make it work

headers-ii/chall.yaml

@@ -10,7 +10,7 @@ hints:
   - There's no file extension, but what other way could I figure out what type of file it is?
   - Someone told me there might be multiple files (even though they only sent one)
 files:
-  - src: funnyfile
+  - src: funfile
 authors:
   - Mudasir
 visible: true

headers-ii/generator.py

@@ -1,25 +1,25 @@
 '''
 @author Mudasir
 
-some util functions to generate flag and copy it to video
+some util function(s) to generate flag and copy it to video
 '''
 
 from PIL import Image, ImageDraw, ImageFont
+import io
 
 FLAG = 'camp{wH@7s_an_3xTr@_f!l3_aNYw@y$_r3dhi8ib28bf}'
 
 def generate_flag():
+    final_bytes = io.BytesIO()
     img = Image.new('RGB', (600, 100), color = (0, 0, 0))
     d = ImageDraw.Draw(img)
     fnt = ImageFont.truetype('arial.ttf', 20)
     d.text((40,30), FLAG, font=fnt, fill=(255,255,255))
-    img.save('flag.png')
+    # img.save('flag.png')
+    img.save(final_bytes, format='PNG')
+    final_bytes = final_bytes.getvalue()
 
-def copy_img_to_video():
-    with open('flag.png', 'rb') as f:
-        flag = f.read()
-        with open('funnyfile', '+ab') as f2:
-            f2.write(flag)
+    with open('funfile', '+ab') as f2:
+        f2.write(final_bytes)
 
-generate_flag()
-copy_img_to_video()
+generate_flag()

headers-ii/solve/solve.md

@@ -0,0 +1,8 @@
+# File headers
+
+Hint in the name: headers. Despite the lack of a file extension we can check the file header / magic number See: (https://en.wikipedia.org/wiki/List_of_file_signatures)[https://en.wikipedia.org/wiki/List_of_file_signatures] for more information on file headers.
+
+Opening the file in a text and/or hex editor shows us that we have an mp4 file. However, the video does not open in a media player. Further examination would show that the file has a PNG glued on to it. Separating the files shows us that the video is a red herring, and the PNG has the flag.
+
+
+Script is included at (solve.py)[solve.py], run in the same directory as the file. It creates (solve.png)[solve.png] with the flag.

headers-ii/solve/solve.py

@@ -0,0 +1,6 @@
+with open('funfile','rb') as f:
+    data = f.read().split(b"\x89PNG")
+    with open('solve.png','wb') as f2:
+        f2.write(b"\x89PNG")
+        f2.write(data[1])
+        print('Done')