[python] support cromfs extraction

python/matcher/cromfs.py

@@ -1,6 +1,10 @@
 import os
 import io
 
+from pathlib import Path
+
+import lzf
+
 from .matcher import SignatureMatcher, Match
 
 class CromFS(SignatureMatcher):
@@ -50,7 +54,19 @@ class CromFS(SignatureMatcher):
 
         return len(self.matches) != 0
 
-    def view(self, match):
+    def view(self, match, root_folder):
+        def extract(path, is_folder):
+            if root_folder is None:
+                return
+            p = root_folder / ('_' + hex(match.offset))
+            p.mkdir(exist_ok=True)
+            p = p / path
+            if is_folder:
+                p.mkdir(exist_ok=True)
+            else:
+                p.touch(exist_ok=True)
+                return open(p, 'wb')
+
         as_num = lambda x: int.from_bytes(x, 'little')
 
         root = match.data['root']
@@ -77,6 +93,31 @@ class CromFS(SignatureMatcher):
                 buffer.seek(old, os.SEEK_SET)
             return s.decode()
 
+        def read_file_contents(buffer, at=None, recover=False, file=None, total_size=0):
+            old = buffer.tell()
+            if at:
+                buffer.seek(at, os.SEEK_SET)
+
+            file_contents = b''
+            while total_size > 0:
+                magic = buffer.read(2)
+                typ = as_num(buffer.read(1))
+                if typ == 0:
+                    len = as_num(buffer.read(1)) << 8 | as_num(buffer.read(1))
+                    uncompress = buffer.read(len)
+                    file_contents += uncompress
+                    total_size -= len
+                if typ == 1:
+                    clen = as_num(buffer.read(1)) << 8 | as_num(buffer.read(1))
+                    ulen = as_num(buffer.read(1)) << 8 | as_num(buffer.read(1))
+                    compressed = buffer.read(clen)
+                    file_contents += lzf.decompress(compressed, ulen)
+                    total_size -= ulen
+            if file:
+                file.write(file_contents)
+            if recover:
+                buffer.seek(old, os.SEEK_SET)
+
         def read_nodes(buffer, current):
             mode = as_num(buffer.read(2))
             buffer.read(2)
@@ -89,23 +130,24 @@ class CromFS(SignatureMatcher):
             is_reg = lambda mode: mode & (8 << 12) != 0
             is_link = lambda mode: mode & (10 << 12) != 0
 
-            path = current + '/' + name
-            print(path)
+            path = current / name
 
             if is_link(mode):
                 pass
             if is_dir(mode):
+                extract(path, True)
                 # traverse the directory children
                 buffer.seek(extra, os.SEEK_SET)
-                read_nodes(buffer, current + '/' + name)
-            if is_reg(mode):
-                for block in range(extra):
-                    # decrypt each block
-                    pass
+                read_nodes(buffer, path)
+            if is_reg(mode) and name != '.' and name != '..':
+                f = extract(path, False)
+                read_file_contents(buffer, at=extra, recover=True, total_size=size, file=f)
+                if f:
+                    f.close()
 
             # traverse its peer
             if peer != 0:
                 buffer.seek(peer, os.SEEK_SET)
                 read_nodes(buffer, current)
 
-        read_nodes(region, '')
+        read_nodes(region, Path(''))

python/matcher/matcher.py

@@ -27,5 +27,5 @@ class SignatureMatcher:
     def is_valid(self):
         return False
 
-    def view(self, match):
+    def view(self, match, root_folder=None):
         pass

python/matcher/romfs.py

@@ -27,8 +27,7 @@ class RomFS(SignatureMatcher):
 
         return len(self.matches) != 0
 
-    def view(self, match):
-
+    def view(self, match, root_folder):
         start = match.offset
         length = match.length
         raw = io.BytesIO(self.file[start:start+length])