| EL3 SPMC Threat Model |
| ********************* |
| |
| ************ |
| Introduction |
| ************ |
| This document provides a threat model for the TF-A :ref:`EL3 Secure Partition Manager` |
| (EL3 SPM) implementation. The EL3 SPM implementation is based on the |
| `Arm Firmware Framework for Arm A-profile`_ specification. |
| |
| ******************** |
| Target of Evaluation |
| ******************** |
| In this threat model, the target of evaluation is the ``Secure Partition Manager Core`` |
| component (SPMC) within the EL3 firmware. |
| The monitor and SPMD at EL3 are covered by the :ref:`Generic TF-A threat model |
| <threat_analysis>`. |
| |
| The scope for this threat model is: |
| |
| - The TF-A implementation for the EL3 SPMC |
| - The implementation complies with the FF-A v1.1 specification. |
| - Secure partition is statically provisioned at boot time. |
| - Focus on the run-time part of the life-cycle (no specific emphasis on boot |
| time, factory firmware provisioning, firmware udpate etc.) |
| - Not covering advanced or invasive physical attacks such as decapsulation, |
| FIB etc. |
| |
| Data Flow Diagram |
| ================= |
| Figure 1 shows a high-level data flow diagram for the SPM split into an SPMD |
| and SPMC component at EL3. The SPMD mostly acts as a relayer/pass-through between |
| the normal world and the secure world. It is assumed to expose small attack surface. |
| |
| A description of each diagram element is given in Table 1. In the diagram, the |
| red broken lines indicate trust boundaries. |
| |
| Components outside of the broken lines are considered untrusted. |
| |
| .. uml:: ../resources/diagrams/plantuml/el3_spm_dfd.puml |
| :caption: Figure 1: EL3 SPMC Data Flow Diagram |
| |
| .. table:: Table 1: EL3 SPMC Data Flow Diagram Description |
| |
| +---------------------+--------------------------------------------------------+ |
| | Diagram Element | Description | |
| +=====================+========================================================+ |
| | DF1 | SP to SPMC communication. FF-A function invocation or | |
| | | implementation-defined Hypervisor call. | |
| | | | |
| | | Note:- To communicate with LSP, SP1 performs a direct | |
| | | message request to SPMC targeting LSP as destination. | |
| +---------------------+--------------------------------------------------------+ |
| | DF2 | SPMC to SPMD communication. | |
| +---------------------+--------------------------------------------------------+ |
| | DF3 | SPMD to NS forwarding. | |
| +---------------------+--------------------------------------------------------+ |
| | DF4 | SPMC to LSP communication. | |
| | | NWd to LSP communication happens through SPMC. | |
| | | LSP can send direct response SP1 or NWd through SPMC. | |
| +---------------------+--------------------------------------------------------+ |
| | DF5 | HW control. | |
| +---------------------+--------------------------------------------------------+ |
| | DF6 | Bootloader image loading. | |
| +---------------------+--------------------------------------------------------+ |
| | DF7 | External memory access. | |
| +---------------------+--------------------------------------------------------+ |
| |
| |
| *************** |
| Threat Analysis |
| *************** |
| |
| This threat model follows a similar methodology to the :ref:`Generic TF-A threat model |
| <threat_analysis>`. The following sections define: |
| |
| - Trust boundaries |
| - Assets |
| - Theat agents |
| - Threat types |
| |
| Trust boundaries |
| ================ |
| |
| - Normal world is untrusted. |
| - Secure world and normal world are separate trust boundaries. |
| - EL3 monitor, SPMD and SPMC are trusted. |
| - Bootloaders (in particular BL1/BL2 if using TF-A) and run-time BL31 are |
| implicitely trusted by the usage of trusted boot. |
| - EL3 monitor, SPMD, SPMC do not trust SPs. |
| |
| Assets |
| ====== |
| |
| The following assets are identified: |
| |
| - SPMC state. |
| - SP state. |
| - Information exchange between endpoints (partition messages). |
| - SPMC secrets (e.g. pointer authentication key when enabled) |
| - SP secrets (e.g. application keys). |
| - Scheduling cycles. |
| - Shared memory. |
| |
| Threat Agents |
| ============= |
| |
| The following threat agents are identified: |
| |
| - Non-secure endpoint (referred NS-Endpoint later): normal world client at |
| NS-EL2 (Hypervisor) or NS-EL1 (VM or OS kernel). |
| - Secure endpoint (referred as S-Endpoint later): typically a secure partition. |
| - Hardware attacks (non-invasive) requiring a physical access to the device, |
| such as bus probing or DRAM stress. |
| |
| Threat types |
| ============ |
| |
| The following threat categories as exposed in the :ref:`Generic TF-A threat model |
| <threat_analysis>` |
| are re-used: |
| |
| - Spoofing |
| - Tampering |
| - Repudiation |
| - Information disclosure |
| - Denial of service |
| - Elevation of privileges |
| |
| Similarly this threat model re-uses the same threat risk ratings. The risk |
| analysis is evaluated based on the environment being ``Server`` or ``Mobile``. |
| IOT is not evaluated as the EL3 SPMC is primarily meant for use in Client. |
| |
| Threat Assessment |
| ================= |
| |
| The following threats are identified by applying STRIDE analysis on each diagram |
| element of the data flow diagram. |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 01 | |
| +========================+====================================================+ |
| | Threat | **An endpoint impersonates the sender | |
| | | FF-A ID in a direct request/response invocation.** | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3, DF4 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMD, SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SP state | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Spoofing | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------++------------------------+ |
| | Impact | Critical(5) | Critical(5) | |
| +------------------------+--------------------------++------------------------+ |
| | Likelihood | Critical(5) | Critical(5) | |
| +------------------------+--------------------------++------------------------+ |
| | Total Risk Rating | Critical(25) | Critical(25) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | SPMC must be able to correctly identify an | |
| | | endpoint and enforce checks to disallow spoofing. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Yes. | |
| | implemented? | The SPMC enforces checks in the direct message | |
| | | request/response interfaces such an endpoint cannot| |
| | | spoof the origin and destination worlds (e.g. a NWd| |
| | | originated message directed to the SWd cannot use a| |
| | | SWd ID as the sender ID). | |
| | | Also enforces check for direct response being sent | |
| | | only to originator of request. | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 02 | |
| +========================+====================================================+ |
| | Threat | **An endpoint impersonates the receiver | |
| | | FF-A ID in a direct request/response invocation.** | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3, DF4 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMD, SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SP state | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Spoofing, Denial of Service | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------++------------------------+ |
| | Impact | Critical(5) | Critical(5) | |
| +------------------------+--------------------------++------------------------+ |
| | Likelihood | Critical(5) | Critical(5) | |
| +------------------------+--------------------------++------------------------+ |
| | Total Risk Rating | Critical(25) | Critical(25) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Validate if endpoind has permission to send | |
| | | request to other endpoint by implementation | |
| | | defined means. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Platform specific. | |
| | implemented? | | |
| | | The guidance below is left for a system integrator | |
| | | to implement as necessary. | |
| | | | |
| | | Additionally a software component residing in the | |
| | | SPMC can be added for the purpose of direct | |
| | | request/response filtering. | |
| | | | |
| | | It can be configured with the list of known IDs | |
| | | and about which interaction can occur between one | |
| | | and another endpoint (e.g. which NWd endpoint ID | |
| | | sends a direct request to which SWd endpoint ID). | |
| | | | |
| | | This component checks the sender/receiver fields | |
| | | for a legitimate communication between endpoints. | |
| | | | |
| | | A similar component can exist in the OS kernel | |
| | | driver, or Hypervisor although it remains untrusted| |
| | | by the SPMD/SPMC. | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 03 | |
| +========================+====================================================+ |
| | Threat | **Tampering with memory shared between an endpoint | |
| | | and the SPMC.** | |
| | | | |
| | | A malicious endpoint may attempt tampering with its| |
| | | RX/TX buffer contents while the SPMC is processing | |
| | | it (TOCTOU). | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF3, DF7 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | Shared memory, Information exchange | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Tampering | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | High (4) | High (4) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | High (4) | High (4) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | High (16) | High (16) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Validate all inputs, copy before use. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Yes. In context of FF-A v1.1 this is the case of | |
| | implemented? | sharing the RX/TX buffer pair and usage in the | |
| | | PARTITION_INFO_GET or memory sharing primitives. | |
| | | | |
| | | The SPMC copies the contents of the TX buffer | |
| | | to an internal temporary buffer before processing | |
| | | its contents. The SPMC implements hardened input | |
| | | validation on data transmitted through the TX | |
| | | buffer by an untrusted endpoint. | |
| | | | |
| | | The TF-A SPMC enforces | |
| | | checks on data transmitted through RX/TX buffers. | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 04 | |
| +========================+====================================================+ |
| | Threat | **An endpoint may tamper with its own state or the | |
| | | state of another endpoint.** | |
| | | | |
| | | A malicious endpoint may attempt violating: | |
| | | | |
| | | - its own or another SP state by using an unusual | |
| | | combination (or out-of-order) FF-A function | |
| | | invocations. | |
| | | This can also be an endpoint emitting FF-A | |
| | | function invocations to another endpoint while | |
| | | the latter in not in a state to receive it (e.g. | |
| | | SP sends a direct request to the normal world | |
| | | early while the normal world is not booted yet). | |
| | | - the SPMC state itself by employing unexpected | |
| | | transitions in FF-A memory sharing, direct | |
| | | requests and responses, or handling of interrupts| |
| | | This can be led by random stimuli injection or | |
| | | fuzzing. | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMD, SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SP state, SPMC state | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Tampering | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | High (4) | High (4) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | High (12) | High (12) | |
| +------------------------+------------------+-----------------+---------------+ |
| | Mitigations | Follow guidelines in FF-A v1.1 specification on | |
| | | state transitions (run-time model). | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Yes. The TF-A SPMC is hardened to follow this | |
| | implemented? | guidance. | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 05 | |
| +========================+====================================================+ |
| | Threat | **Replay fragments of past communication between | |
| | | endpoints.** | |
| | | | |
| | | A malicious endpoint may replay a message exchange | |
| | | that occurred between two legitimate endpoints as | |
| | | a matter of triggering a malfunction or extracting | |
| | | secrets from the receiving endpoint. In particular | |
| | | the memory sharing operation with fragmented | |
| | | messages between an endpoint and the SPMC may be | |
| | | replayed by a malicious agent as a matter of | |
| | | getting access or gaining permissions to a memory | |
| | | region which does not belong to this agent. | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF2, DF3 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | Information exchange | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Repudiation | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | High (4) | High (4) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | High (12) | High (12) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Strict input validation and state tracking. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Platform specific. | |
| | implemented? | | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 06 | |
| +========================+====================================================+ |
| | Threat | **A malicious endpoint may attempt to extract data | |
| | | or state information by the use of invalid or | |
| | | incorrect input arguments.** | |
| | | | |
| | | Lack of input parameter validation or side effects | |
| | | of maliciously forged input parameters might affect| |
| | | the SPMC. | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMD, SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SP secrets, SPMC secrets, SP state, SPMC state | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Information discolure | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | High (4) | High (4) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | High (12) | High (12) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | SPMC must be prepared to receive incorrect input | |
| | | data from secure partitions and reject them | |
| | | appropriately. | |
| | | The use of software (canaries) or hardware | |
| | | hardening techniques (XN, WXN, pointer | |
| | | authentication) helps detecting and stopping | |
| | | an exploitation early. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Yes. The TF-A SPMC mitigates this threat by | |
| | implemented? | implementing stack protector, pointer | |
| | | authentication, XN, WXN, security hardening | |
| | | techniques. | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 07 | |
| +========================+====================================================+ |
| | Threat | **A malicious endpoint may forge a direct message | |
| | | request such that it reveals the internal state of | |
| | | another endpoint through the direct message | |
| | | response.** | |
| | | | |
| | | The secure partition or SPMC replies to a partition| |
| | | message by a direct message response with | |
| | | information which may reveal its internal state | |
| | | (e.g. partition message response outside of | |
| | | allowed bounds). | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SPMC or SP state | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Information discolure | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | Low (2) | Low (2) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | Medium (6) | Medium (6) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Follow FF-A specification about state transitions, | |
| | | run time model, do input validation. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Yes. For the specific case of direct requests | |
| | implemented? | targeting the SPMC, the latter is hardened to | |
| | | prevent its internal state or the state of an SP | |
| | | to be revealed through a direct message response. | |
| | | Further FF-A v1.1 guidance about run time models | |
| | | and partition states is followed. | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 08 | |
| +========================+====================================================+ |
| | Threat | **Probing the FF-A communication between | |
| | | endpoints.** | |
| | | | |
| | | SPMC and SPs are typically loaded to external | |
| | | memory (protected by a TrustZone memory | |
| | | controller). A malicious agent may use non invasive| |
| | | methods to probe the external memory bus and | |
| | | extract the traffic between an SP and the SPMC or | |
| | | among SPs when shared buffers are held in external | |
| | | memory. | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF7 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SP/SPMC state, SP/SPMC secrets | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | Hardware attack | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Information disclosure | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | Low (2) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | Medium (6) | Medium (9) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Implement DRAM protection techniques using | |
| | | hardware countermeasures at platform or chip level.| |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Platform specific. | |
| | implemented? | | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 09 | |
| +========================+====================================================+ |
| | Threat | **A malicious agent may attempt revealing the SPMC | |
| | | state or secrets by the use of software-based cache| |
| | | side-channel attack techniques.** | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF7 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SP or SPMC state | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Information disclosure | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | Low (2) | Low (2) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | Medium (6) | Medium (6) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | The SPMC may be hardened further with SW | |
| | | mitigations (e.g. speculation barriers) for the | |
| | | cases not covered in HW. Usage of hardened | |
| | | compilers and appropriate options, code inspection | |
| | | are recommended ways to mitigate Spectre types of | |
| | | attacks. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | No. | |
| | implemented? | | |
| +------------------------+----------------------------------------------------+ |
| |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 10 | |
| +========================+====================================================+ |
| | Threat | **A malicious endpoint may attempt flooding the | |
| | | SPMC with requests targeting a service within an | |
| | | endpoint such that it denies another endpoint to | |
| | | access this service.** | |
| | | | |
| | | Similarly, the malicious endpoint may target a | |
| | | a service within an endpoint such that the latter | |
| | | is unable to request services from another | |
| | | endpoint. | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SPMC state, Scheduling cycles | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Denial of service | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | Medium (9) | Medium (9) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Bounding the time for operations to complete can | |
| | | be achieved by the usage of a trusted watchdog. | |
| | | Other quality of service monitoring can be achieved| |
| | | in the SPMC such as counting a number of operations| |
| | | in a limited timeframe. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Platform specific. | |
| | implemented? | | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 11 | |
| +========================+====================================================+ |
| | Threat | **Denying a lender endpoint to make progress if | |
| | | borrower endpoint encountered a fatal exception. | |
| | | Denying a new sender endpoint to make progress | |
| | | if receiver encountered a fatal exception.** | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | Shared resources, Scheduling cycles. | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Denial of service | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | Medium (3) | Medium (3) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | Medium (9) | Medium (9) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | SPMC must be able to detect fatal error in SP and | |
| | | take ownership of shared resources. It should | |
| | | be able to relinquish the access to shared memory | |
| | | regions to allow lender to proceed. | |
| | | SPMC must return ABORTED if new direct requests are| |
| | | targeted to SP which has had a fatal error. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Platform specific. | |
| | implemented? | | |
| +------------------------+----------------------------------------------------+ |
| |
| +------------------------+----------------------------------------------------+ |
| | ID | 12 | |
| +========================+====================================================+ |
| | Threat | **A malicious endpoint may attempt to donate, | |
| | | share, lend, relinquish or reclaim unauthorized | |
| | | memory region.** | |
| +------------------------+----------------------------------------------------+ |
| | Diagram Elements | DF1, DF2, DF3 | |
| +------------------------+----------------------------------------------------+ |
| | Affected TF-A | SPMC | |
| | Components | | |
| +------------------------+----------------------------------------------------+ |
| | Assets | SP secrets, SPMC secrets, SP state, SPMC state | |
| +------------------------+----------------------------------------------------+ |
| | Threat Agent | NS-Endpoint, S-Endpoint | |
| +------------------------+----------------------------------------------------+ |
| | Threat Type | Elevation of Privilege | |
| +------------------------+--------------------------+-------------------------+ |
| | Application | Server | Mobile | |
| +------------------------+--------------------------+-------------------------+ |
| | Impact | High (4) | High (4) | |
| +------------------------+--------------------------+-------------------------+ |
| | Likelihood | High (4) | High (4) | |
| +------------------------+--------------------------+-------------------------+ |
| | Total Risk Rating | High (16) | High (16) | |
| +------------------------+--------------------------+-------------------------+ |
| | Mitigations | Follow FF-A specification guidelines | |
| | | on Memory management transactions. | |
| +------------------------+----------------------------------------------------+ |
| | Mitigations | Yes. The SPMC tracks ownership and access state | |
| | implemented? | for memory transactions appropriately, and | |
| | | validating the same for all operations. | |
| | | SPMC follows FF-A v1.1 | |
| | | guidance for memory transaction lifecycle. | |
| +------------------------+----------------------------------------------------+ |
| |
| --------------- |
| |
| *Copyright (c) 2022-2023, Arm Limited. All rights reserved.* |
| |
| .. _Arm Firmware Framework for Arm A-profile: https://developer.arm.com/docs/den0077/latest |
| .. _FF-A ACS: https://github.com/ARM-software/ff-a-acs/releases |