9 files changed, 988 insertions, 0 deletions
diff --git a/tools/mcuboot/imgtool/keys/__init__.py b/tools/mcuboot/imgtool/keys/__init__.py
new file mode 100644
index 00000000..f25e2aae
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/__init__.py
@@ -0,0 +1,94 @@
+# Copyright 2017 Linaro Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Cryptographic key management for imgtool.
+"""
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric.rsa import (
+    RSAPrivateKey, RSAPublicKey)
+from cryptography.hazmat.primitives.asymmetric.ec import (
+    EllipticCurvePrivateKey, EllipticCurvePublicKey)
+from cryptography.hazmat.primitives.asymmetric.ed25519 import (
+    Ed25519PrivateKey, Ed25519PublicKey)
+from cryptography.hazmat.primitives.asymmetric.x25519 import (
+    X25519PrivateKey, X25519PublicKey)
+
+from .rsa import RSA, RSAPublic, RSAUsageError, RSA_KEY_SIZES
+from .ecdsa import ECDSA256P1, ECDSA256P1Public, ECDSAUsageError
+from .ed25519 import Ed25519, Ed25519Public, Ed25519UsageError
+from .x25519 import X25519, X25519Public, X25519UsageError
+
+
+class PasswordRequired(Exception):
+    """Raised to indicate that the key is password protected, but a
+    password was not specified."""
+    pass
+
+
+def load(path, passwd=None):
+    """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:
+        pk = serialization.load_pem_private_key(
+            raw_pem,
+            password=passwd,
+            backend=default_backend())
+    # Unfortunately, the crypto library raises unhelpful exceptions,
+    # so we have to look at the text.
+    except TypeError as e:
+        msg = str(e)
+        if "private key is encrypted" in msg:
+            return None
+        raise e
+    except ValueError:
+        # This seems to happen if the key is a public key, let's try
+        # loading it as a public key.
+        pk = serialization.load_pem_public_key(
+            raw_pem,
+            backend=default_backend())
+
+    if isinstance(pk, RSAPrivateKey):
+        if pk.key_size not in RSA_KEY_SIZES:
+            raise Exception("Unsupported RSA key size: " + pk.key_size)
+        return RSA(pk)
+    elif isinstance(pk, RSAPublicKey):
+        if pk.key_size not in RSA_KEY_SIZES:
+            raise Exception("Unsupported RSA key size: " + pk.key_size)
+        return RSAPublic(pk)
+    elif isinstance(pk, EllipticCurvePrivateKey):
+        if pk.curve.name != 'secp256r1':
+            raise Exception("Unsupported EC curve: " + pk.curve.name)
+        if pk.key_size != 256:
+            raise Exception("Unsupported EC size: " + pk.key_size)
+        return ECDSA256P1(pk)
+    elif isinstance(pk, EllipticCurvePublicKey):
+        if pk.curve.name != 'secp256r1':
+            raise Exception("Unsupported EC curve: " + pk.curve.name)
+        if pk.key_size != 256:
+            raise Exception("Unsupported EC size: " + pk.key_size)
+        return ECDSA256P1Public(pk)
+    elif isinstance(pk, Ed25519PrivateKey):
+        return Ed25519(pk)
+    elif isinstance(pk, Ed25519PublicKey):
+        return Ed25519Public(pk)
+    elif isinstance(pk, X25519PrivateKey):
+        return X25519(pk)
+    elif isinstance(pk, X25519PublicKey):
+        return X25519Public(pk)
+    else:
+        raise Exception("Unknown key type: " + str(type(pk)))
diff --git a/tools/mcuboot/imgtool/keys/ecdsa.py b/tools/mcuboot/imgtool/keys/ecdsa.py
new file mode 100644
index 00000000..139d583d
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/ecdsa.py
@@ -0,0 +1,157 @@
+"""
+ECDSA key management
+"""
+
+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 .general import KeyClass
+
+class ECDSAUsageError(Exception):
+    pass
+
+class ECDSA256P1Public(KeyClass):
+    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
+
+    def get_public_bytes(self):
+        # The key is embedded into MBUboot in "SubjectPublicKeyInfo" format
+        return self._get_public().public_bytes(
+            encoding=serialization.Encoding.DER,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo)
+
+    def get_private_bytes(self, minimal):
+        self._unsupported('get_private_bytes')
+
+    def export_private(self, path, passwd=None):
+        self._unsupported('export_private')
+
+    def export_public(self, path):
+        """Write the public key to the given file."""
+        pem = self._get_public().public_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo)
+        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):
+    """
+    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):
+        '''
+        Builds a new DER that only includes the EC private key, removing the
+        public key that is added as an "optional" BITSTRING.
+        '''
+        offset_PUB = 68
+        EXCEPTION_TEXT = "Error parsing ecdsa key. Please submit an issue!"
+        if der[offset_PUB] != 0xa1:
+            raise ECDSAUsageError(EXCEPTION_TEXT)
+        len_PUB = der[offset_PUB + 1]
+        b = bytearray(der[:-offset_PUB])
+        offset_SEQ = 29
+        if b[offset_SEQ] != 0x30:
+            raise ECDSAUsageError(EXCEPTION_TEXT)
+        b[offset_SEQ + 1] -= len_PUB
+        offset_OCT_STR = 27
+        if b[offset_OCT_STR] != 0x04:
+            raise ECDSAUsageError(EXCEPTION_TEXT)
+        b[offset_OCT_STR + 1] -= len_PUB
+        if b[0] != 0x30 or b[1] != 0x81:
+            raise ECDSAUsageError(EXCEPTION_TEXT)
+        b[2] -= len_PUB
+        return b
+
+    def get_private_bytes(self, minimal):
+        priv = self.key.private_bytes(
+            encoding=serialization.Encoding.DER,
+            format=serialization.PrivateFormat.PKCS8,
+            encryption_algorithm=serialization.NoEncryption())
+        if minimal:
+            priv = self._build_minimal_ecdsa_privkey(priv)
+        return priv
+
+    def export_private(self, path, passwd=None):
+        """Write the private key to the given file, protecting it with the optional password."""
+        if passwd is None:
+            enc = serialization.NoEncryption()
+        else:
+            enc = serialization.BestAvailableEncryption(passwd)
+        pem = self.key.private_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PrivateFormat.PKCS8,
+            encryption_algorithm=enc)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def raw_sign(self, payload):
+        """Return the actual signature"""
+        return self.key.sign(
+            data=payload,
+            signature_algorithm=ec.ECDSA(SHA256()))
+
+    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/tools/mcuboot/imgtool/keys/ecdsa_test.py b/tools/mcuboot/imgtool/keys/ecdsa_test.py
new file mode 100644
index 00000000..7982cad9
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/ecdsa_test.py
@@ -0,0 +1,99 @@
+"""
+Tests for ECDSA keys
+"""
+
+import io
+import os.path
+import sys
+import tempfile
+import unittest
+
+from cryptography.exceptions import InvalidSignature
+from cryptography.hazmat.primitives.asymmetric import ec
+from cryptography.hazmat.primitives.hashes import SHA256
+
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '../..')))
+
+from imgtool.keys import load, ECDSA256P1, ECDSAUsageError
+
+class EcKeyGeneration(unittest.TestCase):
+
+    def setUp(self):
+        self.test_dir = tempfile.TemporaryDirectory()
+
+    def tname(self, base):
+        return os.path.join(self.test_dir.name, base)
+
+    def tearDown(self):
+        self.test_dir.cleanup()
+
+    def test_keygen(self):
+        name1 = self.tname("keygen.pem")
+        k = ECDSA256P1.generate()
+        k.export_private(name1, b'secret')
+
+        self.assertIsNone(load(name1))
+
+        k2 = load(name1, b'secret')
+
+        pubname = self.tname('keygen-pub.pem')
+        k2.export_public(pubname)
+        pk2 = load(pubname)
+
+        # We should be able to export the public key from the loaded
+        # public key, but not the private key.
+        pk2.export_public(self.tname('keygen-pub2.pem'))
+        self.assertRaises(ECDSAUsageError,
+                          pk2.export_private, self.tname('keygen-priv2.pem'))
+
+    def test_emit(self):
+        """Basic sanity check on the code emitters."""
+        k = ECDSA256P1.generate()
+
+        ccode = io.StringIO()
+        k.emit_c_public(ccode)
+        self.assertIn("ecdsa_pub_key", ccode.getvalue())
+        self.assertIn("ecdsa_pub_key_len", ccode.getvalue())
+
+        rustcode = io.StringIO()
+        k.emit_rust_public(rustcode)
+        self.assertIn("ECDSA_PUB_KEY", rustcode.getvalue())
+
+    def test_emit_pub(self):
+        """Basic sanity check on the code emitters."""
+        pubname = self.tname("public.pem")
+        k = ECDSA256P1.generate()
+        k.export_public(pubname)
+
+        k2 = load(pubname)
+
+        ccode = io.StringIO()
+        k2.emit_c_public(ccode)
+        self.assertIn("ecdsa_pub_key", ccode.getvalue())
+        self.assertIn("ecdsa_pub_key_len", ccode.getvalue())
+
+        rustcode = io.StringIO()
+        k2.emit_rust_public(rustcode)
+        self.assertIn("ECDSA_PUB_KEY", rustcode.getvalue())
+
+    def test_sig(self):
+        k = ECDSA256P1.generate()
+        buf = b'This is the message'
+        sig = k.raw_sign(buf)
+
+        # The code doesn't have any verification, so verify this
+        # manually.
+        k.key.public_key().verify(
+            signature=sig,
+            data=buf,
+            signature_algorithm=ec.ECDSA(SHA256()))
+
+        # Modify the message to make sure the signature fails.
+        self.assertRaises(InvalidSignature,
+                          k.key.public_key().verify,
+                          signature=sig,
+                          data=b'This is thE message',
+                          signature_algorithm=ec.ECDSA(SHA256()))
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tools/mcuboot/imgtool/keys/ed25519.py b/tools/mcuboot/imgtool/keys/ed25519.py
new file mode 100644
index 00000000..fb000cd9
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/ed25519.py
@@ -0,0 +1,105 @@
+"""
+ED25519 key management
+"""
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric import ed25519
+
+from .general import KeyClass
+
+
+class Ed25519UsageError(Exception):
+    pass
+
+
+class Ed25519Public(KeyClass):
+    def __init__(self, key):
+        self.key = key
+
+    def shortname(self):
+        return "ed25519"
+
+    def _unsupported(self, name):
+        raise Ed25519UsageError("Operation {} requires private key".format(name))
+
+    def _get_public(self):
+        return self.key
+
+    def get_public_bytes(self):
+        # The key is embedded into MBUboot in "SubjectPublicKeyInfo" format
+        return self._get_public().public_bytes(
+            encoding=serialization.Encoding.DER,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo)
+
+    def get_private_bytes(self, minimal):
+        self._unsupported('get_private_bytes')
+
+    def export_private(self, path, passwd=None):
+        self._unsupported('export_private')
+
+    def export_public(self, path):
+        """Write the public key to the given file."""
+        pem = self._get_public().public_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def sig_type(self):
+        return "ED25519"
+
+    def sig_tlv(self):
+        return "ED25519"
+
+    def sig_len(self):
+        return 64
+
+
+class Ed25519(Ed25519Public):
+    """
+    Wrapper around an ED25519 private key.
+    """
+
+    def __init__(self, key):
+        """key should be an instance of EllipticCurvePrivateKey"""
+        self.key = key
+
+    @staticmethod
+    def generate():
+        pk = ed25519.Ed25519PrivateKey.generate()
+        return Ed25519(pk)
+
+    def _get_public(self):
+        return self.key.public_key()
+
+    def get_private_bytes(self, minimal):
+        raise Ed25519UsageError("Operation not supported with {} keys".format(
+            self.shortname()))
+
+    def export_private(self, path, passwd=None):
+        """
+        Write the private key to the given file, protecting it with the
+        optional password.
+        """
+        if passwd is None:
+            enc = serialization.NoEncryption()
+        else:
+            enc = serialization.BestAvailableEncryption(passwd)
+        pem = self.key.private_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PrivateFormat.PKCS8,
+            encryption_algorithm=enc)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def sign_digest(self, digest):
+        """Return the actual signature"""
+        return self.key.sign(data=digest)
+
+    def verify_digest(self, signature, digest):
+        """Verify that signature is valid for given digest"""
+        k = self.key
+        if isinstance(self.key, ed25519.Ed25519PrivateKey):
+            k = self.key.public_key()
+        return k.verify(signature=signature, data=digest)
diff --git a/tools/mcuboot/imgtool/keys/ed25519_test.py b/tools/mcuboot/imgtool/keys/ed25519_test.py
new file mode 100644
index 00000000..31f43fe9
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/ed25519_test.py
@@ -0,0 +1,103 @@
+"""
+Tests for ECDSA keys
+"""
+
+import hashlib
+import io
+import os.path
+import sys
+import tempfile
+import unittest
+
+from cryptography.exceptions import InvalidSignature
+from cryptography.hazmat.primitives.asymmetric import ed25519
+
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '../..')))
+
+from imgtool.keys import load, Ed25519, Ed25519UsageError
+
+
+class Ed25519KeyGeneration(unittest.TestCase):
+
+    def setUp(self):
+        self.test_dir = tempfile.TemporaryDirectory()
+
+    def tname(self, base):
+        return os.path.join(self.test_dir.name, base)
+
+    def tearDown(self):
+        self.test_dir.cleanup()
+
+    def test_keygen(self):
+        name1 = self.tname("keygen.pem")
+        k = Ed25519.generate()
+        k.export_private(name1, b'secret')
+
+        self.assertIsNone(load(name1))
+
+        k2 = load(name1, b'secret')
+
+        pubname = self.tname('keygen-pub.pem')
+        k2.export_public(pubname)
+        pk2 = load(pubname)
+
+        # We should be able to export the public key from the loaded
+        # public key, but not the private key.
+        pk2.export_public(self.tname('keygen-pub2.pem'))
+        self.assertRaises(Ed25519UsageError,
+                          pk2.export_private, self.tname('keygen-priv2.pem'))
+
+    def test_emit(self):
+        """Basic sanity check on the code emitters."""
+        k = Ed25519.generate()
+
+        ccode = io.StringIO()
+        k.emit_c_public(ccode)
+        self.assertIn("ed25519_pub_key", ccode.getvalue())
+        self.assertIn("ed25519_pub_key_len", ccode.getvalue())
+
+        rustcode = io.StringIO()
+        k.emit_rust_public(rustcode)
+        self.assertIn("ED25519_PUB_KEY", rustcode.getvalue())
+
+    def test_emit_pub(self):
+        """Basic sanity check on the code emitters."""
+        pubname = self.tname("public.pem")
+        k = Ed25519.generate()
+        k.export_public(pubname)
+
+        k2 = load(pubname)
+
+        ccode = io.StringIO()
+        k2.emit_c_public(ccode)
+        self.assertIn("ed25519_pub_key", ccode.getvalue())
+        self.assertIn("ed25519_pub_key_len", ccode.getvalue())
+
+        rustcode = io.StringIO()
+        k2.emit_rust_public(rustcode)
+        self.assertIn("ED25519_PUB_KEY", rustcode.getvalue())
+
+    def test_sig(self):
+        k = Ed25519.generate()
+        buf = b'This is the message'
+        sha = hashlib.sha256()
+        sha.update(buf)
+        digest = sha.digest()
+        sig = k.sign_digest(digest)
+
+        # The code doesn't have any verification, so verify this
+        # manually.
+        k.key.public_key().verify(signature=sig, data=digest)
+
+        # Modify the message to make sure the signature fails.
+        sha = hashlib.sha256()
+        sha.update(b'This is thE message')
+        new_digest = sha.digest()
+        self.assertRaises(InvalidSignature,
+                          k.key.public_key().verify,
+                          signature=sig,
+                          data=new_digest)
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tools/mcuboot/imgtool/keys/general.py b/tools/mcuboot/imgtool/keys/general.py
new file mode 100644
index 00000000..ce7a2d26
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/general.py
@@ -0,0 +1,45 @@
+"""General key class."""
+
+import sys
+
+AUTOGEN_MESSAGE = "/* Autogenerated by imgtool.py, do not edit. */"
+
+class KeyClass(object):
+    def _emit(self, header, trailer, encoded_bytes, indent, file=sys.stdout, len_format=None):
+        print(AUTOGEN_MESSAGE, file=file)
+        print(header, end='', file=file)
+        for count, b in enumerate(encoded_bytes):
+            if count % 8 == 0:
+                print("\n" + indent, end='', file=file)
+            else:
+                print(" ", end='', file=file)
+            print("0x{:02x},".format(b), end='', file=file)
+        print("\n" + trailer, file=file)
+        if len_format is not None:
+            print(len_format.format(len(encoded_bytes)), file=file)
+
+    def emit_c_public(self, file=sys.stdout):
+        self._emit(
+            header="const unsigned char {}_pub_key[] = {{".format(self.shortname()),
+            trailer="};",
+            encoded_bytes=self.get_public_bytes(),
+            indent="    ",
+            len_format="const unsigned int {}_pub_key_len = {{}};".format(self.shortname()),
+            file=file)
+
+    def emit_rust_public(self, file=sys.stdout):
+        self._emit(
+            header="static {}_PUB_KEY: &'static [u8] = &[".format(self.shortname().upper()),
+            trailer="];",
+            encoded_bytes=self.get_public_bytes(),
+            indent="    ",
+            file=file)
+
+    def emit_private(self, minimal, file=sys.stdout):
+        self._emit(
+            header="const unsigned char enc_priv_key[] = {",
+            trailer="};",
+            encoded_bytes=self.get_private_bytes(minimal),
+            indent="    ",
+            len_format="const unsigned int enc_priv_key_len = {};",
+            file=file)
diff --git a/tools/mcuboot/imgtool/keys/rsa.py b/tools/mcuboot/imgtool/keys/rsa.py
new file mode 100644
index 00000000..f8273bf5
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/rsa.py
@@ -0,0 +1,163 @@
+"""
+RSA Key management
+"""
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography.hazmat.primitives.asymmetric.padding import PSS, MGF1
+from cryptography.hazmat.primitives.hashes import SHA256
+
+from .general import KeyClass
+
+
+# Sizes that bootutil will recognize
+RSA_KEY_SIZES = [2048, 3072]
+
+
+class RSAUsageError(Exception):
+    pass
+
+
+class RSAPublic(KeyClass):
+    """The public key can only do a few operations"""
+    def __init__(self, key):
+        self.key = key
+
+    def key_size(self):
+        return self.key.key_size
+
+    def shortname(self):
+        return "rsa"
+
+    def _unsupported(self, name):
+        raise RSAUsageError("Operation {} requires private key".format(name))
+
+    def _get_public(self):
+        return self.key
+
+    def get_public_bytes(self):
+        # The key embedded into MCUboot is in PKCS1 format.
+        return self._get_public().public_bytes(
+            encoding=serialization.Encoding.DER,
+            format=serialization.PublicFormat.PKCS1)
+
+    def get_private_bytes(self, minimal):
+        self._unsupported('get_private_bytes')
+
+    def export_private(self, path, passwd=None):
+        self._unsupported('export_private')
+
+    def export_public(self, path):
+        """Write the public key to the given file."""
+        pem = self._get_public().public_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def sig_type(self):
+        return "PKCS1_PSS_RSA{}_SHA256".format(self.key_size())
+
+    def sig_tlv(self):
+        return"RSA{}".format(self.key_size())
+
+    def sig_len(self):
+        return self.key_size() / 8
+
+    def verify(self, signature, payload):
+        k = self.key
+        if isinstance(self.key, rsa.RSAPrivateKey):
+            k = self.key.public_key()
+        return k.verify(signature=signature, data=payload,
+                        padding=PSS(mgf=MGF1(SHA256()), salt_length=32),
+                        algorithm=SHA256())
+
+
+class RSA(RSAPublic):
+    """
+    Wrapper around an RSA key, with imgtool support.
+    """
+
+    def __init__(self, key):
+        """The key should be a private key from cryptography"""
+        self.key = key
+
+    @staticmethod
+    def generate(key_size=2048):
+        if key_size not in RSA_KEY_SIZES:
+            raise RSAUsageError("Key size {} is not supported by MCUboot"
+                                .format(key_size))
+        pk = rsa.generate_private_key(
+            public_exponent=65537,
+            key_size=key_size,
+            backend=default_backend())
+        return RSA(pk)
+
+    def _get_public(self):
+        return self.key.public_key()
+
+    def _build_minimal_rsa_privkey(self, der):
+        '''
+        Builds a new DER that only includes N/E/D/P/Q RSA parameters;
+        standard DER private bytes provided by OpenSSL also includes
+        CRT params (DP/DQ/QP) which can be removed.
+        '''
+        OFFSET_N = 7  # N is always located at this offset
+        b = bytearray(der)
+        off = OFFSET_N
+        if b[off + 1] != 0x82:
+            raise RSAUsageError("Error parsing N while minimizing")
+        len_N = (b[off + 2] << 8) + b[off + 3] + 4
+        off += len_N
+        if b[off + 1] != 0x03:
+            raise RSAUsageError("Error parsing E while minimizing")
+        len_E = b[off + 2] + 4
+        off += len_E
+        if b[off + 1] != 0x82:
+            raise RSAUsageError("Error parsing D while minimizing")
+        len_D = (b[off + 2] << 8) + b[off + 3] + 4
+        off += len_D
+        if b[off + 1] != 0x81:
+            raise RSAUsageError("Error parsing P while minimizing")
+        len_P = b[off + 2] + 3
+        off += len_P
+        if b[off + 1] != 0x81:
+            raise RSAUsageError("Error parsing Q while minimizing")
+        len_Q = b[off + 2] + 3
+        off += len_Q
+        # adjust DER size for removed elements
+        b[2] = (off - 4) >> 8
+        b[3] = (off - 4) & 0xff
+        return b[:off]
+
+    def get_private_bytes(self, minimal):
+        priv = self.key.private_bytes(
+            encoding=serialization.Encoding.DER,
+            format=serialization.PrivateFormat.TraditionalOpenSSL,
+            encryption_algorithm=serialization.NoEncryption())
+        if minimal:
+            priv = self._build_minimal_rsa_privkey(priv)
+        return priv
+
+    def export_private(self, path, passwd=None):
+        """Write the private key to the given file, protecting it with the
+        optional password."""
+        if passwd is None:
+            enc = serialization.NoEncryption()
+        else:
+            enc = serialization.BestAvailableEncryption(passwd)
+        pem = self.key.private_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PrivateFormat.PKCS8,
+            encryption_algorithm=enc)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def sign(self, payload):
+        # The verification code only allows the salt length to be the
+        # same as the hash length, 32.
+        return self.key.sign(
+            data=payload,
+            padding=PSS(mgf=MGF1(SHA256()), salt_length=32),
+            algorithm=SHA256())
diff --git a/tools/mcuboot/imgtool/keys/rsa_test.py b/tools/mcuboot/imgtool/keys/rsa_test.py
new file mode 100644
index 00000000..b0afa835
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/rsa_test.py
@@ -0,0 +1,115 @@
+"""
+Tests for RSA keys
+"""
+
+import io
+import os
+import sys
+import tempfile
+import unittest
+
+from cryptography.exceptions import InvalidSignature
+from cryptography.hazmat.primitives.asymmetric.padding import PSS, MGF1
+from cryptography.hazmat.primitives.hashes import SHA256
+
+# Setup sys path so 'imgtool' is in it.
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__),
+                                                '../..')))
+
+from imgtool.keys import load, RSA, RSAUsageError
+from imgtool.keys.rsa import RSA_KEY_SIZES
+
+
+class KeyGeneration(unittest.TestCase):
+
+    def setUp(self):
+        self.test_dir = tempfile.TemporaryDirectory()
+
+    def tname(self, base):
+        return os.path.join(self.test_dir.name, base)
+
+    def tearDown(self):
+        self.test_dir.cleanup()
+
+    def test_keygen(self):
+        # Try generating a RSA key with non-supported size
+        with self.assertRaises(RSAUsageError):
+            RSA.generate(key_size=1024)
+
+        for key_size in RSA_KEY_SIZES:
+            name1 = self.tname("keygen.pem")
+            k = RSA.generate(key_size=key_size)
+            k.export_private(name1, b'secret')
+
+            # Try loading the key without a password.
+            self.assertIsNone(load(name1))
+
+            k2 = load(name1, b'secret')
+
+            pubname = self.tname('keygen-pub.pem')
+            k2.export_public(pubname)
+            pk2 = load(pubname)
+
+            # We should be able to export the public key from the loaded
+            # public key, but not the private key.
+            pk2.export_public(self.tname('keygen-pub2.pem'))
+            self.assertRaises(RSAUsageError, pk2.export_private,
+                              self.tname('keygen-priv2.pem'))
+
+    def test_emit(self):
+        """Basic sanity check on the code emitters."""
+        for key_size in RSA_KEY_SIZES:
+            k = RSA.generate(key_size=key_size)
+
+            ccode = io.StringIO()
+            k.emit_c_public(ccode)
+            self.assertIn("rsa_pub_key", ccode.getvalue())
+            self.assertIn("rsa_pub_key_len", ccode.getvalue())
+
+            rustcode = io.StringIO()
+            k.emit_rust_public(rustcode)
+            self.assertIn("RSA_PUB_KEY", rustcode.getvalue())
+
+    def test_emit_pub(self):
+        """Basic sanity check on the code emitters, from public key."""
+        pubname = self.tname("public.pem")
+        for key_size in RSA_KEY_SIZES:
+            k = RSA.generate(key_size=key_size)
+            k.export_public(pubname)
+
+            k2 = load(pubname)
+
+            ccode = io.StringIO()
+            k2.emit_c_public(ccode)
+            self.assertIn("rsa_pub_key", ccode.getvalue())
+            self.assertIn("rsa_pub_key_len", ccode.getvalue())
+
+            rustcode = io.StringIO()
+            k2.emit_rust_public(rustcode)
+            self.assertIn("RSA_PUB_KEY", rustcode.getvalue())
+
+    def test_sig(self):
+        for key_size in RSA_KEY_SIZES:
+            k = RSA.generate(key_size=key_size)
+            buf = b'This is the message'
+            sig = k.sign(buf)
+
+            # The code doesn't have any verification, so verify this
+            # manually.
+            k.key.public_key().verify(
+                signature=sig,
+                data=buf,
+                padding=PSS(mgf=MGF1(SHA256()), salt_length=32),
+                algorithm=SHA256())
+
+            # Modify the message to make sure the signature fails.
+            self.assertRaises(InvalidSignature,
+                              k.key.public_key().verify,
+                              signature=sig,
+                              data=b'This is thE message',
+                              padding=PSS(mgf=MGF1(SHA256()), salt_length=32),
+                              algorithm=SHA256())
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tools/mcuboot/imgtool/keys/x25519.py b/tools/mcuboot/imgtool/keys/x25519.py
new file mode 100644
index 00000000..63c0b5a7
--- /dev/null
+++ b/tools/mcuboot/imgtool/keys/x25519.py
@@ -0,0 +1,107 @@
+"""
+X25519 key management
+"""
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric import x25519
+
+from .general import KeyClass
+
+
+class X25519UsageError(Exception):
+    pass
+
+
+class X25519Public(KeyClass):
+    def __init__(self, key):
+        self.key = key
+
+    def shortname(self):
+        return "x25519"
+
+    def _unsupported(self, name):
+        raise X25519UsageError("Operation {} requires private key".format(name))
+
+    def _get_public(self):
+        return self.key
+
+    def get_public_bytes(self):
+        # The key is embedded into MBUboot in "SubjectPublicKeyInfo" format
+        return self._get_public().public_bytes(
+            encoding=serialization.Encoding.DER,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo)
+
+    def get_private_bytes(self, minimal):
+        self._unsupported('get_private_bytes')
+
+    def export_private(self, path, passwd=None):
+        self._unsupported('export_private')
+
+    def export_public(self, path):
+        """Write the public key to the given file."""
+        pem = self._get_public().public_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def sig_type(self):
+        return "X25519"
+
+    def sig_tlv(self):
+        return "X25519"
+
+    def sig_len(self):
+        return 32
+
+
+class X25519(X25519Public):
+    """
+    Wrapper around an X25519 private key.
+    """
+
+    def __init__(self, key):
+        """key should be an instance of EllipticCurvePrivateKey"""
+        self.key = key
+
+    @staticmethod
+    def generate():
+        pk = x25519.X25519PrivateKey.generate()
+        return X25519(pk)
+
+    def _get_public(self):
+        return self.key.public_key()
+
+    def get_private_bytes(self, minimal):
+        return self.key.private_bytes(
+            encoding=serialization.Encoding.DER,
+            format=serialization.PrivateFormat.PKCS8,
+            encryption_algorithm=serialization.NoEncryption())
+
+    def export_private(self, path, passwd=None):
+        """
+        Write the private key to the given file, protecting it with the
+        optional password.
+        """
+        if passwd is None:
+            enc = serialization.NoEncryption()
+        else:
+            enc = serialization.BestAvailableEncryption(passwd)
+        pem = self.key.private_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PrivateFormat.PKCS8,
+            encryption_algorithm=enc)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def sign_digest(self, digest):
+        """Return the actual signature"""
+        return self.key.sign(data=digest)
+
+    def verify_digest(self, signature, digest):
+        """Verify that signature is valid for given digest"""
+        k = self.key
+        if isinstance(self.key, x25519.X25519PrivateKey):
+            k = self.key.public_key()
+        return k.verify(signature=signature, data=digest)