Related
I saw in the SDK this permission for apps to request:
public static final String FACTORY_TEST
Run as a manufacturer test application, running as the root user. Only available when the device is running in manufacturer test mode.
Constant Value: "android.permission.FACTORY_TEST"
Click to expand...
Click to collapse
Our current model with superuser whitelist is not very secure because a malicious person could bundle their own su binary and circumvent the restrictions. It would seem that having our custom roms run in test mode would provide a great solution: using Android's own permission/security model for apps to run as root. This should force all apps to visibly request root permissions at install time.
I am in favor of anything that will improve the security of my phone. It concerns me that anyone who knows what they are doing can so easily boot into recovery mode on my phone, wipe and flash any ROM they want. Granted, they would not have access to my information if the wipe and flash. But, it makes it trivially simple to hijack my phone. I would like to have some password protection for Recovery and Fastboot.
i am by no means a dev, but it seems to me that this probably just has to do with the adp devices
what's a adp device? and explain how they could possibly do this again?
android developer phone.
jaaronmoody said:
i am by no means a dev, but it seems to me that this probably just has to do with the adp devices
Click to expand...
Click to collapse
well, technically, if we have root, dont have an "ADP" device?
when I do a fresh install, it says welcome to Android Developer Phone 1 (in most ROMs)
the adp device was a specific phone release for developers to be used with the sdk.
jaaronmoody said:
the adp device was a specific phone release for developers to be used with the sdk.
Click to expand...
Click to collapse
I know that, but the hardware is the same as ours (they just get the awesome battery cover)
jaaronmoody said:
the adp device was a specific phone release for developers to be used with the sdk.
Click to expand...
Click to collapse
Most roms especially cyanogen Roms are based on SDK/ADP1 directly and thus making our devices recognizable as ADP Devices.
Simple solution could be to restore the original su binary at boot.
1) keep a copy in the boot image ramdisk
2) scan the path at boot for su
3) compare md5sum with the original
4) delete if md5sum is different
5) restore original trusted su
and also just for paranoia:
6) scan system for setuid binaries and report to the user
This has NOTHING to do with ADP1. Test mode is just that... TEST MODE, i.e. diagnostics and repair. Probably needs to be plugged into a test station that authenticates using some manufacturer diagnostic keys. I really doubt that it would be a simple matter of requesting root permissions as this would be too easy to abuse.
And to the OP: No, you can't just bundle an 'su' binary and run it. The binary has to be owned and setuid as root in order for it to actually get root permissions. There is nothing magical about the su binary -- it is just 'sh' renamed as 'su', chown'd as root, and chmod 4755. A regular user can NOT chown root. Only root can chown root. Note that the su binary that works with the root app is modified such that it will terminate if the root app doesn't grant root permission. For all these reasons, su+rootapp is fairly secure. Not against someone unauthorized getting their hands on the device, but against some malevolent app taking root and running amok.
lbcoder said:
This has NOTHING to do with ADP1. Test mode is just that... TEST MODE, i.e. diagnostics and repair. Probably needs to be plugged into a test station that authenticates using some manufacturer diagnostic keys. I really doubt that it would be a simple matter of requesting root permissions as this would be too easy to abuse.
And to the OP: No, you can't just bundle an 'su' binary and run it. The binary has to be owned and setuid as root in order for it to actually get root permissions. There is nothing magical about the su binary -- it is just 'sh' renamed as 'su', chown'd as root, and chmod 4755. A regular user can NOT chown root. Only root can chown root. Note that the su binary that works with the root app is modified such that it will terminate if the root app doesn't grant root permission. For all these reasons, su+rootapp is fairly secure. Not against someone unauthorized getting their hands on the device, but against some malevolent app taking root and running amok.
Click to expand...
Click to collapse
Thanks for clearing that up.
The idea posted earlier about recovery menu password should be lofted at Cyanogen (or anyone willing to take that on). Should we make a thread for it?
Keep in mind that it is physically impossible to secure your phone against somebody who gets their hands on the actual device. You can only make it harder to get at it. If somebody wanted to they could just read the flash chip directly or use JTAG to get at it. However, I agree that adb could be made a bit more secure.
And to the OP: No, you can't just bundle an 'su' binary and run it. The binary has to be owned and setuid as root in order for it to actually get root permissions. There is nothing magical about the su binary -- it is just 'sh' renamed as 'su', chown'd as root, and chmod 4755. A regular user can NOT chown root. Only root can chown root. Note that the su binary that works with the root app is modified such that it will terminate if the root app doesn't grant root permission. For all these reasons, su+rootapp is fairly secure. Not against someone unauthorized getting their hands on the device, but against some malevolent app taking root and running amok.
Click to expand...
Click to collapse
@lbcoder,
That's nonsense. Check any linux system, /bin/sh is always owned by root and is always executable. Running an executable owned by user X does NOT run said program as X. Copying a binary onto the phone preserves permissions, so if i chowned an sh binary as root on my computer and copied it over, the binary will stay owned by root. The su binary is just that, a binary. It is not simply a shell owned by root.
nobodyimportant said:
@lbcoder,
That's nonsense. Check any linux system, /bin/sh is always owned by root and is always executable. Running an executable owned by user X does NOT run said program as X. Copying a binary onto the phone preserves permissions, so if i chowned an sh binary as root on my computer and copied it over, the binary will stay owned by root. The su binary is just that, a binary. It is not simply a shell owned by root.
Click to expand...
Click to collapse
you're missing the bit (pun intended) about su being setuid root. when a normal user runs su, it does, indeed run as root, but it uses the security subsystem behind the scenes to prevent unauthorized activity:
http://en.wikipedia.org/wiki/Setuid
the 'unzip' executable will, indeed, preserve ownership, but to my knowledge, there's no way to copy a setuid binary to the phone as a normal user -- there may be a way it could be pulled off, but I don't know how
nobodyimportant said:
@lbcoder,
That's nonsense. Check any linux system, /bin/sh is always owned by root and is always executable. Running an executable owned by user X does NOT run said program as X. Copying a binary onto the phone preserves permissions, so if i chowned an sh binary as root on my computer and copied it over, the binary will stay owned by root. The su binary is just that, a binary. It is not simply a shell owned by root.
Click to expand...
Click to collapse
I have one thing to say to you:
http://en.wikipedia.org/wiki/Setuid
Now that you've made a complete and utter fool of yourself, how do you feel?
FYI: your regular user can NOT chown root. Go ahead and try it.
alapapa said:
you're missing the bit (pun intended) about su being setuid root. when a normal user runs su, it does, indeed run as root, but it uses the security subsystem behind the scenes to prevent unauthorized activity:
http://en.wikipedia.org/wiki/Setuid
the 'unzip' executable will, indeed, preserve ownership, but to my knowledge, there's no way to copy a setuid binary to the phone as a normal user -- there may be a way it could be pulled off, but I don't know how
Click to expand...
Click to collapse
It is a moot point whether the setuid bit can be restored since a regular user doesn't have the ability to change the owner to anything but self, which means that the best they could do is create an su binary that will give other users THEIR OWN permissions.
A regular user can change ownership *only* to self -- i.e. if they have group or other write permission, then they can chown the file. They can also change the group, but only to groups to which they are members -- and this requires that they already have some form of write permission on the file.
Note that extracting a file is no different than actually *creating* the file, which means that if the user couldn't simply MAKE the file, then they can't *extract* the file either.
If any of this was untrue, there would be nothing to stop any user from doing something like this to take over any Linux computer (except from within a chroot jail, but that doesn't apply here);
cp `which sh` ~/su; chown root:root ~/su; chmod 4755 ~/su
** but that most definitely won't work.
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...?
In this post, I'm not telling any tricks or methods. I am just providing my thoughts and possibilities. Recently I was trying to root my phone and I did a little bit of research on it. By the way, note one thing here that my phone is part of the Android One project and made by Xiaomi, so it's much harder to root than any other phone. If you have also tried to root your phone, then you might have also heard these words... (Magisk manager, Superuser, Busybox, SU Binary, TWRP Custom recovery, root file, System file, Custom Rom), etc. In this thread, if I am right you can root your phone just by using ADB Shell. Rooting your phone means...
Rooting (Android)
From Wikipedia, the free encyclopedia
Rooting is the process of allowing users of smartphones, tablets, and other devices running the Android mobile operating system to attain privileged control (known as root access) over various Android subsystems. As Android uses the Linux kernel, rooting an Android device gives similar access to administrative (superuser) permissions as on Linux or any other Unix-like operating system such as FreeBSD or macOS.
Rooting is often performed with the goal of overcoming limitations that carriers and hardware manufacturers put on some devices. Thus, rooting gives the ability (or permission) to alter or replace system applications and settings, run specialized applications ("apps") that require administrator-level permissions, or perform other operations that are otherwise inaccessible to a normal Android user. On Android, rooting can also facilitate the complete removal and replacement of the device's operating system, usually with a more recent release of its current operating system.
Root access is sometimes compared to jailbreaking devices running the Apple iOS operating system. However, these are different concepts: Jailbreaking is the bypass of several types of Apple prohibitions for the end-user, including modifying the operating system (enforced by a "locked bootloader"), installing non-officially approved (not available on the App Store) applications via sideloading, and granting the user elevated administration-level privileges (rooting). Many vendors such as HTC, Sony, LG, Asus, and Google explicitly provide the ability to unlock devices and even replace the operating system entirely. Similarly, the ability to sideload applications is typically permissible on Android devices without root permissions. Thus, it is primarily the third aspect of iOS jailbreaking (giving users administrative privileges) that most directly correlates to Android rooting.
Rooting is distinct from SIM unlocking and bootloader unlocking. The former allows removing the SIM lock on a phone, while the latter allows rewriting the phone's boot partition (for example, to install or replace the operating system).
Source: Wikipedia
So, as much as I've noticed (I could be wrong) mainly all rooting processes does one of those two things,
1. Edits your boot.img
or
2. Adds a SU binary file to your system & more specifically to your system/bin file.
So if that's true and every Android phone or at least the same brands or same models or at least same Android versions or maybe all of them requires the exact same SU binary file(Superuser binary file). Now, if you don't want to change your boot.img there is only one is remaining and that is adding the SU binary file. Now you might ask how to do that...
Just use your ADB shell to give writing system files permission to your file manager. And then put the SU file to your system.
So, that's all I was just trying to say. Now if I am right please let me know and thanks for reading until now. And also if I am right, please someone provide me the SU binary file of Xiaomi MI A3, code name: laurel_sprout . Thank you once again, All developers, take care of your health. For further inquiries and helping me out, message me on XDA personally.
Writer: Samiullah Ridoy.
Samiullah Ridoy said:
...
Just use your ADB shell to give writing system files permission to your file manager. And then put the SU file to your system.
...
Click to expand...
Click to collapse
Absolutely errleading ( i.e. wrong ) statement:
1. To mount Android's partition /system as RW - so you can copy SU-binary onto it - you need superuser ( SU ) rights.
2. Modern Android versions have SELinux enabled, and most also DM-verity and/or AVB. These safety-features lock the /system partition to get tampered, what at least with regards to SELinux and/or DM-verity only can be disabled by superuser ( SU ).
3. With regards to AVB one has to unlock device's bootloader, too, in order to disable this lock.
@Samiullah Ridoy
As above post said,
-You can't simply give writing system files permission.
-Only emulators have that ability(since they are not production builds)
Here is your device specific guide at Mi A3 forum https://forum.xda-developers.com/t/...-root-mi-a3-with-magisk-without-twrp.3958509/
Rooting your device is same as any other device if we use Magisk rooting method. It does not take additional steps to root your specific device.
Thanks
You need to disable DM-verity.
You can do it from ADB. You need to modify Stock boot image file. Patch it and disable DM-Verity.
HemanthJabalpuri said:
@Samiullah Ridoy
As above post said,
-You can't simply give writing system files permission.
-Only emulators have that ability(since they are not production builds)
Here is your device specific guide at Mi A3 forum https://forum.xda-developers.com/t/...-root-mi-a3-with-magisk-without-twrp.3958509/
Rooting your device is same as any other device if we use Magisk rooting method. It does not take additional steps to root your specific device.
Thanks
Click to expand...
Click to collapse
I have already seen that post & I don't want to do it that way. You said, " You can't simply give writing system files permission. ", I've already mentioned but saying it once again that I could be wrong but we can give writing system files permission by using these code...
Code:
adb shell pm grant [package name] android.permission.WRITE_SETTINGS
adb shell pm grant [package name] android.permission.ACCESS_MEDIA_LOCATION
adb shell pm grant [package name] android.permission.WRITE_INTERNAL_STORAGE
Tell me if I am wrong & thanks for your compliment.
Samiullah Ridoy said:
I have already seen that post & I don't want to do it that way. You said, " You can't simply give writing system files permission. ", I've already mentioned but saying it once again that I could be wrong but we can give writing system files permission by using these code...
Code:
adb shell pm grant [package name] android.permission.WRITE_SETTINGS
adb shell pm grant [package name] android.permission.ACCESS_MEDIA_LOCATION
adb shell pm grant [package name] android.permission.WRITE_INTERNAL_STORAGE
Tell me if I am wrong & thanks for your compliment.
Click to expand...
Click to collapse
I didn't tried those but I am sure those are NOT for writing read-only partitions.
Those are for accessing internal storage and changing settings like brightness I think.
jwoegerbauer said:
Absolutely errleading ( i.e. wrong ) statement:
1. To mount Android's partition /system as RW - so you can copy SU-binary onto it - you need superuser ( SU ) rights.
2. Modern Android versions have SELinux enabled, and most also DM-verity and/or AVB. These safety-features lock the /system partition to get tampered, what at least with regards to SELinux and/or DM-verity only can be disabled by superuser ( SU ).
3. With regards to AVB one has to unlock device's bootloader, too, in order to disable this lock.
Click to expand...
Click to collapse
Absolutely correct.
It seems to me OP has never tried this, simply has copied from other sources. That is why the nonsense.
I want to edit camera_features.xml file but it needs root access, I don't want to root device but I think there is a way through ADB or using some third party apps that uses super user permission to edit root files
Please I'm sure there is way to edit it without rooting device by using special third party apps but I need someone who know how to
Temporarily root Android by putting a suitable su binary into Android's filesystem - preferably /data/loca/temp - and making it executable.
https://forum.xda-developers.com/attachments/su-binaries-zip.5566949/
I don't find the directory data/local
And does it require root to put the su file there
Noticed that I made a spelling mistake:
The directory recommended to copy su binary into is
/data/local/tmp
what exists on all Android versions since beginning and by default is mounted as RW
How can I reach the folder, which app can reach and copy files to root data/local/tmp without rooting device
You use ADB - of course requires USB DEbugging got enabled on device in question.
To clarify things: the su binary is the root functionality you want to add to Android.
I tried to use adb push su data/local/tmp but it doesn't work
xXx yYy said:
You use ADB - of course requires USB DEbugging got enabled on device in question.
To clarify things: the su binary is the root functionality you want to add to Android.
Click to expand...
Click to collapse
I know but I think there is another way using apps that uses system apps permissions
Such as editing root file of the device as official device updater
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.