// 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/hex.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_VERITYstatic bool deny_reading_verity_digests;#endif // initialized to falsestatic bool loadpin_root_writable;#ifdef CONFIG_SYSCTL static int proc_handler_loadpin(const struct ctl_table *table, int dir,				void *buffer, size_t *lenp, loff_t *ppos){	if (!loadpin_root_writable && SYSCTL_USER_TO_KERN(dir))		return -EINVAL;	return proc_dointvec_minmax(table, dir, buffer, lenp, ppos);} static const struct ctl_table loadpin_sysctl_table[] = {	{		.procname       = "enforce",		.data           = &enforce,		.maxlen         = sizeof(int),		.mode           = 0644,		.proc_handler   = proc_handler_loadpin,		.extra1         = SYSCTL_ZERO,		.extra2         = SYSCTL_ONE,	},};#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; 	/* 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; 	/* 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) {		loadpin_root_writable = sb_is_writable(pinned_root);		report_writable(pinned_root, loadpin_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;} #ifdef CONFIG_SECURITY_LOADPIN_VERITY enum loadpin_securityfs_interface_index {	LOADPIN_DM_VERITY,}; static int read_trusted_verity_root_digests(unsigned int fd){	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; 	CLASS(fd, f)(fd);	if (fd_empty(f))		return -EINVAL; 	data = kzalloc(SZ_4K, GFP_KERNEL);	if (!data) {		rc = -ENOMEM;		goto err;	} 	rc = kernel_read_file(fd_file(f), 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_flex(*trd, data, len);		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); 	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; 	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;} #endif /* CONFIG_SECURITY_LOADPIN_VERITY */ DEFINE_LSM(loadpin) = {	.id = &loadpin_lsmid,	.init = loadpin_init,#ifdef CONFIG_SECURITY_LOADPIN_VERITY	.initcall_fs = 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");