snpguest is a Command Line Interface utility for managing an AMD SEV-SNP enabled guest. This tool allows users to interact with the AMD SEV-SNP guest firmware device enabling various operations such as: attestation, certificate management, derived key fetching, and more.
- Usage
- Extended Attestation Workflow
- Regular Attestation Workflow
- Extended Attestation Flowchart
- Regular Attestation Flowchart
- Building
- Reporting Bugs
Every snpguest (sub)command comes with a --help option for a description on its use.
Usage
snpguest --helpRequests the VEK certificate chain (ARK, ASK/ASVK and VCEK/VLEK) from host memory (requests extended-config). The user needs to specify the certificate encoding to store the certificates in (PEM or DER). Currently, only PEM and DER encodings are supported. All certificates will be in the same encoding. The user also needs to provide the path to the directory where the certificates will be stored. If certificates already exist in the provided directory, they will be overwritten.
Usage
snpguest certificates $ENCODING $CERTS_DIRArguments
-
$ENCODING: Specifies the certificate encoding to store the certificates in (PEM or DER). -
$CERTS_DIR: Specifies the directory to store the certificates in. This is required only when requesting an extended attestation report.
Example
snpguest certificates pem ./certsDisplays files in human readable form.
Usage
snpguest display <SUBCOMMAND>Subcommands
-
reportWhen used for displaying a report, it prints the attestation report contents into the terminal. The user has to provide the path of the stored attestation report to display.
Usage
snpguest display report $ATT_REPORT_PATHArgument
$ATT_REPORT_PATH: Specifies the path of the stored attestation report to display.
Example
snpguest display report attestation-report.bin
-
keyWhen used for displaying the fetched derived key's contents, it prints the derived key in hex format into the terminal. The user has to provide the path of a stored derived key to display.
Usage
snpguest display key $KEY_PATHArgument
$KEY_PATH: Specifies the path of the stored derived key to display.
Example
snpguest display key derived-key.bin
Command to Requests certificates from the KDS.
Usage
snpguest fetch <SUBCOMMAND>Subcommands
-
caRequests the certificate authority chain (ARK & ASK/ASVK) from the KDS. The user needs to specify the certificate encoding to store the certificates in (PEM or DER). Currently, only PEM and DER encodings are supported. Both certificates will be in the same encoding. The user must specify their host processor model. The user also needs to provide the path to the directory where the certificates will be stored. If the certificates already exist in the provided directory, they will be overwritten. The
--endorserargument specifies the type of attestation signing key (defaults to VCEK).Usage
# Fetch CA chain of the user-provided processor model snpguest fetch ca $ENCODING $CERTS_DIR $PROCESSOR_MODEL --endorser $ENDORSER # Fetch CA chain of the processor-model written in the attestation report snpguest fetch ca $ENCODING $CERTS_DIR --report $ATT_REPORT_PATH --endorser $ENDORSER
Arguments
Argument Description Default $ENCODINGSpecifies the certificate encoding to store the certificates in (PEM or DER). required $CERTS_DIRSpecifies the directory to store the certificates in. required $PROCESSOR_MODELSpecifies the host processor model (conflict with $ATT_REPORT_PATH).required -r, --report $ATT_REPORT_PATHSpecifies the attestation report to detect the host processor model (conflict with $PROCESSOR_MODEL)— -e, --endorser $ENDORSERSpecifies the endorser type, possible values: "vcek", "vlek". "vcek" Example
snpguest fetch ca der ./certs-kds milan -e vlek
snpguest fetch ca pem ./certs-kds -r attestation-report.bin -e vcek
-
vcekRequests the VCEK certificate from the KDS. The user needs to specify the certificate encoding to store the certificate in (PEM or DER). Currently, only PEM and DER encodings are supported. The user must specify their host processor model. The user also needs to provide the path to the directory where the VCEK will be stored and the path to a stored attestation report that will be used to request the VCEK. If the certificate already exists in the provided directory, it will be overwritten.
Usage
snpguest fetch vcek $ENCODING $CERTS_DIR $ATT_REPORT_PATH --processor-model $PROCESSOR_MODEL
Arguments
Argument Description Default $ENCODINGSpecifies the certificate encoding to store the certificates in (PEM or DER). required $CERTS_DIRSpecifies the directory to store the certificates in. required $ATT_REPORT_PATHSpecifies the path of the stored attestation report. required -p, --processor-model $PROCESSOR_MODELSpecifies the host processor model. — Example
snpguest fetch vcek pem ./certs-kds attestation-report.bin
-
crlRequests the Certificate Revocation List (CRL) from the KDS. It takes the same set of arguments as
snpguest fetch ca. The user needs to specify the encoding to store the CRL in (PEM or DER). Currently, only PEM and DER encodings are supported. The user must specify their host processor model. The user also needs to provide the path to the directory where the CRL will be stored. If the CRL already exists in the provided directory, it will be overwritten. The--endorserargument specifies the type of attestation signing key (defaults to VCEK).Usage
# Fetch CRL of the user-provided processor model snpguest fetch crl $ENCODING $CERTS_DIR $PROCESSOR_MODEL --endorser $ENDORSER # Fetch CRL of the processor-model written in the attestation report snpguest fetch crl $ENCODING $CERTS_DIR --report $ATT_REPORT_PATH --endorser $ENDORSER
Arguments
Argument Description Default $ENCODINGSpecifies the encoding to store the CRL in (PEM or DER). required $CERTS_DIRSpecifies the directory to store the CRL in. required $PROCESSOR_MODELSpecifies the host processor model (conflict with --report).required -r, --report $ATT_REPORT_PATHSpecifies the attestation report to detect the host processor model (conflict with $PROCESSOR_MODEL)— -e, --endorser $ENDORSERSpecifies the endorser type, possible values: "vcek", "vlek". "vcek" Example
snpguest fetch crl der ./certs-kds milan -e vlek
snpguest fetch crl pem ./certs-kds -r attestation-report.bin -e vcek
Creates the derived key based on input parameters and stores it. $KEY_PATH is the path to store the derived key. $ROOT_KEY_SELECT is the root key from which to derive the key (either "vcek" or "vmrk"). The --guest_field_select option specifies which Guest Field Select bits to enable as a 64-bit integer. Only the least-significant 6 bits (Message Version 1) or 7 bits (Message Version 2) are currently defined. Each of the bits from right to left correspond to Guest Policy, Image ID, Family ID, Measurement, SVN and TCB Version, Launch Mitigation Vector, respectively. For each bit, 0 denotes off, and 1 denotes on. The --guest_svn option specifies the guest SVN to mix into the key, the --tcb_version option specifies the TCB version to mix into the derived key, and the --launch_mit_vector option specifies the launch mitigation vector value to mix into the derived key. The --vmpl option specifies the VMPL level the Guest is running on and defaults to 1.
Usage
snpguest key $KEY_PATH $ROOT_KEY_SELECT [-v, --vmpl] [-g, --guest_field_select] [-s, --guest_svn] [-t, --tcb_version]Arguments
| Argument | Description | Default |
|---|---|---|
$KEY_PATH |
The path to store the derived key. | required |
$ROOT_KEY_SELECT |
is the root key from which to derive the key (either "vcek" or "vmrk"). | required |
-v, --vmpl $VMPL |
option specifies the VMPL level the Guest is running on. | 1 |
-g, --guest_field_select $GFS |
option specifies which Guest Field Select bits to enable as a 64-bit integer (decimal, prefixed hex or prefixed bin). | 0 |
-s, --guest_svn $GSVN |
option specifies the guest SVN to mix into the key (decimal, prefixed hex or prefixed bin). | 0 |
-t, --tcb_version $TCBV |
option specifies the TCB version to mix into the derived key (decimal, prefixed hex or prefixed bin). | 0 |
-l, --launch_mit_vector $LMV |
option specifies the launch mitigation vector value to mix into the derived key (decimal, prefixed hex or prefixed bin). Only available for MSG_KEY_REQ message version ≥ 2. |
— |
Guest Field Select
| Bit | Field | Note |
|---|---|---|
| 63:7 | (Reserved) | Currently not supported. |
| 6 (MSB) | Launch MIT Vector | Set to 0 if not specified; supported for MSG_KEY_REQ message version ≥ 2. |
| 5 | TCB Version | |
| 4 | SVN | |
| 3 | Measurement | |
| 2 | Family ID | |
| 1 | Image ID | |
| 0 (LSB) | Guest Policy |
For example, all of
--guest_field_select 49--guest_field_select 0x31--guest_field_select 0b110001
denote the following specification:
Guest Policy:On (1),
Image ID:Off (0),
Family ID: Off (0),
Measurement: Off (0),
SVN:On (1),
TCB Version:On (1),
Launch MIT Vector: Off (none).
Example
# Creating and storing a derived key
snpguest key derived-key.bin vcek --guest_field_select 0b110001 --guest_svn 2 --tcb_version 1 --vmpl 3Requests an attestation report from the host and writes it to a file with the provided request data and VMPL. The attestation report is written in binary format to the specified report path. The user can pass 64 bytes of data in any file format into $REQUEST_FILE to request the attestation report. This data will be bound to the REPORT_DATA field of the attestation report. The --random flag can be used to generate and use random data for the request, which will be written into $REQUEST_FILE. On a Confidential VM with the OpenHCL paravisor, use --openhcl to request a fresh attestation report through the vTPM. The 64 bytes read from $REQUEST_FILE, or generated with --random, are supplied to OpenHCL as the report request data. When --openhcl is used, --vmpl is ignored and the paravisor requests the report at VMPL 0. VMPL otherwise defaults to 1.
Usage
snpguest report $ATT_REPORT_PATH $REQUEST_FILE [-v, --vmpl] [-r, --random] [--openhcl]Arguments
| Argument | Description | Default |
|---|---|---|
$ATT_REPORT_PATH |
Specifies the path where the attestation report would be stored. | required |
$REQUEST_FILE |
Specifies the path to the 64-byte request file. Its contents are used as the report request data. With --random, 64 random bytes are generated, written to this file, and used instead. |
required |
-v, --vmpl $VMPL |
Specifies the VMPL level the Guest is running on. Ignored with --openhcl, which requests the report at VMPL 0. |
1 |
-r, --random |
Generate 64 random bytes of data for the report request and write them to $REQUEST_FILE. |
false |
--openhcl |
Request a fresh attestation report through the OpenHCL paravisor (only available on supported Confidential VMs with a binary built with the hyperv feature). |
false |
Example
# Requesting Attestation Report with user-generated data
snpguest report attestation-report.bin request-file.bin
# Requesting Attestation Report using random data
snpguest report attestation-report.bin random-request-file.bin --random
# Requesting a fresh Attestation Report through OpenHCL with user-generated data
snpguest report attestation-report.bin request-file.bin --openhclVerifies certificates and the attestation report.
Usage
snpguest verify <SUBCOMMAND>Subcommands
-
certsVerifies that the provided certificate chain has been properly signed by each certificate. The user needs to provide a directory where all three certificates (ARK, ASK/ASVK and VCEK/VLEK) are stored. An error will be raised if any of the certificates fail verification.
Usage
snpguest verify certs $CERTS_DIRArgument
$CERTS_DIR: Specifies the directory where the certificates are stored in.
Example
snpguest verify certs ./certs
-
attestationVerifies the contents of the Attestation Report using the VCEK/VLEK certificate. The user needs to provide the path to the directory containing the VCEK/VLEK certificate and the path to a stored attestation report to be verified. An error will be raised if the attestation verification fails at any point. The user can use the
-t, --tcbflag to only validate the TCB contents of the report and the-s, --signatureflag to only validate the report's signature.Usage
snpguest verify attestation $CERTS_DIR $ATT_REPORT_PATH [-t, --tcb] [-s, --signature] [-m, --measurement] [-d, --host-data] [-r, --report-data]
Arguments
-
$CERTS_DIR: Specifies the directory where the certificates are stored in. -
$ATT_REPORT_PATH: Specifies the path of the stored attestation report.
Options
-t, --tcb: Verify the Reported TCB section of the report only.-s, --signature: Verify the signature of the report only.-m, --measurement: Verify the measurement from the attestation report.-d, --host-data: Verify the host-data from the attestation report.-r, --report-data: Verify the report-data from the attestation report.
Example
# Verify Attestation snpguest verify attestation ./certs attestation-report.bin # Verify Attestation Reported TCB only snpguest verify attestation ./certs attestation-report.bin --tcb # Verify Attestation Signature only snpguest verify attestation ./certs attestation-report.bin --signature # Verify Attestation Measurement only snpguest verify attestation --measurement 0xf28aac58964258d8ae0b2e88a706fc7afd0bb524f6a291ac3eedeccb73f89d7cfcf2e4fb6045e7d5201e41d1726afa02 /home/amd/certs /home/amd/report.bin # Verify Attestation host-data only snpguest verify attestation --host-data 0x7e4a3f9c1b82a056d39f0d44e5c8a7b1f02394de6b58ac0d7e3c11af0042bd59 /home/amd/certs /home/amd/report.bin # Verify Attestation report-data only snpguest verify attestation --report-data 0x5482c1ffe29145d47cf678f7681e3b64a89909d6cf8ec0104cfacb0b0418f005f564ad14f5c1381c99b74903a780ea340e887c9b445e9c760bf0b74115b26d45 /home/amd/certs /home/amd/report.bin
-
- -q, --quiet: Suppress console output.
Usage
snpguest -q <SUBCOMMAND>Step 1. Request the attestation report by providing the two mandatory parameters - $ATT_REPORT_PATH which is the path pointing to where the user wishes to store the attestation report and $REQUEST_FILE which contains the 64 bytes of request data. The optional parameter [-v, --vmpl] specifies the VMPL level for the attestation report and is set to 1 by default. The flag [-r, --random] generates random request data and writes it to $REQUEST_FILE. On a Confidential VM with the OpenHCL paravisor, the --openhcl flag requests a fresh report through OpenHCL using the data from $REQUEST_FILE, or the generated data when combined with --random. --openhcl requires the hyperv feature and ignores --vmpl because the paravisor requests the report at VMPL 0.
snpguest report $ATT_REPORT_PATH $REQUEST_FILE [-v, --vmpl] [-r, --random] [--openhcl]Step 2. Request certificates from the extended memory by providing the two mandatory parameters - $ENCODING which specifies whether to use PEM or DER encoding to store the certificates and $CERTS_DIR which specifies the path in the user's directory where the certificates will be saved.
snpguest certificates $ENCODING $CERTS_DIRIn some environments, only the VCEK/VLEK certificate can be obtained. In this case, you must follow the procedure described in Regular Attestation Workflow to obtain an AMD CA certificates.
Step 3. Verify the certificates obtained from the extended memory by providing $CERTS_DIR which specifies the path in the user's directory where the certificates were saved from Step 2.
snpguest verify certs $CERTS_DIRStep 4. Verify the attestation by providing the two mandatory parameters - $CERTS_DIR which specifies the path in the user's directory where the certificates were saved from Step 2 and $ATT_REPORT_PATH which is the path pointing to the stored attestation report which the user wishes to verify. The optional parameters [-t, --tcb] is used to verify just the Reported TCB contents of the attestaion report and [-s, --signature] is used to verify just the signature of the attestaion report.
snpguest verify attestation $CERTS_DIR $ATT_REPORT_PATH [-t, --tcb] [-s, --signature]Step 1. Request the attestation report by providing the two mandatory parameters - $ATT_REPORT_PATH which is the path pointing to where the user wishes to store the attestation report and $REQUEST_FILE which contains the 64 bytes of request data. The optional parameter [-v, --vmpl] specifies the VMPL level for the attestation report and is set to 1 by default. The flag [-r, --random] generates random request data and writes it to $REQUEST_FILE. On a Confidential VM with the OpenHCL paravisor, the --openhcl flag requests a fresh report through OpenHCL using the data from $REQUEST_FILE, or the generated data when combined with --random. --openhcl requires the hyperv feature and ignores --vmpl because the paravisor requests the report at VMPL 0.
snpguest report $ATT_REPORT_PATH $REQUEST_FILE [-v, --vmpl] [-r, --random] [--openhcl]Step 2. Request AMD Root Key (ARK) and AMD SEV Key (ASK) (or AMD SEV-VLEK Key (ASVK) for VLEK) from the AMD Key Distribution Service (KDS) by providing the three mandatory parameters - $ENCODING which specifies whether to use PEM or DER encoding to store the certificates, $CERTS_DIR which specifies the path in the user's directory where the certificates will be saved, and $PROCESSOR_MODEL - which specifies the AMD Processor model for which the certificates are to be fetched. The optional -e, --endorser argument specifies the type of attestation signing key (defaults to VCEK).
snpguest fetch ca $ENCODING $CERTS_DIR $PROCESSOR_MODEL [-e, --endorser] $ENDORSERStep 3. Request the Versioned Chip Endorsement Key (VCEK) from the AMD Key Distribution Service (KDS) by providing the three mandatory parameters - $ENCODING which specifies whether to use PEM or DER encoding to store the certificates, $CERTS_DIR which specifies the path in the user's directory where the certificates will be saved, and $ATT_REPORT_PATH which is the path pointing to the stored attestation report for detecting Chip ID and Reported TCB Version. The optional [-p, --processor-model] argument specifies the AMD Processor model for which the certificates are to be fetched.
snpguest fetch vcek $ENCODING $CERTS_DIR $ATT_REPORT_PATH [-p, --processor-model] $PROCESSOR_MODELStep 4. Verify the certificates obtained by providing $CERTS_DIR which specifies the path in the user's directory where the certificates were saved from Step 2.
snpguest verify certs $CERTS_DIRStep 5. Verify the attestation by providing the two mandatory parameters - $CERTS_DIR which specifies the path in the user's directory where the certificates were saved from Step 2 and $ATT_REPORT_PATH which is the path pointing to the stored attestation report which the user wishes to verify. The optional parameters [-t, --tcb] is used to verify just the Reported TCB contents of the attestaion report and [-s, --signature] is used to verify just the signature of the attestaion report.
snpguest verify attestation $CERTS_DIR $ATT_REPORT_PATH [-t, --tcb] [-s, --signature]
Some packages may need to be installed on the host system in order to build snpguest.
#Rust Installation
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source "$HOME/.cargo/env"
#Building snpguest after cloning
cargo build -rsudo apt install build-essentialsudo dnf groupinstall "Development Tools" "Development Libraries"sudo zypper in -t pattern "devel_basis"On Azure CVMs with AMD SEV-SNP, the native /dev/sev-guest interface is hidden from the guest OS. Build snpguest with the hyperv feature and use the --openhcl flag to request a fresh attestation report through the OpenHCL paravisor. The command supplies the 64 bytes from $REQUEST_FILE (or the bytes generated by --random) to OpenHCL through the vTPM, then reads the resulting report from the vTPM NV index.
git clone https://github.com/virtee/snpguest
cd ./snpguest
cargo build -r --features hypervPlease report all bugs to the Github snpguest repository.