yuurei/src/user.rs

//! User related things
use super::*;
use cryptohelpers::{
    rsa::{
	RsaPublicKey,
	Signature,
    },
    sha256::{self, Sha256Hash},
};
use std::borrow::Borrow;
use std::hash::{Hasher, Hash};

id_type!(UserID; "A unique user iD");

/// The salt added to to the user ID hash to be signed by the user's private key.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct UserSalt([u8; 16]);

impl UserSalt
{
    /// Generate a new random salt.
    pub fn generate() -> Self
    {
	let mut ar = [0u8; 16];
	getrandom::getrandom(&mut ar[..]).expect("rng fatal");
	Self(ar)
    }
}

impl UserID
{
    /// SHA256 hash this ID with a salt
    pub fn hash_with_salt(&self, salt: &UserSalt) -> Sha256Hash
    {
	sha256::compute_slice_iter(iter![&self.0.as_bytes()[..], &salt.0[..]])
    }

    /// Generate a new salt and then return that salt and this ID hashed with that new salt.
    ///
    /// This salt should be 
    pub fn generate_hash(&self) -> (UserSalt, Sha256Hash)
    {
	let salt = UserSalt::generate();
	let hash = self.hash_with_salt(&salt);
	(salt, hash)
    }
}

/// A user identifier.
///
/// Contains the user's unique ID, their public key(s), and a valid signature of the sha256 hash of the user's ID + a random salt.
///
/// # Hash
/// This type hashes to its unique ID, and also borrows to its unique ID.
#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct User
{
    /// The user's unique ID.
    id: UserID,

    /// A optional set of identifiers given by the user. The user must be trusted to set/edit this value.
    ident: post::Ident,

    /// The public keys associated with this user.
    ///
    /// # Trust
    /// Each public key must have a corresponding signature in its complemental entry in `id_sig` to be considered trusted.
    /// A user with no trusted public keys can be anyone or multiple people. This is not *disallowed* usually but should be discouraged.
    ///
    /// Users are only considered trusted if they have at least one trusted public key.
    pubkey: Vec<RsaPublicKey>,

    /// This vector contains the complemental signature (and salt used with `id` to produce the signed hash) to the public keys in `pubkey`. Each element of `pubkey` must have a complemental element in this vector.
    ///
    /// # Trusted public keys
    /// `None` values for this are signatures that have not yet been produces for a given salt, and do not count as complete. Public keys in `pubkey` that do not have a corresponding `Some` signature value in this field should not be trusted.
    id_sig: Vec<(UserSalt, Option<Signature>)>, 
}

impl Hash for User {
    fn hash<H: Hasher>(&self, state: &mut H) {
	self.id.hash(state)
    }
}


impl Borrow<UserID> for User
{
    fn borrow(&self) -> &UserID
    {
	&self.id
    }
}


impl User
{
    /// Is this user a trusted user?
    ///
    /// Does this user have at least one trusted public key (they have produced a valid signature specified in `id_sig`).
    pub fn is_trusted(&self) -> eyre::Result<bool>
    {
	for (i, (key, (salt, sig))) in (0..).zip(self.pubkey.iter().zip(self.id_sig.iter()))
	{
	    if let Some(sig) = sig {
		let hash = self.id.hash_with_salt(salt);
		if sig.verify_slice(&hash, key)
		    .with_section(move || format!("{:?}", key).header("Public key was"))
		    .with_section(move || format!("{:?}", sig).header("Signature was"))
		    .with_section(move || format!("{:?}", salt).header("Salt was"))
		    .with_section(move || format!("{:?}", hash).header("Hash was"))
		    .with_note(|| i.to_string().header("For pubkey"))
		    .with_note(|| format!("{:?} ({:?})", self.id, self.ident).header("For user"))
		    .with_warning(|| "This could indicate key or signature corruption. This key or signature may need to be removed.")
		    .with_suggestion(|| "If the user is unable to produce a verifyable signature for this public key despite haiving access to the private key, the key may be corrupted and may need to be removed and replaced.")
		    .wrap_err(eyre!("Failed to verify embedded signature of salted+hashed ID to complementary public key"))? {
			return Ok(true);
		    }
	    }
	}
	Ok(false)
    }
}