Roundtable January 2014

roundtable@muug.ca

13 participants
19 discussions

xargs with no command
by Trevor Cordes 18 Jan '14

18 Jan '14

As per Tuesday's meeting RTFM: ibm.com gave me the first hint: If no command template appears on the command line, xargs uses echo by default. Which then let me find it in Linux's man page: ... and executes the command (default is /bin/echo) ... So they were basically using xargs as a newline-eater to combine all the lines of the iteration into one.

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wireshark warning
by Trevor Cordes 18 Jan '14

18 Jan '14

Didn't have a chance to bring it up at the meeting, but I feel it's important to add that wireshark is probably the most frequently security-patched FOSS out there. I watch the security feed from Fedora and the package I see sec-updated most often is wireshark, probably followed by PHPMyAdmin. It's quite astonishing how miserably insecure wireshark is. (Hmm, too bad there doesn't seem to be a page or chart ranking FOSS by CVE count, unless someone else can find one.) So, if you use wireshark, do your package updates frequently and/or before each invocation of wireshark. This is a great argument for not using wireshark on Windows, as there is not yum/apt-get for it, AFAIK, meaning you'd be on your own to check for and install updates.

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Fwd: OpenNTPD and NTP reflection attacks
by Adam Thompson 17 Jan '14

17 Jan '14

Along the lines of a question Alan raised at the meeting this week... apparently NTP DDoS attack are a thing now. :-( -Adam -------- Original Message -------- Subject: OpenNTPD and NTP reflection attacks Date: Wed, 15 Jan 2014 13:36:12 -0600 From: Nicolai <nicolai-omisc(a)chocolatine.org> To: misc(a)openbsd.org Hi everyone, I have a question about OpenNTPD now that NTP reflection attacks are in the news. OpenBSD produces and uses its own OpenNTPD, primarily written by Henning and made portable by Darren Tucker. The following website: http://openntpproject.org/ is an important effort to minimize reflection-related holes in NTP software. The given test command is not supported by OpenNTPD, suggesting no major amplification. And after reading the manual pages I don't think there's an alternative for getting OpenNTPD to generate a large amplification, though I could be wrong. So, is it correct to say that OpenNTPD is immune from generating large amplifications? (Recent articles on the subject mention 100x amplification factors!) Nicolai -- -Adam Thompson athompso(a)athompso.net Cell: +1 204 291-7950 Fax: +1 204 489-6515

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Firewall/Router hall of fame?
by John Lange 10 Jan '14

10 Jan '14

Should the Linksys WRT router/firewall go into the hall of fame? Undeniably, a lot of stuff Linksys made was crap but the WRT was not one of them. Even with it's default firmware it was a great firewall for home and small businesses. From the start it handled state tracking, NAT and packet reassembly properly making it one of the only devices around that would handle things like VOIP (credit most likely goes to it's Linux roots). Even today many so-called high-end firewalls (e.g. Sonicwall) still can not handle a fragmented UDP packets breaking SIP over UDP. According to this Wired article, the WRT is now back in a Gigabit version and Linksys is now publicly embracing the alternative firmwares that helped make it so popular. http://www.wired.com/gadgetlab/2014/01/linksys-wrt/ I still run a WRT with the "Tomato" firmware at home and I think this device will always have a place in my personal "hall of fame". Long live the WRT! Regards, John

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Video card?
by Kevin McGregor 08 Jan '14

08 Jan '14

It turns out I was a bit hasty in getting rid of all my video cards. At least, I think I got rid of them. I can't find any anywhere. :-) Does anyone have an old video card they don't need any more? It must be PCI or PCI-Express, and it's destined for a server (FreeNAS/FreeBSD or some such) so 2D/3D performance is not an issue. :-D I'd like to pick it up ASAP so I can continue to build my server. I can get a new card for ~$30, but I'd rather reduce, reuse, recycle. Thanks! Kevin

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Red Hat and CentOS joining forces
by Gilles Detillieux 08 Jan '14

08 Jan '14

Here's an interesting development I didn't see coming. Yesterday Red Hat and CentOS announced they were joining forces on this community-developed platform. http://www.zdnet.com/red-hat-incorporates-free-red-hat-clone-centos-7000024… http://community.redhat.com/centos-faq/ http://www.centos.org/ http://lists.centos.org/pipermail/centos-announce/2014-January/020100.html -- Gilles R. Detillieux E-mail: <grdetil(a)scrc.umanitoba.ca> Spinal Cord Research Centre WWW: http://www.scrc.umanitoba.ca/ Dept. Physiology, U. of Manitoba Winnipeg, MB R3E 0J9 (Canada)

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MUUG Meeting, Jan 14, 7:30pm -- Wireshark
by gedetil＠cs.umanitoba.ca 07 Jan '14

07 Jan '14

The Manitoba UNIX User Group (MUUG) will be holding its next monthly meeting on Tuesday, January 14. The meeting topic for this month is as follows: Wireshark Katherine Scrupa will be presenting Wireshark as the main topic. "Wireshark is the world's foremost network protocol analyzer. It lets you see what's happening on your network at a microscopic level. It is the de facto (and often de jure) standard across many industries and educational institutions." Kevin McGregor will be presenting an RTFM from the depths of CLI Magic; @climagic on Twitter. The group holds its general meetings at 7:30pm on the second Tuesday of every month from September to June. (There are no meetings in July and August.) Meetings are open to the general public; you don't have to be a MUUG member to attend. ***************************************************************** Please note our *NEW* meeting location for this month: Room 1L08, Lockhart Hall, University of Winnipeg, entrance on Ellice Ave. between Spence St. and Balmoral St. Parking is available on the surrounding streets and in the lots on nearby streets. Look for signage once you're at the building, or ask a security guard. ***************************************************************** For more information about MUUG, and its monthly meetings, check out their Web server: http://www.muug.mb.ca/ Help us promote this month's meeting, by putting this poster up on your workplace bulletin board or other suitable public message board: http://www.muug.mb.ca/meetings/MUUGmeeting.pdf -- Gilbert E. Detillieux E-mail: <gedetil(a)muug.mb.ca> Manitoba UNIX User Group Web: http://www.muug.mb.ca/ PO Box 130 St-Boniface Phone: (204)474-8161 Winnipeg MB CANADA R2H 3B4 Fax: (204)474-7609

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Korn shell script debugging
by Kevin McGregor 03 Jan '14

03 Jan '14

I've got a Korn shell script which I'm trying to debug with the aid of the "-x" switch, and it works for a while (i.e. as the script executes) until a function is called, then the shell stops displaying the commands as it executes. When the function returns, the commands are displayed again. How do I get it to display commands for the entire script? Kevin

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dhclient-exit-hooks
by Trevor Cordes 03 Jan '14

03 Jan '14

Yet another obscure problem. /etc/dhcp/dhclient-exit-hooks is supposed to run (if it exists) after dhclient has accepted a new DHCP IP from your ISP and done all its stuff. One would assume that would include setting the IP on your actual interface. I have a problem where a script that /etc/dhcp/dhclient-exit-hooks talks to (async through a named pipe, so after that it won't block) then does some stuff based on what /sbin/ip says the ip address is. I am expecting this to be the *new* ip address. But what it seems to be doing is still using the old ip, meaning (if I'm following my extremely complex scripts properly) /sbin/ip is still returning the old ip at that point. Does anyone have experience with dhclient, or its hooks? Is this even possible? Even weirder is my scripts wait an additional 10s before checking /sbin/ip so even if there was a short delay, it shouldn't still give me the old ip. The /sbin/ip command I use it: /sbin/ip -o -4 addr list <interface> then I parse out the address. Is there anything in the linux networking layer that would cause an IP bind to "not show up" for >10s? Secondly, debug testing this will be very difficult because our Shaw IP's change so infrequently. I suppose I could "trick it" by switching NICs and/or changing my NIC's MAC. I've never done that before, is that easy and safe?

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Roundtable January 2014