Monitor regex (monitor_re) has a minor regex bug

[beasteers]

Version: redis-py: 3.5.3

Platform: Python 3.10.11 mac

Description:

The redis monitor command parsing can break for certain messages (has been happening with byte strings that contain the substring "] ").

Basically, the fix is to make the client_info regex non-greedy:

# original
monitor_re = re.compile(r"\[(\d+) (.*)\] (.*)")
# fix:
monitor_re = re.compile(r"\[(\d+) (.*?)\] (.*)")

You can test here: https://regexr.com/

An example that works

[0 172.18.0.4:36030] "XADD" "default:main" "MAXLEN" "~" "1000" "*" "d" "asdf"

An example that breaks the original regex

[0 172.18.0.4:36030] "XADD" "default:main" "MAXLEN" "~" "1000" "*" "d" "] "

The assumption being that the client_info would never contain "] " which seems to be the case from what I can tell.

[beasteers]

And just to document this somewhere: If you need to parse out byte strings from (e.g.) XADD commands, this is how you can restore the proper encoding. I'm not 100% certain there aren't failure cases - If anyone can identify any (or has a systematic way of validating) let me know.

The key is !! codecs.escape_decode(x) !!

import codecs
from redis.client import Monitor as Monitor_

class Monitor(Monitor_):  # use: Monitor(r.connection_pool)

    monitor_re = re.compile(rb"\[(\d+) (.*?)\] (.*)")
    command_re = re.compile(rb'"(.*?(?<!\\))"')

    def next_command(self):
        """Parse the response from a monitor command"""
        # https://github.com/redis/redis/blob/4031a187321be26fc96c044fec3ee759841e8379/src/replication.c#L576
        response = self.connection.read_response(disable_decoding=True)
        command_time, command_data = response.split(b" ", 1)
        db_id, client_info, raw_command = self.monitor_re.match(command_data).groups()
        command_parts = self.command_re.findall(raw_command)
        command_parts = [codecs.escape_decode(x)[0] for x in command_parts]

        client_info = client_info.decode()
        if client_info == "lua":
            client_address = client_type = "lua"
            client_port = ""
        else:
            client_address, client_port = client_info.rsplit(":", 1)  # ipv6 has colons
            client_type = "unix" if client_info.startswith("unix") else "tcp"

        return {
            "time": float(command_time.decode()),
            "db": int(db_id.decode()),
            "client_address": client_address,
            "client_port": client_port,
            "client_type": client_type,
            # return a list of bytes with mixed encodings (utf-8 for everything unless you're storing things like jpegs)
            "args": command_parts,  
        }