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use rand::{thread_rng, Rng};
use sharks::{Share, Sharks};
use std::collections::HashSet;
use std::convert::{TryFrom, TryInto};
use std::fmt;
use xsalsa20poly1305::aead::generic_array::GenericArray;
use zeroize::Zeroize;
pub mod encrypt;
fn get_shares_to_take(num_shares: u8) -> HashSet<u8> {
let mut rng = thread_rng();
let mut shares_to_take = HashSet::new();
while shares_to_take.len() < num_shares.into() {
let next_index = rng.gen::<u8>();
if next_index > 0 {
shares_to_take.insert(next_index);
}
}
shares_to_take
}
pub fn share(secret: &[u8], num_shares: u8, threshold: u8) -> Result<Vec<Vec<u8>>, ShareError> {
if num_shares < 2 {
return Err(ShareError {
message: "At least 2 shares required".to_string(),
});
}
if threshold < 2 {
return Err(ShareError {
message: "Threshold must be at least 2".to_string(),
});
}
if threshold > num_shares {
return Err(ShareError {
message: "Threshold must not be greater than the number of shares".to_string(),
});
}
let sharks = Sharks(threshold);
let dealer = sharks.dealer(&secret[..]);
let shares_to_take = get_shares_to_take(num_shares);
Ok(dealer
.take(255)
.map(|s| Vec::from(&s))
.filter(|s| shares_to_take.contains(&s[0]))
.collect())
}
pub fn combine(shares_bytes: Vec<Vec<u8>>) -> Result<Vec<u8>, RecoveryError> {
let shares: Vec<Share> = shares_bytes
.iter()
.map(|s| Share::try_from(s.as_slice()).unwrap())
.collect();
let sharks = Sharks(shares.len().try_into().unwrap());
match sharks.recover(&shares) {
Ok(val) => Ok(val),
Err(err) => Err(err.into()),
}
}
pub fn share_authenticated(
secret: &[u8],
num_shares: u8,
threshold: u8,
) -> Result<(Vec<Vec<u8>>, Vec<u8>), ShareError> {
let mut key = encrypt::generate_key();
match share(&key, num_shares, threshold) {
Ok(shares) => {
let ciphertext = encrypt::encrypt(key, secret.to_vec()).unwrap();
key.zeroize();
Ok((shares, ciphertext))
}
Err(err) => Err(err),
}
}
pub fn combine_authenticated(
shares: Vec<Vec<u8>>,
ciphertext: Vec<u8>,
) -> Result<Vec<u8>, RecoveryError> {
let recovered_key = combine(shares)?;
let key = GenericArray::from_slice(&recovered_key[..]);
match encrypt::decrypt(*key, ciphertext) {
Ok(val) => Ok(val),
Err(err) => Err(err.into()),
}
}
#[derive(Debug)]
pub struct ShareError {
pub message: String,
}
impl fmt::Display for ShareError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "Cannot create shares: {}", self.message)
}
}
#[derive(Debug)]
pub struct RecoveryError {
pub message: String,
}
impl fmt::Display for RecoveryError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "Error during recovery {}", self.message)
}
}
impl From<xsalsa20poly1305::aead::Error> for RecoveryError {
fn from(error: xsalsa20poly1305::aead::Error) -> Self {
RecoveryError {
message: error.to_string(),
}
}
}
impl From<&str> for RecoveryError {
fn from(error: &str) -> Self {
RecoveryError {
message: String::from(error),
}
}
}
pub fn default_threshold(number_of_shares: u8) -> u8 {
if number_of_shares == 2 {
return 2;
};
(number_of_shares as f32 * 0.75) as u8
}
pub fn thresold_sanity(threshold: u8, number_of_shares: u8) -> i32 {
(threshold as i32) - (default_threshold(number_of_shares) as i32)
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn passes_on_all_shares() {
let original_secret = b"hello";
let shares = share(&original_secret[..], 5, 3).unwrap();
assert_eq!(shares.len(), 5);
let recovered_secret = combine(shares).unwrap();
assert_eq!(recovered_secret, b"hello");
}
#[test]
fn passes_on_threshold_amount() {
let original_secret = b"hello";
let mut shares = share(&original_secret[..], 5, 3).unwrap();
assert_eq!(shares.len(), 5);
shares.remove(0);
shares.remove(1);
assert_eq!(shares.len(), 3);
let recovered_secret = combine(shares).unwrap();
assert_eq!(recovered_secret, b"hello");
}
#[test]
fn authenticated() {
let original_secret = b"hello";
let (shares, ciphertext) = share_authenticated(&original_secret[..], 5, 3).unwrap();
assert_eq!(shares.len(), 5);
let recovered_secret = combine_authenticated(shares, ciphertext).unwrap();
assert_eq!(recovered_secret, b"hello");
}
#[test]
fn fails_on_insufficient_shares() {
let original_secret = b"hello";
let (mut shares, ciphertext) = share_authenticated(&original_secret[..], 5, 3).unwrap();
assert_eq!(shares.len(), 5);
shares.remove(0);
shares.remove(1);
shares.remove(2);
assert_eq!(shares.len(), 2);
let res = combine_authenticated(shares, ciphertext);
assert!(res.is_err());
}
#[test]
fn fails_on_impossible_threshold() {
let original_secret = b"hello";
let share_result = share(&original_secret[..], 5, 6);
assert!(share_result.is_err());
}
#[test]
fn fails_on_threshold_of_one() {
let original_secret = b"hello";
let share_result = share(&original_secret[..], 5, 1);
assert!(share_result.is_err());
}
#[test]
fn fails_on_creating_one_share() {
let original_secret = b"hello";
let share_result = share(&original_secret[..], 1, 1);
assert!(share_result.is_err());
}
#[test]
fn fails_on_bad_share() {
let original_secret = b"hello";
let (mut shares, ciphertext) = share_authenticated(&original_secret[..], 5, 3).unwrap();
shares[0] = b"bad share".to_vec();
let res = combine_authenticated(shares, ciphertext);
assert!(res.is_err());
}
#[test]
fn check_default_threshold() {
assert_eq!(thresold_sanity(7, 10), 0);
assert_eq!(thresold_sanity(5, 7), 0);
assert_eq!(thresold_sanity(3, 5), 0);
assert_eq!(thresold_sanity(2, 3), 0);
assert_eq!(thresold_sanity(2, 2), 0);
assert_eq!(thresold_sanity(2, 10), -5);
assert_eq!(thresold_sanity(9, 10), 2);
}
}