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Vboot vulnerability fix

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Merge tag 'dm-pull-1apr20' of git://git.denx.de/u-boot-dm

Vboot vulnerability fix
This commit is contained in:
Tom Rini 2020-04-01 14:29:21 -04:00
commit e0718b3ab7
11 changed files with 602 additions and 119 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
common/bootm.c
View file

@ -819,7 +819,8 @@ void __weak switch_to_non_secure_mode(void)
#else /* USE_HOSTCC */
#if defined(CONFIG_FIT_SIGNATURE)
static int bootm_host_load_image(const void *fit, int req_image_type)
static int bootm_host_load_image(const void *fit, int req_image_type,
int cfg_noffset)
{
const char *fit_uname_config = NULL;
ulong data, len;
@ -831,6 +832,7 @@ static int bootm_host_load_image(const void *fit, int req_image_type)
void *load_buf;
int ret;
fit_uname_config = fdt_get_name(fit, cfg_noffset, NULL);
memset(&images, '\0', sizeof(images));
images.verify = 1;
noffset = fit_image_load(&images, (ulong)fit,
@ -878,7 +880,7 @@ int bootm_host_load_images(const void *fit, int cfg_noffset)
for (i = 0; i < ARRAY_SIZE(image_types); i++) {
int ret;
ret = bootm_host_load_image(fit, image_types[i]);
ret = bootm_host_load_image(fit, image_types[i], cfg_noffset);
if (!err && ret && ret != -ENOENT)
err = ret;
}

2
common/image-cipher.c
View file

@ -88,7 +88,7 @@ static int fit_image_setup_decrypt(struct image_cipher_info *info,
return -1;
}
info->keyname = fdt_getprop(fit, cipher_noffset, "key-name-hint", NULL);
info->keyname = fdt_getprop(fit, cipher_noffset, FIT_KEY_HINT, NULL);
if (!info->keyname) {
printf("Can't get key name\n");
return -1;

26
common/image-fit.c
View file

@ -168,7 +168,7 @@ static void fit_image_print_data(const void *fit, int noffset, const char *p,
int value_len;
char *algo;
const char *padding;
int required;
bool required;
int ret, i;
debug("%s %s node: '%s'\n", p, type,
@ -179,8 +179,8 @@ static void fit_image_print_data(const void *fit, int noffset, const char *p,
return;
}
printf("%s", algo);
keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
required = fdt_getprop(fit, noffset, "required", NULL) != NULL;
keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
required = fdt_getprop(fit, noffset, FIT_KEY_REQUIRED, NULL) != NULL;
if (keyname)
printf(":%s", keyname);
if (required)
@ -1712,24 +1712,6 @@ int fit_conf_find_compat(const void *fit, const void *fdt)
return best_match_offset;
}
/**
* fit_conf_get_node - get node offset for configuration of a given unit name
* @fit: pointer to the FIT format image header
* @conf_uname: configuration node unit name
*
* fit_conf_get_node() finds a configuration (within the '/configurations'
* parent node) of a provided unit name. If configuration is found its node
* offset is returned to the caller.
*
* When NULL is provided in second argument fit_conf_get_node() will search
* for a default configuration node instead. Default configuration node unit
* name is retrieved from FIT_DEFAULT_PROP property of the '/configurations'
* node.
*
* returns:
* configuration node offset when found (>=0)
* negative number on failure (FDT_ERR_* code)
*/
int fit_conf_get_node(const void *fit, const char *conf_uname)
{
int noffset, confs_noffset;
@ -1969,7 +1951,7 @@ int fit_image_load(bootm_headers_t *images, ulong addr,
fit_uname = fit_get_name(fit, noffset, NULL);
}
if (noffset < 0) {
puts("Could not find subimage node\n");
printf("Could not find subimage node type '%s'\n", prop_name);
bootstage_error(bootstage_id + BOOTSTAGE_SUB_SUBNODE);
return -ENOENT;
}

49
common/image-sig.c
View file

@ -229,7 +229,7 @@ static int fit_image_setup_verify(struct image_sign_info *info,
padding_name = RSA_DEFAULT_PADDING_NAME;
memset(info, '\0', sizeof(*info));
info->keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
info->keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
info->fit = (void *)fit;
info->node_offset = noffset;
info->name = algo_name;
@ -340,7 +340,8 @@ int fit_image_verify_required_sigs(const void *fit, int image_noffset,
const char *required;
int ret;
required = fdt_getprop(sig_blob, noffset, "required", NULL);
required = fdt_getprop(sig_blob, noffset, FIT_KEY_REQUIRED,
NULL);
if (!required || strcmp(required, "image"))
continue;
ret = fit_image_verify_sig(fit, image_noffset, data, size,
@ -359,20 +360,39 @@ int fit_image_verify_required_sigs(const void *fit, int image_noffset,
return 0;
}
int fit_config_check_sig(const void *fit, int noffset, int required_keynode,
char **err_msgp)
/**
* fit_config_check_sig() - Check the signature of a config
*
* @fit: FIT to check
* @noffset: Offset of configuration node (e.g. /configurations/conf-1)
* @required_keynode: Offset in the control FDT of the required key node,
* if any. If this is given, then the configuration wil not
* pass verification unless that key is used. If this is
* -1 then any signature will do.
* @conf_noffset: Offset of the configuration subnode being checked (e.g.
* /configurations/conf-1/kernel)
* @err_msgp: In the event of an error, this will be pointed to a
* help error string to display to the user.
* @return 0 if all verified ok, <0 on error
*/
static int fit_config_check_sig(const void *fit, int noffset,
int required_keynode, int conf_noffset,
char **err_msgp)
{
char * const exc_prop[] = {"data"};
const char *prop, *end, *name;
struct image_sign_info info;
const uint32_t *strings;
const char *config_name;
uint8_t *fit_value;
int fit_value_len;
bool found_config;
int max_regions;
int i, prop_len;
char path[200];
int count;
config_name = fit_get_name(fit, conf_noffset, NULL);
debug("%s: fdt=%p, conf='%s', sig='%s'\n", __func__, gd_fdt_blob(),
fit_get_name(fit, noffset, NULL),
fit_get_name(gd_fdt_blob(), required_keynode, NULL));
@ -413,9 +433,20 @@ int fit_config_check_sig(const void *fit, int noffset, int required_keynode,
char *node_inc[count];
debug("Hash nodes (%d):\n", count);
found_config = false;
for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) {
debug(" '%s'\n", name);
node_inc[i] = (char *)name;
if (!strncmp(FIT_CONFS_PATH, name, strlen(FIT_CONFS_PATH)) &&
name[sizeof(FIT_CONFS_PATH) - 1] == '/' &&
!strcmp(name + sizeof(FIT_CONFS_PATH), config_name)) {
debug(" (found config node %s)", config_name);
found_config = true;
}
}
if (!found_config) {
*err_msgp = "Selected config not in hashed nodes";
return -1;
}
/*
@ -483,7 +514,7 @@ static int fit_config_verify_sig(const void *fit, int conf_noffset,
if (!strncmp(name, FIT_SIG_NODENAME,
strlen(FIT_SIG_NODENAME))) {
ret = fit_config_check_sig(fit, noffset, sig_offset,
&err_msg);
conf_noffset, &err_msg);
if (ret) {
puts("- ");
} else {
@ -499,13 +530,14 @@ static int fit_config_verify_sig(const void *fit, int conf_noffset,
goto error;
}
return verified ? 0 : -EPERM;
if (verified)
return 0;
error:
printf(" error!\n%s for '%s' hash node in '%s' config node\n",
err_msg, fit_get_name(fit, noffset, NULL),
fit_get_name(fit, conf_noffset, NULL));
return -1;
return -EPERM;
}
int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
@ -526,7 +558,8 @@ int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
const char *required;
int ret;
required = fdt_getprop(sig_blob, noffset, "required", NULL);
required = fdt_getprop(sig_blob, noffset, FIT_KEY_REQUIRED,
NULL);
if (!required || strcmp(required, "conf"))
continue;
ret = fit_config_verify_sig(fit, conf_noffset, sig_blob,

24
include/image.h
View file

@ -939,12 +939,14 @@ int booti_setup(ulong image, ulong *relocated_addr, ulong *size,
#define FIT_IMAGES_PATH "/images"
#define FIT_CONFS_PATH "/configurations"
/* hash/signature node */
/* hash/signature/key node */
#define FIT_HASH_NODENAME "hash"
#define FIT_ALGO_PROP "algo"
#define FIT_VALUE_PROP "value"
#define FIT_IGNORE_PROP "uboot-ignore"
#define FIT_SIG_NODENAME "signature"
#define FIT_KEY_REQUIRED "required"
#define FIT_KEY_HINT "key-name-hint"
/* cipher node */
#define FIT_CIPHER_NODENAME "cipher"
@ -1092,7 +1094,27 @@ int fit_image_check_comp(const void *fit, int noffset, uint8_t comp);
int fit_check_format(const void *fit);
int fit_conf_find_compat(const void *fit, const void *fdt);
/**
* fit_conf_get_node - get node offset for configuration of a given unit name
* @fit: pointer to the FIT format image header
* @conf_uname: configuration node unit name (NULL to use default)
*
* fit_conf_get_node() finds a configuration (within the '/configurations'
* parent node) of a provided unit name. If configuration is found its node
* offset is returned to the caller.
*
* When NULL is provided in second argument fit_conf_get_node() will search
* for a default configuration node instead. Default configuration node unit
* name is retrieved from FIT_DEFAULT_PROP property of the '/configurations'
* node.
*
* returns:
* configuration node offset when found (>=0)
* negative number on failure (FDT_ERR_* code)
*/
int fit_conf_get_node(const void *fit, const char *conf_uname);
int fit_conf_get_prop_node_count(const void *fit, int noffset,
const char *prop_name);
int fit_conf_get_prop_node_index(const void *fit, int noffset,

6
lib/rsa/rsa-sign.c
View file

@ -792,8 +792,8 @@ int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
}
if (!ret) {
ret = fdt_setprop_string(keydest, node, "key-name-hint",
info->keyname);
ret = fdt_setprop_string(keydest, node, FIT_KEY_HINT,
info->keyname);
}
if (!ret)
ret = fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
@ -815,7 +815,7 @@ int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
info->name);
}
if (!ret && info->require_keys) {
ret = fdt_setprop_string(keydest, node, "required",
ret = fdt_setprop_string(keydest, node, FIT_KEY_REQUIRED,
info->require_keys);
}
done:

157
test/py/tests/test_vboot.py
View file

@ -24,10 +24,18 @@ For configuration verification:
Tests run with both SHA1 and SHA256 hashing.
"""
import pytest
import sys
import struct
import pytest
import u_boot_utils as util
import vboot_forge
TESTDATA = [
['sha1', '', False],
['sha1', '-pss', False],
['sha256', '', False],
['sha256', '-pss', False],
['sha256', '-pss', True],
]
@pytest.mark.boardspec('sandbox')
@pytest.mark.buildconfigspec('fit_signature')
@ -35,7 +43,8 @@ import u_boot_utils as util
@pytest.mark.requiredtool('fdtget')
@pytest.mark.requiredtool('fdtput')
@pytest.mark.requiredtool('openssl')
def test_vboot(u_boot_console):
@pytest.mark.parametrize("sha_algo,padding,required", TESTDATA)
def test_vboot(u_boot_console, sha_algo, padding, required):
"""Test verified boot signing with mkimage and verification with 'bootm'.
This works using sandbox only as it needs to update the device tree used
@ -75,13 +84,14 @@ def test_vboot(u_boot_console):
with cons.log.section('Verified boot %s %s' % (sha_algo, test_type)):
output = cons.run_command_list(
['host load hostfs - 100 %stest.fit' % tmpdir,
'fdt addr 100',
'bootm 100'])
assert(expect_string in ''.join(output))
'fdt addr 100',
'bootm 100'])
assert expect_string in ''.join(output)
if boots:
assert('sandbox: continuing, as we cannot run' in ''.join(output))
assert 'sandbox: continuing, as we cannot run' in ''.join(output)
else:
assert('sandbox: continuing, as we cannot run' not in ''.join(output))
assert('sandbox: continuing, as we cannot run'
not in ''.join(output))
def make_fit(its):
"""Make a new FIT from the .its source file.
@ -108,20 +118,6 @@ def test_vboot(u_boot_console):
util.run_and_log(cons, [mkimage, '-F', '-k', tmpdir, '-K', dtb,
'-r', fit])
def sign_fit_norequire(sha_algo):
"""Sign the FIT
Signs the FIT and writes the signature into it. It also writes the
public key into the dtb.
Args:
sha_algo: Either 'sha1' or 'sha256', to select the algorithm to
use.
"""
cons.log.action('%s: Sign images' % sha_algo)
util.run_and_log(cons, [mkimage, '-F', '-k', tmpdir, '-K', dtb,
fit])
def replace_fit_totalsize(size):
"""Replace FIT header's totalsize with something greater.
@ -142,6 +138,22 @@ def test_vboot(u_boot_console):
handle.write(struct.pack(">I", size))
return struct.unpack(">I", total_size)[0]
def create_rsa_pair(name):
"""Generate a new RSA key paid and certificate
Args:
name: Name of of the key (e.g. 'dev')
"""
public_exponent = 65537
util.run_and_log(cons, 'openssl genpkey -algorithm RSA -out %s%s.key '
'-pkeyopt rsa_keygen_bits:2048 '
'-pkeyopt rsa_keygen_pubexp:%d' %
(tmpdir, name, public_exponent))
# Create a certificate containing the public key
util.run_and_log(cons, 'openssl req -batch -new -x509 -key %s%s.key '
'-out %s%s.crt' % (tmpdir, name, tmpdir, name))
def test_with_algo(sha_algo, padding):
"""Test verified boot with the given hash algorithm.
@ -160,7 +172,7 @@ def test_vboot(u_boot_console):
# Build the FIT, but don't sign anything yet
cons.log.action('%s: Test FIT with signed images' % sha_algo)
make_fit('sign-images-%s%s.its' % (sha_algo , padding))
make_fit('sign-images-%s%s.its' % (sha_algo, padding))
run_bootm(sha_algo, 'unsigned images', 'dev-', True)
# Sign images with our dev keys
@ -171,7 +183,7 @@ def test_vboot(u_boot_console):
dtc('sandbox-u-boot.dts')
cons.log.action('%s: Test FIT with signed configuration' % sha_algo)
make_fit('sign-configs-%s%s.its' % (sha_algo , padding))
make_fit('sign-configs-%s%s.its' % (sha_algo, padding))
run_bootm(sha_algo, 'unsigned config', '%s+ OK' % sha_algo, True)
# Sign images with our dev keys
@ -180,14 +192,29 @@ def test_vboot(u_boot_console):
cons.log.action('%s: Check signed config on the host' % sha_algo)
util.run_and_log(cons, [fit_check_sign, '-f', fit, '-k', tmpdir,
'-k', dtb])
util.run_and_log(cons, [fit_check_sign, '-f', fit, '-k', dtb])
# Replace header bytes
# Make sure that U-Boot checks that the config is in the list of hashed
# nodes. If it isn't, a security bypass is possible.
with open(fit, 'rb') as fd:
root, strblock = vboot_forge.read_fdt(fd)
root, strblock = vboot_forge.manipulate(root, strblock)
with open(fit, 'w+b') as fd:
vboot_forge.write_fdt(root, strblock, fd)
util.run_and_log_expect_exception(
cons, [fit_check_sign, '-f', fit, '-k', dtb],
1, 'Failed to verify required signature')
run_bootm(sha_algo, 'forged config', 'Bad Data Hash', False)
# Create a new properly signed fit and replace header bytes
make_fit('sign-configs-%s%s.its' % (sha_algo, padding))
sign_fit(sha_algo)
bcfg = u_boot_console.config.buildconfig
max_size = int(bcfg.get('config_fit_signature_max_size', 0x10000000), 0)
existing_size = replace_fit_totalsize(max_size + 1)
run_bootm(sha_algo, 'Signed config with bad hash', 'Bad Data Hash', False)
run_bootm(sha_algo, 'Signed config with bad hash', 'Bad Data Hash',
False)
cons.log.action('%s: Check overflowed FIT header totalsize' % sha_algo)
# Replace with existing header bytes
@ -205,21 +232,22 @@ def test_vboot(u_boot_console):
util.run_and_log(cons, 'fdtput -t bx %s %s value %s' %
(fit, sig_node, sig))
run_bootm(sha_algo, 'Signed config with bad hash', 'Bad Data Hash', False)
run_bootm(sha_algo, 'Signed config with bad hash', 'Bad Data Hash',
False)
cons.log.action('%s: Check bad config on the host' % sha_algo)
util.run_and_log_expect_exception(cons, [fit_check_sign, '-f', fit,
'-k', dtb], 1, 'Failed to verify required signature')
util.run_and_log_expect_exception(
cons, [fit_check_sign, '-f', fit, '-k', dtb],
1, 'Failed to verify required signature')
def test_required_key(sha_algo, padding):
"""Test verified boot with the given hash algorithm.
This function test if u-boot reject an image when a required
key isn't used to sign a FIT.
This function tests if U-Boot rejects an image when a required key isn't
used to sign a FIT.
Args:
sha_algo: Either 'sha1' or 'sha256', to select the algorithm to
use.
sha_algo: Either 'sha1' or 'sha256', to select the algorithm to use
"""
# Compile our device tree files for kernel and U-Boot. These are
# regenerated here since mkimage will modify them (by adding a
@ -227,22 +255,27 @@ def test_vboot(u_boot_console):
dtc('sandbox-kernel.dts')
dtc('sandbox-u-boot.dts')
# Build the FIT with prod key (keys required)
# Build the FIT with dev key (keys NOT required)
# The dtb contain the key prod and dev and the key prod are set as required.
# Then try to boot the FIT with dev key
# This FIT should not be accepted by u-boot because the key prod is required
cons.log.action('%s: Test FIT with configs images' % sha_algo)
make_fit('sign-configs-%s%s-prod.its' % (sha_algo , padding))
sign_fit(sha_algo)
make_fit('sign-configs-%s%s.its' % (sha_algo , padding))
# Build the FIT with prod key (keys required) and sign it. This puts the
# signature into sandbox-u-boot.dtb, marked 'required'
make_fit('sign-configs-%s%s-prod.its' % (sha_algo, padding))
sign_fit(sha_algo)
run_bootm(sha_algo, 'signed configs', '', False)
# Build the FIT with dev key (keys NOT required). This adds the
# signature into sandbox-u-boot.dtb, NOT marked 'required'.
make_fit('sign-configs-%s%s.its' % (sha_algo, padding))
sign_fit(sha_algo)
# So now sandbox-u-boot.dtb two signatures, for the prod and dev keys.
# Only the prod key is set as 'required'. But FIT we just built has
# a dev signature only (sign_fit() overwrites the FIT).
# Try to boot the FIT with dev key. This FIT should not be accepted by
# U-Boot because the prod key is required.
run_bootm(sha_algo, 'required key', '', False)
cons = u_boot_console
tmpdir = cons.config.result_dir + '/'
tmp = tmpdir + 'vboot.tmp'
datadir = cons.config.source_dir + '/test/py/tests/vboot/'
fit = '%stest.fit' % tmpdir
mkimage = cons.config.build_dir + '/tools/mkimage'
@ -251,42 +284,22 @@ def test_vboot(u_boot_console):
dtb = '%ssandbox-u-boot.dtb' % tmpdir
sig_node = '/configurations/conf-1/signature'
# Create an RSA key pair
public_exponent = 65537
util.run_and_log(cons, 'openssl genpkey -algorithm RSA -out %sdev.key '
'-pkeyopt rsa_keygen_bits:2048 '
'-pkeyopt rsa_keygen_pubexp:%d' %
(tmpdir, public_exponent))
# Create a certificate containing the public key
util.run_and_log(cons, 'openssl req -batch -new -x509 -key %sdev.key -out '
'%sdev.crt' % (tmpdir, tmpdir))
# Create an RSA key pair (prod)
public_exponent = 65537
util.run_and_log(cons, 'openssl genpkey -algorithm RSA -out %sprod.key '
'-pkeyopt rsa_keygen_bits:2048 '
'-pkeyopt rsa_keygen_pubexp:%d' %
(tmpdir, public_exponent))
# Create a certificate containing the public key (prod)
util.run_and_log(cons, 'openssl req -batch -new -x509 -key %sprod.key -out '
'%sprod.crt' % (tmpdir, tmpdir))
create_rsa_pair('dev')
create_rsa_pair('prod')
# Create a number kernel image with zeroes
with open('%stest-kernel.bin' % tmpdir, 'w') as fd:
fd.write(5000 * chr(0))
fd.write(500 * chr(0))
try:
# We need to use our own device tree file. Remember to restore it
# afterwards.
old_dtb = cons.config.dtb
cons.config.dtb = dtb
test_with_algo('sha1','')
test_with_algo('sha1','-pss')
test_with_algo('sha256','')
test_with_algo('sha256','-pss')
test_required_key('sha256','-pss')
if required:
test_required_key(sha_algo, padding)
else:
test_with_algo(sha_algo, padding)
finally:
# Go back to the original U-Boot with the correct dtb.
cons.config.dtb = old_dtb

423
test/py/tests/vboot_forge.py Normal file
View file

@ -0,0 +1,423 @@
#!/usr/bin/python3
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2020, F-Secure Corporation, https://foundry.f-secure.com
#
# pylint: disable=E1101,W0201,C0103
"""
Verified boot image forgery tools and utilities
This module provides services to both take apart and regenerate FIT images
in a way that preserves all existing verified boot signatures, unless you
manipulate nodes in the process.
"""
import struct
import binascii
from io import BytesIO
#
# struct parsing helpers
#
class BetterStructMeta(type):
"""
Preprocesses field definitions and creates a struct.Struct instance from them
"""
def __new__(cls, clsname, superclasses, attributedict):
if clsname != 'BetterStruct':
fields = attributedict['__fields__']
field_types = [_[0] for _ in fields]
field_names = [_[1] for _ in fields if _[1] is not None]
attributedict['__names__'] = field_names
s = struct.Struct(attributedict.get('__endian__', '') + ''.join(field_types))
attributedict['__struct__'] = s
attributedict['size'] = s.size
return type.__new__(cls, clsname, superclasses, attributedict)
class BetterStruct(metaclass=BetterStructMeta):
"""
Base class for better structures
"""
def __init__(self):
for t, n in self.__fields__:
if 's' in t:
setattr(self, n, '')
elif t in ('Q', 'I', 'H', 'B'):
setattr(self, n, 0)
@classmethod
def unpack_from(cls, buffer, offset=0):
"""
Unpack structure instance from a buffer
"""
fields = cls.__struct__.unpack_from(buffer, offset)
instance = cls()
for n, v in zip(cls.__names__, fields):
setattr(instance, n, v)
return instance
def pack(self):
"""
Pack structure instance into bytes
"""
return self.__struct__.pack(*[getattr(self, n) for n in self.__names__])
def __str__(self):
items = ["'%s': %s" % (n, repr(getattr(self, n))) for n in self.__names__ if n is not None]
return '(' + ', '.join(items) + ')'
#
# some defs for flat DT data
#
class HeaderV17(BetterStruct):
__endian__ = '>'
__fields__ = [
('I', 'magic'),
('I', 'totalsize'),
('I', 'off_dt_struct'),
('I', 'off_dt_strings'),
('I', 'off_mem_rsvmap'),
('I', 'version'),
('I', 'last_comp_version'),
('I', 'boot_cpuid_phys'),
('I', 'size_dt_strings'),
('I', 'size_dt_struct'),
]
class RRHeader(BetterStruct):
__endian__ = '>'
__fields__ = [
('Q', 'address'),
('Q', 'size'),
]
class PropHeader(BetterStruct):
__endian__ = '>'
__fields__ = [
('I', 'value_size'),
('I', 'name_offset'),
]
# magical constants for DTB format
OF_DT_HEADER = 0xd00dfeed
OF_DT_BEGIN_NODE = 1
OF_DT_END_NODE = 2
OF_DT_PROP = 3
OF_DT_END = 9
class StringsBlock:
"""
Represents a parsed device tree string block
"""
def __init__(self, values=None):
if values is None:
self.values = []
else:
self.values = values
def __getitem__(self, at):
if isinstance(at, str):
offset = 0
for value in self.values:
if value == at:
break
offset += len(value) + 1
else:
self.values.append(at)
return offset
if isinstance(at, int):
offset = 0
for value in self.values:
if offset == at:
return value
offset += len(value) + 1
raise IndexError('no string found corresponding to the given offset')
raise TypeError('only strings and integers are accepted')
class Prop:
"""
Represents a parsed device tree property
"""
def __init__(self, name=None, value=None):
self.name = name
self.value = value
def clone(self):
return Prop(self.name, self.value)
def __repr__(self):
return "<Prop(name='%s', value=%s>" % (self.name, repr(self.value))
class Node:
"""
Represents a parsed device tree node
"""
def __init__(self, name=None):
self.name = name
self.props = []
self.children = []
def clone(self):
o = Node(self.name)
o.props = [x.clone() for x in self.props]
o.children = [x.clone() for x in self.children]
return o
def __getitem__(self, index):
return self.children[index]
def __repr__(self):
return "<Node('%s'), %s, %s>" % (self.name, repr(self.props), repr(self.children))
#
# flat DT to memory
#
def parse_strings(strings):
"""
Converts the bytes into a StringsBlock instance so it is convenient to work with
"""
strings = strings.split(b'\x00')
return StringsBlock(strings)
def parse_struct(stream):
"""
Parses DTB structure(s) into a Node or Prop instance
"""
tag = bytearray(stream.read(4))[3]
if tag == OF_DT_BEGIN_NODE:
name = b''
while b'\x00' not in name:
name += stream.read(4)
name = name.rstrip(b'\x00')
node = Node(name)
item = parse_struct(stream)
while item is not None:
if isinstance(item, Node):
node.children.append(item)
elif isinstance(item, Prop):
node.props.append(item)
item = parse_struct(stream)
return node
if tag == OF_DT_PROP:
h = PropHeader.unpack_from(stream.read(PropHeader.size))
length = (h.value_size + 3) & (~3)
value = stream.read(length)[:h.value_size]
prop = Prop(h.name_offset, value)
return prop
if tag in (OF_DT_END_NODE, OF_DT_END):
return None
raise ValueError('unexpected tag value')
def read_fdt(fp):
"""
Reads and parses the flattened device tree (or derivatives like FIT)
"""
header = HeaderV17.unpack_from(fp.read(HeaderV17.size))
if header.magic != OF_DT_HEADER:
raise ValueError('invalid magic value %08x; expected %08x' % (header.magic, OF_DT_HEADER))
# TODO: read/parse reserved regions
fp.seek(header.off_dt_struct)
structs = fp.read(header.size_dt_struct)
fp.seek(header.off_dt_strings)
strings = fp.read(header.size_dt_strings)
strblock = parse_strings(strings)
root = parse_struct(BytesIO(structs))
return root, strblock
#
# memory to flat DT
#
def compose_structs_r(item):
"""
Recursive part of composing Nodes and Props into a bytearray
"""
t = bytearray()
if isinstance(item, Node):
t.extend(struct.pack('>I', OF_DT_BEGIN_NODE))
if isinstance(item.name, str):
item.name = bytes(item.name, 'utf-8')
name = item.name + b'\x00'
if len(name) & 3:
name += b'\x00' * (4 - (len(name) & 3))
t.extend(name)
for p in item.props:
t.extend(compose_structs_r(p))
for c in item.children:
t.extend(compose_structs_r(c))
t.extend(struct.pack('>I', OF_DT_END_NODE))
elif isinstance(item, Prop):
t.extend(struct.pack('>I', OF_DT_PROP))
value = item.value
h = PropHeader()
h.name_offset = item.name
if value:
h.value_size = len(value)
t.extend(h.pack())
if len(value) & 3:
value += b'\x00' * (4 - (len(value) & 3))
t.extend(value)
else:
h.value_size = 0
t.extend(h.pack())
return t
def compose_structs(root):
"""
Composes the parsed Nodes into a flat bytearray instance
"""
t = compose_structs_r(root)
t.extend(struct.pack('>I', OF_DT_END))
return t
def compose_strings(strblock):
"""
Composes the StringsBlock instance back into a bytearray instance
"""
b = bytearray()
for s in strblock.values:
b.extend(s)
b.append(0)
return bytes(b)
def write_fdt(root, strblock, fp):
"""
Writes out a complete flattened device tree (or FIT)
"""
header = HeaderV17()
header.magic = OF_DT_HEADER
header.version = 17
header.last_comp_version = 16
fp.write(header.pack())
header.off_mem_rsvmap = fp.tell()
fp.write(RRHeader().pack())
structs = compose_structs(root)
header.off_dt_struct = fp.tell()
header.size_dt_struct = len(structs)
fp.write(structs)
strings = compose_strings(strblock)
header.off_dt_strings = fp.tell()
header.size_dt_strings = len(strings)
fp.write(strings)
header.totalsize = fp.tell()
fp.seek(0)
fp.write(header.pack())
#
# pretty printing / converting to DT source
#
def as_bytes(value):
return ' '.join(["%02X" % x for x in value])
def prety_print_value(value):
"""
Formats a property value as appropriate depending on the guessed data type
"""
if not value:
return '""'
if value[-1] == b'\x00':
printable = True
for x in value[:-1]:
x = ord(x)
if x != 0 and (x < 0x20 or x > 0x7F):
printable = False
break
if printable:
value = value[:-1]
return ', '.join('"' + x + '"' for x in value.split(b'\x00'))
if len(value) > 0x80:
return '[' + as_bytes(value[:0x80]) + ' ... ]'
return '[' + as_bytes(value) + ']'
def pretty_print_r(node, strblock, indent=0):
"""
Prints out a single node, recursing further for each of its children
"""
spaces = ' ' * indent
print((spaces + '%s {' % (node.name.decode('utf-8') if node.name else '/')))
for p in node.props:
print((spaces + ' %s = %s;' % (strblock[p.name].decode('utf-8'), prety_print_value(p.value))))
for c in node.children:
pretty_print_r(c, strblock, indent+1)
print((spaces + '};'))
def pretty_print(node, strblock):
"""
Generates an almost-DTS formatted printout of the parsed device tree
"""
print('/dts-v1/;')
pretty_print_r(node, strblock, 0)
#
# manipulating the DT structure
#
def manipulate(root, strblock):
"""
Maliciously manipulates the structure to create a crafted FIT file
"""
# locate /images/kernel@1 (frankly, it just expects it to be the first one)
kernel_node = root[0][0]
# clone it to save time filling all the properties
fake_kernel = kernel_node.clone()
# rename the node
fake_kernel.name = b'kernel@2'
# get rid of signatures/hashes
fake_kernel.children = []
# NOTE: this simply replaces the first prop... either description or data
# should be good for testing purposes
fake_kernel.props[0].value = b'Super 1337 kernel\x00'
# insert the new kernel node under /images
root[0].children.append(fake_kernel)
# modify the default configuration
root[1].props[0].value = b'conf@2\x00'
# clone the first (only?) configuration
fake_conf = root[1][0].clone()
# rename and change kernel and fdt properties to select the crafted kernel
fake_conf.name = b'conf@2'
fake_conf.props[0].value = b'kernel@2\x00'
fake_conf.props[1].value = b'fdt@1\x00'
# insert the new configuration under /configurations
root[1].children.append(fake_conf)
return root, strblock
def main(argv):
with open(argv[1], 'rb') as fp:
root, strblock = read_fdt(fp)
print("Before:")
pretty_print(root, strblock)
root, strblock = manipulate(root, strblock)
print("After:")
pretty_print(root, strblock)
with open('blah', 'w+b') as fp:
write_fdt(root, strblock, fp)
if __name__ == '__main__':
import sys
main(sys.argv)
# EOF

3
tools/fdt_host.h
View file

@ -27,6 +27,7 @@
*/
int fdt_remove_unused_strings(const void *old, void *new);
int fit_check_sign(const void *working_fdt, const void *key);
int fit_check_sign(const void *fit, const void *key,
const char *fit_uname_config);
#endif /* __FDT_HOST_H__ */

8
tools/fit_check_sign.c
View file

@ -41,6 +41,7 @@ int main(int argc, char **argv)
void *fit_blob;
char *fdtfile = NULL;
char *keyfile = NULL;
char *config_name = NULL;
char cmdname[256];
int ret;
void *key_blob;
@ -48,7 +49,7 @@ int main(int argc, char **argv)
strncpy(cmdname, *argv, sizeof(cmdname) - 1);
cmdname[sizeof(cmdname) - 1] = '\0';
while ((c = getopt(argc, argv, "f:k:")) != -1)
while ((c = getopt(argc, argv, "f:k:c:")) != -1)
switch (c) {
case 'f':
fdtfile = optarg;
@ -56,6 +57,9 @@ int main(int argc, char **argv)
case 'k':
keyfile = optarg;
break;
case 'c':
config_name = optarg;
break;
default:
usage(cmdname);
break;
@ -78,7 +82,7 @@ int main(int argc, char **argv)
return EXIT_FAILURE;
image_set_host_blob(key_blob);
ret = fit_check_sign(fit_blob, key_blob);
ret = fit_check_sign(fit_blob, key_blob, config_name);
if (!ret) {
ret = EXIT_SUCCESS;
fprintf(stderr, "Signature check OK\n");

17
tools/image-host.c
View file

@ -170,7 +170,7 @@ static int fit_image_setup_sig(struct image_sign_info *info,
memset(info, '\0', sizeof(*info));
info->keydir = keydir;
info->keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
info->keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
info->fit = fit;
info->node_offset = noffset;
info->name = strdup(algo_name);
@ -249,7 +249,7 @@ static int fit_image_process_sig(const char *keydir, void *keydest,
free(value);
/* Get keyname again, as FDT has changed and invalidated our pointer */
info.keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
info.keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
/*
* Write the public key into the supplied FDT file; this might fail
@ -337,7 +337,7 @@ static int fit_image_setup_cipher(struct image_cipher_info *info,
info->keydir = keydir;
/* Read the key name */
info->keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
info->keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
if (!info->keyname) {
printf("Can't get key name for cipher '%s' in image '%s'\n",
node_name, image_name);
@ -886,7 +886,7 @@ static int fit_config_process_sig(const char *keydir, void *keydest,
free(region_prop);
/* Get keyname again, as FDT has changed and invalidated our pointer */
info.keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
info.keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
/* Write the public key into the supplied FDT file */
if (keydest) {
@ -1025,19 +1025,22 @@ int fit_add_verification_data(const char *keydir, void *keydest, void *fit,
}
#ifdef CONFIG_FIT_SIGNATURE
int fit_check_sign(const void *fit, const void *key)
int fit_check_sign(const void *fit, const void *key,
const char *fit_uname_config)
{
int cfg_noffset;
int ret;
cfg_noffset = fit_conf_get_node(fit, NULL);
cfg_noffset = fit_conf_get_node(fit, fit_uname_config);
if (!cfg_noffset)
return -1;
printf("Verifying Hash Integrity ... ");
printf("Verifying Hash Integrity for node '%s'... ",
fdt_get_name(fit, cfg_noffset, NULL));
ret = fit_config_verify(fit, cfg_noffset);
if (ret)
return ret;
printf("Verified OK, loading images\n");
ret = bootm_host_load_images(fit, cfg_noffset);
return ret;