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avr.go
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avr.go
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// Package ias provides routines for interacting with the Intel Attestation
// Service.
package ias
import (
"crypto/x509"
"encoding/base64"
"encoding/hex"
"encoding/json"
"fmt"
"net/url"
"time"
"github.com/oasisprotocol/oasis-core/go/common/sgx"
)
// NonceMaxLen is the maximum length of the AVR nonce.
const NonceMaxLen = 32
// requiredAVRVersion is the required AV report version.
const requiredAVRVersion = 4
var (
unsafeSkipVerify bool
unsafeAllowDebugEnclaves bool
)
// TimestampFormat is the format of the AVR timestamp, suitable for use with
// time.Parse.
//
// Workaround for https://github.com/golang/go/issues/21990
const TimestampFormat = "2006-01-02T15:04:05.999999999"
var (
isvQuoteFwdMap = map[string]ISVEnclaveQuoteStatus{
"OK": QuoteOK,
"SIGNATURE_INVALID": QuoteSignatureInvalid,
"GROUP_REVOKED": QuoteGroupRevoked,
"SIGNATURE_REVOKED": QuoteSignatureRevoked,
"KEY_REVOKED": QuoteKeyRevoked,
"SIGRL_VERSION_MISMATCH": QuoteSigRLVersionMismatch,
"GROUP_OUT_OF_DATE": QuoteGroupOutOfDate,
"CONFIGURATION_NEEDED": QuoteConfigurationNeeded,
"SW_HARDENING_NEEDED": QuoteSwHardeningNeeded,
"CONFIGURATION_AND_SW_HARDENING_NEEDED": QuoteConfigurationAndSwHardeningNeeded,
}
isvQuoteRevMap = make(map[ISVEnclaveQuoteStatus]string)
pseManifFwdMap = map[string]PSEManifestStatus{
"OK": ManifestOK,
"UNKNOWN": ManifestUnknown,
"INVALID": ManifestInvalid,
"OUT_OF_DATE": ManifestOutOfDate,
"REVOKED": ManifestRevoked,
"RL_VERSION_MISMATCH": ManifestRLVersionMismatch,
}
pseManifRevMap = make(map[PSEManifestStatus]string)
crlReasonRevMap = map[CRLReason]string{
ReasonUnspecified: "unspecified",
ReasonKeyCompromise: "keyCompromise",
ReasonCACompromise: "cACompromise",
ReasonAffiliationChanged: "affiliationChanged",
ReasonSuperseded: "superseded",
ReasonCessationOfOperation: "cessationOfOperation",
ReasonCertificateHold: "certificateHold",
ReasonRemoveFromCRL: "removeFromCRL",
ReasonPrivilegeWithdrawn: "privilegeWithdrawn",
ReasonAACompromise: "aACompromise",
}
mrSignerBlacklist = make(map[sgx.MrSigner]bool)
)
// ISVEnclaveQuoteStatus is the status of an enclave quote.
type ISVEnclaveQuoteStatus int
// Predefined ISV enclave quote status codes.
const (
quoteFieldMissing ISVEnclaveQuoteStatus = iota
QuoteOK
QuoteSignatureInvalid
QuoteGroupRevoked
QuoteSignatureRevoked
QuoteKeyRevoked
QuoteSigRLVersionMismatch
QuoteGroupOutOfDate
QuoteConfigurationNeeded
QuoteSwHardeningNeeded
QuoteConfigurationAndSwHardeningNeeded
)
// UnmarshalText implements the encoding.TextUnmarshaler interface.
func (s *ISVEnclaveQuoteStatus) UnmarshalText(text []byte) error {
var ok bool
*s, ok = isvQuoteFwdMap[string(text)]
if !ok {
return fmt.Errorf("ias/avr: invalid quote status: '%v'", string(text))
}
return nil
}
// MarshalText implements the encoding.TextMarshaler interface.
func (s *ISVEnclaveQuoteStatus) MarshalText() ([]byte, error) {
str, ok := isvQuoteRevMap[*s]
if !ok {
return nil, fmt.Errorf("ias/avr: invalid quote status: '%v'", int(*s))
}
return []byte(str), nil
}
func (s ISVEnclaveQuoteStatus) String() string {
return isvQuoteRevMap[s]
}
// PSEManifestStatus is the status of a SGX Platform Service Security
// Property Descriptor.
type PSEManifestStatus int
// Predefined SGX Platform Service Security Property Descriptor status codes.
const (
ManifestOK PSEManifestStatus = iota
ManifestUnknown
ManifestInvalid
ManifestOutOfDate
ManifestRevoked
ManifestRLVersionMismatch
)
// UnmarshalText implements the encoding.TextUnmarshaler interface.
func (p *PSEManifestStatus) UnmarshalText(text []byte) error {
var ok bool
*p, ok = pseManifFwdMap[string(text)]
if !ok {
return fmt.Errorf("ias/avr: invalid PSE manifest status: '%v'", string(text))
}
return nil
}
// MarshalText implements the encoding.TextMarshaler interface.
func (p *PSEManifestStatus) MarshalText() ([]byte, error) {
str, ok := pseManifRevMap[*p]
if !ok {
return nil, fmt.Errorf("ias/avr: invalid PSE manifest status: '%v'", int(*p))
}
return []byte(str), nil
}
func (p PSEManifestStatus) String() string {
return pseManifRevMap[p]
}
// CRLReason is a certificate revocation reason code as specified in RFC 5280
// 5.3.1.
type CRLReason int
// Predefined CRL revocation reason codes.
const (
ReasonUnspecified CRLReason = 0
ReasonKeyCompromise CRLReason = 1
ReasonCACompromise CRLReason = 2
ReasonAffiliationChanged CRLReason = 3
ReasonSuperseded CRLReason = 4
ReasonCessationOfOperation CRLReason = 5
ReasonCertificateHold CRLReason = 6
ReasonRemoveFromCRL CRLReason = 8
ReasonPrivilegeWithdrawn CRLReason = 9
ReasonAACompromise CRLReason = 10
)
func (r CRLReason) String() string {
s, ok := crlReasonRevMap[r]
if !ok {
return fmt.Sprintf("[unknown reason (%d)]", int(r))
}
return s
}
// AVRBundle is a serialized Attestation Verification Report bundled
// with additional data required to allow offline verification.
type AVRBundle struct {
Body []byte `json:"body"`
CertificateChain []byte `json:"certificate_chain"`
Signature []byte `json:"signature"`
}
// Open decodes and validates the AVR contained in the bundle, and returns
// the Attestation Verification Report iff it is valid
func (b *AVRBundle) Open(trustRoots *x509.CertPool, ts time.Time) (*AttestationVerificationReport, error) {
return DecodeAVR(b.Body, b.Signature, b.CertificateChain, trustRoots, ts)
}
// AttestationVerificationReport is a deserialized Attestation Verification
// Report (AVR).
type AttestationVerificationReport struct {
ID string `json:"id"`
Timestamp string `json:"timestamp"`
Version int `json:"version"`
ISVEnclaveQuoteStatus ISVEnclaveQuoteStatus `json:"isvEnclaveQuoteStatus"`
ISVEnclaveQuoteBody []byte `json:"isvEnclaveQuoteBody"`
RevocationReason *CRLReason `json:"revocationReason"`
PSEManifestStatus *PSEManifestStatus `json:"pseManifestStatus"`
PSEManifestHash string `json:"pseManifestHash"`
PlatformInfoBlob string `json:"platformInfoBlob"`
Nonce string `json:"nonce"`
EPIDPseudonym []byte `json:"epidPseudonym"`
AdvisoryURL string `json:"advisoryURL"`
AdvisoryIDs []string `json:"advisoryIDs"`
}
// Quote decodes and returns the enclave quote component of an Attestation
// Verification Report.
func (a *AttestationVerificationReport) Quote() (*Quote, error) {
var quote Quote
if err := quote.UnmarshalBinary(a.ISVEnclaveQuoteBody); err != nil {
return nil, err
}
return "e, nil
}
func (a *AttestationVerificationReport) validate() error { // nolint: gocyclo
const (
pseManifestHashLen = 32
epidPseudonymLen = 64 + 64
)
if _, err := time.Parse(TimestampFormat, a.Timestamp); err != nil {
return fmt.Errorf("ias/avr: invalid timestamp: %w", err)
}
if a.Version != requiredAVRVersion {
return fmt.Errorf("ias/avr: invalid report version, got: %d, required: %d", a.Version, requiredAVRVersion)
}
if a.ISVEnclaveQuoteStatus == quoteFieldMissing {
return fmt.Errorf("ias/avr: missing isvEnclaveQuoteStatus")
}
switch len(a.ISVEnclaveQuoteBody) {
case 0:
case quoteLen:
untrustedQuote, err := a.Quote()
if err != nil {
return fmt.Errorf("ias/avr: malformed quote: %w", err)
}
if err = untrustedQuote.Verify(); err != nil {
return fmt.Errorf("ias/avr: invalid quote: %w", err)
}
default:
return fmt.Errorf("ias/avr: invalid isvEnclaveQuoteBody length")
}
if a.ISVEnclaveQuoteStatus == QuoteGroupRevoked {
if a.RevocationReason == nil {
return fmt.Errorf("ias/avr: missing revocationReason")
}
} else if a.RevocationReason != nil {
return fmt.Errorf("ias/avr: invalid isvEnclaveStatus for revocationReason")
}
if a.PSEManifestStatus != nil {
switch a.ISVEnclaveQuoteStatus {
case QuoteOK, QuoteGroupOutOfDate, QuoteConfigurationNeeded, QuoteSwHardeningNeeded, QuoteConfigurationAndSwHardeningNeeded:
default:
return fmt.Errorf("ias/avr: unexpected pseManifestStatus")
}
}
pseHash, err := hex.DecodeString(a.PSEManifestHash)
if err != nil {
return fmt.Errorf("ias/avr: failed to decode pseManifestHash: %w", err)
}
switch len(pseHash) {
case 0, pseManifestHashLen:
default:
return fmt.Errorf("ias/avr: invalid pseManifestHash length")
}
piBlob, err := hex.DecodeString(a.PlatformInfoBlob)
if err != nil {
return fmt.Errorf("ias/avr: failed to decode platformInfoBlob: %w", err)
}
if len(piBlob) > 0 {
var canHas bool
switch a.ISVEnclaveQuoteStatus {
case QuoteGroupRevoked, QuoteGroupOutOfDate, QuoteConfigurationNeeded, QuoteSwHardeningNeeded, QuoteConfigurationAndSwHardeningNeeded:
canHas = true
default:
}
if a.PSEManifestStatus != nil && !canHas { // "one of the following"
switch *a.PSEManifestStatus {
case ManifestOutOfDate, ManifestRevoked, ManifestRLVersionMismatch:
canHas = true
default:
}
}
if !canHas {
return fmt.Errorf("ias/avr: unexpected platformInfoBlob")
}
// Could validate the Platform Info Blob (4.2.4), but it's also
// described as "opaque".
}
if len(a.Nonce) > NonceMaxLen {
return fmt.Errorf("ias/avr: invalid nonce length")
}
switch len(a.EPIDPseudonym) {
case 0, epidPseudonymLen:
default:
return fmt.Errorf("ias/avr: invalid epidPseudonym length")
}
return nil
}
// DecodeAVR decodes and validates an Attestation Verification Report.
func DecodeAVR(data, encodedSignature, encodedCertChain []byte, trustRoots *x509.CertPool, ts time.Time) (*AttestationVerificationReport, error) {
if !unsafeSkipVerify {
if err := validateAVRSignature(data, encodedSignature, encodedCertChain, trustRoots, ts); err != nil {
return nil, err
}
}
// Set the ISVEnclaveQuoteStatus to a sentinel value so that it is
// possible to detect it being missing from the JSON.
a := &AttestationVerificationReport{
ISVEnclaveQuoteStatus: quoteFieldMissing,
}
if err := json.Unmarshal(data, a); err != nil {
return nil, fmt.Errorf("ias/avr: failed to parse JSON: %w", err)
}
if err := a.validate(); err != nil {
return nil, err
}
return a, nil
}
func validateAVRSignature(data, encodedSignature, encodedCertChain []byte, trustRoots *x509.CertPool, ts time.Time) error {
decoded, err := url.QueryUnescape(string(encodedCertChain))
if err != nil {
return fmt.Errorf("ias/avr: failed to decode certificate chain: %w", err)
}
pemCerts := []byte(decoded)
var certs []*x509.Certificate
for {
var cert *x509.Certificate
cert, pemCerts, err = CertFromPEM(pemCerts)
if err != nil {
return err
}
if cert == nil {
break
}
certs = append(certs, cert)
}
if len(certs) != 2 {
return fmt.Errorf("ias/avr: unexpected certificate chain length: %d", len(certs))
}
signingCert, rootCert := certs[0], certs[1]
certChains, err := signingCert.Verify(x509.VerifyOptions{
Roots: trustRoots,
CurrentTime: ts,
})
if err != nil {
return fmt.Errorf("ias/avr: failed to verify certificate chain: %w", err)
}
if !certRootsAChain(rootCert, certChains) {
return fmt.Errorf("ias/avr: unexpected root in certificate chain")
}
signature, err := base64.StdEncoding.DecodeString(string(encodedSignature))
if err != nil {
return fmt.Errorf("ias/avr: failed to decode signature: %w", err)
}
if err = signingCert.CheckSignature(x509.SHA256WithRSA, data, signature); err != nil {
return fmt.Errorf("ias/avr: failed to verify AVR signature: %w", err)
}
return nil
}
// SetSkipVerify will disable AVR signature verification for the remainder
// of the process' lifetime.
func SetSkipVerify() {
unsafeSkipVerify = true
}
// SetAllowDebugEnclave will enable running and communicating with enclaves
// with debug flag enabled in AVR for the remainder of the process' lifetime.
func SetAllowDebugEnclaves() {
unsafeAllowDebugEnclaves = true
}
// UnsetAllowDebugEnclave will disable running and communicating with enclaves
// with debug flag enabled in AVR for the remainder of the process' lifetime.
func UnsetAllowDebugEnclaves() {
unsafeAllowDebugEnclaves = false
}
// BuildMrSignerBlacklist builds the MRSIGNER blacklist.
func BuildMrSignerBlacklist(allowTestKeys bool) {
if !allowTestKeys {
for _, v := range []string{
sgx.FortanixDummyMrSigner.String(),
} {
var signer sgx.MrSigner
if err := signer.UnmarshalHex(v); err != nil {
panic("ias/avr: failed to decode MRSIGNER: " + v)
}
mrSignerBlacklist[signer] = true
}
}
}
func init() {
for k, v := range isvQuoteFwdMap {
isvQuoteRevMap[v] = k
}
for k, v := range pseManifFwdMap {
pseManifRevMap[v] = k
}
}