deploy_sage_on_docker

Posted on Edited on In Word count in article: 5k Reading time ≈ 5 mins.

记录下在docker上部署sage的密码学交互题目的过程。

0x1 Starting from cv

以下是maple佬出的一道题的deploy文件，给选手的py附件和deploy的py附件是同一个文件，非常方便，这也是我选它做模板的理由:

challenge.py

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from typing import Tuple
from Crypto.Util.number import *
from gmpy2 import powmod
import os

flag = os.environb.get(b"FLAG", b"TSJ{test_flag}")

def pow(a: int, b: int, c: int) -> int:
    # gmpy2.powmod is much faster than pow
    return int(powmod(a, b, c))

def getPrimeOrderGroup(bits) -> Tuple[int, int, int]:
    """
    Generate a prime p with large prime factor q and a generator g
    """
    while True:
        q = getPrime(bits)
        for i in range(2, 257, 2):
            p = q * i + 1
            if isPrime(p):
                g = pow(getRandomRange(2, p), i, p)
                if g != 1:
                    assert pow(g, q, p) == 1
                    return p, q, g

class RSA:
    def __init__(self, bits):
        self.p = getPrime(bits // 2)
        self.q = getPrime(bits // 2)
        self.n = self.p * self.q
        self.e = 65537
        self.d = pow(self.e, -1, (self.p - 1) * (self.q - 1))

    def encrypt(self, m: int) -> int:
        return pow(m, self.e, self.n)

    def decrypt(self, c: int) -> int:
        return pow(c, self.d, self.n)

    def __str__(self) -> str:
        e = self.e
        n = self.n
        return f"RSA({n}, {e})"

class ElGamal:
    def __init__(self, bits):
        self.p, self.q, self.g = getPrimeOrderGroup(bits)
        self.x = getRandomRange(2, self.q)
        self.y = pow(self.g, self.x, self.p)

    def encrypt(self, m: int) -> Tuple[int, int]:
        r = getRandomRange(2, self.q)
        s = pow(self.y, r, self.p)
        c1 = pow(self.g, r, self.p)
        c2 = (s * m) % self.p
        return c1, c2

    def decrypt(self, c1: int, c2: int) -> int:
        s = pow(c1, self.x, self.p)
        m = (pow(s, -1, self.p) * c2) % self.p
        return m

    def __str__(self) -> str:
        p = self.p
        g = self.g
        y = self.y
        return f"ElGamal({p}, {g}, {y})"

elg = ElGamal(1024)
rsa = RSA(1024)

print("Welcome to Cipher Switching Service!")
print()
print("This is our public keys:")
print(rsa)
print(elg)
print()
print("And this is some information about the encrypted flag:")
print(f"{len(flag) = }")
flag += os.urandom(96 - len(flag))  # random padding
flagenc = rsa.encrypt(bytes_to_long(flag))
print(f"{flagenc = }")
print()

for _ in range(1337):
    print("1. RSA to ElGamal")
    print("2. ElGamal to RSA")
    print("3. Quit")
    choice = int(input("> "))
    if choice == 1:
        c = int(input("c = "))
        print(elg.encrypt(rsa.decrypt(c)))
    elif choice == 2:
        c1 = int(input("c1 = "))
        c2 = int(input("c2 = "))
        print(rsa.encrypt(elg.decrypt(c1, c2)))
    elif choice == 3:
        print("Bye")
        break
    else:
        print(f"Unknown choice: {choice}")
else:
    print("To prevent abuse, we limit each session to have only 1337 attempts at most.")

Dockerfile

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FROM python:slim

RUN apt-get update && apt-get install -yqq socat

RUN pip install gmpy2 pycryptodome
RUN mkdir /app

WORKDIR /app
COPY challenge.py .

CMD ["/bin/sh", "-c", "socat TCP-LISTEN:8763,fork,reuseaddr EXEC:'python challenge.py',stderr"]

docker-compose.yml

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version: '3.9'
services:
  chall:
    build:
      context: .
    init: true
    environment:
      - FLAG=TSJ{a_weird_oracle?}
    ports:
      - 8763:8763

0x2 Deploy

在这个基础上修改成支持sage的python，首先就要解决安装sage的问题。主要遇到的问题有二：

  • debian.org连不上，apt-get报错
  • sagemath安装过慢

嘛，解决起来也简单，前者把基础镜像改成debian

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FROM debian:stable-slim

后者换源

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RUN sed -i 's/deb.debian.org/mirrors.ustc.edu.cn/g' /etc/apt/sources.list.d/debian.sources

就能非常爽滑的操作apt-get update -y sagemath了。

接下来的步骤大差不差，唯一有点卡的步骤是安装第三方库，按下面模板写就没问题了：

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RUN apt install -y python3-pip

RUN pip install pycryptodome --break-system-packages

操作基本完成，用qwb2022的一道题测试一下：

challenge.py

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from sage.all import *
from sage.modules.free_module_integer import IntegerLattice
from Crypto.Cipher import AES
from base64 import b64encode
from hashlib import *
import signal

flag = os.environb.get(b"FLAG", b"flag{114514}")

n = 75
m = 150
r = 10
N = 126633165554229521438977290762059361297987250739820462036000284719563379254544315991201997343356439034674007770120263341747898897565056619503383631412169301973302667340133958109

def gen(n, m, r, N):
    t1 = [ZZ.random_element(-2^15, 2^15) for _ in range(n*m)]
    t2 = [ZZ.random_element(N) for _ in range(r*n)]
    B = matrix(ZZ, n, m, t1)
    L = IntegerLattice(B)
    A = matrix(ZZ, r, n, t2)
    C = (A * B) % N
    return L, C

def pad(s):
    return s + (16 - len(s) % 16) * b"\x00"

signal.alarm(60)
L, C = gen(n, m, r, N)
print(C)
key = sha256(str(L.reduced_basis[0]).encode()).digest()
aes = AES.new(key, AES.MODE_ECB)
ct = b64encode(aes.encrypt(pad(flag))).decode()
print(ct)

Dockerfile

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FROM debian:stable-slim
RUN sed -i 's/deb.debian.org/mirrors.ustc.edu.cn/g' /etc/apt/sources.list.d/debian.sources

RUN apt-get update
RUN apt-get install -y socat 
RUN apt-get install -y sagemath

RUN apt install -y python3-pip

RUN pip install pycryptodome --break-system-packages

RUN mkdir /app

WORKDIR /app
COPY challenge.py .

CMD ["/bin/sh", "-c", "socat TCP-LISTEN:23333,fork,reuseaddr EXEC:'python3 challenge.py',stderr"]

docker-compose.yml

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version: '0.0'
services:
  chall:
    build:
      context: .
    init: true
    environment:
      - FLAG=flag{OK!_secret_number_is_114514}
    ports:
      - 23333:23333

最终效果：

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