sploit for arena-battle 3

notes/findings.md

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+# Findings — Brunnerne 2026 A/D
+
+## arena-battle (pwn, port 1337->31337)
+
+Status: partially patched (see services/arena-battle/PATCH_NOTES.md items 1-7).
+Sploit: challenges/pwn/arena-battle/work/sploit.py (+predictors.py) — token
+prediction via unsalted glibc rand(); verified 15/15 flags vs vulnerable build.
+
+### Remaining holes in OUR patched server (audit 2026-08-26)
+- [P1] NOTE_CREATE lines logged verbatim to logs/server.log -> any file-read
+  anywhere on box = flag dump. Fix: redact.
+- [P2] SLA: ATTACK ignores current_turn; anyone can FIGHT+ATTACK our checker's
+  fighter to hp=0 (dead forever until 1h cleanup) + steal gold. Fix: auto-revive
+  dead fighters after ~60s.
+- [P3] Memory DoS: battles map never erased, b.logs unbounded, inventory
+  push_back loop bounded only by gold. Fix: caps + GC of ended battles.
+- [P4] LOGOUT leaves fighter_battle entry (teardown skips because
+  client_fighter already erased) -> ghost-battle desync. Fix: logout ends battle.
+- [P5] write() not looped -> partial-write truncation on big NOTE listings.
+- Cleanup thread erases fighter_battle[fid] for OLD inactive battle even if fid
+  is now in a NEWER active battle (minor desync, low prio).
+
+### Offense roadmap (vs other teams' half-fixes)
+- default-seed rand(): DONE (glibc+darwin predictors).
+- srand(time(NULL)): TODO — brute-force seed from 1-2 self-registered tokens.
+- std::mt19937(time) / fixed seed: TODO — own mt19937 impl + state recovery
+  from tokens we harvest by registering (REGISTER echoes TOKEN).
+- NOTE_GET has no rate limit across reconnects (MAX_BAD_TOKENS is per-conn).
+
+### Verified facts
+- work/server.cpp == services_vulnerable/arena-battle/server.cpp (diff clean).
+- Flag format [A-Z0-9]{31}= ; store = fighter notes; NOTE_GET auths on token alone.
+- checker_sim.py: REGISTER CheckerX warrior + NOTE_CREATE <flag> <flag>.
+
+## Other services (not started)
+- rusgram, tiktak, "services 4" — pending triage.