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Various formatting fixes

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Marek Marczykowski-Górecki 2024-05-21 16:36:00 +02:00
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developer/services/dom0-secure-updates.md
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@ -33,11 +33,11 @@ Keeping Dom0 not connected to any network makes it hard, however, to provide upd
The update process is initiated by [qubes-dom0-update script](https://github.com/QubesOS/qubes-core-admin-linux/blob/release2/dom0-updates/qubes-dom0-update), running in Dom0.
Updates (\*.rpm files) are checked and downloaded by UpdateVM, which by default is the same as the firewall VM, but can be configured to be any other, network-connected VM. This is done by [qubes-download-dom0-updates.sh script](https://github.com/QubesOS/qubes-core-agent-linux/blob/release2/misc/qubes-download-dom0-updates.sh) (this script is executed using qrexec by the previously mentioned qubes-dom0-update). Note that we assume that this script might get compromised and fetch maliciously compromised downloads -- this is not a problem as Dom0 verifies digital signatures on updates later. The downloaded rpm files are placed in a ~~~/var/lib/qubes/dom0-updates~~~ directory on UpdateVM filesystem (again, they might get compromised while being kept there, still this isn't a problem). This directory is passed to yum using the ~~~--installroot=~~~ option.
Updates (`*.rpm` files) are checked and downloaded by UpdateVM, which by default is the same as the firewall VM, but can be configured to be any other, network-connected VM. This is done by [qubes-download-dom0-updates.sh script](https://github.com/QubesOS/qubes-core-agent-linux/blob/release2/misc/qubes-download-dom0-updates.sh) (this script is executed using qrexec by the previously mentioned qubes-dom0-update). Note that we assume that this script might get compromised and fetch maliciously compromised downloads -- this is not a problem as Dom0 verifies digital signatures on updates later. The downloaded rpm files are placed in a ~~~/var/lib/qubes/dom0-updates~~~ directory on UpdateVM filesystem (again, they might get compromised while being kept there, still this isn't a problem). This directory is passed to yum using the ~~~--installroot=~~~ option.
Once updates are downloaded, the update script that runs in UpdateVM requests an RPM service [qubes.ReceiveUpdates](https://github.com/QubesOS/qubes-core-admin-linux/blob/release2/dom0-updates/qubes.ReceiveUpdates) to be executed in Dom0. This service is implemented by [qubes-receive-updates script](https://github.com/QubesOS/qubes-core-admin-linux/blob/release2/dom0-updates/qubes-receive-updates) running in Dom0. The Dom0's qubes-dom0-update script (which originally initiated the whole update process) waits until qubes-receive-updates finished.
The qubes-receive-updates script processes the untrusted input from Update VM: it first extracts the received \*.rpm files (that are sent over qrexec data connection) and then verifies digital signature on each file. The qubes-receive-updates script is a security-critical component of the Dom0 update process (as is the [qfile-dom0-unpacker.c](https://github.com/QubesOS/qubes-core-admin-linux/blob/release2/dom0-updates/qfile-dom0-unpacker.c) and the rpm utility, both used by the qubes-receive-updates for processing the untrusted input).
The qubes-receive-updates script processes the untrusted input from Update VM: it first extracts the received `*.rpm` files (that are sent over qrexec data connection) and then verifies digital signature on each file. The qubes-receive-updates script is a security-critical component of the Dom0 update process (as is the [qfile-dom0-unpacker.c](https://github.com/QubesOS/qubes-core-admin-linux/blob/release2/dom0-updates/qfile-dom0-unpacker.c) and the rpm utility, both used by the qubes-receive-updates for processing the untrusted input).
Once qubes-receive-updates finished unpacking and verifying the updates, the updates are placed in ``qubes-receive-updates`` directory in Dom0 filesystem. Those updates are now trusted. Dom0 is configured (see /etc/yum.conf in Dom0) to use this directory as a default (and only) [yum repository](https://github.com/QubesOS/qubes-core-admin-linux/blob/release2/dom0-updates/qubes-cached.repo).