An Introduction to Android Rooting for the Complete Beginner - Android Software/Hacking General [Developers Only]
There are a few of these guides around, but I thought to write my own. Hope it will be helpful! I'll keep the most up-to-date version on my site.
Rooting Android: What Is it?
If you've heard about "rooting" your Android phone, and are confused by what exactly it does, or don't understand the instructions you found on an obscure forum or blog post somewhere, this guide might help you make sense of things.
What Is "Root"?
"Root" is the name of the default administrative user in Unix. The user named "root" can do absolutely anything: edit or delete any file, start or stop any system service, and also add, remove or change the privileges of other users, so that they, too, could perform the same operation.
So, user "root" can actually bestow administrative privileges on any Android user, including the default one you use normally on the phone.
When you buy an Android phone, it normally does not let you login as user "root".
What Can User "Root" Do?
Your phone is really a general-purpose hand-held computer. People have written apps for it that can do the things like this:
Turn it into a wireless internet router, connecting to your 3G/4G network on one end, and broadcasting a wifi hotspot on another. You can thus connect your laptop to the internet from anywhere. "Tethering," but without cables!
Lets you overwrite any of the Android system files, customizing it to your heart's content. This lets you customize the built-in fonts, colors, keyboards, etc.
Lets you install newer versions of Android, beyond what your phone's vendor has provided.
Why stop at standard Android? Because Android is an open source operating system, people have been able to modify it to add features far and beyond what Google has put in it, as well as offering better performance in some situations. With administrative privileges, you can just flash an entire new Android ROM to your phone. A very popular one is CynaogenMod, which is based on Android 2.3.
Install various networking servers and clients, such as QuickSSHd to allow logging in to your phone over the internet, or CifsManager, which lets you access Windows shared drives from your phone.
Who knows? People might think of new users for these hand-held computers, uses that would require full access to all features of the phone.
Why Won't My Phone Normally Let Me Login As "Root"?
First, for reliability -- as far as you're concerned.
Imagine if your phone automatically gave you administrative access. This means that any app you install can do anything it wants to it. Obviously, unacceptable.
An alternate solution is available in newer versions of Windows and other desktop operating systems, which require you to enter a special administrative password whenever a program is trying to access secure parts of your computer. This is annoying enough on a desktop computer: on a phone, it would again be unacceptable.
So, it makes sense -- for your sake -- to disallow any administrative privileges.
Second, for reliability -- as far the phone vendor is concerned.
A smartphone, unlike a PC, is an expensive consumer device with an explicit support contract. People normally and frequently return phones to the shop if they stop working properly, or call customer support to get assistance. There's a huge cost for the vendor to maintain this support network.
Think for a minute what would happen if any phone user could login as "root" and delete any system file: you would have broken phones everywhere, frustrated consumers, and clogged support networks. Indeed, "rooting" a phone pretty much voids your warranty as far the vendor is concerned.
I Understand the Risks and Am Willing to Void the Warranty, So Why Can't I Login As "Root"? It's My Phone!
Even if logging in as "root" were an advanced feature, hidden away somewhere in the menus with thousands of warnings about possible dangers, you can bet that many non-advanced users would find it. When their phone breaks, you bet they will be angry, and will not care that the warnings were there. As far as they would be concerned, this "root" thing is a feature of their phone, and if it can break the phone then it shouldn't even be there.
And there's a third party who has a business interest in denying you "root": the telecommunication carriers. Their business model is designed around typical consumer uses of the phone, and they do not want it to be too powerful. For example, a "rooted" phone can let you tether it to a laptop, so that your laptop gets its internet access. But, carriers typically sell special "laptop sticks" for that purpose specifically, and these usually are more expensive than phone plans, because they take into account the much heavier bandwidth that laptop users tend to use. If everybody could "root" their phone and tether it, this product -- and source of revenue -- would be irrelevant.
So, Phones Don't Come with a "Root" User?
Android is based on the Linux operating system, which requires the "root" user to function. It's there. However, the vendor has tried to hide all the normal ways to access it. The "root" user is there, it's just "locked."
What Is "Rooting"?
In the context of Android phone, rooting means more than just letting you log in as the "root" user: it means installing a set of tools so that any of your programs can access "root" when then need to and you allow them.
The result is that "rooted" phone works just like Windows, in that it will ask you for permission (but not a password) whenever an app is trying to get administrative privileges.
Fortunately, once you gain access to the "root" user, it's very easily to install a set of standard apps that let you implement this feature, specifically the Superuser app.
How Do I Root My Phone?
Nothing in software can be truly locked down, and hackers have found ways to get "root" access on any Android phone on the market. There are quite a few holes.
But, these methods vary a lot and are different per phone. It's easier on some phones than others. It's often risky, too, because a misstep could potentially "brick" your phone -- making it so that you cannot boot into Android. "Unbricking" is possible in some cases, but not in others. Take care!
Search the internet, and you will likely find various blog and forums posts with instructions for rooting your particular phone model.
This is not a guide for rooting your particular phone model. Instead, it is a general description of what rooting is and how it works. It can help you understand the rooting instructions you find.
Any Downsides?
Well, first of all, there is the risk of bricking your phone. You might want to make sure that someone you know with the same model phone as you have has used the method before. Or, read about it in the internet forums, and make sure that lots of other people have used this method successfully.
Also, you may void your warranty: of course, this would only happen if customer support looks closely at your phone and notices that it has been rooted. It's a good idea to look at these rooting guides to see if there is an easy way to un-root the phone, or at least return it to factory settings.
Finally, there's the issue of "firmware updates" coming from your carrier. Sometimes they will work fine with rooted phones (as long as custom Android ROM has not been installed on them), but depending on the rooting method it may mean that won't work fine anymore. "Not working fine" can mean that the upgrades simply won't run, but it can also mean that the upgrades would fail terribly and brick your phone. Generally, if you have rooted your phone and are getting an "Update Available, Do you want to download?" message from your carrier, don't just say "yes," instead check the forums to see the experience of other people with rooted phones with this update. Generally this problem seems rare, a result of a very poor upgrade package from the vendor -- the usual case is that the upgrade simply won't work.
Don't worry too much: with a rooted phone (and a good Recovery program, see below) you will likely be able to install the upgrade yourself, and possibly better upgrades to more advanced versions of Android than your vendor provides.
How Rooting Works
First, let's understand how the locking down happens.
Your phone actually has more than just Android installed on it. There are, at minimum, three and usually four "partitions" in which entirely different programs are installed. Android is just one of them.
The Boot Loader
The first partition has the boot loader, the very first program see when you turn on the phone normally. The boot loader's main job is simply to boot other partitions, and by default it just boots the Android partition, commonly called the ROM (described below). So, you don't really see the boot loader for very long.
However, all phones allow for a special way of turning them on -- for example, holding the volume up button while pressing the power on button -- that shows the boot loader menu.
When you're there, you can actually choose if you want to boot into the Android partition, or you can boot into the Recovery partition (described in detail below).
The interesting thing about the boot loader is that it is very, very simple. It has no mechanism for users and privileges. One way to look at it is that it always is "root," and in fact can't be anything else.
Sounds like a good place from which to unlock your phone! Unfortunately, most boot loaders are too simple.
One exception is the boot loader found in Google's Nexus phones, and in a few other developer-friendly phones. These boot loaders can actually communicate with a PC over USB, and support writing data to partitions ("flashing" them), as well as booting from them. With this feature, you can flash an unlocked Android ROM to the Android partition, and you're done! Well, the challenge is just to find such a ROM that works well with your phone...
Most phones don't have such a flexible boot loader. However, getting into the boot loader menu is important, because it lets you boot into the Recovery partition, detailed next.
The Recovery Partition
As its name can tell you, this partition is mostly for customer support: the Recovery program can be used to return the Android partition to its factory settings, which can solve a lot of problems with faulty phones, or phones that were infected by bad apps. It can also format the SD card partition.
Some Recovery programs can also install special phone upgrades from the SD card, that write directly to ("flash") the Android ROM partition. Obviously, free access for anyone would allow rooting, so vendors make sure that Recovery would only accept official upgrades. But, one way to root a phone would be for hackers to find a way to create such an "upgrade" that the Recovery program would accept.
There's quite a lot of variation in Recovery programs out there: every vendor has their own idea of which recovery features would be useful for their customer support team. Boot into yours and take a look! It's harmless, unless you actually choose one of the recovery options...
Like the boot loader, the Recovery program is always in "root". A hacked Recovery program could let you flash an unlocked Android ROM, or run any "upgrade" you like. So, in addition to just "recovering" an unusable phone, it can help you "recover" the "root" user that has been locked from you!
A good Recovery program is very useful for customizing your phone, beyond just rooting it. By far the most popular Recovery program is Clockwork Recovery, also called ClockworkMod.
Some rooting methods begin by finding a way to flash ClockworkMod to your Recovery partition, from which you can then run an "upgrade" that roots your phone. Other rooting method find another way in, but still recommend you flash ClockwordMod as soon as possible, because it's just so useful for customizers.
You will not find a homepage or an "official" way to download ClockwordMod: carriers obviously do not want you get have easy access to it. But, search around, and you will find one appropriate for your phone. The ROM Manager app can also flash it for you, assuming you are already rooted.
The SD Card
This is another partition, entirely for you. It is not protected in any way, and you have full access to reading and writing files on it.
For many phones, this partition does not exist unless you physically install an SD card. Some phones have a built-in SD card.
The Android ROM
Finally, the most important partition on your phone! When the boot loader starts the Linux operating system (the "kernel") that sits underneath Android, one of the first subsystems to come up is the security system. From then on, the "root" user will be used to start various user-level subsystems required for the phone to function.
Eventually, the default user will be started, and that will be used to run your apps: the status and notification bar that appears on the top of the screen, the settings manager, the virtual keyboards, etc. Finally you get the home launcher, from which you can launch all the other apps on your phone. None of these programs run as "root", so you are effectively locked from administrative privileges.
The Linux operating system can set security permissions per file. So, indeed large parts of this partition are restricted to be read-only by any user except "root". So, if you boot into Android, none of the apps you run will be able to change these system files. The rest of the partition is readable-and-writeable, and generally functions just like the SD card partition, though it's usually much smaller.
Of course, if you boot into Recovery instead, you will be able to write to these files, because you are "root" there. That's why ClockworkMod is so useful for rooting your phone!
Most Android apps run on yet another layer, a virtual machine called Dalvik, which is a heavily modified version of the Java virtual machine found on previous generations of cell phones, as well as on desktop computers, servers, and many other devices. Definitely, everything you install from an app store will run on Dalvik. Dalvik is a tightly controlled environment in which privileges are carefully controlled per program, beyond what the Linux operating system provides. Not only do apps not have administrative access to the phone, but they can be limited in access to wifi, cellular access, and your data.
Except... that Android does provide a way for apps to request administrative privileges. In locked phones, this is automatically and silently denied. However, the Superuser app can hook into these requests and let any app switch to the "root" user, from which they have full administrative access. A friendly dialog box will pop up, asking you if you want to give the app full permissions. Say yes, and there you go!
A phone in which the Superuser app is running properly is rooted.
Summary: Rooting Methods
The rooting instructions you find will likely be one of these, or a combination of these steps:
Phones with boot loaders that can be unlocked (such as Google's Nexus) will let you flash other partitions. You can flash a whole Android ROM that is already rooted, such as CynaogenMod, and you're done! Or, if you don't want to replace your entire Android ROM, you can flash ClockworkMod into the Recovery partition, and move from there to the next method.
Some rooting methods start with a hacked way to flash ClockworkMod into the Recovery partition. With ClockworkMod, you can run your own special "upgrade" from the SD card. This "upgrade" will vary a lot per phone model, but at the minimum it will involve installing the Superuser app. For some phones, it will modify a few Linux configuration settings to make sure that Superuser app can login as "root." Other, more heavily locked-down phone models might require replacing certain locked parts of Linux and the Android system, sometimes much of the Linux "kernel" itself.
Other rooting methods use the phone's existing Recovery program, but the hackers found a way to create an "upgrade" that can fool the Recovery program into believing it's official. From there on, it's identical to the previous step.
Some rooting methods start straight from Android. Hackers found a way to login as root while Android is running. Of course, logging in as root is not the same rooting, but once you are logged in as root you can run a similar "upgrade" as is used in the previous steps.
Need More Help?
Don't ask me, please! Seriously, I spent a lot of time writing this long article specifically so I would not have to keep answering questions about the process. There are many internet forums and bloggers that welcome questions from noobs. I've generally found the Android hacker community to be extremely generous and welcoming.
Happy rooting!
Nice - but clarification requested
I like the article as it answers some questions.
One thing I'm curious about - you seem to use the terms Recovery Partition and Recovery Program interchangeably. Is that your intent? I'm not trying to split hairs - I just want to understand. I would have expected booting into the recovery partition loads the recovery program.
Also, you talk about how vendors choose features of their recovery program. CWM is then a replacement for the vendor supplied recovery program, correct? If you root then install CWM, are you in effect replacing the recovery program after rooting (as opposed to forcing CWM to overwrite the existing recovery program via flash)?
Thx
Thanks!
A very useful guide for android beginners like me!
Sorry for the bump . This post deserves a thanks and a bump
Thanks! A very useful guide for beginner. I've forwarded this to my colleague who just switched from Windows to Android phone.
Much appreciation!
Thank you so much. I have just purchased a rooted phone & have a ton of questions. Have spent hours here tonight searching for basic info. Finally found this & it really helped this total "noob".
Thank you again.
thanks (very2 usefull) from iphone4 user
Good work..
Sent from my Galaxy Mini using xda-premium
Thanks. It helped very much
how to root sony xperia u
How to root sony xperia U..?
please give me detailed and simple procedure to follow...
i would also happy to know should i have pc drivers to run this rooting process..?
thanks
Thx for taking the time to write the article helped me understand a lot of things
Related
Garminfone ro.secure=0!
I cracked the img format for Garminfones... started out by looking at the format of the file and it turns out the only difference is the loader addresses. Took the stock recovery and disabled security, which worked. Then modified the boot.img to disable security and had the filesystems mount rw by default and flashed it to the recovery partition. Booted into recovery mode and viola... security disabled. Now it is time to flash it to the boot partition and cross fingers. Now I just need to figure out how to compile a working recovery mode... preferrably one that can be activated by keypress. Not sure how to do that part. I can only get to recovery and bootloader mode after booting into the os. I should have a working mkbooting soon so I don't have to hex edit the generated img files.
Well done! I look forward to any progress reports that you make. Are you using the official or leaked version of the 2.1 Eclair?
The official and leaked versions are equal. And I did find out that we do have fastboot It's the blue screen that you get when you hold UP+POWER, or do adb reboot bootloader... two different messages on the screen. I can get fastboot to accept a reboot-bootloader command, but I'm having some issues actually getting any information out of it or flashing something like a boot image. To get it to respond, you do: fastboot -i 0x091E <command> the -i makes it specify the Vendor ID, since fastboot only accepts a few vendors by default. I also found out that I don't have to rebuild the mkbootimg program... if you add --base 0x1AC00000, then the load addresses match up in the resulting img file.
If someone is willing to host it, I can share the modified boot.img that sets ro.secure=0 and mounts the filesystems RW by default.
Hey, just joined to reply to this thread. Is it possible for you to upload to a file-sharing site such as megaupload, fileserve, etc. I'm just getting into this whole rooting/modifying stuff. I used z4root to root my A50 and have installed superuser. I have deleted some of the carrier .apks but am thinking I should have made a back-up before doing so. I also bought setcpu from the market before finding out the Qualcomm chip does not allow overclocking. Can I ask what the point of modifying the boot image is? Is this the first step in being able to install custom roms to the phone? Anyway, appreciate the effort you guys have put in to modifying the phone.
You get a higher level of access, along with things like being able to customize parts of the phone, in my case enabling read/write by default. I also am planning on playing a bit, like remapping partitions... the instructions are in the init.rc file. Always take a dump_image (or remount all mtd partitions as read only and just use cat to dump the mtd partitions). Also tar up each of the root folders (and files) in case you need quick access to any files you may have deleted. If you need a system app back and you don't have a backup, you have to reflash 2.1 again. Very important... if you care about the Garmin map software, make sure to get the /storage folder, including the one in it named .System... you can recover the maps, vehicles, etc by using two different Garmin web update windows programs-- one for the system stuff and one for the maps. Better safe than sorry.
any news on this What would we need to be able to overclock?
I spent a good portion of the day yesterday rooting and installing CyanogenMod on my fiance's MyTouch Slide, and I have to say, it was amazing. It's a lot more than just a throwing around some custom default apps, cleaning up bloatware, even adding some kernel modules... I can do all of that on my rooted Garminfone just fine. It also had the Android 2.3 base, and it has polish and refinements that just can't be done without a custom built ROM. I bought my Garminfone on purpose, even knowing that it shipped with Android 1.6, even knowing that the interface was awful, even knowing that the device wasn't going to sell as well as I wished it would. I bought it for it's offline maps, and for it's fantastic GPS. Things have improved since I bought my device... Android 2.1 was released, an improved user interface arrived, I gained root access and was able to clean up some stuff, etc. etc. But none of that prevented me from being jealous yesterday after seeing CyanogenMod. Further, Cyanogen has experience with preserving apps through the process of installing his mod for the first time; He did it when Google first sent him the Cease and Desist letter barring him from packaging CyanogenMod with Google Apps. I'm not sure HOW he did it, and I don't care, but I do think that it's very possible for him to do just that again with our Garmin Maps and the associated apps. For these reasons, I suggest that we could have our cake, and we could eat it too: Have a modern OS (Based on Android 2.3), have a clean, unified interface, with no bloatware AND our maps... Cyanogen is not known for making his mod for phones he doesnt own. Further, as we all know, ours was possibly the worst selling and least popular android device ever released to market. While I consider myself versed in the ways of Linux, I am not a developer. I run Gentoo, and have the associated skills, and I will contribute in any way I know how, but hacking is not my forte. I can't expect brilliant minds to work for any project for nothing. Therefore, I am putting my money where my mouth is... I'm going to take all the money from my weekly paycheck that I can afford, and I'm going to donate it to that project. It won't be much... I am a starving college kid, after all... but it will be generous within my means. I am also going to post a reference to this thread everywhere I know how... My contribution might be small, but the community might be able to get something together that is mighty. Visit topic 5864-garminfone on their forums to add your support. (Edit: They moved my post, I have corrected this with the correct forum topic)
Possible to Replace a System File without Rooting?
I am a NOOB, but I like myself just fine. The video for NOOBs is funny, but IMHO, should be a bit more serious. I'm one of those people experiencing issues with GPS and TTFF being excessively long on the MT. Cry. If I run MyPhoneExplorer, I can see the system file structure, and I believe I can move files to the phone. I believe I can do the same with SwiFTP. Can one drop replacement GPS libraries for example into the SYSTEM and SYSTEM/HW sub-directories using a program like MPE, or an FTP program like SwiFTP without rooting, and would they be honored on the next reboot? Would I be mangling some check-sum or other that determines the integrity of the system loaded? I'm one of those users that doesn't really want to root if not necessary, but I wonder if doing some mod like the above - would doing so lay subsequent update pushes from VMUSA to waste? Also, I'd really like if possible to flag some programs not to load, unless I explicitly ask them to load via the U.I. with intent. I suppose I'd have to root to do something like that. Perhaps with Ginger-Break? Would doing this make subsequent updates problematic? Any information regarding my constraints and options to effect both of the above would be very appreciated. Thanks.
There are ways to mount the various partitions from a host machine (e.g. Linux) while it is in the "emergency" flash mode, which would permit what you want to do. Doing this is quite dangerous - at least as much as rooting the device and perhaps more-so.
I appreciate the response. OK, if I were to root via Gingerbreak and install the files that way, then un-root, would my system then appear to be (to an update provided by Motorola or VMUSA) as something which couldn't be updated? In other-words would rooting put me on a path to having to use specially modified updates? Thanks.
Depends on what you change. In GENERAL no, the update will come through. The major risk is that it crashes on install as some part of what you changed is a dependency but is not reloaded. This is rare, but can happen. So.... root, install Clockwork, and make an immediate Nandroid backup BEFORE you screw with anything. That SHOULD allow you to un-hose yourself if you get in trouble.
[Q] Firmware layer differences between phones and PCs
I only recently started looking into smartphones (got two android devices to play with just this winter), and some things seem surprising and strange to me, since I'm coming from a PC (GNU/Linux) background. So several technical questions come to mind when trying to learn more about this. One thing I'm curious about is the fimware layer, that is, the part that connects the hardware to the OS, on generic current smartphones, and how it differs from what we currently have on PCs.
On PCs, everything is relatively simple, the UEFI is the central firmware that handles hardware initialisation and starting a payload (bootloader or OS). One thing PC users come to expect is that UEFI allows booting from different media, be it several hard disks, external storage, DVD etc. And UEFI acts as a sort of bootloader itself, having the ability to list registered EFI files and boot from them (although vendor implementations vary here).
So the standard boot procedure on PCs is like this: UEFI starts the hardware, selects the first UEFI boot entry, loads a bootloader (typically GRUB), the bootloader presents the user with a list of OSs and loads the selected OS (GNU/Linux or Windows). There are variations of this (notably Coreboot that can skip all the middlemen and start the OS directly), but what I described is a typical modern dual-boot scenario.
It seems that a lot of these assumptions don't work for current smartphones. You usually have a "locked bootloader" (already raises a question: is this really a bootloader, or is that a part of the firmware? Where is it, in the internal memory – the "hard disk" – or on a separate reserved flash storage?). Often times you can unlock said "bootloader" (it seems that this was a major consumer victory at some point).
When it's "unlocked", then you can install something called a "recovery". (One of the two devices has TWRP installed and I know how to use it, but not exactly how it works.) Oddly enough, it seems that a "recovery" is even expected to be installed after "unlocking the bootloader" by the manufacturer itself (the service menu on my HTC device has an option literally called "Recovery"). From what I can tell, this recovery is something a bit similar to what the bootloader on PCs does (TWRP allows creating and switching between "ROM slots", which is pretty much boot entries), but it also has backup/restore functionality (from what I can tell, that means creating an image of all OS files and dumping it into a specified directory), partitioning functionality, and some tools for offline modification of the OS ("ZIP flashing" and such).
Tasks like that on PCs are usually done either from within the OS, or by booting from external media (which is safer). So here the question is, what prevents doing that on smartphones? Why doesn't the "recovery" act like a standard bootloader: allow selecting between OSs to boot, and if there is an SD card with recovery software on it inserted, boot from it?
Then the "ROMs" themselves. On PCs, you just insert installation media and install whatever you like (minding the partitions and dealing with OS driver support). What prevents doing that on smartphones? This probably follows from the last question, but why can't you insert an SD card with, say, a Gentoo ARM base system, then use it to bootstrap an installation on internal storage?
On a related note, I'm unpleasantly surprised with the whole Android "rooting" thing. On GNU/Linux, such a thing is unfathomable. You install the OS and you set the root password. In the current smartphone world it's like the manufacturer owns the smartphone, not you, and refuses to give the root password for some notorious reason... This also brings up a question: if users don't get the root password, what is the security system on Android like? On GNU/Linux you can't install any application without root rights, which is fair because that means you will think twice before installing applications, and viruses can't destroy your system or change any system configuration files because that requires a root password.
And then about the firmware itself. Does it work different from UEFI, and if so, how? Are there any standards, like UEFI is on x86? Can the firmware be replaced (like it is possible on x86 with Coreboot)?
Thanks for any information you can give me on all these questions
Why isn't there Linux style root on Android?
This is something I have been wondering for a while and after searching the forums and Google I have not been able to find a clear answer. As a long time Linux user the idea of running your system as root all the time is appalling. It is a huge security risk. But for some reason that is really the only way to gain root access on an Android device (as far as i am aware). Apps like SuperSU allow you to pick the apps that are allowed to run as root, but there is no password or verification that the entity approving the access actually has the authority to do so. I hear all the time that rooting your phone is a trade-off between customizability and security, but every Linux system has a root user and it is incredibly secure when properly administered. What is the reason for the difference? From what I have read, it sounds like part of the issue has to do with Android handling users differently. I would love to be able to maintain a more limited root function on my devices. Thanks.
funkbuqet said: This is something I have been wondering for a while and after searching the forums and Google I have not been able to find a clear answer. As a long time Linux user the idea of running your system as root all the time is appalling. It is a huge security risk. But for some reason that is really the only way to gain root access on an Android device (as far as i am aware). Apps like SuperSU allow you to pick the apps that are allowed to run as root, but there is no password or verification that the entity approving the access actually has the authority to do so. I hear all the time that rooting your phone is a trade-off between customizability and security, but every Linux system has a root user and it is incredibly secure when properly administered. What is the reason for the difference? From what I have read, it sounds like part of the issue has to do with Android handling users differently. I would love to be able to maintain a more limited root function on my devices. Thanks. Click to expand... Click to collapse You can set a passcode with SuperSU....
Thanks for the reply. That is good to know. Does that really fill the security gap though? I guess if I set My non-background root permissions to expire every 15 minutes that does help for apps that do not need to run as root in the background. I am more referring to the distinction between regular user land and the root user. Titanium Backup for example; If I want it to be able to run a full backup (including system apps and settings) of my phone every night I have to give it permanent root permissions. That root permission applies to both the automatic process and anything that I as a user (or any entity that can get control of TB) to act as root as well. Ideally there would be 2 separate instances of the program; the back-up process (a daemon perhaps) initiated by the root user and a second available in regular user space. This sort of thing is common on Linux systems. My knowledge of Android is not particularly deep. I cannot tell if there is actually a separate root user or how user/group permissions work. It seems that the Android framework is designed around the user not having root access. Which is a bit confusing for an OS that prides itself on customization and "Be together not the same". I can't imagine buying a desktop PC that didn't allow me to have system level (root) access. Why should it be any different on a mobile device?
How to securely erase Android phone that I can't encrypt?
So I'm selling my old Meizu M2 Note which is running Flyme OS that doesn't allow me to encrypt the whole phone. How can I ensure the data is actually gone before selling? Normal wiping doesn't erase everything.
That's a good but hard to answer question. A good old fashioned hard drive can be single pass overwritten (debate about overwrite passes is still an open discussion) making it unrecoverable for anything but an MFT, Mobile devices use flash memory just like a USB drive or an SSD. What is the difference? Wear leveling (https://en.wikipedia.org/wiki/Wear_leveling). Because of that people came up with crypto-shredding or crypto erase which only truly works with Hardware Encryption because Software encryption can never, with 100% certainty, know how the wear leveling reacts on every device. You already said this isn't an option so what can you do to be sure nothing can be recovered? The answer is unfortunately short, nothing. However recent research showed that multi pass overwriting caught a lot of data but even the Gutmann method (35 passes) did not get rid of everything (I forgot the link to the Whitepapers). That said, you aren't selling it to a forensic specialist. My best suggestion is to use one of the higher rated wiping apps (Shreddit for example) to first destroy your files, then factory reset and download a few good recovery apps and again a wiping app. Make sure you can't recover your own files anymore (if you have very sensitive data you can connect it to a PC and use even better recovery or, if you are paranoid, forensic tools) then overwrite it with as many passes, rounds and algorithms you feel comfortable with. Check recovery tools again and call it a day when you feel satisfied. This WILL eat at the wear level so keep that in mind when you want to start overdoing it. Not everything will be gone but it's as good as it's going to get and I highly doubt the person you sell it to will be able to recover anything. Good luck!
GU42 said: So I'm selling my old Meizu M2 Note which is running Flyme OS that doesn't allow me to encrypt the whole phone. How can I ensure the data is actually gone before selling? Normal wiping doesn't erase everything. Click to expand... Click to collapse #noob guide incoming (potentially useless and harmful) i just thought of it shred memory download custom rom and flash fill memory with stuff shred again xD
TheMarchHare said: That's a good but hard to answer question. A good old fashioned hard drive can be single pass overwritten (debate about overwrite passes is still an open discussion) making it unrecoverable for anything but an MFT, Mobile devices use flash memory just like a USB drive or an SSD. What is the difference? Wear leveling. Because of that people came up with crypto-shredding or crypto erase which only truly works with Hardware Encryption because Software encryption can never, with 100% certainty, know how the wear leveling reacts on every device. You already said this isn't an option so what can you do to be sure nothing can be recovered? The answer is unfortunately short, nothing. However recent research showed that multi pass overwriting caught a lot of data but even the Gutmann method (35 passes) did not get rid of everything (I forgot the link to the Whitepapers). That said, you aren't selling it to a forensic specialist. My best suggestion is to use one of the higher rated wiping apps (Shreddit for example) to first destroy your files, then factory reset and download a few good recovery apps and again a wiping app. Make sure you can't recover your own files anymore (if you have very sensitive data you can connect it to a PC and use even better recovery or, if you are paranoid, forensic tools) then overwrite it with as many passes, rounds and algorithms you feel comfortable with. Check recovery tools again and call it a day when you feel satisfied. This WILL eat at the wear level so keep that in mind when you want to start overdoing it. Not everything will be gone but it's as good as it's going to get and I highly doubt the person you sell it to will be able to recover anything. Good luck! Click to expand... Click to collapse Thanks for your amazing reply! I finally found the solution I was looking for: as Avast! support told me, you can still use Avast! Mobile Security to securely erase your phone (by overwriting data), it's just a hidden feature. You just have to deactivate the Device Administrators permission for the app. Then you just use the "erase device." Was that research about multi pass overwriting done on SSD, or HDD? I always thought that one pass is enough on a standart HDD. Can you recommend me any good forensic tools to use to check if the data is truly erased, please? And does the phone need to be rooted in order to restore deleted data? Thanks for all your insight and advice !
GU42 said: Thanks for your amazing reply! I finally found the solution I was looking for: as Avast! support told me, you can still use Avast! Mobile Security to securely erase your phone (by overwriting data), it's just a hidden feature. You just have to deactivate the Device Administrators permission for the app. Then you just use the "erase device." Was that research about multi pass overwriting done on SSD, or HDD? I always thought that one pass is enough on a standart HDD. Can you recommend me any good forensic tools to use to check if the data is truly erased, please? And does the phone need to be rooted in order to restore deleted data? Thanks for all your insight and advice ! Click to expand... Click to collapse Avasts shredder works but it's a single pass on flash memory so it doesn't clear everything with 100% certainty because of the wear leveling but no algorithm does. I'm pretty sure that's a feature they added after purchasing CCleaner. They also added it as a module in their windows platform. The multi pass research was done on Solid State Drives and I still can't find the link. Just from a research paper in 2011. SSD's are still closest in comparison to the kind of memory used in Mobile devices. As for HDD's it's an open debate. Forensics have claimed to be sble to read past 200 writes in the past but there is no research to support this. I believe that they showed that 1 pass PRNG is enough in 2005, however the DoD was still developing machines to perform 7 pass DoD standard wipes so, I have to say that I have no idea. If you want serious forensic tools you're looking at these kind of distributions (infosec just made me laugh, SSL_ERR_CERT_COMMON_NAME_INVALID, it's infosec! ??). http://resources.infosecinstitute.com/computer-forensics-tools/ But if anyone you sell it to would try something it would be more along the lines of Recuva and similar software. On phones you can just download a bunch of high rated recovery tools and see if anything pops up. You do not need root for most of them. You could run fstrim which I'm pretty sure has no root requirements either. This would mark all blocks as invalid so Garbage Collection can pick it up as well. Even though GC has been show not to clean everything it doesn't hurt.