Date: Mon, 04 Sep 2023 18:00:37 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-arm@FreeBSD.org Subject: [Bug 273566] stray characters contaminate serial console Message-ID: <bug-273566-7@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D273566 Bug ID: 273566 Summary: stray characters contaminate serial console Product: Base System Version: CURRENT Hardware: arm OS: Any Status: New Severity: Affects Only Me Priority: --- Component: arm Assignee: freebsd-arm@FreeBSD.org Reporter: fbsd@www.zefox.net >From time to time serial console connections on raspberry Pi (2, 3 and 4) systems allow stray characters to enter serial console commands. Since the console is often used by root, this seems potentially insecure.=20 The setup consists of a pair of Pi's. One holds a usb-serial adapter, with the serial end connected to a second Pi's console uart. Connection=20 is established by ssh into the first Pi, starting tip or cu, and then logging into the second Pi into the usual way. Often, login is to root. Often, the ssh connection to the first Pi drops spontaneously. It can be re-established by repeating the connection procedure, if the original shell running on the second Pi's serial console is still running the old session remains up and prior commands can be run from history. When that is done, sometimes the apparent "last words" to the second Pi appear to be things that were never intentionally entered before the=20 disconnect. Here's one example, in this case the terminal session is running on a Pi4 running RasPiOS, the ssh connection is to a Pi2 running FreeBSD 14.0-ALPHA4 armv7 1400097 (GENERIC) #1, the Pi running the serial console is running 15-current:client_loop: send disconnect: Broken pipe bob@raspberrypi:~ $ ssh 192.168.1.13 Password for bob@generic: Last login: Mon Sep 4 08:14:21 2023 from 192.168.1.10 FreeBSD 14.0-ALPHA4 armv7 1400097 (GENERIC) #1 stable/14-n265029-d6fec2dacf= 80: Mon Sep 4 02:12:35 PDT 2023 Welcome to FreeBSD! Release Notes, Errata: https://www.FreeBSD.org/releases/ Security Advisories: https://www.FreeBSD.org/security/ FreeBSD Handbook: https://www.FreeBSD.org/handbook/ FreeBSD FAQ: https://www.FreeBSD.org/faq/ Questions List: https://www.FreeBSD.org/lists/questions/ FreeBSD Forums: https://forums.FreeBSD.org/ Documents installed with the system are in the /usr/local/share/doc/freebsd/ directory, or can be installed later with: pkg install en-freebsd-doc For other languages, replace "en" with a language code like de or fr. Show the version of FreeBSD installed: freebsd-version ; uname -a Please include that output and any error messages when posting questions. Introduction to manual pages: man man FreeBSD directory layout: man hier To change this login announcement, see motd(5). To see the last 10 lines of a long file, use "tail filename". To see the first 10 lines, use "head filename". To see new lines as they're appended to a file, use "tail -f filename". -- Dru <genesis@istar.ca> bob@generic:~ % su Password: # tip ucom Stale lock on cuaU0 PID=3D1181... overriding. connected Y\HHMHLN\247\261=CD=81\315m\335u=E9=81=95\311\351=CD=A1}}=C2=A5=D1=A5=D1=A5= =C2=BD YHHMHLN=EF=BF=BD=EF=BF=BD=CD=81=EF=BF=BDm=EF=BF=BDu=E9=81=95=EF=BF=BD=EF=BF= =BD=CD=A1}}=EF=BF=BD=D1=A5=D1=A5=EF=BF=BD: Command not found. bob@pelorus:/usr/src % =C2=BD=C2=B9=C2=B9=D1=A5=C2=BD=C2=B9=C2=B1=C2=BD=CD= =95=C3=A5=C9=95=C2=B5=C2=BD=D1=95=C2=A1=C2=BD=C3=8D=C3=915)5)5)=C3=BF Too many )'s. bob@pelorus:/usr/src If one types up-arrow to recall history, the first few old "commands" are rubbish, though they are not un-displayable as would be expected from line noise (the copy-paste from FreeBSD to RasPiOS is misleading). In this example an FTDI-232 was in use, but PL2303 has behaved similarly. The origin of the disconnect is unclear. I think it's a problem with ssh between the RasPiOS terminal and the Pi holding the USB-serial=20 adapter, but don't know how to tell for sure. It seems to be load-related, with a busy FreeBSD Pi more inclined to drop connections even if the connection itself is entirely idle.=20 FWIW, stable/12 does not display this behavior, with ssh-usb-serial-console connections staying up for days or weeks. --=20 You are receiving this mail because: You are the assignee for the bug.=
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