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tss2.go
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tss2.go
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package tss2
import (
"encoding/asn1"
"errors"
"golang.org/x/crypto/cryptobyte"
cryptobyte_asn1 "golang.org/x/crypto/cryptobyte/asn1"
)
var (
oidLoadableKey = asn1.ObjectIdentifier{2, 23, 133, 10, 1, 3}
oidImportableKey = asn1.ObjectIdentifier{2, 23, 133, 10, 1, 4}
oidSealedKey = asn1.ObjectIdentifier{2, 23, 133, 10, 1, 5}
)
// TPMKey is defined in https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.html#section-3.1:
//
// TPMKey ::= SEQUENCE {
// type OBJECT IDENTIFIER,
// emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL,
// policy [1] EXPLICIT SEQUENCE OF TPMPolicy OPTIONAL,
// secret [2] EXPLICIT OCTET STRING OPTIONAL,
// authPolicy [3] EXPLICIT SEQUENCE OF TPMAuthPolicy OPTIONAL,
// parent INTEGER,
// pubkey OCTET STRING,
// privkey OCTET STRING
// }
type TPMKey struct {
Type asn1.ObjectIdentifier
EmptyAuth bool `asn1:"optional,explicit,tag:0"`
Policy []TPMPolicy `asn1:"optional,explicit,tag:1"`
Secret []byte `asn1:"optional,explicit,tag:2"`
AuthPolicy []TPMAuthPolicy `asn1:"optional,explicit,tag:3"`
Parent int
PublicKey []byte
PrivateKey []byte
}
// TPMPolicy is defined in https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.html#section-4.1:
//
// TPMPolicy ::= SEQUENCE {
// commandCode [0] EXPLICIT INTEGER,
// commandPolicy [1] EXPLICIT OCTET STRING
// }
type TPMPolicy struct {
CommandCode int `asn1:"explicit,tag:0"`
CommandPolicy []byte `asn1:"explicit,tag:1"`
}
// TPMAuthPolicy is defined in https://www.hansenpartnership.com/draft-bottomley-tpm2-keys.html#section-5.1
//
// TPMAuthPolicy ::= SEQUENCE {
// name [0] EXPLICIT UTF8String OPTIONAL,
// policy [1] EXPLICIT SEQUENCE OF TPMPolicy
// }
type TPMAuthPolicy struct {
Name string `asn1:"utf8,optional,explicit,tag:0"`
Policy []TPMPolicy `asn1:"explicit,tag:1"`
}
// ParsePrivateKey parses a single TPM key from the given ASN.1 DER data.
//
// # Experimental
//
// Notice: This API is EXPERIMENTAL and may be changed or removed in a later
// release.
func ParsePrivateKey(derBytes []byte) (*TPMKey, error) {
var err error
input := cryptobyte.String(derBytes)
if !input.ReadASN1(&input, cryptobyte_asn1.SEQUENCE) {
return nil, errors.New("malformed TSS2 key")
}
key := new(TPMKey)
if !input.ReadASN1ObjectIdentifier(&key.Type) {
return nil, errors.New("malformed TSS2 type")
}
if tag, ok := readOptionalTag(&input, 0); ok {
if !readASN1Boolean(&tag, &key.EmptyAuth) {
return nil, errors.New("malformed TSS2 emptyAuth")
}
}
// TODO(mariano): generate key with policy
if tag, ok := readOptionalTag(&input, 1); ok {
var policy cryptobyte.String
if !tag.ReadASN1(&policy, cryptobyte_asn1.SEQUENCE) {
return nil, errors.New("malformed TSS2 policy")
}
key.Policy, err = readTPMPolicySequence(&policy)
if err != nil {
return nil, err
}
}
// TODO(mariano): generate key with secret
if tag, ok := readOptionalTag(&input, 2); ok {
if key.Secret, ok = readOctetString(&tag); !ok {
return nil, errors.New("malformed TSS2 secret")
}
}
// TODO(mariano): generate key with authPolicy
if tag, ok := readOptionalTag(&input, 3); ok {
if key.AuthPolicy, err = readTPMAuthPolicy(&tag); err != nil {
return nil, err
}
}
if !input.ReadASN1Integer(&key.Parent) {
return nil, errors.New("malformed TSS2 parent")
}
var ok bool
if key.PublicKey, ok = readOctetString(&input); !ok {
return nil, errors.New("malformed TSS2 pubkey")
}
if key.PrivateKey, ok = readOctetString(&input); !ok {
return nil, errors.New("malformed TSS2 privkey")
}
return key, nil
}
// MarshalPrivateKey converts the given key to a TSS2 ASN.1 DER form.
//
// # Experimental
//
// Notice: This API is EXPERIMENTAL and may be changed or removed in a later
// release.
func MarshalPrivateKey(key *TPMKey) ([]byte, error) {
if key == nil {
return nil, errors.New("tpmKey cannot be nil")
}
return asn1.Marshal(*key)
}
func readOptionalTag(input *cryptobyte.String, tag int) (cryptobyte.String, bool) {
var isPresent bool
var output cryptobyte.String
if !input.ReadOptionalASN1(&output, &isPresent, cryptobyte_asn1.Tag(tag).Constructed().ContextSpecific()) {
return nil, false
}
return output, isPresent
}
func readOctetString(input *cryptobyte.String) ([]byte, bool) {
var os cryptobyte.String
if !input.ReadASN1(&os, cryptobyte_asn1.OCTET_STRING) {
return nil, false
}
return os, true
}
// readASN1Boolean accepts 0x01 as a TRUE value for a boolean type. OpenSSL
// seems to confuse DER with BER encoding and encodes the BOOLEAN TRUE as 0x01
// instead of 0xff.
func readASN1Boolean(input *cryptobyte.String, out *bool) bool {
var bytes cryptobyte.String
if !input.ReadASN1(&bytes, cryptobyte_asn1.BOOLEAN) || len(bytes) != 1 {
return false
}
switch bytes[0] {
case 0:
*out = false
case 1, 0xff:
*out = true
default:
return false
}
return true
}
func readTPMPolicySequence(input *cryptobyte.String) ([]TPMPolicy, error) {
var policies []TPMPolicy
for !input.Empty() {
var p TPMPolicy
var seq cryptobyte.String
if !input.ReadASN1(&seq, cryptobyte_asn1.SEQUENCE) {
return nil, errors.New("malformed TSS2 policy")
}
tag, ok := readOptionalTag(&seq, 0)
if !ok || !tag.ReadASN1Integer(&p.CommandCode) {
return nil, errors.New("malformed TSS2 policy commandCode")
}
tag, ok = readOptionalTag(&seq, 1)
if !ok {
return nil, errors.New("malformed TSS2 policy commandPolicy")
}
if p.CommandPolicy, ok = readOctetString(&tag); !ok {
return nil, errors.New("malformed TSS2 policy commandPolicy")
}
policies = append(policies, p)
}
return policies, nil
}
func readTPMAuthPolicy(input *cryptobyte.String) ([]TPMAuthPolicy, error) {
var (
err error
authPolicy cryptobyte.String
authPolicies []TPMAuthPolicy
)
if !input.ReadASN1(&authPolicy, cryptobyte_asn1.SEQUENCE) {
return nil, errors.New("malformed TSS2 authPolicy")
}
for !authPolicy.Empty() {
var ap TPMAuthPolicy
var seq cryptobyte.String
if !authPolicy.ReadASN1(&seq, cryptobyte_asn1.SEQUENCE) {
return nil, errors.New("malformed TSS2 authPolicy")
}
var name cryptobyte.String
if tag, ok := readOptionalTag(&seq, 0); ok {
if !tag.ReadASN1(&name, cryptobyte_asn1.UTF8String) {
return nil, errors.New("malformed TSS2 authPolicy name")
}
ap.Name = string(name)
}
var policySeq cryptobyte.String
if tag, ok := readOptionalTag(&seq, 1); ok {
if !tag.ReadASN1(&policySeq, cryptobyte_asn1.SEQUENCE) {
return nil, errors.New("malformed TSS2 authPolicy policy")
}
if ap.Policy, err = readTPMPolicySequence(&policySeq); err != nil {
return nil, errors.New("malformed TSS2 authPolicy policy")
}
}
authPolicies = append(authPolicies, ap)
}
return authPolicies, nil
}