from .internal.crypto import (
_kdfa,
_get_digest,
_symdef_to_crypt,
_secret_to_seed,
_generate_seed,
_decrypt,
_encrypt,
_check_hmac,
_hmac,
_get_digest_size,
)
from .types import *
from .ESAPI import ESAPI
from .constants import (
ESYS_TR,
TPM2_CAP,
TPM2_PT_NV,
TPM2_ECC,
TPM2_PT,
TPM2_RH,
)
from .internal.templates import _ek
from .TSS2_Exception import TSS2_Exception
from cryptography.hazmat.primitives import constant_time as ct
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.backends import default_backend
from typing import Optional, Tuple, Callable, List
import secrets
[docs]def make_credential(
public: TPM2B_PUBLIC, credential: bytes, name: TPM2B_NAME
) -> Tuple[TPM2B_ID_OBJECT, TPM2B_ENCRYPTED_SECRET]:
"""Encrypts credential for use with activate_credential
Args:
public (TPMT_PUBLIC): The public area of the activation key
credential (bytes): The credential to be encrypted
name (bytes): The name of the key associated with the credential
Returns:
A tuple of (TPM2B_ID_OBJECT, TPM2B_ENCRYPTED_SECRET)
Raises:
ValueError: If the public key type is not supported
"""
if isinstance(public, TPM2B_PUBLIC):
public = public.publicArea
if isinstance(credential, bytes):
credential = TPM2B_DIGEST(buffer=credential)
if isinstance(name, TPM2B_SIMPLE_OBJECT):
name = bytes(name)
seed, enc_seed = _generate_seed(public, b"IDENTITY\x00")
(cipher, symmode, symbits) = _symdef_to_crypt(
public.parameters.asymDetail.symmetric
)
symkey = _kdfa(public.nameAlg, seed, b"STORAGE", name, b"", symbits)
enc_cred = _encrypt(cipher, symmode, symkey, credential.marshal())
halg = _get_digest(public.nameAlg)
hmackey = _kdfa(public.nameAlg, seed, b"INTEGRITY", b"", b"", halg.digest_size * 8)
outerhmac = _hmac(halg, hmackey, enc_cred, name)
hmacdata = TPM2B_DIGEST(buffer=outerhmac).marshal()
credblob = TPM2B_ID_OBJECT(credential=hmacdata + enc_cred)
secret = TPM2B_ENCRYPTED_SECRET(secret=enc_seed)
return (credblob, secret)
[docs]def wrap(
newparent: TPMT_PUBLIC,
public: TPM2B_PUBLIC,
sensitive: TPM2B_SENSITIVE,
symkey: Optional[bytes] = None,
symdef: Optional[TPMT_SYM_DEF_OBJECT] = None,
) -> Tuple[TPM2B_DATA, TPM2B_PRIVATE, TPM2B_ENCRYPTED_SECRET]:
"""Wraps key under a TPM key hierarchy
A key is wrapped following the Duplication protections of the TPM Architecture specification.
The architecture specification is found in "Part 1: Architecture" at the following link:
- https://trustedcomputinggroup.org/resource/tpm-library-specification/
At the time of this writing, spec 1.59 was most recent and it was under section 23.3,
titled "Duplication".
Args:
newparent (TPMT_PUBLIC): The public area of the parent
public (TPM2B_PUBLIC): The public area of the key
sensitive (TPM2B_SENSITIVE): The sensitive area of the key
symkey (bytes or None):
Symmetric key for inner encryption. Defaults to None.
When None and symdef is defined a key will be generated based on the key size for symdef.
symdef (TPMT_SYM_DEF_OBJECT or None):
Symmetric algorithm to be used for inner encryption, defaults to None.
If None no inner wrapping is performed, else this should be set to aes128CFB since that is
what the TPM supports. To set to aes128cfb, do:
::
TPMT_SYM_DEF(
algorithm=TPM2_ALG.AES,
keyBits=TPMU_SYM_KEY_BITS(sym=128),
mode=TPMU_SYM_MODE(sym=TPM2_ALG.CFB),
)
Returns:
A tuple of (TPM2B_DATA, TPM2B_PRIVATE, TPM2B_ENCRYPTED_SECRET) which is the encryption key, the
the wrapped duplicate and the encrypted seed.
Raises:
ValueError: If the public key type or symmetric algorithm are not supported
"""
enckeyout = TPM2B_DATA()
outsymseed = TPM2B_ENCRYPTED_SECRET()
sensb = sensitive.marshal()
name = bytes(public.get_name())
if symdef and symdef.algorithm != TPM2_ALG.NULL:
cipher, mode, bits = _symdef_to_crypt(symdef)
if not symkey:
klen = int(bits / 8)
symkey = secrets.token_bytes(klen)
halg = _get_digest(public.publicArea.nameAlg)
h = hashes.Hash(halg(), backend=default_backend())
h.update(sensb)
h.update(name)
innerint = TPM2B_DIGEST(buffer=h.finalize()).marshal()
encsens = _encrypt(cipher, mode, symkey, innerint + sensb)
enckeyout.buffer = symkey
else:
encsens = sensb
seed, outsymseed.secret = _generate_seed(newparent, b"DUPLICATE\x00")
cipher, mode, bits = _symdef_to_crypt(newparent.parameters.asymDetail.symmetric)
outerkey = _kdfa(newparent.nameAlg, seed, b"STORAGE", name, b"", bits)
dupsens = _encrypt(cipher, mode, outerkey, encsens)
halg = _get_digest(newparent.nameAlg)
hmackey = _kdfa(
newparent.nameAlg, seed, b"INTEGRITY", b"", b"", halg.digest_size * 8
)
outerhmac = _hmac(halg, hmackey, dupsens, name)
hmacdata = TPM2B_DIGEST(buffer=outerhmac).marshal()
duplicate = TPM2B_PRIVATE(buffer=hmacdata + dupsens)
return (enckeyout, duplicate, outsymseed)
[docs]def unwrap(
newparentpub: TPMT_PUBLIC,
newparentpriv: TPMT_SENSITIVE,
public: TPM2B_PUBLIC,
duplicate: TPM2B_PRIVATE,
outsymseed: TPM2B_ENCRYPTED_SECRET,
symkey: Optional[bytes] = None,
symdef: Optional[TPMT_SYM_DEF_OBJECT] = None,
) -> TPM2B_SENSITIVE:
"""unwraps a key under a TPM key hierarchy. In essence, export key from TPM.
This is the inverse function to the wrap() routine. This is usually performed by the TPM when importing
objects, however, if an object is duplicated under a new parent where one has both the public and private
keys, the object can be unwrapped.
Args:
newparentpub (TPMT_PUBLIC): The public area of the parent the key was duplicated/wrapped under.
newparentpriv (TPMT_SENSITIVE): The private key of the parent the key was duplicated/wrapped under.
public (TPM2B_PUBLIC): The public area of the key to be unwrapped.
duplicate (TPM2B_PRIVATE): The private or wrapped key to be unwrapped.
outsymseed (TPM2B_ENCRYPTED_SECRET): The output symmetric seed from a wrap or duplicate call.
symkey (bytes or None):
Symmetric key for inner encryption. Defaults to None.
When None and symdef is defined a key will be generated based on the key size for symdef.
symdef (TPMT_SYM_DEF_OBJECT or None):
Symmetric algorithm to be used for inner encryption, defaults to None.
If None no inner wrapping is performed, else this should be set to aes128CFB since that is what
the TPM supports. To set to aes128cfb, do:
::
TPMT_SYM_DEF(
algorithm=TPM2_ALG.AES,
keyBits=TPMU_SYM_KEY_BITS(sym=128),
mode=TPMU_SYM_MODE(sym=TPM2_ALG.CFB),
)
Returns:
A TPM2B_SENSITIVE which contains the raw key material.
Raises:
ValueError: If the public key type or symmetric algorithm are not supported
"""
halg = _get_digest(newparentpub.nameAlg)
seed = _secret_to_seed(newparentpriv, newparentpub, b"DUPLICATE\x00", outsymseed)
hmackey = _kdfa(
newparentpub.nameAlg, seed, b"INTEGRITY", b"", b"", halg.digest_size * 8
)
buffer = bytes(duplicate)
hmacdata, offset = TPM2B_DIGEST.unmarshal(buffer)
outerhmac = bytes(hmacdata)
dupsens = buffer[offset:]
name = bytes(public.get_name())
_check_hmac(halg, hmackey, dupsens, name, outerhmac)
cipher, mode, bits = _symdef_to_crypt(newparentpub.parameters.asymDetail.symmetric)
outerkey = _kdfa(newparentpub.nameAlg, seed, b"STORAGE", name, b"", bits)
sensb = _decrypt(cipher, mode, outerkey, dupsens)
if symdef and symdef.algorithm != TPM2_ALG.NULL:
if not symkey:
raise RuntimeError(
"Expected symkey when symdef is not None or Tsymdef.algorithm is not TPM2_ALG.NULL"
)
cipher, mode, bits = _symdef_to_crypt(symdef)
halg = _get_digest(public.publicArea.nameAlg)
# unwrap the inner encryption which is the integrity + TPM2B_SENSITIVE
innerint_and_decsens = _decrypt(cipher, mode, symkey, sensb)
innerint, offset = TPM2B_DIGEST.unmarshal(innerint_and_decsens)
innerint = bytes(innerint)
decsensb = innerint_and_decsens[offset:]
h = hashes.Hash(halg(), backend=default_backend())
h.update(decsensb)
h.update(name)
integrity = h.finalize()
if not ct.bytes_eq(integrity, innerint):
raise RuntimeError("Expected inner integrity to match")
decsens = decsensb
else:
decsens = sensb
s, l = TPM2B_SENSITIVE.unmarshal(decsens)
if len(decsens) != l:
raise RuntimeError(
f"Expected the sensitive buffer to be size {l}, got: {len(decsens)}"
)
return s
[docs]class NoSuchIndex(Exception):
"""NV index is not defined exception
Args:
index (int): The NV index requested
"""
def __init__(self, index):
self.index = index
def __str__(self):
return f"NV index 0x{index:08x} does not exist"
[docs]class NVReadEK:
"""NV read callback to be used with create_ek_template
Args:
ectx (ESAPI): The ESAPI context for reading from NV areas
auth_handle (ESYS_TR): Handle indicating the source of the authorization. Defaults to the index being read.
session1 (ESYS_TR): A session for securing the TPM command (optional). Defaults to ESYS_TR.PASSWORD.
session2 (ESYS_TR): A session for securing the TPM command (optional). Defaults to ESYS_TR.NONE.
session3 (ESYS_TR): A session for securing the TPM command (optional). Defaults to ESYS_TR.NONE.
"""
def __init__(
self,
ectx: ESAPI,
auth_handle: ESYS_TR = None,
session1: ESYS_TR = ESYS_TR.PASSWORD,
session2: ESYS_TR = ESYS_TR.NONE,
session3: ESYS_TR = ESYS_TR.NONE,
):
self._ectx = ectx
self._auth_handle = auth_handle
self._session1 = session1
self._session2 = session2
self._session3 = session3
self._buffer_max = 512
more = True
while more:
more, data = self._ectx.get_capability(
TPM2_CAP.TPM_PROPERTIES,
TPM2_PT.FIXED,
4096,
session1=session2,
session2=session3,
)
props = data.data.tpmProperties
for p in props:
if p.property == TPM2_PT_NV.BUFFER_MAX:
self._buffer_max = p.value
more = False
break
def __call__(self, index: Union[int, TPM2_RH]) -> bytes:
try:
nvh = self._ectx.tr_from_tpmpublic(
index, session1=self._session2, session2=self._session3
)
except TSS2_Exception as e:
if e.rc == 0x18B:
raise NoSuchIndex(index)
else:
raise e
nvpub, _ = self._ectx.nv_read_public(
nvh, session1=self._session2, session2=self._session3
)
nvdata = b""
left = nvpub.nvPublic.dataSize
while left > 0:
off = nvpub.nvPublic.dataSize - left
size = self._buffer_max if left > self._buffer_max else left
data = self._ectx.nv_read(
nvh,
size,
off,
auth_handle=self._auth_handle,
session1=self._session1,
session2=self._session2,
session3=self._session3,
)
nvdata = nvdata + bytes(data)
left = left - len(data)
return nvdata
[docs]def create_ek_template(
ektype: str, nv_read_cb: Callable[[Union[int, TPM2_RH]], bytes]
) -> Tuple[bytes, TPM2B_PUBLIC]:
"""Creates an Endorsenment Key template which when created matches the EK certificate
The template is created according to TCG EK Credential Profile For TPM Family 2.0:
- https://trustedcomputinggroup.org/resource/tcg-ek-credential-profile-for-tpm-family-2-0/
Args:
ektype (str): The endoresment key type.
nv_read_cb (Callable[Union[int, TPM2_RH]]): The callback to use for reading NV areas.
Note:
nv_read_cb MUST raise a NoSuchIndex exception if the NV index isn't defined.
Returns:
A tuple of the certificate (can be None) and the template as a TPM2B_PUBLIC instance
Raises:
ValueError: If ektype is unknown or if a high range certificate is requested but not found.
"""
en = ektype.replace("-", "_")
if not hasattr(_ek, en):
raise ValueError(f"unknown EK type {ektype}")
(cert_index, template) = getattr(_ek, en)
nonce_index = None
if ektype in ("EK-RSA2048", "EK-ECC256"):
nonce_index = cert_index + 1
template_index = cert_index + 2
else:
template_index = cert_index + 1
cert = None
try:
cert = nv_read_cb(cert_index)
except NoSuchIndex:
if ektype not in ("EK-RSA2048", "EK-ECC256"):
raise ValueError(f"no certificate found for {ektype}")
try:
templb = nv_read_cb(template_index)
tt, _ = TPMT_PUBLIC.unmarshal(templb)
template = TPM2B_PUBLIC(publicArea=tt)
except NoSuchIndex:
# The TPM is not required to have these Indices, but we must try
# Avoids a race on checking for NV and then reading if a delete
# comes in
pass
nonce = None
if nonce_index:
try:
nonce = nv_read_cb(nonce_index)
except NoSuchIndex:
# The TPM is not required to have these Indices, but we must try
# Avoids a race on checking for NV and then reading if a delete
# comes in
pass
if nonce and template.publicArea.type == TPM2_ALG.RSA:
template.publicArea.unique.rsa = nonce + ((256 - len(nonce)) * b"\x00")
elif (
nonce
and template.publicArea.type == TPM2_ALG.ECC
and template.publicArea.parameters.eccDetail.curveID == TPM2_ECC.NIST_P256
):
template.publicArea.unique.ecc.x = nonce + ((32 - len(nonce)) * b"\x00")
template.publicArea.unique.ecc.y = b"\x00" * 32
return cert, template