diff --git a/crates/attestation/src/lib.rs b/crates/attestation/src/lib.rs index fa92797..7ecfc34 100644 --- a/crates/attestation/src/lib.rs +++ b/crates/attestation/src/lib.rs @@ -11,6 +11,7 @@ use std::{ fmt::{self, Display, Formatter}, io::Read, net::IpAddr, + sync::{Arc, RwLock, RwLockReadGuard, RwLockWriteGuard}, time::{Duration, SystemTime, UNIX_EPOCH}, }; @@ -22,7 +23,11 @@ use pccs::{Pccs, PccsError}; use serde::{Deserialize, Serialize}; use thiserror::Error; -use crate::{dcap::DcapVerificationError, gcp::GcpFirmwareCache, measurements::MeasurementPolicy}; +use crate::{ + dcap::DcapVerificationError, + gcp::GcpFirmwareCache, + measurements::{MeasurementFormatError, MeasurementPolicy}, +}; #[cfg(test)] static TEST_CRYPTO_PROVIDER: OnceLock<()> = OnceLock::new(); @@ -325,8 +330,9 @@ impl AttestationGenerator { /// Allows remote attestations to be verified #[derive(Clone, Debug)] pub struct AttestationVerifier { - /// The measurement policy with accepted values and attestation types - measurement_policy: MeasurementPolicy, + /// The measurement policy with accepted values and attestation types, + /// shared between clones + measurement_policy: Arc>, /// Whether to write quotes to files on disk dump_dcap_quotes: bool, #[cfg(feature = "azure")] @@ -338,12 +344,30 @@ pub struct AttestationVerifier { internal_pccs: Option, /// Cached GCP firmware blobs indexed by MRTD known_gcp_firmware: gcp::GcpFirmwareCache, + /// Dynamic measurement policy to re-fetch from file or URL + dynamic_measurement_policy: Option, +} + +/// Measurement policy together with a generation number used to track +/// changes +#[derive(Clone, Debug)] +struct MeasurementPolicyState { + policy: MeasurementPolicy, + generation: u64, +} + +impl MeasurementPolicyState { + fn new(policy: MeasurementPolicy) -> Self { + Self { policy, generation: 0 } + } } /// Options used to construct an [AttestationVerifier] pub struct AttestationVerifierBuilder { /// The measurement policy with accepted values and attestation types measurement_policy: MeasurementPolicy, + /// A dynamic measurement policy file or URL + dynamic_measurement_policy: Option, /// A PCCS service to use - defaults to Intel PCS pccs_url: Option, dump_dcap_quotes: bool, @@ -396,6 +420,17 @@ impl AttestationVerifierBuilder { self.pccs_url = Some(pccs_url); self } + + /// Re-fetch the measurement policy from this file or URL after a + /// measurement mismatch. + /// + /// Both asynchronous and synchronous verification perform one retry + /// with the refreshed policy. Synchronous URL refreshes block for + /// up to ten seconds. + pub fn with_dynamic_measurements_file_or_url(mut self, file_or_url: String) -> Self { + self.dynamic_measurement_policy = Some(file_or_url); + self + } } impl AttestationVerifier { @@ -409,12 +444,15 @@ impl AttestationVerifier { }); Self { - measurement_policy: builder.measurement_policy, + measurement_policy: Arc::new(RwLock::new(MeasurementPolicyState::new( + builder.measurement_policy, + ))), dump_dcap_quotes: builder.dump_dcap_quotes, #[cfg(feature = "azure")] override_azure_outdated_tcb: builder.override_azure_outdated_tcb, internal_pccs, known_gcp_firmware: GcpFirmwareCache::new(), + dynamic_measurement_policy: builder.dynamic_measurement_policy, } } @@ -426,6 +464,7 @@ impl AttestationVerifier { #[cfg(feature = "azure")] override_azure_outdated_tcb: false, internal_pccs_prewarm: Some(true), + dynamic_measurement_policy: None, } } @@ -433,12 +472,15 @@ impl AttestationVerifier { /// and will reject if one is given pub fn expect_none() -> Self { Self { - measurement_policy: MeasurementPolicy::expect_none(), + measurement_policy: Arc::new(RwLock::new(MeasurementPolicyState::new( + MeasurementPolicy::expect_none(), + ))), dump_dcap_quotes: false, #[cfg(feature = "azure")] override_azure_outdated_tcb: false, internal_pccs: None, known_gcp_firmware: gcp::GcpFirmwareCache::new(), + dynamic_measurement_policy: None, } } @@ -446,12 +488,15 @@ impl AttestationVerifier { #[cfg(any(test, feature = "mock"))] pub fn mock() -> Self { Self { - measurement_policy: MeasurementPolicy::mock(), + measurement_policy: Arc::new(RwLock::new(MeasurementPolicyState::new( + MeasurementPolicy::mock(), + ))), dump_dcap_quotes: false, #[cfg(feature = "azure")] override_azure_outdated_tcb: false, internal_pccs: None, known_gcp_firmware: gcp::GcpFirmwareCache::new(), + dynamic_measurement_policy: None, } } @@ -459,12 +504,15 @@ impl AttestationVerifier { #[cfg(any(test, feature = "mock"))] pub fn mock_with_pccs(pccs_url: String) -> Self { Self { - measurement_policy: MeasurementPolicy::mock(), + measurement_policy: Arc::new(RwLock::new(MeasurementPolicyState::new( + MeasurementPolicy::mock(), + ))), dump_dcap_quotes: false, #[cfg(feature = "azure")] override_azure_outdated_tcb: false, internal_pccs: Some(Pccs::new(Some(pccs_url))), known_gcp_firmware: gcp::GcpFirmwareCache::new(), + dynamic_measurement_policy: None, } } @@ -551,11 +599,31 @@ impl AttestationVerifier { .attestation_evidence .as_ref() .map(|evidence| evidence.platform.clone()); - self.measurement_policy.check_measurement_with_gcp_cache( + + let policy_state = self.measurement_policy_read().clone(); + let policy_check = policy_state.policy.check_measurement_with_gcp_cache( &measurements, platform_metadata.as_ref(), Some(&self.known_gcp_firmware), - )?; + ); + + if let Err(err) = policy_check { + // If this fails, and we have dynamic measurement policy, re-retrieve our + // measurement policy, then check the policy a second time + if let Some(file_or_url) = &self.dynamic_measurement_policy { + let new_measurement_policy = + MeasurementPolicy::from_file_or_url(file_or_url.to_string()).await?; + let measurement_policy = + self.set_measurement_policy(new_measurement_policy, policy_state.generation); + measurement_policy.check_measurement_with_gcp_cache( + &measurements, + platform_metadata.as_ref(), + Some(&self.known_gcp_firmware), + )?; + } else { + return Err(err); + } + } tracing::debug!("Verification successful"); Ok(Some(measurements)) @@ -628,11 +696,28 @@ impl AttestationVerifier { .attestation_evidence .as_ref() .map(|evidence| evidence.platform.clone()); - self.measurement_policy.check_measurement_with_gcp_cache( + let policy_state = self.measurement_policy_read().clone(); + let policy_check = policy_state.policy.check_measurement_with_gcp_cache( &measurements, platform_metadata.as_ref(), Some(&self.known_gcp_firmware), - )?; + ); + + if let Err(err) = policy_check { + if let Some(file_or_url) = &self.dynamic_measurement_policy { + let new_measurement_policy = + MeasurementPolicy::from_file_or_url_sync(file_or_url.to_string())?; + let measurement_policy = + self.set_measurement_policy(new_measurement_policy, policy_state.generation); + measurement_policy.check_measurement_with_gcp_cache( + &measurements, + platform_metadata.as_ref(), + Some(&self.known_gcp_firmware), + )?; + } else { + return Err(err); + } + } tracing::debug!("Verification successful"); Ok(Some(measurements)) @@ -640,12 +725,42 @@ impl AttestationVerifier { /// Whether we allow no remote attestation pub fn has_remote_attestation(&self) -> bool { - self.measurement_policy.has_remote_attestation() + self.measurement_policy_read().policy.has_remote_attestation() } - /// Returns the measurement policy used - pub fn measurement_policy(&self) -> &MeasurementPolicy { - &self.measurement_policy + /// Returns a snapshot of the measurement policy currently in use. + pub fn measurement_policy(&self) -> MeasurementPolicy { + self.measurement_policy_read().policy.clone() + } + + /// Whether this verifier automatically refreshes its measurement policy + /// after a mismatch. + pub fn has_dynamic_measurement_policy(&self) -> bool { + self.dynamic_measurement_policy.is_some() + } + + /// Replaces the measurement policy used by this verifier and all of its + /// clones if it has not changed since `expected_generation` was + /// observed. + pub(crate) fn set_measurement_policy( + &self, + measurement_policy: MeasurementPolicy, + expected_generation: u64, + ) -> MeasurementPolicy { + let mut state = self.measurement_policy_write(); + if state.generation == expected_generation { + state.policy = measurement_policy; + state.generation = state.generation.wrapping_add(1); + } + state.policy.clone() + } + + fn measurement_policy_read(&self) -> RwLockReadGuard<'_, MeasurementPolicyState> { + self.measurement_policy.read().unwrap_or_else(|poisoned| poisoned.into_inner()) + } + + fn measurement_policy_write(&self) -> RwLockWriteGuard<'_, MeasurementPolicyState> { + self.measurement_policy.write().unwrap_or_else(|poisoned| poisoned.into_inner()) } } @@ -773,6 +888,8 @@ pub enum AttestationError { AttestationTypeNotAccepted, #[error("Measurements not accepted")] MeasurementsNotAccepted, + #[error("Failed to refresh measurement policy: {0}")] + MeasurementPolicyRefresh(#[from] MeasurementFormatError), #[cfg(feature = "azure")] #[error("MAA: {0}")] Maa(#[from] azure::MaaError), @@ -835,4 +952,93 @@ mod tests { assert!(result.is_ok(), "expected sync mock verification to succeed: {result:?}"); } + + #[test] + fn measurement_policy_can_be_updated_between_verification_attempts() { + let verifier = + AttestationVerifier::builder(MeasurementPolicy::tdx()).with_no_internal_pccs().build(); + let verifier_clone = verifier.clone(); + let message = AttestationExchangeMessage::without_attestation(); + let input_data = [0; 64]; + + assert!(matches!( + verifier.verify_attestation_sync(message.clone(), input_data), + Err(AttestationError::AttestationTypeNotAccepted) + )); + + let generation = verifier_clone.measurement_policy_read().generation; + verifier_clone.set_measurement_policy(MeasurementPolicy::expect_none(), generation); + + assert!(matches!(verifier.verify_attestation_sync(message, input_data), Ok(None))); + } + + #[test] + fn stale_measurement_policy_refresh_does_not_overwrite_newer_policy() { + let verifier = AttestationVerifier::expect_none(); + let stale_generation = verifier.measurement_policy_read().generation; + + verifier.set_measurement_policy(MeasurementPolicy::tdx(), stale_generation); + let installed_policy = + verifier.set_measurement_policy(MeasurementPolicy::expect_none(), stale_generation); + + assert!(installed_policy.has_remote_attestation()); + assert!(verifier.has_remote_attestation()); + } + + #[tokio::test] + async fn dynamic_measurement_policy_refetches_on_mismatch() { + let temp_dir = tempfile::tempdir().unwrap(); + let policy_path = temp_dir.path().join("measurements.json"); + tokio::fs::write(&policy_path, br#"[{"attestation_type":"none"}]"#).await.unwrap(); + + let initial_policy = MeasurementPolicy::from_file(policy_path.clone()).await.unwrap(); + let verifier = AttestationVerifier::builder(initial_policy) + .with_no_internal_pccs() + .with_dynamic_measurements_file_or_url(policy_path.to_string_lossy().into_owned()) + .build(); + + let input_data = [7u8; 64]; + let quote = dcap::create_dcap_attestation(input_data).unwrap(); + let attestation = AttestationEvidence { + quote, + platform: mock_platform_metadata(AttestationType::DcapTdx).unwrap(), + }; + let measurements = measurements::mock_dcap_measurements(); + + assert!(verifier.measurement_policy().check_measurement(&measurements, None).is_err()); + + tokio::fs::write(&policy_path, br#"[{"attestation_type":"dcap-tdx"}]"#).await.unwrap(); + + verifier.verify_attestation(attestation.into(), input_data).await.unwrap(); + + assert!(verifier.measurement_policy().check_measurement(&measurements, None).is_ok()); + } + + #[tokio::test] + async fn sync_verification_refetches_dynamic_measurement_policy_on_mismatch() { + let temp_dir = tempfile::tempdir().unwrap(); + let policy_path = temp_dir.path().join("measurements.json"); + std::fs::write(&policy_path, br#"[{"attestation_type":"none"}]"#).unwrap(); + + let policy_source = policy_path.to_string_lossy().into_owned(); + let initial_policy = + MeasurementPolicy::from_file_or_url_sync(policy_source.clone()).unwrap(); + let mock_pcs_server = spawn_mock_pcs_server(MockPcsConfig::default()).await.unwrap(); + let verifier = AttestationVerifier::builder(initial_policy) + .pccs_url(mock_pcs_server.base_url.clone()) + .with_dynamic_measurements_file_or_url(policy_source) + .build(); + verifier.ready().await.unwrap(); + + let input_data = [7u8; 64]; + let quote = dcap::create_dcap_attestation(input_data).unwrap(); + let attestation = AttestationEvidence { + quote, + platform: mock_platform_metadata(AttestationType::DcapTdx).unwrap(), + }; + + std::fs::write(&policy_path, br#"[{"attestation_type":"dcap-tdx"}]"#).unwrap(); + + verifier.verify_attestation_sync(attestation.into(), input_data).unwrap(); + } } diff --git a/crates/attestation/src/measurements.rs b/crates/attestation/src/measurements.rs index 878ce87..0f640e2 100644 --- a/crates/attestation/src/measurements.rs +++ b/crates/attestation/src/measurements.rs @@ -1,6 +1,14 @@ //! Measurements and policy for enforcing them when validating a remote //! attestation -use std::{collections::HashMap, fmt, fmt::Formatter, net::IpAddr, path::PathBuf}; +use std::{ + collections::HashMap, + fmt, + fmt::Formatter, + io::Read, + net::IpAddr, + path::PathBuf, + time::Duration, +}; use attest_measure::dcap::expected_dcap_registers; use attest_types::{ @@ -502,6 +510,33 @@ impl MeasurementPolicy { } } + /// Synchronously parse a measurement policy from either a URL or a file + /// path. + pub fn from_file_or_url_sync(file_or_url: String) -> Result { + #[cfg(test)] + crate::install_test_crypto_provider(); + + let normalized_source = file_or_url.to_lowercase(); + let normalized_source = normalized_source.trim_ascii(); + let is_https = normalized_source.starts_with("https://"); + let is_http = normalized_source.starts_with("http://"); + if is_https || is_http { + if is_http && !Self::is_loopback_http_url(&file_or_url)? { + return Err(MeasurementFormatError::InsecureHttpNotLoopback(file_or_url)); + } + + let response = ureq::get(&file_or_url) + .timeout(Duration::from_secs(10)) + .call() + .map_err(|error| MeasurementFormatError::Ureq(Box::new(error)))?; + let mut measurements_json = Vec::new(); + response.into_reader().read_to_end(&mut measurements_json)?; + Self::from_json_bytes(measurements_json) + } else { + Self::from_json_bytes(std::fs::read(file_or_url)?) + } + } + /// Given the path to a JSON file containing measurements, return a /// [MeasurementPolicy] pub async fn from_file(measurement_file: PathBuf) -> Result { @@ -820,6 +855,8 @@ pub enum MeasurementFormatError { ParseInt(#[from] std::num::ParseIntError), #[error("Failed to read measurements from URL: {0}")] Reqwest(#[from] reqwest::Error), + #[error("Failed to synchronously read measurements from URL: {0}")] + Ureq(#[source] Box), #[error("Invalid URL: {0}")] InvalidUri(#[from] InvalidUri), #[error("Refusing to load measurement policy over plain HTTP from non-loopback host: {0}")] diff --git a/crates/attested-tls/src/lib.rs b/crates/attested-tls/src/lib.rs index c6da230..f93cf8b 100644 --- a/crates/attested-tls/src/lib.rs +++ b/crates/attested-tls/src/lib.rs @@ -487,6 +487,10 @@ impl AttestedCertificateVerifier { pub fn try_default( attestation_verifier: AttestationVerifier, ) -> Result { + if attestation_verifier.has_dynamic_measurement_policy() { + return Err(AttestedTlsError::DynamicMeasurementPolicyUnsupported); + } + let crypto_provider = default_crypto_provider()?; let server_verifier = WebPkiServerVerifier::builder(Arc::new({ @@ -956,6 +960,10 @@ impl AttestedCertificateVerifierBuilder { /// Finish the build of AttestedCertificateVerifier pub fn finish(self) -> Result { + if self.attestation_verifier.has_dynamic_measurement_policy() { + return Err(AttestedTlsError::DynamicMeasurementPolicyUnsupported); + } + let crypto_provider = match self.crypto_provider { None => default_crypto_provider()?, Some(provider) => provider, @@ -1001,6 +1009,8 @@ impl AttestedCertificateVerifierBuilder { #[derive(Debug, Error)] pub enum AttestedTlsError { + #[error("Dynamic measurement policies are not supported by AttestedCertificateVerifier")] + DynamicMeasurementPolicyUnsupported, #[error("Certificate validity duration must be at least {minimum:?}")] InvalidCertificateValidityDuration { minimum: Duration }, #[error("Failed to generate certificate key pair: {0}")] @@ -1727,6 +1737,25 @@ mod tests { .unwrap(); } + #[test] + fn attested_certificate_verifier_rejects_dynamic_measurement_policies() { + let dynamic_verifier = AttestationVerifier::builder( + attestation::measurements::MeasurementPolicy::expect_none(), + ) + .with_no_internal_pccs() + .with_dynamic_measurements_file_or_url("measurements.json".into()) + .build(); + + assert!(matches!( + AttestedCertificateVerifier::build(dynamic_verifier.clone()).finish(), + Err(AttestedTlsError::DynamicMeasurementPolicyUnsupported) + )); + assert!(matches!( + AttestedCertificateVerifier::try_default(dynamic_verifier), + Err(AttestedTlsError::DynamicMeasurementPolicyUnsupported) + )); + } + #[tokio::test(flavor = "multi_thread")] async fn sync_verifier_cache_miss_fails_then_succeeds_after_background_fetch() { install_test_crypto_provider();