internal: refactor oid package to variant package (#1538)

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

internal/variant/variant.go

@@ -0,0 +1,185 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+/*
+Package variant defines Attestation variants for different CSPs.
+
+Each variant defines an OID, a string representation, and a function to compare it to other OIDs.
+
+The OID is used in attested TLS to distinguish the attestation documents.
+OIDs beginning with 1.3.9900 are reserved and can be used without registration.
+
+* The 1.3.9900.1 branch is reserved for placeholder values and testing.
+
+* The 1.3.9900.2 branch is reserved for AWS.
+
+* The 1.3.9900.3 branch is reserved for GCP.
+
+* The 1.3.9900.4 branch is reserved for Azure.
+
+* The 1.3.9900.5 branch is reserved for QEMU.
+
+Deprecated OIDs should never be reused for different purposes.
+Instead, new OIDs should be added in the appropriate branch at the next available index.
+
+String representation should be lowercase and contain only letters, numbers, and hyphens.
+They should be prefixed with the branch name, e.g. all variants in the 1.3.9900.2 (AWS) branch should start with "aws-".
+Each variant should have a unique string representation.
+*/
+package variant
+
+import (
+	"encoding/asn1"
+	"fmt"
+)
+
+const (
+	dummy              = "dummy"
+	awsNitroTPM        = "aws-nitro-tpm"
+	gcpSEVES           = "gcp-sev-es"
+	azureSEVSNP        = "azure-sev-snp"
+	azureTrustedLaunch = "azure-trustedlaunch"
+	qemuVTPM           = "qemu-vtpm"
+)
+
+// Getter returns an ASN.1 Object Identifier.
+type Getter interface {
+	OID() asn1.ObjectIdentifier
+}
+
+// Variant describes an attestation variant.
+type Variant interface {
+	Getter
+	String() string
+	Equal(other Getter) bool
+}
+
+// FromString returns the OID for the given string.
+func FromString(oid string) (Variant, error) {
+	switch oid {
+	case dummy:
+		return Dummy{}, nil
+	case awsNitroTPM:
+		return AWSNitroTPM{}, nil
+	case gcpSEVES:
+		return GCPSEVES{}, nil
+	case azureSEVSNP:
+		return AzureSEVSNP{}, nil
+	case azureTrustedLaunch:
+		return AzureTrustedLaunch{}, nil
+	case qemuVTPM:
+		return QEMUVTPM{}, nil
+	}
+	return nil, fmt.Errorf("unknown OID: %q", oid)
+}
+
+// Dummy OID for testing.
+type Dummy struct{}
+
+// OID returns the struct's object identifier.
+func (Dummy) OID() asn1.ObjectIdentifier {
+	return asn1.ObjectIdentifier{1, 3, 9900, 1, 1}
+}
+
+// String returns the string representation of the OID.
+func (Dummy) String() string {
+	return dummy
+}
+
+// Equal returns true if the other variant is also a Dummy.
+func (Dummy) Equal(other Getter) bool {
+	return other.OID().Equal(Dummy{}.OID())
+}
+
+// AWSNitroTPM holds the AWS nitro TPM OID.
+type AWSNitroTPM struct{}
+
+// OID returns the struct's object identifier.
+func (AWSNitroTPM) OID() asn1.ObjectIdentifier {
+	return asn1.ObjectIdentifier{1, 3, 9900, 2, 1}
+}
+
+// String returns the string representation of the OID.
+func (AWSNitroTPM) String() string {
+	return awsNitroTPM
+}
+
+// Equal returns true if the other variant is also AWSNitroTPM.
+func (AWSNitroTPM) Equal(other Getter) bool {
+	return other.OID().Equal(AWSNitroTPM{}.OID())
+}
+
+// GCPSEVES holds the GCP SEV-ES OID.
+type GCPSEVES struct{}
+
+// OID returns the struct's object identifier.
+func (GCPSEVES) OID() asn1.ObjectIdentifier {
+	return asn1.ObjectIdentifier{1, 3, 9900, 3, 1}
+}
+
+// String returns the string representation of the OID.
+func (GCPSEVES) String() string {
+	return gcpSEVES
+}
+
+// Equal returns true if the other variant is also GCPSEVES.
+func (GCPSEVES) Equal(other Getter) bool {
+	return other.OID().Equal(GCPSEVES{}.OID())
+}
+
+// AzureSEVSNP holds the OID for Azure SNP CVMs.
+type AzureSEVSNP struct{}
+
+// OID returns the struct's object identifier.
+func (AzureSEVSNP) OID() asn1.ObjectIdentifier {
+	return asn1.ObjectIdentifier{1, 3, 9900, 4, 1}
+}
+
+// String returns the string representation of the OID.
+func (AzureSEVSNP) String() string {
+	return azureSEVSNP
+}
+
+// Equal returns true if the other variant is also AzureSEVSNP.
+func (AzureSEVSNP) Equal(other Getter) bool {
+	return other.OID().Equal(AzureSEVSNP{}.OID())
+}
+
+// AzureTrustedLaunch holds the OID for Azure TrustedLaunch VMs.
+type AzureTrustedLaunch struct{}
+
+// OID returns the struct's object identifier.
+func (AzureTrustedLaunch) OID() asn1.ObjectIdentifier {
+	return asn1.ObjectIdentifier{1, 3, 9900, 4, 2}
+}
+
+// String returns the string representation of the OID.
+func (AzureTrustedLaunch) String() string {
+	return azureTrustedLaunch
+}
+
+// Equal returns true if the other variant is also AzureTrustedLaunch.
+func (AzureTrustedLaunch) Equal(other Getter) bool {
+	return other.OID().Equal(AzureTrustedLaunch{}.OID())
+}
+
+// QEMUVTPM holds the QEMUVTPM OID.
+type QEMUVTPM struct{}
+
+// OID returns the struct's object identifier.
+func (QEMUVTPM) OID() asn1.ObjectIdentifier {
+	return asn1.ObjectIdentifier{1, 3, 9900, 5, 1}
+}
+
+// String returns the string representation of the OID.
+func (QEMUVTPM) String() string {
+	return qemuVTPM
+}
+
+// Equal returns true if the other variant is also QEMUVTPM.
+func (QEMUVTPM) Equal(other Getter) bool {
+	return other.OID().Equal(QEMUVTPM{}.OID())
+}