Skip to content

fix(events): use saturating arithmetic for anchor_idx calculation in select_winners (closes #134) #145

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
rushikeshgarad2024-dev wants to merge 2 commits into
base: testnet
Choose a base branch
from
Open

fix(events): use saturating arithmetic for anchor_idx calculation in select_winners (closes #134) #145

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
5016889
fix(events): use saturating_add for anchor_idx calculation (closes #134)
rushikeshgarad2024-dev Sep 12, 2026
2b5ba60
fix(events): use fail-closed checked_add for anchor_idx calculation (…
rushikeshgarad2024-dev Sep 12, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion contracts/events/src/event_ops.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -734,7 +734,7 @@ pub fn select_winners(
.ok_or(Error::InvalidDistribution)? as i128;
let amount = base_escrow.saturating_mul(percent) / 100_i128;

let anchor_idx = existing_count + (idx as u32);
let anchor_idx = existing_count.saturating_add(idx as u32);

@almanax-ai almanax-ai Bot Sep 12, 2026

Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Info Severity severity

Arithmetic and Financial Logic: silent index collision risk in winner selection loop

existing_count.saturating_add(idx as u32) can clamp anchor_idx to u32::MAX instead of failing if existing_count + idx overflows. Because anchor_idx is persisted in PrizeAward and likely used later to locate the corresponding Winner, saturation could cause multiple awards to share the same anchor_idx, leading to incorrect lookups (wrong recipient/amount) or permanent inability to claim if the index no longer matches the appended winner row.

For persisted indices/anchors, prefer fail-closed arithmetic: use checked_add and return an explicit error (or enforce existing_count <= u32::MAX - winners.len()) so state cannot be written with a clamped/colliding anchor_idx.

Fix with MCP 
Almanax found a vulnerability. Can you take a look and fix it?
Finding ID: 14fe1965-603a-4858-8cd4-84c8baba6cfd
Actions
  • Reply /almanax ask <question> to ask a follow-up question.
  • Reply /almanax dismiss [<reason>] and it won't appear again in future scans.
  • Reply /almanax resolve [<reason>] to mark the finding as resolved.
  • Reply /almanax severity <level> [<reason>] to override the severity.

storage::append_winner(
env,
event_id,
Expand Down