[Replicant] backup stock ROM without root

[Fil Lupin]

Hello,
After searching, I did not find any method working on all devices to allow to backup a device's partitions without flashing it to get root.
Moreover, I found several posts assuring this is not possible for GT-I9300 (see B.6. in https://forum.xda-developers.com/showthread.php?t=723596).

On GT-I9300 (Samsung Galaxy S3), it seems the only way to get root is to flash recovery partition.
First step should then be to get a recovery partition which will not harm the device before installing it on device.
What I mean here is one should not only checking integrity of the downloaded file by checking MD5 signature but also checking that recovery partition will do what it is made for and only this.
In my point of view, this is exactly the same logic behind using libre software: to get maximum control on what the device can do.

Some websites allow to download firmware but I do not know how to guaranty those firmware authenticity.
Since I am not an expert, I hope someone can let me know how to do this.

Another way to get flash recovery and get root could be to boot a temporary recovery on SDCard as suggested by Kurtis Hanna. I did not test this solution.
Since the goal is just to get a recovery partition dump, one could then flash the recovery partition with TWRP (https://www.xda-developers.com/how-to-install-twrp/ and https://www.xda-developers.com/how-to-install-twrp/) which is GPL (https://github.com/omnirom/android_bootable_recovery/).

- Fil Lupin.