mirror of
https://github.com/torvalds/linux.git
synced 2024-12-05 18:41:23 +00:00
b1a867eeb8
As the kernel test robot helpfully reminded us, all of the lsm_id instances defined inside the various LSMs should be marked as static. The one exception is Landlock which uses its lsm_id variable across multiple source files with an extern declaration in a header file. Reported-by: kernel test robot <lkp@intel.com> Suggested-by: Casey Schaufler <casey@schaufler-ca.com> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
451 lines
11 KiB
C
451 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* Module and Firmware Pinning Security Module
|
|
*
|
|
* Copyright 2011-2016 Google Inc.
|
|
*
|
|
* Author: Kees Cook <keescook@chromium.org>
|
|
*/
|
|
|
|
#define pr_fmt(fmt) "LoadPin: " fmt
|
|
|
|
#include <linux/module.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/kernel_read_file.h>
|
|
#include <linux/lsm_hooks.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/blkdev.h>
|
|
#include <linux/path.h>
|
|
#include <linux/sched.h> /* current */
|
|
#include <linux/string_helpers.h>
|
|
#include <linux/dm-verity-loadpin.h>
|
|
#include <uapi/linux/loadpin.h>
|
|
#include <uapi/linux/lsm.h>
|
|
|
|
#define VERITY_DIGEST_FILE_HEADER "# LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS"
|
|
|
|
static void report_load(const char *origin, struct file *file, char *operation)
|
|
{
|
|
char *cmdline, *pathname;
|
|
|
|
pathname = kstrdup_quotable_file(file, GFP_KERNEL);
|
|
cmdline = kstrdup_quotable_cmdline(current, GFP_KERNEL);
|
|
|
|
pr_notice("%s %s obj=%s%s%s pid=%d cmdline=%s%s%s\n",
|
|
origin, operation,
|
|
(pathname && pathname[0] != '<') ? "\"" : "",
|
|
pathname,
|
|
(pathname && pathname[0] != '<') ? "\"" : "",
|
|
task_pid_nr(current),
|
|
cmdline ? "\"" : "", cmdline, cmdline ? "\"" : "");
|
|
|
|
kfree(cmdline);
|
|
kfree(pathname);
|
|
}
|
|
|
|
static int enforce = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCE);
|
|
static char *exclude_read_files[READING_MAX_ID];
|
|
static int ignore_read_file_id[READING_MAX_ID] __ro_after_init;
|
|
static struct super_block *pinned_root;
|
|
static DEFINE_SPINLOCK(pinned_root_spinlock);
|
|
#ifdef CONFIG_SECURITY_LOADPIN_VERITY
|
|
static bool deny_reading_verity_digests;
|
|
#endif
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
static struct ctl_table loadpin_sysctl_table[] = {
|
|
{
|
|
.procname = "enforce",
|
|
.data = &enforce,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec_minmax,
|
|
.extra1 = SYSCTL_ONE,
|
|
.extra2 = SYSCTL_ONE,
|
|
},
|
|
{ }
|
|
};
|
|
|
|
static void set_sysctl(bool is_writable)
|
|
{
|
|
/*
|
|
* If load pinning is not enforced via a read-only block
|
|
* device, allow sysctl to change modes for testing.
|
|
*/
|
|
if (is_writable)
|
|
loadpin_sysctl_table[0].extra1 = SYSCTL_ZERO;
|
|
else
|
|
loadpin_sysctl_table[0].extra1 = SYSCTL_ONE;
|
|
}
|
|
#else
|
|
static inline void set_sysctl(bool is_writable) { }
|
|
#endif
|
|
|
|
static void report_writable(struct super_block *mnt_sb, bool writable)
|
|
{
|
|
if (mnt_sb->s_bdev) {
|
|
pr_info("%pg (%u:%u): %s\n", mnt_sb->s_bdev,
|
|
MAJOR(mnt_sb->s_bdev->bd_dev),
|
|
MINOR(mnt_sb->s_bdev->bd_dev),
|
|
writable ? "writable" : "read-only");
|
|
} else
|
|
pr_info("mnt_sb lacks block device, treating as: writable\n");
|
|
|
|
if (!writable)
|
|
pr_info("load pinning engaged.\n");
|
|
}
|
|
|
|
/*
|
|
* This must be called after early kernel init, since then the rootdev
|
|
* is available.
|
|
*/
|
|
static bool sb_is_writable(struct super_block *mnt_sb)
|
|
{
|
|
bool writable = true;
|
|
|
|
if (mnt_sb->s_bdev)
|
|
writable = !bdev_read_only(mnt_sb->s_bdev);
|
|
|
|
return writable;
|
|
}
|
|
|
|
static void loadpin_sb_free_security(struct super_block *mnt_sb)
|
|
{
|
|
/*
|
|
* When unmounting the filesystem we were using for load
|
|
* pinning, we acknowledge the superblock release, but make sure
|
|
* no other modules or firmware can be loaded when we are in
|
|
* enforcing mode. Otherwise, allow the root to be reestablished.
|
|
*/
|
|
if (!IS_ERR_OR_NULL(pinned_root) && mnt_sb == pinned_root) {
|
|
if (enforce) {
|
|
pinned_root = ERR_PTR(-EIO);
|
|
pr_info("umount pinned fs: refusing further loads\n");
|
|
} else {
|
|
pinned_root = NULL;
|
|
}
|
|
}
|
|
}
|
|
|
|
static int loadpin_check(struct file *file, enum kernel_read_file_id id)
|
|
{
|
|
struct super_block *load_root;
|
|
const char *origin = kernel_read_file_id_str(id);
|
|
bool first_root_pin = false;
|
|
bool load_root_writable;
|
|
|
|
/* If the file id is excluded, ignore the pinning. */
|
|
if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) &&
|
|
ignore_read_file_id[id]) {
|
|
report_load(origin, file, "pinning-excluded");
|
|
return 0;
|
|
}
|
|
|
|
/* This handles the older init_module API that has a NULL file. */
|
|
if (!file) {
|
|
if (!enforce) {
|
|
report_load(origin, NULL, "old-api-pinning-ignored");
|
|
return 0;
|
|
}
|
|
|
|
report_load(origin, NULL, "old-api-denied");
|
|
return -EPERM;
|
|
}
|
|
|
|
load_root = file->f_path.mnt->mnt_sb;
|
|
load_root_writable = sb_is_writable(load_root);
|
|
|
|
/* First loaded module/firmware defines the root for all others. */
|
|
spin_lock(&pinned_root_spinlock);
|
|
/*
|
|
* pinned_root is only NULL at startup or when the pinned root has
|
|
* been unmounted while we are not in enforcing mode. Otherwise, it
|
|
* is either a valid reference, or an ERR_PTR.
|
|
*/
|
|
if (!pinned_root) {
|
|
pinned_root = load_root;
|
|
first_root_pin = true;
|
|
}
|
|
spin_unlock(&pinned_root_spinlock);
|
|
|
|
if (first_root_pin) {
|
|
report_writable(pinned_root, load_root_writable);
|
|
set_sysctl(load_root_writable);
|
|
report_load(origin, file, "pinned");
|
|
}
|
|
|
|
if (IS_ERR_OR_NULL(pinned_root) ||
|
|
((load_root != pinned_root) && !dm_verity_loadpin_is_bdev_trusted(load_root->s_bdev))) {
|
|
if (unlikely(!enforce)) {
|
|
report_load(origin, file, "pinning-ignored");
|
|
return 0;
|
|
}
|
|
|
|
report_load(origin, file, "denied");
|
|
return -EPERM;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int loadpin_read_file(struct file *file, enum kernel_read_file_id id,
|
|
bool contents)
|
|
{
|
|
/*
|
|
* LoadPin only cares about the _origin_ of a file, not its
|
|
* contents, so we can ignore the "are full contents available"
|
|
* argument here.
|
|
*/
|
|
return loadpin_check(file, id);
|
|
}
|
|
|
|
static int loadpin_load_data(enum kernel_load_data_id id, bool contents)
|
|
{
|
|
/*
|
|
* LoadPin only cares about the _origin_ of a file, not its
|
|
* contents, so a NULL file is passed, and we can ignore the
|
|
* state of "contents".
|
|
*/
|
|
return loadpin_check(NULL, (enum kernel_read_file_id) id);
|
|
}
|
|
|
|
static const struct lsm_id loadpin_lsmid = {
|
|
.name = "loadpin",
|
|
.id = LSM_ID_LOADPIN,
|
|
};
|
|
|
|
static struct security_hook_list loadpin_hooks[] __ro_after_init = {
|
|
LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
|
|
LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
|
|
LSM_HOOK_INIT(kernel_load_data, loadpin_load_data),
|
|
};
|
|
|
|
static void __init parse_exclude(void)
|
|
{
|
|
int i, j;
|
|
char *cur;
|
|
|
|
/*
|
|
* Make sure all the arrays stay within expected sizes. This
|
|
* is slightly weird because kernel_read_file_str[] includes
|
|
* READING_MAX_ID, which isn't actually meaningful here.
|
|
*/
|
|
BUILD_BUG_ON(ARRAY_SIZE(exclude_read_files) !=
|
|
ARRAY_SIZE(ignore_read_file_id));
|
|
BUILD_BUG_ON(ARRAY_SIZE(kernel_read_file_str) <
|
|
ARRAY_SIZE(ignore_read_file_id));
|
|
|
|
for (i = 0; i < ARRAY_SIZE(exclude_read_files); i++) {
|
|
cur = exclude_read_files[i];
|
|
if (!cur)
|
|
break;
|
|
if (*cur == '\0')
|
|
continue;
|
|
|
|
for (j = 0; j < ARRAY_SIZE(ignore_read_file_id); j++) {
|
|
if (strcmp(cur, kernel_read_file_str[j]) == 0) {
|
|
pr_info("excluding: %s\n",
|
|
kernel_read_file_str[j]);
|
|
ignore_read_file_id[j] = 1;
|
|
/*
|
|
* Can not break, because one read_file_str
|
|
* may map to more than on read_file_id.
|
|
*/
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
static int __init loadpin_init(void)
|
|
{
|
|
pr_info("ready to pin (currently %senforcing)\n",
|
|
enforce ? "" : "not ");
|
|
parse_exclude();
|
|
#ifdef CONFIG_SYSCTL
|
|
if (!register_sysctl("kernel/loadpin", loadpin_sysctl_table))
|
|
pr_notice("sysctl registration failed!\n");
|
|
#endif
|
|
security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks),
|
|
&loadpin_lsmid);
|
|
|
|
return 0;
|
|
}
|
|
|
|
DEFINE_LSM(loadpin) = {
|
|
.name = "loadpin",
|
|
.init = loadpin_init,
|
|
};
|
|
|
|
#ifdef CONFIG_SECURITY_LOADPIN_VERITY
|
|
|
|
enum loadpin_securityfs_interface_index {
|
|
LOADPIN_DM_VERITY,
|
|
};
|
|
|
|
static int read_trusted_verity_root_digests(unsigned int fd)
|
|
{
|
|
struct fd f;
|
|
void *data;
|
|
int rc;
|
|
char *p, *d;
|
|
|
|
if (deny_reading_verity_digests)
|
|
return -EPERM;
|
|
|
|
/* The list of trusted root digests can only be set up once */
|
|
if (!list_empty(&dm_verity_loadpin_trusted_root_digests))
|
|
return -EPERM;
|
|
|
|
f = fdget(fd);
|
|
if (!f.file)
|
|
return -EINVAL;
|
|
|
|
data = kzalloc(SZ_4K, GFP_KERNEL);
|
|
if (!data) {
|
|
rc = -ENOMEM;
|
|
goto err;
|
|
}
|
|
|
|
rc = kernel_read_file(f.file, 0, (void **)&data, SZ_4K - 1, NULL, READING_POLICY);
|
|
if (rc < 0)
|
|
goto err;
|
|
|
|
p = data;
|
|
p[rc] = '\0';
|
|
p = strim(p);
|
|
|
|
p = strim(data);
|
|
while ((d = strsep(&p, "\n")) != NULL) {
|
|
int len;
|
|
struct dm_verity_loadpin_trusted_root_digest *trd;
|
|
|
|
if (d == data) {
|
|
/* first line, validate header */
|
|
if (strcmp(d, VERITY_DIGEST_FILE_HEADER)) {
|
|
rc = -EPROTO;
|
|
goto err;
|
|
}
|
|
|
|
continue;
|
|
}
|
|
|
|
len = strlen(d);
|
|
|
|
if (len % 2) {
|
|
rc = -EPROTO;
|
|
goto err;
|
|
}
|
|
|
|
len /= 2;
|
|
|
|
trd = kzalloc(struct_size(trd, data, len), GFP_KERNEL);
|
|
if (!trd) {
|
|
rc = -ENOMEM;
|
|
goto err;
|
|
}
|
|
trd->len = len;
|
|
|
|
if (hex2bin(trd->data, d, len)) {
|
|
kfree(trd);
|
|
rc = -EPROTO;
|
|
goto err;
|
|
}
|
|
|
|
list_add_tail(&trd->node, &dm_verity_loadpin_trusted_root_digests);
|
|
}
|
|
|
|
if (list_empty(&dm_verity_loadpin_trusted_root_digests)) {
|
|
rc = -EPROTO;
|
|
goto err;
|
|
}
|
|
|
|
kfree(data);
|
|
fdput(f);
|
|
|
|
return 0;
|
|
|
|
err:
|
|
kfree(data);
|
|
|
|
/* any failure in loading/parsing invalidates the entire list */
|
|
{
|
|
struct dm_verity_loadpin_trusted_root_digest *trd, *tmp;
|
|
|
|
list_for_each_entry_safe(trd, tmp, &dm_verity_loadpin_trusted_root_digests, node) {
|
|
list_del(&trd->node);
|
|
kfree(trd);
|
|
}
|
|
}
|
|
|
|
/* disallow further attempts after reading a corrupt/invalid file */
|
|
deny_reading_verity_digests = true;
|
|
|
|
fdput(f);
|
|
|
|
return rc;
|
|
}
|
|
|
|
/******************************** securityfs ********************************/
|
|
|
|
static long dm_verity_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
|
|
{
|
|
void __user *uarg = (void __user *)arg;
|
|
unsigned int fd;
|
|
|
|
switch (cmd) {
|
|
case LOADPIN_IOC_SET_TRUSTED_VERITY_DIGESTS:
|
|
if (copy_from_user(&fd, uarg, sizeof(fd)))
|
|
return -EFAULT;
|
|
|
|
return read_trusted_verity_root_digests(fd);
|
|
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
static const struct file_operations loadpin_dm_verity_ops = {
|
|
.unlocked_ioctl = dm_verity_ioctl,
|
|
.compat_ioctl = compat_ptr_ioctl,
|
|
};
|
|
|
|
/**
|
|
* init_loadpin_securityfs - create the securityfs directory for LoadPin
|
|
*
|
|
* We can not put this method normally under the loadpin_init() code path since
|
|
* the security subsystem gets initialized before the vfs caches.
|
|
*
|
|
* Returns 0 if the securityfs directory creation was successful.
|
|
*/
|
|
static int __init init_loadpin_securityfs(void)
|
|
{
|
|
struct dentry *loadpin_dir, *dentry;
|
|
|
|
loadpin_dir = securityfs_create_dir("loadpin", NULL);
|
|
if (IS_ERR(loadpin_dir)) {
|
|
pr_err("LoadPin: could not create securityfs dir: %ld\n",
|
|
PTR_ERR(loadpin_dir));
|
|
return PTR_ERR(loadpin_dir);
|
|
}
|
|
|
|
dentry = securityfs_create_file("dm-verity", 0600, loadpin_dir,
|
|
(void *)LOADPIN_DM_VERITY, &loadpin_dm_verity_ops);
|
|
if (IS_ERR(dentry)) {
|
|
pr_err("LoadPin: could not create securityfs entry 'dm-verity': %ld\n",
|
|
PTR_ERR(dentry));
|
|
return PTR_ERR(dentry);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
fs_initcall(init_loadpin_securityfs);
|
|
|
|
#endif /* CONFIG_SECURITY_LOADPIN_VERITY */
|
|
|
|
/* Should not be mutable after boot, so not listed in sysfs (perm == 0). */
|
|
module_param(enforce, int, 0);
|
|
MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning");
|
|
module_param_array_named(exclude, exclude_read_files, charp, NULL, 0);
|
|
MODULE_PARM_DESC(exclude, "Exclude pinning specific read file types");
|