init:初始框架

2026-06-06 20:50:54 +08:00
commit b5be64b642
685 changed files with 398844 additions and 0 deletions
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+# Copyright 2017-2020 Linaro Limited
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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.
+
+imgtool_version = "1.8.0"
@@ -0,0 +1,49 @@
+# Copyright (c) 2019, Arm Limited.
+# Copyright (c) 2020, Linaro Limited
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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.
+
+from enum import Enum
+import cbor
+
+
+class SwComponent(int, Enum):
+    """
+    Software component property IDs specified by
+    Arm's PSA Attestation API 1.0 document.
+    """
+    TYPE = 1
+    MEASUREMENT_VALUE = 2
+    VERSION = 4
+    SIGNER_ID = 5
+    MEASUREMENT_DESCRIPTION = 6
+
+
+def create_sw_component_data(sw_type, sw_version, sw_measurement_description,
+                             sw_measurement_value, sw_signer_id):
+
+    # List of software component properties (Key ID + value)
+    properties = {
+        SwComponent.TYPE: sw_type,
+        SwComponent.VERSION: sw_version,
+        SwComponent.SIGNER_ID: sw_signer_id,
+        SwComponent.MEASUREMENT_DESCRIPTION: sw_measurement_description,
+    }
+
+    # Note: The measurement value must be the last item of the property
+    #       list because later it will be modified by the bootloader.
+    properties[SwComponent.MEASUREMENT_VALUE] = sw_measurement_value
+
+    return cbor.dumps(properties)
@@ -0,0 +1,605 @@
+# Copyright 2018 Nordic Semiconductor ASA
+# Copyright 2017-2020 Linaro Limited
+# Copyright 2019-2021 Arm Limited
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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.
+
+"""
+Image signing and management.
+"""
+
+from . import version as versmod
+from .boot_record import create_sw_component_data
+import click
+from enum import Enum
+from intelhex import IntelHex
+import hashlib
+import struct
+import os.path
+from .keys import rsa, ecdsa, x25519
+from cryptography.hazmat.primitives.asymmetric import ec, padding
+from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+from cryptography.hazmat.primitives.kdf.hkdf import HKDF
+from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import hashes, hmac
+from cryptography.exceptions import InvalidSignature
+
+IMAGE_MAGIC = 0x96f3b83d
+IMAGE_HEADER_SIZE = 32
+BIN_EXT = "bin"
+INTEL_HEX_EXT = "hex"
+DEFAULT_MAX_SECTORS = 128
+MAX_ALIGN = 8
+DEP_IMAGES_KEY = "images"
+DEP_VERSIONS_KEY = "versions"
+MAX_SW_TYPE_LENGTH = 12  # Bytes
+
+# Image header flags.
+IMAGE_F = {
+        'PIC':                   0x0000001,
+        'ENCRYPTED_AES128':      0x0000004,
+        'ENCRYPTED_AES256':      0x0000008,
+        'NON_BOOTABLE':          0x0000010,
+        'RAM_LOAD':              0x0000020,
+        'ROM_FIXED':             0x0000100,
+}
+
+TLV_VALUES = {
+        'KEYHASH': 0x01,
+        'PUBKEY': 0x02,
+        'SHA256': 0x10,
+        'RSA2048': 0x20,
+        'ECDSA224': 0x21,
+        'ECDSA256': 0x22,
+        'RSA3072': 0x23,
+        'ED25519': 0x24,
+        'ENCRSA2048': 0x30,
+        'ENCKW': 0x31,
+        'ENCEC256': 0x32,
+        'ENCX25519': 0x33,
+        'DEPENDENCY': 0x40,
+        'SEC_CNT': 0x50,
+        'BOOT_RECORD': 0x60,
+}
+
+TLV_SIZE = 4
+TLV_INFO_SIZE = 4
+TLV_INFO_MAGIC = 0x6907
+TLV_PROT_INFO_MAGIC = 0x6908
+
+boot_magic = bytes([
+    0x77, 0xc2, 0x95, 0xf3,
+    0x60, 0xd2, 0xef, 0x7f,
+    0x35, 0x52, 0x50, 0x0f,
+    0x2c, 0xb6, 0x79, 0x80, ])
+
+STRUCT_ENDIAN_DICT = {
+        'little': '<',
+        'big':    '>'
+}
+
+VerifyResult = Enum('VerifyResult',
+                    """
+                    OK INVALID_MAGIC INVALID_TLV_INFO_MAGIC INVALID_HASH
+                    INVALID_SIGNATURE
+                    """)
+
+
+class TLV():
+    def __init__(self, endian, magic=TLV_INFO_MAGIC):
+        self.magic = magic
+        self.buf = bytearray()
+        self.endian = endian
+
+    def __len__(self):
+        return TLV_INFO_SIZE + len(self.buf)
+
+    def add(self, kind, payload):
+        """
+        Add a TLV record.  Kind should be a string found in TLV_VALUES above.
+        """
+        e = STRUCT_ENDIAN_DICT[self.endian]
+        if isinstance(kind, int):
+            buf = struct.pack(e + 'BBH', kind, 0, len(payload))
+        else:
+            buf = struct.pack(e + 'BBH', TLV_VALUES[kind], 0, len(payload))
+        self.buf += buf
+        self.buf += payload
+
+    def get(self):
+        if len(self.buf) == 0:
+            return bytes()
+        e = STRUCT_ENDIAN_DICT[self.endian]
+        header = struct.pack(e + 'HH', self.magic, len(self))
+        return header + bytes(self.buf)
+
+
+class Image():
+
+    def __init__(self, version=None, header_size=IMAGE_HEADER_SIZE,
+                 pad_header=False, pad=False, confirm=False, align=1,
+                 slot_size=0, max_sectors=DEFAULT_MAX_SECTORS,
+                 overwrite_only=False, endian="little", load_addr=0,
+                 rom_fixed=None, erased_val=None, save_enctlv=False,
+                 security_counter=None):
+
+        if load_addr and rom_fixed:
+            raise click.UsageError("Can not set rom_fixed and load_addr at the same time")
+
+        self.version = version or versmod.decode_version("0")
+        self.header_size = header_size
+        self.pad_header = pad_header
+        self.pad = pad
+        self.confirm = confirm
+        self.align = align
+        self.slot_size = slot_size
+        self.max_sectors = max_sectors
+        self.overwrite_only = overwrite_only
+        self.endian = endian
+        self.base_addr = None
+        self.load_addr = 0 if load_addr is None else load_addr
+        self.rom_fixed = rom_fixed
+        self.erased_val = 0xff if erased_val is None else int(erased_val, 0)
+        self.payload = []
+        self.enckey = None
+        self.save_enctlv = save_enctlv
+        self.enctlv_len = 0
+
+        if security_counter == 'auto':
+            # Security counter has not been explicitly provided,
+            # generate it from the version number
+            self.security_counter = ((self.version.major << 24)
+                                     + (self.version.minor << 16)
+                                     + self.version.revision)
+        else:
+            self.security_counter = security_counter
+
+    def __repr__(self):
+        return "<Image version={}, header_size={}, security_counter={}, \
+                base_addr={}, load_addr={}, align={}, slot_size={}, \
+                max_sectors={}, overwrite_only={}, endian={} format={}, \
+                payloadlen=0x{:x}>".format(
+                    self.version,
+                    self.header_size,
+                    self.security_counter,
+                    self.base_addr if self.base_addr is not None else "N/A",
+                    self.load_addr,
+                    self.align,
+                    self.slot_size,
+                    self.max_sectors,
+                    self.overwrite_only,
+                    self.endian,
+                    self.__class__.__name__,
+                    len(self.payload))
+
+    def load(self, path):
+        """Load an image from a given file"""
+        ext = os.path.splitext(path)[1][1:].lower()
+        try:
+            if ext == INTEL_HEX_EXT:
+                ih = IntelHex(path)
+                self.payload = ih.tobinarray()
+                self.base_addr = ih.minaddr()
+            else:
+                with open(path, 'rb') as f:
+                    self.payload = f.read()
+        except FileNotFoundError:
+            raise click.UsageError("Input file not found")
+
+        # Add the image header if needed.
+        if self.pad_header and self.header_size > 0:
+            if self.base_addr:
+                # Adjust base_addr for new header
+                self.base_addr -= self.header_size
+            self.payload = bytes([self.erased_val] * self.header_size) + \
+                self.payload
+
+        self.check_header()
+
+    def save(self, path, hex_addr=None):
+        """Save an image from a given file"""
+        ext = os.path.splitext(path)[1][1:].lower()
+        if ext == INTEL_HEX_EXT:
+            # input was in binary format, but HEX needs to know the base addr
+            if self.base_addr is None and hex_addr is None:
+                raise click.UsageError("No address exists in input file "
+                                       "neither was it provided by user")
+            h = IntelHex()
+            if hex_addr is not None:
+                self.base_addr = hex_addr
+            h.frombytes(bytes=self.payload, offset=self.base_addr)
+            if self.pad:
+                trailer_size = self._trailer_size(self.align, self.max_sectors,
+                                                  self.overwrite_only,
+                                                  self.enckey,
+                                                  self.save_enctlv,
+                                                  self.enctlv_len)
+                trailer_addr = (self.base_addr + self.slot_size) - trailer_size
+                padding = bytearray([self.erased_val] * 
+                                    (trailer_size - len(boot_magic)))
+                if self.confirm and not self.overwrite_only:
+                    padding[-MAX_ALIGN] = 0x01  # image_ok = 0x01
+                padding += boot_magic
+                h.puts(trailer_addr, bytes(padding))
+            h.tofile(path, 'hex')
+        else:
+            if self.pad:
+                self.pad_to(self.slot_size)
+            with open(path, 'wb') as f:
+                f.write(self.payload)
+
+    def check_header(self):
+        if self.header_size > 0 and not self.pad_header:
+            if any(v != 0 for v in self.payload[0:self.header_size]):
+                raise click.UsageError("Header padding was not requested and "
+                                       "image does not start with zeros")
+
+    def check_trailer(self):
+        if self.slot_size > 0:
+            tsize = self._trailer_size(self.align, self.max_sectors,
+                                       self.overwrite_only, self.enckey,
+                                       self.save_enctlv, self.enctlv_len)
+            padding = self.slot_size - (len(self.payload) + tsize)
+            if padding < 0:
+                msg = "Image size (0x{:x}) + trailer (0x{:x}) exceeds " \
+                      "requested size 0x{:x}".format(
+                          len(self.payload), tsize, self.slot_size)
+                raise click.UsageError(msg)
+
+    def ecies_hkdf(self, enckey, plainkey):
+        if isinstance(enckey, ecdsa.ECDSA256P1Public):
+            newpk = ec.generate_private_key(ec.SECP256R1(), default_backend())
+            shared = newpk.exchange(ec.ECDH(), enckey._get_public())
+        else:
+            newpk = X25519PrivateKey.generate()
+            shared = newpk.exchange(enckey._get_public())
+        derived_key = HKDF(
+            algorithm=hashes.SHA256(), length=48, salt=None,
+            info=b'MCUBoot_ECIES_v1', backend=default_backend()).derive(shared)
+        encryptor = Cipher(algorithms.AES(derived_key[:16]),
+                           modes.CTR(bytes([0] * 16)),
+                           backend=default_backend()).encryptor()
+        cipherkey = encryptor.update(plainkey) + encryptor.finalize()
+        mac = hmac.HMAC(derived_key[16:], hashes.SHA256(),
+                        backend=default_backend())
+        mac.update(cipherkey)
+        ciphermac = mac.finalize()
+        if isinstance(enckey, ecdsa.ECDSA256P1Public):
+            pubk = newpk.public_key().public_bytes(
+                encoding=Encoding.X962,
+                format=PublicFormat.UncompressedPoint)
+        else:
+            pubk = newpk.public_key().public_bytes(
+                encoding=Encoding.Raw,
+                format=PublicFormat.Raw)
+        return cipherkey, ciphermac, pubk
+
+    def create(self, key, public_key_format, enckey, dependencies=None,
+               sw_type=None, custom_tlvs=None, encrypt_keylen=128):
+        self.enckey = enckey
+
+        # Calculate the hash of the public key
+        if key is not None:
+            pub = key.get_public_bytes()
+            sha = hashlib.sha256()
+            sha.update(pub)
+            pubbytes = sha.digest()
+        else:
+            pubbytes = bytes(hashlib.sha256().digest_size)
+
+        protected_tlv_size = 0
+
+        if self.security_counter is not None:
+            # Size of the security counter TLV: header ('HH') + payload ('I')
+            #                                   = 4 + 4 = 8 Bytes
+            protected_tlv_size += TLV_SIZE + 4
+
+        if sw_type is not None:
+            if len(sw_type) > MAX_SW_TYPE_LENGTH:
+                msg = "'{}' is too long ({} characters) for sw_type. Its " \
+                      "maximum allowed length is 12 characters.".format(
+                       sw_type, len(sw_type))
+                raise click.UsageError(msg)
+
+            image_version = (str(self.version.major) + '.'
+                             + str(self.version.minor) + '.'
+                             + str(self.version.revision))
+
+            # The image hash is computed over the image header, the image
+            # itself and the protected TLV area. However, the boot record TLV
+            # (which is part of the protected area) should contain this hash
+            # 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)
+
+            # Create CBOR encoded boot record
+            boot_record = create_sw_component_data(sw_type, image_version,
+                                                   "SHA256", digest,
+                                                   pubbytes)
+
+            protected_tlv_size += TLV_SIZE + len(boot_record)
+
+        if dependencies is not None:
+            # Size of a Dependency TLV = Header ('HH') + Payload('IBBHI')
+            # = 4 + 12 = 16 Bytes
+            dependencies_num = len(dependencies[DEP_IMAGES_KEY])
+            protected_tlv_size += (dependencies_num * 16)
+
+        if custom_tlvs is not None:
+            for value in custom_tlvs.values():
+                protected_tlv_size += TLV_SIZE + len(value)
+
+        if protected_tlv_size != 0:
+            # Add the size of the TLV info header
+            protected_tlv_size += TLV_INFO_SIZE
+
+        # At this point the image is already on the payload
+        #
+        # This adds the padding if image is not aligned to the 16 Bytes
+        # in encrypted mode
+        if self.enckey is not None:
+            pad_len = len(self.payload) % 16
+            if pad_len > 0:
+                pad = bytes(16 - pad_len)
+                if isinstance(self.payload, bytes):
+                    self.payload += pad
+                else:
+                    self.payload.extend(pad)
+
+        # This adds the header to the payload as well
+        if encrypt_keylen == 256:
+            self.add_header(enckey, protected_tlv_size, 256)
+        else:
+            self.add_header(enckey, protected_tlv_size)
+
+        prot_tlv = TLV(self.endian, TLV_PROT_INFO_MAGIC)
+
+        # Protected TLVs must be added first, because they are also included
+        # in the hash calculation
+        protected_tlv_off = None
+        if protected_tlv_size != 0:
+
+            e = STRUCT_ENDIAN_DICT[self.endian]
+
+            if self.security_counter is not None:
+                payload = struct.pack(e + 'I', self.security_counter)
+                prot_tlv.add('SEC_CNT', payload)
+
+            if sw_type is not None:
+                prot_tlv.add('BOOT_RECORD', boot_record)
+
+            if dependencies is not None:
+                for i in range(dependencies_num):
+                    payload = struct.pack(
+                                    e + 'B3x'+'BBHI',
+                                    int(dependencies[DEP_IMAGES_KEY][i]),
+                                    dependencies[DEP_VERSIONS_KEY][i].major,
+                                    dependencies[DEP_VERSIONS_KEY][i].minor,
+                                    dependencies[DEP_VERSIONS_KEY][i].revision,
+                                    dependencies[DEP_VERSIONS_KEY][i].build
+                                    )
+                    prot_tlv.add('DEPENDENCY', payload)
+
+            if custom_tlvs is not None:
+                for tag, value in custom_tlvs.items():
+                    prot_tlv.add(tag, value)
+
+            protected_tlv_off = len(self.payload)
+            self.payload += prot_tlv.get()
+
+        tlv = TLV(self.endian)
+
+        # Note that ecdsa wants to do the hashing itself, which means
+        # we get to hash it twice.
+        sha = hashlib.sha256()
+        sha.update(self.payload)
+        digest = sha.digest()
+
+        tlv.add('SHA256', digest)
+
+        if key is not None:
+            if public_key_format == 'hash':
+                tlv.add('KEYHASH', pubbytes)
+            else:
+                tlv.add('PUBKEY', pub)
+
+            # `sign` expects the full image payload (sha256 done internally),
+            # while `sign_digest` expects only the digest of the payload
+
+            if hasattr(key, 'sign'):
+                sig = key.sign(bytes(self.payload))
+            else:
+                sig = key.sign_digest(digest)
+            tlv.add(key.sig_tlv(), sig)
+
+        # At this point the image was hashed + signed, we can remove the
+        # protected TLVs from the payload (will be re-added later)
+        if protected_tlv_off is not None:
+            self.payload = self.payload[:protected_tlv_off]
+
+        if enckey is not None:
+            if encrypt_keylen == 256:
+                plainkey = os.urandom(32)
+            else:
+                plainkey = os.urandom(16)
+
+            if isinstance(enckey, rsa.RSAPublic):
+                cipherkey = enckey._get_public().encrypt(
+                    plainkey, padding.OAEP(
+                        mgf=padding.MGF1(algorithm=hashes.SHA256()),
+                        algorithm=hashes.SHA256(),
+                        label=None))
+                self.enctlv_len = len(cipherkey)
+                tlv.add('ENCRSA2048', cipherkey)
+            elif isinstance(enckey, (ecdsa.ECDSA256P1Public,
+                                     x25519.X25519Public)):
+                cipherkey, mac, pubk = self.ecies_hkdf(enckey, plainkey)
+                enctlv = pubk + mac + cipherkey
+                self.enctlv_len = len(enctlv)
+                if isinstance(enckey, ecdsa.ECDSA256P1Public):
+                    tlv.add('ENCEC256', enctlv)
+                else:
+                    tlv.add('ENCX25519', enctlv)
+
+            nonce = bytes([0] * 16)
+            cipher = Cipher(algorithms.AES(plainkey), modes.CTR(nonce),
+                            backend=default_backend())
+            encryptor = cipher.encryptor()
+            img = bytes(self.payload[self.header_size:])
+            self.payload[self.header_size:] = \
+                encryptor.update(img) + encryptor.finalize()
+
+        self.payload += prot_tlv.get()
+        self.payload += tlv.get()
+
+        self.check_trailer()
+
+    def add_header(self, enckey, protected_tlv_size, aes_length=128):
+        """Install the image header."""
+
+        flags = 0
+        if enckey is not None:
+            if aes_length == 128:
+                flags |= IMAGE_F['ENCRYPTED_AES128']
+            else:
+                flags |= IMAGE_F['ENCRYPTED_AES256']
+        if self.load_addr != 0:
+            # Indicates that this image should be loaded into RAM
+            # instead of run directly from flash.
+            flags |= IMAGE_F['RAM_LOAD']
+        if self.rom_fixed:
+            flags |= IMAGE_F['ROM_FIXED']
+
+        e = STRUCT_ENDIAN_DICT[self.endian]
+        fmt = (e +
+               # type ImageHdr struct {
+               'I' +     # Magic    uint32
+               'I' +     # LoadAddr uint32
+               'H' +     # HdrSz    uint16
+               'H' +     # PTLVSz   uint16
+               'I' +     # ImgSz    uint32
+               'I' +     # Flags    uint32
+               'BBHI' +  # Vers     ImageVersion
+               'I'       # Pad1     uint32
+               )  # }
+        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
+        self.payload = bytearray(self.payload)
+        self.payload[:len(header)] = header
+
+    def _trailer_size(self, write_size, max_sectors, overwrite_only, enckey,
+                      save_enctlv, enctlv_len):
+        # NOTE: should already be checked by the argument parser
+        magic_size = 16
+        if overwrite_only:
+            return MAX_ALIGN * 2 + magic_size
+        else:
+            if write_size not in set([1, 2, 4, 8]):
+                raise click.BadParameter("Invalid alignment: {}".format(
+                    write_size))
+            m = DEFAULT_MAX_SECTORS if max_sectors is None else max_sectors
+            trailer = m * 3 * write_size  # status area
+            if enckey is not None:
+                if save_enctlv:
+                    # TLV saved by the bootloader is aligned
+                    keylen = (int((enctlv_len - 1) / MAX_ALIGN) + 1) * MAX_ALIGN
+                else:
+                    keylen = 16
+                trailer += keylen * 2  # encryption keys
+            trailer += MAX_ALIGN * 4  # image_ok/copy_done/swap_info/swap_size
+            trailer += magic_size
+            return trailer
+
+    def pad_to(self, size):
+        """Pad the image to the given size, with the given flash alignment."""
+        tsize = self._trailer_size(self.align, self.max_sectors,
+                                   self.overwrite_only, self.enckey,
+                                   self.save_enctlv, self.enctlv_len)
+        padding = size - (len(self.payload) + tsize)
+        pbytes = bytearray([self.erased_val] * padding)
+        pbytes += bytearray([self.erased_val] * (tsize - len(boot_magic)))
+        if self.confirm and not self.overwrite_only:
+            pbytes[-MAX_ALIGN] = 0x01  # image_ok = 0x01
+        pbytes += boot_magic
+        self.payload += pbytes
+
+    @staticmethod
+    def verify(imgfile, key):
+        with open(imgfile, "rb") as f:
+            b = f.read()
+
+        magic, _, header_size, _, img_size = struct.unpack('IIHHI', b[:16])
+        version = struct.unpack('BBHI', b[20:28])
+
+        if magic != IMAGE_MAGIC:
+            return VerifyResult.INVALID_MAGIC, None, None
+
+        tlv_off = header_size + img_size
+        tlv_info = b[tlv_off:tlv_off+TLV_INFO_SIZE]
+        magic, tlv_tot = struct.unpack('HH', tlv_info)
+        if magic == TLV_PROT_INFO_MAGIC:
+            tlv_off += tlv_tot
+            tlv_info = b[tlv_off:tlv_off+TLV_INFO_SIZE]
+            magic, tlv_tot = struct.unpack('HH', tlv_info)
+
+        if magic != TLV_INFO_MAGIC:
+            return VerifyResult.INVALID_TLV_INFO_MAGIC, None, None
+
+        sha = hashlib.sha256()
+        prot_tlv_size = tlv_off
+        sha.update(b[:prot_tlv_size])
+        digest = sha.digest()
+
+        tlv_end = tlv_off + tlv_tot
+        tlv_off += TLV_INFO_SIZE  # skip tlv info
+        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"]:
+                off = tlv_off + TLV_SIZE
+                if digest == b[off:off+tlv_len]:
+                    if key is None:
+                        return VerifyResult.OK, version, digest
+                else:
+                    return VerifyResult.INVALID_HASH, None, None
+            elif key is not None and tlv_type == TLV_VALUES[key.sig_tlv()]:
+                off = tlv_off + TLV_SIZE
+                tlv_sig = b[off:off+tlv_len]
+                payload = b[:prot_tlv_size]
+                try:
+                    if hasattr(key, 'verify'):
+                        key.verify(tlv_sig, payload)
+                    else:
+                        key.verify_digest(tlv_sig, digest)
+                    return VerifyResult.OK, version, digest
+                except InvalidSignature:
+                    # continue to next TLV
+                    pass
+            tlv_off += TLV_SIZE + tlv_len
+        return VerifyResult.INVALID_SIGNATURE, None, None
@@ -0,0 +1,96 @@
+# Copyright 2017 Linaro Limited
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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)))
@@ -0,0 +1,159 @@
+"""
+ECDSA key management
+"""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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
@@ -0,0 +1,101 @@
+"""
+Tests for ECDSA keys
+"""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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()
@@ -0,0 +1,107 @@
+"""
+ED25519 key management
+"""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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)
@@ -0,0 +1,105 @@
+"""
+Tests for ECDSA keys
+"""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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()
@@ -0,0 +1,47 @@
+"""General key class."""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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: &[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)
@@ -0,0 +1,165 @@
+"""
+RSA Key management
+"""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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())
@@ -0,0 +1,117 @@
+"""
+Tests for RSA keys
+"""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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()
@@ -0,0 +1,109 @@
+"""
+X25519 key management
+"""
+
+# SPDX-License-Identifier: Apache-2.0
+
+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)
@@ -0,0 +1,395 @@
+#! /usr/bin/env python3
+#
+# Copyright 2017-2020 Linaro Limited
+# Copyright 2019-2021 Arm Limited
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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.
+
+import re
+import click
+import getpass
+import imgtool.keys as keys
+import sys
+from imgtool import image, imgtool_version
+from imgtool.version import decode_version
+from .keys import (
+    RSAUsageError, ECDSAUsageError, Ed25519UsageError, X25519UsageError)
+
+MIN_PYTHON_VERSION = (3, 6)
+if sys.version_info < MIN_PYTHON_VERSION:
+    sys.exit("Python %s.%s or newer is required by imgtool."
+             % MIN_PYTHON_VERSION)
+
+
+def gen_rsa2048(keyfile, passwd):
+    keys.RSA.generate().export_private(path=keyfile, passwd=passwd)
+
+
+def gen_rsa3072(keyfile, passwd):
+    keys.RSA.generate(key_size=3072).export_private(path=keyfile,
+                                                    passwd=passwd)
+
+
+def gen_ecdsa_p256(keyfile, passwd):
+    keys.ECDSA256P1.generate().export_private(keyfile, passwd=passwd)
+
+
+def gen_ecdsa_p224(keyfile, passwd):
+    print("TODO: p-224 not yet implemented")
+
+
+def gen_ed25519(keyfile, passwd):
+    keys.Ed25519.generate().export_private(path=keyfile, passwd=passwd)
+
+
+def gen_x25519(keyfile, passwd):
+    keys.X25519.generate().export_private(path=keyfile, passwd=passwd)
+
+
+valid_langs = ['c', 'rust']
+keygens = {
+    'rsa-2048':   gen_rsa2048,
+    'rsa-3072':   gen_rsa3072,
+    'ecdsa-p256': gen_ecdsa_p256,
+    'ecdsa-p224': gen_ecdsa_p224,
+    'ed25519':    gen_ed25519,
+    'x25519':     gen_x25519,
+}
+
+
+def load_key(keyfile):
+    # TODO: better handling of invalid pass-phrase
+    key = keys.load(keyfile)
+    if key is not None:
+        return key
+    passwd = getpass.getpass("Enter key passphrase: ").encode('utf-8')
+    return keys.load(keyfile, passwd)
+
+
+def get_password():
+    while True:
+        passwd = getpass.getpass("Enter key passphrase: ")
+        passwd2 = getpass.getpass("Reenter passphrase: ")
+        if passwd == passwd2:
+            break
+        print("Passwords do not match, try again")
+
+    # Password must be bytes, always use UTF-8 for consistent
+    # encoding.
+    return passwd.encode('utf-8')
+
+
+@click.option('-p', '--password', is_flag=True,
+              help='Prompt for password to protect key')
+@click.option('-t', '--type', metavar='type', required=True,
+              type=click.Choice(keygens.keys()), prompt=True,
+              help='{}'.format('One of: {}'.format(', '.join(keygens.keys()))))
+@click.option('-k', '--key', metavar='filename', required=True)
+@click.command(help='Generate pub/private keypair')
+def keygen(type, key, password):
+    password = get_password() if password else None
+    keygens[type](key, password)
+
+
+@click.option('-l', '--lang', metavar='lang', default=valid_langs[0],
+              type=click.Choice(valid_langs))
+@click.option('-k', '--key', metavar='filename', required=True)
+@click.command(help='Dump public key from keypair')
+def getpub(key, lang):
+    key = load_key(key)
+    if key is None:
+        print("Invalid passphrase")
+    elif lang == 'c':
+        key.emit_c_public()
+    elif lang == 'rust':
+        key.emit_rust_public()
+    else:
+        raise ValueError("BUG: should never get here!")
+
+
+@click.option('--minimal', default=False, is_flag=True,
+              help='Reduce the size of the dumped private key to include only '
+                   'the minimum amount of data required to decrypt. This '
+                   'might require changes to the build config. Check the docs!'
+              )
+@click.option('-k', '--key', metavar='filename', required=True)
+@click.command(help='Dump private key from keypair')
+def getpriv(key, minimal):
+    key = load_key(key)
+    if key is None:
+        print("Invalid passphrase")
+    try:
+        key.emit_private(minimal)
+    except (RSAUsageError, ECDSAUsageError, Ed25519UsageError,
+            X25519UsageError) as e:
+        raise click.UsageError(e)
+
+
+@click.argument('imgfile')
+@click.option('-k', '--key', metavar='filename')
+@click.command(help="Check that signed image can be verified by given key")
+def verify(key, imgfile):
+    key = load_key(key) if key else None
+    ret, version, digest = image.Image.verify(imgfile, key)
+    if ret == image.VerifyResult.OK:
+        print("Image was correctly validated")
+        print("Image version: {}.{}.{}+{}".format(*version))
+        print("Image digest: {}".format(digest.hex()))
+        return
+    elif ret == image.VerifyResult.INVALID_MAGIC:
+        print("Invalid image magic; is this an MCUboot image?")
+    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")
+    elif ret == image.VerifyResult.INVALID_SIGNATURE:
+        print("No signature found for the given key")
+    else:
+        print("Unknown return code: {}".format(ret))
+    sys.exit(1)
+
+
+def validate_version(ctx, param, value):
+    try:
+        decode_version(value)
+        return value
+    except ValueError as e:
+        raise click.BadParameter("{}".format(e))
+
+
+def validate_security_counter(ctx, param, value):
+    if value is not None:
+        if value.lower() == 'auto':
+            return 'auto'
+        else:
+            try:
+                return int(value, 0)
+            except ValueError:
+                raise click.BadParameter(
+                    "{} is not a valid integer. Please use code literals "
+                    "prefixed with 0b/0B, 0o/0O, or 0x/0X as necessary."
+                    .format(value))
+
+
+def validate_header_size(ctx, param, value):
+    min_hdr_size = image.IMAGE_HEADER_SIZE
+    if value < min_hdr_size:
+        raise click.BadParameter(
+            "Minimum value for -H/--header-size is {}".format(min_hdr_size))
+    return value
+
+
+def get_dependencies(ctx, param, value):
+    if value is not None:
+        versions = []
+        images = re.findall(r"\((\d+)", value)
+        if len(images) == 0:
+            raise click.BadParameter(
+                "Image dependency format is invalid: {}".format(value))
+        raw_versions = re.findall(r",\s*([0-9.+]+)\)", value)
+        if len(images) != len(raw_versions):
+            raise click.BadParameter(
+                '''There's a mismatch between the number of dependency images
+                and versions in: {}'''.format(value))
+        for raw_version in raw_versions:
+            try:
+                versions.append(decode_version(raw_version))
+            except ValueError as e:
+                raise click.BadParameter("{}".format(e))
+        dependencies = dict()
+        dependencies[image.DEP_IMAGES_KEY] = images
+        dependencies[image.DEP_VERSIONS_KEY] = versions
+        return dependencies
+
+
+class BasedIntParamType(click.ParamType):
+    name = 'integer'
+
+    def convert(self, value, param, ctx):
+        try:
+            return int(value, 0)
+        except ValueError:
+            self.fail('%s is not a valid integer. Please use code literals '
+                      'prefixed with 0b/0B, 0o/0O, or 0x/0X as necessary.'
+                      % value, param, ctx)
+
+
+@click.argument('outfile')
+@click.argument('infile')
+@click.option('--custom-tlv', required=False, nargs=2, default=[],
+              multiple=True, metavar='[tag] [value]',
+              help='Custom TLV that will be placed into protected area. '
+                   'Add "0x" prefix if the value should be interpreted as an '
+                   'integer, otherwise it will be interpreted as a string. '
+                   'Specify the option multiple times to add multiple TLVs.')
+@click.option('-R', '--erased-val', type=click.Choice(['0', '0xff']),
+              required=False,
+              help='The value that is read back from erased flash.')
+@click.option('-x', '--hex-addr', type=BasedIntParamType(), required=False,
+              help='Adjust address in hex output file.')
+@click.option('-L', '--load-addr', type=BasedIntParamType(), required=False,
+              help='Load address for image when it should run from RAM.')
+@click.option('-F', '--rom-fixed', type=BasedIntParamType(), required=False,
+              help='Set flash address the image is built for.')
+@click.option('--save-enctlv', default=False, is_flag=True,
+              help='When upgrading, save encrypted key TLVs instead of plain '
+                   'keys. Enable when BOOT_SWAP_SAVE_ENCTLV config option '
+                   'was set.')
+@click.option('-E', '--encrypt', metavar='filename',
+              help='Encrypt image using the provided public key. '
+                   '(Not supported in direct-xip or ram-load mode.)')
+@click.option('--encrypt-keylen', default='128',
+              type=click.Choice(['128','256']),
+              help='When encrypting the image using AES, select a 128 bit or '
+                   '256 bit key len.')
+@click.option('-e', '--endian', type=click.Choice(['little', 'big']),
+              default='little', help="Select little or big endian")
+@click.option('--overwrite-only', default=False, is_flag=True,
+              help='Use overwrite-only instead of swap upgrades')
+@click.option('--boot-record', metavar='sw_type', help='Create CBOR encoded '
+              'boot record TLV. The sw_type represents the role of the '
+              'software component (e.g. CoFM for coprocessor firmware). '
+              '[max. 12 characters]')
+@click.option('-M', '--max-sectors', type=int,
+              help='When padding allow for this amount of sectors (defaults '
+                   'to 128)')
+@click.option('--confirm', default=False, is_flag=True,
+              help='When padding the image, mark it as confirmed (implies '
+                   '--pad)')
+@click.option('--pad', default=False, is_flag=True,
+              help='Pad image to --slot-size bytes, adding trailer magic')
+@click.option('-S', '--slot-size', type=BasedIntParamType(), required=True,
+              help='Size of the slot. If the slots have different sizes, use '
+              'the size of the secondary slot.')
+@click.option('--pad-header', default=False, is_flag=True,
+              help='Add --header-size zeroed bytes at the beginning of the '
+                   'image')
+@click.option('-H', '--header-size', callback=validate_header_size,
+              type=BasedIntParamType(), required=True)
+@click.option('--pad-sig', default=False, is_flag=True,
+              help='Add 0-2 bytes of padding to ECDSA signature '
+                   '(for mcuboot <1.5)')
+@click.option('-d', '--dependencies', callback=get_dependencies,
+              required=False, help='''Add dependence on another image, format:
+              "(<image_ID>,<image_version>), ... "''')
+@click.option('-s', '--security-counter', callback=validate_security_counter,
+              help='Specify the value of security counter. Use the `auto` '
+              'keyword to automatically generate it from the image version.')
+@click.option('-v', '--version', callback=validate_version,  required=True)
+@click.option('--align', type=click.Choice(['1', '2', '4', '8']),
+              required=True)
+@click.option('--public-key-format', type=click.Choice(['hash', 'full']),
+              default='hash', help='In what format to add the public key to '
+              'the image manifest: full key or hash of the key.')
+@click.option('-k', '--key', metavar='filename')
+@click.command(help='''Create a signed or unsigned image\n
+               INFILE and OUTFILE are parsed as Intel HEX if the params have
+               .hex extension, otherwise binary format is used''')
+def sign(key, public_key_format, align, version, pad_sig, header_size,
+         pad_header, slot_size, pad, confirm, max_sectors, overwrite_only,
+         endian, encrypt_keylen, encrypt, infile, outfile, dependencies,
+         load_addr, hex_addr, erased_val, save_enctlv, security_counter,
+         boot_record, custom_tlv, rom_fixed):
+
+    if confirm:
+        # Confirmed but non-padded images don't make much sense, because
+        # otherwise there's no trailer area for writing the confirmed status.
+        pad = True
+    img = image.Image(version=decode_version(version), header_size=header_size,
+                      pad_header=pad_header, pad=pad, confirm=confirm,
+                      align=int(align), slot_size=slot_size,
+                      max_sectors=max_sectors, overwrite_only=overwrite_only,
+                      endian=endian, load_addr=load_addr, rom_fixed=rom_fixed,
+                      erased_val=erased_val, save_enctlv=save_enctlv,
+                      security_counter=security_counter)
+    img.load(infile)
+    key = load_key(key) if key else None
+    enckey = load_key(encrypt) if encrypt else None
+    if enckey and key:
+        if ((isinstance(key, keys.ECDSA256P1) and
+             not isinstance(enckey, keys.ECDSA256P1Public))
+                or (isinstance(key, keys.RSA) and
+                    not isinstance(enckey, keys.RSAPublic))):
+            # FIXME
+            raise click.UsageError("Signing and encryption must use the same "
+                                   "type of key")
+
+    if pad_sig and hasattr(key, 'pad_sig'):
+        key.pad_sig = True
+
+    # Get list of custom protected TLVs from the command-line
+    custom_tlvs = {}
+    for tlv in custom_tlv:
+        tag = int(tlv[0], 0)
+        if tag in custom_tlvs:
+            raise click.UsageError('Custom TLV %s already exists.' % hex(tag))
+        if tag in image.TLV_VALUES.values():
+            raise click.UsageError(
+                'Custom TLV %s conflicts with predefined TLV.' % hex(tag))
+
+        value = tlv[1]
+        if value.startswith('0x'):
+            if len(value[2:]) % 2:
+                raise click.UsageError('Custom TLV length is odd.')
+            custom_tlvs[tag] = bytes.fromhex(value[2:])
+        else:
+            custom_tlvs[tag] = value.encode('utf-8')
+
+    img.create(key, public_key_format, enckey, dependencies, boot_record,
+               custom_tlvs, int(encrypt_keylen))
+    img.save(outfile, hex_addr)
+
+
+class AliasesGroup(click.Group):
+
+    _aliases = {
+        "create": "sign",
+    }
+
+    def list_commands(self, ctx):
+        cmds = [k for k in self.commands]
+        aliases = [k for k in self._aliases]
+        return sorted(cmds + aliases)
+
+    def get_command(self, ctx, cmd_name):
+        rv = click.Group.get_command(self, ctx, cmd_name)
+        if rv is not None:
+            return rv
+        if cmd_name in self._aliases:
+            return click.Group.get_command(self, ctx, self._aliases[cmd_name])
+        return None
+
+
+@click.command(help='Print imgtool version information')
+def version():
+    print(imgtool_version)
+
+
+@click.command(cls=AliasesGroup,
+               context_settings=dict(help_option_names=['-h', '--help']))
+def imgtool():
+    pass
+
+
+imgtool.add_command(keygen)
+imgtool.add_command(getpub)
+imgtool.add_command(getpriv)
+imgtool.add_command(verify)
+imgtool.add_command(sign)
+imgtool.add_command(version)
+
+
+if __name__ == '__main__':
+    imgtool()
@@ -0,0 +1,55 @@
+# Copyright 2017 Linaro Limited
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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.
+
+"""
+Semi Semantic Versioning
+
+Implements a subset of semantic versioning that is supportable by the image
+header.
+"""
+
+from collections import namedtuple
+import re
+
+SemiSemVersion = namedtuple('SemiSemVersion', ['major', 'minor', 'revision',
+                                               'build'])
+
+version_re = re.compile(
+    r"""^([1-9]\d*|0)(\.([1-9]\d*|0)(\.([1-9]\d*|0)(\+([1-9]\d*|0))?)?)?$""")
+
+
+def decode_version(text):
+    """Decode the version string, which should be of the form maj.min.rev+build
+    """
+    m = version_re.match(text)
+    if m:
+        result = SemiSemVersion(
+                int(m.group(1)) if m.group(1) else 0,
+                int(m.group(3)) if m.group(3) else 0,
+                int(m.group(5)) if m.group(5) else 0,
+                int(m.group(7)) if m.group(7) else 0)
+        return result
+    else:
+        msg = "Invalid version number, should be maj.min.rev+build with later "
+        msg += "parts optional"
+        raise ValueError(msg)
+
+
+if __name__ == '__main__':
+    print(decode_version("1.2"))
+    print(decode_version("1.0"))
+    print(decode_version("0.0.2+75"))
+    print(decode_version("0.0.0+00"))