cmz/tests/wallet.rs

// We want Scalars to be lowercase letters, and Points and credentials
// to be capital letters
#![allow(non_snake_case)]

use cmz::*;
use curve25519_dalek::ristretto::RistrettoPoint as G;
use group::Group;
use rand_core::RngCore;
use sha2::Sha512;

CMZ! { Wallet: randid, balance }
CMZ! { Item: serialno, price }

CMZProtocol! { wallet_issue,
  ,
  W: Wallet { randid: J, balance: S },
}

CMZProtocol! { item_issue,
  ,
  I: Item { serialno: S, price: S },
}

CMZProtocol! { wallet_spend,
  [ W: Wallet { randid: R, balance: H },
    I: Item { serialno: H, price: H } ],
  N: Wallet { randid: J, balance: H },
  N.balance >= 0,
  W.balance = N.balance + I.price
}

CMZProtocol! { wallet_spend_with_fee<fee>,
  [ W: Wallet { randid: R, balance: H },
    I: Item { serialno: H, price: H } ],
  N: Wallet { randid: J, balance: H },
  N.balance >= 0,
  W.balance = N.balance + I.price + fee
}

// The issuer runs this on its own to create an Item credential for a
// particular item (specified by a serial number) with a given price.
fn issue_item(
    rng: &mut impl RngCore,
    serialno: u128,
    price: u128,
    privkey: &CMZPrivkey<G>,
    public: &CMZPubkey<G>,
) -> Result<Item, CMZError> {
    let (request, state) = item_issue::prepare(&mut *rng, Item::using_pubkey(public))?;
    let (reply, _) = item_issue::handle(
        &mut *rng,
        request,
        |I: &mut Item| {
            I.set_privkey(privkey);
            I.serialno = Some(serialno.into());
            I.price = Some(price.into());
            Ok(())
        },
        |I: &Item| Ok(()),
    )?;
    let res = state.finalize(reply);
    match res {
        Ok(c) => Ok(c),
        Err((err, _state)) => Err(err),
    }
}

// The issuer runs this on its own to create an initial wallet loaded
// with funds, to sent to a client.  The issuer will presumably charge
// the client out of band for this loaded wallet.
fn issue_wallet(
    rng: &mut impl RngCore,
    balance: u128,
    privkey: &CMZPrivkey<G>,
    public: &CMZPubkey<G>,
) -> Result<Wallet, CMZError> {
    let (request, state) = wallet_issue::prepare(&mut *rng, Wallet::using_pubkey(public))?;
    let (reply, wallet) = wallet_issue::handle(
        &mut *rng,
        request,
        |W: &mut Wallet| {
            W.set_privkey(privkey);
            W.balance = Some(balance.into());
            Ok(())
        },
        |I: &Wallet| Ok(()),
    )?;
    let res = state.finalize(reply);
    match res {
        Ok(c) => Ok(c),
        Err((err, _state)) => Err(err),
    }
}

#[test]
fn test_wallet() -> Result<(), CMZError> {
    // Initialization
    let mut rng = rand::thread_rng();
    cmz_group_init(G::hash_from_bytes::<Sha512>(b"CMZ Generator A"));

    // Issuer: generate private and public keys for each type of
    // credential.  (The client gets a copy of the public keys.)
    let (wallet_priv, wallet_pub) = Wallet::cmz_gen_keys(&mut rng);
    let (item_priv, item_pub) = Item::cmz_gen_keys(&mut rng);

    // The issuer makes some Item credentials for various items by just
    // executing the issuing protocol with itself
    let ebook_item = issue_item(&mut rng, 100, 2995, &item_priv, &item_pub)?;
    let album_item = issue_item(&mut rng, 200, 995, &item_priv, &item_pub)?;

    // The verify_MAC function is only usable for debugging, since the
    // client will not have the private key and the issuer will
    // typically not have the complete credential.  But we'll use it
    // here to check that the credentials we get back are correct.
    ebook_item.verify_MAC(&item_priv).unwrap();
    album_item.verify_MAC(&item_priv).unwrap();

    // In exchange for out of band funds, the issuer generates a loaded
    // wallet and sends it to the client.
    let initial_wallet = issue_wallet(&mut rng, 10000, &wallet_priv, &wallet_pub)?;

    initial_wallet.verify_MAC(&wallet_priv).unwrap();

    // Buy an item (no fee version)

    // client actions
    let mut N = Wallet::using_pubkey(&wallet_pub);
    N.balance = Some(initial_wallet.balance.unwrap() - ebook_item.price.unwrap());
    let (request, state) = wallet_spend::prepare(&mut rng, &initial_wallet, &ebook_item, N)?;
    let reqbytes = request.as_bytes();

    // issuer actions
    let recvreq = wallet_spend::Request::try_from(&reqbytes[..]).unwrap();
    let (reply, (_W_issuer, _I_issuer, _N_issuer)) = wallet_spend::handle(
        &mut rng,
        recvreq,
        |W: &mut Wallet, I: &mut Item, N: &mut Wallet| {
            W.set_privkey(&wallet_priv);
            I.set_privkey(&item_priv);
            N.set_privkey(&wallet_priv);
            Ok(())
        },
        // This callback should test that W.randid has never been seen
        // before, but it doesn't currently do that.
        |W: &Wallet, I: &Item, N: &Wallet| Ok(()),
    )?;
    let replybytes = reply.as_bytes();

    // client actions
    let recvreply = wallet_spend::Reply::try_from(&replybytes[..]).unwrap();
    let W_issued = state.finalize(recvreply).unwrap();

    W_issued.verify_MAC(&wallet_priv).unwrap();

    // The version of the protocol parameterized by a fee.  The client
    // and issue must agree on the params.
    let params = wallet_spend_with_fee::Params { fee: 5u128.into() };

    // client actions
    let mut N_fee = Wallet::using_pubkey(&wallet_pub);

    N_fee.balance = Some(W_issued.balance.unwrap() - album_item.price.unwrap() - params.fee);

    let (request_fee, state_fee) =
        wallet_spend_with_fee::prepare(&mut rng, &W_issued, &album_item, N_fee, &params)?;
    let reqbytes_fee = request_fee.as_bytes();

    // issuer actions
    let recvreq_fee = wallet_spend_with_fee::Request::try_from(&reqbytes_fee[..]).unwrap();
    let (reply_fee, (_W_fee_issuer, _I_fee_isser, _N_fee_issuer)) = wallet_spend_with_fee::handle(
        &mut rng,
        recvreq_fee,
        |W: &mut Wallet, I: &mut Item, N: &mut Wallet| {
            W.set_privkey(&wallet_priv);
            I.set_privkey(&item_priv);
            N.set_privkey(&wallet_priv);
            Ok(wallet_spend_with_fee::Params { fee: params.fee })
        },
        // This callback should test that W.randid has never been seen
        // before, but it doesn't currently do that.
        |W: &Wallet, I: &Item, N: &Wallet| Ok(()),
    )?;
    let replybytes_fee = reply_fee.as_bytes();

    // client actions
    let recvreply_fee = wallet_spend_with_fee::Reply::try_from(&replybytes_fee[..]).unwrap();
    let W_issued_fee = state_fee.finalize(recvreply_fee).unwrap();

    W_issued_fee.verify_MAC(&wallet_priv).unwrap();

    Ok(())
}