First, primitive version of checksum calc tool

This is a (seemingly) working re-implementation of how to calculate the
expected checksum for a Fritz!Box configuration file in Python.

fbchecksum

@@ -0,0 +1,107 @@
+#!/usr/bin/python
+
+import binascii
+import sys, re
+
+print "CRC32 test: %08X" % (binascii.crc32("some\n bullshit\r test\0\0 to compare to PHP equivalent") & 0xffffffff);
+print "unhexlify test: %s (<- should read \"Hallo\")" % binascii.unhexlify("48616C6c6F00");
+print "stripcslashes test: %s" % re.sub("\\\\\\\\", "\\\\", "foo\\\\bar\\blupp")
+
+# TODO credits
+# TODO windows line endings?
+
+# global pre-compiled regex objects for later matching
+# matches a key-value pair found on the top of the config
+# TODO do we need to allow optional whitespaces before the end of the line?
+var_val_pair_regex = re.compile("^([\w]+)=([\S]+)$");
+
+# matches the begin marker of a config file name
+cfg_file_start_regex = re.compile("^\*{4} CFGFILE:([\S]+)$")
+
+bin_file_start_regex = re.compile("^\*{4} BINFILE:([\S]+)$")
+
+any_file_end_regex = re.compile("^\*{4} END OF FILE \*{4}$")
+
+def read_config_file(filename, lines):
+    #print "amount of lines: %i" % len(lines)
+    #for line in lines:
+    #    print line,
+    #sys.exit(2)
+    result = str(filename) + '\0'
+    for line in lines[:-1]:
+        result += re.sub("\\\\\\\\", "\\\\", line) # TODO stripcslashes
+    if lines[-1] != str("\n"):
+        # TODO does the fritzbox also accept configs with no such newline?
+        print "Whoops, I was expecting an empty line at the end of file \"%s\"!" % filename
+        sys.exit(2)
+    return result
+
+def read_binary_file(filename, lines):
+    result = str(filename) + '\0'
+    for line in lines:
+        result += binascii.unhexlify(line.strip())
+    return result
+
+def main():
+    config_lines = list() # input (list of lines, line endings included)
+    checksum_material = str() # accumulated data for CRC32 calculation
+
+    if(len(sys.argv) < 2):
+        print "Need argument (file to inspect)!"
+        sys.exit(-1)
+
+    filename = sys.argv[1]
+
+    try:
+        with file(filename) as f:
+            config_lines = f.readlines()
+    except Exception as e:
+        print "ERROR: File \"%s\" could not be read." % filename
+        if hasattr(e, "strerror"): print "ERROR: %s" % e.strerror
+        sys.exit(-1);
+
+    line_index = int(0)
+    while line_index < len(config_lines):
+        #print "processing line: %i" % (line_index + 1)
+        line = config_lines[line_index]
+
+        # determine the type of this (and maybe the following) input line(s)
+        match = re.match(var_val_pair_regex, line);
+        if match:
+            checksum_material += match.group(1) + match.group(2) + '\0';
+            #print "%s" % checksum_material
+            line_index += 1
+            continue
+
+        match = re.match(cfg_file_start_regex, line);
+        if match:
+            file_start = line_index + 1
+            file_end = file_start + 1
+            while not re.match(any_file_end_regex, config_lines[file_end]):
+                file_end += 1
+            checksum_material += read_config_file(match.group(1), config_lines[file_start:file_end])
+            #print "%s" % checksum_material,
+            #sys.exit(2)
+            line_index = file_end + 1
+            continue
+
+        match = re.match(bin_file_start_regex, line);
+        if match:
+            file_start = line_index + 1
+            file_end = file_start + 1
+            while not re.match(any_file_end_regex, config_lines[file_end]):
+                file_end += 1
+            checksum_material += read_binary_file(match.group(1), config_lines[file_start:file_end])
+            line_index = file_end + 1
+            continue
+
+        # line is ignored
+        line_index += 1
+
+    #with open("python-out.bin", "w") as f:
+    #    f.write(checksum_material)
+
+    print "presumably proper checksum: %08X" % (binascii.crc32(checksum_material) & 0xffffffff)
+
+if __name__ == '__main__':
+    main()