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title description services author ms.service ms.topic ms.date ms.author
Examples of an Azure Attestation policy
Examples of Azure Attestation policy.
attestation
msmbaldwin
attestation
overview
08/31/2020
mbaldwin

Examples of an attestation policy

Attestation policy is used to process the attestation evidence and determine whether Azure Attestation will issue an attestation token. Attestation token generation can be controlled with custom policies. Below are some examples of an attestation policy.

Sample custom policy for an SGX enclave

version= 1.0;
authorizationrules
{
       [ type=="x-ms-sgx-is-debuggable", value==false ]
        && [ type=="x-ms-sgx-product-id", value==<product-id> ]
        && [ type=="x-ms-sgx-svn", value>= 0 ]
        && [ type=="x-ms-sgx-mrsigner", value=="<mrsigner>"]
    => permit();
};
issuancerules {
c:[type=="x-ms-sgx-mrsigner"] => issue(type="<custom-name>", value=c.value);
};

For more information on the incoming claims generated by Azure Attestation, see claim sets. Incoming claims can be used by policy authors to define authorization rules in a custom policy.

Issuance rules section isn't mandatory. This section can be used by the users to have additional outgoing claims generated in the attestation token with custom names. For more information on the outgoing claims generated by the service in attestation token, see claim sets.

Default policy for an SGX enclave

version= 1.0;
authorizationrules {
	=> permit();
};
issuancerules {
	c:[type=="x-ms-sgx-is-debuggable"] => issue(type="is-debuggable", value=c.value);
	c:[type=="x-ms-sgx-mrsigner"] => issue(type="sgx-mrsigner", value=c.value);
	c:[type=="x-ms-sgx-mrenclave"] => issue(type="sgx-mrenclave", value=c.value);
	c:[type=="x-ms-sgx-product-id"] => issue(type="product-id", value=c.value);
	c:[type=="x-ms-sgx-svn"] => issue(type="svn", value=c.value);
	c:[type=="x-ms-attestation-type"] => issue(type="tee", value=c.value);
};

Claims used in default policy are considered deprecated but are fully supported and will continue to be included in the future. It's recommended to use the non-deprecated claim names. For more information on the recommended claim names, see claim sets.

Sample custom policy to support multiple SGX enclaves

version= 1.0;
authorizationrules 
{
	[ type=="x-ms-sgx-is-debuggable", value==true ]&&
	[ type=="x-ms-sgx-mrsigner", value=="mrsigner1"] => permit(); 
	[ type=="x-ms-sgx-is-debuggable", value==true ]&& 
	[ type=="x-ms-sgx-mrsigner", value=="mrsigner2"] => permit(); 
};

Unsigned Policy for an SGX enclave with PolicyFormat=JWT

eyJhbGciOiJub25lIn0.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.

Signed Policy for an SGX enclave with PolicyFormat=JWT

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.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.c0l-xqGDFQ8_kCiQ0_vvmDQYG_u544CYmoiucPNxd9MU8ZXT69UD59UgSuya2yl241NoVXA_0LaMEB2re0JnTbPD_dliJn96HnIOqnxXxRh7rKbu65ECUOMWPXbyKQMZ0I3Wjhgt_XyyhfEiQGfJfGzA95-wm6yWqrmW7dMI7JkczG9ideztnr0bsw5NRsIWBXOjVy7Bg66qooTnODS_OqeQ4iaNsN-xjMElHABUxXhpBt2htbhemDU1X41o8clQgG84aEHCgkE07pR-7IL_Fn2gWuPVC66yxAp00W1ib2L-96q78D9J52HPdeDCSFio2RL7r5lOtz8YkQnjacb6xA

Sample policy for TPM using Policy version 1.0

version=1.0;

authorizationrules { 
    => permit();
};

issuancerules
{
[type=="aikValidated", value==true]&& 
[type=="secureBootEnabled", value==true] &&
[type=="bootDebuggingDisabled", value==true] && 
[type=="vbsEnabled", value==true] && 
[type=="notWinPE", value==true] && 
[type=="notSafeMode", value==true] => issue(type="PlatformAttested", value=true);
};

A simple TPM attestation policy that can be used to verify minimal aspects of the boot.

Sample policy for TPM using Policy version 1.2

version=1.2;

configurationrules{
	=> issueproperty(type="required_pcr_mask", value=131070);
	=> issueproperty(type="require_valid_aik_cert", value=false);
};

authorizationrules { 
c:[type == "tpmVersion", issuer=="AttestationService", value==2] => permit();
};

issuancerules{

c:[type == "aikValidated", issuer=="AttestationService"] =>issue(type="aikValidated", value=c.value);

// SecureBoot enabled 
c:[type == "events", issuer=="AttestationService"] => add(type = "efiConfigVariables", value = JmesPath(c.value, "Events[?EventTypeString == 'EV_EFI_VARIABLE_DRIVER_CONFIG' && ProcessedData.VariableGuid == '8BE4DF61-93CA-11D2-AA0D-00E098032B8C']"));
c:[type == "efiConfigVariables", issuer=="AttestationPolicy"]=> issue(type = "SecureBootEnabled", value = JsonToClaimValue(JmesPath(c.value, "[?ProcessedData.UnicodeName == 'SecureBoot'] | length(@) == `1` && @[0].ProcessedData.VariableData == 'AQ'")));
![type=="SecureBootEnabled", issuer=="AttestationPolicy"] => issue(type="SecureBootEnabled", value=false);

// Retrieve bool properties Code integrity
c:[type=="events", issuer=="AttestationService"] => add(type="boolProperties", value=JmesPath(c.value, "Events[? EventTypeString == 'EV_EVENT_TAG' && (PcrIndex == `12` || PcrIndex == `13` || PcrIndex == `19` || PcrIndex == `20`)].ProcessedData.EVENT_TRUSTBOUNDARY"));
c:[type=="boolProperties", issuer=="AttestationPolicy"] => add(type="codeIntegrityEnabledSet", value=JsonToClaimValue(JmesPath(c.value, "[*].EVENT_CODEINTEGRITY")));
c:[type=="codeIntegrityEnabledSet", issuer=="AttestationPolicy"] => issue(type="CodeIntegrityEnabled", value=ContainsOnlyValue(c.value, true));
![type=="CodeIntegrityEnabled", issuer=="AttestationPolicy"] => issue(type="CodeIntegrityEnabled", value=false);

// Bitlocker Boot Status, The first non zero measurement or zero.
c:[type=="events", issuer=="AttestationService"] => add(type="srtmDrtmEventPcr", value=JmesPath(c.value, "Events[? EventTypeString == 'EV_EVENT_TAG' && (PcrIndex == `12` || PcrIndex == `19`)].ProcessedData.EVENT_TRUSTBOUNDARY"));
c:[type=="srtmDrtmEventPcr", issuer=="AttestationPolicy"] => add(type="BitlockerStatus", value=JsonToClaimValue(JmesPath(c.value, "[*].EVENT_BITLOCKER_UNLOCK | @[? Value != `0`].Value | @[0]")));
[type=="BitlockerStatus", issuer=="AttestationPolicy"] => issue(type="BitlockerStatus", value=true);
![type=="BitlockerStatus", issuer=="AttestationPolicy"] => issue(type="BitlockerStatus", value=false);

// Elam Driver (windows defender) Loaded
c:[type=="boolProperties", issuer=="AttestationPolicy"] => add(type="elamDriverLoaded", value=JsonToClaimValue(JmesPath(c.value, "[*].EVENT_LOADEDMODULE_AGGREGATION[] | [? EVENT_IMAGEVALIDATED == `true` && (equals_ignore_case(EVENT_FILEPATH, '\\windows\\system32\\drivers\\wdboot.sys') || equals_ignore_case(EVENT_FILEPATH, '\\windows\\system32\\drivers\\wd\\wdboot.sys'))] | @ != `null`")));
[type=="elamDriverLoaded", issuer=="AttestationPolicy"] => issue(type="ELAMDriverLoaded", value=true);
![type=="elamDriverLoaded", issuer=="AttestationPolicy"] => issue(type="ELAMDriverLoaded", value=false);

};

The policy uses the TPM version to restrict attestation calls. The issuancerules looks at various properties measured during boot.

Next steps