Init. import

Marathon-PPC/README.md

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+## Информация для участников
+> Каждый уважающий себя CTFер обязан решать 150 примеров за 10 секунд
+
+## Решение
+Готовый скрипт: [solve/solve.py](solve/solver.py).
+
+## Флаг
+`caplag{There_1s_n0thing_m0re_1mp0rtant_f0r_pract1ce_than_g00d_the0ry}`

Marathon-PPC/solve/solver.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+
+import sys
+import os
+import math
+import socket
+from typing import List, Tuple
+
+
+def fib_fast(n: int) -> int:
+    def f(k: int) -> Tuple[int, int]:
+        if k == 0:
+            return (0, 1)
+        a, b = f(k >> 1)
+        c = a * (2 * b - a)
+        d = a * a + b * b
+        if k & 1:
+            return (d, c + d)
+        else:
+            return (c, d)
+    return f(n)[0]
+
+
+def arith_sum(a: int, b: int, s: int) -> int:
+
+    n = (b - a) // s + 1
+    return n * (a + b) // 2
+
+
+def integral_poly(a: int, b: int, coeff: List[int]) -> int:
+
+    res = 0
+    for k, c in enumerate(coeff):
+        e = k + 1
+        if c % e != 0:
+            raise ValueError("Non-integer term encountered; protocol assumption violated")
+        ce = c // e
+        res += ce * (pow(b, e) - pow(a, e))
+    return res
+
+
+def eval_expr(expr: str) -> int:
+    t = expr.strip().split()
+    if not t:
+        raise ValueError("Empty expression")
+    op = t[0]
+
+    def i(x: str) -> int:
+        return int(x)
+
+    if op == "plus":
+        return i(t[1]) + i(t[2])
+    if op == "minus":
+        return i(t[1]) - i(t[2])
+    if op == "times":
+        return i(t[1]) * i(t[2])
+    if op == "div":
+        a, b = i(t[1]), i(t[2])
+        return a // b
+    if op == "mod":
+        a, b = i(t[1]), i(t[2])
+        return a % b
+    if op == "pow":
+        a, b = i(t[1]), i(t[2])
+        return pow(a, b)
+    if op == "sqrt":
+        a = i(t[1])
+        r = math.isqrt(a)
+        return r
+    if op == "abs":
+        return abs(i(t[1]))
+    if op == "fact":
+        return math.factorial(i(t[1]))
+    if op == "gcd":
+        return math.gcd(i(t[1]), i(t[2]))
+    if op == "lcm":
+        a, b = i(t[1]), i(t[2])
+        g = math.gcd(a, b)
+        return a // g * b
+    if op == "det2":
+        a, b, c, d = i(t[1]), i(t[2]), i(t[3]), i(t[4])
+        return a * d - b * c
+    if op == "det3":
+        a, b, c = i(t[1]), i(t[2]), i(t[3])
+        d, e, f = i(t[4]), i(t[5]), i(t[6])
+        g, h, j = i(t[7]), i(t[8]), i(t[9])
+        return a * (e * j - f * h) - b * (d * j - f * g) + c * (d * h - e * g)
+    if op == "sum":
+        if t[3] != "step":
+            raise ValueError("Expected 'step' in sum expression")
+        a, b, s = i(t[1]), i(t[2]), i(t[4])
+        return arith_sum(a, b, s)
+    if op == "fib":
+        return fib_fast(i(t[1]))
+    if op == "lin1":
+        a, b, c = i(t[1]), i(t[2]), i(t[3])
+        return (c - b) // a
+    if op == "lin2x":
+        a1, b1, c1, a2, b2, c2 = i(t[1]), i(t[2]), i(t[3]), i(t[4]), i(t[5]), i(t[6])
+        D = a1 * b2 - a2 * b1
+        return (c1 * b2 - c2 * b1) // D
+    if op == "lin2y":
+        a1, b1, c1, a2, b2, c2 = i(t[1]), i(t[2]), i(t[3]), i(t[4]), i(t[5]), i(t[6])
+        D = a1 * b2 - a2 * b1
+        return (a1 * c2 - a2 * c1) // D
+    if op == "integral":
+        a, b = i(t[1]), i(t[2])
+        if t[3] != "poly":
+            raise ValueError("Expected 'poly' in integral expression")
+        coeff = list(map(int, t[4:]))
+        return integral_poly(a, b, coeff)
+
+    raise ValueError(f"Unknown operator: {op}")
+
+
+def run(host: str, port: int):
+    with socket.create_connection((host, port)) as sock:
+        sock_file = sock.makefile("rwb", buffering=0)
+        pending = None  # (expr_str, answer)
+        while True:
+            line = sock_file.readline()
+            if not line:
+                break
+            try:
+                s = line.decode().rstrip("\r\n")
+            except Exception:
+                continue
+            print(f"[SRV] {s}")
+
+            if s.startswith("Task ") and ":" in s:
+                try:
+                    expr = s.split(":", 1)[1].strip()
+                except Exception:
+                    expr = ""
+                ans = eval_expr(expr)
+                pending = (expr, ans)
+                print(f"[SOLVE] {expr} => {ans}")
+                continue
+
+            if s.strip().startswith(">") and pending is not None:
+                print(f"[SEND] {pending[1]}")
+                ans_bytes = str(pending[1]).encode() + b"\n"
+                sock_file.write(ans_bytes)
+                sock_file.flush()
+                pending = None
+                continue
+
+            if "Here is your flag:" in s or s.endswith("Bye."):
+                print(s)
+                continue
+
+
+def main():
+    host = sys.argv[1] if len(sys.argv) >= 2 else os.getenv("HOST", "127.0.0.1")
+    port = int(sys.argv[2]) if len(sys.argv) >= 3 else int(os.getenv("PORT", "5000"))
+    run(host, port)
+
+
+if __name__ == "__main__":
+    main()