In iPhone, keychain is a sqllite database which stores sensitive data on the device. Apple’s keychain service is a library/API provided by Apple that developers can use to store sensitive information on an iOS device securely. Instead of storing sensitive information in plaintext configuration files, developers can leverage the keychain services to have the operating system store sensitive information securely on their behalf.
Keychain is encrypted with a hardware key. Hardware key is unique per device and not even accessible to OS running on the device. So even if some one get access to the keychain db file in a remote attack (Remember android malware, which steal sqlite.db files and sent it to the remote server), they cannot decrypt and view the content. Keychain also restricts the application access to the stored data. Each application on your device has a unique application-identifier (also called as entitlements). The keychain service restricts which data an application can access based on this identifier. By default, applications can only access data associated with their own application-identifier. Later apple introduced keychain groups. Now applications which belong to same group can share the keychain items.
On a jailbroken device, all keychain entries can be accessed by writing an application and making it as a member of all application group.
Copy keychain_dumper to iPhone over ssh. Run the below command on SSH Terminal. This extracts all the keychain groups from keychain-2.db and stores in an xml file.
./keychain_dumper -e /var/tmp/entitlements.xml
Using ldid and entitlement xml file, we can make keychain_dumper program as a member of all keychain groups.
ldid -S/var/tmp/entitlements.xml keychain_dumper
Now running keychain dumper reads all the entries from keychain and displays it on the terminal.
On the newer versions of iOS (v5) running this tool ends up with killed 9 error.
The problem here is iOS kernel signature checks the binary file at several places. Jailbreak tools cannot patch all these signature checks because it is difficult for them to patch each and every signature check. When we copy keychaindumper to iPhone, it does not have a signature. So running the binary exits with killed 9 message because iOS kernel does not have the signature of keychain_dumper.
To get rid of this problem add the signature of keychain_dumper to kernel cache (list of hashes) by running the below command. After adding the signature, you can run the rest of commands to dump the keychain entries.
ldid -S keychain_dumper
But in the newer versions (5.0.1), this workaround is not working. Because we have to run ldid command twice with -S option. This tries to overwrite the binary hash on kernel cache and fails. So follow the below listed steps to use the keychain_dumper on newer versions of iOS.
1. Copy keychain_dumper to iPhone over SSH. 2. Manually dump keychain groups with the help of sqlite3 command. > Sqlite3 /var/Keychains/keychain-2.db “select agrp from genp” Running this command on my phone listed three access groups. - apple, com.apple.apsd, com.apple.cfnetwork 3. Create a XML file similar to the sample shown below with all the keychain groups listed by above command (paste the keychain group name in the string tags). Sample.xml
iPhone Forensics goal is extracting data and artifacts from iPhone without altering the information on the device. iPhone forensics can be performed on the backups made by iTunes (escrow key attack) or directly on the live device. This article explains the technical procedure and the challenges involved in extracting data from the live iPhone.
The techniques explained in the article only works for iPhone 3gs, iPhone 4 & iPad1. It does not work for iPhone 4s, iPad 2, iPad 3 and iPad mini.
Techniques explained in the article also works for iOS 6 (Use iOS 5.1.1 ipsw file iOS 6 devices).
Forensics on Live Device:
Jean Sigwald a researcher at Sogeti ESEC Labs has released open source forensic tools (with the support of iOS 5) to recover low level data from the iPhone. Below details outline their research and gives an overview on usage of iPhone forensic tools.
iPhone 4 GSM model, running with iOS 5.1.1 is used for the demos.
Steps involved in iPhone forensics:
Creating & Loading forensic toolkit on to the device without damaging the evidence
Establishing a communication between the device and the computer
Bypassing the iPhone passcode restrictions
Reading the encrypted file system
Recovering the deleted files
1. Creating & Loading forensic toolkit
Imagine a computer which is protected with OS level password - we can still access the hard disk data by booting a live CD or by removing the hard disk and connecting it to other machine. When we compare computers to the iPhone, it is an embedded device. So it is not easy to take out the chips (hard disk) and dump data in it. iPhone makes chip dumping even more complicated by encrypting the data during storage. In order to perform iPhone forensics, we use Live CD approach. As the iPhone has only one serial port, we are going to load custom OS over USB to access hard disk (NAND chip) of the device. But the problem here is, iPhone only loads the firmware which is signed by Apple.
In order to create and load forensic toolkit, first we need to understand iPhone functions at operating system level. iOS (previously known as iPhone OS) is the operating system that runs on all Apple devices like iPhone, iPod, Apple TV and iPad. iOS is a zip file (ships as an .ipsw file) that contains boot loaders, kernel, system software, shared libraries & built in applications.
When an iPhone boots up, it walks through a chain of trust which is a series of RSA signature checks among software components in a specific order as shown in Figure 1.
The BootRom is a Read only memory (ROM) and it is the first stage of booting an iOS device. BootRom contains the Apple root certificates to signature check the next stage.
iPhone operates in 3 modes – Normal Mode, Recovery Mode, DFU mode
In Normal mode, BootRom start off some initialization stuff and loads the low level boot loader (LLB) by verifying its signature. LLB signature checks and loads the stage 2 boot loader (iBoot). iBoot signature checks the kernel & device tree and kernel signature checks all the user applications.
In DFU mode, iPhone follows the boot sequence with a series of signature checks as shown in Figure 2. BootRom signature checks the second level boot loaders (iBSS, iBEC). Boot loader signature checks the kernel and kernel signature checks the Ramdisk.
During iOS update, Ramdisk gets loaded into RAM and it loads all other OS components. In Forensics, we will create a custom Ramdisk with all our forensic tool kit and load it on iPhone volatile memory. Signature checks implemented at various stages in the boot sequence does not allow loading our custom Ramdisk. To load our custom Ramdisk we have to bypass all these signature checks. In the chain of trust boot sequence, if we compromise one link, we can fully control all the links that follow it. The hacker community have found several vulnerabilities in BootRom using which we can flash our own boot loader and patch all other signature checks in all the subsequent stages. Apart from signature checks, every stage is also encrypted. These encryption keys can be grabbed from JailBreaking tools.
Building custom Ramdisk
First we will build a custom Ramdisk with all our forensic tools and patch the Ramdisk signature checks in kernel. Later, we use jailbreak tools to load our kernel by patching BootRom signature checks.
With the open source forensic toolkit released by Sogeti Labs, we can build Ramdisk only on MAC OS X. During this article, Ramdisk is built on MAC OS X 10.6. The entire forensic toolkit contains python scripts, few binaries and few shell scripts.
In order to run the tools, first we need to install all the dependencies (Use the below listed commands from OS X terminal).
Download and install Xcode 4. It installs the required compilers (ex: gcc).
Download ldid, grant execute permissions and move it to /usr/bin directory. ldid is used for signing the binaries.
Download and install OSXFuse. OSXFUSE allows to extend Mac OS X’s native file handling capabilities via third-party file system.
curl -O -L https://github.com/downloads/osxfuse/osxfuse/OSXFUSE-2.3.4.dmg
hdiutil mount OSXFUSE-2.3.4.dmg
sudo installer -pkg /Volumes/FUSE for OS X/Install OSXFUSE 2.3.pkg -target /
hdiutil eject /Volumes/FUSE for OS X/
Download and install Mercurial (http://mercurial.selenic.com/) to check out the source code from the repository.
hg clone https://code.google.com/p/iphone-dataprotection/
Compile img3fs.c which is located in img3fs folder. This script is used to encrypt and decrypt Ramdisk and kernel. If you run into a problem while running this command, edit the makefile in img3fs folder and change the compiler path.
make -C img3fs/
Download redsn0w which is a famous JailBreaking tool. Keys.plist file inside redsn0w contains the encryption keys to decrypt Ramdisk and Kernel.
To patch the signature checks in kernel, supply iOS 5.1.1 ipsw file to kernel_patcher.py. iOS 5.1.1 ipsw file can be downloaded from www.getios.com which maintains all iOS versions for all Apple devices.
The above python script creates a patched kernel and a shell script to create Ramdisk.
Running the shell script downloads the forensic tool kit (ssh.tar.gz) and adds it to the Ramdisk. The Ramdisk image is just a plain HFS+ file system which is native to Mac OS, making it fairly simple to add files to it. All the steps mentioned above create a patched kernel and a custom Ramdisk with forensic tools.
Note: I have created the patched kernel and the custom Ramdisk for iPhone 4. You can directly download these files and skip all the above steps.
In order to load forensic toolkit, supply iOS 5.1.1 ipsw file, patched kernel and custom Ramdisk to redsn0w tool. Connect the device to computer using USB cable and run the below command. Follow the steps displayed by redsn0w to boot the device in DFU mode. In DFU mode, redsn0w exploits the BootRom vulnerability and loads patched kernel & custom Ramdisk on to the device.
If the process fails with the No identifying data fetched error, make sure that the host computer is connected to the internet. After redsn0w is done, the Ramdisk boots in verbose mode. Upon successful boot up, iPhone displays ‘OK’ message.
2. Establishing device to computer communication
Once booted with custom Ramdisk, networking capabilities (like WI-FI) are not enabled by default. So a different way is chosen to communicate with the device by following the approach that Apple took with iTunes. USBMUX is a protocol used by iTunes to talk to the booted iPhone and coordinate access to its iPhone services by other applications. USB multiplexing provides TCP like connectivity over a USB port using SSL. Over this channel iTunes uses AFC service to transfer files. But here we use this channel to establish a SSH connection and get shell access to the device.
SSH works on port 22. Tcprelay.py script redirects port 22 traffic to 2222 port.
At this point, we get access to the file system. To make things even more complicated, every file is encrypted with its own unique encryption key tied to particular iOS device. Furthermore, data protection mechanism introduced with iOS 4 adds another layer of encryption that does not give access to the protected files & keychain items when the device is locked. Data protection is the combination of using hardware based encryption along with a software key. Every iPhone (>3gs) contains a special piece of hardware (AES processor) which handles the encryption with a set of hardcoded keys (UID, GID). OS running on the device cannot read the hardcoded keys but it can use the keys generate by UID (0×835 and 0x89B) for encryption and decryption. Software key is protected by a passcode and is also used to unlock the device every time the user wants to make use of the device. So in order to access the protected files, first we have to bypass the passcode.
3. Bypassing the iPhone passcode restrictions
Initially (< iOS 4), passcode is stored in a file which can be removed directly over SSH. Since the introduction of data protection (from iOS 4), passcode is used to encrypt protected files and keychain items on the device. So in order to decrypt the data, we have to supply the valid passcode.
Passcode validation is performed at two levels one at springboard and another one at kernel level. Brute force attack performed at springboard level locks the device, introduces delays and may lead to data wipe-out. However these protection mechanisms are not applicable at kernel level (AppleKeyStore method) and it leads to brute force attacks. To make brute force attacks less practical, passcode key derived from the user passcode is tied to hardware UID key. So the brute force can only be performed on the device and it is not possible to prepare pre compute values (like rainbow tables) offline. Demo_bruteforce.py script can be used to brute force the 4 digit passcode.
Port 1999 opened with tcprelay.py is used by the brute force script. It connects to the custom restored_external daemon on the Ramdisk, collects basic device information (serial number, UDID, etc.), unique device keys (keys 0×835 and 0x89B), downloads the system keybag and tries to brute force the passcode (4 digits only).
Table 1 illustrates the time required to brute force different types of passcodes.
4. Reading the encrypted file system
Upon successful passcode brute force, the script automatically downloads the keychain. Keychain is a SQLite database which stores sensitive data on your device. Keychain is encrypted with hardware key. Keychain also restrict which applications can access the stored data. Each application on your device has a unique application-identifier (also called as entitlements). The keychain service restricts which data an application can access based on this identifier. By default, applications can only access data associated with their own application-identifier. Later apple introduced keychain groups. Now applications which belong to same group can share the keychain items. There are two ways to access all the keychain items. One way is, by writing an application and making it as a member of all application groups. The other way is by writing an application and granting com.apple.keystore.access-keychain-keys entitlement.
Keychain database contents can be extracted using keychain_tool.py.
To dump the iPhone file system execute the dump_data_partition shell script.
The script reads the file system from the device and copies it to UDID directory as an image (.dmg) file. The image file can be opened using the modified HFSExplorer that will decrypt the files on the fly. To decrypt it permanently, emf_decrypter.py script can be used.
If you are using Gevey unlock and want to upgrade your iPhone to ios 5 , do not directly update it through iTunes. Use redsnow and create a custom os bundle which preserves the old baseband. Detailed steps can be found at - Update to iOS 5 by preserving baseband
After installing iOS 5 you need to activate the phone. Activation is different from unlocking . To activate the phone you will require an original sim (carrier to which the phone is locked). If you do not have the original sim, close iTunes and use redsnow to jailbreak the phone. After jailbreaking, open iTunes and activate the phone.
Now insert your Gevey sim to unlock the iPhone. It works perfectly on iOS 5 and baseband 4.10.1.
Gevey sim problems that I have faced and the solutions
- After the sync with iTunes (over USB), Gevey sim stopped working (you will see no service message). It seems Apple is sending some instructions to phone to disable the Gevey sim. I removed the sim and inserted it again. Then Gevey sim started working.
- To get rid of this problem, I am disconnecting the internet from my machine (on which iTunes is running) while syncing the phone. So far, I did not face any problem with this method.
- After syncing the phone with iTunes over Wi-Fi, Gevey sim stopped working and I spent a lot of time to make it work. One solution that I found is – sync the phone with iTunes (disconnect internet from laptop) over USB then remove the sim and insert it again. Hereafter Gevey sim worked well .
- After downloading GPRS or 3G settings, those settings did not work. To make it work, I restarted the phone, removed the sim and inserted it again.
- If none of those techniques work or if you see invalid sim message: Remove & insert the sim. After few minutes you will see No service message. Dial 112 and end the call in a minute. Turn on airpot and off it in a minute. It will show SIM Failure message. You might get signal by this time. If not, it might have shown you invalid sim message. Now remove the sim and insert it again. And do not do anything. You will see the signal in few minutes.
- If you have jailbroken iOS 5 (currently only tethered jailbreak is available), when you restart the phone you have to use redsnow just boot option to make the phone work. If you Want to restart your phone without connecting it to laptop, one alternative is, use of software restart called respring. Download sbsettings from Cydia and it will show respring option. Now on-wards whenever you want to restart the phone, use respring option.
- Turning on 3g may drops the signal, then remove and insert the sim, gevey displays accept message. Click on it. Wait for 1 minute and dial 112 and hangup. Turn on airplane mode till you see no sim card installed message. Turn off airplane mode. It displays the signal now (even for gevey ultra sim, you have to follow all the steps).
- This technique worked for all kind of signal problems: Remove the sim card when you notice no service message. If you see other messages like invalid sim, turn on and off airplane mode until you see no service message. Insert sim, then gevey displays accept message. Click on it. Wait for 1 minute (you may notice no service message) and dial 112 and hangup. Turn on airplane mode till you see no sim card installed message. Turn off airplane mode. Wait for few seconds. You will notice sim failure, invalid sim message. Later it starts searching for signal and displays the full signal (all the steps are necessary even for gevey ultra sim) .
- Turning on 3g sometimes may show only one signal bar and slowly drops the signal. To get rid of this problem, always first turn on cellular data then turn on 3g.
I have given a presentation on Pentesting iPhone Applications in c0c0n. This presentation mainly focuses on methodology, techniques and the tools that will help security testers while assessing the security of iPhone applications.
Mac OS X default file system is HFS (It also supports FAT 32 file system). If you connect a Pen Drive which is formatted in NTFS format, Mac detects it as a disk. You can read files from disk, but you can not write into it. So if you try to copy some files from Mac to Pen Drive it will not work. To do that, format the Pen Drive in FAT 32 format. Then Mac recognizes it as a hard drive. Now you can drag files from Mac to Pen Drive.
In Mac OS X, everything is complicated. Not as easy as in windows. In Windows if you copy files from NTFS formatted drive to FAT 32 drive, it automatically converts from one format to other. But it takes extra space to store those format conversion details.