ima_policy.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2008 IBM Corporation
 * Author: Mimi Zohar <zohar@us.ibm.com>
 *
 * ima_policy.c
 *	- initialize default measure policy rules
 */

#include <linux/init.h>
#include <linux/list.h>
#include <linux/kernel_read_file.h>
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/magic.h>
#include <linux/parser.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include <linux/seq_file.h>
#include <linux/ima.h>

#include "ima.h"

/* flags definitions */
#define IMA_FUNC	0x0001
#define IMA_MASK	0x0002
#define IMA_FSMAGIC	0x0004
#define IMA_UID		0x0008
#define IMA_FOWNER	0x0010
#define IMA_FSUUID	0x0020
#define IMA_INMASK	0x0040
#define IMA_EUID	0x0080
#define IMA_PCR		0x0100
#define IMA_FSNAME	0x0200
#define IMA_KEYRINGS	0x0400
#define IMA_LABEL	0x0800
#define IMA_VALIDATE_ALGOS	0x1000
#define IMA_GID		0x2000
#define IMA_EGID	0x4000
#define IMA_FGROUP	0x8000

#define UNKNOWN		0
#define MEASURE		0x0001	/* same as IMA_MEASURE */
#define DONT_MEASURE	0x0002
#define APPRAISE	0x0004	/* same as IMA_APPRAISE */
#define DONT_APPRAISE	0x0008
#define AUDIT		0x0040
#define HASH		0x0100
#define DONT_HASH	0x0200

#define INVALID_PCR(a) (((a) < 0) || \
	(a) >= (sizeof_field(struct ima_iint_cache, measured_pcrs) * 8))

int ima_policy_flag;
static int temp_ima_appraise;
static int build_ima_appraise __ro_after_init;

atomic_t ima_setxattr_allowed_hash_algorithms;

#define MAX_LSM_RULES 6
enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
	LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
};

enum policy_types { ORIGINAL_TCB = 1, DEFAULT_TCB };

enum policy_rule_list { IMA_DEFAULT_POLICY = 1, IMA_CUSTOM_POLICY };

struct ima_rule_opt_list {
	size_t count;
	char *items[] __counted_by(count);
};

/*
 * These comparators are needed nowhere outside of ima so just define them here.
 * This pattern should hopefully never be needed outside of ima.
 */
static inline bool vfsuid_gt_kuid(vfsuid_t vfsuid, kuid_t kuid)
{
	return __vfsuid_val(vfsuid) > __kuid_val(kuid);
}

static inline bool vfsgid_gt_kgid(vfsgid_t vfsgid, kgid_t kgid)
{
	return __vfsgid_val(vfsgid) > __kgid_val(kgid);
}

static inline bool vfsuid_lt_kuid(vfsuid_t vfsuid, kuid_t kuid)
{
	return __vfsuid_val(vfsuid) < __kuid_val(kuid);
}

static inline bool vfsgid_lt_kgid(vfsgid_t vfsgid, kgid_t kgid)
{
	return __vfsgid_val(vfsgid) < __kgid_val(kgid);
}

struct ima_rule_entry {
	struct list_head list;
	int action;
	unsigned int flags;
	enum ima_hooks func;
	int mask;
	unsigned long fsmagic;
	uuid_t fsuuid;
	kuid_t uid;
	kgid_t gid;
	kuid_t fowner;
	kgid_t fgroup;
	bool (*uid_op)(kuid_t cred_uid, kuid_t rule_uid);    /* Handlers for operators       */
	bool (*gid_op)(kgid_t cred_gid, kgid_t rule_gid);
	bool (*fowner_op)(vfsuid_t vfsuid, kuid_t rule_uid); /* vfsuid_eq_kuid(), vfsuid_gt_kuid(), vfsuid_lt_kuid() */
	bool (*fgroup_op)(vfsgid_t vfsgid, kgid_t rule_gid); /* vfsgid_eq_kgid(), vfsgid_gt_kgid(), vfsgid_lt_kgid() */
	int pcr;
	unsigned int allowed_algos; /* bitfield of allowed hash algorithms */
	struct {
		void *rule;	/* LSM file metadata specific */
		char *args_p;	/* audit value */
		int type;	/* audit type */
	} lsm[MAX_LSM_RULES];
	char *fsname;
	struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
	struct ima_rule_opt_list *label; /* Measure data grouped under this label */
	struct ima_template_desc *template;
};

/*
 * sanity check in case the kernels gains more hash algorithms that can
 * fit in an unsigned int
 */
static_assert(
	8 * sizeof(unsigned int) >= HASH_ALGO__LAST,
	"The bitfield allowed_algos in ima_rule_entry is too small to contain all the supported hash algorithms, consider using a bigger type");

/*
 * Without LSM specific knowledge, the default policy can only be
 * written in terms of .action, .func, .mask, .fsmagic, .uid, .gid,
 * .fowner, and .fgroup
 */

/*
 * The minimum rule set to allow for full TCB coverage.  Measures all files
 * opened or mmap for exec and everything read by root.  Dangerous because
 * normal users can easily run the machine out of memory simply building
 * and running executables.
 */
static struct ima_rule_entry dont_measure_rules[] __ro_after_init = {
	{.action = DONT_MEASURE, .fsmagic = PROC_SUPER_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = SYSFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = DEBUGFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = TMPFS_MAGIC, .func = FILE_CHECK,
	 .flags = IMA_FSMAGIC | IMA_FUNC},
	{.action = DONT_MEASURE, .fsmagic = DEVPTS_SUPER_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = BINFMTFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = SECURITYFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = SELINUX_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = SMACK_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = CGROUP_SUPER_MAGIC,
	 .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = CGROUP2_SUPER_MAGIC,
	 .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_MEASURE, .fsmagic = EFIVARFS_MAGIC, .flags = IMA_FSMAGIC}
};

static struct ima_rule_entry original_measurement_rules[] __ro_after_init = {
	{.action = MEASURE, .func = MMAP_CHECK, .mask = MAY_EXEC,
	 .flags = IMA_FUNC | IMA_MASK},
	{.action = MEASURE, .func = BPRM_CHECK, .mask = MAY_EXEC,
	 .flags = IMA_FUNC | IMA_MASK},
	{.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
	 .uid = GLOBAL_ROOT_UID, .uid_op = &uid_eq,
	 .flags = IMA_FUNC | IMA_MASK | IMA_UID},
	{.action = MEASURE, .func = MODULE_CHECK, .flags = IMA_FUNC},
	{.action = MEASURE, .func = FIRMWARE_CHECK, .flags = IMA_FUNC},
};

static struct ima_rule_entry default_measurement_rules[] __ro_after_init = {
	{.action = MEASURE, .func = MMAP_CHECK, .mask = MAY_EXEC,
	 .flags = IMA_FUNC | IMA_MASK},
	{.action = MEASURE, .func = BPRM_CHECK, .mask = MAY_EXEC,
	 .flags = IMA_FUNC | IMA_MASK},
	{.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
	 .uid = GLOBAL_ROOT_UID, .uid_op = &uid_eq,
	 .flags = IMA_FUNC | IMA_INMASK | IMA_EUID},
	{.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
	 .uid = GLOBAL_ROOT_UID, .uid_op = &uid_eq,
	 .flags = IMA_FUNC | IMA_INMASK | IMA_UID},
	{.action = MEASURE, .func = MODULE_CHECK, .flags = IMA_FUNC},
	{.action = MEASURE, .func = FIRMWARE_CHECK, .flags = IMA_FUNC},
	{.action = MEASURE, .func = POLICY_CHECK, .flags = IMA_FUNC},
};

static struct ima_rule_entry default_appraise_rules[] __ro_after_init = {
	{.action = DONT_APPRAISE, .fsmagic = PROC_SUPER_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = SYSFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = DEBUGFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = TMPFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = RAMFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = DEVPTS_SUPER_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = BINFMTFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = SECURITYFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = SELINUX_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = SMACK_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = EFIVARFS_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = CGROUP_SUPER_MAGIC, .flags = IMA_FSMAGIC},
	{.action = DONT_APPRAISE, .fsmagic = CGROUP2_SUPER_MAGIC, .flags = IMA_FSMAGIC},
#ifdef CONFIG_IMA_WRITE_POLICY
	{.action = APPRAISE, .func = POLICY_CHECK,
	.flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
#endif
#ifndef CONFIG_IMA_APPRAISE_SIGNED_INIT
	{.action = APPRAISE, .fowner = GLOBAL_ROOT_UID, .fowner_op = &vfsuid_eq_kuid,
	 .flags = IMA_FOWNER},
#else
	/* force signature */
	{.action = APPRAISE, .fowner = GLOBAL_ROOT_UID, .fowner_op = &vfsuid_eq_kuid,
	 .flags = IMA_FOWNER | IMA_DIGSIG_REQUIRED},
#endif
};

static struct ima_rule_entry build_appraise_rules[] __ro_after_init = {
#ifdef CONFIG_IMA_APPRAISE_REQUIRE_MODULE_SIGS
	{.action = APPRAISE, .func = MODULE_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
#endif
#ifdef CONFIG_IMA_APPRAISE_REQUIRE_FIRMWARE_SIGS
	{.action = APPRAISE, .func = FIRMWARE_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
#endif
#ifdef CONFIG_IMA_APPRAISE_REQUIRE_KEXEC_SIGS
	{.action = APPRAISE, .func = KEXEC_KERNEL_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
#endif
#ifdef CONFIG_IMA_APPRAISE_REQUIRE_POLICY_SIGS
	{.action = APPRAISE, .func = POLICY_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
#endif
};

static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
	{.action = APPRAISE, .func = MODULE_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
	{.action = APPRAISE, .func = FIRMWARE_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
	{.action = APPRAISE, .func = KEXEC_KERNEL_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
	{.action = APPRAISE, .func = POLICY_CHECK,
	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
};

static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
	{.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
};

/* An array of architecture specific rules */
static struct ima_rule_entry *arch_policy_entry __ro_after_init;

static LIST_HEAD(ima_default_rules);
static LIST_HEAD(ima_policy_rules);
static LIST_HEAD(ima_temp_rules);
static struct list_head __rcu *ima_rules = (struct list_head __rcu *)(&ima_default_rules);

static int ima_policy __initdata;

static int __init default_measure_policy_setup(char *str)
{
	if (ima_policy)
		return 1;

	ima_policy = ORIGINAL_TCB;
	return 1;
}
__setup("ima_tcb", default_measure_policy_setup);

static bool ima_use_appraise_tcb __initdata;
static bool ima_use_secure_boot __initdata;
static bool ima_use_critical_data __initdata;
static bool ima_fail_unverifiable_sigs __ro_after_init;
static int __init policy_setup(char *str)
{
	char *p;

	while ((p = strsep(&str, " |\n")) != NULL) {
		if (*p == ' ')
			continue;
		if ((strcmp(p, "tcb") == 0) && !ima_policy)
			ima_policy = DEFAULT_TCB;
		else if (strcmp(p, "appraise_tcb") == 0)
			ima_use_appraise_tcb = true;
		else if (strcmp(p, "secure_boot") == 0)
			ima_use_secure_boot = true;
		else if (strcmp(p, "critical_data") == 0)
			ima_use_critical_data = true;
		else if (strcmp(p, "fail_securely") == 0)
			ima_fail_unverifiable_sigs = true;
		else
			pr_err("policy \"%s\" not found", p);
	}

	return 1;
}
__setup("ima_policy=", policy_setup);

static int __init default_appraise_policy_setup(char *str)
{
	ima_use_appraise_tcb = true;
	return 1;
}
__setup("ima_appraise_tcb", default_appraise_policy_setup);

static struct ima_rule_opt_list *ima_alloc_rule_opt_list(const substring_t *src)
{
	struct ima_rule_opt_list *opt_list;
	size_t count = 0;
	char *src_copy;
	char *cur, *next;
	size_t i;

	src_copy = match_strdup(src);
	if (!src_copy)
		return ERR_PTR(-ENOMEM);

	next = src_copy;
	while ((cur = strsep(&next, "|"))) {
		/* Don't accept an empty list item */
		if (!(*cur)) {
			kfree(src_copy);
			return ERR_PTR(-EINVAL);
		}
		count++;
	}

	/* Don't accept an empty list */
	if (!count) {
		kfree(src_copy);
		return ERR_PTR(-EINVAL);
	}

	opt_list = kzalloc(struct_size(opt_list, items, count), GFP_KERNEL);
	if (!opt_list) {
		kfree(src_copy);
		return ERR_PTR(-ENOMEM);
	}
	opt_list->count = count;

	/*
	 * strsep() has already replaced all instances of '|' with '\0',
	 * leaving a byte sequence of NUL-terminated strings. Reference each
	 * string with the array of items.
	 *
	 * IMPORTANT: Ownership of the allocated buffer is transferred from
	 * src_copy to the first element in the items array. To free the
	 * buffer, kfree() must only be called on the first element of the
	 * array.
	 */
	for (i = 0, cur = src_copy; i < count; i++) {
		opt_list->items[i] = cur;
		cur = strchr(cur, '\0') + 1;
	}

	return opt_list;
}

static void ima_free_rule_opt_list(struct ima_rule_opt_list *opt_list)
{
	if (!opt_list)
		return;

	if (opt_list->count) {
		kfree(opt_list->items[0]);
		opt_list->count = 0;
	}

	kfree(opt_list);
}

static void ima_lsm_free_rule(struct ima_rule_entry *entry)
{
	int i;

	for (i = 0; i < MAX_LSM_RULES; i++) {
		ima_filter_rule_free(entry->lsm[i].rule);
		kfree(entry->lsm[i].args_p);
	}
}

static void ima_free_rule(struct ima_rule_entry *entry)
{
	if (!entry)
		return;

	/*
	 * entry->template->fields may be allocated in ima_parse_rule() but that
	 * reference is owned by the corresponding ima_template_desc element in
	 * the defined_templates list and cannot be freed here
	 */
	kfree(entry->fsname);
	ima_free_rule_opt_list(entry->keyrings);
	ima_lsm_free_rule(entry);
	kfree(entry);
}

static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry,
						gfp_t gfp)
{
	struct ima_rule_entry *nentry;
	int i;

	/*
	 * Immutable elements are copied over as pointers and data; only
	 * lsm rules can change
	 */
	nentry = kmemdup(entry, sizeof(*nentry), gfp);
	if (!nentry)
		return NULL;

	memset(nentry->lsm, 0, sizeof_field(struct ima_rule_entry, lsm));

	for (i = 0; i < MAX_LSM_RULES; i++) {
		if (!entry->lsm[i].args_p)
			continue;

		nentry->lsm[i].type = entry->lsm[i].type;
		nentry->lsm[i].args_p = entry->lsm[i].args_p;

		ima_filter_rule_init(nentry->lsm[i].type, Audit_equal,
				     nentry->lsm[i].args_p,
				     &nentry->lsm[i].rule,
				     gfp);
		if (!nentry->lsm[i].rule)
			pr_warn("rule for LSM \'%s\' is undefined\n",
				nentry->lsm[i].args_p);
	}
	return nentry;
}

static int ima_lsm_update_rule(struct ima_rule_entry *entry)
{
	int i;
	struct ima_rule_entry *nentry;

	nentry = ima_lsm_copy_rule(entry, GFP_KERNEL);
	if (!nentry)
		return -ENOMEM;

	list_replace_rcu(&entry->list, &nentry->list);
	synchronize_rcu();
	/*
	 * ima_lsm_copy_rule() shallow copied all references, except for the
	 * LSM references, from entry to nentry so we only want to free the LSM
	 * references and the entry itself. All other memory references will now
	 * be owned by nentry.
	 */
	for (i = 0; i < MAX_LSM_RULES; i++)
		ima_filter_rule_free(entry->lsm[i].rule);
	kfree(entry);

	return 0;
}

static bool ima_rule_contains_lsm_cond(struct ima_rule_entry *entry)
{
	int i;

	for (i = 0; i < MAX_LSM_RULES; i++)
		if (entry->lsm[i].args_p)
			return true;

	return false;
}

/*
 * The LSM policy can be reloaded, leaving the IMA LSM based rules referring
 * to the old, stale LSM policy.  Update the IMA LSM based rules to reflect
 * the reloaded LSM policy.
 */
static void ima_lsm_update_rules(void)
{
	struct ima_rule_entry *entry, *e;
	int result;

	list_for_each_entry_safe(entry, e, &ima_policy_rules, list) {
		if (!ima_rule_contains_lsm_cond(entry))
			continue;

		result = ima_lsm_update_rule(entry);
		if (result) {
			pr_err("lsm rule update error %d\n", result);
			return;
		}
	}
}

int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
			  void *lsm_data)
{
	if (event != LSM_POLICY_CHANGE)
		return NOTIFY_DONE;

	ima_lsm_update_rules();
	return NOTIFY_OK;
}

/**
 * ima_match_rule_data - determine whether func_data matches the policy rule
 * @rule: a pointer to a rule
 * @func_data: data to match against the measure rule data
 * @cred: a pointer to a credentials structure for user validation
 *
 * Returns true if func_data matches one in the rule, false otherwise.
 */
static bool ima_match_rule_data(struct ima_rule_entry *rule,
				const char *func_data,
				const struct cred *cred)
{
	const struct ima_rule_opt_list *opt_list = NULL;
	bool matched = false;
	size_t i;

	if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
		return false;

	switch (rule->func) {
	case KEY_CHECK:
		if (!rule->keyrings)
			return true;

		opt_list = rule->keyrings;
		break;
	case CRITICAL_DATA:
		if (!rule->label)
			return true;

		opt_list = rule->label;
		break;
	default:
		return false;
	}

	if (!func_data)
		return false;

	for (i = 0; i < opt_list->count; i++) {
		if (!strcmp(opt_list->items[i], func_data)) {
			matched = true;
			break;
		}
	}

	return matched;
}

/**
 * ima_match_rules - determine whether an inode matches the policy rule.
 * @rule: a pointer to a rule
 * @idmap: idmap of the mount the inode was found from
 * @inode: a pointer to an inode
 * @cred: a pointer to a credentials structure for user validation
 * @prop: LSM properties of the task to be validated
 * @func: LIM hook identifier
 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
 * @func_data: func specific data, may be NULL
 *
 * Returns true on rule match, false on failure.
 */
static bool ima_match_rules(struct ima_rule_entry *rule,
			    struct mnt_idmap *idmap,
			    struct inode *inode, const struct cred *cred,
			    struct lsm_prop *prop, enum ima_hooks func, int mask,
			    const char *func_data)
{
	int i;
	bool result = false;
	struct ima_rule_entry *lsm_rule = rule;
	bool rule_reinitialized = false;

	if ((rule->flags & IMA_FUNC) &&
	    (rule->func != func && func != POST_SETATTR))
		return false;

	switch (func) {
	case KEY_CHECK:
	case CRITICAL_DATA:
		return ((rule->func == func) &&
			ima_match_rule_data(rule, func_data, cred));
	default:
		break;
	}

	if ((rule->flags & IMA_MASK) &&
	    (rule->mask != mask && func != POST_SETATTR))
		return false;
	if ((rule->flags & IMA_INMASK) &&
	    (!(rule->mask & mask) && func != POST_SETATTR))
		return false;
	if ((rule->flags & IMA_FSMAGIC)
	    && rule->fsmagic != inode->i_sb->s_magic)
		return false;
	if ((rule->flags & IMA_FSNAME)
	    && strcmp(rule->fsname, inode->i_sb->s_type->name))
		return false;
	if ((rule->flags & IMA_FSUUID) &&
	    !uuid_equal(&rule->fsuuid, &inode->i_sb->s_uuid))
		return false;
	if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
		return false;
	if (rule->flags & IMA_EUID) {
		if (has_capability_noaudit(current, CAP_SETUID)) {
			if (!rule->uid_op(cred->euid, rule->uid)
			    && !rule->uid_op(cred->suid, rule->uid)
			    && !rule->uid_op(cred->uid, rule->uid))
				return false;
		} else if (!rule->uid_op(cred->euid, rule->uid))
			return false;
	}
	if ((rule->flags & IMA_GID) && !rule->gid_op(cred->gid, rule->gid))
		return false;
	if (rule->flags & IMA_EGID) {
		if (has_capability_noaudit(current, CAP_SETGID)) {
			if (!rule->gid_op(cred->egid, rule->gid)
			    && !rule->gid_op(cred->sgid, rule->gid)
			    && !rule->gid_op(cred->gid, rule->gid))
				return false;
		} else if (!rule->gid_op(cred->egid, rule->gid))
			return false;
	}
	if ((rule->flags & IMA_FOWNER) &&
	    !rule->fowner_op(i_uid_into_vfsuid(idmap, inode),
			     rule->fowner))
		return false;
	if ((rule->flags & IMA_FGROUP) &&
	    !rule->fgroup_op(i_gid_into_vfsgid(idmap, inode),
			     rule->fgroup))
		return false;
	for (i = 0; i < MAX_LSM_RULES; i++) {
		int rc = 0;
		struct lsm_prop inode_prop = { };

		if (!lsm_rule->lsm[i].rule) {
			if (!lsm_rule->lsm[i].args_p)
				continue;
			else
				return false;
		}

retry:
		switch (i) {
		case LSM_OBJ_USER:
		case LSM_OBJ_ROLE:
		case LSM_OBJ_TYPE:
			security_inode_getlsmprop(inode, &inode_prop);
			rc = ima_filter_rule_match(&inode_prop,
						   lsm_rule->lsm[i].type,
						   Audit_equal,
						   lsm_rule->lsm[i].rule);
			break;
		case LSM_SUBJ_USER:
		case LSM_SUBJ_ROLE:
		case LSM_SUBJ_TYPE:
			rc = ima_filter_rule_match(prop, lsm_rule->lsm[i].type,
						   Audit_equal,
						   lsm_rule->lsm[i].rule);
			break;
		default:
			break;
		}

		if (rc == -ESTALE && !rule_reinitialized) {
			lsm_rule = ima_lsm_copy_rule(rule, GFP_ATOMIC);
			if (lsm_rule) {
				rule_reinitialized = true;
				goto retry;
			}
		}
		if (!rc) {
			result = false;
			goto out;
		}
	}
	result = true;

out:
	if (rule_reinitialized) {
		for (i = 0; i < MAX_LSM_RULES; i++)
			ima_filter_rule_free(lsm_rule->lsm[i].rule);
		kfree(lsm_rule);
	}
	return result;
}

/*
 * In addition to knowing that we need to appraise the file in general,
 * we need to differentiate between calling hooks, for hook specific rules.
 */
static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
{
	if (!(rule->flags & IMA_FUNC))
		return IMA_FILE_APPRAISE;

	switch (func) {
	case MMAP_CHECK:
	case MMAP_CHECK_REQPROT:
		return IMA_MMAP_APPRAISE;
	case BPRM_CHECK:
		return IMA_BPRM_APPRAISE;
	case CREDS_CHECK:
		return IMA_CREDS_APPRAISE;
	case FILE_CHECK:
	case POST_SETATTR:
		return IMA_FILE_APPRAISE;
	case MODULE_CHECK ... MAX_CHECK - 1:
	default:
		return IMA_READ_APPRAISE;
	}
}

/**
 * ima_match_policy - decision based on LSM and other conditions
 * @idmap: idmap of the mount the inode was found from
 * @inode: pointer to an inode for which the policy decision is being made
 * @cred: pointer to a credentials structure for which the policy decision is
 *        being made
 * @prop: LSM properties of the task to be validated
 * @func: IMA hook identifier
 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
 * @flags: IMA actions to consider (e.g. IMA_MEASURE | IMA_APPRAISE)
 * @pcr: set the pcr to extend
 * @template_desc: the template that should be used for this rule
 * @func_data: func specific data, may be NULL
 * @allowed_algos: allowlist of hash algorithms for the IMA xattr
 *
 * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
 * conditions.
 *
 * Since the IMA policy may be updated multiple times we need to lock the
 * list when walking it.  Reads are many orders of magnitude more numerous
 * than writes so ima_match_policy() is classical RCU candidate.
 */
int ima_match_policy(struct mnt_idmap *idmap, struct inode *inode,
		     const struct cred *cred, struct lsm_prop *prop,
		     enum ima_hooks func, int mask, int flags, int *pcr,
		     struct ima_template_desc **template_desc,
		     const char *func_data, unsigned int *allowed_algos)
{
	struct ima_rule_entry *entry;
	int action = 0, actmask = flags | (flags << 1);
	struct list_head *ima_rules_tmp;

	if (template_desc && !*template_desc)
		*template_desc = ima_template_desc_current();

	rcu_read_lock();
	ima_rules_tmp = rcu_dereference(ima_rules);
	list_for_each_entry_rcu(entry, ima_rules_tmp, list) {

		if (!(entry->action & actmask))
			continue;

		if (!ima_match_rules(entry, idmap, inode, cred, prop,
				     func, mask, func_data))
			continue;

		action |= entry->flags & IMA_NONACTION_FLAGS;

		action |= entry->action & IMA_DO_MASK;
		if (entry->action & IMA_APPRAISE) {
			action |= get_subaction(entry, func);
			action &= ~IMA_HASH;
			if (ima_fail_unverifiable_sigs)
				action |= IMA_FAIL_UNVERIFIABLE_SIGS;

			if (allowed_algos &&
			    entry->flags & IMA_VALIDATE_ALGOS)
				*allowed_algos = entry->allowed_algos;
		}

		if (entry->action & IMA_DO_MASK)
			actmask &= ~(entry->action | entry->action << 1);
		else
			actmask &= ~(entry->action | entry->action >> 1);

		if ((pcr) && (entry->flags & IMA_PCR))
			*pcr = entry->pcr;

		if (template_desc && entry->template)
			*template_desc = entry->template;

		if (!actmask)
			break;
	}
	rcu_read_unlock();

	return action;
}

/**
 * ima_update_policy_flags() - Update global IMA variables
 *
 * Update ima_policy_flag and ima_setxattr_allowed_hash_algorithms
 * based on the currently loaded policy.
 *
 * With ima_policy_flag, the decision to short circuit out of a function
 * or not call the function in the first place can be made earlier.
 *
 * With ima_setxattr_allowed_hash_algorithms, the policy can restrict the
 * set of hash algorithms accepted when updating the security.ima xattr of
 * a file.
 *
 * Context: called after a policy update and at system initialization.
 */
void ima_update_policy_flags(void)
{
	struct ima_rule_entry *entry;
	int new_policy_flag = 0;
	struct list_head *ima_rules_tmp;

	rcu_read_lock();
	ima_rules_tmp = rcu_dereference(ima_rules);
	list_for_each_entry_rcu(entry, ima_rules_tmp, list) {
		/*
		 * SETXATTR_CHECK rules do not implement a full policy check
		 * because rule checking would probably have an important
		 * performance impact on setxattr(). As a consequence, only one
		 * SETXATTR_CHECK can be active at a given time.
		 * Because we want to preserve that property, we set out to use
		 * atomic_cmpxchg. Either:
		 * - the atomic was non-zero: a setxattr hash policy is
		 *   already enforced, we do nothing
		 * - the atomic was zero: no setxattr policy was set, enable
		 *   the setxattr hash policy
		 */
		if (entry->func == SETXATTR_CHECK) {
			atomic_cmpxchg(&ima_setxattr_allowed_hash_algorithms,
				       0, entry->allowed_algos);
			/* SETXATTR_CHECK doesn't impact ima_policy_flag */
			continue;
		}

		if (entry->action & IMA_DO_MASK)
			new_policy_flag |= entry->action;
	}
	rcu_read_unlock();

	ima_appraise |= (build_ima_appraise | temp_ima_appraise);
	if (!ima_appraise)
		new_policy_flag &= ~IMA_APPRAISE;

	ima_policy_flag = new_policy_flag;
}

static int ima_appraise_flag(enum ima_hooks func)
{
	if (func == MODULE_CHECK)
		return IMA_APPRAISE_MODULES;
	else if (func == FIRMWARE_CHECK)
		return IMA_APPRAISE_FIRMWARE;
	else if (func == POLICY_CHECK)
		return IMA_APPRAISE_POLICY;
	else if (func == KEXEC_KERNEL_CHECK)
		return IMA_APPRAISE_KEXEC;
	return 0;
}

static void add_rules(struct ima_rule_entry *entries, int count,
		      enum policy_rule_list policy_rule)
{
	int i = 0;

	for (i = 0; i < count; i++) {
		struct ima_rule_entry *entry;

		if (policy_rule & IMA_DEFAULT_POLICY)
			list_add_tail(&entries[i].list, &ima_default_rules);

		if (policy_rule & IMA_CUSTOM_POLICY) {
			entry = kmemdup(&entries[i], sizeof(*entry),
					GFP_KERNEL);
			if (!entry)
				continue;

			list_add_tail(&entry->list, &ima_policy_rules);
		}
		if (entries[i].action == APPRAISE) {
			if (entries != build_appraise_rules)
				temp_ima_appraise |=
					ima_appraise_flag(entries[i].func);
			else
				build_ima_appraise |=
					ima_appraise_flag(entries[i].func);
		}
	}
}

static int ima_parse_rule(char *rule, struct ima_rule_entry *entry);

static int __init ima_init_arch_policy(void)
{
	const char * const *arch_rules;
	const char * const *rules;
	int arch_entries = 0;
	int i = 0;

	arch_rules = arch_get_ima_policy();
	if (!arch_rules)
		return arch_entries;

	/* Get number of rules */
	for (rules = arch_rules; *rules != NULL; rules++)
		arch_entries++;

	arch_policy_entry = kcalloc(arch_entries + 1,
				    sizeof(*arch_policy_entry), GFP_KERNEL);
	if (!arch_policy_entry)
		return 0;

	/* Convert each policy string rules to struct ima_rule_entry format */
	for (rules = arch_rules, i = 0; *rules != NULL; rules++) {
		char rule[255];
		int result;

		result = strscpy(rule, *rules, sizeof(rule));

		INIT_LIST_HEAD(&arch_policy_entry[i].list);
		result = ima_parse_rule(rule, &arch_policy_entry[i]);
		if (result) {
			pr_warn("Skipping unknown architecture policy rule: %s\n",
				rule);
			memset(&arch_policy_entry[i], 0,
			       sizeof(*arch_policy_entry));
			continue;
		}
		i++;
	}
	return i;
}

/**
 * ima_init_policy - initialize the default measure rules.
 *
 * ima_rules points to either the ima_default_rules or the new ima_policy_rules.
 */
void __init ima_init_policy(void)
{
	int build_appraise_entries, arch_entries;

	/* if !ima_policy, we load NO default rules */
	if (ima_policy)
		add_rules(dont_measure_rules, ARRAY_SIZE(dont_measure_rules),
			  IMA_DEFAULT_POLICY);

	switch (ima_policy) {
	case ORIGINAL_TCB:
		add_rules(original_measurement_rules,
			  ARRAY_SIZE(original_measurement_rules),
			  IMA_DEFAULT_POLICY);
		break;
	case DEFAULT_TCB:
		add_rules(default_measurement_rules,
			  ARRAY_SIZE(default_measurement_rules),
			  IMA_DEFAULT_POLICY);
		break;
	default:
		break;
	}

	/*
	 * Based on runtime secure boot flags, insert arch specific measurement
	 * and appraise rules requiring file signatures for both the initial
	 * and custom policies, prior to other appraise rules.
	 * (Highest priority)
	 */
	arch_entries = ima_init_arch_policy();
	if (!arch_entries)
		pr_info("No architecture policies found\n");
	else
		add_rules(arch_policy_entry, arch_entries,
			  IMA_DEFAULT_POLICY | IMA_CUSTOM_POLICY);

	/*
	 * Insert the builtin "secure_boot" policy rules requiring file
	 * signatures, prior to other appraise rules.
	 */
	if (ima_use_secure_boot)
		add_rules(secure_boot_rules, ARRAY_SIZE(secure_boot_rules),
			  IMA_DEFAULT_POLICY);

	/*
	 * Insert the build time appraise rules requiring file signatures
	 * for both the initial and custom policies, prior to other appraise
	 * rules. As the secure boot rules includes all of the build time
	 * rules, include either one or the other set of rules, but not both.
	 */
	build_appraise_entries = ARRAY_SIZE(build_appraise_rules);
	if (build_appraise_entries) {
		if (ima_use_secure_boot)
			add_rules(build_appraise_rules, build_appraise_entries,
				  IMA_CUSTOM_POLICY);
		else