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Bernhard’s article on Plänet Debian about the “colon” command in the shell could use a clarification and a security-relevant correcture.

There is, indeed, no difference between the : and true built-in commands.

Stéphane Chazelas points out that writing : ${VARNAME:=default} is bad, : "${VARNAME:=default}" is correct. Reason: someone could preset $VARNAME with, for example, /*/*/*/*/../../../../*/*/*/*/../../../../*/*/*/* which will exhaust during globbing.

Besides that, the article is good. Thanks Bernhard for posting it!

PS: I sometimes use the colon as comment leader in the last line of a script or function, because it, unlike the octothorpe, sets $? to 0, which can be useful.

Update: As jilles pointed out in IRC, “colon” (‘:’) is a POSIX special built-in (most importantly, it keeps assignments), whereas “true” is a regular built-in utility.

mksh R50d released

07.10.2014 by tg@
Tags: bug debian mksh news pcli

The last MirBSD Korn Shell update broke update-initramfs because I accidentally introduced a regression in field splitting while fixing other bugs – sorry!

mksh R50d was just released to fix that, and a small NULL pointer dereference found by Goodbox on IRC. Thanks to my employer tarent for a bit of time to work on it.

mksh R50c released, security fix

03.10.2014 by tg@
Tags: android bug debian mksh news pcli release security

The MirBSD Korn Shell has got a new security and maintenance release.

This release fixes one mksh(1)-specific issue when importing values from the environment. The issue has been detected by the main developer during careful code review, looking at whether the shell is affected by the recent “shellshock” bugs in GNU bash, many of which also affect AT&T ksh93. (The answer is: no, none of these bugs affects mksh.) Stephane Chanzelas kindly provided me with an in-depth look at how this can be exploited. The issue has not got a CVE identifier because it was identified as low-risk. The problem here is that the environment import filter mistakenly accepted variables named “FOO+” (for any FOO), which are, by general environ(7) syntax, distinct from “FOO”, and treated them as appending to the value of “FOO”. An attacker who already had access to the environment could so append values to parameters passed through programs (including sudo(8) or setuid) to shell scripts, including indirectly, after those programs intended to sanitise the environment, e.g. invalidating the last $PATH component. It could also be used to circumvent sudo’s environment filter which protected against the vulnerability of an unpatched GNU bash being exploited.

tl;dr: mksh not affected by any shellshock bugs, but we found a bug of our own, with low impact, which does not affect any other shell, during careful code review. Please do update to mksh R50c quickly.

mksh R50b released

03.09.2014 by tg@
Tags: mksh news pcli

The MirBSD Korn Shell has got a new bugfix release. Thought you’d want to know ☺

mksh R50, jupp 27 released

29.06.2014 by tg@
Tags: jupp mksh news pcli

Both the MirBSD Korn Shell and jupp – the editor which sucks less have seen new releases today. Please test them, report all bugs, and otherwise enjoy all the bugfixes.

Other subprojects will also have new releases… once I get around doing so after hacking them…

Update 03.07.2014: New release for MirCPIO, that is, cpio(1) and pax(1) and tar(1) in a somewhat portable package.

-r--r--r-- 4 tg miros-cvssrc 141973 Jul 3 19:56 /MirOS/dist/mir/cpio/paxmirabilis-20140703.cpio.gz

mksh build problem workaround

26.01.2014 by tg@
Tags: mksh

As a workaround to the build problem of mksh R49 with some host shells, you can try removing every sequence of backslash + newline in rlimits.opt and sh_flags.opt, for example with the following sequence:

	cd /path/to/mksh
	for f in *.opt; do
		tr '\n' '`' <"$f" | \
		    sed 's/\\`//g' | \
		    tr '`' '\n' >"$f.out"
		mv "$f.out" "$f"
	done
 

This will apply to every upcoming mksh(1) release until such time as this code has been rewritten in (host) C. Another thing that could be done is to add -r to both IFS= read line occurences in Build.sh, function do_genopt.

FOSDEM preparations… done.

20.01.2014 by tg@
Tags: debian event fun grml mksh twitxr work

I’ve produced several pin-on buttons to take with me to FOSDEM for giving away (as long as there are any left):

Several pin-on buttons I made

First row (nice projects), from left to right: MidnightBSD; Glenda, the Plan 9 bunny; Teckids e.V.

Second row (The MirOS Project): mksh; the Shilouette Dæmon; the “Triforce” (Live+Install CDs for i386 and sparc, with MirGrml); “the m” (alternative logo, vector)

Third row (things originating from tarent): Freedroidz (now a Teckids project); OSIAM (Identity and Access Management); tarent (tarent AG, tarent GmbH), who sponsored production of these buttons

Hm… jupp needs a button’able logo!


FOSDEM meetup

mksh-current version "R48 2013/11/17" (only this version, no others) suffer from a now-known regression which can make your MirBSD system unbootable. Please immediately either revert to an earlier version (such as a stable release) or update to "R48 2013/11/29" from AnonCVS.

This reverts the fix for “x="X 1 2"; showargs ${x#X}”, which nevertheless is a genuine bug. Contributions fixing it without introducing any such regressions welcome…

FrOSCon is approaching, and all MirBSD developers will attend… but why’s there no MirBSD exhibit? The answer to that is a bit complex. First let’s state that of course we will participate in the event as well as the Open Source world. We’ll also be geocaching around the campus with other interested (mostly OSS) people (including those we won for this sport) and helping out other OSS projects we’ve become attached to.

MirOS BSD, the operating system, is a niche system. The conference on the other hand got “younger” and more mainstream. This means that almost all conference visitors do not belong to the target group of MirOS BSD which somewhat is an “ancient solution”: the most classical BSD around (NetBSD® loses because they have rc.d and PAM and lack sendmail(8), sorry guys, your attempt at being not reformable doesn’t count) and running on restricted hardware (such as my 486SLC with 12 MiB RAM) and exots (SPARCstation). It’s viable even as developer workstation (if your hardware is supported… otherwise just virtualise it) but its strength lies with SPARC support and “embedded x86”. And being run as virtual machine: we’re reportedly more stable and more performant than OpenBSD. MirBSD is not cut off from modern development and occasionally takes a questionable but justified choice (such as using 16-bit Unicode internally) or a weird-looking but beneficial one (such as OPTU encoding saving us locale(1) hassles) or even acts as technological pioneer (64-bit time_t on ILP32 platforms) or, at least, is faster than OpenBSD (newer GNU toolchain, things like that), but usually more conservatively, and yes, this is by design, not by lack of manpower, most of the time.

The MirPorts Framework, while technically superiour in enough places, is something that just cannot happen without manpower. I (tg@) am still using it exclusively, continuing to update ports I use and occasionally creating new ones (mupdf is in the works!), but it’s not something I’d recommend someone (other than an Mac OSX user) to use on a nōn-MirBSD system (Interix is not exactly thriving either, and the Interix support was only begun; other OSes are not widely tested).

The MirBSD Korn Shell is probably the one thing I will be remembered for. But I have absolutely no idea how one would present it on a booth at such an exhibition. A talk is much more likely. So no on that front too.

jupp, the editor which sucks less, is probably something that does deserve mainstream interest (especially considering Natureshadow is using it while teaching computing to kids) but probably more in a workshop setting. And booth space is precious enough in the FH so I think that’d be unfair.

All the other subprojects and side projects Benny and I have, such as mirₘᵢₙcⒺ, josef stalin, FreeWRT, Lunix Ewe, Shellsnippets, the fonts, etc. are interesting but share few, if any, common ground. Again, this does not match the vast majority of visitors. While we probably should push a number of these more, but a booth isn’t “it” here, either.

MirOS Linux (“MirLinux”) and MirOS Windows are, despite otherwise-saying rumours called W*k*p*d*a, only premature ideas that will not really be worked on (though MirLinux concepts are found in mirₘᵢₙcⒺ and stalin).

As you can see, despite all developers having full-time dayjobs, The MirOS Project is far from being obsolete. We hope that our website visitors understand our reasons to not have an exhibition booth of our own (even if the SPARCstation makes for a way cool one, it’s too heavy to lift all the time), and would like to point out that there are several other booths (commercial ones, as well as OSS ones such as AllBSD, Debian and (talking to) others) and other itineries we participate in. This year both Benny and I have been roped into helping out the conference itself, too (not exactly unvoluntarily though).

The best way to talk to us is IRC during regular European “geek” hours (i.e. until way too late into the night – which Americans should benefit from), semi-synchronously, or mailing lists. We sort of expect you to not be afraid to RTFM and look up acronyms you don’t understand; The MirOS Project is not unfriendly but definitely not suited for your proverbial Aunt Tilly, newbies, “desktop” users, and people who aren’t at least somewhat capable of using written English (this is by design).

mksh/Win32

18.07.2013 by tg@

Michael Langguth and Scalaris AG asked me to publish the mksh/Win32 Beta 14 source and binary archive, and it is with joy I’m doing this.

Checksums and Hashes

  • RMD160 (ports/mksh-w32-beta14.zip) = 0dc8ef6e95592bd132f701ca77c4e0a3afe46f24
  • TIGER (ports/mksh-w32-beta14.zip) = 966e548f9e9c1d5b137ae3ec48e60db4a57c9a0ed15720fb
  • 1181543005 517402 /MirOS/dist/mir/mksh/ports/mksh-w32-beta14.zip
  • MD5 (ports/mksh-w32-beta14.zip) = b57367b0710bf76a972b493562e2b6b5

Just a few words on it (more in the README.1st file included): this is a port of The MirBSD Korn Shell R39 to the native WinAPI; it’s not quite got the full Unix feel (especially as it targets the Weihenstephan unxutils instead of a full Interix or Cygwin environment) but doesn’t need a full POSIX emulation layer either. It’s intended to replace MKS ksh and the MKS Toolkit. Source for the compatibility library is also included under The MirOS Licence; we aim at publishing it as OSI Certified Open Source Software like mksh itself. (There is a situation with dlmalloc/nedmalloc being resolved, and the icon is derived from the BSD dæmon which is a protected unregistered trademark, but we’re not Mozilla and allow distro packages to keep using it ☺) Rebasing it on a newer mksh(1) followed by (partial) integration into the main source code is a goal.

Have fun trying it out and hacking on it. It’s currently built with -DMKSH_NOPROSPECTOFWORK (so coprocesses and a few other minor things won’t work), but a SIGCHLD emulation is being worked on – but if you want to help out, I’m sure it’s welcome, just come on IRC or post on the mailing list, and I’ll forward things to Michael as needed. Reports on testing with other toolchain and OS versions are also welcome.

mksh R45 released

26.04.2013 by tg@

The MirBSD Korn Shell R45 has been released today, and R44 has been named the new stable/bugfix-only series. (That’s version 45.1, not 0.45, dear Homebrew/MacOSX packagers.)

Packagers rejoice: the -DMKSH_GCC55009 dance is no longer needed, and even the run-time check for integer division is gone. Why? Because I realised one cannot use signed integers in C, at all, and rewrote the mksh(1) arithmetics code to use unsigned integers only. Special thanks to the people from musl libc and, to some lesser amount, Natureshadow for providing me with ideas what algorithms to replace some functionality with (signed shell arithmetic is, of course, still usable, it is just emulated using unsigned C integers now).

The following entertainment…

	tg@blau:~ $ echo foo >/bar\ baz
	/bin/mksh: can't create /bar baz: Permission denied
	1|tg@blau:~ $ doch
	tg@blau:~ $ cat /bar\ baz
	foo
 

… was provided by Tonnerre Lombard; like Swedish, German has got a number of words that cannot be expressed in English so I feel not up to the task of explaining this to people who don’t know the German word “doch”, just rest assured it calls the last input line (be careful, this is literally a line, so don’t use backslash-newline sequences) using sudo(8).

mksh R42b and R41c released

15.02.2013 by tg@
Tags: mksh

The MirBSD Korn Shell must-have bugfix releases R42b (for the current formal release series) and R41c (for the last bugfix-only stable series) have been issued. Debian testing/unstable users get the fixes through their package management, versioned 40.9.20120630-7 targetting wheezy (hopefully). Debian experimental users will receive a 42b-1 upload, closer to what other distro packages provide, soonish, targetting jessie.

Since we lack anything better (that, unless Freshmeat, is actually usable), by request of our packagers, new mksh(1) releases will be announced on our miros-mksh@ mailing list starting now.

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