added material

This commit is contained in:
Jeremy Janella
2026-05-09 23:21:13 -04:00
commit 75faa5c410
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#!/usr/bin/env python3
import argparse
import requests
import torch
import torch.nn as nn
import torch.nn.functional as F
import torchvision.transforms as transforms
from PIL import Image
import io
import base64
import numpy as np
import sys
import os
def base64_to_tensor(base64_str: str) -> torch.Tensor:
"""
Convert base64-encoded PNG to tensor.
Args:
base64_str: Base64-encoded PNG string
Returns:
torch.Tensor: Image tensor in [0,1] range with shape (C, H, W)
"""
img_bytes = base64.b64decode(base64_str)
img = Image.open(io.BytesIO(img_bytes))
tensor = transforms.ToTensor()(img)
return tensor
def tensor_to_base64(tensor: torch.Tensor) -> str:
"""
Convert tensor to base64-encoded PNG.
Args:
tensor: Image tensor in [0,1] range with shape (C, H, W)
Returns:
str: Base64-encoded PNG string
"""
img_array = (tensor.permute(1, 2, 0).numpy() * 255).astype(np.uint8)
img = Image.fromarray(img_array)
buffer = io.BytesIO()
img.save(buffer, format='PNG')
buffer.seek(0)
return base64.b64encode(buffer.getvalue()).decode('utf-8')
class CIFAR10CNN(nn.Module):
"""
Simple CNN for CIFAR-10 classification.
Architecture:
- Conv block 1: 3→32 channels, BatchNorm, ReLU, MaxPool
- Conv block 2: 32→64 channels, BatchNorm, ReLU, MaxPool
- FC1: 64*8*8 → 128, ReLU, Dropout(0.5)
- FC2: 128 → 10 (logits)
"""
def __init__(self, num_classes: int = 10):
"""
Initialize the CNN.
Args:
num_classes: Number of output classes (default: 10 for CIFAR-10)
"""
super(CIFAR10CNN, self).__init__()
# First convolutional block
self.conv1 = nn.Conv2d(3, 32, kernel_size=3, padding=1)
self.bn1 = nn.BatchNorm2d(32)
self.relu1 = nn.ReLU()
self.pool1 = nn.MaxPool2d(2, 2) # 32x32 -> 16x16
# Second convolutional block
self.conv2 = nn.Conv2d(32, 64, kernel_size=3, padding=1)
self.bn2 = nn.BatchNorm2d(64)
self.relu2 = nn.ReLU()
self.pool2 = nn.MaxPool2d(2, 2) # 16x16 -> 8x8
# Fully connected layers
self.fc1 = nn.Linear(64 * 8 * 8, 128)
self.relu3 = nn.ReLU()
self.dropout = nn.Dropout(0.5)
self.fc2 = nn.Linear(128, num_classes)
def forward(self, x: torch.Tensor) -> torch.Tensor:
"""
Forward pass.
Args:
x: Input tensor of shape (batch_size, 3, 32, 32)
Returns:
torch.Tensor: Logits of shape (batch_size, num_classes)
"""
x = self.pool1(self.relu1(self.bn1(self.conv1(x))))
x = self.pool2(self.relu2(self.bn2(self.conv2(x))))
x = x.view(x.size(0), -1) # Flatten
x = self.dropout(self.relu3(self.fc1(x)))
x = self.fc2(x)
return x
def load_model(model_path: str, device: str = 'cuda') -> CIFAR10CNN:
"""
Load trained CIFAR-10 model.
Args:
model_path: Path to model checkpoint (.pth file)
device: Device to load model on ('cuda' or 'cpu')
Returns:
CIFAR10CNN: Loaded model in eval mode
"""
model = CIFAR10CNN(num_classes=10)
# Load checkpoint
checkpoint = torch.load(model_path, map_location=device)
# Handle both direct state_dict and checkpoint dict formats
if isinstance(checkpoint, dict) and 'model_state_dict' in checkpoint:
model.load_state_dict(checkpoint['model_state_dict'])
else:
model.load_state_dict(checkpoint)
model = model.to(device)
model.eval()
return model
def deepfool_attack(
model: nn.Module,
image: torch.Tensor,
mean: list,
std: list,
num_classes: int = 10,
overshoot: float = 0.02,
max_iter: int = 50,
device: str = 'cuda'
) -> tuple:
"""
DeepFool minimal perturbation attack.
This implements the complete DeepFool algorithm:
1. Linearize the classifier around the current point
2. For each class k != current_class:
- Compute gradient direction w_k that increases class k score
- Compute distance to the linearized decision boundary
3. Find the closest decision boundary
4. Take minimal step to reach that boundary (with overshoot)
5. Re-linearize and repeat until misclassification
Args:
model: Trained CIFAR-10 model
image: Clean image in [0,1] range, shape (3, 32, 32)
mean: Normalization mean per channel
std: Normalization std per channel
num_classes: Number of classes to consider
overshoot: Overshoot parameter to ensure crossing boundary
max_iter: Maximum iterations
device: Device to run attack on
Returns:
tuple: (adversarial_image, total_perturbation, iterations, final_class)
"""
# Prepare normalization tensors
mean_t = torch.tensor(mean, device=device).view(3, 1, 1)
std_t = torch.tensor(std, device=device).view(3, 1, 1)
# Work in pixel space [0,1]
x = image.clone().to(device)
x_orig = image.clone().to(device)
# Normalize for model
x_norm = (x - mean_t) / std_t
# Get initial prediction
with torch.no_grad():
logits = model(x_norm.unsqueeze(0))
current_class = logits.argmax(dim=1).item()
original_class = current_class
r_total = torch.zeros_like(x)
print(f"\n{'='*60}")
print(f"DeepFool Attack")
print(f"{'='*60}")
print(f"Original class: {original_class}")
print(f"Num classes: {num_classes}")
print(f"Overshoot: {overshoot}")
print(f"Max iterations: {max_iter}")
print(f"{'='*60}\n")
for iteration in range(max_iter):
# Enable gradients
x_norm = (x - mean_t) / std_t
x_norm.requires_grad = True
# Forward pass
logits = model(x_norm.unsqueeze(0))
current_class = logits.argmax(dim=1).item()
# Check if misclassified
if current_class != original_class:
print(f" Misclassification achieved at iteration {iteration + 1}")
print(f" New class: {current_class}")
break
# Find closest decision boundary
min_dist = float('inf')
best_w = None
best_f = None
for k in range(num_classes):
if k == current_class:
continue
# Zero gradients
if x_norm.grad is not None:
x_norm.grad.zero_()
# Gradient for class k
logits[0, k].backward(retain_graph=True)
grad_k = x_norm.grad.clone()
# Zero gradients
if x_norm.grad is not None:
x_norm.grad.zero_()
# Gradient for current class
logits[0, current_class].backward(retain_graph=True)
grad_current = x_norm.grad.clone()
# Direction: increases k, decreases current
w_k = grad_k - grad_current
# Score gap
f_k = (logits[0, k] - logits[0, current_class]).item()
# Distance to boundary in normalized space
w_norm = torch.norm(w_k)
dist = abs(f_k) / (w_norm + 1e-10)
# Track minimum
if dist < min_dist:
min_dist = dist
best_w = w_k
best_f = f_k
# Compute perturbation in normalized space
w_norm_sq = torch.norm(best_w)**2
r_i = (abs(best_f) / (w_norm_sq + 1e-10)) * best_w
# Convert to pixel space (chain rule)
r_i_pixel = r_i * std_t
# Apply perturbation with overshoot
r_total = r_total + (1 + overshoot) * r_i_pixel
x = x_orig + r_total
# Clip to valid range
x = torch.clamp(x, 0.0, 1.0)
if (iteration + 1) % 10 == 0:
# Check L2 in normalized space
with torch.no_grad():
x_norm_check = (x - mean_t) / std_t
orig_norm = (x_orig - mean_t) / std_t
l2 = torch.norm(x_norm_check - orig_norm).item()
print(f" Iteration {iteration + 1}/{max_iter} - L2 norm: {l2:.4f}")
print(f"\n{'='*60}")
print(f"Attack complete!")
print(f"{'='*60}\n")
return x.detach().cpu(), r_total.detach().cpu(), iteration + 1, current_class
def test_api_robustness(host: str, image: torch.Tensor) -> bool:
"""
Test API robustness against invalid inputs.
Args:
host: Challenge server host URL
image: Clean challenge image
Returns:
bool: True if all robustness tests pass
"""
print(f"\n{'='*60}")
print("API Robustness Tests")
print(f"{'='*60}\n")
all_passed = True
# Test 1: Invalid JSON
print("[Test 1] Invalid JSON format...")
try:
response = requests.post(
f"{host}/submit",
data="invalid json",
headers={'content-type': 'application/json'}
)
if response.status_code == 400:
print(" [+] Correctly rejected invalid JSON")
else:
print(f" [-] Expected 400, got {response.status_code}")
all_passed = False
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
# Test 2: Missing image field
print("\n[Test 2] Missing 'image' field...")
try:
response = requests.post(
f"{host}/submit",
json={"wrong_field": "data"}
)
if response.status_code == 400:
result = response.json()
if 'error' in result and 'image' in result['error'].lower():
print(" [+] Correctly rejected missing image field")
else:
print(f" [-] Expected error message about missing image field")
all_passed = False
else:
print(f" [-] Expected 400, got {response.status_code}")
all_passed = False
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
# Test 3: Invalid base64
print("\n[Test 3] Invalid base64 encoding...")
try:
response = requests.post(
f"{host}/submit",
json={"image": "not_valid_base64!!!"}
)
if response.status_code == 400:
print(" [+] Correctly rejected invalid base64")
else:
print(f" [-] Expected 400, got {response.status_code}")
all_passed = False
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
# Test 4: Corrupted image data
print("\n[Test 4] Corrupted image data...")
try:
# Send corrupted base64 that decodes but isn't a valid PNG
corrupted_base64 = base64.b64encode(b"not a valid png image").decode('utf-8')
response = requests.post(
f"{host}/submit",
json={"image": corrupted_base64}
)
if response.status_code == 400:
print(" [+] Correctly rejected corrupted image data")
else:
print(f" [-] Expected 400, got {response.status_code}")
all_passed = False
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
print(f"\n{'='*60}")
print(f"API Robustness: {'PASSED' if all_passed else 'FAILED'}")
print(f"{'='*60}\n")
return all_passed
def test_anti_cheat(host: str, model: nn.Module, image: torch.Tensor,
l2_threshold: float, mean: list, std: list,
device: str) -> bool:
"""
Test anti-cheat mechanisms for DeepFool.
Args:
host: Challenge server host URL
model: Trained model
image: Clean challenge image
l2_threshold: L2 constraint threshold
mean: Normalization mean
std: Normalization std
device: Device to run on
Returns:
bool: True if all anti-cheat tests pass
"""
print(f"\n{'='*60}")
print("Anti-Cheat Mechanism Tests")
print(f"{'='*60}\n")
all_passed = True
mean_t = torch.tensor(mean).view(3, 1, 1)
std_t = torch.tensor(std).view(3, 1, 1)
# Test 1: Clean image (no modification)
print("[Test 1] Submitting clean image (should fail)...")
try:
clean_base64 = tensor_to_base64(image)
response = requests.post(f"{host}/submit", json={"image": clean_base64})
result = response.json()
if not result['success'] and not result['validation']['misclassification']:
print(" [+] Correctly rejected clean image")
else:
print(" [-] Should reject clean image (no misclassification)")
all_passed = False
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
# Test 2: L2 perturbation too large
print("\n[Test 2] L2 perturbation exceeding threshold (should fail)...")
try:
large_pert = image.clone()
# Add large perturbation
large_pert = torch.clamp(large_pert + 0.5, 0, 1)
large_base64 = tensor_to_base64(large_pert)
response = requests.post(f"{host}/submit", json={"image": large_base64})
result = response.json()
if not result['success'] and not result['validation']['l2_satisfied']:
print(" [+] Correctly rejected oversized L2 perturbation")
else:
print(" [-] Should reject perturbation exceeding L2 threshold")
all_passed = False
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
# Test 3: I-FGSM attack (L∞-based, should fail L∞ check)
print("\n[Test 3] I-FGSM attack (L∞-based, should fail)...")
try:
x_fgsm = image.clone().to(device)
x_norm = (x_fgsm - mean_t.to(device)) / std_t.to(device)
x_norm.requires_grad = True
outputs = model(x_norm.unsqueeze(0))
target = torch.tensor([0], device=device) # Arbitrary target
# Targeted I-FGSM
for _ in range(20):
loss = F.cross_entropy(outputs, target)
model.zero_grad()
loss.backward()
grad_norm = x_norm.grad
grad_pixel = grad_norm / std_t.to(device)
x_fgsm = x_fgsm - 0.01 * grad_pixel.sign()
x_fgsm = torch.clamp(x_fgsm, 0, 1)
x_norm = (x_fgsm - mean_t.to(device)) / std_t.to(device)
x_norm.requires_grad = True
outputs = model(x_norm.unsqueeze(0))
x_fgsm = x_fgsm.cpu()
fgsm_base64 = tensor_to_base64(x_fgsm)
response = requests.post(f"{host}/submit", json={"image": fgsm_base64})
result = response.json()
if not result['success'] and not result['validation'].get('reasonable_linf', True):
print(" [+] Correctly rejected I-FGSM attack (L∞ too large)")
else:
print(" [-] Should reject I-FGSM attacks")
all_passed = False
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
# Test 4: Random perturbation (wrong direction)
print("\n[Test 4] Random perturbation (wrong direction, should fail)...")
try:
random_pert = image.clone()
# Small random perturbation that causes misclassification
noise = torch.randn_like(random_pert) * 0.03
random_pert = torch.clamp(random_pert + noise, 0, 1)
# Check if it causes misclassification
with torch.no_grad():
orig_norm = (image - mean_t) / std_t
rand_norm = (random_pert - mean_t) / std_t
orig_pred = model(orig_norm.unsqueeze(0).to(device)).argmax().item()
rand_pred = model(rand_norm.unsqueeze(0).to(device)).argmax().item()
if rand_pred != orig_pred:
random_base64 = tensor_to_base64(random_pert)
response = requests.post(f"{host}/submit", json={"image": random_base64})
result = response.json()
if not result['success'] and not result['validation'].get('deepfool_direction', True):
print(" [+] Correctly rejected random perturbation")
else:
print(" [-] Should reject random perturbations")
all_passed = False
else:
print(" [!] Random perturbation didn't cause misclassification, skipping")
except Exception as e:
print(f" [-] Exception: {e}")
all_passed = False
print(f"\n{'='*60}")
print(f"Anti-Cheat Tests: {'PASSED' if all_passed else 'FAILED'}")
print(f"{'='*60}\n")
return all_passed
def solve_challenge(host: str, device: str = 'cuda', run_tests: bool = False):
"""
Main solver function.
Args:
host: Challenge server host URL
device: Device for attack ('cuda' or 'cpu')
run_tests: Whether to run robustness and anti-cheat tests
"""
print(f"\n{'='*60}")
print(f"Skills Assessment 2")
print(f"{'='*60}\n")
# Determine model path (assume running from solver/ directory)
solver_dir = os.path.dirname(os.path.abspath(__file__))
challenge_dir = os.path.dirname(solver_dir)
assets_dir = os.path.join(challenge_dir, "assets")
model_path = os.path.join(assets_dir, "cifar10_model_best.pth")
# Ensure assets directory exists
os.makedirs(assets_dir, exist_ok=True)
# Fetch model if missing
if not os.path.exists(model_path):
print(f"[1/5] Model not found at {model_path}")
weights_url = f"{host}/model/weights" # Adjust if your endpoint differs
print(f"Attempting to download weights from: {weights_url}")
try:
resp = requests.get(weights_url, timeout=30)
resp.raise_for_status()
with open(model_path, "wb") as f:
f.write(resp.content)
print(f" Weights downloaded and saved to {model_path}")
except requests.exceptions.RequestException as e:
print(f"[-] Error: Failed to download model weights from {weights_url}")
print(f"Details: {e}")
print("Hint: Ensure the challenge server exposes /model/weights and is reachable.")
raise
# Step 1: Load model
print("[1/5] Loading CIFAR-10 model...")
model = load_model(model_path, device=device)
print(f" Model loaded on {device}")
# Step 2: Get challenge
print("\n[2/5] Fetching challenge...")
response = requests.get(f"{host}/challenge")
response.raise_for_status()
challenge = response.json()
print(f" Original class: {challenge['original_class']} ({challenge['original_class_name']})")
print(f" L2 threshold: {challenge['l2_threshold']}")
print(f" Num classes hint: {challenge['num_classes_hint']}")
print(f" Overshoot hint: {challenge['overshoot_hint']}")
# Step 3: Decode image
print("\n[3/5] Decoding challenge image...")
image = base64_to_tensor(challenge['image'])
mean = challenge['normalization']['mean']
std = challenge['normalization']['std']
print(f" Image shape: {image.shape}")
print(f" Normalization: mean={mean}, std={std}")
# Verify original prediction
with torch.no_grad():
mean_t = torch.tensor(mean).view(3, 1, 1)
std_t = torch.tensor(std).view(3, 1, 1)
img_norm = (image - mean_t) / std_t
orig_pred = model(img_norm.unsqueeze(0).to(device)).argmax(dim=1).item()
print(f" Verified original prediction: {orig_pred}")
# Optional: Run robustness and anti-cheat tests
if run_tests:
print("\n" + "="*60)
print("RUNNING SECURITY TESTS")
print("="*60)
robustness_passed = test_api_robustness(host, image)
anticheat_passed = test_anti_cheat(
host, model, image, challenge['l2_threshold'],
mean, std, device
)
if robustness_passed and anticheat_passed:
print(f"\n{'='*60}")
print("[+] ALL SECURITY TESTS PASSED")
print(f"{'='*60}\n")
else:
print(f"\n{'='*60}")
print("[-] SOME SECURITY TESTS FAILED")
print(f"{'='*60}\n")
print("Proceeding with legitimate attack...\n")
# Step 4: Run DeepFool attack
print("\n[4/5] Running DeepFool attack...")
adv_image, perturbation, iters, final_class = deepfool_attack(
model=model,
image=image,
mean=mean,
std=std,
num_classes=challenge['num_classes_hint'],
overshoot=challenge['overshoot_hint'],
max_iter=challenge['max_iterations_hint'],
device=device
)
print(f" Iterations: {iters}")
print(f" Final class: {final_class}")
# Verify L2 norm in normalized space
with torch.no_grad():
mean_t = torch.tensor(mean).view(3, 1, 1)
std_t = torch.tensor(std).view(3, 1, 1)
orig_norm = (image - mean_t) / std_t
adv_norm = (adv_image - mean_t) / std_t
delta_norm = adv_norm - orig_norm
l2_norm = torch.norm(delta_norm).item()
print(f" L2 norm (normalized): {l2_norm:.4f}")
print(f" Threshold: {challenge['l2_threshold']}")
print(f" Within threshold: {l2_norm <= challenge['l2_threshold']}")
# Step 5: Submit
print("\n[5/5] Submitting adversarial example...")
adv_base64 = tensor_to_base64(adv_image)
response = requests.post(
f"{host}/submit",
json={"image": adv_base64}
)
response.raise_for_status()
result = response.json()
# Display results
print(f"\n{'='*60}")
print("Validation Results")
print(f"{'='*60}")
validation = result['validation']
print(f"L2 norm: {validation['l2_norm']:.4f} / {validation['l2_threshold']}")
print(f"L2 constraint satisfied: {validation['l2_satisfied']}")
print(f"Valid range [0,1]: {validation['valid_range']}")
print(f"Original prediction: {validation['original_class']}")
print(f"Adversarial prediction: {validation['adversarial_class']}")
print(f"Misclassification: {validation['misclassification']}")
print(f"\nSuccess: {result['success']}")
if result['success']:
print(f"\n{'='*60}")
print(f"[+] FLAG: {result['flag']}")
print(f"{'='*60}\n")
else:
print(f"\n[-] {result['message']}")
if 'hint' in result:
print(f"[!] {result['hint']}\n")
def main():
"""Main entry point."""
parser = argparse.ArgumentParser(
description='Working solver for Skills Assessment 2'
)
parser.add_argument(
'--host',
type=str,
default='http://154.57.164.66:31701',
help='Challenge server host URL (default: http://localhost:8001)'
)
parser.add_argument(
'--device',
type=str,
default='cuda' if torch.cuda.is_available() else 'cpu',
help='Device to run attack on (default: cuda if available, else cpu)'
)
parser.add_argument(
'--skip-tests',
action='store_true',
help='Skip API robustness and anti-cheat tests (tests run by default)'
)
args = parser.parse_args()
try:
solve_challenge(args.host, args.device, not args.skip_tests)
except requests.exceptions.ConnectionError:
print(f"\n[-] Error: Could not connect to {args.host}")
print("Make sure the challenge server is running (./run.sh)\n")
except Exception as e:
print(f"\n[-] Error: {str(e)}\n")
raise
if __name__ == "__main__":
main()