Merge pull request #100 from Philip-Zimmermann/main

- Fix image resize analyzer
- Fixed broken stegbrute URL
- Fix minor typos

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.11-slim AS build
+FROM python:3.14-slim AS build
 
 WORKDIR /
 

README.md

@@ -73,13 +73,13 @@ Here is a batch of usefull commands.
 
 ```bash
 docker compose down -v  # Remove volume containings results
-docker compose -f docker-compose-dev.yml up  # Start application in developpement mode
+docker compose -f compose.dev.yml up  # Start application in developpement mode
 rm -rf aperisolve/results  # Remove results from developpement mode
 docker exec -it postgres psql -U aperiuser -d aperisolve  # Get postgresql shell
 docker exec -it aperisolve-web bash # Get shell in running web app
 ```
 
-> Note, if you used [docker-compose-dev.yml](docker-compose-dev.yml), you must remove "results" when switching to [production docker](docker-compose.yml).
+> Note, if you used [compose.dev.yml](compose.dev.yml), you must remove "results" when switching to [production docker](compose.yml).
 
 ### Code quality
 
@@ -94,7 +94,6 @@ GitHub CI will alert in case of failure.
 
 ## Roadmap
 
-- [x] PngCheck
 - [ ] Zsteg extract / --all --> **Download `zsteg` files** such as mp3 encoded on LSB
 - [ ] Test on mobile
 - [ ] i18n

aperisolve/analyzers/image_resize.py

@@ -0,0 +1,190 @@
+"""Image size bruteforcer for common PNG sizes."""
+
+import zlib
+import shutil
+from pathlib import Path
+from .utils import update_data
+
+# Full list of expected sizes
+EXPECTED_SIZES = [
+    # -------------------------
+    # ICONS (Square)
+    # -------------------------
+    (16, 16), (20, 20), (24, 24), (28, 28),
+    (32, 32), (48, 48), (64, 64), (72, 72),
+    (96, 96), (128, 128), (192, 192), (256, 256),
+    (384, 384), (512, 512), (768, 768), (1024, 1024),
+    (1536, 1536), (2048, 2048), (4096, 4096),
+
+    # -------------------------
+    # 1:1 Square (General)
+    # -------------------------
+    (300, 300), (500, 500), (800, 800), (1000, 1000),
+    (1500, 1500), (2000, 2000), (2500, 2500), (3000, 3000),
+
+    # -------------------------
+    # 4:3 Aspect (Classic Screens)
+    # -------------------------
+    (320, 240), (640, 480), (800, 600), (960, 720),
+    (1024, 768), (1280, 960), (1600, 1200), (2048, 1536),
+    (2560, 1920), (3200, 2400), (4096, 3072),
+
+    # -------------------------
+    # 3:2 Aspect (Photography)
+    # -------------------------
+    (600, 400), (900, 600), (1200, 800), (1500, 1000),
+    (1800, 1200), (2400, 1600), (3000, 2000), (3600, 2400),
+    (4500, 3000), (6000, 4000),
+
+    # -------------------------
+    # 16:9 Aspect (Video / Web)
+    # -------------------------
+    (426, 240), (640, 360), (854, 480), (960, 540),
+    (1280, 720), (1366, 768), (1600, 900), (1920, 1080),
+    (2560, 1440), (3200, 1800), (3440, 1935), (3840, 2160),
+    (5120, 2880), (7680, 4320), (10240, 5760),
+
+    # -------------------------
+    # 16:10 Aspect (Laptops)
+    # -------------------------
+    (1280, 800), (1440, 900), (1680, 1050),
+    (1920, 1200), (2560, 1600), (2880, 1800),
+    (3840, 2400), (5120, 3200),
+
+    # -------------------------
+    # Mobile Portrait (9:16)
+    # -------------------------
+    (720, 1280), (1080, 1920), (1440, 2560),
+    (2160, 3840), (1440, 2960), (1080, 2400),
+    (1170, 2532), (1284, 2778), (1290, 2796),
+
+    # -------------------------
+    # Social Media Sizes
+    # -------------------------
+    # Instagram
+    (1080, 1080), (1080, 1350), (1080, 1920),
+
+    # Facebook
+    (1200, 628), (1200, 1200),
+
+    # Twitter/X
+    (1200, 675), (1500, 500),
+
+    # YouTube Thumbnails
+    (1280, 720), (1920, 1080),
+
+    # -------------------------
+    # Banners / Headers
+    # -------------------------
+    (1600, 500), (1920, 500), (2560, 700),
+    (3000, 1000), (3840, 1200),
+
+    # -------------------------
+    # Print-like Digital Sizes
+    # -------------------------
+    (2550, 3300),  # Letter @ 300 DPI
+    (2480, 3508),  # A4 @ 300 DPI
+    (3508, 4961),  # A3 @ 300 DPI
+    (4961, 7016),  # A2 @ 300 DPI
+    (7016, 9933),  # A1 @ 300 DPI
+
+]
+
+def calc_checksum(header_chunk, width_bytes, height_bytes):
+    """
+    Calculates the CRC32 of the IHDR chunk with new dimensions.
+    header_chunk: The full IHDR chunk (Type + Data).
+    """
+    # Reconstruct IHDR: [Type(4)] + [New Width(4)] + [New Height(4)] + [Rest of Data(5)]
+    new_header = header_chunk[:4] + width_bytes + height_bytes + header_chunk[12:]
+
+    # Calculate CRC and return as 4 bytes (Big Endian)
+    return bytearray((zlib.crc32(new_header) & 0xffffffff).to_bytes(4, byteorder='big'))
+
+def analyze_image_resize(input_img: Path, output_dir: Path) -> None:
+    """
+    Analyze an image submission using python-based resize bruteforce.
+    Attempts to recover PNGs with modified resolutions but valid CRCs.
+    """
+
+    # 1. Setup Paths
+    input_img = Path(input_img)
+    output_dir = Path(output_dir)
+
+    # 3. Initialize Logs
+    logs = []
+    recovered_image = None
+
+    try:
+        with input_img.open("rb") as image:
+            f = image.read()
+
+        b = bytearray(f)
+
+        # Find IHDR start
+        IHDR = b.find(b'\x49\x48\x44\x52')
+        if IHDR == -1:
+            logs.append("Failure: PNG header (IHDR) not found.")
+            update_data(output_dir, {"image_resize": {"status": "error", "error": "PNG header not found."}})
+            return
+
+        # Calculate Chunk Length (The 4 bytes BEFORE IHDR tag)
+        chunk_length = int.from_bytes((b[IHDR- 4: IHDR]), byteorder="big") + 4
+
+        # Extract Target CRC (The 4 bytes AFTER the chunk data)
+        target_crc = b[IHDR + chunk_length:IHDR + chunk_length + 4]
+
+        # Isolate the header chunk (Type + Data)
+        header_chunk = b[IHDR:IHDR + chunk_length]
+
+        logs.append(f"Target CRC found: 0x{target_crc.hex()}")
+
+        match_found = False
+
+        # Brute-force Loop
+        for size in EXPECTED_SIZES:
+            width, height = size
+
+            # Convert dimensions to 4-byte Big Endian arrays
+            width_bytes = bytearray(width.to_bytes(4, byteorder='big'))
+            height_bytes = bytearray(height.to_bytes(4, byteorder='big'))
+
+            # Check if this size matches the file's CRC
+            if target_crc == calc_checksum(header_chunk, width_bytes, height_bytes):
+                match_found = True
+                logs.append(f"Success: Match found! Dimensions: {width}x{height}")
+
+                # Create Output Filename
+                img_name = f"recovered_{width}x{height}.png"
+
+                # Create parent directories if they don't exist
+                output_dir.mkdir(parents=True, exist_ok=True)
+                output_path = output_dir / img_name
+
+                # Splicing: [Start...IHDR+4] + [W] + [H] + [IHDR+12...End]
+                full_png_data = b[:IHDR+4] + width_bytes + height_bytes + b[IHDR+12:]
+
+                # Write the recovered file to disk
+                with output_path.open("wb") as out_f:
+                    out_f.write(full_png_data)
+
+                recovered_image = Path(output_dir.name) / img_name
+                break # Stop looking after finding the match
+
+        if not match_found:
+            logs.append("Failure: No matching dimensions found.")
+
+        # 4. Final Data Update
+        output_data = {
+            "image_resize": {  # Key name must match your module name in AperiSolve
+                "status": "ok",
+                "output": logs
+            }
+        }
+        if recovered_image:
+            output_data["image_resize"]["image"] = "/image/" + str(recovered_image)
+        update_data(output_dir, output_data)
+
+    except Exception as e:
+        update_data(output_dir, {"image_resize": {"status": "error", "error": str(e)}})
+    return None

aperisolve/config.py

@@ -3,6 +3,6 @@
 from pathlib import Path
 
 IMAGE_EXTENSIONS = [".png", ".jpg", ".jpeg", ".gif", ".bmp", ".webp", ".tiff"]
-WORKER_FILES = ["binwalk", "foremost", "steghide", "zsteg"]
+WORKER_FILES = ["binwalk", "foremost", "steghide", "zsteg", "image_resize"]
 
 RESULT_FOLDER = Path(__file__).parent.resolve() / "results"

aperisolve/static/js/aperisolve.js

@@ -8,6 +8,7 @@ const TOOL_ORDER = [
   "steghide",
   "zsteg",
   "strings",
+  "image_resize",
 ];
 
 function escapeHtml(text) {
@@ -248,7 +249,7 @@ function parseResult(result) {
     analyzer.className = `analyzer a-${escapeHtml(tool)}`;
     resultDiv.appendChild(analyzer);
 
-    analyzer.innerHTML += `<h2>${capitalize(tool)}</h2>`;
+    analyzer.innerHTML += `<h2>${capitalize(tool.replace("_"," "))}</h2>`;
 
     if (result[tool]["status"] === "ok") {
       if ("images" in result[tool]) {
@@ -270,8 +271,17 @@ function parseResult(result) {
           }
         }
       }
+
+      if ("image" in result[tool]) {
+        // Parse image output
+        analyzer.innerHTML += `<div class='results_img'><img src='${escapeHtml(
+          result[tool]["image"]
+        )}'/></div>`;
+      }
+
       // Parse text output
   
+
       if (typeof result[tool]["output"] === "string") {
         analyzer.innerHTML += `<pre>${escapeHtml(
           result[tool]["output"]

aperisolve/templates/faq.html

@@ -6,8 +6,8 @@
   <div>
     <div>
       This cheatsheet is intended to guide CTF players in their research. This cheatsheet is not representative of
-      modern steganography/seganalysis techniques, and its content does not match with the creation of an interesting
+      modern steganography/steganalysis techniques, and its content does not match with the creation of an interesting
-      challenges 😉.
+      challenge 😉.
     </div>
   </div>
   <h2>Check file type / metadata</h2>
@@ -48,7 +48,7 @@
       <ul class="fa-ul">
         <li>Verify the checksums of the file. These are usually CRC32, some tools like <a
             href='http://www.libpng.org/pub/png/apps/pngcheck.html' target='_blank' class='highlight'>PngCheck</a> or <a
-            href='https://github.com/sherlly/PCRT' target='_blank' class='highlight'>PCRT</a> are usefull to verify and
+            href='https://github.com/sherlly/PCRT' target='_blank' class='highlight'>PCRT</a> are useful to verify and
           correct these checksums.</li>
       </ul>
       <div class="command">

aperisolve/workers.py

@@ -13,6 +13,7 @@ from .analyzers.steghide import analyze_steghide
 from .analyzers.strings import analyze_strings
 from .analyzers.zsteg import analyze_zsteg
 from .analyzers.pngcheck import analyze_pngcheck
+from .analyzers.image_resize import analyze_image_resize
 from .app import app, db
 from .config import RESULT_FOLDER
 from .models import Image, Submission
@@ -53,6 +54,7 @@ def analyze_image(submission_hash: str) -> None:
                 (analyze_pngcheck, img_path, result_path),
                 (analyze_steghide, img_path, result_path, submission.password),
                 (analyze_zsteg, img_path, result_path),
+                (analyze_image_resize, img_path, result_path),
             ]
 
             # Deep analysis only