// GetEKCert reads the Endorsement Key certificate from the TPM's NVRAM and
// returns it, along with any error generated.
func GetEKCert(context *tspi.Context) (ekcert []byte, err error) {
var wellKnown [20]byte
tpm := context.GetTPM()
nv, err := context.CreateNV()
if err != nil {
return nil, err
}
policy, err := tpm.GetPolicy(tspi.TSS_POLICY_USAGE)
if err != nil {
return nil, err
}
policy.SetSecret(tspi.TSS_SECRET_MODE_SHA1, wellKnown[:])
nv.SetIndex(0x1000f000)
nv.AssignPolicy(policy)
data, err := nv.ReadValue(0, 5)
if err != nil {
return nil, err
}
tag := (uint)((uint)(data[0])<<8 | (uint)(data[1]))
if tag != 0x1001 {
return nil, fmt.Errorf("Invalid tag: %x", tag)
}
if data[2] != 0 {
return nil, fmt.Errorf("Invalid certificate")
}
ekbuflen := (uint)(uint(data[3])<<8 | (uint)(data[4]))
offset := (uint)(5)
data, err = nv.ReadValue(offset, 2)
tag = (uint)((uint)(data[0])<<8 | (uint)(data[1]))
if tag == 0x1002 {
offset += 2
ekbuflen -= 2
} else if data[0] != 0x30 {
return nil, fmt.Errorf("Invalid header: %x\n", tag)
}
ekoffset := (uint)(0)
var ekbuf []byte
for ekoffset < ekbuflen {
length := (uint)(ekbuflen - ekoffset)
if length > 128 {
length = 128
}
data, err = nv.ReadValue(offset, length)
if err != nil {
return nil, err
}
ekbuf = append(ekbuf, data...)
offset += length
ekoffset += length
}
return ekbuf, nil
}
// AIKChallengeResponse takes the output from GenerateChallenge along with the
// encrypted AIK key blob. The TPM then decrypts the asymmetric challenge with
// its EK in order to obtain the AES key, and uses the AES key to decrypt the
// symmetrically encrypted data. It verifies that this data blob corresponds
// to the AIK it was given, and if so hands back the secret contained within
// the symmetrically encrypted data.
func AIKChallengeResponse(context *tspi.Context, aikblob []byte, asymchallenge []byte, symchallenge []byte) (secret []byte, err error) {
var wellKnown [20]byte
srk, err := context.LoadKeyByUUID(tspi.TSS_PS_TYPE_SYSTEM, tspi.TSS_UUID_SRK)
if err != nil {
return nil, err
}
srkpolicy, err := srk.GetPolicy(tspi.TSS_POLICY_USAGE)
if err != nil {
return nil, err
}
srkpolicy.SetSecret(tspi.TSS_SECRET_MODE_SHA1, wellKnown[:])
tpm := context.GetTPM()
tpmpolicy, err := context.CreatePolicy(tspi.TSS_POLICY_USAGE)
if err != nil {
return nil, err
}
tpm.AssignPolicy(tpmpolicy)
tpmpolicy.SetSecret(tspi.TSS_SECRET_MODE_SHA1, wellKnown[:])
aik, err := context.LoadKeyByBlob(srk, aikblob)
if err != nil {
return nil, err
}
secret, err = tpm.ActivateIdentity(aik, asymchallenge, symchallenge)
return secret, err
}
// CreateAIK asks the TPM to generate an Attestation Identity Key. It returns
// the unencrypted public half of the AIK along with an encrypted blob
// containing both halves of the key, and any error.
func CreateAIK(context *tspi.Context) ([]byte, []byte, error) {
var wellKnown [20]byte
n := make([]byte, 2048/8)
for i := 0; i < 2048/8; i++ {
n[i] = 0xff
}
srk, err := context.LoadKeyByUUID(tspi.TSS_PS_TYPE_SYSTEM, tspi.TSS_UUID_SRK)
if err != nil {
return nil, nil, err
}
keypolicy, err := srk.GetPolicy(tspi.TSS_POLICY_USAGE)
if err != nil {
return nil, nil, err
}
err = keypolicy.SetSecret(tspi.TSS_SECRET_MODE_SHA1, wellKnown[:])
if err != nil {
return nil, nil, err
}
tpm := context.GetTPM()
tpmpolicy, err := tpm.GetPolicy(tspi.TSS_POLICY_USAGE)
if err != nil {
return nil, nil, err
}
err = tpm.AssignPolicy(tpmpolicy)
if err != nil {
return nil, nil, err
}
err = tpmpolicy.SetSecret(tspi.TSS_SECRET_MODE_SHA1, wellKnown[:])
if err != nil {
return nil, nil, err
}
pcakey, err := context.CreateKey(tspi.TSS_KEY_TYPE_LEGACY | tspi.TSS_KEY_SIZE_2048)
if err != nil {
return nil, nil, err
}
err = pcakey.SetModulus(n)
if err != nil {
return nil, nil, err
}
aik, err := context.CreateKey(tspi.TSS_KEY_TYPE_IDENTITY | tspi.TSS_KEY_SIZE_2048)
if err != nil {
return nil, nil, err
}
_, err = tpm.CollateIdentityRequest(srk, pcakey, aik)
if err != nil {
return nil, nil, err
}
pubkey, err := aik.GetPubKeyBlob()
if err != nil {
return nil, nil, err
}
blob, err := aik.GetKeyBlob()
if err != nil {
return nil, nil, err
}
_, err = aik.GetModulus()
return pubkey, blob, nil
}