u-boot/common/image-fit-sig.c
Simon Glass 79af75f777 fit: Don't allow verification of images with @ nodes
When searching for a node called 'fred', any unit address appended to the
name is ignored by libfdt, meaning that 'fred' can match 'fred@1'. This
means that we cannot be sure that the node originally intended is the one
that is used.

Disallow use of nodes with unit addresses.

Update the forge test also, since it uses @ addresses.

CVE-2021-27138

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Bruce Monroe <bruce.monroe@intel.com>
Reported-by: Arie Haenel <arie.haenel@intel.com>
Reported-by: Julien Lenoir <julien.lenoir@intel.com>
2021-02-15 19:17:25 -05:00

483 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (c) 2013, Google Inc.
*/
#ifdef USE_HOSTCC
#include "mkimage.h"
#include <time.h>
#else
#include <common.h>
#include <log.h>
#include <malloc.h>
#include <asm/global_data.h>
DECLARE_GLOBAL_DATA_PTR;
#endif /* !USE_HOSTCC*/
#include <fdt_region.h>
#include <image.h>
#include <u-boot/rsa.h>
#include <u-boot/rsa-checksum.h>
#define IMAGE_MAX_HASHED_NODES 100
/**
* fit_region_make_list() - Make a list of image regions
*
* Given a list of fdt_regions, create a list of image_regions. This is a
* simple conversion routine since the FDT and image code use different
* structures.
*
* @fit: FIT image
* @fdt_regions: Pointer to FDT regions
* @count: Number of FDT regions
* @region: Pointer to image regions, which must hold @count records. If
* region is NULL, then (except for an SPL build) the array will be
* allocated.
* @return: Pointer to image regions
*/
struct image_region *fit_region_make_list(const void *fit,
struct fdt_region *fdt_regions,
int count,
struct image_region *region)
{
int i;
debug("Hash regions:\n");
debug("%10s %10s\n", "Offset", "Size");
/*
* Use malloc() except in SPL (to save code size). In SPL the caller
* must allocate the array.
*/
#ifndef CONFIG_SPL_BUILD
if (!region)
region = calloc(sizeof(*region), count);
#endif
if (!region)
return NULL;
for (i = 0; i < count; i++) {
debug("%10x %10x\n", fdt_regions[i].offset,
fdt_regions[i].size);
region[i].data = fit + fdt_regions[i].offset;
region[i].size = fdt_regions[i].size;
}
return region;
}
static int fit_image_setup_verify(struct image_sign_info *info,
const void *fit, int noffset,
int required_keynode, char **err_msgp)
{
char *algo_name;
const char *padding_name;
if (fdt_totalsize(fit) > CONFIG_FIT_SIGNATURE_MAX_SIZE) {
*err_msgp = "Total size too large";
return 1;
}
if (fit_image_hash_get_algo(fit, noffset, &algo_name)) {
*err_msgp = "Can't get hash algo property";
return -1;
}
padding_name = fdt_getprop(fit, noffset, "padding", NULL);
if (!padding_name)
padding_name = RSA_DEFAULT_PADDING_NAME;
memset(info, '\0', sizeof(*info));
info->keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
info->fit = (void *)fit;
info->node_offset = noffset;
info->name = algo_name;
info->checksum = image_get_checksum_algo(algo_name);
info->crypto = image_get_crypto_algo(algo_name);
info->padding = image_get_padding_algo(padding_name);
info->fdt_blob = gd_fdt_blob();
info->required_keynode = required_keynode;
printf("%s:%s", algo_name, info->keyname);
if (!info->checksum || !info->crypto || !info->padding) {
*err_msgp = "Unknown signature algorithm";
return -1;
}
return 0;
}
int fit_image_check_sig(const void *fit, int noffset, const void *data,
size_t size, int required_keynode, char **err_msgp)
{
struct image_sign_info info;
struct image_region region;
uint8_t *fit_value;
int fit_value_len;
*err_msgp = NULL;
if (fit_image_setup_verify(&info, fit, noffset, required_keynode,
err_msgp))
return -1;
if (fit_image_hash_get_value(fit, noffset, &fit_value,
&fit_value_len)) {
*err_msgp = "Can't get hash value property";
return -1;
}
region.data = data;
region.size = size;
if (info.crypto->verify(&info, &region, 1, fit_value, fit_value_len)) {
*err_msgp = "Verification failed";
return -1;
}
return 0;
}
static int fit_image_verify_sig(const void *fit, int image_noffset,
const char *data, size_t size,
const void *sig_blob, int sig_offset)
{
int noffset;
char *err_msg = "";
int verified = 0;
int ret;
/* Process all hash subnodes of the component image node */
fdt_for_each_subnode(noffset, fit, image_noffset) {
const char *name = fit_get_name(fit, noffset, NULL);
/*
* We don't support this since libfdt considers names with the
* name root but different @ suffix to be equal
*/
if (strchr(name, '@')) {
err_msg = "Node name contains @";
goto error;
}
if (!strncmp(name, FIT_SIG_NODENAME,
strlen(FIT_SIG_NODENAME))) {
ret = fit_image_check_sig(fit, noffset, data,
size, -1, &err_msg);
if (ret) {
puts("- ");
} else {
puts("+ ");
verified = 1;
break;
}
}
}
if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
err_msg = "Corrupted or truncated tree";
goto error;
}
return verified ? 0 : -EPERM;
error:
printf(" error!\n%s for '%s' hash node in '%s' image node\n",
err_msg, fit_get_name(fit, noffset, NULL),
fit_get_name(fit, image_noffset, NULL));
return -1;
}
int fit_image_verify_required_sigs(const void *fit, int image_noffset,
const char *data, size_t size,
const void *sig_blob, int *no_sigsp)
{
int verify_count = 0;
int noffset;
int sig_node;
/* Work out what we need to verify */
*no_sigsp = 1;
sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
if (sig_node < 0) {
debug("%s: No signature node found: %s\n", __func__,
fdt_strerror(sig_node));
return 0;
}
fdt_for_each_subnode(noffset, sig_blob, sig_node) {
const char *required;
int ret;
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,
sig_blob, noffset);
if (ret) {
printf("Failed to verify required signature '%s'\n",
fit_get_name(sig_blob, noffset, NULL));
return ret;
}
verify_count++;
}
if (verify_count)
*no_sigsp = 0;
return 0;
}
/**
* 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", "data-size", "data-position"};
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));
*err_msgp = NULL;
if (fit_image_setup_verify(&info, fit, noffset, required_keynode,
err_msgp))
return -1;
if (fit_image_hash_get_value(fit, noffset, &fit_value,
&fit_value_len)) {
*err_msgp = "Can't get hash value property";
return -1;
}
/* Count the number of strings in the property */
prop = fdt_getprop(fit, noffset, "hashed-nodes", &prop_len);
end = prop ? prop + prop_len : prop;
for (name = prop, count = 0; name < end; name++)
if (!*name)
count++;
if (!count) {
*err_msgp = "Can't get hashed-nodes property";
return -1;
}
if (prop && prop_len > 0 && prop[prop_len - 1] != '\0') {
*err_msgp = "hashed-nodes property must be null-terminated";
return -1;
}
/* Add a sanity check here since we are using the stack */
if (count > IMAGE_MAX_HASHED_NODES) {
*err_msgp = "Number of hashed nodes exceeds maximum";
return -1;
}
/* Create a list of node names from those strings */
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;
}
/*
* Each node can generate one region for each sub-node. Allow for
* 7 sub-nodes (hash-1, signature-1, etc.) and some extra.
*/
max_regions = 20 + count * 7;
struct fdt_region fdt_regions[max_regions];
/* Get a list of regions to hash */
count = fdt_find_regions(fit, node_inc, count,
exc_prop, ARRAY_SIZE(exc_prop),
fdt_regions, max_regions - 1,
path, sizeof(path), 0);
if (count < 0) {
*err_msgp = "Failed to hash configuration";
return -1;
}
if (count == 0) {
*err_msgp = "No data to hash";
return -1;
}
if (count >= max_regions - 1) {
*err_msgp = "Too many hash regions";
return -1;
}
/* Add the strings */
strings = fdt_getprop(fit, noffset, "hashed-strings", NULL);
if (strings) {
/*
* The strings region offset must be a static 0x0.
* This is set in tool/image-host.c
*/
fdt_regions[count].offset = fdt_off_dt_strings(fit);
fdt_regions[count].size = fdt32_to_cpu(strings[1]);
count++;
}
/* Allocate the region list on the stack */
struct image_region region[count];
fit_region_make_list(fit, fdt_regions, count, region);
if (info.crypto->verify(&info, region, count, fit_value,
fit_value_len)) {
*err_msgp = "Verification failed";
return -1;
}
return 0;
}
static int fit_config_verify_sig(const void *fit, int conf_noffset,
const void *sig_blob, int sig_offset)
{
int noffset;
char *err_msg = "No 'signature' subnode found";
int verified = 0;
int ret;
/* Process all hash subnodes of the component conf node */
fdt_for_each_subnode(noffset, fit, conf_noffset) {
const char *name = fit_get_name(fit, noffset, NULL);
if (!strncmp(name, FIT_SIG_NODENAME,
strlen(FIT_SIG_NODENAME))) {
ret = fit_config_check_sig(fit, noffset, sig_offset,
conf_noffset, &err_msg);
if (ret) {
puts("- ");
} else {
puts("+ ");
verified = 1;
break;
}
}
}
if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
err_msg = "Corrupted or truncated tree";
goto error;
}
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 -EPERM;
}
static int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
const void *sig_blob)
{
const char *name = fit_get_name(fit, conf_noffset, NULL);
int noffset;
int sig_node;
int verified = 0;
int reqd_sigs = 0;
bool reqd_policy_all = true;
const char *reqd_mode;
/*
* We don't support this since libfdt considers names with the
* name root but different @ suffix to be equal
*/
if (strchr(name, '@')) {
printf("Configuration node '%s' contains '@'\n", name);
return -EPERM;
}
/* Work out what we need to verify */
sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
if (sig_node < 0) {
debug("%s: No signature node found: %s\n", __func__,
fdt_strerror(sig_node));
return 0;
}
/* Get required-mode policy property from DTB */
reqd_mode = fdt_getprop(sig_blob, sig_node, "required-mode", NULL);
if (reqd_mode && !strcmp(reqd_mode, "any"))
reqd_policy_all = false;
debug("%s: required-mode policy set to '%s'\n", __func__,
reqd_policy_all ? "all" : "any");
fdt_for_each_subnode(noffset, sig_blob, sig_node) {
const char *required;
int ret;
required = fdt_getprop(sig_blob, noffset, FIT_KEY_REQUIRED,
NULL);
if (!required || strcmp(required, "conf"))
continue;
reqd_sigs++;
ret = fit_config_verify_sig(fit, conf_noffset, sig_blob,
noffset);
if (ret) {
if (reqd_policy_all) {
printf("Failed to verify required signature '%s'\n",
fit_get_name(sig_blob, noffset, NULL));
return ret;
}
} else {
verified++;
if (!reqd_policy_all)
break;
}
}
if (reqd_sigs && !verified) {
printf("Failed to verify 'any' of the required signature(s)\n");
return -EPERM;
}
return 0;
}
int fit_config_verify(const void *fit, int conf_noffset)
{
return fit_config_verify_required_sigs(fit, conf_noffset,
gd_fdt_blob());
}