The standard may have extensions, such as the e. MMC Security Extension. For more information about flash technologies, check our additional resources:.
The eMMC is an evolving standard. MMCElectrical Standard 5.
The eMMC standard provides an interface in which the device is seen and treated as a block device by Linux. On the other hand, eMMC is widely different from those and its peculiarities must be taken into consideration when choosing and configuring the file system.
As of the embedded Linux BSP 2. The eMMC device has a boot areawhich is seen as a different block device than the regular user area.
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From the above output, notice that boot area does not have a partition table. In addition, the user area size is bytesbeing bytes for the kernel and device tree partition and bytes for the root file system. Alternatively, one could get the block devices and partition sizes using the command lsblk :. Using the command dfyou'll notice that the size reported by the file systems is slightly smaller than the user area partitions:.
From the command above the total size of the kernel and device tree partition is bytes and the root file system is bytes. This reports the actual usable space for each partition and happens due to file system overhead - things such as the inode table and file system journal.
Even though discouraged, it is possible to copy the eMMC contents for backup or replication purposes. There is a specific article for this topic:. The Linux kernel provides a tool chest for configuring MMC devices from user space named mmc-utils.
If you want to use the upstream version, it can be easily built using OpenEmbedded. Both variants upstream and downstream can be built and installed concurrently in the same image, due to update-alternatives support. Mmc-utils makes it possible to query information from the device as well as configure features.
Some examples are health statusenhanced user areawrite reliabilitysanitizecache and write protection.
JEDEC Announces Publication of New MMC V4.4 Specification
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I have a question about the RPMB rollback protection counter, according to the RPMB specification, when a write operation is issued to the RPMB partition, this partition will compare a physical counter inside this partition to the counter that the write operation has, if it is equal, then continue the next check HMAC,etc.
If the write operation is validated, this physical counter will increase by 1. Now here comes my question:. Learn more. Asked 3 years, 3 months ago. Active 2 years, 10 months ago.
Viewed times. Or everytime when we create a small chunk inside, then RPMB patition will have a counter associated to it? What is the size of this counter?
What will happen if there are too many write operations and then overflows? If overflow happened, will the RPMB protect still valid? Or no more write operations are allowed?
Dream in the wind Dream in the wind 79 7 7 bronze badges. Active Oldest Votes. After all, I got the answer: Yes,there is a unique global counter, which does not depend on the partition creation in RPMB.
Instead, this global counter will increase by 1 every time after a valid write operation. According to RPMB reference, it is 32 bit. Currently there is no handle case if the counter overflow since write to RPMB use case is very few.Most of our embedded devices use eMMC, but security into eMMC as far as I know has not been extensively studied or taken account of in threat models.
If you look at the Android platform, kernel hacks are not uncommon and remote kernel hacks are also not a rarity. There are certain commands that a hacker can send which can permanently disable brick a device. Permanent write protect can be enabled on the main partition or any of the boot partitions. A malicious entity with kernel access to the device can wipe the bootloader and enable permanent write protect and prevent any even hardware based recovery.
Card lock will lock the eMMC with a password. No data would be accessible without the password. An adversary could hold your data for hostage and demand payment for a hardware unlocking solution. This is not meant to be an exhaustive list. There are other attack vectors to watch out for too. For example, if the device uses the RPMB to prevent downgrades, an attacker may corrupt it and prevent boot.
The main takeaway here is that having raw eMMC access is dangerous. This only affected a small number of users who choose to hack their 3DS with Gateway. However, in the future, we may see an expansion of these kinds of attacks on mobile devices. The eMMC specifications provides a means of disabling any potentially destructive features either at power-on or permanently. Care must be taken in implementing this solution as reset attacks have to be prevented.
Also, this will not prevent any hardware based bricking, although it is unlikely that such a thing can happen remotely. Permanent disable of features like card lock and write protect will prevent the commands for enabling them from ever working. Device manufacturers who choose to do this must be sure that they would never need to use such a feature in the future.
This is the safest solution. As a user who wants to secure their eMMC based devices, you can obtain root access and run the permanent disable commands, although such a task is obviously dangerous and should only be attempted by someone with knowledge of eMMC. I hope to write an Android app at some point that can perform this operation, although it is very low priority for me at this point.
Overall, I think more research should be done on the topic of eMMC security. Someone with the resources should perform a study to see how many percentage of devices in the wild has the potential to be compromised with an eMMC attack. I know RAM dumps are not possible for the vita because it shares the same board as the other components. Then someone would have to find a way to dump the modification back onto the cartridge and see what happens.
It is sort of how the PSP was hacked. The only flaws in this method is that it would be rather inconvenient for anyone who just wanted to play a SNES emulator on there vita because they would have knowledge and the tools to do what I have described. Maybe sometime in the near future there maybe a PSvita cartridge reader to make whole process easier.
But, I do have my doubts. Your email address will not be published. Twitter LinkedIn GitHub. Search for:. Solutions The eMMC specifications provides a means of disabling any potentially destructive features either at power-on or permanently.
Comments Funny how no one ever tells you these things. June 06, at PM. Do you think it makes sense to do this as a precaution on a hacked 3ds? It might only be a matter of time before someone releases a malicious homebrew.This specification mandates that it should be possible to store general-purpose data and key material that guarantees confidentiality and integrity of the data stored and the atomicity of the operations that modifies the storage atomicity here means that either the entire operation completes successfully or no write is done.
It is possible to use the normal world file systems and the RPMB implementations simultaneously. Depending on the compile-time configuration, one or several values may be used. TEE supplicant will receive the messages and store the encrypted data accordingly to the Linux file system. Reading files are handled in a similar manner. Each persistent object is assigned an internal identifier. All normal world files are integrity protected and encrypted, as described below.
Key manager is a component in TEE file system, and is responsible for handling data encryption and decryption and also management of the sensitive key materials. Currently, in OP-TEE OS we only have a per-device key, SSK, which is used for secure storage subsystem, but, for the future we might need to create different per-device keys for different subsystems using the same algorithm as we generate the SSK; An easy way to generate different per-device keys for different subsystems is using different static strings to generate the keys.
The hash tree is responsible for handling data encryption and decryption of a secure storage file. All fields header, nodes, and blocks are duplicated with two versions, 0 and 1, to ensure atomic updates.
According to GlobalPlatform Trusted Storage requirement of the atomicity, the following operations should support atomic update:. This part is common with the REE-based filesystem. The device operations all have to go through the normal world. HMAC authentication is implemented here also.
Block encryption protects file data.
The FAT is not encrypted. For all platforms, a constant key is used, resulting in no protection against decryption, or Secure Storage duplication to other devices. This is because information about how to retrieve key data from the SoC is considered sensitive by the vendors and it is not publicly available. But there are no existing platform implementations.
To allow Secure Storage to operate securely on your platform, you must define implementations in your platform code for:. These implementations should fetch the key data from your SoC-specific e-fuses, or crypto unit according to the method defined by your SoC vendor. OP-TEE documentation latest. It is described in this document and is the default implementation.
The Trusted Storage may be backed by non-secure resources as long as suitable cryptographic protection is applied, which MUST be as strong as the means used to protect the TEE code and data itself.
Ability to hide sensitive key material from the TA itself.
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Each TA has access to its own storage space that is shared among all the instances of that TA but separated from the other TAs. The Trusted Storage must provide a minimum level of protection against rollback attacks. It is accepted that the actually physical storage may be in an insecure area and so is vulnerable to actions from outside of the TEE.
Typically, an implementation may rely on the REE for that purpose protection level or on hardware assets controlled by the TEE protection level The architecture is depicted below. The FAT grows dynamically as files are added to the filesystem. Among other things, each entry has the start address for the file data, its size, and the filename.
Starting from the end of the RPMB partition and extending downwards is the file data area. The FAT block for the modified file is always updated last, after data have been written successfully. Otherwise, or if the file needs to be extended, a new file is created. RPMB operations are the following: Reading device information partition size, reliable write block count.This document provides an overview of the Trusty architecture for Linux-based system, what security services Trusty provides, and how Trusty works on top of the ACRN Hypervisor.
As shown in Figure below, it consists of:. Figure Trusty Architecture. Intel enables Trusty implementation on x86 based platforms with hardware virtualization technology e. VT-x and VT-d. The purpose of this secure monitor hypervisor is to isolate the normal and secure worlds, and to schedule Trusty OS in and out on demand.
In the Trusty implementation, all the security services provided by Trusty OS in the secure world are event-driven. The normal world and secure world share the same processor resources, so this minimizes the context switching performance penalty.
In Trusty OS, the kernel is a derivative of the Little Kernel projectan embedded kernel supporting multi-thread, interrupt management, MMU, scheduling, and more. Google engineers added user-mode application support and a syscall layer to support privilege level isolation, so that each Trusted App can run in an isolated virtual address space to enhance application security.
For security reasons and for serving early-boot time security requests e. Typically, Trusty provides APIs for developing two classes of applications:. Software running in normal world can use Trusty client library APIs to connect to trusted applications and exchange arbitrary messages with them, just like a network service over IP. It is up to the application to determine the data format and semantics of these messages using an app-level protocol.
Reliable delivery of messages is guaranteed by the underlying Trusty infrastructure Trusty Driversand the communication is completely asynchronous. The differences truly depend on the security services that normal world OS would like to have. In embedded products such as an automotive IVI system, the most important security services requested by customers are keystore and secure storage.
In this article we will focus on these two services. Protocol elements, such as purpose, mode and padding, as well as access control constraints, are specified when keys are generated or imported and are permanently bound to the key, ensuring the key cannot be used in any other way. In addition to the list above, there is one more service that Keymaster implementations provide, but which is not exposed as an API: Random number generation.
This is used internally for generation of keys, Initialization Vectors IVsrandom padding, and other elements of secure protocols that require randomness. Using Android as an example, Keystore functions are explained in greater details in this Android keymaster functions document. As shown in Figure above, the Keymaster HAL is a dynamically-loadable library used by the Keystore service to provide hardware-backed cryptographic services.
The purpose of the Keymaster HAL is only to marshal and unmarshal requests to the secure world. The details of how RPMB works are out of scope in this article. This secure storage can provide data confidentiality, integrity, and anti-replay protection.MMC V4. This benefits product developers by simplifying the non- volatile memory interface design and qualification process — resulting in a reduction in time-to-market as well as facilitating support for future flash device offerings.
The new MMC V4. Also included in the new standard is the introduction of a flexible partition management system, in addition to allowing partitions to be set and operated in an enhanced performance mode, thereby offering improved performance and endurance for selective data.
Several key security enhancements are provided in the new standard, including increased write protection management, introduction of a secure access-controlled memory block and secure erase and trim for secure data erase operations.
Various usage models can now be supported with both permanent and temporary write protection methods, allowing write protection to be selectively applied to user data as well as boot areas. The introduction of a Replay Protected Memory Block RPMB allows for a portion of memory to be accessed with a hidden security key, providing secure storage for the host to protect crucial programs or data, as well as enable copy protection.
Information Security Stack Exchange is a question and answer site for information security professionals. It only takes a minute to sign up. Can anyone explain to me how to use RPMB and how it can actually mitigate replay attacks? It can withstand replay attacks by requiring a key to write to this region. The rpmb has a key that can be programmed once. Later, the host reads a counter value from the rpmb.
It uses this counter value and the programmed key to generate a MAC. The device then checks the MAC given vs the MAC it calculated using the same key, and if it matches, write access is granted referenceslide 4.
Typically, before any access e. This can ensure the data freshness, however, once the counter reaches its max value bitany write access will be denied it means that the RPMB will be a read-only storage. While the Software generated Random Number nonce is used for replay-protection on READ access, because on read access, the software in TEE is responsible for authenticating the data and verifying its freshness, it must never use the same nonce or a poor random number generator to generate nonce to prevent data replay for read access.
For more details, you can see my talk in Linux Security Summit Europe Implement Android Tamper-Resistant Secure Storage and Secure it in Virtualizationin this slides, by the way, it also talks about one of RPMB virtualization solutions on top of hypervisor if you're interested in.
Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Ask Question. Asked 2 years, 8 months ago. Active 5 months ago. Viewed 10k times. Satya Satya 61 1 1 gold badge 1 1 silver badge 5 5 bronze badges. Active Oldest Votes.
RPMB can be used using mmc-utils. Ryan Schaefer Ryan Schaefer 61 1 1 silver badge 3 3 bronze badges.