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Simple (not one-click) root for stock ROM & kernel

Update: One click root has been using this "simple" method since version 2.2.7. If you're rooting your phone for the first time, please try that first. Consider this thread to be purely informational for those who want step-by-step details of how the process works.
I've been suspicious of the joeykrim root method since it was first posted at SDX. I finally got my Epic yesterday and confirmed that is, indeed unnecessary. I don't fault joeykrim though, he ported the working root method from the Moment to the Epic without actually having access to an Epic himself.
Anyways, the joeykrim root method is unnecessarilly complex becuase it works around an RFS permissions bug which loses the setuid bit on the Moment. It appears the Galaxy S phones have this bug fixed, which is why the root methods on the I9000, Vibrant, Captivate, Fascinate, etc., are much simpler.
So, for the simple root:
First, make sure joeykrim root is not installed.
Upgrade to DI18 (not strictly necessary, but you'll want to do it).
Setup a working adb from the Android SDK and whatever drivers are necessary for your platform.
Download rageagainstthecage-arm5.bin from the C skills blog (link removed due to my newbieness) or from any of the one-click root packages.
Download su-2.3.6.1-ef-signed.zip and extract "system/bin/su" and "system/app/Superuser.apk" to a temporary directory you'll be working from.
Enable USB debugging on your phone and connect it to your computer.
Now, open a command prompt/shell on your computer and cd to the appropriate temporary directory. Run:
Code:
adb push rageagainstthecage-arm5.bin /data/local/tmp
adb shell chmod 755 /data/local/tmp/rageagainstthecage-arm5.bin
adb shell /data/local/tmp/rageagainstthecage-arm5.bin
and confirm you have a working root shell. Then continue with:
Code:
adb push su /system/xbin
adb shell chmod 4755 /system/xbin/su
adb install Superuser.apk
That's it! You should have a working root via su & the Superuser package. At least, I did.
Note that the preceeding steps installs Superuser.apk to /data, which is what I prefer to do. This means if you do a "Factory data reset" su will be temporarilly broken until you reinstall the Superuser.apk package. Since installing the package itself doesn't require root, this is easily done after a /data reset.
Also note that I did not perform a /system remount-rw anywhere. At least on my Epic, /system appears to always be mounted read-write so it's an unnecessary step. It's actually the "joeykrim-root.sh" script that remounts /system read-only during the boot process, which is why folks who don't use root kernels have run into this problem before. I'm not sure why joeykrim's script does that, I guess he probably assumed /system is mounted read-only by default. There's arguments that /system should be read-only, but I didn't touch it in case some Samsung stuff depends on it being read-write.
Finally, if you're already rooted via joeykrim or are running a root kernel, there's nothing really to be gained by doing this. I'm just throwing this out there as I perfer to make the minimum invasive changes possible to obtain root.

Wow, that was really informative. To check for Super user you:
Type: adb shell
then type: SU
You should get a # sign if you have root. Correct?
In the original Noobln post method would the Epic keep root even after a wipe therefore not needing to re-apply the superuser apk again? That might be a reason why folks would want to go the more invasive route (considering rooters seems to change ROMS fairly often which requires wipes sometimes). Either way, keeping a copy of the apk file on your SD card is no big deal.

mkasick said:
Also note that I did not perform a /system remount-rw anywhere. At least on my Epic, /system appears to always be mounted read-write so it's an unnecessary step. It's actually the "joeykrim-root.sh" script that remounts /system read-only during the boot process, which is why folks who don't use root kernels have run into this problem before. I'm not sure why joeykrim's script does that, I guess he probably assumed /system is mounted read-only by default. There's arguments that /system should be read-only, but I didn't touch it in case some Samsung stuff depends on it being read-write.
Click to expand...
Click to collapse
This explains a lot of problems! thanks
EDIT- another noob question- why do you prefer to have superuser installed to /system/data- why not put it in /system/app? Also if I want to install busybox where is the best location to put it?

ZenInsight said:
Wow, that was really informative. To check for Super user you:
Type: adb shell
then type: SU
You should get a # sign if you have root. Correct?
Click to expand...
Click to collapse
Once you run rageagainstthecage-arm5.bin, you should get a root-shell automatically every time you run "adb shell" after until you reboot the phone. Yes, you can tell it's a root shell since it uses the "#" prompt. This is the important part to check, since if the exploit doesn't work, you'll have to run it again. But I haven't seen it not work.
After su is installed and you reboot, your steps are correct: run "adb shell", run "su", then you'll be prompted on the phone scren to authorize access and once you allow it you'll end up with a "#" prompt.
ZenInsight said:
In the original Noobln post method would the Epic keep root even after a wipe therefore not needing to re-apply the superuser apk again?
Click to expand...
Click to collapse
noobnl installs Superuser.apk to /system, you can do that here too. Just replace the "adb install Superuser.apk" step with "adb push Superuser.apk /system/app". It's independent of the joeykrim scripts.

With my captivate we have many update.zip root methods to choose from. Any chance this will be coming to the epic? Have a friend with an epic and command lines would be too much and one click didn't work.
Sent from my SAMSUNG-SGH-I897 using XDA App

jimmyz said:
why do you prefer to have superuser installed to /system/data- why not put it in /system/app?
Click to expand...
Click to collapse
I prefer to keep consistent with the idea that user-installed applications go in /data, and stock-installed-and-unmodified applications remain in /system/app. This way, upgrading Superuser.apk doesn't require a root-shell/root-explorer, you can remove it or upgrade it the way you do with any user installed application--adb install, side-loading via an sdcard, or downloading it from the market.
Plus, in general I prefer to keep my /system as untouched as possible. For example, I don't remove stock apps either. The "su" binary has to be installed in /system to persist after a /data wipe, and busybox is best installed to /system so it's in PATH (haven't looked into modifying the default PATH yet). Otherwise I try to keep /system alone.
jimmyz said:
Also if I want to install busybox where is the best location to put it?
Click to expand...
Click to collapse
Android's default PATH provides four places for busybox to be installed: /sbin, /system/bin, /system/sbin, and /system/xbin. /sbin is part of the initramfs, in other words it's controlled by the kernel you're running. You can install busybox to any of the three /system/*bin directories, but I prefer /system/xbin.
In the traditional Unix conventions, "/usr/bin" is for user-runnable stock-installed programs, and "/usr/sbin" is for root-requiring (superuser-runnable) stock-installed programs. "xbin" isn't part of the standard convention, but I'd guess it's intended for "extra binaries" that are not part of the stock installation (much like /usr/local/bin), thus it seems like an appropriate location for a user-added "su" and "busybox" programs.
The second reason is that "xbin" is relatively empty, so if you want to create the applet symlinks (i.e., so that you can call "cp" instead of "buybox cp") it won't overwrite the stock toolbox symlinks. Also, since "xbin" is last on the default PATH, any programs provided by both toolbox and busybox will default to the toolbox version--which would be important for stock system scripts that might run into compatibility issues if they were to use the busybox versions instead.
To install busybox, grab a copy of the binary from somewhere (one click packages, a copy of stericson.busybox.apk, etc.). Then, once rooted run:
Code:
adb push busybox /data/local/tmp
adb shell
su # Authorize on phone screen
cat /data/local/tmp/busybox > /system/xbin/busybox
chown root.shell /system/xbin/busybox
chmod 755 /system/xbin/busybox
rm /data/local/tmp/busybox
/system/xbin/busybox --install -s /system/xbin

jhnstn00 said:
With my captivate we have many update.zip root methods to choose from. Any chance this will be coming to the epic?
Click to expand...
Click to collapse
I don't believe so. The I9000/Vibrant/Captivate have recoveries that don't check the signature of update.zip (as I understand, or maybe they do but only require test keys) which makes rooting-via-recovery possible. Unfortuntaely the Epic and Fascinate do perform signature checks, so we can't enable root via stock-recovery.
That said, the Fascinate one-click methods should also work on the Epic. Although depending on why your friend couldn't get the Epic one-click to work, the Fascinate one may not work either.

mkasick said:
I prefer to keep consistent with the idea that user-installed applications go in /data, and stock-installed-and-unmodified applications remain in /system/app. This way, upgrading Superuser.apk doesn't require a root-shell/root-explorer, you can remove it or upgrade it the way you do with any user installed application--adb install, side-loading via an sdcard, or downloading it from the market.
Plus, in general I prefer to keep my /system as untouched as possible. For example, I don't remove stock apps either. The "su" binary has to be installed in /system to persist after a /data wipe, and busybox is best installed to /system so it's in PATH (haven't looked into modifying the default PATH yet). Otherwise I try to keep /system alone.
Android's default PATH provides four places for busybox to be installed: /sbin, /system/bin, /system/sbin, and /system/xbin. /sbin is part of the initramfs, in other words it's controlled by the kernel you're running. You can install busybox to any of the three /system/*bin directories, but I prefer /system/xbin.
In the traditional Unix conventions, "/usr/bin" is for user-runnable stock-installed programs, and "/usr/sbin" is for root-requiring (superuser-runnable) stock-installed programs. "xbin" isn't part of the standard convention, but I'd guess it's intended for "extra binaries" that are not part of the stock installation (much like /usr/local/bin), thus it seems like an appropriate location for a user-added "su" and "busybox" programs.
The second reason is that "xbin" is relatively empty, so if you want to create the applet symlinks (i.e., so that you can call "cp" instead of "buybox cp") it won't overwrite the stock toolbox symlinks. Also, since "xbin" is last on the default PATH, any programs provided by both toolbox and busybox will default to the toolbox version--which would be important for stock system scripts that might run into compatibility issues if they were to use the busybox versions instead.
To install busybox, grab a copy of the binary from somewhere (one click packages, a copy of stericson.busybox.apk, etc.). Then, once rooted run:
Code:
adb push busybox /data/local/tmp
adb shell
su # Authorize on phone screen
cat /data/local/tmp/busybox > /system/xbin/busybox
chown root.shell /system/xbin/busybox
chmod 755 /system/xbin/busybox
rm /data/local/tmp/busybox
/system/xbin/busybox --install -s /system/xbin
Click to expand...
Click to collapse
You sir are a true gentleman! Thank you for the informative answers- its great to have you over here! I have one more question- why can't I usually push directly to /system ?

jimmyz said:
why can't I usually push directly to /system ?
Click to expand...
Click to collapse
Pushing directly to /system requires running the adb service on the phone as the root user, so that it has permissions to write to that directory. Usually adb runs on the phone unprivileged, so you can only push to world-writable directories.
Running rageagainstthecage-arm5.bin actually changes this. The exploit forces the adb service to run as the root user, which is why "adb shell" gives you a root shell and "adb push" to /system does work, until the phone is restarted.
Interesting enough, the adb service also runs as root by default in the Android emulator. So there's probably a configuration setting, somewhere, to make it do that. In general it's safer to run adb unprivileged though, and "su" to move files to /system once uploaded elsewhere on the phoe.

mkasick said:
Pushing directly to /system requires running the adb service on the phone as the root user, so that it has permissions to write to that directory. Usually adb runs on the phone unprivileged, so you can only push to world-writable directories.
Running rageagainstthecage-arm5.bin actually changes this. The exploit forces the adb service to run as the root user, which is why "adb shell" gives you a root shell and "adb push" to /system does work, until the phone is restarted.
Interesting enough, the adb service also runs as root by default in the Android emulator. So there's probably a configuration setting, somewhere, to make it do that. In general it's safer to run adb unprivileged though, and "su" to move files to /system once uploaded elsewhere on the phoe.
Click to expand...
Click to collapse
I am learning a lot!!! Could you take a look at koush's kernel here, with it I noticed that when using adb I got the # prompt right away and was able to push to /system- maybe he was able to figure out the config settings? Once again thanks!!!
one more ? (feel free to ignore this one) what actually happens when you do
Code:
adb shell /data/local/tmp/rageagainstthecage-arm5.bin
and how does that give you permanent root?

mkasick said:
Pushing directly to /system requires running the adb service on the phone as the root user, so that it has permissions to write to that directory. Usually adb runs on the phone unprivileged, so you can only push to world-writable directories.
Running rageagainstthecage-arm5.bin actually changes this. The exploit forces the adb service to run as the root user, which is why "adb shell" gives you a root shell and "adb push" to /system does work, until the phone is restarted.
Interesting enough, the adb service also runs as root by default in the Android emulator. So there's probably a configuration setting, somewhere, to make it do that. In general it's safer to run adb unprivileged though, and "su" to move files to /system once uploaded elsewhere on the phoe.
Click to expand...
Click to collapse
It is indeed a config option in default.prop. However, this is in the initramfs and you can't change it on the fly, so you need to rebuild the kernel to change it. With some work you can modify the stock kernel to do it, but I personally haven't tried it.
Sent from my Epic 4G using XDA App

Thank you, this worked perfectly for me, running stock DI18 ROM that I flashed tonight!!! I confirmed by installing the wireless tethering pre-9 apk, and successfully ran the wireless tethering without any errors.
Quick question: do we need to do this after root or is it not needed?
NEEDED?? ===> SuperUser App to help with Security Concerns for the Epic - h**p://forum.sdx-developers.com/epic-development/superuser-app-to-help-with-security-concerns/
Also, Titanium Backup failed to work - it gave an error of denied root access, and said busybox was not installed. What needs to be done to make it work? Do I need to install clockwork mod (not exactly sure what it does though) or a custom ROM?

AndroidSPCS said:
Quick question: do we need to do this after root or is it not needed?
Click to expand...
Click to collapse
Not sure exactly what you're asking. This is an alternative to the joeykrim-based one-click roots and rooted kernels. If you already have one of those this isn't really necessary.
AndroidSPCS said:
NEEDED?? ===> SuperUser App
Click to expand...
Click to collapse
Yes, the su binary used here requires the Supruser appto be installed to authorize su requests. Otherwise they'll always be denied. Other su binaries might not require it, but then all apps have root access which isn't really a good thing.
AndroidSPCS said:
Also, Titanium Backup failed to work - it gave an error of denied root access, and said busybox was not installed. What needs to be done to make it work?
Click to expand...
Click to collapse
Did you authorize Titanium Backup when the Superuser prompt came up (requies the Superuser app to be instald too)?
Titanium Backup has an option to download and install it's preferred version of busybox. Follow the prompts to do that.

mkasick said:
Not sure exactly what you're asking. This is an alternative to the joeykrim-based one-click roots and rooted kernels. If you already have one of those this isn't really necessary.
Click to expand...
Click to collapse
Thanks, actually this was referring to the thread where the instructions for going to adb shell or terminal and typing in the following commands:
adb shell
su
mount -t rfs -o remount,rw /dev/block/stl9 /system
cp /system/bin/su /system/bin/jk-su
exit
Yes, the su binary used here requires the Supruser appto be installed to authorize su requests. Otherwise they'll always be denied. Other su binaries might not require it, but then all apps have root access which isn't really a good thing.
Click to expand...
Click to collapse
Yes same as above, the question is not whether we need SU app (I know we do), but whether we needed to type the additional commands:
adb shell
su
mount -t rfs -o remount,rw /dev/block/stl9 /system
cp /system/bin/su /system/bin/jk-su
exit
What do these commands do? It seems to me my Superuser app is working fine with wifi tether - popping up with allow / disable permission boxes, etc. Do these commands add something else to Superuser?
Did you authorize Titanium Backup when the Superuser prompt came up (requies the Superuser app to be instald too)?
Titanium Backup has an option to download and install it's preferred version of busybox. Follow the prompts to do that.
Click to expand...
Click to collapse
There was no Superuser prompt during the install of the app, nor anytime when it said it had a failure with root access. However there is an option to install BusyBox, which I have not done yet, because I am not sure what busybox is, or what it does. I'd like to find out why I need it and what it does, so I can feel comfortable with installing it.
Thanks again.

echo "root::0:0:root:/data/local:/system/bin/sh" > /etc/passwd
echo "root::0:" > /etc/group
you need to do that in a shell to make sure su works properly.
I'm updating the one click root right now to be less silly.

http://forum.xda-developers.com/showpost.php?p=8543226&postcount=455
I just cleaned up the one click root to not do many of the silly things joeykrim's root does. It also means your system will be mounted as rw after a reboot and it won't overwrite your su with jk-su every boot (no more modified playlogo).
Cleaned up all the old stuff from the root so it should work fine even if you were using one of the older one clicks. I made sure su works, incl titanium backup.
I'm still installing superuser.apk to /system/app because I think it belongs there.
Thanks for doing the footwork, mkasick!

Firon said:
http://forum.xda-developers.com/showpost.php?p=8543226&postcount=455
I just cleaned up the one click root to not do many of the silly things joeykrim's root does. It also means your system will be mounted as rw after a reboot and it won't overwrite your su with jk-su every boot (no more modified playlogo).
Cleaned up all the old stuff from the root so it should work fine even if you were using one of the older one clicks. I made sure su works, incl titanium backup.
I'm still installing superuser.apk to /system/app because I think it belongs there.
Thanks for doing the footwork, mkasick!
Click to expand...
Click to collapse
Firon- why are these lines still needed?
Code:
adb push playlogo /system/bin/playlogo
what is playlogo? Does this just put the stock one back in case you used the joeykrim method in the past?
Code:
adb push remount /system/xbin/remount
Are the remount scripts still needed?
Code:
adb shell ln -s /system/xbin/su /system/bin/su
why is this link needed? why cant su just be in xbin
thanks in advance!
Code:

jimmyz said:
Firon- why are these lines still needed?
Code:
adb push playlogo /system/bin/playlogo
what is playlogo? Does this just put the stock one back in case you used the joeykrim method in the past?
Click to expand...
Click to collapse
This is just pushing the stock playlogo, since joeykrim's method overwrites it with some custom script.
Code:
adb push remount /system/xbin/remount
Are the remount scripts still needed?
Click to expand...
Click to collapse
The script allows you to easily remount system as ro or rw at will. Why not?
Code:
adb shell ln -s /system/xbin/su /system/bin/su
why is this link needed? why cant su just be in xbin
Click to expand...
Click to collapse
I don't know if any apps depend on it being in a particular location. It is in xbin, but I'm also linking it to /system/bin to be safe.

AndroidSPCS said:
What do these commands do? It seems to me my Superuser app is working fine with wifi tether - popping up with allow / disable permission boxes, etc. Do these commands add something else to Superuser?
Click to expand...
Click to collapse
These commands were necessary to get Superuser working with the old joeykrim root method. They're not necessary with this method (or the newly released one-click). In other words, if wifi-tethering is already working for you, nothing further is needed to be done.
AndroidSPCS said:
There was no Superuser prompt during the install of the app, nor anytime when it said it had a failure with root access.
Click to expand...
Click to collapse
I don't actually use TitaniumBackup. I'm not sure why its superuser-requirements would be different from other apps, but I guess it is. The new one-click appears to address this.
AndroidSPCS said:
However there is an option to install BusyBox, which I have not done yet, because I am not sure what busybox is, or what it does. I'd like to find out why I need it and what it does, so I can feel comfortable with installing it.
Click to expand...
Click to collapse
Busybox is a suite of "familar" Unix command-line utilites (things like cp (copy), mv (move), ls (list), etc.). It targets embedded platforms by being very featureful, yet relatively small. It's installed and used on a wide variety of embedded devices including wireless routers, print servers, phones, even televisions.
Oddly enough, Android does not include busybox by default. Instead it comes with it's own utility-programs-package called "toolbox" that isn't nearly as featureful, and quickly becomes a pain to use. Some programs, like TitaniumBackup depend on busybox programs/features, and thus require it's installation. It's safe.
The only problem with busybox is that there's not one single version of it. There's multiple builds of it from the same source code with different sets of features turned on and off. In the past, some folks had a version of busybox installed that didn't contain all the features necessary to support TitaniumBackup, so they added the option to install their own version. It's installed in a separate location, so it won't overwrite any version you do have installed, and it's safe to do. But if you've already installed another version of busybox that does work, then it may be unnecessary.

I did the Jokeyrim method a few days ago. I installed a new kernal and now a new ROM. All seems ok, but ow when I do the "whoami" command in adb shell I get whoami not found. I don't think I'm really rooted anymore. Any attempt to reinstall the Jokeyrim root script results in failure (mostly "device not found" errors). When in adb shell, most commands I type now are either "not found" or "permission denied", so I'm not confident that I'm really rooted now.
Since I have / had Jokeyrim installed, how can I "uninstall" it so that I can use this method of rooting instead? BTW, the newest Clockworkmod is installed and working.
Do I need to flash to stock first? Sorry, but I'm a VERY STOOPID NOOB.

[GUIDE] get root!

Hi all,
this thread would like to be a shortly introduction about root user permission on general android platform!
As we all know the root user in Unix-based OS is the user with UID equal to 0.
Many threads talks about gain root on android by means of magic oneclick tool or by way of flashing custom recovery on device then copy the fantastic ChainsDD's su binary and install superuser or another apk to manage privileged action request .
Do we really need? Probably! But we maybe only want a root prompt, root privilege through adb shell or on the terminal emulator, this is certainly possible.
Deafult android shell is /system/bin/sh, if we could run it through, for example, an executable owned by user with UID 0, and if there was a Unix access rights flags that allow users to run an executable with the permissions of the executable's owner, we probably would get a root shell only by running that executable! Easy!
Only one thing, we should know a method for push our unsecure setuidded executable owned by root under the /system/xbin directory, which is also owned by root!
For example, might be possible to dump our /system, mount the filesystem data on a Linux box (which we know the root password), copy the unsecure elf under the correct path, and then flash back the modified /system image to our device, all with the original bootloader, without any custom recovery.
Once done, if we run the executable, ta daaan....
If someone wants to get his hands dirty:
Code:
void main()
{
setuid(0);
system("/system/bin/sh");
}
this can be enough!

Anyone...?

Dirty Cow

Just wondering if the new Dirty Cow exploit means all those previously unrootable phones can now (or very soon) be rooted.
http://www.cyberciti.biz/faq/dirtyc...local-privilege-escalation-vulnerability-fix/

kennonk said:
Just wondering if the new Dirty Cow exploit means all those previously unrootable phones can now (or very soon) be rooted.
http://www.cyberciti.biz/faq/dirtyc...local-privilege-escalation-vulnerability-fix/
Click to expand...
Click to collapse
Based upon the early research into this, YES it would appear that this also has widespread affect into the Android Linux Kernel
https://www.nowsecure.com/blog/2016/10/21/dirty-cow-vulnerability-mobile-impact/
https://www.theguardian.com/technol...ow-linux-vulnerability-found-after-nine-years
(Bottom of Article Google confirms Android is susceptible)
PoC Code which would probably need to be slightly refactored for use in Android, but still highly relevant
https://github.com/dirtycow/dirtycow.github.io/wiki/PoCs

The bug affects the Android Linux kernel. I already tested it, and yes, you can change any file owned by root to whatever you want.
But that doesn't mean you can actually root the phone (that is, gain root access). Maybe it is possible, but I don't think is trivial. The thing is: you can modify root owned files, yes. But you need that some process owned by root executes your file, so you can gain root access. Editing init scripts won't work since they are recreated every time you boot your phone, and after the phone boots, as far as I know, nothing else is executed by root.
I don't mean that it can't be done, maybe there's some file that is executed by root after boot out there that you can modify, but I wouldn't know which one.

Scorpius666 said:
The thing is: you can modify root owned files, yes. But you need that some process owned by root executes your file, so you can gain root access.
Click to expand...
Click to collapse
Doesn't that mean you can install a custom su binary and just execute that as any user?

This exploit only allows you to replace the content of existing files with their existing mode/permissions, and the way su operates you need the setuid (set-user-ID) bit set in the mode, and from a brief look at the system I wanted to get root on, android doesn't seem to have any setuid binaries.
I'm thinking replacing something like wpa_supplicant could let us execute the payload as root, just disable and re-enable wifi, but I can't seem to get the exploit itself to work at the moment.
On further inspection (at least on this device), wpa_supplicant isn't readable by non-root (which I think the exploit requires). app_process is, but that's an executable I'd prefer not to mess with
Update:
Got the exploit itself working.
Tried replacing /system/bin/fsck_msdos's content to trigger it to be run as root by inserting a microSD card,
but something on this device (Amazon Fire 5th gen) keeps rebooting and restoring the system partition if any file is changed.

a___ said:
This exploit only allows you to replace the content of existing files
Click to expand...
Click to collapse
Not true. This code executes su as root, spawning a root shell. It can be modified to run a script that installs su in/system etc..
The counterside is that the kernel crashes/freezes after some seconds.
https://gist.github.com/scumjr/17d91f20f73157c722ba2aea702985d2
I'd like to port that to an apk using the ndk, but my pc is too old.

The /system partition is mounted read only by default. Because of this, you can't overwrite them. But I saw a exploit which used /sys/kernel/uevent_helper to execute a shell script as root. This would probably also work with the dirty cow exploit.

KillahKiwi said:
Doesn't that mean you can install a custom su binary and just execute that as any user?
Click to expand...
Click to collapse
You can't create a new file. You can modify an existing file. The su binary needs the setuid bit and there are no files in the Android filesystem with that bit set.
The only way to root a phone with this bug is to modify an executable that will change the owner of the su binary to root and set the setuid bit on this file. This part is trivial and very easy.
The difficult part is to find a binary that will be executed as root after you have booted. If somebody knows any file in /system/bin for example that will be executed as root doing some action on the phone tell me and the phone will be rooted in seconds.
---------- Post added at 11:32 AM ---------- Previous post was at 11:28 AM ----------
a___ said:
Got the exploit itself working.
Tried replacing /system/bin/fsck_msdos's content to trigger it to be run as root by inserting a microSD card,
but something on this device (Amazon Fire 5th gen) keeps rebooting and restoring the system partition if any file is changed.
Click to expand...
Click to collapse
I copied the su binary in /data/local/tmp. I can modify files in /system/bin for example and the phone does not reboot, but i don't have fsck_msdos in my phone.
---------- Post added at 11:35 AM ---------- Previous post was at 11:32 AM ----------
DP FH said:
Not true. This code executes su as root, spawning a root shell. It can be modified to run a script that installs su in/system etc..
The counterside is that the kernel crashes/freezes after some seconds.
https://gist.github.com/scumjr/17d91f20f73157c722ba2aea702985d2
I'd like to port that to an apk using the ndk, but my pc is too old.
Click to expand...
Click to collapse
I'm compiling on the phone using UXTerm, then apt install clang, and then using gcc. It's the quickest way to compile a single .c file on it.

Scorpius666 said:
. It's the quickest way to compile a single .c file on it.
Click to expand...
Click to collapse
I'd like to create a standard Android app that uses jni to run exploit and then roots the device. I can't test on my real phone because I need warranty and Knox counter to 0.

DP FH said:
Not true. This code executes su as root, spawning a root shell. It can be modified to run a script that installs su in/system etc..
The counterside is that the kernel crashes/freezes after some seconds.
https://gist.github.com/scumjr/17d91f20f73157c722ba2aea702985d2
I'd like to port that to an apk using the ndk, but my pc is too old.
Click to expand...
Click to collapse
At first try doesn't work for me:
Code:
[email protected]:/data/local/tmp $ ./dirtyc0w-mem b6dc0000 b6dc1000
[*] range: b6dc0000-b6dc1000]
[*] getuid = b6f79b18
[*] mmap 0xb6dd5000
[*] exploiting (patch)
./dirtyc0w-mem: failed to execute "su": Permission denied
[*] exploiting (unpatch)
[*] unpatched: uid=2000 (madviseThread)
[*] unpatched: uid=2000 (procselfmemThread)
But I'll modify a little bit to see if I can get it to work.

Scorpius666 said:
doesn't work for me.
Click to expand...
Click to collapse
I don't think you have su on the phone ????
By the way I'm trying to install some emulator on my pc so I can try

DP FH said:
I don't think you have su on the phone ????
By the way I'm trying to install some emulator on my pc so I can try
Click to expand...
Click to collapse
I do have the su, in /data/local/tmp, with users permission. The idea is to do a chown root:root and a chmod 4755.
But I know what the problem is. The SHELLCODE in the file is for x86, which seems to be a XOR AX, AX and a RET. I have to do the same for an ARM v7L in THUMB I think...

DP FH said:
Not true. This code executes su as root, spawning a root shell. It can be modified to run a script that installs su in/system etc..
The counterside is that the kernel crashes/freezes after some seconds.
<URL>
I'd like to port that to an apk using the ndk, but my pc is too old.
Click to expand...
Click to collapse
Well that assumes we have a setuid su already, this variant of the exploit won't help us.
julianwi said:
The /system partition is mounted read only by default. Because of this, you can't overwrite them. But I saw a exploit which used /sys/kernel/uevent_helper to execute a shell script as root. This would probably also work with the dirty cow exploit.
Click to expand...
Click to collapse
Somehow it did manage to overwrite it, but maybe the reboot and reset are caused by it being read-only and not actually writing the changes to persistent storage.
Will look into /sys/kernel/uevent_helper though, thanks
Scorpius666 said:
...
I copied the su binary in /data/local/tmp. I can modify files in /system/bin for example and the phone does not reboot, but i don't have fsck_msdos in my phone.
...
Click to expand...
Click to collapse
Just about any would work, you probably have some other fsck or mkfs utility you could do it with, then trying to format an SD card should run mkfs

a___ said:
Just about any would work, you probably have some other fsck or mkfs utility you could do it with, then trying to format an SD card should run mkfs
Click to expand...
Click to collapse
The thing is all my fsck* files are not readable, only by root, at least in my device. The exploit needs a readable file.

a___ said:
Well that assumes we have a setuid su already, this variant of the exploit won't help us
Click to expand...
Click to collapse
Nope. The su command is executed as root, and when you execute su as root it gives you a root shell. Try to execute sh instead of su.

DP FH said:
Nope. The su command is executed as root, and when you execute su as root it gives you a root shell. Try to execute sh instead of su.
Click to expand...
Click to collapse
No, it merely makes libc report that the user is root even though it isn't, it needs su to already have setuid to switch to the real root, and then running the shell. In this case (simplified) the exploit just bypasses the password prompt.

a___ said:
No, it merely makes libc report that the user is root even though it isn't, it needs su to already have setuid to switch to the real root, and then running the shell. In this case (simplified) the exploit just bypasses the password prompt.
Click to expand...
Click to collapse
I just noticed that. Using sh instead of su, the dirtycow-mem works in the phone and it spawns a shell, but with the same privileges than the user that executed it. So it's useless at least with that libc approach.

Scorpius666 said:
I just noticed that. Using sh instead of su, the dirtycow-mem works in the phone and it spawns a shell, but with the same privileges than the user that executed it. So it's useless at least with that libc approach.
Click to expand...
Click to collapse
Strange, on normal x86 works like a charm so something needs to be fixed

DP FH said:
Strange, on normal x86 works like a charm so something needs to be fixed
Click to expand...
Click to collapse
Of course it works on x86. If you read the code you'll see that it changes the function getuid() of libc (that is already loaded in memory) to return 0. The x86 su binary uses getuid() to know if it should ask for a password or not. Since getuid() is patched, it doesn't ask a password and spawn a root shell.
So basically for dirtycow-mem to work you need:
A su binary with setuid root
That su binary should ask for a password
The Android su binary doesn't ask for a password and doesn't have the setuid root so this exploit won't work.

hey there
did anyone try the dirtycow-vdso exploit? it works on SELinux (which AOSP uses) and doesn't require a SUID see
github . com/scumjr/dirtycow-vdso

!!!Possible Perm Root Within Reach!!! 4-5-2019

I would like to share some info I have garnered from various forms of testing and such. I know a guy with a newer alcatel brazilian only model running android 6. We have been trying to get into the phone for a while. mtk-su was the way in to begin with. since it's a newer phone, it has decent security. system somehow gets mounted to zram so any changes made to system get erased at boot. System is ro and can't be changed perm as of yet. A script was created that basically spams mount system rw, which allows a few second gaps of system being rw, long enough to push some supersu files and start the daemon. Now, pushing strictly supersu files and then opening supersu will get the update binary request, which does not complete, and canceling the update still doesnt allow the installed su binary to work, so no temp root. Basically supersu is a no go. Now fast forward ahead a bit of time., and this is what the process is looking like.
Use mtk-su to grant ADB shell temp root
run the script for system rw from that temp root adb shell
squeeze the supersu files minus su to their locations using the small system rw gaps and also rename mtk-su to su and push that where it goes
give those pushed files correct permissions
start the su daemon
Temporary Paydirt!!
you now have temp root on a ro system, locked bootloader, all security in place. You are bypassing the need for supersu all together as you have temp root that doesnt ask for permission. any app that wants root gets it automatically.
that makes a guy wonder what flashfire would do, could you flash proper supersu that way and have it be systemless?
can you run selinux switch and have selinux be permissive
on a non zram system setup, could you gain perm root by not having system reloaded every time
could you somehow get to and mount the real system(location of real system is known: mblck25 or something) on a zram system setup and then gain perm root
Anyways, this is just something that's been banging around in my head, slowly spilling out, with small strides being made. Alot of testing still needs to be done, the process tweaked and refined and alot of sleepless nights i'm sure. Any thoughts, opinions, ideas, help is surely welcomed and needed. Once i have a dedicated tester on board and exhaust all possibilities and get the process to a good point, i'll release what I have. Until then, rest assured that I am doing what i can, for a phone i don;t own. The good thing is that this will potentially work on any device that mtk-su works on, which at this point is turning out to be a very decent amount of MTK devices

Mount /$y$tem a$ -rw
What i$ the $cript?

How do I temporarily root a samsung device running android 9 without twrp recovery?

I have used magisk to patch the file and android platform tools (fastboot or stuff like that) but it does not work. I dont want to install twrp as i dont really trust custom recoveries as much and i dont want to use odin for the same reason. Is this impossible or is there a way but i am just doing it incorrectly. Please reply asap!

Never installed Magisk nor TWRP, why should I have done it?
To answer your question: A temporary root can get achieved by putting a suitable su into directory /data/local/tmp and making it executable.
https://forum.xda-developers.com/attachments/su-binaries-zip.5566949/

xXx yYy said:
Never installed Magisk nor TWRP, why should I have done it?
To answer your question: A temporary root can get achieved by putting a suitable su into directory /data/local/tmp and making it executable.
https://forum.xda-developers.com/attachments/su-binaries-zip.5566949/
Click to expand...
Click to collapse
The data partition is not accessible without having root first. How are they to place su in data partition to gain temp root without first gaining root to place su in data partition? How can they root the device by using a method that requires root in the first place to achieve what you are telling them?

I think the code
Code:
adb push <PATH-TO-SU-ON-PC> /data/local/tmp
always works , because this path ( /data/local/tmp ) is always present and writable on Android dev device and Emulator.
At least it always worked for me since I'm rooting Android this way.

xXx yYy said:
I think the code
Code:
adb push <PATH-TO-SU-ON-PC> /data/local/tmp
always works , because this path ( /data/local/tmp ) is always present and writable on Android dev device and Emulator.
At least it always worked for me since I'm rooting Android this way.
Click to expand...
Click to collapse
do i unroot my device by rebooting it?
p.s. will doing this solution create a possibility of bricking my device?

Technically seen you can't root / unroot a device, but only Android OS.
As with Android OS root ( sometimes called superuser ) is the same as Administrator with Windows OS. Simply adding an user with elevated privileges never will brick an Android device.
Become familiar what root is the world of Linux OS - take note that Android OS merely is a port of it.

xXx yYy said:
Technically seen you can't root / unroot a device, but only Android OS.
As with Android OS root ( sometimes called superuser ) is the same as Administrator with Windows OS. Simply adding an user with elevated privileges never will brick an Android device.
Become familiar what root is the world of Linux OS - take note that Android OS merely is a port of it.
Click to expand...
Click to collapse
so running that command will give me legit root privileges and i can do the things an admin can do without any malware or damage?

Droidriven said:
The data partition is not accessible without having root first. How are they to place su in data partition to gain temp root without first gaining root to place su in data partition? How can they root the device by using a method that requires root in the first place to achieve what you are telling them?
Click to expand...
Click to collapse
so should i really use magisk to root my device?

moutsu said:
so should i really use magisk to root my device?
Click to expand...
Click to collapse
No, try what was suggested by placing su in the data/local/tmp. If that doesn't work, try using magisk to root your device.

xXx yYy said:
I think the code
Code:
adb push <PATH-TO-SU-ON-PC> /data/local/tmp
always works , because this path ( /data/local/tmp ) is always present and writable on Android dev device and Emulator.
At least it always worked for me since I'm rooting Android this way.
Click to expand...
Click to collapse
I've never seen a device rooted by such simple means, in my experience, it has always required root to even access data partition, especially if trying to push/pull files to/from data via adb.
I mean, if it were really that easy, why would all these rooting tools snd methods that exist on XDA have ever been needed to be created?
What devices have you rooted using this method? Can you provide information that explains and confirms what you say?

Hmmmm...
Short checked on my SM-R860 Android 11...
Code:
freshbs:/ $ cd /data/local/tmp
freshbs:/data/local/tmp $ ls
freshbs:/data/local/tmp $ ls -a1l
total 6
drwxrwx--x 2 shell shell 3452 2022-03-25 01:20 .
drwxr-x--x 4 root root 3452 2022-03-25 01:20 ..
Need more time or drinks to place something here...
Waiting for other results...
Best Regards

@Droidriven
Fellow member @adfree has proven that even with Android 11 directory /data/local/tmp worlwide exists and is writeable.
Sometimes it really makes sense to understand what OP wants to achieve: He just wants to know how Android can be temporarily rooted.

xXx yYy said:
@Droidriven
Fellow member @adfree has proven that even with Android 11 directory /data/local/tmp worlwide exists and is writeable.
Sometimes it really makes sense to understand what OP wants to achieve: He just wants to know how Android can be temporarily rooted.
Click to expand...
Click to collapse
I do need to know how an android can be temporarily rooted so I can give certain apps on my phone root access to recover some stuff I accidentally deleted. However, I do need a bit of clarification on what su file I need to put into the directory as the filed you linked was a zip file.
I would also like a method on how to unroot my device.

Dear moutsu...
IMHO instead blabla... IMHO it makes sense to start from scratch with FULL infos.
I can see only bla bla Samsung Device...
Please give full details...
A
Model Name...
Example:
SM-G920F is Android 7 for instance...
B
Is Phone alive... then give full details about Firmware Version.
Easiest way for most infos...
Type:
*#1234#
Type or make Photo or Screenshot...
Best Regards

@xXx yYy
Thank you very much. But...
I clicked through your profile and find some more puzzle parts of your idea...
Learning to root my old Galaxy S4
I have an old Samsung Galaxy S4. It's been off the network for a while and its system clock has drifted. However, adb works and I can use the old phone as a sandbox environment to learn about low level Android fundamentals. I would like to learn...
forum.xda-developers.com
After this I was drunken enough to try few things with my SM-R860...
WITHOUT success...
Later I will add my ADB output... for better understanding...
IMHO I am not total Noob in Rooting something...
Also I have "some" experiences in recover halfdead devices to backup beloved data...
I am sure you have forgotten about Samsung additional Security check... like Knox crap etc...
So my conclusion...
Your method is good to know...
But chance for success in "newer" Samsung devices is not 100 %...
Maybe you can give Samsung model name... where this work?
I could check SM-G920F with Android 7 just for fun... if I have time...
Thanx in advance.
Best Regards

regardless it is writeable to adb shell only (uid 2000), chown is forbidden anyway. even if you set SUID bit that wouldn't make much sense in /data/local/tmp
furthermore, even if you could place su binary in /system (which requires unlocked bootloader + dm-verity patch) it still requires privileged daemon in background where su want connect apps (but not exist).
so this method never worked, except for some ancient android devices where remount /system was possible from adb root.
and we haven't spoke about selinux, yet
Magisk does all this, but requires* unlocked bootloader - which triggers factory reset. So unless you have some nice exploit like dirty-cow or mtk-su, temporary root is simply impossible.
edit: TWRP is not able to decrypt samsung encryption btw. So if you want have access to userdata partition on locked bootloader the only way would be (samsung signed) so called "combination ROM" (with same bootloader level) to be flashed from Odin via HOME_CSC or heimdall.
if your device is ancient old you might lucky bootloader is unlocked, userdata partition is not encrypted at all, and ROM is just signed with test keys. in that case you can flash anything on recovery partition. philz touch recovery even provided flashable zips that signed with test keys, these zips can be flashed straight from stock recovery without PC. I remember temporary zips exist, that only boot into custom recovery without actually installing it.
edit2: *except some Mediatek devices with AVBv1 where one can flash magisk patched boot.img on locked bootloader

My last 2 cents here ( I no longer participate this thread ):
The su ( read: switchuser ) command is used to run an Android system function as a different user. It is the easiest way to switch or change to the administrative account ( read: superuser ) in the current logged in session.
Most versions of Android disable the superuser ( mostly mistakenly called root user - take note that root user in Android is the user with ID 0 who is by default present on all Android versions, is the user of session when Android gets started ) account by default making the system more secure. But, this also restricts the Android user from running specific system related commands.
Using su to temporarily act as a superuser allows you to bypass this restriction and perform system related tasks with different users.
The synthax of su command is
Code:
su [options] [username [[arguments]]
If a username isn't specified, su defaults to the superuser. Now, the logged-in user can run all system commands. This will also change the home directory and path to executable files.
If the su is used to temporarily act the logged-in user as superuser then the su binary can be located anywhere in Android's filesystem, e.g. /data/local/tmp, /storage/emulated/0, etc.pp, it must not be located in Android's system partition.

xXx yYy said:
My last 2 cents here ( I no longer participate this thread ):
Click to expand...
Click to collapse
yes, that's maybe better. teach yourself about android first. android is not linux
What special privileges "/system/xbin/su" does have w.r.t. root access?
This answer says: Because of the way directory/file permissions are configured on Android, you need to have the su binary on your /system partition in order for it to work. Putting elsewhere...
android.stackexchange.com

what is your current bootloader level? combination ROM is available (haven't checked these download links)
https://www.samsungfirmwares.info/samsung-sm-j415gn-combination-firmware-file-rom
my expectation ro.debuggable=1 is enabled
adb root will work on eng build

aIecxs said:
yes, that's maybe better. teach yourself about android first. android is not linux
What special privileges "/system/xbin/su" does have w.r.t. root access?
This answer says: Because of the way directory/file permissions are configured on Android, you need to have the su binary on your /system partition in order for it to work. Putting elsewhere...
android.stackexchange.com
Click to expand...
Click to collapse
Yeah, I get where they were coming from but.....
Nah. It just doesn't work that way for everybody. Like all things android, it really just depends on what device you have and how crappy its hardware/software and security is. Lower end/cheap and old stuff doesn't have as much time invested in making them secure to save on development and distribution costs.
Unfortunately, Samsung just isn't one of those brands that are easily rooted these days, unless you buy specific models with specific firmware/binary combinations.