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I use zip bombs to protect my server

idiallo.com

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Re: I use zip bombs to protect my server

#221
post #62

> At my old employer, a bot discovered a wordpress vulnerability and inserted a malicious script into our server I know it's slightly off topic, but it's just so amusing (edit: reassuring) to know I'm not the only one who, after 1 hour of setting up Wordpress there's a PHP shell magically deployed on my server.

Yes, never self host Wordpress if you value your sanity. Even if it’s not the first hour it will eventually happen when you forget a patch.

Ditto to self-hosting wordpress works fine with standard hosting practices and not installing a bazillion random plugins.

Re: I use zip bombs to protect my server

#222
post #54

Is there any legal exposure possible? Like, a legitimate crawler suing you and alleging that you broke something of theirs?

Just crossed my mind that perhaps lots of bot traffic is coming from botnets of unaware victims who downloaded a shitty game or similar, orchestrated by a malicious C&C server somewhere else. (There was a post about this type of malware recently.) Now, if you crash the victims machine, it’s complicated at least ethically, if not legally.

Re: I use zip bombs to protect my server

#223

These days, almost all browsers accept zstd and brotli, so these bombs can be even more effective today! [This]( https://news.ycombinator.com/item?id=23496794 ) old comment showed an impressive 1.2M:1 compression ratio and [zstd seems to be doing even better]( https://github.com/netty/netty/issues/14004 ). Though, bots may not support modern compression standards. Then again, that may be a good way to block bots: eve…

If you nest the gzip inside another gzip it gets even smaller since the blocks of compressed '0' data are themselves low entropy in the first generation gzip. Nested zst reduces the 10G file to 99 bytes.

Wouldnt that defeat the attack though as you arent serving the large content anymore

Re: I use zip bombs to protect my server

#224

Earlier quoted context omitted.

There's a lot of essential functionality missing from WordPress, meaning you have to install plugins. Depending on what you need to do. But it's such a bad platform that there really isn't any reason for anybody to use WordPress for anything. No matter your use case, there will be a better alternative to WordPress.

Can you recommend an alternative for a non-technical organization, where there's someone who needs to be able to edit pages and upload documents on a regular basis, so they need as user-friendly an interface as possible for that? Especially when they don't have a budget for it, and you're helping them out as a favor? It's so easy to spin up Wordpress for them, but I'm not a fan either. I've tried Drupal in the past f…

I find it very telling that there's no 2 responses to this post recommending the same thing. Confirms my belief that there is no real alternative to Wordpress for a free and open-source CMS that is straightforward to install and usable to build and edit pages by non-tech-experts.

Re: I use zip bombs to protect my server

#225

Earlier quoted context omitted.

If you nest the gzip inside another gzip it gets even smaller since the blocks of compressed '0' data are themselves low entropy in the first generation gzip. Nested zst reduces the 10G file to 99 bytes.

Wouldnt that defeat the attack though as you arent serving the large content anymore

It would need a bot that is accessing files via hyperlink with an aim to decompress them and riffle through their contents. The compressed file can be delivered over a compressed response to achieve the two layers, cutting down significantly on the outbound traffic. passwd.zst, secrets.docx, etc. would look pretty juicy. Throw some bait in honeypot directories (exposed for file access) listed in robots.txt and see who takes it.

Re: I use zip bombs to protect my server

#226

Earlier quoted context omitted.

If you nest the gzip inside another gzip it gets even smaller since the blocks of compressed '0' data are themselves low entropy in the first generation gzip. Nested zst reduces the 10G file to 99 bytes.

Can you hand edit to create recursive file structures to make it infinite? I used to use debug in dos to make what appeared to be gigantic floppy discs by editing the fat

That's what I was hoping for with the original article.

Re: I use zip bombs to protect my server

#227

These days, almost all browsers accept zstd and brotli, so these bombs can be even more effective today! [This]( https://news.ycombinator.com/item?id=23496794 ) old comment showed an impressive 1.2M:1 compression ratio and [zstd seems to be doing even better]( https://github.com/netty/netty/issues/14004 ). Though, bots may not support modern compression standards. Then again, that may be a good way to block bots: eve…

How will my browser react on receiving such bombs? I’d rather not to test it myself…

Re: I use zip bombs to protect my server

#228
Once upon a time around 2001 or so I used to have a static line at home and host some stuff on my home linux box. A windows NT update had meant a lot of them had enabled this optimistic encryption thing where windows boxes would try to connect to a certain port and negotiate an s/wan before doing TCP traffic. I was used to seeing this traffic a lot on my firewall so no big deal. However there was one machine in particular that was really obnoxious. It would try to connect every few seconds and would just not quit.

I tried to contact the admin of the box (yeah that’s what people used to do) and got nowhere. Eventually I sent a message saying “hey I see your machine trying to connect every few seconds on port . I’m just sending a heads up that we’re starting a new service on that port and I want to make sure it doesn’t cause you any problems.”

Of course I didn’t hear back. Then I set up a server on that port that basically read from /dev/urandom, set TCP_NODELAY and a few other flags and pushed out random gibberish as fast as possible. I figured the clients of this service might not want their strings of randomness to be null-terminated so I thoughtfully removed any nulls that might otherwise naturally occur. The misconfigured NT box connected, drank 5 seconds or so worth of randomness, then disappeared. Then 5 minutes later, reappeared, connected, took its buffer overflow medicine and disappeared again. And this pattern then continued for a few weeks until the box disappeared from the internet completely.

I like to imagine that some admin was just sitting there scratching his head wondering why his NT box kept rebooting.

Re: I use zip bombs to protect my server

#229
post #182
post #114

I'm curious why a 10GB file of all zeroes would compress only to 10MB. I mean theoretically you could compress it to one byte. I suppose the compression happens on a stream of data instead of analyzing the whole, but I'd assume it would still do better than 10MB.

Good question. The "ultimate zip bomb" looks something like https://github.com/iamtraction/ZOD - this produces the infamous "42.zip" file, which is about 42KiB, but expands to 3.99 PiB (!). There's literally no machine on Earth today that can deal with that (as a single file, I mean).

Do must unzip programs work recursively by default?

Re: I use zip bombs to protect my server

#230
post #166

Earlier quoted context omitted.

I made a 64kx64k JPEG once by feeding the encoder the same line of macro blocks until it produce the entire image. Years later I was finally able to open it.

I had a ton of trouble opening a 10MB or so png a few weeks back. It was stitched together screenshots forming a map of some areas in a game, so it was quite large. Some stuff refused to open it at all as if the file was invalid, some would hang for minutes, some opened blurry. My first semi-success was Fossify Gallery on my phone from F-Droid. If I let it chug a bit, it'd show a blurry image, a while longer it'd foc…

Firefox on a mid-tier Samsung and a cheapo data connection (4G) took avout 30s to load. I could pan, but it limited me from zooming much, and the little I could zoom in looked quite blury.
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