'net/ftp': Uncontrolled Resource Consumption (Memory/CPU)

Current `TIME_PARSER` implementation allows attackers to cause a denial of service (memory consumption) via a large integer value for the `fractions` property. The problem code: ```ruby TIME_PARSER = ->(value, local = false) { unless /\A(?<year>\d{4})(?<month>\d{2})(?<day>\d{2}) (?<hour>\d{2})(?<min>\d{2})(?<sec>\d{2}) (?:\.(?<fractions>\d+))?/x =~ value raise FTPProtoError, "invalid time-val: #{value}" end usec = fractions.to_i * 10 ** (6 - fractions.to_s.size) Time.public_send(local ? :local : :utc, year, month, day, hour, min, sec, usec) } ``` # PoC For example, a ran a malicious server that returns `"213 20371231000000.".("9"x999999999)."\r\n"` for commands that use `TIME_PARSER` (`mlst`, `mlsd`, `mdtm`, etc). Also, such a response can be spoofed if the attacker is on the same network as the victim. Here is the result of running of the process for an hour and a half: ``` PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 18644 me 20 0 27.9g 12.3g 64 D 100.0 84.0 89:17.45 ruby ``` The process kept the CPU load around 90-100% all the time, and slowly but surely, devour all the available memory. ## Impact Denial of Service.