279 lines
10 KiB
Rust
279 lines
10 KiB
Rust
//! The `budget_expr` module provides a domain-specific language for payment plans. Users create BudgetExpr objects that
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//! are given to an interpreter. The interpreter listens for `Witness` transactions,
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//! which it uses to reduce the payment plan. When the budget is reduced to a
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//! `Payment`, the payment is executed.
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use crate::payment_plan::{Payment, Witness};
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use crate::pubkey::Pubkey;
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use chrono::prelude::*;
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use std::mem;
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/// A data type representing a `Witness` that the payment plan is waiting on.
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#[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
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pub enum Condition {
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/// Wait for a `Timestamp` `Witness` at or after the given `DateTime`.
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Timestamp(DateTime<Utc>, Pubkey),
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/// Wait for a `Signature` `Witness` from `Pubkey`.
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Signature(Pubkey),
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}
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impl Condition {
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/// Return true if the given Witness satisfies this Condition.
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pub fn is_satisfied(&self, witness: &Witness, from: &Pubkey) -> bool {
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match (self, witness) {
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(Condition::Signature(pubkey), Witness::Signature) => pubkey == from,
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(Condition::Timestamp(dt, pubkey), Witness::Timestamp(last_time)) => {
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pubkey == from && dt <= last_time
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}
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_ => false,
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}
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}
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}
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/// A data type representing a payment plan.
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#[repr(C)]
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#[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
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pub enum BudgetExpr {
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/// Make a payment.
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Pay(Payment),
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/// Make a payment after some condition.
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After(Condition, Box<BudgetExpr>),
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/// Either make a payment after one condition or a different payment after another
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/// condition, which ever condition is satisfied first.
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Or((Condition, Box<BudgetExpr>), (Condition, Box<BudgetExpr>)),
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/// Make a payment after both of two conditions are satisfied
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And(Condition, Condition, Box<BudgetExpr>),
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}
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impl BudgetExpr {
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/// Create the simplest budget - one that pays `tokens` to Pubkey.
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pub fn new_payment(tokens: u64, to: Pubkey) -> Self {
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BudgetExpr::Pay(Payment { tokens, to })
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}
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/// Create a budget that pays `tokens` to `to` after being witnessed by `from`.
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pub fn new_authorized_payment(from: Pubkey, tokens: u64, to: Pubkey) -> Self {
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BudgetExpr::After(
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Condition::Signature(from),
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Box::new(Self::new_payment(tokens, to)),
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)
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}
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/// Create a budget that pays tokens` to `to` after being witnessed by 2x `from`s
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pub fn new_2_2_multisig_payment(from0: Pubkey, from1: Pubkey, tokens: u64, to: Pubkey) -> Self {
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BudgetExpr::And(
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Condition::Signature(from0),
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Condition::Signature(from1),
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Box::new(Self::new_payment(tokens, to)),
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)
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}
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/// Create a budget that pays `tokens` to `to` after the given DateTime.
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pub fn new_future_payment(dt: DateTime<Utc>, from: Pubkey, tokens: u64, to: Pubkey) -> Self {
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BudgetExpr::After(
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Condition::Timestamp(dt, from),
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Box::new(Self::new_payment(tokens, to)),
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)
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}
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/// Create a budget that pays `tokens` to `to` after the given DateTime
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/// unless cancelled by `from`.
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pub fn new_cancelable_future_payment(
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dt: DateTime<Utc>,
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from: Pubkey,
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tokens: u64,
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to: Pubkey,
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) -> Self {
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BudgetExpr::Or(
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(
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Condition::Timestamp(dt, from),
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Box::new(Self::new_payment(tokens, to)),
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),
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(
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Condition::Signature(from),
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Box::new(Self::new_payment(tokens, to)),
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),
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)
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}
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/// Return Payment if the budget requires no additional Witnesses.
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pub fn final_payment(&self) -> Option<Payment> {
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match self {
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BudgetExpr::Pay(payment) => Some(payment.clone()),
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_ => None,
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}
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}
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/// Return true if the budget spends exactly `spendable_tokens`.
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pub fn verify(&self, spendable_tokens: u64) -> bool {
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match self {
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BudgetExpr::Pay(payment) => payment.tokens == spendable_tokens,
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BudgetExpr::After(_, sub_expr) | BudgetExpr::And(_, _, sub_expr) => {
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sub_expr.verify(spendable_tokens)
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}
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BudgetExpr::Or(a, b) => a.1.verify(spendable_tokens) && b.1.verify(spendable_tokens),
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}
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}
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/// Apply a witness to the budget to see if the budget can be reduced.
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/// If so, modify the budget in-place.
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pub fn apply_witness(&mut self, witness: &Witness, from: &Pubkey) {
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let new_expr = match self {
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BudgetExpr::After(cond, sub_expr) if cond.is_satisfied(witness, from) => {
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Some(sub_expr.clone())
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}
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BudgetExpr::Or((cond, sub_expr), _) if cond.is_satisfied(witness, from) => {
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Some(sub_expr.clone())
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}
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BudgetExpr::Or(_, (cond, sub_expr)) if cond.is_satisfied(witness, from) => {
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Some(sub_expr.clone())
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}
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BudgetExpr::And(cond0, cond1, sub_expr) => {
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if cond0.is_satisfied(witness, from) {
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Some(Box::new(BudgetExpr::After(cond1.clone(), sub_expr.clone())))
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} else if cond1.is_satisfied(witness, from) {
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Some(Box::new(BudgetExpr::After(cond0.clone(), sub_expr.clone())))
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} else {
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None
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}
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}
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_ => None,
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};
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if let Some(expr) = new_expr {
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mem::replace(self, *expr);
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::signature::{Keypair, KeypairUtil};
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#[test]
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fn test_signature_satisfied() {
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let from = Pubkey::default();
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assert!(Condition::Signature(from).is_satisfied(&Witness::Signature, &from));
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}
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#[test]
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fn test_timestamp_satisfied() {
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let dt1 = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
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let dt2 = Utc.ymd(2014, 11, 14).and_hms(10, 9, 8);
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let from = Pubkey::default();
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assert!(Condition::Timestamp(dt1, from).is_satisfied(&Witness::Timestamp(dt1), &from));
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assert!(Condition::Timestamp(dt1, from).is_satisfied(&Witness::Timestamp(dt2), &from));
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assert!(!Condition::Timestamp(dt2, from).is_satisfied(&Witness::Timestamp(dt1), &from));
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}
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#[test]
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fn test_verify() {
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let dt = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
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let from = Pubkey::default();
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let to = Pubkey::default();
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assert!(BudgetExpr::new_payment(42, to).verify(42));
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assert!(BudgetExpr::new_authorized_payment(from, 42, to).verify(42));
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assert!(BudgetExpr::new_future_payment(dt, from, 42, to).verify(42));
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assert!(BudgetExpr::new_cancelable_future_payment(dt, from, 42, to).verify(42));
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}
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#[test]
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fn test_authorized_payment() {
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let from = Pubkey::default();
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let to = Pubkey::default();
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let mut expr = BudgetExpr::new_authorized_payment(from, 42, to);
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expr.apply_witness(&Witness::Signature, &from);
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assert_eq!(expr, BudgetExpr::new_payment(42, to));
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}
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#[test]
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fn test_future_payment() {
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let dt = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
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let from = Keypair::new().pubkey();
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let to = Keypair::new().pubkey();
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let mut expr = BudgetExpr::new_future_payment(dt, from, 42, to);
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expr.apply_witness(&Witness::Timestamp(dt), &from);
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assert_eq!(expr, BudgetExpr::new_payment(42, to));
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}
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#[test]
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fn test_unauthorized_future_payment() {
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// Ensure timestamp will only be acknowledged if it came from the
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// whitelisted public key.
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let dt = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
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let from = Keypair::new().pubkey();
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let to = Keypair::new().pubkey();
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let mut expr = BudgetExpr::new_future_payment(dt, from, 42, to);
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let orig_expr = expr.clone();
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expr.apply_witness(&Witness::Timestamp(dt), &to); // <-- Attack!
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assert_eq!(expr, orig_expr);
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}
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#[test]
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fn test_cancelable_future_payment() {
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let dt = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
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let from = Pubkey::default();
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let to = Pubkey::default();
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let mut expr = BudgetExpr::new_cancelable_future_payment(dt, from, 42, to);
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expr.apply_witness(&Witness::Timestamp(dt), &from);
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assert_eq!(expr, BudgetExpr::new_payment(42, to));
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let mut expr = BudgetExpr::new_cancelable_future_payment(dt, from, 42, to);
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expr.apply_witness(&Witness::Signature, &from);
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assert_eq!(expr, BudgetExpr::new_payment(42, from));
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}
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#[test]
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fn test_2_2_multisig_payment() {
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let from0 = Keypair::new().pubkey();
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let from1 = Keypair::new().pubkey();
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let to = Pubkey::default();
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let mut expr = BudgetExpr::new_2_2_multisig_payment(from0, from1, 42, to);
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expr.apply_witness(&Witness::Signature, &from0);
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assert_eq!(expr, BudgetExpr::new_authorized_payment(from1, 42, to));
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}
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#[test]
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fn test_multisig_after_sig() {
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let from0 = Keypair::new().pubkey();
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let from1 = Keypair::new().pubkey();
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let from2 = Keypair::new().pubkey();
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let to = Pubkey::default();
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let expr = BudgetExpr::new_2_2_multisig_payment(from0, from1, 42, to);
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let mut expr = BudgetExpr::After(Condition::Signature(from2), Box::new(expr));
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expr.apply_witness(&Witness::Signature, &from2);
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expr.apply_witness(&Witness::Signature, &from0);
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assert_eq!(expr, BudgetExpr::new_authorized_payment(from1, 42, to));
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}
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#[test]
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fn test_multisig_after_ts() {
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let from0 = Keypair::new().pubkey();
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let from1 = Keypair::new().pubkey();
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let dt = Utc.ymd(2014, 11, 11).and_hms(7, 7, 7);
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let to = Pubkey::default();
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let expr = BudgetExpr::new_2_2_multisig_payment(from0, from1, 42, to);
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let mut expr = BudgetExpr::After(Condition::Timestamp(dt, from0), Box::new(expr));
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expr.apply_witness(&Witness::Timestamp(dt), &from0);
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assert_eq!(
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expr,
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BudgetExpr::new_2_2_multisig_payment(from0, from1, 42, to)
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);
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expr.apply_witness(&Witness::Signature, &from0);
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assert_eq!(expr, BudgetExpr::new_authorized_payment(from1, 42, to));
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}
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}
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