1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
|
# SPDX-License-Identifier: GPL-2.0+
# Copyright (c) 2022 Softathome
# Written by Philippe Reynes <philippe.reynes@softathome.com>
#
# Entry-type for the global header
#
import os
import struct
from dtoc import fdt_util
from u_boot_pylib import tools
from binman.entry import Entry
from binman.etype.collection import Entry_collection
from binman.entry import EntryArg
from Cryptodome.Hash import SHA256, SHA384, SHA512
from Cryptodome.PublicKey import RSA
from Cryptodome.Signature import pkcs1_15
from Cryptodome.Signature import pss
PRE_LOAD_MAGIC = b'UBSH'
RSAS = {
'rsa1024': 1024 / 8,
'rsa2048': 2048 / 8,
'rsa4096': 4096 / 8
}
SHAS = {
'sha256': SHA256,
'sha384': SHA384,
'sha512': SHA512
}
class Entry_pre_load(Entry_collection):
"""Pre load image header
Properties / Entry arguments:
- pre-load-key-path: Path of the directory that store key (provided by
the environment variable PRE_LOAD_KEY_PATH)
- content: List of phandles to entries to sign
- algo-name: Hash and signature algo to use for the signature
- padding-name: Name of the padding (pkcs-1.5 or pss)
- key-name: Filename of the private key to sign
- header-size: Total size of the header
- version: Version of the header
This entry creates a pre-load header that contains a global
image signature.
For example, this creates an image with a pre-load header and a binary::
binman {
image2 {
filename = "sandbox.bin";
pre-load {
content = <&image>;
algo-name = "sha256,rsa2048";
padding-name = "pss";
key-name = "private.pem";
header-size = <4096>;
version = <1>;
};
image: blob-ext {
filename = "sandbox.itb";
};
};
};
"""
def __init__(self, section, etype, node):
super().__init__(section, etype, node)
self.algo_name = fdt_util.GetString(self._node, 'algo-name')
self.padding_name = fdt_util.GetString(self._node, 'padding-name')
self.key_name = fdt_util.GetString(self._node, 'key-name')
self.header_size = fdt_util.GetInt(self._node, 'header-size')
self.version = fdt_util.GetInt(self._node, 'version')
def ReadNode(self):
super().ReadNode()
self.key_path, = self.GetEntryArgsOrProps([EntryArg('pre-load-key-path', str)])
if self.key_path is None:
self.key_path = ''
def _CreateHeader(self):
"""Create a pre load header"""
hash_name, sign_name = self.algo_name.split(',')
padding_name = self.padding_name
key_name = os.path.join(self.key_path, self.key_name)
# Check hash and signature name/type
if hash_name not in SHAS:
self.Raise(hash_name + " is not supported")
if sign_name not in RSAS:
self.Raise(sign_name + " is not supported")
# Read the key
with open(key_name, 'rb') as pem:
key = RSA.import_key(pem.read())
# Check if the key has the expected size
if key.size_in_bytes() != RSAS[sign_name]:
self.Raise("The key " + self.key_name + " don't have the expected size")
# Compute the hash
hash_image = SHAS[hash_name].new()
hash_image.update(self.image)
# Compute the signature
if padding_name is None:
padding_name = "pkcs-1.5"
if padding_name == "pss":
salt_len = key.size_in_bytes() - hash_image.digest_size - 2
padding = pss
padding_args = {'salt_bytes': salt_len}
elif padding_name == "pkcs-1.5":
padding = pkcs1_15
padding_args = {}
else:
self.Raise(padding_name + " is not supported")
sig = padding.new(key, **padding_args).sign(hash_image)
hash_sig = SHA256.new()
hash_sig.update(sig)
version = self.version
header_size = self.header_size
image_size = len(self.image)
ofs_img_sig = 64 + len(sig)
flags = 0
reserved0 = 0
reserved1 = 0
first_header = struct.pack('>4sIIIIIII32s', PRE_LOAD_MAGIC,
version, header_size, image_size,
ofs_img_sig, flags, reserved0,
reserved1, hash_sig.digest())
hash_first_header = SHAS[hash_name].new()
hash_first_header.update(first_header)
sig_first_header = padding.new(key, **padding_args).sign(hash_first_header)
data = first_header + sig_first_header + sig
pad = bytearray(self.header_size - len(data))
return data + pad
def ObtainContents(self):
"""Obtain a placeholder for the header contents"""
# wait that the image is available
self.image = self.GetContents(False)
if self.image is None:
return False
self.SetContents(self._CreateHeader())
return True
def ProcessContents(self):
data = self._CreateHeader()
return self.ProcessContentsUpdate(data)
|
