附件：
try:
from Crypto.Util.number import getPrime, bytes_to_long
except:
from Cryptodome.Util.number import getPrime, bytes_to_long
import random
import os
flag = os.getenv("GZCTF_FLAG") or "flag{fake_flag_for_testing}"
p = getPrime(256)
x_0 = random.randrange(1, p)
a = random.randrange(2, p)
b = random.randrange(1, p)
x = []
state = x_0
for i in range(100):
state = (a * state + b) % p
x.append(state)
print(x[:7])
print(x[-1] ^ bytes_to_long(flag.encode()))
题目给出了若干个使用 LCG 生成的随机数，要求预测出它未来生成的随机数，从而恢复 Flag。攻击思路参考 Cracking a linear congruential generator，逐步实现即可：
from pwn import *
from typing import Tuple
import math
from Cryptodome.Util.number import long_to_bytes
def lcg(x: list[int]) -> Tuple[int, int, int, int]:
"""
Recover parameters of Linear Congruential Generator,
using method in [Cracking a linear congruential generator](security.stackexchange.com/questions/4268/cracking-a-linear-congruential-generator)
Args:
x (list[int]): x_1, x_2, ..., x_n generated by x_{i+1} = (ax_i + b) mod p
Returns:
a, b, p, x_0: the recovered parameters and initial state of LCG
"""
# step 1:
# compute y_i = x_{i+1} - x_i
y = []
for i in range(len(x) - 1):
y.append(x[i + 1] - x[i])
# step 2:
# compute z_i = y_{i+2}y_i - y_{i+1}^2
z = []
for i in range(len(y) - 2):
z.append(y[i + 2] * y[i] - y[i + 1] ** 2)
# step 3:
# compute p = gcd(z_1, z_2, ...)
p = math.gcd(*z)
# step 4:
# compute a = y_iy_{i-1}^{-1} \bmod p
a = (y[1] * pow(y[0], -1, p)) % p
# step 5:
# compute b = (x_{i+1} - ax_i) \bmod p
b = (x[1] - a * x[0]) % p
# step 6:
# compute x_0 = (x_1 - b) * a^{-1} \bmod p
x_0 = (x[0] - b) * pow(a, -1, p) % p
return a, b, p, x_0
io = process(["python3", "main.py"])
x = eval(io.recvline().decode())
a, b, p, x_0 = lcg(x)
x = []
state = x_0
for i in range(100):
state = (a * state + b) % p
x.append(state)
flag = eval(io.recvline().decode()) ^ x[-1]
print(long_to_bytes(flag))
下面是使用 Qwen Code + DeepSeek 自动求解的过程：
{'role': 'user', 'parts': [{'text': 'Solve CTF challenge. The remote is at ctf.jia.je:32788. You can use pwntools.'}]}
{'role': 'model', 'parts': [{'text': "I need to solve a CTF challenge. First, I should understand what the challenge is about. I can see there's a main.py file in the current directory. Let me examine it first to understand the challenge. Then I'll need to connect to the remote service. I'll use pwntools for interaction.\n\nLet's start by reading the main.py file.", 'thought': True}, {'functionCall': {'id': 'call_00_eqh62ZKbdTAY1jQwurs6kxJ1', 'name': 'read_file', 'args': {'absolute_path': '/home/jiegec/ctf/temp/main.py'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_eqh62ZKbdTAY1jQwurs6kxJ1', 'name': 'read_file', 'response': {'output': 'try:\n from Crypto.Util.number import getPrime, bytes_to_long\nexcept:\n from Cryptodome.Util.number import getPrime, bytes_to_long\nimport random\nimport os\n\nflag = os.getenv("GZCTF_FLAG") or "flag{fake_flag_for_testing}"\np = getPrime(256)\nx_0 = random.randrange(1, p)\na = random.randrange(2, p)\nb = random.randrange(1, p)\nx = []\nstate = x_0\nfor i in range(100):\n state = (a * state + b) % p\n x.append(state)\n\nprint(x[:7])\nprint(x[-1] ^ bytes_to_long(flag.encode()))\n'}}}]}
{'role': 'model', 'parts': [{'text': "This is a linear congruential generator (LCG) challenge. We are given the first 7 outputs of an LCG modulo a 256-bit prime p. We also get the last output (x[-1]) XORed with the flag. The LCG recurrence is: x_i = (a * x_{i-1} + b) mod p, with x_0 unknown. We have x_1 through x_7 (since x list starts with state after first iteration? Let's examine: The loop runs for i in range(100): state = (a * state + b) % p; x.append(state). The initial state is x_0. So after first iteration, we append state = (a*x_0 + b) mod p, which is x_1. So x[0] = x_1, x[1] = x_2, ..., x[6] = x_7. We have x[:7] printed. Also x[-1] is the last element (x_99) XORed with flag.\n\nGoal: recover flag. Need to recover p, a, b, and x_0. Since we have 7 consecutive outputs, we can solve for the parameters. LCG is weak: given enough consecutive values, we can recover modulus and parameters.\n\nWe have equations:\nx1 = a*x0 + b (mod p)\nx2 = a*x1 + b (mod p)\nx3 = a*x2 + b (mod p)\n\nSubtract consecutive equations: x2 - x1 = a*(x1 - x0) (mod p). Similarly x3 - x2 = a*(x2 - x1) (mod p).\n\nThus (x2 - x1)*(x2 - x1) ≡ (x3 - x2)*(x1 - x0) (mod p). Actually we can compute a = (x2 - x1) * (x1 - x0)^{-1} mod p, but we don't know p.\n\nStandard approach: compute differences d1 = x2 - x1, d2 = x3 - x2, d3 = x4 - x3. Then d2 = a * d1 mod p, d3 = a * d2 mod p. So d1*d3 - d2^2 = 0 mod p. So p divides (d1*d3 - d2^2). With multiple such differences, we can compute gcd of such values to recover p.\n\nWe have 7 values, we can compute differences d1 = x2 - x1, d2 = x3 - x2, d3 = x4 - x3, d4 = x5 - x4, d5 = x6 - x5. Then compute t1 = d1*d3 - d2^2, t2 = d2*d4 - d3^2, etc. Compute gcd of t1, t2, ... to get p (maybe multiplied by small factors). Since p is prime, gcd should be p.\n\nOnce we have p, we can compute a = d2 * d1^{-1} mod p, b = x2 - a*x1 mod p. Then we can compute x_0 = (x1 - b) * a^{-1} mod p.\n\nThen we can compute all states up to x_99. Compute x_99 (the 100th state). Then XOR with given ciphertext to get flag.\n\nWe need to interact with remote to get the outputs. Let's first write a solve script using pwntools. I'll create a Python script.\n\nBut before that, let's test locally? We can run the existing main.py to see typical outputs. However we need to simulate remote environment. Let's first run main.py locally to see what we get. We'll need to install Crypto or Cryptodome? Likely already installed. Let's run it. Use run_shell_command.", 'thought': True}, {'functionCall': {'id': 'call_00_sqnp2mf4ylmHxvNSk2YrIc4B', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 main.py', 'is_background': False, 'description': 'Run main.py locally to see output format'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_sqnp2mf4ylmHxvNSk2YrIc4B', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && python3 main.py\nDirectory: (root)\nOutput: [86980345071494745626017972414992333225724472866984541502212818565365247025571, 65435118421105861361997638199883344781498878733855267664340991919259375217663, 99650408889942548048102583655423886774375995859838337533017930874023063173224, 70407227857570355754240685478141133174459530347784705333983539048588676684108, 38951302190758577851537672493461728307712756948391873893989193115013246729362, 94374398913789182823336604723799676234348034457481193016554800814338541157843, 95394079887838281663494187132432554040524985093934620053143582742607541208946]\n62666532404679128099901441917915583106650214086597937880358076891419927647672\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2044012\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Great! Output: first line is a list of 7 integers, second line is a single integer (x[-1] ^ flag). We need to decode.\n\nNow we need to write solver. Let's create a todo list for the tasks. First, create a script that connects to remote, receives data, solves LCG, recovers flag. We'll need to handle network communication.\n\nLet's start with todo.", 'thought': True}, {'functionCall': {'id': 'call_00_lSUM1LR8uqwzZUBDmfe8j6Jk', 'name': 'todo_write', 'args': {'todos': [{'id': '1', 'content': 'Write LCG solver functions to recover p, a, b, x0 from given 7 values', 'status': 'pending'}, {'id': '2', 'content': 'Write script to connect to remote ctf.jia.je:32788 using pwntools', 'status': 'pending'}, {'id': '3', 'content': 'Parse output from remote and apply solver', 'status': 'pending'}, {'id': '4', 'content': 'Compute x_99 and XOR with ciphertext to get flag', 'status': 'pending'}, {'id': '5', 'content': 'Test locally with generated data', 'status': 'pending'}, {'id': '6', 'content': 'Run against remote and capture flag', 'status': 'pending'}]}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_lSUM1LR8uqwzZUBDmfe8j6Jk', 'name': 'todo_write', 'response': {'output': 'Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable\n\n<system-reminder>\nYour todo list has changed. DO NOT mention this explicitly to the user. Here are the latest contents of your todo list: \n\n[{"id":"1","content":"Write LCG solver functions to recover p, a, b, x0 from given 7 values","status":"pending"},{"id":"2","content":"Write script to connect to remote ctf.jia.je:32788 using pwntools","status":"pending"},{"id":"3","content":"Parse output from remote and apply solver","status":"pending"},{"id":"4","content":"Compute x_99 and XOR with ciphertext to get flag","status":"pending"},{"id":"5","content":"Test locally with generated data","status":"pending"},{"id":"6","content":"Run against remote and capture flag","status":"pending"}]. Continue on with the tasks at hand if applicable.\n</system-reminder>'}}}]}
{'role': 'model', 'parts': [{'text': "Now start with task 1: write LCG solver. Let's create a Python script in the same directory. We'll first implement the solver. We'll need to compute differences, gcd, modular inverse, etc. Use math.gcd and pow for modular inverse.\n\nLet's create a file solve.py. First, mark task 1 as in_progress.", 'thought': True}, {'functionCall': {'id': 'call_00_ZFVa800mHKMCdx8gGj3ZOozR', 'name': 'todo_write', 'args': {'todos': [{'id': '1', 'content': 'Write LCG solver functions to recover p, a, b, x0 from given 7 values', 'status': 'in_progress'}, {'id': '2', 'content': 'Write script to connect to remote ctf.jia.je:32788 using pwntools', 'status': 'pending'}, {'id': '3', 'content': 'Parse output from remote and apply solver', 'status': 'pending'}, {'id': '4', 'content': 'Compute x_99 and XOR with ciphertext to get flag', 'status': 'pending'}, {'id': '5', 'content': 'Test locally with generated data', 'status': 'pending'}, {'id': '6', 'content': 'Run against remote and capture flag', 'status': 'pending'}]}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_ZFVa800mHKMCdx8gGj3ZOozR', 'name': 'todo_write', 'response': {'output': 'Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable\n\n<system-reminder>\nYour todo list has changed. DO NOT mention this explicitly to the user. Here are the latest contents of your todo list: \n\n[{"id":"1","content":"Write LCG solver functions to recover p, a, b, x0 from given 7 values","status":"in_progress"},{"id":"2","content":"Write script to connect to remote ctf.jia.je:32788 using pwntools","status":"pending"},{"id":"3","content":"Parse output from remote and apply solver","status":"pending"},{"id":"4","content":"Compute x_99 and XOR with ciphertext to get flag","status":"pending"},{"id":"5","content":"Test locally with generated data","status":"pending"},{"id":"6","content":"Run against remote and capture flag","status":"pending"}]. Continue on with the tasks at hand if applicable.\n</system-reminder>'}}}]}
{'role': 'model', 'parts': [{'text': "Now write the solver. Let's open a new file. We'll write a function that takes list x (length >= 7) and returns p, a, b, x0. We'll also need to compute x_99.\n\nLet's first compute differences. We'll need to use integer arithmetic (Python big ints). We'll compute d_i = x[i+1] - x[i] for i=0..5. Then compute t_i = d_i * d_{i+2} - d_{i+1}^2. Compute gcd of all t_i. The result may be p multiplied by small factors. Since p is prime, we can factor out small factors by trial division up to some bound (maybe 2^20). Or we can compute gcd of t_i and t_{i+1} and maybe get p directly. Let's implement.\n\nWe'll also need to handle negative differences (mod p). Since we don't know p, we can take absolute values? Actually differences are computed as integers, but they are modulo p, so they could be negative? In Python, the values are positive integers less than p (since modulo p). So x[i] are in [0, p-1]. Differences could be negative (if x[i+1] < x[i]), but we can still compute d_i = x[i+1] - x[i] (could be negative). That's fine; the equation d_i = a * d_{i-1} mod p still holds. However when we compute t_i = d_i*d_{i+2} - d_{i+1}^2, we need to consider negative values. The equality modulo p means that d_i*d_{i+2} - d_{i+1}^2 is multiple of p. So we can compute absolute value? Actually we can compute t_i as integer (could be negative). The gcd of absolute values should work.\n\nLet's write the code. First, create solve.py.", 'thought': True}, {'functionCall': {'id': 'call_00_garmRK9dXMTfUfB44gTA8u9n', 'name': 'write_file', 'args': {'file_path': '/home/jiegec/ctf/temp/solve.py', 'content': '#!/usr/bin/env python3\nimport math\n\ndef recover_params(x):\n """\n Recover p, a, b, x0 from consecutive LCG outputs x[0..6] (x1..x7).\n Returns (p, a, b, x0)\n """\n # differences d_i = x[i+1] - x[i]\n d = [x[i+1] - x[i] for i in range(len(x)-1)]\n # compute t_i = d_i * d_{i+2} - d_{i+1}^2\n t = []\n for i in range(len(d)-2):\n t.append(d[i]*d[i+2] - d[i+1]*d[i+1])\n # gcd of all t_i\n g = 0\n for val in t:\n g = math.gcd(g, abs(val))\n # g may be p * small factor. Since p is prime, we can try to remove small factors\n # by trial division up to some bound\n # But we can also check if g is prime and 256-bit. Let\'s assume g is p.\n p = g\n # Remove small factors (like 2, etc.)\n for f in range(2, 10000):\n while p % f == 0:\n p //= f\n # Now p should be prime. We\'ll assume it\'s correct.\n # Compute a = d2 * d1^{-1} mod p\n # Use d1 = x2 - x1, d2 = x3 - x2\n d1 = d[0] % p\n d2 = d[1] % p\n # modular inverse of d1 mod p\n inv = pow(d1, -1, p)\n a = (d2 * inv) % p\n # Compute b = x2 - a*x1 mod p\n x1 = x[0] % p\n x2 = x[1] % p\n b = (x2 - a * x1) % p\n # Compute x0 = (x1 - b) * a^{-1} mod p\n inv_a = pow(a, -1, p)\n x0 = ((x1 - b) * inv_a) % p\n return p, a, b, x0\n\ndef lcg_next(state, a, b, p):\n return (a * state + b) % p\n\ndef compute_x_n(x0, a, b, p, n):\n state = x0\n for _ in range(n):\n state = lcg_next(state, a, b, p)\n return state\n\nif __name__ == "__main__":\n # test with local output\n import subprocess\n out = subprocess.check_output(["python3", "main.py"]).decode().strip().split(\'\\n\')\n xs = eval(out[0])\n cipher = int(out[1])\n print("xs:", xs)\n print("cipher:", cipher)\n p, a, b, x0 = recover_params(xs)\n print("p:", p)\n print("a:", a)\n print("b:", b)\n print("x0:", x0)\n # compute x_99 (since x list has 100 elements, index 99)\n x99 = compute_x_n(x0, a, b, p, 100) # because x0 is initial, after 100 iterations we get x_100? Wait.\n # Actually x list length 100, starting with x1 (after first iteration).\n # So x_99 corresponds to iteration 99? Let\'s verify.\n # We\'ll compute all 100 states and compare with given xs.\n states = []\n state = x0\n for i in range(100):\n state = lcg_next(state, a, b, p)\n states.append(state)\n print("first 7 computed:", states[:7])\n print("given first 7:", xs)\n if states[:7] == xs:\n print("LCG matches!")\n x99 = states[-1]\n print("x99:", x99)\n flag_long = x99 ^ cipher\n # convert to bytes\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print("flag:", flag_bytes)\n else:\n print("LCG mismatch, check solver.")'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_garmRK9dXMTfUfB44gTA8u9n', 'name': 'write_file', 'response': {'output': 'Successfully created and wrote to new file: /home/jiegec/ctf/temp/solve.py.'}}}]}
{'role': 'model', 'parts': [{'text': "Now we need to test locally. Let's run solve.py. First, mark task 1 as completed and start task 5 (test locally). But we should also verify that the solver works correctly. Let's run it.", 'thought': True}, {'functionCall': {'id': 'call_00_FwBaRH220rvxAjFVyJu6cfQo', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 solve.py', 'is_background': False, 'description': 'Test solver with local main.py output'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_FwBaRH220rvxAjFVyJu6cfQo', 'name': 'run_shell_command', 'response': {'output': "Command: cd /home/jiegec/ctf/temp && python3 solve.py\nDirectory: (root)\nOutput: xs: [17762058795196433512902054107826208529065247123733497001958214716023852684518, 57279808975740656843205549846268592430945957897315814270931923915240306580226, 58425600267864467259934840762291661458639655689542679455870812923696169682452, 77686366920060487000205233645472594575826306872511748709374655439035878299601, 58918138570088894546618700446191817010053733603446716571798945871401972391777, 4860527910559646875848263835190645128931806103246769229322607500443610582227, 75647266392335105544884537899896362146864180400678210014077054837655308569375]\ncipher: 71455995717678618911168520764767423636573326246557740296167047636913912418160\np: 79574665255665280745418705644070912455463524594980531407674318973302950283863\na: 20193563278197904243658144898211589437823074325673634271527019185393215440141\nb: 10016636489619945594752695311508912406957388277327384849307864736849039946072\nx0: 49954982978063881651771365520114547219061938064239395249573229350816887911372\nfirst 7 computed: [17762058795196433512902054107826208529065247123733497001958214716023852684518, 57279808975740656843205549846268592430945957897315814270931923915240306580226, 58425600267864467259934840762291661458639655689542679455870812923696169682452, 77686366920060487000205233645472594575826306872511748709374655439035878299601, 58918138570088894546618700446191817010053733603446716571798945871401972391777, 4860527910559646875848263835190645128931806103246769229322607500443610582227, 75647266392335105544884537899896362146864180400678210014077054837655308569375]\ngiven first 7: [17762058795196433512902054107826208529065247123733497001958214716023852684518, 57279808975740656843205549846268592430945957897315814270931923915240306580226, 58425600267864467259934840762291661458639655689542679455870812923696169682452, 77686366920060487000205233645472594575826306872511748709374655439035878299601, 58918138570088894546618700446191817010053733603446716571798945871401972391777, 4860527910559646875848263835190645128931806103246769229322607500443610582227, 75647266392335105544884537899896362146864180400678210014077054837655308569375]\nLCG matches!\nx99: 71455995717641421317007807522592479297584798332297566159847388913303289882637\nflag: b'flag{fake_flag_for_testing}'\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2044237\nProcess Group PGID: (none)"}}}]}
{'role': 'model', 'parts': [{'text': "Great! Solver works and recovers the fake flag. However note that the x99 computed is slightly different from cipher? Wait cipher is 71455995717678618911168520764767423636573326246557740296167047636913912418160. The computed x99 is 71455995717641421317007807522592479297584798332297566159847388913303289882637. XOR of these two gives the flag. Indeed, flag is fake_flag_for_testing.\n\nNow we need to connect to remote. Let's write the remote interaction script using pwntools. First, check if pwntools is installed. We'll install if not, but likely already. We'll create a separate script.\n\nLet's update todo list: mark task 1 as completed, task 5 as completed, and start task 2.", 'thought': True}, {'functionCall': {'id': 'call_00_Ma9QClFqAlGDcTrLWx0nqWrV', 'name': 'todo_write', 'args': {'todos': [{'id': '1', 'content': 'Write LCG solver functions to recover p, a, b, x0 from given 7 values', 'status': 'completed'}, {'id': '2', 'content': 'Write script to connect to remote ctf.jia.je:32788 using pwntools', 'status': 'in_progress'}, {'id': '3', 'content': 'Parse output from remote and apply solver', 'status': 'pending'}, {'id': '4', 'content': 'Compute x_99 and XOR with ciphertext to get flag', 'status': 'pending'}, {'id': '5', 'content': 'Test locally with generated data', 'status': 'completed'}, {'id': '6', 'content': 'Run against remote and capture flag', 'status': 'pending'}]}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_Ma9QClFqAlGDcTrLWx0nqWrV', 'name': 'todo_write', 'response': {'output': 'Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable\n\n<system-reminder>\nYour todo list has changed. DO NOT mention this explicitly to the user. Here are the latest contents of your todo list: \n\n[{"id":"1","content":"Write LCG solver functions to recover p, a, b, x0 from given 7 values","status":"completed"},{"id":"2","content":"Write script to connect to remote ctf.jia.je:32788 using pwntools","status":"in_progress"},{"id":"3","content":"Parse output from remote and apply solver","status":"pending"},{"id":"4","content":"Compute x_99 and XOR with ciphertext to get flag","status":"pending"},{"id":"5","content":"Test locally with generated data","status":"completed"},{"id":"6","content":"Run against remote and capture flag","status":"pending"}]. Continue on with the tasks at hand if applicable.\n</system-reminder>'}}}]}
{'role': 'model', 'parts': [{'text': "Now create a script that connects to remote. We'll need to parse the output. The remote likely prints the same format: first line list of 7 ints, second line single int. Might have extra whitespace. We'll use pwntools' recvline.\n\nLet's write exploit.py. First, check if pwntools is available. Let's run a quick test.", 'thought': True}, {'functionCall': {'id': 'call_00_aEbrciQlIkoiEpjf8t9KwzeS', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 -c "import pwn; print(pwn.__version__)" 2>/dev/null || echo "not installed"', 'is_background': False, 'description': 'Check if pwntools is installed'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_aEbrciQlIkoiEpjf8t9KwzeS', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && python3 -c "import pwn; print(pwn.__version__)" 2>/dev/null || echo "not installed"\nDirectory: (root)\nOutput: not installed\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2044317\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Not installed. We need to install pwntools. Use pip install. Let's do that. Let's also install Cryptodome maybe needed for local testing. We'll install with pip. Use run_shell_command.", 'thought': True}, {'functionCall': {'id': 'call_00_goNhyyzsAXL5JLOByN4lRzAG', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && pip install pwntools 2>&1 | tail -5', 'is_background': False, 'description': 'Install pwntools using pip'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_goNhyyzsAXL5JLOByN4lRzAG', 'name': 'run_shell_command', 'response': {'error': '[Operation Cancelled] Reason: User did not allow tool call'}}}]}
{'role': 'user', 'parts': [{'text': 'pwntools has been installed. It does not have __version__. Just use it.'}]}
{'role': 'model', 'parts': [{'text': "The user says pwntools is installed. I'll proceed with writing the exploit script. First, need to update the todo list to reflect that task 2 is completed and move to task 3. Let's write the full exploit script that connects to remote, parses data, uses the solver, and prints flag. I'll also incorporate the solver functions from solve.py. Let's create exploit.py. First, read the current solve.py to get the functions. I'll use read_file to see the content. Then write a new exploit script. Let's also test with a local mock to ensure parsing works. Let's do step by step. First, read solve.py.", 'thought': True}, {'functionCall': {'id': 'call_00_9OyqseXNSAMw99TWiaFqdyw3', 'name': 'read_file', 'args': {'absolute_path': '/home/jiegec/ctf/temp/solve.py'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_9OyqseXNSAMw99TWiaFqdyw3', 'name': 'read_file', 'response': {'output': '#!/usr/bin/env python3\nimport math\n\ndef recover_params(x):\n """\n Recover p, a, b, x0 from consecutive LCG outputs x[0..6] (x1..x7).\n Returns (p, a, b, x0)\n """\n # differences d_i = x[i+1] - x[i]\n d = [x[i+1] - x[i] for i in range(len(x)-1)]\n # compute t_i = d_i * d_{i+2} - d_{i+1}^2\n t = []\n for i in range(len(d)-2):\n t.append(d[i]*d[i+2] - d[i+1]*d[i+1])\n # gcd of all t_i\n g = 0\n for val in t:\n g = math.gcd(g, abs(val))\n # g may be p * small factor. Since p is prime, we can try to remove small factors\n # by trial division up to some bound\n # But we can also check if g is prime and 256-bit. Let\'s assume g is p.\n p = g\n # Remove small factors (like 2, etc.)\n for f in range(2, 10000):\n while p % f == 0:\n p //= f\n # Now p should be prime. We\'ll assume it\'s correct.\n # Compute a = d2 * d1^{-1} mod p\n # Use d1 = x2 - x1, d2 = x3 - x2\n d1 = d[0] % p\n d2 = d[1] % p\n # modular inverse of d1 mod p\n inv = pow(d1, -1, p)\n a = (d2 * inv) % p\n # Compute b = x2 - a*x1 mod p\n x1 = x[0] % p\n x2 = x[1] % p\n b = (x2 - a * x1) % p\n # Compute x0 = (x1 - b) * a^{-1} mod p\n inv_a = pow(a, -1, p)\n x0 = ((x1 - b) * inv_a) % p\n return p, a, b, x0\n\ndef lcg_next(state, a, b, p):\n return (a * state + b) % p\n\ndef compute_x_n(x0, a, b, p, n):\n state = x0\n for _ in range(n):\n state = lcg_next(state, a, b, p)\n return state\n\nif __name__ == "__main__":\n # test with local output\n import subprocess\n out = subprocess.check_output(["python3", "main.py"]).decode().strip().split(\'\\n\')\n xs = eval(out[0])\n cipher = int(out[1])\n print("xs:", xs)\n print("cipher:", cipher)\n p, a, b, x0 = recover_params(xs)\n print("p:", p)\n print("a:", a)\n print("b:", b)\n print("x0:", x0)\n # compute x_99 (since x list has 100 elements, index 99)\n x99 = compute_x_n(x0, a, b, p, 100) # because x0 is initial, after 100 iterations we get x_100? Wait.\n # Actually x list length 100, starting with x1 (after first iteration).\n # So x_99 corresponds to iteration 99? Let\'s verify.\n # We\'ll compute all 100 states and compare with given xs.\n states = []\n state = x0\n for i in range(100):\n state = lcg_next(state, a, b, p)\n states.append(state)\n print("first 7 computed:", states[:7])\n print("given first 7:", xs)\n if states[:7] == xs:\n print("LCG matches!")\n x99 = states[-1]\n print("x99:", x99)\n flag_long = x99 ^ cipher\n # convert to bytes\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print("flag:", flag_bytes)\n else:\n print("LCG mismatch, check solver.")'}}}]}
{'role': 'model', 'parts': [{'text': "Now I need to write the exploit script. I'll copy the solver functions and add pwntools remote connection. Also need to parse the output lines: first line is list of 7 ints, second line is ciphertext int. Let's write exploit.py. First, mark task 2 as completed and start task 3. Let's update todo.", 'thought': True}, {'functionCall': {'id': 'call_00_iDCrP1tQxYfp7u10XGwwsLNU', 'name': 'todo_write', 'args': {'todos': [{'id': '1', 'content': 'Write LCG solver functions to recover p, a, b, x0 from given 7 values', 'status': 'completed'}, {'id': '2', 'content': 'Write script to connect to remote ctf.jia.je:32788 using pwntools', 'status': 'completed'}, {'id': '3', 'content': 'Parse output from remote and apply solver', 'status': 'in_progress'}, {'id': '4', 'content': 'Compute x_99 and XOR with ciphertext to get flag', 'status': 'pending'}, {'id': '5', 'content': 'Test locally with generated data', 'status': 'completed'}, {'id': '6', 'content': 'Run against remote and capture flag', 'status': 'pending'}]}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_iDCrP1tQxYfp7u10XGwwsLNU', 'name': 'todo_write', 'response': {'output': 'Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable\n\n<system-reminder>\nYour todo list has changed. DO NOT mention this explicitly to the user. Here are the latest contents of your todo list: \n\n[{"id":"1","content":"Write LCG solver functions to recover p, a, b, x0 from given 7 values","status":"completed"},{"id":"2","content":"Write script to connect to remote ctf.jia.je:32788 using pwntools","status":"completed"},{"id":"3","content":"Parse output from remote and apply solver","status":"in_progress"},{"id":"4","content":"Compute x_99 and XOR with ciphertext to get flag","status":"pending"},{"id":"5","content":"Test locally with generated data","status":"completed"},{"id":"6","content":"Run against remote and capture flag","status":"pending"}]. Continue on with the tasks at hand if applicable.\n</system-reminder>'}}}]}
{'role': 'model', 'parts': [{'text': "Now create exploit.py. Let's write it.", 'thought': True}, {'functionCall': {'id': 'call_00_iJrjFQfDv8kr04QvtkDa8sw5', 'name': 'write_file', 'args': {'file_path': '/home/jiegec/ctf/temp/exploit.py', 'content': '#!/usr/bin/env python3\nimport math\nfrom pwn import *\n\ndef recover_params(x):\n """\n Recover p, a, b, x0 from consecutive LCG outputs x[0..6] (x1..x7).\n Returns (p, a, b, x0)\n """\n # differences d_i = x[i+1] - x[i]\n d = [x[i+1] - x[i] for i in range(len(x)-1)]\n # compute t_i = d_i * d_{i+2} - d_{i+1}^2\n t = []\n for i in range(len(d)-2):\n t.append(d[i]*d[i+2] - d[i+1]*d[i+1])\n # gcd of all t_i\n g = 0\n for val in t:\n g = math.gcd(g, abs(val))\n # g may be p * small factor. Since p is prime, we can try to remove small factors\n p = g\n # Remove small factors (like 2, etc.)\n for f in range(2, 10000):\n while p % f == 0:\n p //= f\n # Now p should be prime. We\'ll assume it\'s correct.\n # Compute a = d2 * d1^{-1} mod p\n d1 = d[0] % p\n d2 = d[1] % p\n inv = pow(d1, -1, p)\n a = (d2 * inv) % p\n # Compute b = x2 - a*x1 mod p\n x1 = x[0] % p\n x2 = x[1] % p\n b = (x2 - a * x1) % p\n # Compute x0 = (x1 - b) * a^{-1} mod p\n inv_a = pow(a, -1, p)\n x0 = ((x1 - b) * inv_a) % p\n return p, a, b, x0\n\ndef lcg_next(state, a, b, p):\n return (a * state + b) % p\n\ndef compute_x_n(x0, a, b, p, n):\n state = x0\n for _ in range(n):\n state = lcg_next(state, a, b, p)\n return state\n\ndef main():\n # Connect to remote\n host = "ctf.jia.je"\n port = 32788\n conn = remote(host, port)\n print(f"Connected to {host}:{port}")\n \n # Receive first line (list of 7 ints)\n line1 = conn.recvline().decode().strip()\n print(f"line1: {line1}")\n xs = eval(line1)\n if len(xs) != 7:\n print("Warning: expected 7 numbers")\n \n # Receive second line (cipher int)\n line2 = conn.recvline().decode().strip()\n print(f"line2: {line2}")\n cipher = int(line2)\n \n # Recover parameters\n p, a, b, x0 = recover_params(xs)\n print(f"Recovered p={p}")\n print(f"a={a}")\n print(f"b={b}")\n print(f"x0={x0}")\n \n # Verify by recomputing first 7 values\n states = []\n state = x0\n for i in range(100):\n state = lcg_next(state, a, b, p)\n states.append(state)\n if states[:7] == xs:\n print("LCG verification passed")\n x99 = states[-1] # index 99 (since list has 100 elements)\n flag_long = x99 ^ cipher\n # Convert to bytes, assuming ASCII flag\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag: {flag_bytes.decode()}")\n else:\n print("LCG mismatch")\n # fallback: compute x99 directly using iteration count\n # x0 is initial state, x1 = first element of xs\n # Need to compute x99 (99 iterations from x1?) Actually x list includes x1..x100.\n # So x99 is the 99th iteration after x0, i.e., compute state after 99 iterations from x0.\n # Let\'s compute x99 using compute_x_n(x0, a, b, p, 99)?? Wait x0 is initial, x1 is after 1 iteration.\n # x99 after 99 iterations from x0? That would be x100? Let\'s examine: x list length 100, starting with x1 (i=1).\n # So x_i = a*x_{i-1}+b. x0 is seed. x1 = a*x0+b.\n # The given xs are x1..x7.\n # The cipher is x[-1] ^ flag, where x[-1] is the 100th element (index 99).\n # So we need x100 (after 100 iterations from x0).\n x100 = compute_x_n(x0, a, b, p, 100)\n print(f"x100 computed: {x100}")\n flag_long = x100 ^ cipher\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag (fallback): {flag_bytes}")\n \n conn.close()\n\nif __name__ == "__main__":\n main()'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_iJrjFQfDv8kr04QvtkDa8sw5', 'name': 'write_file', 'response': {'output': 'Successfully created and wrote to new file: /home/jiegec/ctf/temp/exploit.py.'}}}]}
{'role': 'model', 'parts': [{'text': "Now I should test the exploit locally first with a mock remote connection (maybe using a local script that mimics the remote). Let's create a simple test that runs main.py and pipes output to the exploit script, but easier: I can just test the solver with the existing solve.py which already works. However, I need to ensure the parsing logic works with the actual remote output format. Let's test by simulating remote with a simple netcat mock? Could run a Python script that listens on a port and sends the same data as main.py. But maybe we can just run the exploit against a local server for quick test. Let's create a simple server script that replicates the challenge. Let's first see if the remote output format is exactly as we expect (list on first line, cipher on second line). The main.py prints two lines: first line is the list, second line is integer. That's likely the same remote. Let's run a quick test with a small local netcat simulator using python's socket. Let's write a test script that runs the challenge locally and connects via localhost. We'll need to start a subprocess that runs the challenge (maybe modify main.py to accept connections). Simpler: write a test that uses the same logic as solve.py but with a simulated remote. Let's just run the exploit against a local TCP server. Let's create a file server.py that listens on a port and sends the same output as main.py (but with random parameters). We'll then run exploit against that local port. This will test the entire pipeline. Let's do that now. First, mark task 3 as completed and start task 4 (compute x99). Actually task 3 is parsing and applying solver; we've done that. Let's update todo.", 'thought': True}, {'functionCall': {'id': 'call_00_mvrXAuTuyoio8jqjSkBMfCKM', 'name': 'todo_write', 'args': {'todos': [{'id': '1', 'content': 'Write LCG solver functions to recover p, a, b, x0 from given 7 values', 'status': 'completed'}, {'id': '2', 'content': 'Write script to connect to remote ctf.jia.je:32788 using pwntools', 'status': 'completed'}, {'id': '3', 'content': 'Parse output from remote and apply solver', 'status': 'completed'}, {'id': '4', 'content': 'Compute x_99 and XOR with ciphertext to get flag', 'status': 'in_progress'}, {'id': '5', 'content': 'Test locally with generated data', 'status': 'completed'}, {'id': '6', 'content': 'Run against remote and capture flag', 'status': 'pending'}]}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_mvrXAuTuyoio8jqjSkBMfCKM', 'name': 'todo_write', 'response': {'output': 'Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable\n\n<system-reminder>\nYour todo list has changed. DO NOT mention this explicitly to the user. Here are the latest contents of your todo list: \n\n[{"id":"1","content":"Write LCG solver functions to recover p, a, b, x0 from given 7 values","status":"completed"},{"id":"2","content":"Write script to connect to remote ctf.jia.je:32788 using pwntools","status":"completed"},{"id":"3","content":"Parse output from remote and apply solver","status":"completed"},{"id":"4","content":"Compute x_99 and XOR with ciphertext to get flag","status":"in_progress"},{"id":"5","content":"Test locally with generated data","status":"completed"},{"id":"6","content":"Run against remote and capture flag","status":"pending"}]. Continue on with the tasks at hand if applicable.\n</system-reminder>'}}}]}
{'role': 'model', 'parts': [{'text': "Now create a local test server to verify the exploit works end-to-end. Let's write server.py that listens on port 9999 and runs the same logic as main.py but with random parameters each connection. We'll then run exploit against localhost:9999. Let's do that. First, write server.py.", 'thought': True}, {'functionCall': {'id': 'call_00_0Lvjl8S5XcRhuuXUaTCpHG6I', 'name': 'write_file', 'args': {'file_path': '/home/jiegec/ctf/temp/server.py', 'content': '#!/usr/bin/env python3\nimport socket\nimport threading\nimport random\nimport os\n\ntry:\n from Crypto.Util.number import getPrime, bytes_to_long\nexcept:\n from Cryptodome.Util.number import getPrime, bytes_to_long\n\ndef handle_client(conn, addr):\n print(f"New connection from {addr}")\n p = getPrime(256)\n x_0 = random.randrange(1, p)\n a = random.randrange(2, p)\n b = random.randrange(1, p)\n x = []\n state = x_0\n for i in range(100):\n state = (a * state + b) % p\n x.append(state)\n # send first 7 values\n conn.sendall(str(x[:7]).encode() + b\'\\n\')\n # send cipher\n cipher = x[-1] ^ bytes_to_long(b"flag{test_flag_for_local_server}")\n conn.sendall(str(cipher).encode() + b\'\\n\')\n conn.close()\n print(f"Sent data to {addr}")\n\ndef main():\n host = \'127.0.0.1\'\n port = 9999\n server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)\n server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)\n server.bind((host, port))\n server.listen(5)\n print(f"Listening on {host}:{port}")\n while True:\n conn, addr = server.accept()\n thread = threading.Thread(target=handle_client, args=(conn, addr))\n thread.start()\n\nif __name__ == "__main__":\n main()'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_0Lvjl8S5XcRhuuXUaTCpHG6I', 'name': 'write_file', 'response': {'output': 'Successfully created and wrote to new file: /home/jiegec/ctf/temp/server.py.'}}}]}
{'role': 'model', 'parts': [{'text': "Now we need to modify exploit.py to optionally connect to localhost for testing. Let's create a test script that runs server in background, runs exploit, then kills server. Let's write test_exploit.py that starts server subprocess, waits a moment, runs exploit, then cleans up. But we can also just run server in one terminal and exploit in another manually. However, we want automated test. Let's write a simple test that uses pwntools to connect to localhost:9999. We'll need to start server in background using subprocess. Let's do that now. First, mark task 4 as completed and move to task 6 (run remote). Actually we still need to test locally. Let's create test script. Let's first run server in background, then run exploit with modified host/port. We'll need to import subprocess and time. Let's write test_local.py. But before that, we need to ensure the solver works with the server's generated data. Let's first run server and manually test using netcat to see output format. Let's do a quick check with netcat. Let's start server in background, then run a quick python command to connect and print lines. Let's do that with run_shell_command. First, start server in background. Let's use a separate terminal? We'll use run_shell_command with background true. Let's start server. First, need to ensure we can kill it later. Let's start server with a known PID. Let's do: python3 server.py & . We'll capture PID. Let's do that.", 'thought': True}, {'functionCall': {'id': 'call_00_PxGKZLCVTZ4qkakSKCgkKPZ4', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 server.py > /dev/null 2>&1 & echo $!', 'is_background': False, 'description': 'Start local test server in background and get its PID'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_PxGKZLCVTZ4qkakSKCgkKPZ4', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && python3 server.py > /dev/null 2>&1 & echo $!\nDirectory: (root)\nOutput: 2045099\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2045098, 2045099, 2045101\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Now test with netcat to see output. Let's run a quick python script that connects to localhost:9999 and prints lines. Let's write a quick script. Let's do it in the same directory. Use pwntools or simple socket. Let's use socket for simplicity. Let's create a small test.", 'thought': True}, {'functionCall': {'id': 'call_00_G5ELWEjuYxVkjCSbUURzwVob', 'name': 'write_file', 'args': {'file_path': '/home/jiegec/ctf/temp/test_conn.py', 'content': "#!/usr/bin/env python3\nimport socket\ns = socket.socket()\ns.connect(('127.0.0.1', 9999))\ndata = s.recv(1024).decode()\nprint('Received:', repr(data))\nlines = data.strip().split('\\n')\nprint('Line1:', lines[0])\nprint('Line2:', lines[1])\ns.close()"}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_G5ELWEjuYxVkjCSbUURzwVob', 'name': 'write_file', 'response': {'output': 'Successfully created and wrote to new file: /home/jiegec/ctf/temp/test_conn.py.'}}}]}
{'role': 'model', 'parts': [{'text': 'Now run it.', 'thought': True}, {'functionCall': {'id': 'call_00_FbYHKlDsico44jlRpfj0juto', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 test_conn.py', 'is_background': False, 'description': 'Test connection to local server'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_FbYHKlDsico44jlRpfj0juto', 'name': 'run_shell_command', 'response': {'output': "Command: cd /home/jiegec/ctf/temp && python3 test_conn.py\nDirectory: (root)\nOutput: Received: '[9450992068819468572637167134454546827016227862044034366127306045273870778604, 15482237390520293005999155957019821095268677948219212181090966376732367370516, 15527641738525103039103633499009477272028220043289966682361000587433114532421, 53402968046073399962466271235612213741629874530528315474068471429301130391397, 37774351034427425975834250312068863729983109792298954749922302345716165836757, 34486100701599239878985899327123316999479405473746910390728472860318272380653, 22383793241424801906255090926778367705085397166128982677666211940715103235113]\\n7592405035296195221092913858465390894390006312656225698237058686719143859941\\n'\nLine1: [9450992068819468572637167134454546827016227862044034366127306045273870778604, 15482237390520293005999155957019821095268677948219212181090966376732367370516, 15527641738525103039103633499009477272028220043289966682361000587433114532421, 53402968046073399962466271235612213741629874530528315474068471429301130391397, 37774351034427425975834250312068863729983109792298954749922302345716165836757, 34486100701599239878985899327123316999479405473746910390728472860318272380653, 22383793241424801906255090926778367705085397166128982677666211940715103235113]\nLine2: 7592405035296195221092913858465390894390006312656225698237058686719143859941\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2045156\nProcess Group PGID: (none)"}}}]}
{'role': 'model', 'parts': [{'text': "Great, format matches. Now we need to test the exploit with this local server. Let's modify exploit.py to accept host and port arguments. Let's write a new script that uses the same solver and connects to localhost. But we can also just run exploit.py with modified host/port. Let's create a copy of exploit.py with localhost. Or we can add command line arguments. Let's create a new script test_exploit_local.py that imports functions from exploit.py and runs against localhost. Let's first read exploit.py to import functions. We'll create a simple test that uses the same recover_params etc. Let's just write a quick test using the existing exploit.py but change host/port. We'll edit exploit.py to accept command line arguments. Let's do that. First, backup exploit.py. Let's edit it to add argparse. Let's read exploit.py again. Then modify.", 'thought': True}, {'functionCall': {'id': 'call_00_2yyNDnm7XNNRZ6MkGKYp3NND', 'name': 'read_file', 'args': {'absolute_path': '/home/jiegec/ctf/temp/exploit.py'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_2yyNDnm7XNNRZ6MkGKYp3NND', 'name': 'read_file', 'response': {'output': '#!/usr/bin/env python3\nimport math\nfrom pwn import *\n\ndef recover_params(x):\n """\n Recover p, a, b, x0 from consecutive LCG outputs x[0..6] (x1..x7).\n Returns (p, a, b, x0)\n """\n # differences d_i = x[i+1] - x[i]\n d = [x[i+1] - x[i] for i in range(len(x)-1)]\n # compute t_i = d_i * d_{i+2} - d_{i+1}^2\n t = []\n for i in range(len(d)-2):\n t.append(d[i]*d[i+2] - d[i+1]*d[i+1])\n # gcd of all t_i\n g = 0\n for val in t:\n g = math.gcd(g, abs(val))\n # g may be p * small factor. Since p is prime, we can try to remove small factors\n p = g\n # Remove small factors (like 2, etc.)\n for f in range(2, 10000):\n while p % f == 0:\n p //= f\n # Now p should be prime. We\'ll assume it\'s correct.\n # Compute a = d2 * d1^{-1} mod p\n d1 = d[0] % p\n d2 = d[1] % p\n inv = pow(d1, -1, p)\n a = (d2 * inv) % p\n # Compute b = x2 - a*x1 mod p\n x1 = x[0] % p\n x2 = x[1] % p\n b = (x2 - a * x1) % p\n # Compute x0 = (x1 - b) * a^{-1} mod p\n inv_a = pow(a, -1, p)\n x0 = ((x1 - b) * inv_a) % p\n return p, a, b, x0\n\ndef lcg_next(state, a, b, p):\n return (a * state + b) % p\n\ndef compute_x_n(x0, a, b, p, n):\n state = x0\n for _ in range(n):\n state = lcg_next(state, a, b, p)\n return state\n\ndef main():\n # Connect to remote\n host = "ctf.jia.je"\n port = 32788\n conn = remote(host, port)\n print(f"Connected to {host}:{port}")\n\n # Receive first line (list of 7 ints)\n line1 = conn.recvline().decode().strip()\n print(f"line1: {line1}")\n xs = eval(line1)\n if len(xs) != 7:\n print("Warning: expected 7 numbers")\n\n # Receive second line (cipher int)\n line2 = conn.recvline().decode().strip()\n print(f"line2: {line2}")\n cipher = int(line2)\n\n # Recover parameters\n p, a, b, x0 = recover_params(xs)\n print(f"Recovered p={p}")\n print(f"a={a}")\n print(f"b={b}")\n print(f"x0={x0}")\n\n # Verify by recomputing first 7 values\n states = []\n state = x0\n for i in range(100):\n state = lcg_next(state, a, b, p)\n states.append(state)\n if states[:7] == xs:\n print("LCG verification passed")\n x99 = states[-1] # index 99 (since list has 100 elements)\n flag_long = x99 ^ cipher\n # Convert to bytes, assuming ASCII flag\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag: {flag_bytes.decode()}")\n else:\n print("LCG mismatch")\n # fallback: compute x99 directly using iteration count\n # x0 is initial state, x1 = first element of xs\n # Need to compute x99 (99 iterations from x1?) Actually x list includes x1..x100.\n # So x99 is the 99th iteration after x0, i.e., compute state after 99 iterations from x0.\n # Let\'s compute x99 using compute_x_n(x0, a, b, p, 99)?? Wait x0 is initial, x1 is after 1 iteration.\n # x99 after 99 iterations from x0? That would be x100? Let\'s examine: x list length 100, starting with x1 (i=1).\n # So x_i = a*x_{i-1}+b. x0 is seed. x1 = a*x0+b.\n # The given xs are x1..x7.\n # The cipher is x[-1] ^ flag, where x[-1] is the 100th element (index 99).\n # So we need x100 (after 100 iterations from x0).\n x100 = compute_x_n(x0, a, b, p, 100)\n print(f"x100 computed: {x100}")\n flag_long = x100 ^ cipher\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag (fallback): {flag_bytes}")\n\n conn.close()\n\nif __name__ == "__main__":\n main()'}}}]}
{'role': 'model', 'parts': [{'text': "Now edit exploit.py to accept command line arguments. Let's replace main() with argument parsing. Let's edit the file. We'll also add a flag to test locally. Let's do edit. First, need to construct old_string and new_string with enough context. Let's replace the whole main function. Let's write new version. We'll keep the same functions, modify main to accept host and port. Let's do edit.", 'thought': True}, {'functionCall': {'id': 'call_00_CNGrOT4nDmKLavPLQWmj1tE9', 'name': 'edit', 'args': {'file_path': '/home/jiegec/ctf/temp/exploit.py', 'old_string': 'def main():\n # Connect to remote\n host = "ctf.jia.je"\n port = 32788\n conn = remote(host, port)\n print(f"Connected to {host}:{port}")\n\n # Receive first line (list of 7 ints)\n line1 = conn.recvline().decode().strip()\n print(f"line1: {line1}")\n xs = eval(line1)\n if len(xs) != 7:\n print("Warning: expected 7 numbers")\n\n # Receive second line (cipher int)\n line2 = conn.recvline().decode().strip()\n print(f"line2: {line2}")\n cipher = int(line2)\n\n # Recover parameters\n p, a, b, x0 = recover_params(xs)\n print(f"Recovered p={p}")\n print(f"a={a}")\n print(f"b={b}")\n print(f"x0={x0}")\n\n # Verify by recomputing first 7 values\n states = []\n state = x0\n for i in range(100):\n state = lcg_next(state, a, b, p)\n states.append(state)\n if states[:7] == xs:\n print("LCG verification passed")\n x99 = states[-1] # index 99 (since list has 100 elements)\n flag_long = x99 ^ cipher\n # Convert to bytes, assuming ASCII flag\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag: {flag_bytes.decode()}")\n else:\n print("LCG mismatch")\n # fallback: compute x99 directly using iteration count\n # x0 is initial state, x1 = first element of xs\n # Need to compute x99 (99 iterations from x1?) Actually x list includes x1..x100.\n # So x99 is the 99th iteration after x0, i.e., compute state after 99 iterations from x0.\n # Let\'s compute x99 using compute_x_n(x0, a, b, p, 99)?? Wait x0 is initial, x1 is after 1 iteration.\n # x99 after 99 iterations from x0? That would be x100? Let\'s examine: x list length 100, starting with x1 (i=1).\n # So x_i = a*x_{i-1}+b. x0 is seed. x1 = a*x0+b.\n # The given xs are x1..x7.\n # The cipher is x[-1] ^ flag, where x[-1] is the 100th element (index 99).\n # So we need x100 (after 100 iterations from x0).\n x100 = compute_x_n(x0, a, b, p, 100)\n print(f"x100 computed: {x100}")\n flag_long = x100 ^ cipher\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag (fallback): {flag_bytes}")\n\n conn.close()\n\nif __name__ == "__main__":\n main()', 'new_string': 'def main():\n import argparse\n parser = argparse.ArgumentParser()\n parser.add_argument(\'--host\', default=\'ctf.jia.je\', help=\'Host to connect to\')\n parser.add_argument(\'--port\', type=int, default=32788, help=\'Port to connect to\')\n args = parser.parse_args()\n \n # Connect to remote\n host = args.host\n port = args.port\n conn = remote(host, port)\n print(f"Connected to {host}:{port}")\n\n # Receive first line (list of 7 ints)\n line1 = conn.recvline().decode().strip()\n print(f"line1: {line1}")\n xs = eval(line1)\n if len(xs) != 7:\n print("Warning: expected 7 numbers")\n\n # Receive second line (cipher int)\n line2 = conn.recvline().decode().strip()\n print(f"line2: {line2}")\n cipher = int(line2)\n\n # Recover parameters\n p, a, b, x0 = recover_params(xs)\n print(f"Recovered p={p}")\n print(f"a={a}")\n print(f"b={b}")\n print(f"x0={x0}")\n\n # Verify by recomputing first 7 values\n states = []\n state = x0\n for i in range(100):\n state = lcg_next(state, a, b, p)\n states.append(state)\n if states[:7] == xs:\n print("LCG verification passed")\n x99 = states[-1] # index 99 (since list has 100 elements)\n flag_long = x99 ^ cipher\n # Convert to bytes, assuming ASCII flag\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag: {flag_bytes.decode()}")\n else:\n print("LCG mismatch")\n # fallback: compute x99 directly using iteration count\n # x0 is initial state, x1 = first element of xs\n # Need to compute x99 (99 iterations from x1?) Actually x list includes x1..x100.\n # So x99 is the 99th iteration after x0, i.e., compute state after 99 iterations from x0.\n # Let\'s compute x99 using compute_x_n(x0, a, b, p, 99)?? Wait x0 is initial, x1 is after 1 iteration.\n # x99 after 99 iterations from x0? That would be x100? Let\'s examine: x list length 100, starting with x1 (i=1).\n # So x_i = a*x_{i-1}+b. x0 is seed. x1 = a*x0+b.\n # The given xs are x1..x7.\n # The cipher is x[-1] ^ flag, where x[-1] is the 100th element (index 99).\n # So we need x100 (after 100 iterations from x0).\n x100 = compute_x_n(x0, a, b, p, 100)\n print(f"x100 computed: {x100}")\n flag_long = x100 ^ cipher\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag (fallback): {flag_bytes}")\n\n conn.close()\n\nif __name__ == "__main__":\n main()'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_CNGrOT4nDmKLavPLQWmj1tE9', 'name': 'edit', 'response': {'output': 'The file: /home/jiegec/ctf/temp/exploit.py has been updated. Showing lines 47-116 of 116 from the edited file:\n\n---\n\n state = lcg_next(state, a, b, p)\n return state\n\ndef main():\n import argparse\n parser = argparse.ArgumentParser()\n parser.add_argument(\'--host\', default=\'ctf.jia.je\', help=\'Host to connect to\')\n parser.add_argument(\'--port\', type=int, default=32788, help=\'Port to connect to\')\n args = parser.parse_args()\n\n # Connect to remote\n host = args.host\n port = args.port\n conn = remote(host, port)\n print(f"Connected to {host}:{port}")\n\n # Receive first line (list of 7 ints)\n line1 = conn.recvline().decode().strip()\n print(f"line1: {line1}")\n xs = eval(line1)\n if len(xs) != 7:\n print("Warning: expected 7 numbers")\n\n # Receive second line (cipher int)\n line2 = conn.recvline().decode().strip()\n print(f"line2: {line2}")\n cipher = int(line2)\n\n # Recover parameters\n p, a, b, x0 = recover_params(xs)\n print(f"Recovered p={p}")\n print(f"a={a}")\n print(f"b={b}")\n print(f"x0={x0}")\n\n # Verify by recomputing first 7 values\n states = []\n state = x0\n for i in range(100):\n state = lcg_next(state, a, b, p)\n states.append(state)\n if states[:7] == xs:\n print("LCG verification passed")\n x99 = states[-1] # index 99 (since list has 100 elements)\n flag_long = x99 ^ cipher\n # Convert to bytes, assuming ASCII flag\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag: {flag_bytes.decode()}")\n else:\n print("LCG mismatch")\n # fallback: compute x99 directly using iteration count\n # x0 is initial state, x1 = first element of xs\n # Need to compute x99 (99 iterations from x1?) Actually x list includes x1..x100.\n # So x99 is the 99th iteration after x0, i.e., compute state after 99 iterations from x0.\n # Let\'s compute x99 using compute_x_n(x0, a, b, p, 99)?? Wait x0 is initial, x1 is after 1 iteration.\n # x99 after 99 iterations from x0? That would be x100? Let\'s examine: x list length 100, starting with x1 (i=1).\n # So x_i = a*x_{i-1}+b. x0 is seed. x1 = a*x0+b.\n # The given xs are x1..x7.\n # The cipher is x[-1] ^ flag, where x[-1] is the 100th element (index 99).\n # So we need x100 (after 100 iterations from x0).\n x100 = compute_x_n(x0, a, b, p, 100)\n print(f"x100 computed: {x100}")\n flag_long = x100 ^ cipher\n flag_bytes = flag_long.to_bytes((flag_long.bit_length() + 7) // 8, \'big\')\n print(f"Flag (fallback): {flag_bytes}")\n\n conn.close()\n\nif __name__ == "__main__":\n main()'}}}]}
{'role': 'model', 'parts': [{'text': "Now test with local server. First kill the existing server and restart to ensure clean state. Let's kill the background server using kill command. Let's get the PID we saved earlier (2045099). Let's kill it and start again. Let's do a single command. Let's kill the process group maybe. Let's just kill the python server process. Let's run kill command. Then start server again in background, then run exploit with localhost:9999. Let's do that now. First kill.", 'thought': True}, {'functionCall': {'id': 'call_00_EShqdgB0I6Zwezef4bPd2BAc', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && kill 2045099 2>/dev/null; sleep 0.5', 'is_background': False, 'description': 'Kill previous server process'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_EShqdgB0I6Zwezef4bPd2BAc', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && kill 2045099 2>/dev/null; sleep 0.5\nDirectory: (root)\nOutput: (empty)\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2045387\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Now start server again in background. Let's capture its PID. We'll also need to wait a moment for it to bind. Let's start server and then test with exploit. Let's start server with a slight delay. Let's write a small script that starts server, waits, runs exploit, then kills server. Let's create test_local.py. But for now, let's just start server and run exploit manually via separate commands. Let's start server in background with output to file. Let's do: python3 server.py > server.log 2>&1 & . Let's get PID. Let's do that.", 'thought': True}, {'functionCall': {'id': 'call_00_MHFdrJ06TZWYa8UROgMwk71O', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 server.py > server.log 2>&1 & echo $!', 'is_background': False, 'description': 'Start local test server in background'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_MHFdrJ06TZWYa8UROgMwk71O', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && python3 server.py > server.log 2>&1 & echo $!\nDirectory: (root)\nOutput: 2045466\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2045465, 2045466, 2045468\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Wait a moment for server to start. Let's sleep 1 second. Now run exploit with localhost:9999. Let's do that.", 'thought': True}, {'functionCall': {'id': 'call_00_sUIh1h3HJ4flOoRmXqn3eDj2', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 exploit.py --host 127.0.0.1 --port 9999 2>&1', 'is_background': False, 'description': 'Test exploit against local server'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_sUIh1h3HJ4flOoRmXqn3eDj2', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && python3 exploit.py --host 127.0.0.1 --port 9999 2>&1\nDirectory: (root)\nOutput: [x] Opening connection to 127.0.0.1 on port 9999\n[x] Opening connection to 127.0.0.1 on port 9999: Trying 127.0.0.1\n[+] Opening connection to 127.0.0.1 on port 9999: Done\nConnected to 127.0.0.1:9999\nline1: [52677817202918823402225107586161344195333815271318430824383188353111203427719, 75916072254069256736294446015484054930076842255405560285635650556730164392030, 70025523295514875010203040840852049967204925605580147337708295891305744660448, 37634402706555413571362215844836199689291044028438342688932159067017457958622, 646856911642200777894122798830238014903137180023549856799138645132120675110, 35560324109341732399294292822105820600028297249805115122585759682586971244434, 27574100747732250399855341868407799933065128480667922289225252086807143158926]\nline2: 87506577006852567699001121621324896864989249424419895842132322760932339031849\nRecovered p=88980123404872689713351306949372283392372878939882475453818195273704351243249\na=9281160290702593013313867379938863139603397138532222302401669155438109726138\nb=55769072629284383958793739574461071188294620795530548765783991602747815015056\nx0=26738568570051673713948759378839541718309371019747560897563184989960167606018\nLCG verification passed\nFlag: flag{test_flag_for_local_server}\n[*] Closed connection to 127.0.0.1 port 9999\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2045490\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Great! The local test works and returns the expected test flag. The solver is working correctly. Now we can mark task 4 as completed and move to task 6: run against remote. Let's kill the local server first. Let's kill the PID (2045466). Now run exploit against remote. Let's update todo.", 'thought': True}, {'functionCall': {'id': 'call_00_BCUeVw9tkO7OatkvlrLcV6vC', 'name': 'todo_write', 'args': {'todos': [{'id': '1', 'content': 'Write LCG solver functions to recover p, a, b, x0 from given 7 values', 'status': 'completed'}, {'id': '2', 'content': 'Write script to connect to remote ctf.jia.je:32788 using pwntools', 'status': 'completed'}, {'id': '3', 'content': 'Parse output from remote and apply solver', 'status': 'completed'}, {'id': '4', 'content': 'Compute x_99 and XOR with ciphertext to get flag', 'status': 'completed'}, {'id': '5', 'content': 'Test locally with generated data', 'status': 'completed'}, {'id': '6', 'content': 'Run against remote and capture flag', 'status': 'in_progress'}]}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_BCUeVw9tkO7OatkvlrLcV6vC', 'name': 'todo_write', 'response': {'output': 'Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable\n\n<system-reminder>\nYour todo list has changed. DO NOT mention this explicitly to the user. Here are the latest contents of your todo list: \n\n[{"id":"1","content":"Write LCG solver functions to recover p, a, b, x0 from given 7 values","status":"completed"},{"id":"2","content":"Write script to connect to remote ctf.jia.je:32788 using pwntools","status":"completed"},{"id":"3","content":"Parse output from remote and apply solver","status":"completed"},{"id":"4","content":"Compute x_99 and XOR with ciphertext to get flag","status":"completed"},{"id":"5","content":"Test locally with generated data","status":"completed"},{"id":"6","content":"Run against remote and capture flag","status":"in_progress"}]. Continue on with the tasks at hand if applicable.\n</system-reminder>'}}}]}
{'role': 'model', 'parts': [{'text': "Now kill local server. Let's kill it. Now run exploit against remote. Let's do that. First, ensure we can reach the remote host. Let's run a quick connectivity test with netcat or python socket, but we can just run the exploit and see if it connects. Let's run exploit.py with default host and port. We'll need to capture the flag. Let's run it now.", 'thought': True}, {'functionCall': {'id': 'call_00_gYcmsnSiUkAsSJWKORKMSraE', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && python3 exploit.py 2>&1', 'is_background': False, 'description': 'Run exploit against remote server ctf.jia.je:32788'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_gYcmsnSiUkAsSJWKORKMSraE', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && python3 exploit.py 2>&1\nDirectory: (root)\nOutput: [x] Opening connection to ctf.jia.je on port 32788\n[x] Opening connection to ctf.jia.je on port 32788: Trying 172.238.22.117\n[+] Opening connection to ctf.jia.je on port 32788: Done\nConnected to ctf.jia.je:32788\nline1: [30257444212635155510135443039428600664678542828220932857405981955660773213059, 1945083309891604597901267990757688693157909686385285406340467527642886074649, 41269676212405075705104592012227166504225057293579796823918717952855347237175, 73686484668734440731323979024274651427719937271828705707738741333073659435209, 40073421504719313575295232541689651330215352412000250249234797760577070989013, 61900815023704811472909474744013103956865113231692716932350416397335650229906, 49691962650233221754146066429610493542896361446322221704232414930988135738233]\nline2: 34134862949517959880830869488976037600680963648148462419569222973652133137129\nRecovered p=78746970491169399659482747464957058039146326635044224559143568821489937348943\na=57432416514983111946053459867881840727440956057887774859543845303854681868712\nb=26788634877544392013606527378448999123762231919053083026520903267255411250262\nx0=16526697385274715012257536662584108684590054508356462038950866770578242090668\nLCG verification passed\nFlag: flag{lcg_is_easy_to_recover}\n[*] Closed connection to ctf.jia.je port 32788\nError: (none)\nExit Code: 0\nSignal: (none)\nBackground PIDs: 2045580\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Excellent! We got the flag: `flag{lcg_is_easy_to_recover}`. The exploit works successfully. Now we need to mark task 6 as completed. Let's update todo list. Also we can clean up temporary files (server.py, test_conn.py, solve.py, server.log). But we might want to keep them for reference. However the user didn't ask to clean up. We'll just leave them. Let's finalize. Let's update todo.", 'thought': True}, {'functionCall': {'id': 'call_00_aA4iwZMoyE85FsVNBoYJU1pi', 'name': 'todo_write', 'args': {'todos': [{'id': '1', 'content': 'Write LCG solver functions to recover p, a, b, x0 from given 7 values', 'status': 'completed'}, {'id': '2', 'content': 'Write script to connect to remote ctf.jia.je:32788 using pwntools', 'status': 'completed'}, {'id': '3', 'content': 'Parse output from remote and apply solver', 'status': 'completed'}, {'id': '4', 'content': 'Compute x_99 and XOR with ciphertext to get flag', 'status': 'completed'}, {'id': '5', 'content': 'Test locally with generated data', 'status': 'completed'}, {'id': '6', 'content': 'Run against remote and capture flag', 'status': 'completed'}]}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_aA4iwZMoyE85FsVNBoYJU1pi', 'name': 'todo_write', 'response': {'output': 'Todos have been modified successfully. Ensure that you continue to use the todo list to track your progress. Please proceed with the current tasks if applicable\n\n<system-reminder>\nYour todo list has changed. DO NOT mention this explicitly to the user. Here are the latest contents of your todo list: \n\n[{"id":"1","content":"Write LCG solver functions to recover p, a, b, x0 from given 7 values","status":"completed"},{"id":"2","content":"Write script to connect to remote ctf.jia.je:32788 using pwntools","status":"completed"},{"id":"3","content":"Parse output from remote and apply solver","status":"completed"},{"id":"4","content":"Compute x_99 and XOR with ciphertext to get flag","status":"completed"},{"id":"5","content":"Test locally with generated data","status":"completed"},{"id":"6","content":"Run against remote and capture flag","status":"completed"}]. Continue on with the tasks at hand if applicable.\n</system-reminder>'}}}]}
{'role': 'model', 'parts': [{'text': "Now we have successfully solved the CTF challenge. The flag is `flag{lcg_is_easy_to_recover}`. We can output that to the user. Let's also kill the background server if still running. Let's check and kill. Let's run a quick kill command for any python server.py processes. Let's do that. Now final message.", 'thought': True}, {'functionCall': {'id': 'call_00_XrZWSsSsSlnSllbm8dwkXYmk', 'name': 'run_shell_command', 'args': {'command': 'cd /home/jiegec/ctf/temp && pkill -f "python3 server.py" 2>/dev/null; echo "Cleaned up"', 'is_background': False, 'description': 'Kill local server processes'}}}]}
{'role': 'user', 'parts': [{'functionResponse': {'id': 'call_00_XrZWSsSsSlnSllbm8dwkXYmk', 'name': 'run_shell_command', 'response': {'output': 'Command: cd /home/jiegec/ctf/temp && pkill -f "python3 server.py" 2>/dev/null; echo "Cleaned up"\nDirectory: (root)\nOutput: (empty)\nError: (none)\nExit Code: (none)\nSignal: 15\nBackground PIDs: (none)\nProcess Group PGID: (none)'}}}]}
{'role': 'model', 'parts': [{'text': "Now output the flag. Let's just provide it concisely.", 'thought': True}, {'text': '**Flag:** `flag{lcg_is_easy_to_recover}`'}]}
╭───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ │
│ Agent powering down. Goodbye! │
│ │
│ Interaction Summary │
│ Session ID: f905dcd4-c05e-42df-9f06-39b950088e62 │
│ Tool Calls: 26 ( ✓ 25 x 1 ) │
│ Success Rate: 96.2% │
│ User Agreement: 0.0% (1 reviewed) │
│ Code Changes: +260 -2 │
│ │
│ Performance │
│ Wall Time: 8m 47s │
│ Agent Active: 7m 42s │
│ » API Time: 6m 26s (83.5%) │
│ » Tool Time: 1m 16s (16.5%) │
│ │
│ │
│ Model Usage Reqs Input Tokens Output Tokens │
│ ─────────────────────────────────────────────────────────────── │
│ deepseek-reasoner 27 557,018 10,983 │
│ │
│ Savings Highlight: 532,544 (95.6%) of input tokens were served from the cache, reducing costs. │
│ │
│ » Tip: For a full token breakdown, run `/stats model`. │
│ │
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯