A typical computer may contain a trusted platform module (TPM), which typically is an integrated circuit that includes a cryptographic processor and a secure memory. The TPM typically forms the root of trust for the computer in conjunction with the computer's basic input/output system (BIOS). In this regard, the TPM may be regarded as a root of trust for reporting and a root of trust for storage, in that the TPM securely stores various cryptographic keys and measurements of the computer's software and hardware configurations (as measured by the BIOS).
Referring to
As non-limiting examples, the processor-based machine 10 may be a desktop computer; a portable computer; a tablet computer; a server; a wide area network (WAN) server; an Internet-based server; a cloud server; a client; a thin client; a cellular telephone; a smartphone; or in general, any machine that includes at least one processor 24 (a microprocessor, a microcontroller, a processing core of such a microprocessor or microcontroller, and so forth). Regardless of its particular form, the processor-based machine 10 is a physical machine that is formed from a physical platform, or physical hardware 20, and machine executable instructions 50, or software, in accordance with example implementations.
In addition to the physical TPM 40 and the processor(s) 24, the processor-based machine 10 may contain various other physical hardware components, such as, for example, components that form a memory 28 of the machine 10. In general, the memory 28 may be a system memory, a cache memory, a microprocessor-based memory, a memory internal to a processor 24, a memory external to a processor 24, a combination of such memories, and so forth, depending on the particular implementation. Moreover, the memory 28 is a non-transitory memory and may be formed from such memory devices as semiconductor devices, optical storage devices, phase change memory devices, magnetic storage devices, and so forth. One or more (even all) of the hardware components of the processor-based machine 10 may be part of the same integrated circuit or may be parts of intercoupled integrated circuits, depending on the particular implementation.
As further disclosed herein, the processor-based machine 10 may have one or more virtual components, in accordance with example implementations. In this manner, the processor-based machine 10 may include a hypervisor, or virtual machine monitor (VMM) 68, that virtualizes the machine's hardware 20 to provide virtual operating platforms to allow guest virtual machines (herein called “guest VMs 60”) to execute, or run, concurrently on the machine 10. Thus, in general, each guest VM 60 is unaware of the existence of the other guest VM(s) 60, and each guest VM 60 perceives its virtual operating platform as a physical platform.
A given guest VM 60, during its course of operation, may receive a request from a verifier, for attestation of the guest VM's virtual platform. More specifically, as further described herein, the verifier requests a virtualized TPM (called a “virtual TPM” herein) to attest for the guest VM 60. The verifier may be an entity (an application or an Internet server, as examples) that is external to the processor-based machine 10 and may or may not be a trusted third party. For purposes of providing sufficient proof to the verifier, the guest VM 60 may rely on a virtualized version of the physical TPM 40 to provide the information to attest to the VM's authenticity.
One way to virtualize the physical TPM 40 is for the physical TPM 40 to securely store the secrets (keys, measurements, certificates and so forth) for the guest VMs 60, so that the physical TPM 40 may be used to attest to a given guest VM's authenticity. However, reliance on such a scheme may be relatively challenging, as the physical TPM 40 may be relatively incapable of serving more than one platform and providing the appropriate security to partition the stored secured data among the guest VMs 60. Moreover, for such an approach, a high degree of trust is afforded to the VMM 68, as the VMM 68 has access to the secrets of all of the guest VMs 60. Lastly, such an approach may be challenging for migration purposes due to the relatively difficult and resource consuming challenges of migrating secrets between physical TPMs that reside on different physical platforms when guest VMs are migrated between those platforms.
In accordance with the systems and techniques that are disclosed herein, the processor-based machine 10 virtualizes the physical TPM 40 for its guest VMs 60 using one or multiple virtual trusted platform modules (TPMs) 70 (herein called “virtual TPMs 70”). The virtual TPM 70, in turn, may be used to provide information to a requesting verifier to attest to the authenticity of an associated guest VM 60.
The virtual TPMs 70 may be viewed as virtualized versions of the physical TPM 40 for the guest VMs 60: each virtual TPM 70 serves as the roots of trust for measurement and storage for an associated guest VM 60. In accordance with example implementations that are disclosed herein, the processor-based machine 10 bind a given virtual TPM 70 to a given guest VM 60. After a given virtual TPM 70 is bound to a given guest VM 60, the processor-based machine 10 does not re-assign the given virtual TPM 70 to another guest VM 60, regardless of whether the originally-assigned guest VM 60 is migrated or retired.
In accordance with the systems and techniques that are disclosed herein, the virtual TPM 70 is contained within a secure enclave 30 of the processor-based machine 10. The secure enclave 30 protects the secrets of the virtual TPM 70 without involving the direct use of the physical TPM 40; and the secure enclave 30 protects the secrets of the virtual TPM 70 from the firmware, the VMM 68 and other processes that are running, or executing, on the processor-based machine 10.
In general, a secure enclave 30 is a set of memory locations that provides a safe place for an application to execute program instructions and store data inside the enclave 30 in the context of an operating system (OS) process. Thus, an application that executes in this environment is called an “enclave.” Enclaves are executed from an enclave page cache, and the enclave pages are loaded into the enclave page cache by an operating system. Whenever a page of a secure enclave 30 is removed from the enclave page cache, cryptographic protections are used to protect the confidentiality of the page and to detect tampering when the page is loaded back into the enclave page cache. Inside the enclave page cache, enclave data is protected using access control mechanisms, which are provided by the processor(s) 24, and the pages of the page cache are also encrypted.
In general, the enclave page cache is where enclave code is temporarily stored in its encrypted state. The enclave code is fetched from the enclave page cache, decrypted and placed in the processor cache where the code is retrieved and executed in the same manner as non-enclave code, and where enclave data is accessed by the processor 24. Thus, in general, the hardware of the processor-based machine 10 provides a mechanism for protecting certain memory locations, and as described herein, this mechanism is used to protect the virtual TPMs 70. In general, the enclave page cache may be located within the physical address space of the processor-based machine 10, and the enclave page cache may be accessed solely through the use of secure enclave instructions, which are a subset of instructions executed by the processor(s) 24. It is noted that the enclave page cache may contain pages from many different secure enclaves 30 and may provide access control mechanisms to protect the integrity and confidentiality of the pages. The enclave page cache maintains a coherency protocol similar to the one used to preserve coherent physical memory accesses in the processor-based machine 10.
The enclave page cache uses an enclave page cache map, which contains the state information associated with each page in the enclave page cache. The state information indicates information such as the particular enclave 30 to which a given page belongs, the state of a loaded page, and so forth. When a page is removed from the enclave page cache, the state information is exported from the enclave page cache map as well as protected using cryptographic means. Similarly, when a given enclave page is re-loaded into the enclave page cache, the state information is verified.
It is noted that the enclave page cache may be stored in many different types of memories, depending on the particular implementation. For example, in accordance with some implementations, the enclave page cache may be stored on board static random access memory (SRAM) of a given processor 24. As another example, the enclave page cache may be stored as part of a dynamic random access memory (DRAM) that is disposed on the processor 24 or disposed separately from the processor 24. The enclave page cache may also be constructed by dynamically sequestering ways of the processor's last-level cache. For these implementations, the enclave page cache may be protected from unauthorized accesses from outside the processor package, while allowing other packages in the system to access the enclave page cache coherently yet securely.
In further implementations, the enclave page cache may be a cryptographic memory aperture, which may provide a relatively cost-effective mechanism of creating cryptographically-protected volatile storage using DRAM. In this manner, the cryptographic memory aperture uses one or more strategically-placed cryptographic units in a region outside of a processing core of the processor 24 (when the processor 24 is a central processing unit (CPU), for example) to provide varying levels of protection. The various uncore agents are modified to recognize the memory accesses going to the cryptographic memory aperture and to route these accesses to a cryptographic controller located in the uncore. The cryptographic controller, depending on the desired protection level, generates one or more memory accesses to the platform DRAM to fetch the cipher text. The fetch text is then processed by the cryptographic controller to generate the plain text to satisfy the original cryptographic memory aperture request.
In accordance with some implementations, the enclave page cache is kept as a separate container, which is managed by microcode of a processor 24. In this manner, the container is not accessible when execution is outside of the secure enclave 30. When the secure enclave 30 is entered, control is transferred to the enclave code inside the enclave page cache, which is contained in a separate container.
Any page faults or exceptions that occur while executing inside of the enclave 30 are reflected by the microcode to the responsible operating system or VMM. When the processor-based machine 10 is executing outside of any of the enclaves 30, access control to the enclave page cache may be provided by a secure enclave range register of the processor 24. In this manner, the processor-based machine 10, when running inside the microcode, provides page table level protections that prevent access to other enclave page cache entries that do not belong to the executing secure enclave 30. Thus, one option to implement the secure enclaves 30 is to implement the instructions and the protections using the microcode capability of the processor 24.
More details about example implementations of the secure enclave 30 may be found, for example, in PCT Publication No. WO 2011/078855 A1, entitled, “METHOD AND APPARATUS TO PROVIDE SECURE APPLICATION EXECUTION,” which published on Jun. 30, 2011.
As further described below, a given virtual TPM 70 is initialized using certain values that uniquely describe the virtual TPM 70 (and allows the virtual TPM 70 to present itself as a valid virtual TPM) and provide information about the trust state of the underlying physical platform. The virtual TPM 70 may be provisioned by assigning keys to an initialized virtual TPM 70, as also further described below, and thereafter, the provisional virtual TPM 70 may be assigned to one of the guest VMs 60.
In addition to the guest VMs 60, VMM 68, BIOS 54 and virtual TPMs 70, the machine executable instructions 50, or software, of the processor-based machine 10 may further include such other instructions 50, as instructions 50 that when executed, form a host operating system 56 and system VMs 64, which control the provisioning and creation of the guest VMs 60, as further described below. Moreover, as depicted in
Referring to
The system VM 64-1 may also include a migration agent 106, which, as its name implies, manages guest VM migration. In this manner, the migration agent 106 may, for example, manage the copying of a guest VM 60 from the processor-based machine 10 to another physical platform to which the guest VM 60 is being migrated and deletes a copy of a guest VM 60 after the guest VM 60 has been migrated.
The system VM 64-2, in accordance with example implementations, contains the virtual TPMs 70 as well as the virtual TPM supervisors 74. The system VM 64-2 contains a guest operating system 120, as well as a guest basic input-output-operating system (BIOS) 124. The guest operating system 120, in turn, includes drivers 130, which permit communication between a given guest VM 60 and virtual TPM 70 pair. In this manner, each guest VM 60 contains a TPM driver 144 (part of the guest operating system 140 of the guest VM 60), which establishes communication (through the VMM 68) between the guest VM 60 and its assigned virtual TPM 70.
Referring to
The virtual TPM 70 stores private keys 221, which are stored in the virtual TPM 70 when the TPM 70 is provisioned. As a more specific example, a given key 221 may be a private key of a private and public key pair, which uniquely identifies the virtual TPM 70. The keys 221 of the virtual TPM 70, in accordance with example implementations, do not venture beyond the boundaries of the associated secure enclave 30. In this manner, the virtual TPM 70 carries secure information, such as the keys 221 and certificates signed with the keys 221, between platforms and is migrated as its associated guest VM 60 is migrated.
As a more specific example, the keys 221 of a given virtual TPM 70 may include a private key of a public and private key Rivest-Shamir-Adleman (RSA) key pair, which uniquely identifies the virtual TPM 70. The virtual TPM 70 may further store a private key of a private and public attestation key pair, which is used for purposes of authenticating the virtual TPM 70 (and its associated guest VM 60) to a requesting verifier. Moreover, the virtual TPM 70 may further store various certificates, such as certificates signed by associated attestation identity keys, and so forth.
Referring to
For purposes of preserving the privacy of the processor-based machine 10 (and users that use the processor-based machine 10), the DAA architecture 200 employs the use of group private and public identity keys. As an example, in accordance with some implementations, the group private and public keys may be a private key-public key pair of Intel Corporation's cryptographic scheme called, “Enhanced Privacy Identification (EPID).” As described in the examples below, in accordance with some implementations, the TPM 70 stores a private group identity key 210 of a private-public group identity key pair, which is formed from the private group identity key 210 and a public group identity key 224.
The private-public group identity key pair permits the virtual TPM 70 to prove to the verifier 198 that the TPM 70 is a valid device made and certified by the given hardware manufacturer, without revealing the identity of the virtual TPM 70 and without the verifier 198 being able to link multiple authentication attempts made by the TPM 70.
More specifically, in accordance with example implementations, the virtual TPM 70 responds to a given authentication request from the verifier 198 with an attestation identification key (AIK) and an attestation identification certificate (AIC), which is signed using the private group identity key 210. The verifier 198, in response to receiving the AIK and the corresponding AIC, verifies that the virtual TPM 70 is an authentic device made by the given hardware manufacturer through the use of the public group identity key 224.
More specifically, for the given example of
The use of the public-private group identity key pair for purposes of remotely and anonymously certifying the virtual TPM 70 works as follows. A given public group identity key 224 may be associated with many private group identity keys 210, with each public-private key pair forming a unique identification. It is noted that a private group identity key 210 may join a given group of virtual TPMs 70 at provisioning time of the virtual TPMs 70 after the processor-based system 10 has been deployed.
For the example that is depicted in
As depicted in
A signed AIC makes the following statements: the virtual TPM 70 containing the AIC was created within a secure enclave 30 by a virtual TPM supervisor 74 using the public-private group identity key infrastructure; the identity represented by the AIK is a specified security version of a virtual TPM 70; and the identity represented by the AIK is private based on an public-private group identity privacy analysis.
Thus, referring to
Referring to
Virtual TPMs 70 existing within a cloud environment may attest for their associated virtual machines using the supervisor key signed AICs. The AICs are rooted back to the group public identity key that is published by the hardware manufacturer.
In accordance with some implementations, the private group identity key 210 is a single key, which the DAA issuer 220 (see
For implementations in which a single private group identity key is provided by the DAA issuer 220, a modification to a secure enclave called the “quoting enclave” may be made to allow the platform key to be used as the supervisor signing key. More specifically, certain aspects of the secure enclaves architecture use relatively complex and time consuming flows, which are not well suited for implementation within micro-coded instructions. These portions may be outsourced to macrocode. In many cases, the outsourced code relies on special access to sensitive processor or platform data. More details regarding the quoting enclave may be found in PCT Publication No. WO 2011/078855 A, mentioned above.
For example, the signing may take too long for a single instruction. Therefore, a quoting enclave may be used to produce signed quotes, by granting the quoting enclave special access to the private group identity key. Enclave authentication allows specification of the additional capabilities granted to specific enclaves, such as access to the key only by the quoting enclave.
Due to the nature of the computation involved with asymmetric keys and a desire to reduce the number of instructions in the enclave leaf, a hardware-based mechanism for producing “reports” based on a symmetric key authentication key may be used; and these symmetric key based reports are converted into asymmetrically signed quotes using software, which itself is protected using an enclave. As the quoting enclave needs to be authorized to have access to the platform attestation key, the quoting enclave itself is a special purpose enclave, known as an authenticated enclave. This approach minimizes the trusted computing base (TCB) extension and does not expose the platform key.
Thus, in accordance with some implementations, the platform key may be maintained by the quoting enclave. In this manner, a quoting enclave application programming interface (API) supports the generation of supervisor signatures. In a general purpose secure enclave attestation, the calling enclave provides a targeted report to the quoting enclave, and the report is generated using a secure enclave instruction called “ENCLU[EREPORT].” The quoting enclave encryptically verifies this report was generated on the same platform that it is running on. The REPORT structure contains a 32-byte user data entry, which is supplied when the originating enclave created the report through the ENCLU[EREPORT] instruction. The enclave report also contains information about the enclave which called the ENCLU[EREPORT] instruction. This API may use the user data field to identify the object that the supervisor enclave desires to sign. The API may also authenticate through the additional fields in the REPORT structure which enclave is requesting the service and selectively approve and deny which signatures are provided. It is noted that the system provides a minimal TCB extension while eliminating the requirement for a complex supervisor key provisioning infrastructure and management, which would be used in a multiple private key system.
Further implementations may include one or more of the following.
In an example implementation, a technique includes on a physical platform, providing a supervisor to manage a lifecycle of a virtual trusted platform module and using the supervisor to sign a certificate for an attestation identity key used by the virtual trusted platform module.
In some implementations, using the supervisor to sign the certificate includes signing the certificate with a private key stored by the supervisor. The private key is paired with a public key, and the public and private keys are issued by a direct anonymous attestation issuer, which is remote from the physical platform.
In some implementations, the issuer is associated with a manufacturer of a platform chipset.
In some implementations, the private and public keys are parts of a privacy identification associated with a manufacturer of the physical platform.
In some implementations, the technique includes using the supervisor to sign certificates for a plurality of attestation identity keys that are used by a plurality of virtual platform modules using the private key.
In some implementations, the technique includes using the supervisor to sign a certificate for an attestation identity key used by another virtual trusted platform module using another private key that is stored by the supervisor.
In some implementations, the technique further includes using the supervisor to request the private key from the issuer.
In further implementations, the private key is associated with the physical platform, and using the supervisor to sign the certificate includes signing the certificate with the private key and another private key assigned to the supervisor.
In some implementations, the technique further includes on the physical platform, providing at least one additional supervisor to manage a lifecycle of at least one additional virtual trusted platform module and using the additional supervisor(s) to sign a certificate for an attestation identity key that is used by the additional virtual trusted platform module(s).
In some implementations, the technique further includes containing the supervisor within a secure enclave of the physical platform.
In some implementations, the technique further includes containing the virtual trusted platform module in the secure enclave.
In some implementations, the virtual trusted platform module is associated with an underlying physical platform module.
In some implementations, an apparatus includes a processor that is configured to perform any of the above-mentioned techniques.
In some implementations, at least one machine readable medium includes a plurality of instructions that in response to being executed on a computing device, cause the computing device to carry out any of the above-described techniques.
In some implementations, an apparatus includes processor-created secure enclaves a virtual trusted platform and a supervisor that are contained in the secure enclaves. The supervisor manages a lifecycle of the virtual trusted platform module and the supervisor, in response to a request by the virtual trusted platform, signs a certificate for an attestation identity key that is used by the virtual trusted platform module.
In some implementations, the supervisor is adapted to sign the certificate.
In some implementations, the supervisor is adapted to store a private key. The private key is paired with a public key, and the public and private keys are issued by a direct anonymous attestation issuer. The supervisor is adapted to sign the certificate using the private key.
In some implementations, the supervisor is adapted to use the certificate to anonymously prove to a verifier that the virtual trusted platform module is associated with a given manufacturer.
In some implementations, the supervisor is adapted to perform one or more of the following: provision the virtual trusted platform module, sign an attestation identification credential for the virtual trusted platform module, regulate a migration of the virtual trusted platform module and regulate retirement of the virtual trusted platform module.
While a limited number of examples have been disclosed herein, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations.