How to stop Samba users deleting their home directory and email

Samba Carnival Helsinki summer 2009
Samba Carnival (the real Samba logo is sooo boring)

UNIX permissions can send you around the twist sometimes. You can set them up to do anything, not. Here’s a good case in point…

Imagine you have Samba set up to provide users with a home directory. This is a useful feature; if you log in to the server with the name “fred” you (and only you) will see a network share called “fred”, which contains the files in your UNIX/Linux home directory. This is great for knowledgeable computer types, but is it such a great idea for normal lusers? If you’re running IMAP email it’s going to expose your mail directory, .forward and a load of other files that Windoze users might delete on a whim, and really screw things up.

Is there a Samba option to share home directories but to leave certain subdirectories alone? No. Can you just change the ownership and permissions of the critical files to  root and deny write access? No! (Because mail systems require such files to be owned by their user for security reasons). Can you use permission bits or even an ACL? Possibly, but you’ll go insane trying.

A bit of lateral thinking is called for here. Let’s start with the standard section in smb.conf for creating automatic shares for home directories:

[homes]
    comment = Home Directories
    browseable = no
    writable = yes

The “homes” section is special – the name “homes” is reserved to make it so. Basically it auto-creates a share with a name matching the user when someone logs in, so that they can get to their home directory.

First off, you could make it non-writable (i.e. set writable = no). Not much use to use luser, but it does the job of stopping them deleting anything. If read-only access is good enough, it’s an option.

The next idea, if you want it to be useful, is to use the directive “hide dot files” in the definition. This basically returns files beginning in a ‘.’ as “hidden” to Windoze users, hiding the UNIX user configuration files and other stuff you don’t want deleted. Unfortunately the “mail” directory, containing all your loverly IMAP folders is still available for wonton destruction, but you can hide this too by renaming it .mail. All you then need to do is tell your mail server to use the new name. For example, in dovecot.conf, uncomment and edit the line thus:

mail_location = mbox:~/.mail/:INBOX=/var/mail/%u

(Note the ‘.’ added at the front of ~/mail/)

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You then have to rename each of the user’s “mail” folders to “.mail”, restart dovecot and the job is done.

Except when you have lusers who have turned on the “Show Hidden Files” option in Windoze, of course. A surprising number seem to think this is a good idea. You could decide that hidden files allows advanced users control of their mail and configuration, and anyone messing with a hidden file can presumably be trusted to know what you’re doing. You could even mess with Windoze policies to stop them doing this (ha!). Or you may take the view that all lusers and dangerous and if there is a way to mess things up, they’ll find it and do it. In this case, here’s Plan B.

The trick is to know that the default path to shares in [homes] is ‘~’, but you can actually override this! For example:

[homes]
    path = /usr/data/flubnutz
    ...

This  maps users’ home directories in a single directory called ‘flubnutz’. This is not that useful, and I haven’t even bothered to try it myself. When it becomes interesting is when you can add a macro to the path name. %S is a good one to use because it’s the name as the user who has logged in (the service name). %u, likewise. You can then do stuff like:

[homes]
     path = /usr/samba-files/%S
     ....

This stores the user’s home directory files in a completely different location, in a directory matching their name. If you prefer to keep the user’s account files together (like a sensible UNIX admin) you can use:

[homes]
     comment = Home Directories
     path = /usr/home/%S/samba-files
     browseable = no
     writable = yes<

As you can imagine, this stores their Windows home directory files in a sub-directory to their home directory; one which they can’t escape from. You have to create “~/samba-files” and give them ownership of it for this to work. If you don’t want to use the explicit path, %h/samba-files should do instead.

I’ve written a few scripts to create directories and set permissions, which I might add to this if anyone expresses an interest.

 

Governments’ hacking fantasies

It’s silly season again.

Yesterday George Osborne warned that Islamists were tooling up and planning deadly cyber-attacks against the UK, targeting critical systems like ATC and hospitals, as he announced government spending on countermeasures would double from about £200M to £400M a year. Mr Osborne shown a rather tenuous grasp of technology in the past, and I fear he’s been watching too many Hollywood movies when forming his current opinion.

I know a bit about ATC, and the chances of a jihadi disrupting NAS over the internet are slight. Damaging aviation is much easier by more direct means.

Likewise, while I have little time for the design of NHS computers systems, even they’d be hard to seriously disrupt. So difficult that it really wouldn’t be worth the bother. If you want to knock out a hospital, blow up the generators and electricity feed – it’s obvious. About the only systemic damage you could do remotely would be to mess up central databases, but these seem to get messed up regularly anyway, and the world goes on.

But this seems positively sane and sensible compared to today’s report from the “US-China Economic and Security Review Commission”. They’re all exercised about those nasty Chinese guys pinching trade secrets by hacking in to US companies and their government agencies. I’m sceptical about the idea that the Chinese government is behind this, and the Commission has weakened the credibility of their claims with their suggested response to the activity:

Yes folks, their suggestion is that Americans hack in to the Chinese systems and steal back or delete the stolen data. How exactly does one steal back data? And do they really think it’s possible to locate, identify and delete stolen data found in a foreign country. Deleting all copies of data from a local system is hard enough, and if the IT department knows its stuff, it’s impossible as it won’t all be on-line.

Whilst there’s plenty of evidence that people in China, and possibly the military, are engaged in cyber-espionage, this idea reads like the plot of another Hollywood movie of the type George Osborne seems to have been watching. Everyone in the security world knows that the majority of criminal activity on the Internet actually comes from…. the USA. This doesn’t mean the US government is behind it – by the sound of the advice they’re getting, they wouldn’t know how.

People like me have been saying that cyber-crime is (going to be) a big problem for many years now, and I welcome governments waking up and taking it seriously at last. The private sector has done spectacularly badly, as the money is in the superficial stuff, and real security gets in the  way of profits. It’s just a shame that governments have woken up and are groping groggily around in the dark.

FreeBSD on 96-core 64-bit ARMv8

A couple of year’s back I managed to compile and run FreeBSD/Apache/BIND on an ARM-based Raspberry Pi. It was fun, but I have to admit it’s been left on the shelf ever since. A solution waiting for a problem.

Since then the ARM has been a specific target for FreeBSD 11. Do you really need FreeBSD on your smartphone? However much I like BSD, the Linux-based Android does well enough. But wait…

ARM has a 64-bit turbo-nutter-bastard version waiting in the wings, for server use. The ARMv8 is scalable to at least 48 cores per socket and intended to go like the clappers in SMP applications. FreeBSD has long been considered to have the edge over the Linux kernel when it comes to SMP. This is getting interesting.

Cavium-ThunderX
Cavium ThunderX ARMv8 board board.

A team including Semihalf has now got FreeBSD 11 stable running on a twin-CPU monster using the Cavium ThunderX ARM chips, each of which has 48-cores. For details see their blog. With a lot of serious web applications running FreeBSD in preference to the freewheeling Linux, there could be a very ready market for this kind of box.

I would be in danger of being extremely jealous, as my budget for playing with ARM chips doesn’t stretch much past the Raspberry Pi. However, in the 1980’s Atari Research gave me an ATW transputer box with 128 discrete CPUs to help implement an OS on, so I’m still 32-cores ahead. There wasn’t much of a market for the ATW back then, but Cavium could be on to a winner with the approach nearly thirty years later.

Footnote

Does anyone know what happened to the big transputer box prototype that was knocking around the Cambridge office? When the ATW/Abaq was released it was greatly scaled down with no more than 13 transputers, and lacked the glass case with all the flashing lights.

Microsoft plans to dump OneDrive unlimited and Windows 7

Microsoft continues to lose the plot. This week saw the announcement that OneDrive customers have a year to shift their data way, and business have a year to switch from Windows 7 to Linux Windows 10.

The problem they’re having with OneDrive is that when they sold it on the basis of “unlimited” storage, they didn’t realise the punters would actually believe them. After all, who believes what Microsoft says about any of their products? But, apparently, some credulous customers have been using it for backing up all their stuff and this has caught the folks in Redmond by surprise. So they’re withrawing the product, and users have a (at least) year to shift their stuff off, after which the Office365 subscription would have lapsed anyway. The maximum storage available after that date will be 1Tb, but they have yet explain what will happen to the excess.

And in the same week, Microsoft announced that Windows 7 will no longer be available in a year. It may surprise some to hear that it’s still available, as anyone buying a domestic PC from the high street has only had Windows 8 since 2013. However, if you buy a business machine from a business supplier, chances are it will still have Windows 7 pre-installed, with a set of Windows 8 downgrade disks in the box to satisfy an “everything now ships with Windows 8” clause in some OEM deal. Businesses don’t want Windows 8, and voted with their cheque books to keep Windows 7.

Microsoft now plans to take that choice away, and force everyone on to Windows 10. This is hardly unexpected, but now it’s official. The reasons aren’t clear to me. Okay, Windows 10 has the creepy doll sending user data back at Redmond, in order to deliver a richer user experience (and targeted adverts) and make the world a better place (for Microsoft shareholders). Possibly a case of corporate Google-envy? Is Microsoft so keen on the Google business model that they’d risk hacking off the loyal customers who’ve been buying Windows XP and Windows 7 for years? Ironically, Google is pushing it’s paid-for cloud apps, and I suspect, would like to get a larger revenue stream from selling SaaS.

Listen up, Microsoft. People buy Windows because it runs the applications they want. It has nothing to do with whether the like the colour scheme. Windows XP runs DOS stuff; Windows 7 does, just about, because it has XP emulation. This is a concept known as Backward compatibility, and Intel knows all about exploiting this and making mega $$$ if you need a reminder. Lightweight home users and kids might be impressed by the new and shiny, but business wants something that works, and if it ain’t broke, don’t fix it.

The beneficiaries of this will probably be Linux (including Android), Google GDrive and other cloud storage providers, and alternatives to Office: (Google Docs, OpenOffice.org and smaller companies like SoftMaker. The latter has just released SoftMaker Office 2016, with an offer to make it free for use in schools.

TalkTalk Ransom Demand

So, the head of TalkTalk (Dido Harding) has received a ransom demand following the latest hack? From a bunch of Islamist gangsters? I don’t think so. Okay, she probably received an email extortion attempt. Several in fact. It’d be form for Islamist gangsters to have a go, amongst the usual suspects. But the idea that whoever is behind the attacks also sent the ransom demand does not sound like the normal MO. It smells wrong to me. Extortion attempts of this kind generally follow a demonstration that the criminals can disrupt a web site, not after a long-term outage.

I get the vibes that TalkTalk doesn’t know what happened, and take everything they say with a pinch of salt. The only certainty is that their web site was toppled. Data theft, or script kiddies? I suspect the latter, actually. They floated the possibility of widespread data theft, which is very responsible of them until it’s figured out what exactly happened. This is a possibility in any attack.

Meanwhile, people are now questioning whether the stolen data (if there was any) was encrypted, and if not, why not. On a live system, data can’t be encrypted. Think about it! This is allegedly a hack of a live system, so the criminals would have access to the same data that he live system would.

This whole story has been hyped up way beyond the facts. No one (including TalkTalk) wants to suggest it may be overblown for fear of being branded irresponsible by a technically illiterate news media and opportunistic politicians. But it smells all wrong to me. How much more embarrassing if it was was actually script kiddies getting lucky, rather than the APT being hinted at.

No talk from TalkTalk

Charles Dunston’s budget ISP TalkTalk has been hacked again. Yawn. This time it’s big news on TV; the headline story in fact. Their website has been KOed for a couple of days, but it’s back online with a front page showing a different news agenda. They get their feed from AOL (also part of the Carphone Warehouse family), who probably just missed the kerfuffle; there’s no celebrity connection after all. Not yet, anyway.

If you’re a TalkTalk retail customer (or possibly a business customer – who knows how their systems interrelate and what data’s been pilfered), and you’ve used the same password with TalkTalk as any other sites, change your password on those sites NOW. The popular media is full of speculation as to what’s been compromised but they’re not mentioning passwords, presumably because TalkTalk will have told them that any passwords would have been encrypted. But if the criminals have got hold of the hashes, which is likely, it’s only a matter of time before they crack them.

How worried should customers of other ISPs be? Pretty worried, as on the serious side of the business they’re known as Opal Telecom, a significant LLU operator providing the link between the last time and the data centre for a large number of Broadband providers.

I can, of course, only speculate as to why this keeps happening to them. One reason might be related to several conversations I’ve had with people from ISPs TalkTalk has taken over along the way. Apparently they really don’t like hard stuff like UNIX/Linux, and within months of a takeover they force a switch to Microsoft before making all the UNIX people redundant. Any fool can use Microsoft – low levels of technical understanding are required, meaning cheap engineers and lower costs. But do their Microsofties actually know what they’re doing? I dare say that some of them do, and some of them don’t. But the bar for a point-and-click Microsoft house going to be lower.

The spammed malware attack continues, but Microsoft SE has been getting it wrong

Kudos to Microsoft Security Essentials for picking up the nasty attachment being pumped out like crazy by the clean-skin botnet recently, while most of the other scanners failed to detect it. However, it was wrong about the identity of the malware. It’s not  Peals.F!plock, as I originally reported with skepticism. It’s now detected as a variation of something known as Troj/DocDl-YU (to use the name give by Sophos). Read about it here:

https://www.sophos.com/en-us/threat-center/threat-analyses/viruses-and-spyware/Troj~DocDl-YU/detailed-analysis.aspx

This uses Microsoft’s Office macro language to download further malware from the Internet and install it on the victim’s PC, so if anyone activates it there’ll be more than just this Trojan downloader to worry about. As it’s a Microsoft Word document, people tend to open it. If the government really wants to spend money telling the public how to avoid falling victim to cybercrime, they should start by warning about sending documents by email, instead of the current nonsense. Microsoft might get the hump, though, and as I understand it, they’re acting as advisors.

If people have macros disabled on Word, they’re probably okay as long as they don’t get tricked in to enabling them. I’m not hopeful in this regard.

Meanwhile, those behind it are changing the message tweaking the payload to avoid detection – quite successfully! The latest incarnation reads:


From: UUSCOTLAND@example.com

Subject: Water Services Invoice

Good Morning,

I hope you are well.

Please find attached the water services invoice summary for the billing period of 22 September 2015 to 22 October 2015.

If you would like any more help, or information, please contact me on 0345 #######. Our office is open between 9.00am and 5.00pm Monday to Friday. I will be happy to help you. Alternatively you can email me at UUSCOTLAND@example.com

Kind regards

Melissa

Melissa Lears

Billing Specialist

Business Retail

United Utilities Scotland

T: 0345 ####### (#####)

 


They appear to be updating it every morning at around 0800Z. Let’s see what we get tomorrow.

 

iZettle now works with Apple iOS 9(.1)

I’ve just had a note to say that Apple has released a new version of its smartphone/tablet system that fixes the bluetooth bug in version 9.0 that prevented iZettle readers to connect using Bluetooth. So fanbois can now upgrade their fondleslabs without cutting of their revenue stream.

For details see here: https://www.izettle.com/gb/help/articles/2122036

On the Android front, teething problems with iZettle 3.0 software  – the one that works with contactless – seem to have been fixed with version 3.0.1, although 3.0.2 also turned up a couple of days ago. Given some harsh testing with me, it was impossible to get version 3.0.1 confused by turning things on in the wrong order. However, some people have taken to the play store to say it’s still broken. It could be that its incompatible with their handsets (they don’t say which version of Android they’re using) – it could also be that it’s the cable connected version, which always seemed to be on the cusp of working reliably at the best of times.

While they were at it, they’ve fixed a few oddities in the user interface, so you can now just put through a payment without having to add it to the cart first (one of the points I made in the original review).

I’d be interested to hear details if anyone is still having trouble, and I may be able to help.

New botnet spammed malware – Peals.F!plock

This is a big one, coming from hitherto unlisted botnet addresses – and it’s coming right now. I’m cross referencing the blacklisted addresses now to see if I can see who’s had an expansion lately. Spamassassin isn’t that great at picking it up, with about 10% getting straight through and about 90% failing to reach five points.

It’s a Microsoft Word document, apparently containing controversial malware Peals.F!plock. Little is known about this, other than Security Essentials flagging it but others say it’s a false positive. Well someone’s gone to a lot of trouble to sent it a “false positive”.

The messages all claim to come from “Stephanie Greaves”, sgreaves at btros.co.uk, with a fixed subject of COS007202, which is unusual. You’d have thought that if you’re using a clean botnet you’d randomise things a bit. This is a genuine domain name (with no SPF – come on guys!) and for all I know, Stephanie Greaves is the name of a genuine victim. Their MX is a virtual server and they’re probably wondering why it’s been heavily loaded since 9am.

Whoever’s doing this has a pretty comprehensive spamming list, containing nearly all of my honeypots.

Update:

This same malware is now being sent out claiming to be from customerservices@ocado.com with the subject “Your receipt for today’s Ocado delivery”, and an HTML message looking like an Ocado receipt (as far as I can tell – I shop for my own groceries!) Again, Ocado doesn’t seem to have SPF set up.

The message text is:


 

HERE’S YOUR RECEIPT

Hello

Your receipt for today’s delivery is attached to this email. I’ll be delivering your 12:00-14:00 order and, so you’ll know it’s me, I’ll be driving the Lemon van.

Your order doesn’t have any substitutions, everything’s there.

See you later,

Paul

 


The fake bombardier one reads:

Good morning,
Please see attached purchase order.
Kind regards,
Stephanie Greaves
cid:image002.jpg@01D01077.BAC48BA0
Administration Apprentice
Bombardier Transportation (Rolling Stock) UK Ltd
Electronics, Cabling, & Interior Division
Litchurch Lane, Derby, DE24 8AD

 

Update: 20-Oct-15 11:22

The malware spam now looks like this:

From: Shaun Buzzard <shaunb@hubbardproducts.com>
To: <to_addr}}>  <-- Note error
Subject: Order

Hi ,

Please find attached order.

 

Kind regards.

Shaun Buzzard

 

 

Is Northolt Aerodrome Dangerous?

Biggin Hill, a rival airfield to Northolt chasing executive jet traffic for London, has got hold of a 2012 report that says Northolt  doesn’t meet current CAA standards for obstacle clearance, especially at the east end of the runway. Northolt has been there for a hundred years, so shame on the local council for allowing this alleged dangerous development to have taken place.

It wouldn’t be the only airfield to lose its CAA license since new rules came in (e.g. Sandown and Bembridge on the IoW) but then again it’s a military/government field and is regulated by the MAA instead. The civil operators of Biggin Hill and Oxford reckon the CAA should take over regulation, and (presumably) shut their rival down. They would say that, wouldn’t they?

Of course, a cynic like me may wonder whether the value of a huge plot of land next to the A40 had a bearing on what interested parties have to say on the subject.