Sidechannel timing attack vulnerability #81
Description
The auth_via_credentials function only performs the expensive-in-terms-of-time hash if a password hash is found for a given user. This means that response times of any endpoint that requires authentication will be significantly and observably (!!) shorter for users with invalid handles, giving potential attackers unauthorized information - if a response is longer than usual, then this user is a valid target.
pub async fn auth_via_credentials(
login: &str,
password: &str,
pool: &Pool<Postgres>,
) -> Result<User, OmniError> {
let hash = match sqlx::query!(
"SELECT password_hash FROM users WHERE handle = $1",
login
)
.fetch_one(pool)
.await
{
Ok(hash) => hash.password_hash,
Err(e) => match e {
sqlx::Error::RowNotFound => return Err(AuthError::InvalidCredentials)?,
_ => return Err(OmniError::SqlxError(e))?,
},
};
let argon = Argon2::default();
let hash = match PasswordHash::new(&hash) {
Ok(hash) => hash,
Err(e) => return Err(e)?,
};
match argon.verify_password(password.as_bytes(), &hash).is_ok() {
true => User::get_by_handle(login, pool).await,
false => Err(AuthError::InvalidCredentials)?,
}
}