// Attest requests the Tao host sign a statement on behalf of the caller.
func (t *StackedHost) Attest(childSubprin auth.SubPrin, issuer *auth.Prin,
time, expiration *int64, message auth.Form) (*Attestation, error) {
child := t.taoHostName.MakeSubprincipal(childSubprin)
if issuer != nil {
if !auth.SubprinOrIdentical(*issuer, child) {
return nil, newError("invalid issuer in statement")
}
} else {
issuer = &child
}
if t.keys == nil || t.keys.SigningKey == nil {
return t.hostTao.Attest(issuer, time, expiration, message)
}
stmt := auth.Says{Speaker: *issuer, Time: time, Expiration: expiration, Message: message}
var d []byte
if t.keys.Delegation != nil {
var err error
d, err = proto.Marshal(t.keys.Delegation)
if err != nil {
return nil, err
}
}
return GenerateAttestation(t.keys.SigningKey, d, stmt)
}
// Attest requests the Tao host sign a statement on behalf of the caller. The
// optional issuer, time and expiration will be given default values if nil.
func (tt *TPMTao) Attest(issuer *auth.Prin, start, expiration *int64, message auth.Form) (*Attestation, error) {
if issuer == nil {
issuer = &tt.name
} else if !auth.SubprinOrIdentical(*issuer, tt.name) {
return nil, errors.New("invalid issuer in statement")
}
// TODO(tmroeder): we assume here that the PCRs haven't changed (e.g., been
// extended) since this TPMTao was created. If they have, then the PCRs will
// be wrong when we extend the principal here with them as the first
// component. This doesn't matter at the moment, since we don't currently
// support extending the PCRs or clearing them, but it will need to be
// changed when we do.
stmt := auth.Says{
Speaker: *issuer,
Time: start,
Expiration: expiration,
Message: message,
}
// This is done in GenerateAttestation, but the TPM attestation is signed
// differently, so we do the time calculations here.
t := time.Now()
if stmt.Time == nil {
i := t.UnixNano()
stmt.Time = &i
}
if stmt.Expiration == nil {
i := t.Add(365 * 24 * time.Hour).UnixNano()
stmt.Expiration = &i
}
ser := auth.Marshal(stmt)
// TODO(tmroeder): check the pcrVals for sanity once we support extending or
// clearing the PCRs.
sig, _, err := tpm.Quote(tt.tpmfile, tt.aikHandle, ser, tt.pcrNums, tt.srkAuth[:])
if err != nil {
return nil, err
}
// Pull off the extensions from the name to get the bare TPM key for the
// signer.
signer := auth.Prin{
Type: tt.name.Type,
Key: tt.name.Key,
}
a := &Attestation{
SerializedStatement: ser,
Signature: sig,
Signer: auth.Marshal(signer),
}
return a, nil
}
// Attest requests the Tao host sign a statement on behalf of the caller.
func (t *RootHost) Attest(childSubprin auth.SubPrin, issuer *auth.Prin,
time, expiration *int64, message auth.Form) (*Attestation, error) {
child := t.taoHostName.MakeSubprincipal(childSubprin)
if issuer != nil {
if !auth.SubprinOrIdentical(*issuer, child) {
return nil, newError("invalid issuer in statement")
}
} else {
issuer = &child
}
stmt := auth.Says{Speaker: *issuer, Time: time, Expiration: expiration, Message: message}
return GenerateAttestation(t.keys.SigningKey, nil /* delegation */, stmt)
}
// Attest requests that the Tao host sign a statement on behalf of the caller.
func (s *SoftTao) Attest(issuer *auth.Prin, time, expiration *int64, message auth.Form) (*Attestation, error) {
child := s.name.MakeSubprincipal(s.nameExtension)
if issuer == nil {
issuer = &child
} else if !auth.SubprinOrIdentical(issuer, child) {
return nil, newError("Invalid issuer in statement: %s may not speak for %s", child, issuer)
}
stmt := auth.Says{Speaker: *issuer, Time: time, Expiration: expiration, Message: message}
var delegation []byte
if s.keys.Delegation != nil {
var err error
delegation, err = proto.Marshal(s.keys.Delegation)
if err != nil {
return nil, err
}
}
return GenerateAttestation(s.keys.SigningKey, delegation, stmt)
}
// SignsForPrincipal returns true when prin is (or is a subprincipal of) this verifier key.
func (v *Verifier) SignsForPrincipal(prin auth.Prin) bool {
return auth.SubprinOrIdentical(prin, v.ToPrincipal())
}
// 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
}
// Attest requests the Tao host seal a statement on behalf of the caller. The
// optional issuer, time and expiration will be given default values if nil.
func (tt *TPM2Tao) Attest(issuer *auth.Prin, start, expiration *int64,
message auth.Form) (*Attestation, error) {
fmt.Fprintf(os.Stderr, "About to load the quote key in attest\n")
qh, err := tt.loadQuote()
if err != nil {
return nil, err
}
defer tpm2.FlushContext(tt.rw, qh)
if issuer == nil {
issuer = &tt.name
} else if !auth.SubprinOrIdentical(*issuer, tt.name) {
return nil, errors.New("invalid issuer in statement")
}
// TODO(tmroeder): we assume here that the PCRs haven't changed (e.g., been
// extended) since this TPM2Tao was created. If they have, then the PCRs will
// be wrong when we extend the principal here with them as the first
// component. This doesn't matter at the moment, since we don't currently
// support extending the PCRs or clearing them, but it will need to be
// changed when we do.
stmt := auth.Says{
Speaker: *issuer,
Time: start,
Expiration: expiration,
Message: message,
}
// This is done in GenerateAttestation, but the TPM attestation is sealed
// differently, so we do the time calculations here.
t := time.Now()
if stmt.Time == nil {
i := t.UnixNano()
stmt.Time = &i
}
if stmt.Expiration == nil {
i := t.Add(365 * 24 * time.Hour).UnixNano()
stmt.Expiration = &i
}
ser := auth.Marshal(stmt)
var pcrVals [][]byte
toQuote, err := tpm2.FormatTpm2Quote(ser, tt.pcrs, pcrVals)
if err != nil {
return nil, errors.New("Can't format tpm2 Quote")
}
// TODO(tmroeder): check the pcrVals for sanity once we support extending or
// clearing the PCRs.
quote_struct, sig, err := tpm2.Quote(tt.rw, qh, "", tt.password,
toQuote, tt.pcrs, uint16(tpm2.AlgTPM_ALG_NULL))
if err != nil {
return nil, err
}
fmt.Printf("toQuote: %x\n", toQuote)
fmt.Printf("Quote: %x\n", quote_struct)
fmt.Printf("sig: %x\n", sig)
quoteKey, err := x509.MarshalPKIXPublicKey(tt.verifier)
if err != nil {
return nil, err
}
// TODO(kwalsh) remove Tpm2QuoteStructure from Attestation structure
a := &Attestation{
SerializedStatement: ser,
Signature: sig,
SignerType: proto.String("tpm2"),
SignerKey: quoteKey,
Tpm2QuoteStructure: quote_struct,
}
return a, nil
}
