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by ebursztein 852 days ago
Thanks for the feedback -- we will look into it. If you can share with us the list of URL that would be very helpful so we can reproduce - send us an email at magika-dev@google.com if that is possible.

For crawling we have planned a head only model to avoid fetching the whole file but it is not ready yet -- we weren't sure what use-cases would emerge so that is good to know that such model might be useful.

We mostly use Magika internally to route files for AV scanning as we wrote in the blog post, so it is possible that despite our best effort to test Magika extensively on various file types it is not as good on fonts format as it should be. We will look into.

Thanks again for sharing your experience with Magika this is very useful.
2 comments
TomNomNom 852 days ago
Sure thing :)

Here's[0] a .tgz file with 3 files in it that are misidentified by magika but correctly identified by the `file` utility: asp.html, vba.html, unknown.woff

These are files that were in one of my crawl datasets.

[0]: https://poc.lol/files/magika-test.tgz

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ebursztein 852 days ago
Thank you - we are adding them to our test suit for the next version.
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TomNomNom 852 days ago
Super, thank you! I look forward to it :)

I've worked on similar problems recently so I'm well aware of how difficult this is. An example I've given people is in automatically detecting base64-encoded data. It seems easy at first, but any four, eight, or twelve (etc) letter word is technically valid base64, so you need to decide if and how those things should be excluded.

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beeboobaa 852 days ago
Do you have permission to redistribute these files?
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renewiltord 852 days ago
LOL nice b8 m8. For the rest of you who are curious, the files look like this:

    <HTML><HEAD>
    <TITLE>Access Denied</TITLE>
    </HEAD><BODY>
    <H1>Access Denied</H1>
     
    You don't have permission to access "http&#58;&#47;&#47;placement&#46;api&#46;test4&#46;example&#46;com&#47;" on this server.<P>
    Reference&#32;&#35;18&#46;9cb0f748&#46;1695037739&#46;283e2e00
    </BODY>
    </HTML>
Legend. "Do you have permission" hahaha.
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IvyMike 852 days ago
You are asking what if this guy has "web crawl data" that google does not have?

And what if he says no, he does not have permission.

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beeboobaa 852 days ago
> You are asking what if this guy has "web crawl data" that google does not have?

No, I'm asking if he has permission to redistribute these files.

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timschmidt 852 days ago
Are you attempting to assert that use of these files solely for the purpose of improving a software system meant to classify file types does not fall under fair use?

https://en.wikipedia.org/wiki/Fair_use

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beeboobaa 852 days ago
I'm asking a question.

Here's another one for you: Do you believe that all pictures you have ever taken, all emails you have ever written, all code you have ever written could be posted here on this forum to improve someone else's software system?

If so, could you go ahead and post that zip? I'd like to ingest it in my model.

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westurner 852 days ago
What is the MIME type of a .tar file; and what are the MIME types of the constituent concatenated files within an archive format like e.g. tar?

hachoir/subfile/main.py: https://github.com/vstinner/hachoir/blob/main/hachoir/subfil...

File signature: https://en.wikipedia.org/wiki/File_signature

PhotoRec: https://en.wikipedia.org/wiki/PhotoRec

"File Format Gallery for Kaitai Struct"; 185+ binary file format specifications: https://formats.kaitai.io/

Table of ': https://formats.kaitai.io/xref.html

AntiVirus software > Identification methods > Signature-based detection, Heuristics, and ML/AI data mining: https://en.wikipedia.org/wiki/Antivirus_software#Identificat...

Executable compression; packer/loader: https://en.wikipedia.org/wiki/Executable_compression

Shellcode database > MSF: https://en.wikipedia.org/wiki/Shellcode_database

sigtool.c: https://github.com/Cisco-Talos/clamav/blob/main/sigtool/sigt...

clamav sigtool: https://www.google.com/search?q=clamav+sigtool

https://blog.didierstevens.com/2017/07/14/clamav-sigtool-dec... :

  sigtool –-find-sigs "$name" | sigtool –-decode-sigs
List of file signatures: https://en.wikipedia.org/wiki/List_of_file_signatures

And then also clusterfuzz/oss-fuzz scans .txt source files with (sandboxed) Static and Dynamic Analysis tools, and `debsums`/`rpm -Va` verify that files on disk have the same (GPG signed) checksums as the package they are supposed to have been installed from, and a file-based HIDS builds a database of file hashes and compares what's on disk in a later scan with what was presumed good, and ~gdesktop LLM tools scan every file, and there are extended filesystem attributes for label-based MAC systems like SELinux, oh and NTFS ADS.

A sufficient cryptographic hash function yields random bits with uniform probability. DRBG Deterministic Random Bit Generators need high entropy random bits in order to continuously re-seed the RNG random number generator. Is it safe to assume that hashing (1) every file on disk, or (2) any given file on disk at random, will yield random bits with uniform probability; and (3) why Argon2 instead of e.g. only two rounds of SHA256?

https://github.com/google/osv.dev/blob/master/README.md#usin... :

> We provide a Go based tool that will scan your dependencies, and check them against the OSV database for known vulnerabilities via the OSV API. ... With package metadata, not (a file hash, package) database that could be generated from OSV and the actual package files instead of their manifest of already-calculated checksums.

Might as well be heating a pool on the roof with all of this waste heat from hashing binaries build from code of unknown static and dynamic quality.

Add'l useful formats:

> Currently it is able to scan various lockfiles, debian docker containers, SPDX and CycloneDB SBOMs, and git repositories

Things like bittorrent magnet URIs, Named Data Networking, and IPFS are (file-hash based) "Content addressable storage": https://en.wikipedia.org/wiki/Content-addressable_storage

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dieortin 851 days ago
I’m not sure what this comment is trying to say
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westurner 851 days ago
File-based hashing is done is so many places, there's so much heat.

Sub- file-based hashing with feature engineering is necessary for AV, which must take packing, obfuscating, loading, and dynamic analysis into account in addition to zip archives and magic file numbers.

AV AntiVirus applications with LLMs: what do you train it on, what are some of the existing signature databases.

https://SigStore.dev/ (The Linux Foundation) also has a hash-file inverted index for released artifacts.

Also otoh with a time limit,

1. What file is this? Dirname, basename, hashes(s)

2. Is it supposed to be installed at such path?

3. Per it's header, is the file an archive or an image or a document?

4. What file(s) and records and fields are packed into a file, and what transforms were the data transformed with?

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