imgtool: Add support for dependency description

This commit aims to add the ability to specify and add dependency
TLVs to MCUBOOT. Due to the private nature of this feature, having
dependency TLVs mean that the TLV Info header and these TLVs become
part of the protected area (they are supposed to get signed as well).
Since the TLV Info header containing the whole TLV section's size
becomes protected, this size needs to be calculated in advance to get
proper hash values.

Change-Id: I13277a3b595acc2bb8c5084420f3d61c8d301dc2
Author: Bence Kaposzta <bence.kaposzta@arm.com>
Signed-off-by: David Vincze <david.vincze@arm.com>

scripts/imgtool/image.py

@@ -1,5 +1,6 @@
 # Copyright 2018 Nordic Semiconductor ASA
 # Copyright 2017 Linaro Limited
+# Copyright 2019 Arm Limited
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -32,6 +33,8 @@ IMAGE_HEADER_SIZE = 32
 BIN_EXT = "bin"
 INTEL_HEX_EXT = "hex"
 DEFAULT_MAX_SECTORS = 128
+DEP_IMAGES_KEY = "images"
+DEP_VERSIONS_KEY = "versions"
 
 # Image header flags.
 IMAGE_F = {
@@ -48,6 +51,7 @@ TLV_VALUES = {
         'ECDSA256': 0x22,
         'ENCRSA2048': 0x30,
         'ENCKW128': 0x31,
+        'DEPENDENCY': 0x40
 }
 
 TLV_INFO_SIZE = 4
@@ -168,11 +172,49 @@ class Image():
                         len(self.payload), tsize, self.slot_size)
                 raise Exception(msg)
 
-    def create(self, key, enckey):
+    def create(self, key, enckey, dependencies=None):
-        self.add_header(enckey)
+        if dependencies is None:
+            dependencies_num = 0
+            protected_tlv_size = 0
+        else:
+            # Size of a Dependency TLV = Header ('BBH') + Payload('IBBHI')
+            # = 16 Bytes
+            dependencies_num = len(dependencies[DEP_IMAGES_KEY])
+            protected_tlv_size = (dependencies_num * 16) + TLV_INFO_SIZE
+
+        self.add_header(enckey, protected_tlv_size)
 
         tlv = TLV(self.endian)
 
+        if protected_tlv_size != 0:
+            for i in range(dependencies_num):
+                e = STRUCT_ENDIAN_DICT[self.endian]
+                payload = struct.pack(
+                                e + 'I'+'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
+                                )
+                tlv.add('DEPENDENCY', payload)
+            # Full TLV size needs to be calculated in advance, because the
+            # header will be protected as well
+            tlv_header_size = 4
+            payload_digest_size = 32
+            keyhash_size = 32
+            cipherkey_size = 32
+
+            full_size = TLV_INFO_SIZE + len(tlv.buf) + tlv_header_size \
+                        + payload_digest_size
+            if key is not None:
+                full_size += tlv_header_size + keyhash_size \
+                             + tlv_header_size + key.sig_len()
+            if enckey is not None:
+                full_size += tlv_header_size + cipherkey_size
+            tlv_header = struct.pack(e + 'HH', TLV_INFO_MAGIC, full_size)
+            self.payload += tlv_header + bytes(tlv.buf)
+
         # Note that ecdsa wants to do the hashing itself, which means
         # we get to hash it twice.
         sha = hashlib.sha256()
@@ -208,9 +250,9 @@ class Image():
             self.payload[self.header_size:] = encryptor.update(img) + \
                                               encryptor.finalize()
 
-        self.payload += tlv.get()
+        self.payload += tlv.get()[protected_tlv_size:]
 
-    def add_header(self, enckey):
+    def add_header(self, enckey, protected_tlv_size):
         """Install the image header."""
 
         flags = 0
@@ -219,29 +261,29 @@ class Image():
 
         e = STRUCT_ENDIAN_DICT[self.endian]
         fmt = (e +
-            # type ImageHdr struct {
+               # type ImageHdr struct {
-            'I' +   # Magic uint32
+               'I' +     # Magic    uint32
-            'I' +   # LoadAddr uint32
+               'I' +     # LoadAddr uint32
-            'H' +   # HdrSz uint16
+               'H' +     # HdrSz    uint16
-            'H' +   # Pad1  uint16
+               'H' +     # PTLVSz   uint16
-            'I' +   # ImgSz uint32
+               'I' +     # ImgSz    uint32
-            'I' +   # Flags uint32
+               'I' +     # Flags    uint32
-            'BBHI' + # Vers  ImageVersion
+               'BBHI' +  # Vers     ImageVersion
-            'I'     # Pad2  uint32
+               'I'       # Pad1     uint32
-            ) # }
+               )  # }
         assert struct.calcsize(fmt) == IMAGE_HEADER_SIZE
         header = struct.pack(fmt,
                 IMAGE_MAGIC,
                 0, # LoadAddr
                 self.header_size,
-                0, # Pad1
+                protected_tlv_size,  # TLV Info header + Dependency TLVs
                 len(self.payload) - self.header_size, # ImageSz
                 flags, # Flags
                 self.version.major,
                 self.version.minor or 0,
                 self.version.revision or 0,
                 self.version.build or 0,
-                0) # Pad2
+                0)  # Pad1
         self.payload = bytearray(self.payload)
         self.payload[:len(header)] = header
 

scripts/imgtool/main.py

@@ -1,6 +1,7 @@
 #! /usr/bin/env python3
 #
 # Copyright 2017 Linaro Limited
+# Copyright 2019 Arm Limited
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -14,6 +15,7 @@
 # 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
@@ -106,6 +108,29 @@ def validate_header_size(ctx, param, value):
     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'
 
@@ -138,6 +163,9 @@ class BasedIntParamType(click.ParamType):
               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('-d', '--dependencies', callback=get_dependencies,
+              required=False, help='''Add dependence on another image, format:
+              "(<image_ID>,<image_version>), ... "''')
 @click.option('-v', '--version', callback=validate_version,  required=True)
 @click.option('--align', type=click.Choice(['1', '2', '4', '8']),
               required=True)
@@ -146,7 +174,8 @@ class BasedIntParamType(click.ParamType):
                INFILE and OUTFILE are parsed as Intel HEX if the params have
                .hex extension, othewise binary format is used''')
 def sign(key, align, version, header_size, pad_header, slot_size, pad,
-         max_sectors, overwrite_only, endian, encrypt, infile, outfile):
+         max_sectors, overwrite_only, endian, encrypt, infile, outfile,
+         dependencies):
     img = image.Image(version=decode_version(version), header_size=header_size,
                       pad_header=pad_header, pad=pad, align=int(align),
                       slot_size=slot_size, max_sectors=max_sectors,
@@ -159,7 +188,7 @@ def sign(key, align, version, header_size, pad_header, slot_size, pad,
             raise Exception("Encryption only available with RSA key")
         if key and not isinstance(key, keys.RSA2048):
             raise Exception("Signing only available with private RSA key")
-    img.create(key, enckey)
+    img.create(key, enckey, dependencies)
     img.save(outfile)