mnemonic.as_bytes());
let qrcode_data = key_mnemonic.to_bytes();
if let Ok(qrcode) = qrencode(&smex::encode(&qrcode_data), ErrorCorrection::Highest) {
pm.prompt_message(PromptMessage::Text(format!(
concat!(
@ -458,10 +453,9 @@ pub fn remote_decrypt(w: &mut impl Write) -> Result<(), Box<dyn std::error::Erro
pm.prompt_message(PromptMessage::Text(format!(
concat!(
"Upon request, these words should be sent to shardholder {iter}: ",
"{nonce_mnemonic} {key_mnemonic}"
"{key_mnemonic}"
),
iter = iter,
nonce_mnemonic = nonce_mnemonic,
key_mnemonic = key_mnemonic,
)))?;
@ -506,12 +500,16 @@ pub fn remote_decrypt(w: &mut impl Write) -> Result<(), Box<dyn std::error::Erro
let shared_secret = our_key.diffie_hellman(&PublicKey::from(pubkey)).to_bytes();
let hkdf = Hkdf::<Sha256>::new(None, &shared_secret);
let mut hkdf_output = [0u8; 256 / 8];
hkdf.expand(&[], &mut hkdf_output)?;
let shared_key = Aes256Gcm::new_from_slice(&hkdf_output)?;
let payload =
shared_key.decrypt(&nonce, &payload[..payload[payload.len() - 1] as usize])?;
let mut shared_key_data = [0u8; 256 / 8];
hkdf.expand(b"key", &mut shared_key_data)?;
let shared_key = Aes256Gcm::new_from_slice(&shared_key_data)?;
let mut nonce_data = [0u8; 12];
hkdf.expand(b"nonce", &mut nonce_data)?;
let nonce = Nonce::<U12>::from_slice(&nonce_data);
let payload = shared_key.decrypt(nonce, &payload[..payload[payload.len() - 1] as usize])?;
assert_eq!(HUNK_VERSION, payload[0], "Incompatible hunk version");
match &mut iter_count {

2
crates/keyfork/Cargo.toml
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@ -32,7 +32,7 @@ keyfork-entropy = { version = "0.1.0", path = "../util/keyfork-entropy", registr
keyfork-mnemonic-util = { version = "0.2.0", path = "../util/keyfork-mnemonic-util", registry = "distrust" }
keyfork-prompt = { version = "0.1.0", path = "../util/keyfork-prompt", registry = "distrust" }
keyfork-qrcode = { version = "0.1.0", path = "../qrcode/keyfork-qrcode", default-features = false, registry = "distrust" }
keyfork-shard = { version = "0.1.0", path = "../keyfork-shard", default-features = false, features = ["openpgp", "openpgp-card", "qrcode"], registry = "distrust" }
keyfork-shard = { version = "0.2.0", path = "../keyfork-shard", default-features = false, features = ["openpgp", "openpgp-card", "qrcode"], registry = "distrust" }
smex = { version = "0.1.0", path = "../util/smex", registry = "distrust" }
clap = { version = "4.4.2", features = ["derive", "env", "wrap_help"] }