// TruncateAttestation cuts off a delegation chain at its "Program" subprincipal
// extension and replaces its prefix with the given key principal. It also
// returns the PrinExt that represents exactly the program hash.
func TruncateAttestation(kprin auth.Prin, a *Attestation) (auth.Says, auth.PrinExt, error) {
// This attestation must have a top-level delegation to a key. Return an
// authorization for this program rooted in the policy key. I don't like
// this, since it seems like it's much riskier, since this doesn't say
// anything about the context in which the program is running. Fortunately,
// local policy rules: if a peer won't accept this cert, then the other
// program will have to fall back on the longer attestation.
stmt, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
return auth.Says{}, auth.PrinExt{}, err
}
says, ok := stmt.(auth.Says)
if !ok {
return auth.Says{}, auth.PrinExt{}, fmt.Errorf("the serialized statement must be a says")
}
// Replace the message with one that uses the new principal, taking the last
// Program subprinicpal, and all its following elements. It should say:
// policyKey.Program(...)... says key(...) speaksfor
// policyKey.Program(...)..., signed policyKey.
sf, ok := says.Message.(auth.Speaksfor)
if !ok {
return auth.Says{}, auth.PrinExt{}, fmt.Errorf("the message in the statement must be a speaksfor")
}
delegator, ok := sf.Delegator.(auth.Prin)
if !ok {
return auth.Says{}, auth.PrinExt{}, fmt.Errorf("the delegator must be a principal")
}
var prog auth.PrinExt
found := false
for _, sprin := range delegator.Ext {
if !found && (sprin.Name == "Program") {
found = true
prog = sprin
}
if found {
kprin.Ext = append(kprin.Ext, sprin)
}
}
// TODO(tmroeder): make sure that the delegate is a key and is not, e.g.,
// the policy key.
truncSpeaksfor := auth.Speaksfor{
Delegate: sf.Delegate,
Delegator: kprin,
}
truncSays := auth.Says{
Speaker: kprin,
Time: says.Time,
Expiration: says.Expiration,
Message: truncSpeaksfor,
}
return truncSays, prog, nil
}
// RuleDebugString returns a debug string for the ith policy rule, if it exists.
func (g *DatalogGuard) RuleDebugString(i int) string {
if i < 0 || i >= len(g.db.Rules) {
return ""
}
rule := g.db.Rules[i]
r, err := auth.UnmarshalForm(rule)
if err != nil {
return ""
}
return r.ShortString()
}
// ReloadIfModified reads all persistent policy data from disk if the file
// timestamp is more recent than the last time it was read.
func (g *DatalogGuard) ReloadIfModified() error {
if g.Key == nil {
return nil
}
file, err := os.Open(g.Config.GetSignedRulesPath())
if err != nil {
return err
}
defer file.Close()
// before parsing, check the timestamp
info, err := file.Stat()
if err != nil {
return err
}
if !info.ModTime().After(g.modTime) {
return nil
}
serialized, err := ioutil.ReadAll(file)
if err != nil {
return err
}
var sdb SignedDatalogRules
if err := proto.Unmarshal(serialized, &sdb); err != nil {
return err
}
if ok, err := g.Key.Verify(sdb.SerializedRules, DatalogRulesSigningContext, sdb.Signature); !ok {
if err != nil {
return err
}
return newError("datalog rule signature did not verify")
}
var db DatalogRules
if err := proto.Unmarshal(sdb.SerializedRules, &db); err != nil {
return err
}
// Only clear the rules set, since g.assert already skips datalog rules that
// are already present in the engine.
g.db.Rules = nil
g.modTime = info.ModTime()
for _, rule := range db.Rules {
r, err := auth.UnmarshalForm(rule)
if err != nil {
return err
}
err = g.assert(r)
if err != nil {
return err
}
}
return nil
}
// AddEndorsements reads the SerializedEndorsements in an attestation and adds
// the ones that are predicates signed by the policy key.
func AddEndorsements(guard Guard, a *Attestation, v *Verifier) error {
// Before validating against the guard, check to see if there are any
// predicates endorsed by the policy key. This allows truncated principals
// to get the Tao CA to sign a statement of the form
// TrustedHash(ext.Program(...)).
for _, e := range a.SerializedEndorsements {
var ea Attestation
if err := proto.Unmarshal(e, &ea); err != nil {
return err
}
f, err := auth.UnmarshalForm(ea.SerializedStatement)
if err != nil {
return err
}
says, ok := f.(auth.Says)
if !ok {
return fmt.Errorf("a serialized endorsement must be an auth.Says")
}
// TODO(tmroeder): check that this endorsement hasn't expired.
pred, ok := says.Message.(auth.Pred)
if !ok {
return fmt.Errorf("the message in an endorsement must be a predicate")
}
signerPrin, err := auth.UnmarshalPrin(ea.Signer)
if err != nil {
return err
}
if !signerPrin.Identical(says.Speaker) {
return fmt.Errorf("the speaker of an endorsement must be the signer")
}
if !v.ToPrincipal().Identical(signerPrin) {
return fmt.Errorf("the signer of an endorsement must be the policy key")
}
if ok, err := v.Verify(ea.SerializedStatement, AttestationSigningContext, ea.Signature); (err != nil) || !ok {
return fmt.Errorf("the signature on an endorsement didn't pass verification")
}
return guard.AddRule(pred.String())
}
return nil
}
// Create a Program Public/Private key.
func CreateSigningKey(t tao.Tao) (*tao.Keys, []byte, error) {
self, err := t.GetTaoName()
k, err := tao.NewTemporaryKeys(tao.Signing)
if k == nil || err != nil {
return nil, nil, errors.New("Can't generate signing key")
}
publicString := strings.Replace(self.String(), "(", "", -1)
publicString = strings.Replace(publicString, ")", "", -1)
// publicString is now a canonicalized Tao Principal name
us := "US"
google := "Google"
details := tao.X509Details{
Country: &us,
Organization: &google,
CommonName: &publicString}
subjectname := tao.NewX509Name(&details)
derCert, err := k.SigningKey.CreateSelfSignedDER(subjectname)
if err != nil {
return nil, nil, errors.New("Can't self sign cert\n")
}
cert, err := x509.ParseCertificate(derCert)
if err != nil {
return nil, nil, err
}
// Construct statement: "ProgramKey (new key) speaksfor Principal Name"
// ToPrincipal retrieves key's Tao Principal Name.
k.Cert = cert
s := &auth.Speaksfor{
Delegate: k.SigningKey.ToPrincipal(),
Delegator: self}
if s == nil {
return nil, nil, errors.New("Can't produce speaksfor")
}
// Sign attestation statement
k.Delegation, err = t.Attest(&self, nil, nil, s)
if err != nil {
return nil, nil, err
}
_, _ = auth.UnmarshalForm(k.Delegation.SerializedStatement)
return k, derCert, nil
}
func NewMarshalledDatalogGuard(ser []byte) (*DatalogGuard, error) {
var db DatalogRules
if err := proto.Unmarshal(ser, &db); err != nil {
return nil, err
}
g := NewTemporaryDatalogGuard().(*DatalogGuard)
for _, rule := range db.Rules {
r, err := auth.UnmarshalForm(rule)
if err != nil {
return nil, err
}
err = g.assert(r)
if err != nil {
return nil, err
}
}
return g, nil
}
// Attest is the server stub for Tao.Attest.
func (server linuxHostTaoServerStub) Attest(r *RPCRequest, s *RPCResponse) error {
stmt, err := auth.UnmarshalForm(r.Data)
if err != nil {
return err
}
var issuer *auth.Prin
if r.Issuer != nil {
p, err := auth.UnmarshalPrin(r.Issuer)
if err != nil {
return err
}
issuer = &p
}
a, err := server.lh.Attest(server.child, issuer, r.Time, r.Expiration, stmt)
if err != nil {
return err
}
s.Data, err = proto.Marshal(a)
return err
}
func (g *DatalogGuard) findRule(f auth.Form) (string, int, error) {
rule, err := g.formToDatalogRule(f)
if err != nil {
return "", -1, err
}
for i, ser := range g.db.Rules {
f2, err := auth.UnmarshalForm(ser)
if err != nil {
continue
}
rule2, err := g.formToDatalogRule(f2)
if err != nil {
continue
}
if rule == rule2 {
return rule, i, nil
}
}
return rule, -1, nil
}
// RequestTruncatedAttestation connects to a CA instance, sends the attestation
// for an X.509 certificate, and gets back a truncated attestation with a new
// principal name based on the policy key.
func RequestTruncatedAttestation(network, addr string, keys *Keys, v *Verifier) (*Attestation, error) {
a, err := RequestAttestation(network, addr, keys, v)
if err != nil {
return nil, err
}
truncStmt, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
return nil, err
}
says, _, err := TruncateAttestation(v.ToPrincipal(), keys.Delegation)
if err != nil {
return nil, err
}
if !IdenticalDelegations(says, truncStmt) {
return nil, fmt.Errorf("the statement returned by the TaoCA was different than what we expected")
}
return a, nil
}
// EstablishCert contacts a CA to get a certificate signed by the policy key. It
// replaces the current delegation and cert on k with the new delegation and
// cert from the response.
func EstablishCert(network, addr string, k *tao.Keys, v *tao.Verifier) error {
na, err := tao.RequestAttestation(network, addr, k, v)
if err != nil {
return err
}
k.Delegation = na
pa, err := auth.UnmarshalForm(na.SerializedStatement)
if err != nil {
return err
}
// Parse the received statement.
var saysStatement *auth.Says
if ptr, ok := pa.(*auth.Says); ok {
saysStatement = ptr
} else if val, ok := pa.(auth.Says); ok {
saysStatement = &val
}
sf, ok := saysStatement.Message.(auth.Speaksfor)
if ok != true {
return errors.New("says doesn't have speaksfor message")
}
kprin, ok := sf.Delegate.(auth.Term)
if ok != true {
return errors.New("speaksfor message doesn't have Delegate")
}
newCert := auth.Bytes(kprin.(auth.Bytes))
cert, err := x509.ParseCertificate(newCert)
if err != nil {
return err
}
k.Cert["default"] = cert
return nil
}
// Reload requests the policy from the remote TaoCA and instantiates a
// new guard.
func (cg *CachedGuard) Reload() error {
switch cg.guardType {
case Datalog:
datalogGuard := NewDatalogGuard(cg.verifier)
db, err := RequestDatalogRules(cg.network, cg.address, cg.verifier)
if err != nil {
return err
}
datalogGuard.db = *db
for _, marshaledForm := range db.Rules {
f, _ := auth.UnmarshalForm(marshaledForm)
rule, _, err := datalogGuard.findRule(f)
if err != nil {
return err
}
datalogGuard.dl.Assert(rule)
}
cg.guard = datalogGuard
case ACLs: // TODO(cjpatton)
return errors.New("CacheGuard: ACL set reload not implemented")
}
cg.timeUpdated = time.Now().Unix()
return nil
}
// ValidSigner checks the signature on an attestation and, if so, returns the
// principal name for the signer.
func (a *Attestation) ValidSigner() (auth.Prin, error) {
signer := auth.NewPrin(*a.SignerType, a.SignerKey)
switch *a.SignerType {
case "tpm":
// The PCRs are contained in the Speaker of an auth.Says statement that
// makes up the a.SerializedStatement.
f, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
return auth.Prin{}, newError("tao: couldn't unmarshal the statement: %s", err)
}
// A TPM attestation must be an auth.Says.
says, ok := f.(auth.Says)
if !ok {
return auth.Prin{}, newError("tao: the attestation statement was not an auth.Says statement")
}
// Signer is tpm; use tpm-specific signature verification. Extract the
// PCRs from the issuer name, unmarshal the key as an RSA key, and call
// tpm.VerifyQuote().
speaker, ok := says.Speaker.(auth.Prin)
if !ok {
return auth.Prin{}, newError("tao: the speaker of an attestation must be an auth.Prin")
}
pcrNums, pcrVals, err := extractPCRs(speaker)
if err != nil {
return auth.Prin{}, newError("tao: couldn't extract TPM PCRs from attestation: %s", err)
}
pk, err := extractTPMKey(a.SignerKey)
if err != nil {
return auth.Prin{}, newError("tao: couldn't extract TPM key from attestation: %s", err)
}
if err := tpm.VerifyQuote(pk, a.SerializedStatement, a.Signature, pcrNums, pcrVals); err != nil {
return auth.Prin{}, newError("tao: TPM quote failed verification: %s", err)
}
return signer, nil
case "tpm2":
// TODO -- tpm2
// The PCRs are contained in the Speaker of an auth.Says statement that
// makes up the a.SerializedStatement.
f, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
return auth.Prin{}, newError("tao: couldn't unmarshal the statement: %s", err)
}
// put this back in
// A TPM attestation must be an auth.Says.
says, ok := f.(auth.Says)
if !ok {
return auth.Prin{}, newError("tao: the attestation statement was not an auth.Says statement")
}
// Signer is tpm; use tpm-specific signature verification. Extract the
// PCRs from the issuer name, unmarshal the key as an RSA key, and call
// tpm2.VerifyQuote().
speaker, ok := says.Speaker.(auth.Prin)
if !ok {
return auth.Prin{}, newError("tao: the speaker of an attestation must be an auth.Prin")
}
key, err := extractTPM2Key(a.SignerKey)
if err != nil {
return auth.Prin{}, newError("tao: couldn't extract TPM key from attestation: %s", err)
}
pcrNums, pcrVal, err := extractTpm2PCRs(speaker)
if err != nil {
return auth.Prin{}, newError("tao: couldn't extract TPM PCRs from attestation: %s", err)
}
ok, err = tpm2.VerifyTpm2Quote(a.SerializedStatement,
pcrNums, pcrVal, a.Tpm2QuoteStructure, a.Signature,
key)
if err != nil {
return auth.Prin{}, newError("tao: TPM quote verification error")
}
if !ok {
return auth.Prin{}, newError("tao: TPM quote failed verification")
}
return signer, nil
case "key":
// Signer is ECDSA key, use Tao signature verification.
v, err := UnmarshalKey(a.SignerKey)
if err != nil {
return auth.Prin{}, err
}
ok, err := v.Verify(a.SerializedStatement, AttestationSigningContext, a.Signature)
if err != nil {
return auth.Prin{}, err
}
if !ok {
return auth.Prin{}, newError("tao: attestation signature invalid")
}
return signer, nil
default:
return auth.Prin{}, newError("tao: attestation signer principal unrecognized: %s", signer.String())
}
}
// First return is terminate flag.
func DomainRequest(conn net.Conn, policyKey *tao.Keys, guard tao.Guard) (bool, error) {
fmt.Printf("DomainRequest\n")
log.Printf("DomainRequest\n")
// Expect a request with attestation from client.
ms := util.NewMessageStream(conn)
var request domain_policy.DomainCertRequest
err := ms.ReadMessage(&request)
if err != nil {
log.Printf("DomainRequest: Couldn't read attestation from channel:", err)
log.Printf("\n")
return false, err
}
var a tao.Attestation
err = proto.Unmarshal(request.Attestation, &a)
if request.KeyType == nil {
log.Printf("Domain: Empty key type")
return false, errors.New("Empty key type")
}
if *request.KeyType != "ECDSA" {
log.Printf("Domain: bad key type")
return false, errors.New("Domain: bad key type")
}
subjectPublicKey, err := domain_policy.GetEcdsaKeyFromDer(request.SubjectPublicKey)
if err != nil {
log.Printf("DomainRequest: can't get key from der")
return false, errors.New("DomainRequest: can't get key from der")
}
// Get hash of the public key subject.
serializedKey, err := domain_policy.SerializeEcdsaKeyToInternalName(subjectPublicKey.(*ecdsa.PublicKey))
if err != nil || serializedKey == nil {
log.Printf("DomainRequest: Can't serialize key to internal format\n")
return false, errors.New("DomainRequest: Can't serialize key to internal format")
}
subjectKeyHash := domain_policy.GetKeyHash(serializedKey)
peerCert := conn.(*tls.Conn).ConnectionState().PeerCertificates[0]
err = tao.ValidatePeerAttestation(&a, peerCert, guard)
/*
if err != nil {
log.Printf("Domain: RequestCouldn't validate peer attestation:", err)
return false, err
}
fmt.Printf("DomainRequest, peerCert: %x\n", peerCert)
*/
// Sign cert
// Get Program name and key info from delegation.
f, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
log.Printf("DomainRequest: Can't unmarshal a.SerializedStatement\n")
return false, err
}
var saysStatement *auth.Says
if ptr, ok := f.(*auth.Says); ok {
saysStatement = ptr
} else if val, ok := f.(auth.Says); ok {
saysStatement = &val
}
sf, ok := saysStatement.Message.(auth.Speaksfor)
if ok != true {
log.Printf("DomainRequest: says doesnt have speaksfor message\n")
return false, err
}
// this in the new key principal
clientKeyPrincipal, ok := sf.Delegate.(auth.Prin)
if ok != true {
log.Printf("DomainRequest: speaksfor Delegate is not auth.Prin\n")
return false, err
}
programPrincipal, ok := sf.Delegator.(auth.Prin)
if ok != true {
log.Printf("DomainRequest: Can't get subject principal\n")
return false, errors.New("Can't get principal name from verifier")
}
programPrincipalName := programPrincipal.String()
verified := IsAuthenticationValid(&programPrincipalName)
if !verified {
log.Printf("DomainRequest: name verification failed\n")
return false, err
}
fmt.Printf("\nSimpleDomainService: key principal: %s, program principal: %s\n", clientKeyPrincipal, programPrincipalName)
// Is the delegate the same key as was presented in the name in the request?
namedHash := clientKeyPrincipal.KeyHash.(auth.Bytes)
fmt.Printf("\nkeyhash: %x\n", namedHash)
if bytes.Compare(subjectKeyHash[:], namedHash) != 0 {
log.Printf("DomainRequest: named hash is wrong\n")
fmt.Printf("DomainRequest: named hash is wrong, named: %x, computed: %x\n",
namedHash, subjectKeyHash)
return false, errors.New("DomainRequest: named hash is wrong")
}
// Sign program certificate.
notBefore := time.Now()
validFor := 365 * 24 * time.Hour
notAfter := notBefore.Add(validFor)
us := "US"
issuerName := "Google"
localhost := "localhost"
x509SubjectName := &pkix.Name{
Organization: []string{programPrincipalName},
OrganizationalUnit: []string{programPrincipalName},
CommonName: localhost,
Country: []string{us},
}
x509IssuerName := &pkix.Name{
Organization: []string{issuerName},
OrganizationalUnit: []string{issuerName},
CommonName: localhost,
Country: []string{us},
}
// issuerName := tao.NewX509Name(&details)
SerialNumber = SerialNumber + 1
var sn big.Int
certificateTemplate := x509.Certificate{
SerialNumber: &sn,
Issuer: *x509IssuerName,
Subject: *x509SubjectName,
NotBefore: notBefore,
NotAfter: notAfter,
KeyUsage: x509.KeyUsageCertSign |
x509.KeyUsageKeyAgreement | x509.KeyUsageDigitalSignature,
}
clientCert, err := x509.CreateCertificate(rand.Reader, &certificateTemplate,
policyKey.Cert, subjectPublicKey,
policyKey.SigningKey.GetSigner())
if err != nil {
fmt.Printf("Can't create client certificate: ", err, "\n")
return false, err
}
zero := int32(0)
var ra domain_policy.DomainCertResponse
ra.Error = &zero
ra.SignedCert = clientCert
// Add cert chain (just policy cert for now).
ra.CertChain = append(ra.CertChain, policyKey.Cert.Raw)
_, err = ms.WriteMessage(&ra)
if err != nil {
log.Printf("DomainRequest: Couldn't return the attestation on the channel: ", err)
log.Printf("\n")
return false, err
}
return false, nil
}
// First return is terminate flag.
func handleRequest(conn net.Conn, policyKey *tao.Keys, guard tao.Guard) error {
// Expect an attestation from the client.
ms := util.NewMessageStream(conn)
var a tao.Attestation
if err := ms.ReadMessage(&a); err != nil {
return err
}
peerCert := conn.(*tls.Conn).ConnectionState().PeerCertificates[0]
p, err := tao.ValidatePeerAttestation(&a, peerCert)
if err != nil {
return err
}
// TODO(kwalsh) most of this duplicates the work of tao.Conn
if !guard.IsAuthorized(p, "Execute", nil) {
return fmt.Errorf("peer is not authorized to execute, hence not authorized to connect either")
}
// Sign cert and put it in attestation statement
// a consists of serialized statement, sig and SignerInfo
// a is a says speaksfor, Delegate of speaksfor is cert and should be DER encoded
// Get underlying says
f, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
return err
}
var saysStatement *auth.Says
if ptr, ok := f.(*auth.Says); ok {
saysStatement = ptr
} else if val, ok := f.(auth.Says); ok {
saysStatement = &val
}
sf, ok := saysStatement.Message.(auth.Speaksfor)
if ok != true {
return fmt.Errorf("keynegoserver: says doesn't have a speaksfor message\n")
}
kprin, ok := sf.Delegate.(auth.Prin)
if ok != true {
return fmt.Errorf("keynegoserver: speaksfor Delegate is not auth.Prin\n")
}
subjectPrin, ok := sf.Delegator.(auth.Prin)
if ok != true {
return fmt.Errorf("keynegoserver: can't get subject principal\n")
}
subjectName := subjectPrin.String()
details := &tao.X509Details{
Country: proto.String("US"),
Organization: proto.String("Google"),
OrganizationalUnit: proto.String(subjectName),
CommonName: proto.String("localhost"),
}
subjectname := tao.NewX509Name(details)
SerialNumber = SerialNumber + 1
verifier, err := tao.FromPrincipal(kprin)
if err != nil {
return errors.New("can't get principal from kprin")
}
template := policyKey.SigningKey.X509Template(subjectname)
template.IsCA = false
clientCert, err := policyKey.CreateSignedX509(verifier, template, "default")
if err != nil {
return fmt.Errorf("keynegoserver: can't create client certificate: %s\n", err)
}
clientDERCert := clientCert.Raw
err = ioutil.WriteFile("ClientCert", clientDERCert, os.ModePerm)
nowTime := time.Now().UnixNano()
expireTime := time.Now().AddDate(1, 0, 0).UnixNano()
// Replace self signed cert in attest request
newSpeaksFor := &auth.Speaksfor{
Delegate: auth.Bytes(clientDERCert),
Delegator: sf.Delegator,
}
keyNegoSays := auth.Says{
Speaker: policyKey.SigningKey.ToPrincipal(),
Time: &nowTime,
Expiration: &expireTime,
Message: newSpeaksFor,
}
delegator, ok := sf.Delegator.(auth.Prin)
if !ok {
return fmt.Errorf("keynegoserver: the delegator must be a principal")
}
found := false
for _, sprin := range delegator.Ext {
if !found && (sprin.Name == "Program") {
found = true
}
if found {
kprin.Ext = append(kprin.Ext, sprin)
}
}
ra, err := tao.GenerateAttestation(policyKey.SigningKey, nil, keyNegoSays)
if err != nil {
return fmt.Errorf("Couldn't attest to the new says statement: %s", err)
}
if _, err := ms.WriteMessage(ra); err != nil {
return fmt.Errorf("Couldn't return the attestation on the channel: %s", err)
}
return nil
}
// ValidSigner checks the signature on an attestation and, if so, returns the signer.
func (a *Attestation) ValidSigner() (auth.Prin, error) {
signer, err := auth.UnmarshalPrin(a.Signer)
if err != nil {
return auth.Prin{}, err
}
if len(signer.Ext) != 0 {
return auth.Prin{}, newError("tao: attestation signer principal malformed: %s", signer)
}
switch signer.Type {
case "tpm":
// The PCRs are contained in the Speaker of an auth.Says statement that
// makes up the a.SerializedStatement.
f, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
return auth.Prin{}, newError("tao: couldn't unmarshal the statement: %s", err)
}
// A TPM attestation must be an auth.Says.
says, ok := f.(auth.Says)
if !ok {
return auth.Prin{}, newError("tao: the attestation statement was not an auth.Says statement")
}
// Signer is tpm; use tpm-specific signature verification. Extract the
// PCRs from the issuer name, unmarshal the key as an RSA key, and call
// tpm.VerifyQuote().
speaker, ok := says.Speaker.(auth.Prin)
if !ok {
return auth.Prin{}, newError("tao: the speaker of an attestation must be an auth.Prin")
}
pcrNums, pcrVals, err := ExtractPCRs(speaker)
if err != nil {
return auth.Prin{}, newError("tao: couldn't extract PCRs from the signer: %s", err)
}
pk, err := ExtractAIK(speaker)
if err != nil {
return auth.Prin{}, newError("tao: couldn't extract the AIK from the signer: %s", err)
}
if err := tpm.VerifyQuote(pk, a.SerializedStatement, a.Signature, pcrNums, pcrVals); err != nil {
return auth.Prin{}, newError("tao: TPM quote failed verification: %s", err)
}
return signer, nil
case "key":
// Signer is ECDSA key, use Tao signature verification.
v, err := FromPrincipal(signer)
if err != nil {
return auth.Prin{}, err
}
ok, err := v.Verify(a.SerializedStatement, AttestationSigningContext, a.Signature)
if err != nil {
return auth.Prin{}, err
}
if !ok {
return auth.Prin{}, newError("tao: attestation signature invalid")
}
return signer, nil
default:
return auth.Prin{}, newError("tao: attestation signer principal unrecognized: %s", signer.String())
}
}
// Validate checks whether an attestation is valid and, if so, it returns the
// statement conveyed by the attestation.
func (a *Attestation) Validate() (auth.Says, error) {
signer, err := a.ValidSigner()
if err != nil {
return auth.Says{}, err
}
f, err := auth.UnmarshalForm(a.SerializedStatement)
if err != nil {
return auth.Says{}, err
}
var stmt *auth.Says
if ptr, ok := f.(*auth.Says); ok {
stmt = ptr
} else if val, ok := f.(auth.Says); ok {
stmt = &val
} else {
return auth.Says{}, newError("tao: attestation statement has wrong type: %T", f)
}
if a.SerializedDelegation == nil {
// Case (1), no delegation present.
// Require that stmt.Speaker be a subprincipal of (or identical to) a.signer.
if !auth.SubprinOrIdentical(stmt.Speaker, signer) {
return auth.Says{}, newError("tao: attestation statement signer (%v) does not evidently speak for issuer (%v)", signer, stmt.Speaker)
}
} else {
// Case (2), delegation present.
// Require that:
// - delegation conveys delegator says delegate speaksfor delegator,
// - a.signer speaks for delegate
// - and delegator speaks for s.Speaker
var da Attestation
if err := proto.Unmarshal(a.SerializedDelegation, &da); err != nil {
return auth.Says{}, err
}
delegationStatement, err := da.Validate()
if err != nil {
return auth.Says{}, err
}
var delegation *auth.Speaksfor
if ptr, ok := delegationStatement.Message.(*auth.Speaksfor); ok {
delegation = ptr
} else if val, ok := delegationStatement.Message.(auth.Speaksfor); ok {
delegation = &val
} else {
return auth.Says{}, newError("tao: attestation delegation is wrong type")
}
if !delegationStatement.Speaker.Identical(delegation.Delegator) {
return auth.Says{}, newError("tao: attestation delegation is invalid")
}
if !auth.SubprinOrIdentical(delegation.Delegate, signer) {
return auth.Says{}, newError("tao: attestation delegation irrelevant to signer")
}
if !auth.SubprinOrIdentical(stmt.Speaker, delegation.Delegator) {
return auth.Says{}, newError("tao: attestation delegation irrelevant to issuer")
}
if stmt.Time == nil {
stmt.Time = delegationStatement.Time
} else if delegationStatement.Time != nil && *stmt.Time < *delegationStatement.Time {
stmt.Time = delegationStatement.Time
}
if stmt.Expiration == nil {
stmt.Expiration = delegationStatement.Expiration
} else if delegationStatement.Expiration != nil && *stmt.Expiration > *delegationStatement.Expiration {
stmt.Expiration = delegationStatement.Expiration
}
}
return *stmt, nil
}
// This function performs the following checks on a secret disclosure directive.
// (1) the directive signature is valid with respect to signerKey of directive
// (2) Either
// - policyKey matches the signerKey of directive
// - directive cert is a valid program cert (signed by policyKey) certifying the signerKey
// of directive as belonging to 'delegator'
// (3) the directive message is a statement of the form:
// 'policyKey/'delegator' says delegate can read protectedObjectId'
// where delegate is a Tao Principal and protectedObjectId is a (serialized) protected
// object message id.
func VerifySecretDisclosureDirective(policyKey *tao.Keys, directive *DirectiveMessage) (*auth.Prin,
*auth.Prin, *string, *po.ObjectIdMessage, error) {
// Check type of directive
if directive.Type == nil || *(directive.Type) != DirectiveMessage_SECRET_DISCLOSURE {
return nil, nil, nil, nil, errors.New(
"secret_disclosure: directive not of secret disclosure type.")
}
var verifier *tao.Verifier
var delegatorStr string
// Check directive signer matches policy key.
if bytes.Compare(
auth.Marshal(policyKey.SigningKey.ToPrincipal()), directive.GetSigner()) == 0 {
verifier = policyKey.SigningKey.GetVerifier()
delegatorStr = verifier.ToPrincipal().String()
} else {
// Check if program cert is valid, signed by policy key,
// cert public key matches signer and cert name matches speaker
// of says statement.
cert, err := x509.ParseCertificate(directive.Cert)
if err != nil {
return nil, nil, nil, nil, errors.New(
"error parsing directive program cert")
}
rootCert := x509.NewCertPool()
rootCert.AddCert(policyKey.Cert)
verifyOptions := x509.VerifyOptions{Roots: rootCert}
_, err = cert.Verify(verifyOptions)
if err != nil {
return nil, nil, nil, nil, errors.New(
"program cert not valid")
}
verifier, err = tao.FromX509(cert)
delegatorStr = cert.Subject.CommonName
if err != nil {
return nil, nil, nil, nil, err
}
if bytes.Compare(auth.Marshal(verifier.ToPrincipal()), directive.GetSigner()) != 0 {
return nil, nil, nil, nil, errors.New(
"secret_disclosure: directive signer doesn't match program key.")
}
}
// Verify signature.
ok, err := verifier.Verify(directive.GetSerializedStatement(), SigningContext,
directive.GetSignature())
if err != nil {
return nil, nil, nil, nil, err
}
if !ok {
return nil, nil, nil, nil,
errors.New("secret_disclosure: directive signature check failed.")
}
// Validate and return statement.
statement, err := auth.UnmarshalForm(directive.GetSerializedStatement())
if err != nil {
return nil, nil, nil, nil, err
}
var saysStatement *auth.Says
if ptr, ok := statement.(*auth.Says); ok {
saysStatement = ptr
} else if val, ok := statement.(auth.Says); ok {
saysStatement = &val
} else {
return nil, nil, nil, nil,
errors.New("secret_disclosure: directive statement not a 'Says'")
}
stmtSpeaker, ok := saysStatement.Speaker.(auth.Prin)
if !ok {
return nil, nil, nil, nil,
errors.New("secret_disclosure: directive speaker not a 'Prin'")
}
if stmtSpeaker.String() != delegatorStr {
return nil, nil, nil, nil, errors.New(
"secret_disclosure: directive statement speaker does not match signer")
}
pred, ok := saysStatement.Message.(auth.Pred)
if !ok {
return nil, nil, nil, nil,
errors.New("secret_disclosure: directive message not a 'Pred'")
}
predName := pred.Name
if predName == "" {
return nil, nil, nil, nil,
errors.New("secret_disclosure: directive predicate name is empty")
}
if len(pred.Arg) != 2 {
return nil, nil, nil, nil,
errors.New("secret_disclosure: directive predicate doesn't have 2 terms")
}
delegateName, ok := pred.Arg[0].(auth.Prin)
if !ok {
return nil, nil, nil, nil, errors.New(
"secret_disclosure: directive delegateName Term not of type auth.Prin.")
}
serializedObjId, ok := pred.Arg[1].(auth.Bytes)
if !ok {
return nil, nil, nil, nil, errors.New(
"secret_disclosure: directive ObjId Term not of type []byte.")
}
protectedObjId := po.ObjectIdMessage{}
err = proto.Unmarshal(serializedObjId, &protectedObjId)
if err != nil {
return nil, nil, nil, nil, errors.New(
"secret_disclosure: error deserializing protected ObjId.")
}
return &stmtSpeaker, &delegateName, &predName, &protectedObjId, nil
}