From nobody Sun May 21 18:40:47 2023 X-Original-To: freebsd-current@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4QPTsx22dwz4CKf2 for ; Sun, 21 May 2023 18:40:37 +0000 (UTC) (envelope-from fbsd@www.zefox.net) Received: from www.zefox.net (www.zefox.net [50.1.20.27]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "www.zefox.com", Issuer "www.zefox.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4QPTsw4mlDz3s7p for ; Sun, 21 May 2023 18:40:36 +0000 (UTC) (envelope-from fbsd@www.zefox.net) Authentication-Results: mx1.freebsd.org; none Received: from www.zefox.net (localhost [127.0.0.1]) by www.zefox.net (8.17.1/8.15.2) with ESMTPS id 34LIel9J004674 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Sun, 21 May 2023 11:40:47 -0700 (PDT) (envelope-from fbsd@www.zefox.net) Received: (from fbsd@localhost) by www.zefox.net (8.17.1/8.15.2/Submit) id 34LIelog004673; Sun, 21 May 2023 11:40:47 -0700 (PDT) (envelope-from fbsd) Date: Sun, 21 May 2023 11:40:47 -0700 From: bob prohaska To: freebsd-current@freebsd.org Cc: bob prohaska Subject: Re: Stray characters in command history Message-ID: References: List-Id: Discussions about the use of FreeBSD-current List-Archive: https://lists.freebsd.org/archives/freebsd-current List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-current@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 4QPTsw4mlDz3s7p X-Spamd-Bar: ---- X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:7065, ipnet:50.1.16.0/20, country:US] X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-ThisMailContainsUnwantedMimeParts: N Here is another example, perhaps a bit clearer. The ssh connection to the first Pi3 in the chain had dropped, so it was re-establishing via a regular user login, then su was invoked and tip run: ..... To change this login announcement, see motd(5). Want to go the directory you were just in? Type "cd -" bob@pelorus:~ % su Password: # tip ucom Stale lock on cuaU0 PID=2487... overriding. connected osed by r31 www s <<<< This appeared spontaneously, then I hit return. osed: Command not found. <<<<< I didn't type anything. bob@www:/usr/src % <<<<< The shell prompt on the 2nd Pi3's serial console. .... Clearly nothing to do with sshd, might it simply be a misdirected echo of console output generated by a (dead or broken) tip connection? The first example looked possibly malicious, this does not.... Thanks for reading, bob prohaska On Sun, May 21, 2023 at 06:49:33AM -0700, bob prohaska wrote: > Lately I've been playing with buildworld on a Pi3 running -current. The same machine > acts as a terminal server for a second Pi3 also running -current in my "cluster". > I ssh into the first Pi3, su to root and run tip to pick up a serial connection to > the second Pi's console. Both machines are within a week of up-to-date. > > While building world on the first Pi3 the ssh connection frequently drops and must be > re-established. If there was a shell running on the serial console of the second > Pi3 it typically keeps running and when the tip session is restarted disgorges a > stream of accumulated console message. > > This morning the same thing happened, but I noticed something odd. The stream of > messages (all login failure announcements from ssh) ended with > > .... > May 21 06:15:00 www sshd[33562]: error: Fssh_kex_exchange_identification: banner line contains invalid characters > *+May 21 06:15:19 www sshd[33565]: error: Fssh_kex_exchange_identification: Connection closed by remote host > May 21 06:15:33 www sshd[33613]: error: Protocol major versions differ: 2 vs. 1 > > At that point I hit carriage return and got > *+: No match. > > I did not type the *+ so it looks like the characters were somehow introduced elsewhere, > possibly from the ssh failure message. How they got into the command stream is unclear. > > This strikes me as undesirable at best and possibly much worse. The shell reporting > the "no match" was a regular user shell, but if I'd been su'd to root it appears that > the unmatched characters would be seen by the root shell as input. > > This more-or-less fits with the pattern seen earlier with reboots observed via serial > console halting on un-typed keystrokes. Those halts were attributed to electrical noise > on the serial line, but this looks like something injected via part of the network > login process. Reboot pauses have been an ongoing phenomenon for months, this is the > first time I've noticed the "invalid characters" message from ssh on the console. > > Thanks for reading, apologies if I'm being a worrywart. > > bob prohaska > > >