imgtool: Add generic ECDSA TLV support
Update imgtool to support the new
generic ECDSA TLV and the ECDSA
p384 curve type with sha-384
Signed-off-by: Roland Mikhel <roland.mikhel@arm.com>
Change-Id: I9b1887610cc5d0e7cde90f47999fcdf3500ef51c
diff --git a/scripts/imgtool/image.py b/scripts/imgtool/image.py
index 495416b..8da49b9 100644
--- a/scripts/imgtool/image.py
+++ b/scripts/imgtool/image.py
@@ -62,10 +62,12 @@
'KEYHASH': 0x01,
'PUBKEY': 0x02,
'SHA256': 0x10,
+ 'SHA384': 0x11,
'RSA2048': 0x20,
'ECDSA256': 0x22,
'RSA3072': 0x23,
'ED25519': 0x24,
+ 'ECDSASIG': 0x25,
'ENCRSA2048': 0x30,
'ENCKW': 0x31,
'ENCEC256': 0x32,
@@ -94,10 +96,12 @@
INVALID_SIGNATURE
""")
+
def align_up(num, align):
assert (align & (align - 1) == 0) and align != 0
return (num + (align - 1)) & ~(align - 1)
+
class TLV():
def __init__(self, endian, magic=TLV_INFO_MAGIC):
self.magic = magic
@@ -116,7 +120,7 @@
if not TLV_VENDOR_RES_MIN <= kind <= TLV_VENDOR_RES_MAX:
msg = "Invalid custom TLV type value '0x{:04x}', allowed " \
"value should be between 0x{:04x} and 0x{:04x}".format(
- kind, TLV_VENDOR_RES_MIN, TLV_VENDOR_RES_MAX)
+ kind, TLV_VENDOR_RES_MIN, TLV_VENDOR_RES_MAX)
raise click.UsageError(msg)
buf = struct.pack(e + 'HH', kind, len(payload))
else:
@@ -250,11 +254,13 @@
self.enctlv_len)
trailer_addr = (self.base_addr + self.slot_size) - trailer_size
if self.confirm and not self.overwrite_only:
- magic_align_size = align_up(len(self.boot_magic), self.max_align)
+ magic_align_size = align_up(len(self.boot_magic),
+ self.max_align)
image_ok_idx = -(magic_align_size + self.max_align)
flag = bytearray([self.erased_val] * self.max_align)
- flag[0] = 0x01 # image_ok = 0x01
- h.puts(trailer_addr + trailer_size + image_ok_idx, bytes(flag))
+ flag[0] = 0x01 # image_ok = 0x01
+ h.puts(trailer_addr + trailer_size + image_ok_idx,
+ bytes(flag))
h.puts(trailer_addr + (trailer_size - len(self.boot_magic)),
bytes(self.boot_magic))
h.tofile(path, 'hex')
@@ -311,20 +317,31 @@
return cipherkey, ciphermac, pubk
def create(self, key, public_key_format, enckey, dependencies=None,
- sw_type=None, custom_tlvs=None, encrypt_keylen=128, clear=False, fixed_sig=None, pub_key=None, vector_to_sign=None):
+ sw_type=None, custom_tlvs=None, encrypt_keylen=128, clear=False,
+ fixed_sig=None, pub_key=None, vector_to_sign=None,
+ use_legacy_tlv=False):
self.enckey = enckey
+ # Check what hashing algorithm should be used
+ if (key is not None and isinstance(key, ecdsa.ECDSA384P1) or
+ pub_key is not None and isinstance(pub_key,
+ ecdsa.ECDSA384P1Public)):
+ hash_algorithm = hashlib.sha384
+ hash_tlv = "SHA384"
+ else:
+ hash_algorithm = hashlib.sha256
+ hash_tlv = "SHA256"
# Calculate the hash of the public key
if key is not None:
pub = key.get_public_bytes()
- sha = hashlib.sha256()
+ sha = hash_algorithm()
sha.update(pub)
pubbytes = sha.digest()
elif pub_key is not None:
if hasattr(pub_key, 'sign'):
print(os.path.basename(__file__) + ": sign the payload")
pub = pub_key.get_public_bytes()
- sha = hashlib.sha256()
+ sha = hash_algorithm()
sha.update(pub)
pubbytes = sha.digest()
else:
@@ -354,11 +371,11 @@
# before it is even calculated. For this reason the script fills
# this field with zeros and the bootloader will insert the right
# value later.
- digest = bytes(hashlib.sha256().digest_size)
+ digest = bytes(hash_algorithm().digest_size)
# Create CBOR encoded boot record
boot_record = create_sw_component_data(sw_type, image_version,
- "SHA256", digest,
+ hash_tlv, digest,
pubbytes)
protected_tlv_size += TLV_SIZE + len(boot_record)
@@ -435,11 +452,10 @@
# Note that ecdsa wants to do the hashing itself, which means
# we get to hash it twice.
- sha = hashlib.sha256()
+ sha = hash_algorithm()
sha.update(self.payload)
digest = sha.digest()
-
- tlv.add('SHA256', digest)
+ tlv.add(hash_tlv, digest)
if vector_to_sign == 'payload':
# Stop amending data to the image
@@ -458,8 +474,9 @@
tlv.add('PUBKEY', pub)
if key is not None and fixed_sig is None:
- # `sign` expects the full image payload (sha256 done internally),
- # while `sign_digest` expects only the digest of the payload
+ # `sign` expects the full image payload (hashing done
+ # internally), while `sign_digest` expects only the digest
+ # of the payload
if hasattr(key, 'sign'):
print(os.path.basename(__file__) + ": sign the payload")
@@ -551,17 +568,18 @@
) # }
assert struct.calcsize(fmt) == IMAGE_HEADER_SIZE
header = struct.pack(fmt,
- IMAGE_MAGIC,
- self.rom_fixed or self.load_addr,
- self.header_size,
- protected_tlv_size, # TLV Info header + Protected TLVs
- len(self.payload) - self.header_size, # ImageSz
- flags,
- self.version.major,
- self.version.minor or 0,
- self.version.revision or 0,
- self.version.build or 0,
- 0) # Pad1
+ IMAGE_MAGIC,
+ self.rom_fixed or self.load_addr,
+ self.header_size,
+ protected_tlv_size, # TLV Info header +
+ # Protected TLVs
+ len(self.payload) - self.header_size, # ImageSz
+ flags,
+ self.version.major,
+ self.version.minor or 0,
+ self.version.revision or 0,
+ self.version.build or 0,
+ 0) # Pad1
self.payload = bytearray(self.payload)
self.payload[:len(header)] = header
@@ -627,7 +645,13 @@
if magic != TLV_INFO_MAGIC:
return VerifyResult.INVALID_TLV_INFO_MAGIC, None, None
- sha = hashlib.sha256()
+ if isinstance(key, ecdsa.ECDSA384P1Public):
+ sha = hashlib.sha384()
+ hash_tlv = "SHA384"
+ else:
+ sha = hashlib.sha256()
+ hash_tlv = "SHA256"
+
prot_tlv_size = tlv_off
sha.update(b[:prot_tlv_size])
digest = sha.digest()
@@ -637,7 +661,7 @@
while tlv_off < tlv_end:
tlv = b[tlv_off:tlv_off+TLV_SIZE]
tlv_type, _, tlv_len = struct.unpack('BBH', tlv)
- if tlv_type == TLV_VALUES["SHA256"]:
+ if tlv_type == TLV_VALUES[hash_tlv]:
off = tlv_off + TLV_SIZE
if digest == b[off:off+tlv_len]:
if key is None:
diff --git a/scripts/imgtool/keys/__init__.py b/scripts/imgtool/keys/__init__.py
index dfd101d..ed2fed5 100644
--- a/scripts/imgtool/keys/__init__.py
+++ b/scripts/imgtool/keys/__init__.py
@@ -1,4 +1,5 @@
# Copyright 2017 Linaro Limited
+# Copyright 2023 Arm Limited
#
# SPDX-License-Identifier: Apache-2.0
#
@@ -30,7 +31,8 @@
X25519PrivateKey, X25519PublicKey)
from .rsa import RSA, RSAPublic, RSAUsageError, RSA_KEY_SIZES
-from .ecdsa import ECDSA256P1, ECDSA256P1Public, ECDSAUsageError
+from .ecdsa import (ECDSA256P1, ECDSA256P1Public,
+ ECDSA384P1, ECDSA384P1Public, ECDSAUsageError)
from .ed25519 import Ed25519, Ed25519Public, Ed25519UsageError
from .x25519 import X25519, X25519Public, X25519UsageError
@@ -42,7 +44,8 @@
def load(path, passwd=None):
- """Try loading a key from the given path. Returns None if the password wasn't specified."""
+ """Try loading a key from the given path.
+ Returns None if the password wasn't specified."""
with open(path, 'rb') as f:
raw_pem = f.read()
try:
@@ -73,17 +76,23 @@
raise Exception("Unsupported RSA key size: " + pk.key_size)
return RSAPublic(pk)
elif isinstance(pk, EllipticCurvePrivateKey):
- if pk.curve.name != 'secp256r1':
+ if pk.curve.name not in ('secp256r1', 'secp384r1'):
raise Exception("Unsupported EC curve: " + pk.curve.name)
- if pk.key_size != 256:
+ if pk.key_size not in (256, 384):
raise Exception("Unsupported EC size: " + pk.key_size)
- return ECDSA256P1(pk)
+ if pk.curve.name == 'secp256r1':
+ return ECDSA256P1(pk)
+ elif pk.curve.name == 'secp384r1':
+ return ECDSA384P1(pk)
elif isinstance(pk, EllipticCurvePublicKey):
- if pk.curve.name != 'secp256r1':
+ if pk.curve.name not in ('secp256r1', 'secp384r1'):
raise Exception("Unsupported EC curve: " + pk.curve.name)
- if pk.key_size != 256:
+ if pk.key_size not in (256, 384):
raise Exception("Unsupported EC size: " + pk.key_size)
- return ECDSA256P1Public(pk)
+ if pk.curve.name == 'secp256r1':
+ return ECDSA256P1Public(pk)
+ elif pk.curve.name == 'secp384r1':
+ return ECDSA384P1Public(pk)
elif isinstance(pk, Ed25519PrivateKey):
return Ed25519(pk)
elif isinstance(pk, Ed25519PublicKey):
diff --git a/scripts/imgtool/keys/ecdsa.py b/scripts/imgtool/keys/ecdsa.py
index addceb2..b70153c 100644
--- a/scripts/imgtool/keys/ecdsa.py
+++ b/scripts/imgtool/keys/ecdsa.py
@@ -4,11 +4,12 @@
# SPDX-License-Identifier: Apache-2.0
import os.path
+import hashlib
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import ec
-from cryptography.hazmat.primitives.hashes import SHA256
+from cryptography.hazmat.primitives.hashes import SHA256, SHA384
from .general import KeyClass
from .privatebytes import PrivateBytesMixin
@@ -18,18 +19,18 @@
pass
-class ECDSA256P1Public(KeyClass):
+class ECDSAPublicKey(KeyClass):
+ """
+ Wrapper around an ECDSA public key.
+ """
def __init__(self, key):
self.key = key
- def shortname(self):
- return "ecdsa"
-
def _unsupported(self, name):
raise ECDSAUsageError("Operation {} requires private key".format(name))
def _get_public(self):
- return self.key
+ return self.key.public_key()
def get_public_bytes(self):
# The key is embedded into MBUboot in "SubjectPublicKeyInfo" format
@@ -56,55 +57,13 @@
with open(path, 'wb') as f:
f.write(pem)
- def sig_type(self):
- return "ECDSA256_SHA256"
- def sig_tlv(self):
- return "ECDSA256"
-
- def sig_len(self):
- # Early versions of MCUboot (< v1.5.0) required ECDSA
- # signatures to be padded to 72 bytes. Because the DER
- # encoding is done with signed integers, the size of the
- # signature will vary depending on whether the high bit is set
- # in each value. This padding was done in a
- # not-easily-reversible way (by just adding zeros).
- #
- # The signing code no longer requires this padding, and newer
- # versions of MCUboot don't require it. But, continue to
- # return the total length so that the padding can be done if
- # requested.
- return 72
-
- def verify(self, signature, payload):
- # strip possible paddings added during sign
- signature = signature[:signature[1] + 2]
- k = self.key
- if isinstance(self.key, ec.EllipticCurvePrivateKey):
- k = self.key.public_key()
- return k.verify(signature=signature, data=payload,
- signature_algorithm=ec.ECDSA(SHA256()))
-
-
-class ECDSA256P1(ECDSA256P1Public, PrivateBytesMixin):
+class ECDSAPrivateKey(PrivateBytesMixin):
"""
Wrapper around an ECDSA private key.
"""
-
def __init__(self, key):
- """key should be an instance of EllipticCurvePrivateKey"""
self.key = key
- self.pad_sig = False
-
- @staticmethod
- def generate():
- pk = ec.generate_private_key(
- ec.SECP256R1(),
- backend=default_backend())
- return ECDSA256P1(pk)
-
- def _get_public(self):
- return self.key.public_key()
def _build_minimal_ecdsa_privkey(self, der, format):
'''
@@ -154,13 +113,14 @@
'pkcs8': serialization.PrivateFormat.PKCS8,
'openssl': serialization.PrivateFormat.TraditionalOpenSSL
}
- _DEFAULT_FORMAT='pkcs8'
+ _DEFAULT_FORMAT = 'pkcs8'
def get_private_bytes(self, minimal, format):
- format, priv = self._get_private_bytes(minimal, format, ECDSAUsageError)
+ format, priv = self._get_private_bytes(minimal,
+ format, ECDSAUsageError)
if minimal:
- priv = self._build_minimal_ecdsa_privkey(priv,
- self._VALID_FORMATS[format])
+ priv = self._build_minimal_ecdsa_privkey(
+ priv, self._VALID_FORMATS[format])
return priv
def export_private(self, path, passwd=None):
@@ -177,6 +137,64 @@
with open(path, 'wb') as f:
f.write(pem)
+
+class ECDSA256P1Public(ECDSAPublicKey):
+ """
+ Wrapper around an ECDSA (p256) public key.
+ """
+ def __init__(self, key):
+ super().__init__(key)
+ self.key = key
+
+ def shortname(self):
+ return "ecdsa"
+
+ def sig_type(self):
+ return "ECDSA256_SHA256"
+
+ def sig_tlv(self):
+ return "ECDSASIG"
+
+ def sig_len(self):
+ # Early versions of MCUboot (< v1.5.0) required ECDSA
+ # signatures to be padded to 72 bytes. Because the DER
+ # encoding is done with signed integers, the size of the
+ # signature will vary depending on whether the high bit is set
+ # in each value. This padding was done in a
+ # not-easily-reversible way (by just adding zeros).
+ #
+ # The signing code no longer requires this padding, and newer
+ # versions of MCUboot don't require it. But, continue to
+ # return the total length so that the padding can be done if
+ # requested.
+ return 72
+
+ def verify(self, signature, payload):
+ # strip possible paddings added during sign
+ signature = signature[:signature[1] + 2]
+ k = self.key
+ if isinstance(self.key, ec.EllipticCurvePrivateKey):
+ k = self.key.public_key()
+ return k.verify(signature=signature, data=payload,
+ signature_algorithm=ec.ECDSA(SHA256()))
+
+
+class ECDSA256P1(ECDSA256P1Public, ECDSAPrivateKey):
+ """
+ Wrapper around an ECDSA (p256) private key.
+ """
+ def __init__(self, key):
+ super().__init__(key)
+ self.key = key
+ self.pad_sig = False
+
+ @staticmethod
+ def generate():
+ pk = ec.generate_private_key(
+ ec.SECP256R1(),
+ backend=default_backend())
+ return ECDSA256P1(pk)
+
def raw_sign(self, payload):
"""Return the actual signature"""
return self.key.sign(
@@ -191,3 +209,78 @@
return sig
else:
return sig
+
+
+class ECDSA384P1Public(ECDSAPublicKey):
+ """
+ Wrapper around an ECDSA (p384) public key.
+ """
+ def __init__(self, key):
+ super().__init__(key)
+ self.key = key
+
+ def shortname(self):
+ return "ecdsap384"
+
+ def sig_type(self):
+ return "ECDSA384_SHA384"
+
+ def sig_tlv(self):
+ return "ECDSASIG"
+
+ def sig_len(self):
+ # Early versions of MCUboot (< v1.5.0) required ECDSA
+ # signatures to be padded to a fixed length. Because the DER
+ # encoding is done with signed integers, the size of the
+ # signature will vary depending on whether the high bit is set
+ # in each value. This padding was done in a
+ # not-easily-reversible way (by just adding zeros).
+ #
+ # The signing code no longer requires this padding, and newer
+ # versions of MCUboot don't require it. But, continue to
+ # return the total length so that the padding can be done if
+ # requested.
+ return 103
+
+ def verify(self, signature, payload):
+ # strip possible paddings added during sign
+ signature = signature[:signature[1] + 2]
+ k = self.key
+ if isinstance(self.key, ec.EllipticCurvePrivateKey):
+ k = self.key.public_key()
+ return k.verify(signature=signature, data=payload,
+ signature_algorithm=ec.ECDSA(SHA384()))
+
+
+class ECDSA384P1(ECDSA384P1Public, ECDSAPrivateKey):
+ """
+ Wrapper around an ECDSA (p384) private key.
+ """
+
+ def __init__(self, key):
+ """key should be an instance of EllipticCurvePrivateKey"""
+ super().__init__(key)
+ self.key = key
+ self.pad_sig = False
+
+ @staticmethod
+ def generate():
+ pk = ec.generate_private_key(
+ ec.SECP384R1(),
+ backend=default_backend())
+ return ECDSA384P1(pk)
+
+ def raw_sign(self, payload):
+ """Return the actual signature"""
+ return self.key.sign(
+ data=payload,
+ signature_algorithm=ec.ECDSA(SHA384()))
+
+ def sign(self, payload):
+ sig = self.raw_sign(payload)
+ if self.pad_sig:
+ # To make fixed length, pad with one or two zeros.
+ sig += b'\000' * (self.sig_len() - len(sig))
+ return sig
+ else:
+ return sig
diff --git a/scripts/imgtool/main.py b/scripts/imgtool/main.py
index 2df06e1..eba557f 100755
--- a/scripts/imgtool/main.py
+++ b/scripts/imgtool/main.py
@@ -48,6 +48,10 @@
keys.ECDSA256P1.generate().export_private(keyfile, passwd=passwd)
+def gen_ecdsa_p384(keyfile, passwd):
+ keys.ECDSA384P1.generate().export_private(keyfile, passwd=passwd)
+
+
def gen_ed25519(keyfile, passwd):
keys.Ed25519.generate().export_private(path=keyfile, passwd=passwd)
@@ -62,6 +66,7 @@
'rsa-2048': gen_rsa2048,
'rsa-3072': gen_rsa3072,
'ecdsa-p256': gen_ecdsa_p256,
+ 'ecdsa-p384': gen_ecdsa_p384,
'ed25519': gen_ed25519,
'x25519': gen_x25519,
}
@@ -183,7 +188,7 @@
elif ret == image.VerifyResult.INVALID_TLV_INFO_MAGIC:
print("Invalid TLV info magic; is this an MCUboot image?")
elif ret == image.VerifyResult.INVALID_HASH:
- print("Image has an invalid sha256 digest")
+ print("Image has an invalid hash")
elif ret == image.VerifyResult.INVALID_SIGNATURE:
print("No signature found for the given key")
else:
@@ -384,6 +389,8 @@
if enckey and key:
if ((isinstance(key, keys.ECDSA256P1) and
not isinstance(enckey, keys.ECDSA256P1Public))
+ or (isinstance(key, keys.ECDSA384P1) and
+ not isinstance(enckey, keys.ECDSA384P1Public))
or (isinstance(key, keys.RSA) and
not isinstance(enckey, keys.RSAPublic))):
# FIXME