joinservice: cache certificates for Azure SEV-SNP attestation (#2336)

* add ASK caching in joinservice Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * use cached ASK in Azure SEV-SNP attestation Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * update test charts Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix linter Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix typ Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * make caching mechanism less provider-specific Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * update buildfiles Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * add `omitempty` flag Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com> * frontload certificate getter Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com> * rename frontloaded function Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * pass cached certificates to constructor Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix race condition Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix marshalling of empty certs Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix validator usage Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * [wip] add certcache tests Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * add certcache tests Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * tidy Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix validator test Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * remove unused fields in validator Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix certificate precedence Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * use separate context Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * tidy Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * linter fixes Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * linter fixes Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * Remove unnecessary comment Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com> * use background context Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * Use error format directive Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com> * `azure` -> `Azure` Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com> * improve error messages Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * add x509 -> PEM util function Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * use crypto util functions Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix certificate replacement logic Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * only require ASK from certcache Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * tidy Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix comment typo Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> --------- Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com> Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com>
2025-01-11 07:29:29 -05:00 · 2023-09-29 14:29:50 +02:00 · 2023-09-29 14:29:50 +02:00 · a5021c52d3
commit a5021c52d3
parent 68d8b29335
39 changed files with 1197 additions and 50 deletions
--- a/cli/internal/helm/charts/edgeless/constellation-services/charts/join-service/templates/clusterrole.yaml
+++ b/cli/internal/helm/charts/edgeless/constellation-services/charts/join-service/templates/clusterrole.yaml
@ -28,6 +28,7 @@ rules:
  - configmaps
  verbs:
  - get
+  - create
 - apiGroups:
  - "update.edgeless.systems"
  resources:
--- a/cli/internal/helm/testdata/AWS/constellation-services/charts/join-service/templates/clusterrole.yaml
+++ b/cli/internal/helm/testdata/AWS/constellation-services/charts/join-service/templates/clusterrole.yaml
@ -28,6 +28,7 @@ rules:
  - configmaps
  verbs:
  - get
+  - create
 - apiGroups:
  - "update.edgeless.systems"
  resources:
--- a/cli/internal/helm/testdata/Azure/constellation-services/charts/join-service/templates/clusterrole.yaml
+++ b/cli/internal/helm/testdata/Azure/constellation-services/charts/join-service/templates/clusterrole.yaml
@ -28,6 +28,7 @@ rules:
  - configmaps
  verbs:
  - get
+  - create
 - apiGroups:
  - "update.edgeless.systems"
  resources:
--- a/cli/internal/helm/testdata/GCP/constellation-services/charts/join-service/templates/clusterrole.yaml
+++ b/cli/internal/helm/testdata/GCP/constellation-services/charts/join-service/templates/clusterrole.yaml
@ -28,6 +28,7 @@ rules:
  - configmaps
  verbs:
  - get
+  - create
 - apiGroups:
  - "update.edgeless.systems"
  resources:
--- a/cli/internal/helm/testdata/OpenStack/constellation-services/charts/join-service/templates/clusterrole.yaml
+++ b/cli/internal/helm/testdata/OpenStack/constellation-services/charts/join-service/templates/clusterrole.yaml
@ -28,6 +28,7 @@ rules:
  - configmaps
  verbs:
  - get
+  - create
 - apiGroups:
  - "update.edgeless.systems"
  resources:
--- a/cli/internal/helm/testdata/QEMU/constellation-services/charts/join-service/templates/clusterrole.yaml
+++ b/cli/internal/helm/testdata/QEMU/constellation-services/charts/join-service/templates/clusterrole.yaml
@ -28,6 +28,7 @@ rules:
  - configmaps
  verbs:
  - get
+  - create
 - apiGroups:
  - "update.edgeless.systems"
  resources:
--- a/internal/attestation/azure/snp/BUILD.bazel
+++ b/internal/attestation/azure/snp/BUILD.bazel
@ -19,6 +19,7 @@ go_library(
        "//internal/attestation/vtpm",
        "//internal/cloud/azure",
        "//internal/config",
+        "//internal/constants",
        "@com_github_edgelesssys_go_azguestattestation//maa",
        "@com_github_google_go_sev_guest//abi",
        "@com_github_google_go_sev_guest//kds",
--- a/internal/attestation/azure/snp/validator.go
+++ b/internal/attestation/azure/snp/validator.go
@ -24,6 +24,7 @@ import (
 	"github.com/edgelesssys/constellation/v2/internal/attestation/variant"
 	"github.com/edgelesssys/constellation/v2/internal/attestation/vtpm"
 	"github.com/edgelesssys/constellation/v2/internal/config"
+	"github.com/edgelesssys/constellation/v2/internal/constants"
 	"github.com/google/go-sev-guest/abi"
 	"github.com/google/go-sev-guest/kds"
 	spb "github.com/google/go-sev-guest/proto/sevsnp"
@ -101,19 +102,28 @@ func NewValidator(cfg *config.AzureSEVSNP, log attestation.Logger) *Validator {
 // getTrustedKey establishes trust in the given public key.
 // It does so by verifying the SNP attestation document.
 func (v *Validator) getTrustedKey(ctx context.Context, attDoc vtpm.AttestationDocument, extraData []byte) (crypto.PublicKey, error) {
+	trustedAsk := (*x509.Certificate)(&v.config.AMDSigningKey) // ASK, cached by the Join-Service
+	trustedArk := (*x509.Certificate)(&v.config.AMDRootKey)    // ARK, specified in the Constellation config
+
+	// fallback certificates, used if not present in THIM response.
+	cachedCerts := sevSnpCerts{
+		ask: trustedAsk,
+		ark: trustedArk,
+	}
+
 	// transform the instanceInfo received from Microsoft into a verifiable attestation report format.
 	var instanceInfo azureInstanceInfo
 	if err := json.Unmarshal(attDoc.InstanceInfo, &instanceInfo); err != nil {
 		return nil, fmt.Errorf("unmarshalling instanceInfo: %w", err)
 	}
-	att, err := instanceInfo.attestationWithCerts(v.log, v.getter)
+
+	att, err := instanceInfo.attestationWithCerts(v.log, v.getter, cachedCerts)
 	if err != nil {
 		return nil, fmt.Errorf("parsing attestation report: %w", err)
 	}

-	// Verify the attestation report's certificates.
-	trustedArk := x509.Certificate(v.config.AMDRootKey)             // ARK, specified in Constellation config.
-	ask, err := x509.ParseCertificate(att.CertificateChain.AskCert) // ASK, as reported from THIM / KDS.
+	// ASK, as cached in joinservice or reported from THIM / KDS.
+	ask, err := x509.ParseCertificate(att.CertificateChain.AskCert)
 	if err != nil {
 		return nil, fmt.Errorf("parsing ASK certificate: %w", err)
 	}
@ -125,7 +135,7 @@ func (v *Validator) getTrustedKey(ctx context.Context, attDoc vtpm.AttestationDo
 					Product: "Milan",
 					ProductCerts: &trust.ProductCerts{
 						Ask: ask,
-						Ark: &trustedArk,
+						Ark: trustedArk,
 					},
 				},
 			},
@ -246,9 +256,13 @@ type azureInstanceInfo struct {
 }

 // attestationWithCerts returns a formatted version of the attestation report and its certificates from the instanceInfo.
-// if the VCEK certificate or the certificate chain is not present, the given getter is used to retrieve them
-// from the AMD KDS.
-func (a *azureInstanceInfo) attestationWithCerts(logger attestation.Logger, getter trust.HTTPSGetter) (*spb.Attestation, error) {
+// Certificates are retrieved in the following precedence:
+// 1. ASK or ARK from THIM
+// 2. ASK or ARK from fallbackCerts
+// 3. ASK or ARK from AMD KDS.
+func (a *azureInstanceInfo) attestationWithCerts(logger attestation.Logger, getter trust.HTTPSGetter,
+	fallbackCerts sevSnpCerts,
+) (*spb.Attestation, error) {
 	report, err := abi.ReportToProto(a.AttestationReport)
 	if err != nil {
 		return nil, fmt.Errorf("converting report to proto: %w", err)
@ -282,17 +296,29 @@ func (a *azureInstanceInfo) attestationWithCerts(logger attestation.Logger, gett
 		att.CertificateChain.VcekCert = vcek
 	}

-	// If the certificate chain is present, parse it and format it.
+	// If the certificate chain from THIM is present, parse it and format it.
 	ask, ark, err := a.parseCertChain()
 	if err != nil {
 		logger.Warnf("Error parsing certificate chain: %v", err)
 	}
 	if ask != nil {
+		logger.Infof("Using ASK certificate from Azure THIM")
 		att.CertificateChain.AskCert = ask.Raw
 	}
 	if ark != nil {
+		logger.Infof("Using ARK certificate from Azure THIM")
 		att.CertificateChain.ArkCert = ark.Raw
 	}
+
+	// If a cached ASK or an ARK from the Constellation config is present, use it.
+	if att.CertificateChain.AskCert == nil && fallbackCerts.ask != nil {
+		logger.Infof("Using cached ASK certificate")
+		att.CertificateChain.AskCert = fallbackCerts.ask.Raw
+	}
+	if att.CertificateChain.ArkCert == nil && fallbackCerts.ark != nil {
+		logger.Infof("Using ARK certificate from %s", constants.ConfigFilename)
+		att.CertificateChain.ArkCert = fallbackCerts.ark.Raw
+	}
 	// Otherwise, retrieve it from AMD KDS.
 	if att.CertificateChain.AskCert == nil || att.CertificateChain.ArkCert == nil {
 		logger.Infof(
@ -304,10 +330,12 @@ func (a *azureInstanceInfo) attestationWithCerts(logger attestation.Logger, gett
 		if err != nil {
 			return nil, fmt.Errorf("retrieving certificate chain from AMD KDS: %w", err)
 		}
-		if att.CertificateChain.AskCert == nil {
+		if att.CertificateChain.AskCert == nil && kdsCertChain.Ask != nil {
+			logger.Infof("Using ASK certificate from AMD KDS")
 			att.CertificateChain.AskCert = kdsCertChain.Ask.Raw
 		}
-		if att.CertificateChain.ArkCert == nil {
+		if att.CertificateChain.ArkCert == nil && kdsCertChain.Ask != nil {
+			logger.Infof("Using ARK certificate from AMD KDS")
 			att.CertificateChain.ArkCert = kdsCertChain.Ark.Raw
 		}
 	}
@ -315,6 +343,11 @@ func (a *azureInstanceInfo) attestationWithCerts(logger attestation.Logger, gett
 	return att, nil
 }

+type sevSnpCerts struct {
+	ask *x509.Certificate
+	ark *x509.Certificate
+}
+
 // parseCertChain parses the certificate chain from the instanceInfo into x509-formatted ASK and ARK certificates.
 // If less than 2 certificates are present, only the present certificate is returned.
 // If more than 2 certificates are present, an error is returned.
--- a/internal/attestation/azure/snp/validator_test.go
+++ b/internal/attestation/azure/snp/validator_test.go
@ -10,6 +10,7 @@ import (
 	"bytes"
 	"context"
 	"crypto/sha256"
+	"crypto/x509"
 	"encoding/base64"
 	"encoding/binary"
 	"encoding/hex"
@ -169,22 +170,31 @@ func TestParseVCEK(t *testing.T) {
 	}
 }

-// TestInstanceInfoAttestation tests the basic unmarshalling of the attestation report.
+// TestInstanceInfoAttestation tests the basic unmarshalling of the attestation report and the ASK / ARK precedence.
 func TestInstanceInfoAttestation(t *testing.T) {
 	defaultReport := testdata.AttestationReport
+	testdataArk, testdataAsk := mustCertChainToPem(t, testdata.CertChain)
+	exampleCert := &x509.Certificate{
+		Raw: []byte{1, 2, 3},
+	}
 	cfg := config.DefaultForAzureSEVSNP()

 	testCases := map[string]struct {
 		report        []byte
 		vcek          []byte
 		certChain     []byte
+		fallbackCerts sevSnpCerts
 		getter        *stubHTTPSGetter
+		expectedArk   *x509.Certificate
+		expectedAsk   *x509.Certificate
 		wantErr       bool
 	}{
 		"success": {
 			report:      defaultReport,
 			vcek:        testdata.AzureThimVCEK,
 			certChain:   testdata.CertChain,
+			expectedArk: testdataArk,
+			expectedAsk: testdataAsk,
 		},
 		"retrieve vcek": {
 			report:    defaultReport,
@ -196,6 +206,8 @@ func TestInstanceInfoAttestation(t *testing.T) {
 				},
 				nil,
 			),
+			expectedArk: testdataArk,
+			expectedAsk: testdataAsk,
 		},
 		"retrieve certchain": {
 			report: defaultReport,
@ -207,6 +219,37 @@ func TestInstanceInfoAttestation(t *testing.T) {
 				},
 				nil,
 			),
+			expectedArk: testdataArk,
+			expectedAsk: testdataAsk,
+		},
+		"use fallback certs": {
+			report: defaultReport,
+			vcek:   testdata.AzureThimVCEK,
+			fallbackCerts: sevSnpCerts{
+				ask: exampleCert,
+				ark: exampleCert,
+			},
+			getter: newStubHTTPSGetter(
+				&urlResponseMatcher{},
+				nil,
+			),
+			expectedArk: exampleCert,
+			expectedAsk: exampleCert,
+		},
+		"use certchain with fallback certs": {
+			report:    defaultReport,
+			certChain: testdata.CertChain,
+			vcek:      testdata.AzureThimVCEK,
+			fallbackCerts: sevSnpCerts{
+				ask: &x509.Certificate{},
+				ark: &x509.Certificate{},
+			},
+			getter: newStubHTTPSGetter(
+				&urlResponseMatcher{},
+				nil,
+			),
+			expectedArk: testdataArk,
+			expectedAsk: testdataAsk,
 		},
 		"retrieve vcek and certchain": {
 			report: defaultReport,
@ -219,6 +262,8 @@ func TestInstanceInfoAttestation(t *testing.T) {
 				},
 				nil,
 			),
+			expectedArk: testdataArk,
+			expectedAsk: testdataAsk,
 		},
 		"report too short": {
 			report:  defaultReport[:len(defaultReport)-100],
@ -245,7 +290,7 @@ func TestInstanceInfoAttestation(t *testing.T) {
 				VCEK:              tc.vcek,
 			}

-			att, err := instanceInfo.attestationWithCerts(logger.NewTest(t), tc.getter)
+			att, err := instanceInfo.attestationWithCerts(logger.NewTest(t), tc.getter, tc.fallbackCerts)
 			if tc.wantErr {
 				assert.Error(err)
 			} else {
@ -263,11 +308,21 @@ func TestInstanceInfoAttestation(t *testing.T) {
 				assert.True(tcbValues.TeeSpl >= cfg.TEEVersion.Value)
 				assert.True(tcbValues.SnpSpl >= cfg.SNPVersion.Value)
 				assert.True(tcbValues.UcodeSpl >= cfg.MicrocodeVersion.Value)
+				assert.Equal(tc.expectedArk.Raw, att.CertificateChain.ArkCert)
+				assert.Equal(tc.expectedAsk.Raw, att.CertificateChain.AskCert)
 			}
 		})
 	}
 }

+func mustCertChainToPem(t *testing.T, certchain []byte) (ark, ask *x509.Certificate) {
+	t.Helper()
+	a := azureInstanceInfo{CertChain: certchain}
+	ask, ark, err := a.parseCertChain()
+	require.NoError(t, err)
+	return ark, ask
+}
+
 type stubHTTPSGetter struct {
 	urlResponseMatcher *urlResponseMatcher // maps responses to requested URLs
 	err                error
--- a/internal/attestation/choose/choose.go
+++ b/internal/attestation/choose/choose.go
@ -66,6 +66,6 @@ func Validator(cfg config.AttestationCfg, log attestation.Logger) (atls.Validato
 	case *config.DummyCfg:
 		return atls.NewFakeValidator(variant.Dummy{}), nil
 	default:
-		return nil, fmt.Errorf("unknown attestation variant")
+		return nil, fmt.Errorf("unknown attestation variant: %s", cfg.GetVariant())
 	}
 }
--- a/internal/attestation/variant/variant.go
+++ b/internal/attestation/variant/variant.go
@ -134,7 +134,7 @@ func ValidProvider(provider cloudprovider.Provider, variant Variant) bool {
 	return false
 }

-// Dummy OID for testfing.
+// Dummy OID for testing.
 type Dummy struct{}

 // OID returns the struct's object identifier.
--- a/internal/config/attestation.go
+++ b/internal/config/attestation.go
@ -65,18 +65,27 @@ type Certificate x509.Certificate

 // MarshalJSON marshals the certificate to PEM.
 func (c Certificate) MarshalJSON() ([]byte, error) {
+	if len(c.Raw) == 0 {
+		return json.Marshal(new(string))
+	}
 	pem := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: c.Raw})
 	return json.Marshal(string(pem))
 }

 // MarshalYAML marshals the certificate to PEM.
 func (c Certificate) MarshalYAML() (any, error) {
+	if len(c.Raw) == 0 {
+		return "", nil
+	}
 	pem := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: c.Raw})
 	return string(pem), nil
 }

 // UnmarshalJSON unmarshals the certificate from PEM.
 func (c *Certificate) UnmarshalJSON(data []byte) error {
+	if len(data) == 0 {
+		return nil
+	}
 	return c.unmarshal(func(val any) error {
 		return json.Unmarshal(data, val)
 	})
@ -92,6 +101,9 @@ func (c *Certificate) unmarshal(unmarshalFunc func(any) error) error {
 	if err := unmarshalFunc(&pemData); err != nil {
 		return err
 	}
+	if pemData == "" {
+		return nil
+	}
 	block, _ := pem.Decode([]byte(pemData))
 	cert, err := x509.ParseCertificate(block.Bytes)
 	if err != nil {
--- a/internal/config/attestation_test.go
+++ b/internal/config/attestation_test.go
@ -77,6 +77,19 @@ func TestCertificateMarshalJSON(t *testing.T) {
 	assert.JSONEq(jsonCert, string(out))
 }

+func TestEmptyCertificateMarshalJSON(t *testing.T) {
+	require := require.New(t)
+	assert := assert.New(t)
+
+	jsonCert := "\"\""
+	var cert Certificate
+	require.NoError(json.Unmarshal([]byte(jsonCert), &cert))
+
+	out, err := json.Marshal(cert)
+	require.NoError(err)
+	assert.JSONEq(jsonCert, string(out))
+}
+
 func TestCertificateMarshalYAML(t *testing.T) {
 	require := require.New(t)
 	assert := assert.New(t)
@ -89,3 +102,16 @@ func TestCertificateMarshalYAML(t *testing.T) {
 	require.NoError(err)
 	assert.YAMLEq(yamlCert, string(out))
 }
+
+func TestEmptyCertificateMarshalYAML(t *testing.T) {
+	require := require.New(t)
+	assert := assert.New(t)
+
+	yamlCert := "\"\""
+	var cert Certificate
+	require.NoError(yaml.Unmarshal([]byte(yamlCert), &cert))
+
+	out, err := yaml.Marshal(cert)
+	require.NoError(err)
+	assert.YAMLEq(yamlCert, string(out))
+}
--- a/internal/config/config.go
+++ b/internal/config/config.go
@ -1118,6 +1118,9 @@ type AzureSEVSNP struct {
 	// description: |
 	//   AMD Root Key certificate used to verify the SEV-SNP certificate chain.
 	AMDRootKey Certificate `json:"amdRootKey" yaml:"amdRootKey"`
+	// description: |
+	//   AMD Signing Key certificate used to verify the SEV-SNP VCEK / VLEK certificate.
+	AMDSigningKey Certificate `json:"amdSigningKey,omitempty" yaml:"amdSigningKey,omitempty" validate:"len=0"`
 }

 // setWantLatestToFalse sets the WantLatest field to false for all versions in order to unmarshal the numerical versions instead of the string "latest".
--- a/internal/config/config_doc.go
+++ b/internal/config/config_doc.go
@ -590,7 +590,7 @@ func init() {
 			FieldName: "azureSEVSNP",
 		},
 	}
-	AzureSEVSNPDoc.Fields = make([]encoder.Doc, 7)
+	AzureSEVSNPDoc.Fields = make([]encoder.Doc, 8)
 	AzureSEVSNPDoc.Fields[0].Name = "measurements"
 	AzureSEVSNPDoc.Fields[0].Type = "M"
 	AzureSEVSNPDoc.Fields[0].Note = ""
@ -626,6 +626,11 @@ func init() {
 	AzureSEVSNPDoc.Fields[6].Note = ""
 	AzureSEVSNPDoc.Fields[6].Description = "AMD Root Key certificate used to verify the SEV-SNP certificate chain."
 	AzureSEVSNPDoc.Fields[6].Comments[encoder.LineComment] = "AMD Root Key certificate used to verify the SEV-SNP certificate chain."
+	AzureSEVSNPDoc.Fields[7].Name = "amdSigningKey"
+	AzureSEVSNPDoc.Fields[7].Type = "Certificate"
+	AzureSEVSNPDoc.Fields[7].Note = ""
+	AzureSEVSNPDoc.Fields[7].Description = "AMD Signing Key certificate used to verify the SEV-SNP VCEK / VLEK certificate."
+	AzureSEVSNPDoc.Fields[7].Comments[encoder.LineComment] = "AMD Signing Key certificate used to verify the SEV-SNP VCEK / VLEK certificate."

 	AzureTrustedLaunchDoc.Type = "AzureTrustedLaunch"
 	AzureTrustedLaunchDoc.Comments[encoder.LineComment] = "AzureTrustedLaunch is the configuration for Azure Trusted Launch attestation."
--- a/internal/constants/constants.go
+++ b/internal/constants/constants.go
@ -128,6 +128,12 @@ const (
 	K8sVersionFieldName = "cluster-version"
 	// ComponentsListKey is the name of the key holding the list of components in the components configMap.
 	ComponentsListKey = "components"
+	// SevSnpCertCacheConfigMapName is the name of the configMap holding the SEV-SNP certificate cache in the join service.
+	SevSnpCertCacheConfigMapName = "sev-snp-cert-cache"
+	// CertCacheAskKey is the name of the key holding the ASK certificate in the SEV-SNP certificate cache.
+	CertCacheAskKey = "ask"
+	// CertCacheArkKey is the name of the key holding the ARK certificate in the SEV-SNP certificate cache.
+	CertCacheArkKey = "ark"
 	// NodeVersionResourceName resource name used for NodeVersion in constellation-operator and CLI.
 	NodeVersionResourceName = "constellation-version"
 	// NodeKubernetesComponentsAnnotationKey is the name of the annotation holding the reference to the ConfigMap listing all K8s components.
--- a/internal/crypto/crypto.go
+++ b/internal/crypto/crypto.go
@ -8,6 +8,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 package crypto

 import (
+	"bytes"
 	"crypto/rand"
 	"crypto/sha256"
 	"crypto/x509"
@ -61,7 +62,8 @@ func GenerateRandomBytes(length int) ([]byte, error) {
 	return nonce, nil
 }

-// PemToX509Cert takes a list of PEM encoded certificates, parses the first one and returns it.
+// PemToX509Cert takes a list of PEM-encoded certificates, parses the first one and returns it
+// as an x.509 certificate.
 func PemToX509Cert(raw []byte) (*x509.Certificate, error) {
 	decoded, _ := pem.Decode(raw)
 	if decoded == nil {
@ -73,3 +75,13 @@ func PemToX509Cert(raw []byte) (*x509.Certificate, error) {
 	}
 	return cert, nil
 }
+
+// X509CertToPem takes an x.509 certificate and returns it as a PEM-encoded certificate.
+func X509CertToPem(cert *x509.Certificate) ([]byte, error) {
+	outWriter := &bytes.Buffer{}
+	err := pem.Encode(outWriter, &pem.Block{Type: "CERTIFICATE", Bytes: cert.Raw})
+	if err != nil {
+		return nil, fmt.Errorf("encode certificate: %w", err)
+	}
+	return outWriter.Bytes(), nil
+}
--- a/internal/crypto/crypto_test.go
+++ b/internal/crypto/crypto_test.go
@ -7,6 +7,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 package crypto

 import (
+	"crypto/x509"
 	"testing"

 	"github.com/edgelesssys/constellation/v2/internal/crypto/testvector"
@ -119,3 +120,58 @@ func TestGenerateRandomBytes(t *testing.T) {
 	require.NoError(err)
 	assert.Len(n3, 16)
 }
+
+func TestPemToX509Cert(t *testing.T) {
+	testCases := map[string]struct {
+		pemCert []byte
+		wantErr bool
+	}{
+		// TODO(msanft): Add more test cases with testdata
+		"invalid cert": {
+			pemCert: []byte("invalid"),
+			wantErr: true,
+		},
+		"empty cert": {
+			pemCert: []byte{},
+			wantErr: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			_, err := PemToX509Cert(tc.pemCert)
+			if tc.wantErr {
+				assert.Error(err)
+			} else {
+				assert.NoError(err)
+			}
+		})
+	}
+}
+
+func TestX509ToPemCert(t *testing.T) {
+	testCases := map[string]struct {
+		cert    *x509.Certificate
+		wantErr bool
+	}{
+		"success": {
+			cert: &x509.Certificate{},
+		},
+		// TODO(msanft): Add more test cases with testdata
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			_, err := X509CertToPem(tc.cert)
+			if tc.wantErr {
+				assert.Error(err)
+			} else {
+				assert.NoError(err)
+			}
+		})
+	}
+}
--- a/joinservice/cmd/BUILD.bazel
+++ b/joinservice/cmd/BUILD.bazel
@ -21,8 +21,10 @@ go_library(
        "//internal/file",
        "//internal/grpc/atlscredentials",
        "//internal/logger",
+        "//joinservice/internal/certcache",
        "//joinservice/internal/kms",
        "//joinservice/internal/kubeadm",
+        "//joinservice/internal/kubernetes",
        "//joinservice/internal/kubernetesca",
        "//joinservice/internal/server",
        "//joinservice/internal/watcher",
--- a/joinservice/cmd/main.go
+++ b/joinservice/cmd/main.go
@ -28,8 +28,10 @@ import (
 	"github.com/edgelesssys/constellation/v2/internal/file"
 	"github.com/edgelesssys/constellation/v2/internal/grpc/atlscredentials"
 	"github.com/edgelesssys/constellation/v2/internal/logger"
+	"github.com/edgelesssys/constellation/v2/joinservice/internal/certcache"
 	"github.com/edgelesssys/constellation/v2/joinservice/internal/kms"
 	"github.com/edgelesssys/constellation/v2/joinservice/internal/kubeadm"
+	"github.com/edgelesssys/constellation/v2/joinservice/internal/kubernetes"
 	"github.com/edgelesssys/constellation/v2/joinservice/internal/kubernetesca"
 	"github.com/edgelesssys/constellation/v2/joinservice/internal/server"
 	"github.com/edgelesssys/constellation/v2/joinservice/internal/watcher"
@ -56,11 +58,23 @@ func main() {

 	handler := file.NewHandler(afero.NewOsFs())

-	variant, err := variant.FromString(*attestationVariant)
+	kubeClient, err := kubernetes.New()
+	if err != nil {
+		log.With(zap.Error(err)).Fatalf("Failed to create Kubernetes client")
+	}
+
+	attVariant, err := variant.FromString(*attestationVariant)
 	if err != nil {
 		log.With(zap.Error(err)).Fatalf("Failed to parse attestation variant")
 	}
-	validator, err := watcher.NewValidator(log.Named("validator"), variant, handler)
+
+	certCacheClient := certcache.NewClient(log.Named("certcache"), kubeClient, attVariant)
+	cachedCerts, err := certCacheClient.CreateCertChainCache(context.Background())
+	if err != nil {
+		log.With(zap.Error(err)).Fatalf("Failed to create certificate chain cache")
+	}
+
+	validator, err := watcher.NewValidator(log.Named("validator"), attVariant, handler, cachedCerts)
 	if err != nil {
 		flag.Usage()
 		log.With(zap.Error(err)).Fatalf("Failed to create validator")
@ -68,9 +82,10 @@ func main() {

 	creds := atlscredentials.New(nil, []atls.Validator{validator})

-	ctx, cancel := context.WithTimeout(context.Background(), vpcIPTimeout)
+	vpcCtx, cancel := context.WithTimeout(context.Background(), vpcIPTimeout)
 	defer cancel()
-	vpcIP, err := getVPCIP(ctx, *provider)
+
+	vpcIP, err := getVPCIP(vpcCtx, *provider)
 	if err != nil {
 		log.With(zap.Error(err)).Fatalf("Failed to get IP in VPC")
 	}
@ -91,6 +106,7 @@ func main() {
 		kubernetesca.New(log.Named("certificateAuthority"), handler),
 		kubeadm,
 		keyServiceClient,
+		kubeClient,
 		log.Named("server"),
 	)
 	if err != nil {
--- a/joinservice/internal/certcache/BUILD.bazel
+++ b/joinservice/internal/certcache/BUILD.bazel
@ -0,0 +1,37 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("//bazel/go:go_test.bzl", "go_test")
+
+go_library(
+    name = "certcache",
+    srcs = ["certcache.go"],
+    importpath = "github.com/edgelesssys/constellation/v2/joinservice/internal/certcache",
+    visibility = ["//joinservice:__subpackages__"],
+    deps = [
+        "//internal/attestation/variant",
+        "//internal/constants",
+        "//internal/crypto",
+        "//internal/logger",
+        "//joinservice/internal/certcache/amdkds",
+        "@com_github_google_go_sev_guest//abi",
+        "@com_github_google_go_sev_guest//verify/trust",
+        "@io_k8s_apimachinery//pkg/api/errors",
+    ],
+)
+
+go_test(
+    name = "certcache_test",
+    srcs = ["certcache_test.go"],
+    embed = [":certcache"],
+    deps = [
+        "//internal/attestation/variant",
+        "//internal/constants",
+        "//internal/crypto",
+        "//internal/logger",
+        "//joinservice/internal/certcache/testdata",
+        "@com_github_google_go_sev_guest//abi",
+        "@com_github_stretchr_testify//assert",
+        "@com_github_stretchr_testify//require",
+        "@io_k8s_apimachinery//pkg/api/errors",
+        "@io_k8s_apimachinery//pkg/runtime/schema",
+    ],
+)
--- a/joinservice/internal/certcache/amdkds/BUILD.bazel
+++ b/joinservice/internal/certcache/amdkds/BUILD.bazel
@ -0,0 +1,26 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("//bazel/go:go_test.bzl", "go_test")
+
+go_library(
+    name = "amdkds",
+    srcs = ["amdkds.go"],
+    importpath = "github.com/edgelesssys/constellation/v2/joinservice/internal/certcache/amdkds",
+    visibility = ["//joinservice:__subpackages__"],
+    deps = [
+        "@com_github_google_go_sev_guest//abi",
+        "@com_github_google_go_sev_guest//verify/trust",
+    ],
+)
+
+go_test(
+    name = "amdkds_test",
+    srcs = ["amdkds_test.go"],
+    embed = [":amdkds"],
+    deps = [
+        "//internal/logger",
+        "//joinservice/internal/certcache/amdkds/testdata",
+        "@com_github_google_go_sev_guest//abi",
+        "@com_github_google_go_sev_guest//verify/trust",
+        "@com_github_stretchr_testify//assert",
+    ],
+)
--- a/joinservice/internal/certcache/amdkds/amdkds.go
+++ b/joinservice/internal/certcache/amdkds/amdkds.go
@ -0,0 +1,38 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+// The AMDKDS package implements interaction with the AMD KDS (Key Distribution Service).
+package amdkds
+
+import (
+	"crypto/x509"
+	"fmt"
+
+	"github.com/google/go-sev-guest/abi"
+	"github.com/google/go-sev-guest/verify/trust"
+)
+
+// KDSClient is a client for interacting with the AMD KDS.
+type KDSClient struct {
+	getter trust.HTTPSGetter
+}
+
+// NewKDSClient creates a new KDS Client.
+func NewKDSClient(getter trust.HTTPSGetter) *KDSClient {
+	return &KDSClient{
+		getter: getter,
+	}
+}
+
+// CertChain queries the AMD KDS for the certificate chain for given signing type (VCEK / VLEK).
+func (c *KDSClient) CertChain(signingType abi.ReportSigner) (ask, ark *x509.Certificate, err error) {
+	askark, err := trust.GetProductChain("Milan", signingType, c.getter)
+	if err != nil {
+		return nil, nil, fmt.Errorf("retrieving certificate chain: %w", err)
+	}
+
+	return askark.Ask, askark.Ark, nil
+}
--- a/joinservice/internal/certcache/amdkds/amdkds_test.go
+++ b/joinservice/internal/certcache/amdkds/amdkds_test.go
@ -0,0 +1,74 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package amdkds
+
+import (
+	"testing"
+
+	"github.com/edgelesssys/constellation/v2/internal/logger"
+	"github.com/edgelesssys/constellation/v2/joinservice/internal/certcache/amdkds/testdata"
+	"github.com/google/go-sev-guest/abi"
+	"github.com/google/go-sev-guest/verify/trust"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCertChain(t *testing.T) {
+	testCases := map[string]struct {
+		getter  *stubGetter
+		wantErr bool
+	}{
+		"success": {
+			getter: &stubGetter{
+				log: logger.NewTest(t),
+				ret: testdata.CertChain,
+			},
+		},
+		"getter error": {
+			getter: &stubGetter{
+				log: logger.NewTest(t),
+				err: assert.AnError,
+			},
+			wantErr: true,
+		},
+		"empty cert chain": {
+			getter: &stubGetter{
+				log: logger.NewTest(t),
+				ret: nil,
+			},
+			wantErr: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			// Clear the product cert cache to ensure that the test cases are independent.
+			trust.ClearProductCertCache()
+
+			assert := assert.New(t)
+
+			kdsClient := NewKDSClient(tc.getter)
+
+			_, _, err := kdsClient.CertChain(abi.NoneReportSigner)
+			if tc.wantErr {
+				assert.Error(err)
+			} else {
+				assert.NoError(err)
+			}
+		})
+	}
+}
+
+type stubGetter struct {
+	log *logger.Logger
+	ret []byte
+	err error
+}
+
+func (s *stubGetter) Get(url string) ([]byte, error) {
+	s.log.Debugf("Request to %s", url)
+	return s.ret, s.err
+}
--- a/joinservice/internal/certcache/amdkds/testdata/BUILD.bazel
+++ b/joinservice/internal/certcache/amdkds/testdata/BUILD.bazel
@ -0,0 +1,9 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "testdata",
+    srcs = ["testdata.go"],
+    embedsrcs = ["certchain.pem"],
+    importpath = "github.com/edgelesssys/constellation/v2/joinservice/internal/certcache/amdkds/testdata",
+    visibility = ["//joinservice:__subpackages__"],
+)
--- a/joinservice/internal/certcache/amdkds/testdata/certchain.pem
+++ b/joinservice/internal/certcache/amdkds/testdata/certchain.pem
@ -0,0 +1,74 @@
+-----BEGIN CERTIFICATE-----
+MIIGiTCCBDigAwIBAgIDAQABMEYGCSqGSIb3DQEBCjA5oA8wDQYJYIZIAWUDBAIC
+BQChHDAaBgkqhkiG9w0BAQgwDQYJYIZIAWUDBAICBQCiAwIBMKMDAgEBMHsxFDAS
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+ajxCW3Seiws6r1Zm+tCuVbMiNtpS9ThjNX4uve5thyfE2DgoxRFvY1CsoF5M
+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
+MIIGYzCCBBKgAwIBAgIDAQAAMEYGCSqGSIb3DQEBCjA5oA8wDQYJYIZIAWUDBAIC
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+KGKqPQ3P+N9r1hjEFY1plBg93t53OOo49GNI+V1zvXPLI6xIFVsh+mto2RtgEX/e
+pmMKTNN6psW88qg7c1hTWtN6MbRuQ0vm+O+/2tKBF2h8THb94OvvHHoFDpbCELlq
+HnIYhxy0YKXGyaW1NjfULxrrmxVW4wcn5E8GddmvNa6yYm8scJagEi13mhGu4Jqh
+3QU3sf8iUSUr09xQDwHtOQUVIqx4maBZPBtSMf+qUDtjXSSq8lfWcd8bLr9mdsUn
+JZJ0+tuPMKmBnSH860llKk+VpVQsgqbzDIvOLvD6W1Umq25boxCYJ+TuBoa4s+HH
+CViAvgT9kf/rBq1d+ivj6skkHxuzcxbk1xv6ZGxrteJxVH7KlX7YRdZ6eARKwLe4
+AFZEAwoKCQ==
+-----END CERTIFICATE-----
--- a/joinservice/internal/certcache/amdkds/testdata/testdata.go
+++ b/joinservice/internal/certcache/amdkds/testdata/testdata.go
@ -0,0 +1,15 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+// Package testdata contains testing data for an attestation process.
+package testdata
+
+import _ "embed"
+
+// CertChain is a valid certificate chain (PEM, as returned from Azure THIM) for the VCEK certificate.
+//
+//go:embed certchain.pem
+var CertChain []byte
--- a/joinservice/internal/certcache/certcache.go
+++ b/joinservice/internal/certcache/certcache.go
@ -0,0 +1,203 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+// Package certcache implements an in-cluster SEV-SNP certificate cache.
+package certcache
+
+import (
+	"context"
+	"crypto/x509"
+	"fmt"
+
+	"github.com/edgelesssys/constellation/v2/internal/attestation/variant"
+	"github.com/edgelesssys/constellation/v2/internal/constants"
+	"github.com/edgelesssys/constellation/v2/internal/crypto"
+	"github.com/edgelesssys/constellation/v2/internal/logger"
+	"github.com/edgelesssys/constellation/v2/joinservice/internal/certcache/amdkds"
+	"github.com/google/go-sev-guest/abi"
+	"github.com/google/go-sev-guest/verify/trust"
+	k8serrors "k8s.io/apimachinery/pkg/api/errors"
+)
+
+// Client is a client for interacting with the certificate chain cache.
+type Client struct {
+	log        *logger.Logger
+	attVariant variant.Variant
+	kdsClient
+	kubeClient kubeClient
+}
+
+// NewClient creates a new CertCacheClient.
+func NewClient(log *logger.Logger, kubeClient kubeClient, attVariant variant.Variant) *Client {
+	kdsClient := amdkds.NewKDSClient(trust.DefaultHTTPSGetter())
+
+	return &Client{
+		attVariant: attVariant,
+		log:        log,
+		kubeClient: kubeClient,
+		kdsClient:  kdsClient,
+	}
+}
+
+// CreateCertChainCache creates a certificate chain cache for the given attestation variant
+// and returns the cached certificates, if applicable.
+// If the certificate chain cache already exists, nothing is done.
+func (c *Client) CreateCertChainCache(ctx context.Context) (*CachedCerts, error) {
+	switch c.attVariant {
+	case variant.AzureSEVSNP{}:
+		c.log.Debugf("Creating Azure SEV-SNP certificate chain cache")
+		ask, ark, err := c.createCertChainCache(ctx, abi.VcekReportSigner)
+		if err != nil {
+			return nil, fmt.Errorf("creating Azure SEV-SNP certificate chain cache: %w", err)
+		}
+		return &CachedCerts{
+			ask: ask,
+			ark: ark,
+		}, nil
+	// TODO(derpsteb): Add AWS
+	default:
+		c.log.Debugf("No certificate chain caching possible for attestation variant %s", c.attVariant)
+		return nil, nil
+	}
+}
+
+// CachedCerts contains the cached certificates.
+type CachedCerts struct {
+	ask *x509.Certificate
+	ark *x509.Certificate
+}
+
+// SevSnpCerts returns the cached SEV-SNP ASK and ARK certificates.
+func (c *CachedCerts) SevSnpCerts() (ask, ark *x509.Certificate) {
+	return c.ask, c.ark
+}
+
+// createCertChainCache creates a certificate chain cache configmap with the ASK and ARK
+// retrieved from the KDS and returns ASK and ARK. If the configmap already exists and both ASK and ARK are present,
+// nothing is done and the existing ASK and ARK are returned. If the configmap already exists but either ASK or ARK
+// are missing, the missing certificate is retrieved from the KDS and the configmap is updated with the missing value.
+func (c *Client) createCertChainCache(ctx context.Context, signingType abi.ReportSigner) (ask, ark *x509.Certificate, err error) {
+	c.log.Debugf("Creating certificate chain cache")
+	var shouldCreateConfigMap bool
+
+	// Check if ASK or ARK is already cached.
+	// If both are cached, return them.
+	// If only one is cached, retrieve the other one from the
+	// KDS and update the configmap with the missing value.
+	cacheAsk, cacheArk, err := c.getCertChainCache(ctx)
+	if k8serrors.IsNotFound(err) {
+		c.log.Debugf("Certificate chain cache does not exist")
+		shouldCreateConfigMap = true
+	} else if err != nil {
+		return nil, nil, fmt.Errorf("getting certificate chain cache: %w", err)
+	}
+	if cacheAsk != nil && cacheArk != nil {
+		c.log.Debugf("ASK and ARK present in cache, returning cached values")
+		return cacheAsk, cacheArk, nil
+	}
+	if cacheAsk != nil {
+		ask = cacheAsk
+	}
+	if cacheArk != nil {
+		ark = cacheArk
+	}
+
+	// If only one certificate is cached, retrieve the other one from the KDS.
+	c.log.Debugf("Retrieving certificate chain from KDS")
+	kdsAsk, kdsArk, err := c.kdsClient.CertChain(signingType)
+	if err != nil {
+		return nil, nil, fmt.Errorf("retrieving certificate chain from KDS: %w", err)
+	}
+	if ask == nil && kdsAsk != nil {
+		ask = kdsAsk
+	}
+	if ark == nil && kdsArk != nil {
+		ark = kdsArk
+	}
+
+	askPem, err := crypto.X509CertToPem(ask)
+	if err != nil {
+		return nil, nil, fmt.Errorf("encoding ASK: %w", err)
+	}
+	arkPem, err := crypto.X509CertToPem(ark)
+	if err != nil {
+		return nil, nil, fmt.Errorf("encoding ARK: %w", err)
+	}
+
+	if shouldCreateConfigMap {
+		// ConfigMap does not exist, create it.
+		c.log.Debugf("Creating certificate chain cache configmap")
+		if err := c.kubeClient.CreateConfigMap(ctx, constants.SevSnpCertCacheConfigMapName, map[string]string{
+			constants.CertCacheAskKey: string(askPem),
+			constants.CertCacheArkKey: string(arkPem),
+		}); err != nil {
+			// If the ConfigMap already exists, another JoinService instance created the certificate cache while this operation was running.
+			// Calling this function again should now retrieve the cached certificates.
+			if k8serrors.IsAlreadyExists(err) {
+				c.log.Debugf("Certificate chain cache configmap already exists, retrieving cached certificates")
+				return c.getCertChainCache(ctx)
+			}
+			return nil, nil, fmt.Errorf("creating certificate chain cache configmap: %w", err)
+		}
+	} else {
+		// ConfigMap already exists but either ASK or ARK are missing. Update the according value.
+		if cacheAsk == nil {
+			if err := c.kubeClient.UpdateConfigMap(ctx, constants.SevSnpCertCacheConfigMapName,
+				constants.CertCacheAskKey, string(askPem)); err != nil {
+				return nil, nil, fmt.Errorf("updating ASK in certificate chain cache configmap: %w", err)
+			}
+		}
+		if cacheArk == nil {
+			if err := c.kubeClient.UpdateConfigMap(ctx, constants.SevSnpCertCacheConfigMapName,
+				constants.CertCacheArkKey, string(arkPem)); err != nil {
+				return nil, nil, fmt.Errorf("updating ARK in certificate chain cache configmap: %w", err)
+			}
+		}
+	}
+
+	return ask, ark, nil
+}
+
+// getCertChainCache returns the cached ASK and ARK certificate, if available. If either of the keys
+// is not present in the configmap, no error is returned.
+func (c *Client) getCertChainCache(ctx context.Context) (ask, ark *x509.Certificate, err error) {
+	c.log.Debugf("Retrieving certificate chain from cache")
+	askRaw, err := c.kubeClient.GetConfigMapData(ctx, constants.SevSnpCertCacheConfigMapName, constants.CertCacheAskKey)
+	if err != nil {
+		return nil, nil, fmt.Errorf("getting ASK from configmap: %w", err)
+	}
+	if askRaw != "" {
+		c.log.Debugf("ASK cache hit")
+		ask, err = crypto.PemToX509Cert([]byte(askRaw))
+		if err != nil {
+			return nil, nil, fmt.Errorf("parsing ASK: %w", err)
+		}
+	}
+
+	arkRaw, err := c.kubeClient.GetConfigMapData(ctx, constants.SevSnpCertCacheConfigMapName, constants.CertCacheArkKey)
+	if err != nil {
+		return nil, nil, fmt.Errorf("getting ARK from configmap: %w", err)
+	}
+	if arkRaw != "" {
+		c.log.Debugf("ARK cache hit")
+		ark, err = crypto.PemToX509Cert([]byte(arkRaw))
+		if err != nil {
+			return nil, nil, fmt.Errorf("parsing ARK: %w", err)
+		}
+	}
+
+	return ask, ark, nil
+}
+
+type kubeClient interface {
+	CreateConfigMap(ctx context.Context, name string, data map[string]string) error
+	GetConfigMapData(ctx context.Context, name, key string) (string, error)
+	UpdateConfigMap(ctx context.Context, name, key, value string) error
+}
+
+type kdsClient interface {
+	CertChain(signingType abi.ReportSigner) (ask, ark *x509.Certificate, err error)
+}
--- a/joinservice/internal/certcache/certcache_test.go
+++ b/joinservice/internal/certcache/certcache_test.go
@ -0,0 +1,247 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package certcache
+
+import (
+	"context"
+	"crypto/x509"
+	"testing"
+
+	"github.com/edgelesssys/constellation/v2/internal/attestation/variant"
+	"github.com/edgelesssys/constellation/v2/internal/constants"
+	"github.com/edgelesssys/constellation/v2/internal/crypto"
+	"github.com/edgelesssys/constellation/v2/internal/logger"
+	"github.com/edgelesssys/constellation/v2/joinservice/internal/certcache/testdata"
+	"github.com/google/go-sev-guest/abi"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	k8serrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+)
+
+func TestCreateCertChainCache(t *testing.T) {
+	notFoundErr := k8serrors.NewNotFound(schema.GroupResource{}, "test")
+
+	testCases := map[string]struct {
+		kubeClient  *stubKubeClient
+		kdsClient   *stubKdsClient
+		expectedArk *x509.Certificate
+		expectedAsk *x509.Certificate
+		wantErr     bool
+	}{
+		"available in configmap": {
+			kubeClient: &stubKubeClient{
+				askResponse: string(testdata.Ask),
+				arkResponse: string(testdata.Ark),
+			},
+			kdsClient:   &stubKdsClient{},
+			expectedArk: mustParsePEM(testdata.Ark),
+			expectedAsk: mustParsePEM(testdata.Ask),
+		},
+		"query from kds": {
+			kubeClient: &stubKubeClient{
+				getConfigMapDataErr: notFoundErr,
+			},
+			kdsClient: &stubKdsClient{
+				askResponse: testdata.Ask,
+				arkResponse: testdata.Ark,
+			},
+			expectedArk: mustParsePEM(testdata.Ark),
+			expectedAsk: mustParsePEM(testdata.Ask),
+		},
+		"only replace uncached cert": {
+			kubeClient: &stubKubeClient{
+				askResponse: string(testdata.Ark), // on purpose
+			},
+			kdsClient: &stubKdsClient{
+				arkResponse: testdata.Ark,
+				askResponse: testdata.Ask,
+			},
+			expectedArk: mustParsePEM(testdata.Ark),
+			expectedAsk: mustParsePEM(testdata.Ark), // on purpose
+		},
+		"only ask available in configmap": {
+			kubeClient: &stubKubeClient{
+				askResponse: string(testdata.Ask),
+			},
+			kdsClient: &stubKdsClient{
+				arkResponse: testdata.Ark,
+			},
+			expectedArk: mustParsePEM(testdata.Ark),
+			expectedAsk: mustParsePEM(testdata.Ask),
+		},
+		"only ark available in configmap": {
+			kubeClient: &stubKubeClient{
+				arkResponse: string(testdata.Ark),
+			},
+			kdsClient: &stubKdsClient{
+				askResponse: testdata.Ask,
+			},
+			expectedArk: mustParsePEM(testdata.Ark),
+			expectedAsk: mustParsePEM(testdata.Ask),
+		},
+		"get config map data err": {
+			kubeClient: &stubKubeClient{
+				getConfigMapDataErr: assert.AnError,
+			},
+			wantErr: true,
+		},
+		"update configmap err": {
+			kubeClient: &stubKubeClient{
+				askResponse:        string(testdata.Ask),
+				updateConfigMapErr: assert.AnError,
+			},
+			kdsClient: &stubKdsClient{
+				arkResponse: testdata.Ark,
+			},
+			wantErr: true,
+		},
+		"kds cert chain err": {
+			kubeClient: &stubKubeClient{
+				getConfigMapDataErr: notFoundErr,
+			},
+			kdsClient: &stubKdsClient{
+				certChainErr: assert.AnError,
+			},
+			wantErr: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			ctx := context.Background()
+
+			c := &Client{
+				attVariant: variant.Dummy{},
+				log:        logger.NewTest(t),
+				kubeClient: tc.kubeClient,
+				kdsClient:  tc.kdsClient,
+			}
+
+			ask, ark, err := c.createCertChainCache(ctx, abi.NoneReportSigner)
+			if tc.wantErr {
+				assert.Error(err)
+			} else {
+				require.NoError(err)
+				assert.Equal(tc.expectedArk, ark)
+				assert.Equal(tc.expectedAsk, ask)
+			}
+		})
+	}
+}
+
+type stubKdsClient struct {
+	askResponse  []byte
+	arkResponse  []byte
+	certChainErr error
+}
+
+func (c *stubKdsClient) CertChain(abi.ReportSigner) (ask, ark *x509.Certificate, err error) {
+	if c.askResponse != nil {
+		ask = mustParsePEM(c.askResponse)
+	}
+	if c.arkResponse != nil {
+		ark = mustParsePEM(c.arkResponse)
+	}
+	return ask, ark, c.certChainErr
+}
+
+func mustParsePEM(pemBytes []byte) *x509.Certificate {
+	cert, err := crypto.PemToX509Cert(pemBytes)
+	if err != nil {
+		panic(err)
+	}
+	return cert
+}
+
+func TestGetCertChainCache(t *testing.T) {
+	testCases := map[string]struct {
+		kubeClient  *stubKubeClient
+		expectedAsk *x509.Certificate
+		expectedArk *x509.Certificate
+		wantErr     bool
+	}{
+		"success": {
+			kubeClient: &stubKubeClient{
+				askResponse: string(testdata.Ask),
+				arkResponse: string(testdata.Ark),
+			},
+			expectedAsk: mustParsePEM(testdata.Ask),
+			expectedArk: mustParsePEM(testdata.Ark),
+		},
+		"empty ask": {
+			kubeClient: &stubKubeClient{
+				askResponse: "",
+				arkResponse: string(testdata.Ark),
+			},
+			expectedAsk: nil,
+			expectedArk: mustParsePEM(testdata.Ark),
+		},
+		"empty ark": {
+			kubeClient: &stubKubeClient{
+				askResponse: string(testdata.Ask),
+				arkResponse: "",
+			},
+			expectedAsk: mustParsePEM(testdata.Ask),
+			expectedArk: nil,
+		},
+		"error getting config map data": {
+			kubeClient: &stubKubeClient{
+				getConfigMapDataErr: assert.AnError,
+			},
+			wantErr: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
+
+			ctx := context.Background()
+
+			c := NewClient(logger.NewTest(t), tc.kubeClient, variant.Dummy{})
+
+			ask, ark, err := c.getCertChainCache(ctx)
+			if tc.wantErr {
+				assert.Error(err)
+			} else {
+				assert.NoError(err)
+				assert.Equal(tc.expectedArk, ark)
+				assert.Equal(tc.expectedAsk, ask)
+			}
+		})
+	}
+}
+
+type stubKubeClient struct {
+	askResponse         string
+	arkResponse         string
+	createConfigMapErr  error
+	updateConfigMapErr  error
+	getConfigMapDataErr error
+}
+
+func (s *stubKubeClient) CreateConfigMap(context.Context, string, map[string]string) error {
+	return s.createConfigMapErr
+}
+
+func (s *stubKubeClient) GetConfigMapData(_ context.Context, _ string, key string) (string, error) {
+	if key == constants.CertCacheAskKey {
+		return s.askResponse, s.getConfigMapDataErr
+	}
+	if key == constants.CertCacheArkKey {
+		return s.arkResponse, s.getConfigMapDataErr
+	}
+	return "", s.getConfigMapDataErr
+}
+
+func (s *stubKubeClient) UpdateConfigMap(context.Context, string, string, string) error {
+	return s.updateConfigMapErr
+}
--- a/joinservice/internal/certcache/testdata/BUILD.bazel
+++ b/joinservice/internal/certcache/testdata/BUILD.bazel
@ -0,0 +1,12 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "testdata",
+    srcs = ["testdata.go"],
+    embedsrcs = [
+        "ark.pem",
+        "ask.pem",
+    ],
+    importpath = "github.com/edgelesssys/constellation/v2/joinservice/internal/certcache/testdata",
+    visibility = ["//joinservice:__subpackages__"],
+)
--- a/joinservice/internal/certcache/testdata/ark.pem
+++ b/joinservice/internal/certcache/testdata/ark.pem
@ -0,0 +1,37 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
--- a/joinservice/internal/certcache/testdata/ask.pem
+++ b/joinservice/internal/certcache/testdata/ask.pem
@ -0,0 +1,37 @@
+-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
--- a/joinservice/internal/certcache/testdata/testdata.go
+++ b/joinservice/internal/certcache/testdata/testdata.go
@ -0,0 +1,20 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+// Package testdata contains testing data for an attestation process.
+package testdata
+
+import _ "embed"
+
+// Ark is a valid ARK certificate, as returned from the AMD KDS.
+//
+//go:embed ark.pem
+var Ark []byte
+
+// Ask is a valid ASK certificate, as returned from the AMD KDS.
+//
+//go:embed ask.pem
+var Ask []byte
--- a/joinservice/internal/kubernetes/BUILD.bazel
+++ b/joinservice/internal/kubernetes/BUILD.bazel
@ -9,6 +9,7 @@ go_library(
    deps = [
        "//internal/constants",
        "//internal/versions/components",
+        "@io_k8s_api//core/v1:core",
        "@io_k8s_apimachinery//pkg/apis/meta/v1:meta",
        "@io_k8s_apimachinery//pkg/apis/meta/v1/unstructured",
        "@io_k8s_apimachinery//pkg/runtime/schema",
--- a/joinservice/internal/kubernetes/kubernetes.go
+++ b/joinservice/internal/kubernetes/kubernetes.go
@ -17,6 +17,7 @@ import (

 	"github.com/edgelesssys/constellation/v2/internal/constants"
 	"github.com/edgelesssys/constellation/v2/internal/versions/components"
+	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime/schema"
@ -54,7 +55,7 @@ func New() (*Client, error) {

 // GetComponents returns the components of the cluster.
 func (c *Client) GetComponents(ctx context.Context, configMapName string) (components.Components, error) {
-	componentsRaw, err := c.getConfigMapData(ctx, configMapName, constants.ComponentsListKey)
+	componentsRaw, err := c.GetConfigMapData(ctx, configMapName, constants.ComponentsListKey)
 	if err != nil {
 		return components.Components{}, fmt.Errorf("failed to get components: %w", err)
 	}
@ -65,8 +66,9 @@ func (c *Client) GetComponents(ctx context.Context, configMapName string) (compo
 	return clusterComponents, nil
 }

-func (c *Client) getConfigMapData(ctx context.Context, name, key string) (string, error) {
-	cm, err := c.client.CoreV1().ConfigMaps("kube-system").Get(ctx, name, metav1.GetOptions{})
+// GetConfigMapData returns the data for the given key in the configmap with the given name.
+func (c *Client) GetConfigMapData(ctx context.Context, name, key string) (string, error) {
+	cm, err := c.client.CoreV1().ConfigMaps(constants.ConstellationNamespace).Get(ctx, name, metav1.GetOptions{})
 	if err != nil {
 		return "", fmt.Errorf("failed to get configmap: %w", err)
 	}
@ -159,3 +161,37 @@ func k8sCompliantHostname(in string) (string, error) {
 	}
 	return hostname, nil
 }
+
+// CreateConfigMap creates a configmap in the kube-system namespace with the provided name and data.
+func (c *Client) CreateConfigMap(ctx context.Context, name string, data map[string]string) error {
+	cm := &corev1.ConfigMap{
+		TypeMeta: metav1.TypeMeta{
+			Kind:       "ConfigMap",
+			APIVersion: "v1",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      name,
+			Namespace: constants.ConstellationNamespace,
+		},
+		Data: data,
+	}
+	_, err := c.client.CoreV1().ConfigMaps(constants.ConstellationNamespace).Create(ctx, cm, metav1.CreateOptions{})
+	if err != nil {
+		return fmt.Errorf("failed to create configmap: %w", err)
+	}
+	return nil
+}
+
+// UpdateConfigMap updates the configmap with the provided name by writing the provided key and value.
+func (c *Client) UpdateConfigMap(ctx context.Context, name, key, value string) error {
+	cm, err := c.client.CoreV1().ConfigMaps(constants.ConstellationNamespace).Get(ctx, name, metav1.GetOptions{})
+	if err != nil {
+		return fmt.Errorf("failed to get configmap: %w", err)
+	}
+	cm.Data[key] = value
+	_, err = c.client.CoreV1().ConfigMaps(constants.ConstellationNamespace).Update(ctx, cm, metav1.UpdateOptions{})
+	if err != nil {
+		return fmt.Errorf("failed to update configmap: %w", err)
+	}
+	return nil
+}
--- a/joinservice/internal/server/BUILD.bazel
+++ b/joinservice/internal/server/BUILD.bazel
@ -13,7 +13,6 @@ go_library(
        "//internal/grpc/grpclog",
        "//internal/logger",
        "//internal/versions/components",
-        "//joinservice/internal/kubernetes",
        "//joinservice/joinproto",
        "@io_k8s_kubernetes//cmd/kubeadm/app/apis/kubeadm/v1beta3",
        "@org_golang_google_grpc//:go_default_library",
--- a/joinservice/internal/server/server.go
+++ b/joinservice/internal/server/server.go
@ -19,7 +19,6 @@ import (
 	"github.com/edgelesssys/constellation/v2/internal/grpc/grpclog"
 	"github.com/edgelesssys/constellation/v2/internal/logger"
 	"github.com/edgelesssys/constellation/v2/internal/versions/components"
-	"github.com/edgelesssys/constellation/v2/joinservice/internal/kubernetes"
 	"github.com/edgelesssys/constellation/v2/joinservice/joinproto"
 	"go.uber.org/zap"
 	"google.golang.org/grpc"
@ -45,12 +44,8 @@ type Server struct {
 // New initializes a new Server.
 func New(
 	measurementSalt []byte, ca certificateAuthority,
-	joinTokenGetter joinTokenGetter, dataKeyGetter dataKeyGetter, log *logger.Logger,
+	joinTokenGetter joinTokenGetter, dataKeyGetter dataKeyGetter, kubeClient kubeClient, log *logger.Logger,
 ) (*Server, error) {
-	kubeClient, err := kubernetes.New()
-	if err != nil {
-		return nil, fmt.Errorf("failed to create kubernetes client: %w", err)
-	}
 	return &Server{
 		measurementSalt: measurementSalt,
 		log:             log,
--- a/joinservice/internal/watcher/validator.go
+++ b/joinservice/internal/watcher/validator.go
@ -8,6 +8,7 @@ package watcher

 import (
 	"context"
+	"crypto/x509"
 	"encoding/asn1"
 	"fmt"
 	"path/filepath"
@ -28,21 +29,25 @@ type Updatable struct {
 	mux         sync.Mutex
 	fileHandler file.Handler
 	variant     variant.Variant
+	cachedCerts cachedCerts
 	atls.Validator
 }

-// NewValidator initializes a new updatable validator.
-func NewValidator(log *logger.Logger, variant variant.Variant, fileHandler file.Handler) (*Updatable, error) {
+// NewValidator initializes a new updatable validator and performs an initial update (aka. initialization).
+func NewValidator(log *logger.Logger, variant variant.Variant, fileHandler file.Handler, cachedCerts cachedCerts) (*Updatable, error) {
 	u := &Updatable{
 		log:         log,
 		fileHandler: fileHandler,
 		variant:     variant,
+		cachedCerts: cachedCerts,
+	}
+	err := u.Update()
+
+	return u, err
 }

-	if err := u.Update(); err != nil {
-		return nil, err
-	}
-	return u, nil
+type cachedCerts interface {
+	SevSnpCerts() (ask *x509.Certificate, ark *x509.Certificate)
 }

 // Validate calls the validators Validate method, and prevents any updates during the call.
@ -76,11 +81,44 @@ func (u *Updatable) Update() error {
 	}
 	u.log.Debugf("New expected measurements: %+v", cfg.GetMeasurements())

-	validator, err := choose.Validator(cfg, u.log)
+	cfgWithCerts, err := u.configWithCerts(cfg)
 	if err != nil {
-		return fmt.Errorf("updating validator: %w", err)
+		return fmt.Errorf("adding cached certificates: %w", err)
+	}
+
+	validator, err := choose.Validator(cfgWithCerts, u.log)
+	if err != nil {
+		return fmt.Errorf("choosing validator: %w", err)
 	}
 	u.Validator = validator

 	return nil
 }
+
+// addCachedCerts adds the certificates cached by the validator to the attestation config, if applicable.
+func (u *Updatable) configWithCerts(cfg config.AttestationCfg) (config.AttestationCfg, error) {
+	switch c := cfg.(type) {
+	case *config.AzureSEVSNP:
+		ask, err := u.getCachedAskCert()
+		if err != nil {
+			return nil, fmt.Errorf("getting cached ASK certificate: %w", err)
+		}
+		c.AMDSigningKey = config.Certificate(ask)
+		return c, nil
+	}
+	// TODO(derpsteb): Add AWS SEV-SNP
+
+	return cfg, nil
+}
+
+// getCachedAskCert returns the cached SEV-SNP ASK certificate.
+func (u *Updatable) getCachedAskCert() (x509.Certificate, error) {
+	if u.cachedCerts == nil {
+		return x509.Certificate{}, fmt.Errorf("no cached certs available")
+	}
+	ask, _ := u.cachedCerts.SevSnpCerts()
+	if ask == nil {
+		return x509.Certificate{}, fmt.Errorf("no ASK available")
+	}
+	return *ask, nil
+}
--- a/joinservice/internal/watcher/validator_test.go
+++ b/joinservice/internal/watcher/validator_test.go
@ -8,6 +8,7 @@ package watcher

 import (
 	"context"
+	"crypto/x509"
 	"encoding/asn1"
 	"encoding/json"
 	"io"
@ -41,11 +42,16 @@ func TestNewUpdateableValidator(t *testing.T) {
 	testCases := map[string]struct {
 		variant  variant.Variant
 		config   config.AttestationCfg
+		snpCerts *stubSnpCerts
 		wantErr  bool
 	}{
 		"azure": {
 			variant: variant.AzureSEVSNP{},
 			config:  config.DefaultForAzureSEVSNP(),
+			snpCerts: &stubSnpCerts{
+				ask: &x509.Certificate{},
+				ark: &x509.Certificate{},
+			},
 		},
 		"gcp": {
 			variant: variant.GCPSEVES{},
@ -83,6 +89,7 @@ func TestNewUpdateableValidator(t *testing.T) {
 				logger.NewTest(t),
 				tc.variant,
 				handler,
+				tc.snpCerts,
 			)
 			if tc.wantErr {
 				assert.Error(err)
@ -93,6 +100,15 @@ func TestNewUpdateableValidator(t *testing.T) {
 	}
 }

+type stubSnpCerts struct {
+	ask *x509.Certificate
+	ark *x509.Certificate
+}
+
+func (s *stubSnpCerts) SevSnpCerts() (ask *x509.Certificate, ark *x509.Certificate) {
+	return s.ask, s.ark
+}
+
 func TestUpdate(t *testing.T) {
 	assert := assert.New(t)
 	require := require.New(t)