Crash when editing multipart/formdata

[psacawa]

Problem Description

I received the following message when editng a field of a multipart/form-data request body, which is for for file uploads.

Traceback (most recent call last):
  File "mitmproxy/master.py", line 54, in run_loop
  File "urwid/main_loop.py", line 287, in run
  File "urwid/main_loop.py", line 385, in _run
  File "urwid/main_loop.py", line 1494, in run
  File "urwid/compat.py", line 58, in reraise
  File "asyncio/events.py", line 80, in _run
  File "urwid/raw_display.py", line 416, in <lambda>
  File "urwid/raw_display.py", line 515, in parse_input
  File "urwid/main_loop.py", line 412, in _update
  File "urwid/main_loop.py", line 513, in process_input' (No such file or directory)
  File "mitmproxy/tools/console/window.py", line 318, in keypress
  File "mitmproxy/tools/console/keymap.py", line 145, in handle
  File "mitmproxy/tools/console/commandexecutor.py", line 18, in __call__
  File "mitmproxy/command.py", line 273, in execute
  File "mitmproxy/command.py", line 259, in call_strings
  File "mitmproxy/command.py", line 129, in call
  File "mitmproxy/command.py", line 303, in wrapper
  File "mitmproxy/tools/console/consoleaddons.py", line 328, in view_pop
  File "blinker/base.py", line 266, in send
  File "blinker/base.py", line 266, in <listcomp>
  File "mitmproxy/tools/console/window.py", line 247, in pop
  File "mitmproxy/tools/console/window.py", line 114, in pop
  File "mitmproxy/tools/console/window.py", line 126, in call
  File "mitmproxy/tools/console/grideditor/base.py", line 462, in layout_popping
  File "mitmproxy/tools/console/grideditor/base.py", line 440, in call
  File "mitmproxy/tools/console/grideditor/base.py", line 313, in layout_popping
  File "mitmproxy/tools/console/grideditor/base.py", line 455, in set_data_update
  File "mitmproxy/tools/console/grideditor/editors.py", line 68, in set_data
  File "mitmproxy/http.py", line 998, in multipart_form
  File "mitmproxy/http.py", line 979, in _set_multipart_form
  File "mitmproxy/net/http/multipart.py", line 34, in encode
  File "re.py", line 201, in search
TypeError: cannot use a bytes pattern on a string-like object

mitmproxy has crashed!
Please lodge a bug report at:
        https://github.com/mitmproxy/mitmproxy/issues

Recording:

You can see in the recording that the Grideditor fields display the stringified bytes objects str(b'asdf'). I have been able to recreate the bug editing all fields of the multipart/form-data, not just the one for the file itself. This bug has nothing to do with the external editor, as I initially wrote.

Another issue is the the GridEditor for multipart/form-data is very slow for even medium-sized files. When dealing with a 197Kb file, it becomes unresponsive.

Steps to reproduce the behavior:

1. Send a post request with a file upload encoded as multipart/form-data
2. Edit a field of the request with the multipart/form-data GridEditor view directly in mitmproxy
3. Return from the external editor by pressing Q.

System Information

Replicated on:

Mitmproxy: 7.0.0 binary
Python:    3.9.5
OpenSSL:   OpenSSL 1.1.1k  25 Mar 2021
Platform:  Linux-5.13.0-28-generic-x86_64-with-glibc2.31

Mitmproxy: 7.0.4 binary
Python:    3.9.7
OpenSSL:   OpenSSL 1.1.1l  24 Aug 2021
Platform:  Linux-5.13.0-28-generic-x86_64-with-glibc2.31

[ditek]

I can confirm that this is still an issue on v8.0.0.