linux-stable-mirror/security/integrity/ima/ima_fs.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Kylene Hall <kjhall@us.ibm.com>
 * Reiner Sailer <sailer@us.ibm.com>
 * Mimi Zohar <zohar@us.ibm.com>
 *
 * File: ima_fs.c
 *	implemenents security file system for reporting
 *	current measurement list and IMA statistics
 */

#include <linux/fcntl.h>
#include <linux/kernel_read_file.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/parser.h>
#include <linux/vmalloc.h>

#include "ima.h"

/*
 * Requests:
 * 'A\n': stage the entire measurements list
 * 'D\n': delete all staged measurements
 * '[1, ULONG_MAX]\n' delete N measurements records
 */
#define STAGED_REQ_LENGTH 21

static DEFINE_MUTEX(ima_write_mutex);
static DEFINE_MUTEX(ima_measure_mutex);
static long ima_measure_users;
static struct task_struct *measure_writer;
static long measure_writer_extra_writes;

bool ima_canonical_fmt;
static int __init default_canonical_fmt_setup(char *str)
{
#ifdef __BIG_ENDIAN
	ima_canonical_fmt = true;
#endif
	return 1;
}
__setup("ima_canonical_fmt", default_canonical_fmt_setup);

static int valid_policy = 1;

static ssize_t ima_show_counter(char __user *buf, size_t count, loff_t *ppos,
				atomic_long_t *val)
{
	char tmpbuf[32];	/* greater than largest 'long' string value */
	ssize_t len;

	len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
	return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
}

static ssize_t ima_show_num_violations(struct file *filp, char __user *buf,
				       size_t count, loff_t *ppos)
{
	return ima_show_counter(buf, count, ppos, &ima_num_violations);
}

static const struct file_operations ima_num_violations_ops = {
	.read = ima_show_num_violations,
	.llseek = generic_file_llseek,
};

static ssize_t ima_show_measurements_count(struct file *filp,
					   char __user *buf,
					   size_t count, loff_t *ppos)
{
	return ima_show_counter(buf, count, ppos, &ima_num_records[BINARY]);
}

static const struct file_operations ima_measurements_count_ops = {
	.read = ima_show_measurements_count,
	.llseek = generic_file_llseek,
};

/* returns pointer to hlist_node */
static void *_ima_measurements_start(struct seq_file *m, loff_t *pos,
				     struct list_head *head)
{
	loff_t l = *pos;
	struct ima_queue_entry *qe;

	/* we need a lock since pos could point beyond last element */
	rcu_read_lock();
	list_for_each_entry_rcu(qe, head, later) {
		if (!l--) {
			rcu_read_unlock();
			return qe;
		}
	}
	rcu_read_unlock();
	return NULL;
}

static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
{
	return _ima_measurements_start(m, pos, &ima_measurements);
}

static void *ima_measurements_staged_start(struct seq_file *m, loff_t *pos)
{
	return _ima_measurements_start(m, pos, &ima_measurements_staged);
}

static void *_ima_measurements_next(struct seq_file *m, void *v, loff_t *pos,
				    struct list_head *head)
{
	struct ima_queue_entry *qe = v;

	/* lock protects when reading beyond last element
	 * against concurrent list-extension
	 */
	rcu_read_lock();
	qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
	rcu_read_unlock();
	(*pos)++;

	return (&qe->later == head) ? NULL : qe;
}

static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
{
	return _ima_measurements_next(m, v, pos, &ima_measurements);
}

static void *ima_measurements_staged_next(struct seq_file *m, void *v,
					  loff_t *pos)
{
	return _ima_measurements_next(m, v, pos, &ima_measurements_staged);
}

static void ima_measurements_stop(struct seq_file *m, void *v)
{
}

void ima_putc(struct seq_file *m, void *data, int datalen)
{
	while (datalen--)
		seq_putc(m, *(char *)data++);
}

/* print format:
 *       32bit-le=pcr#
 *       char[n]=template digest
 *       32bit-le=template name size
 *       char[n]=template name
 *       [eventdata length]
 *       eventdata[n]=template specific data
 */
int ima_measurements_show(struct seq_file *m, void *v)
{
	/* the list never shrinks, so we don't need a lock here */
	struct ima_queue_entry *qe = v;
	struct ima_template_entry *e;
	char *template_name;
	u32 pcr, namelen, template_data_len; /* temporary fields */
	bool is_ima_template = false;
	int i, algo_idx;

	algo_idx = ima_sha1_idx;

	if (m->file != NULL)
		algo_idx = (unsigned long)file_inode(m->file)->i_private;

	/* get entry */
	e = qe->entry;
	if (e == NULL)
		return -1;

	template_name = (e->template_desc->name[0] != '\0') ?
	    e->template_desc->name : e->template_desc->fmt;

	/*
	 * 1st: PCRIndex
	 * PCR used defaults to the same (config option) in
	 * little-endian format, unless set in policy
	 */
	pcr = !ima_canonical_fmt ? e->pcr : (__force u32)cpu_to_le32(e->pcr);
	ima_putc(m, &pcr, sizeof(e->pcr));

	/* 2nd: template digest */
	ima_putc(m, e->digests[algo_idx].digest,
		 ima_algo_array[algo_idx].digest_size);

	/* 3rd: template name size */
	namelen = !ima_canonical_fmt ? strlen(template_name) :
		(__force u32)cpu_to_le32(strlen(template_name));
	ima_putc(m, &namelen, sizeof(namelen));

	/* 4th:  template name */
	ima_putc(m, template_name, strlen(template_name));

	/* 5th:  template length (except for 'ima' template) */
	if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
		is_ima_template = true;

	if (!is_ima_template) {
		template_data_len = !ima_canonical_fmt ? e->template_data_len :
			(__force u32)cpu_to_le32(e->template_data_len);
		ima_putc(m, &template_data_len, sizeof(e->template_data_len));
	}

	/* 6th:  template specific data */
	for (i = 0; i < e->template_desc->num_fields; i++) {
		enum ima_show_type show = IMA_SHOW_BINARY;
		const struct ima_template_field *field =
			e->template_desc->fields[i];

		if (is_ima_template && strcmp(field->field_id, "d") == 0)
			show = IMA_SHOW_BINARY_NO_FIELD_LEN;
		if (is_ima_template && strcmp(field->field_id, "n") == 0)
			show = IMA_SHOW_BINARY_OLD_STRING_FMT;
		field->field_show(m, show, &e->template_data[i]);
	}
	return 0;
}

static const struct seq_operations ima_measurments_seqops = {
	.start = ima_measurements_start,
	.next = ima_measurements_next,
	.stop = ima_measurements_stop,
	.show = ima_measurements_show
};

static const struct seq_operations ima_measurments_staged_seqops = {
	.start = ima_measurements_staged_start,
	.next = ima_measurements_staged_next,
	.stop = ima_measurements_stop,
	.show = ima_measurements_show
};

static int ima_measure_lock(bool write)
{
	mutex_lock(&ima_measure_mutex);
	/* Overflow check. */
	if (!write && ima_measure_users == LONG_MAX) {
		mutex_unlock(&ima_measure_mutex);
		return -ENFILE;
	}

	/* Same writer can do additional writes or read/writes. */
	if (write && current == measure_writer) {
		measure_writer_extra_writes++;
		mutex_unlock(&ima_measure_mutex);
		return 0;
	}

	/*
	 * ima_measure_users: > 0 open readers
	 * ima_measure_users: == -1 open writer
	 */
	if ((write && ima_measure_users != 0) ||
	    (!write && ima_measure_users < 0)) {
		mutex_unlock(&ima_measure_mutex);
		return -EBUSY;
	}

	if (write) {
		ima_measure_users--;
		/* Pointer valid, no reuse while the file descriptor is open. */
		measure_writer = current;
	} else {
		ima_measure_users++;
	}
	mutex_unlock(&ima_measure_mutex);
	return 0;
}

static void ima_measure_unlock(bool write)
{
	mutex_lock(&ima_measure_mutex);
	/* Decrement additional writes or read/writes. */
	if (write && current == measure_writer &&
	    measure_writer_extra_writes != 0) {
		measure_writer_extra_writes--;
		mutex_unlock(&ima_measure_mutex);
		return;
	}
	if (write) {
		ima_measure_users++;
		measure_writer = NULL;
	} else {
		ima_measure_users--;
	}
	mutex_unlock(&ima_measure_mutex);
}

static int _ima_measurements_open(struct inode *inode, struct file *file,
				  const struct seq_operations *seq_ops)
{
	bool write = (file->f_mode & FMODE_WRITE);
	int ret;

	if (write && !capable(CAP_SYS_ADMIN))
		return -EPERM;

	ret = ima_measure_lock(write);
	if (ret < 0)
		return ret;

	ret = seq_open(file, seq_ops);
	if (ret < 0)
		ima_measure_unlock(write);

	return ret;
}

static int ima_measurements_open(struct inode *inode, struct file *file)
{
	return _ima_measurements_open(inode, file, &ima_measurments_seqops);
}

static int ima_measurements_release(struct inode *inode, struct file *file)
{
	bool write = (file->f_mode & FMODE_WRITE);
	int ret;

	/* seq_release() always returns zero. */
	ret = seq_release(inode, file);

	ima_measure_unlock(write);

	return ret;
}

static int ima_measurements_staged_open(struct inode *inode, struct file *file)
{
	return _ima_measurements_open(inode, file,
				      &ima_measurments_staged_seqops);
}

static ssize_t _ima_measurements_write(struct file *file,
				       const char __user *buf, size_t datalen,
				       loff_t *ppos, bool staged_interface)
{
	char req[STAGED_REQ_LENGTH];
	unsigned long req_value;
	int ret;

	if (datalen < 2 || datalen > STAGED_REQ_LENGTH)
		return -EINVAL;

	if (copy_from_user(req, buf, datalen) != 0)
		return -EFAULT;

	if (req[datalen - 1] != '\n')
		return -EINVAL;

	req[datalen - 1] = '\0';

	switch (req[0]) {
	case 'A':
		if (datalen != 2 || !staged_interface)
			return -EINVAL;

		ret = ima_queue_stage();
		break;
	case 'D':
		if (datalen != 2 || !staged_interface)
			return -EINVAL;

		ret = ima_queue_staged_delete_all();
		break;
	default:
		if (staged_interface)
			return -EINVAL;

		if (ima_flush_htable) {
			pr_debug("Deleting staged N measurements not supported when flushing the hash table is requested\n");
			return -EINVAL;
		}

		ret = kstrtoul(req, 10, &req_value);
		if (ret < 0)
			return ret;

		if (req_value == 0) {
			pr_debug("Must delete at least one entry\n");
			return -EINVAL;
		}

		ret = ima_queue_delete_partial(req_value);
	}

	if (ret < 0)
		return ret;

	return datalen;
}

static ssize_t ima_measurements_write(struct file *file, const char __user *buf,
				      size_t datalen, loff_t *ppos)
{
	return _ima_measurements_write(file, buf, datalen, ppos, false);
}

static ssize_t ima_measurements_staged_write(struct file *file,
					     const char __user *buf,
					     size_t datalen, loff_t *ppos)
{
	return _ima_measurements_write(file, buf, datalen, ppos, true);
}

static const struct file_operations ima_measurements_ops = {
	.open = ima_measurements_open,
	.read = seq_read,
	.write = ima_measurements_write,
	.llseek = seq_lseek,
	.release = ima_measurements_release,
};

static const struct file_operations ima_measurements_staged_ops = {
	.open = ima_measurements_staged_open,
	.read = seq_read,
	.write = ima_measurements_staged_write,
	.llseek = seq_lseek,
	.release = ima_measurements_release,
};

void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
{
	u32 i;

	for (i = 0; i < size; i++)
		seq_printf(m, "%02x", *(digest + i));
}

/* print in ascii */
static int ima_ascii_measurements_show(struct seq_file *m, void *v)
{
	/* the list never shrinks, so we don't need a lock here */
	struct ima_queue_entry *qe = v;
	struct ima_template_entry *e;
	char *template_name;
	int i, algo_idx;

	algo_idx = ima_sha1_idx;

	if (m->file != NULL)
		algo_idx = (unsigned long)file_inode(m->file)->i_private;

	/* get entry */
	e = qe->entry;
	if (e == NULL)
		return -1;

	template_name = (e->template_desc->name[0] != '\0') ?
	    e->template_desc->name : e->template_desc->fmt;

	/* 1st: PCR used (config option) */
	seq_printf(m, "%2d ", e->pcr);

	/* 2nd: template hash */
	ima_print_digest(m, e->digests[algo_idx].digest,
			 ima_algo_array[algo_idx].digest_size);

	/* 3th:  template name */
	seq_printf(m, " %s", template_name);

	/* 4th:  template specific data */
	for (i = 0; i < e->template_desc->num_fields; i++) {
		seq_puts(m, " ");
		if (e->template_data[i].len == 0)
			continue;

		e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
							&e->template_data[i]);
	}
	seq_puts(m, "\n");
	return 0;
}

static const struct seq_operations ima_ascii_measurements_seqops = {
	.start = ima_measurements_start,
	.next = ima_measurements_next,
	.stop = ima_measurements_stop,
	.show = ima_ascii_measurements_show
};

static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
{
	return _ima_measurements_open(inode, file,
				      &ima_ascii_measurements_seqops);
}

static const struct file_operations ima_ascii_measurements_ops = {
	.open = ima_ascii_measurements_open,
	.read = seq_read,
	.write = ima_measurements_write,
	.llseek = seq_lseek,
	.release = ima_measurements_release,
};

static const struct seq_operations ima_ascii_measurements_staged_seqops = {
	.start = ima_measurements_staged_start,
	.next = ima_measurements_staged_next,
	.stop = ima_measurements_stop,
	.show = ima_ascii_measurements_show
};

static int ima_ascii_measurements_staged_open(struct inode *inode,
					      struct file *file)
{
	return _ima_measurements_open(inode, file,
				      &ima_ascii_measurements_staged_seqops);
}

static const struct file_operations ima_ascii_measurements_staged_ops = {
	.open = ima_ascii_measurements_staged_open,
	.read = seq_read,
	.write = ima_measurements_staged_write,
	.llseek = seq_lseek,
	.release = ima_measurements_release,
};

static ssize_t ima_read_policy(char *path)
{
	void *data = NULL;
	char *datap;
	size_t size;
	int rc, pathlen = strlen(path);

	char *p;

	/* remove \n */
	datap = path;
	strsep(&datap, "\n");

	rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
					READING_POLICY);
	if (rc < 0) {
		pr_err("Unable to open file: %s (%d)", path, rc);
		return rc;
	}
	size = rc;
	rc = 0;

	datap = data;
	while (size > 0 && (p = strsep(&datap, "\n"))) {
		pr_debug("rule: %s\n", p);
		rc = ima_parse_add_rule(p);
		if (rc < 0)
			break;
		size -= rc;
	}

	vfree(data);
	if (rc < 0)
		return rc;
	else if (size)
		return -EINVAL;
	else
		return pathlen;
}

static ssize_t ima_write_policy(struct file *file, const char __user *buf,
				size_t datalen, loff_t *ppos)
{
	char *data;
	ssize_t result;

	if (datalen >= PAGE_SIZE)
		datalen = PAGE_SIZE - 1;

	/* No partial writes. */
	result = -EINVAL;
	if (*ppos != 0)
		goto out;

	data = memdup_user_nul(buf, datalen);
	if (IS_ERR(data)) {
		result = PTR_ERR(data);
		goto out;
	}

	result = mutex_lock_interruptible(&ima_write_mutex);
	if (result < 0)
		goto out_free;

	if (data[0] == '/') {
		result = ima_read_policy(data);
	} else if (ima_appraise & IMA_APPRAISE_POLICY) {
		pr_err("signed policy file (specified as an absolute pathname) required\n");
		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
				    "policy_update", "signed policy required",
				    1, 0);
		result = -EACCES;
	} else {
		result = ima_parse_add_rule(data);
	}
	mutex_unlock(&ima_write_mutex);
out_free:
	kfree(data);
out:
	if (result < 0)
		valid_policy = 0;

	return result;
}

static struct dentry *ima_dir;
static struct dentry *ima_symlink;

enum ima_fs_flags {
	IMA_FS_BUSY,
};

static unsigned long ima_fs_flags;

#ifdef	CONFIG_IMA_READ_POLICY
static const struct seq_operations ima_policy_seqops = {
		.start = ima_policy_start,
		.next = ima_policy_next,
		.stop = ima_policy_stop,
		.show = ima_policy_show,
};
#endif

static int __init create_securityfs_measurement_lists(bool staging)
{
	const struct file_operations *ascii_ops = &ima_ascii_measurements_ops;
	const struct file_operations *binary_ops = &ima_measurements_ops;
	umode_t permissions = (S_IRUSR | S_IRGRP | S_IWUSR | S_IWGRP);
	const char *file_suffix = "";
	int count = NR_BANKS(ima_tpm_chip);

	if (staging) {
		ascii_ops = &ima_ascii_measurements_staged_ops;
		binary_ops = &ima_measurements_staged_ops;
		file_suffix = "_staged";
	}

	if (ima_sha1_idx >= NR_BANKS(ima_tpm_chip))
		count++;

	for (int i = 0; i < count; i++) {
		u16 algo = ima_algo_array[i].algo;
		char file_name[NAME_MAX + 1];
		struct dentry *dentry;

		if (algo == HASH_ALGO__LAST)
			snprintf(file_name, sizeof(file_name),
				 "ascii_runtime_measurements_tpm_alg_%x%s",
				 ima_tpm_chip->allocated_banks[i].alg_id,
				 file_suffix);
		else
			snprintf(file_name, sizeof(file_name),
				 "ascii_runtime_measurements_%s%s",
				 hash_algo_name[algo], file_suffix);
		dentry = securityfs_create_file(file_name, permissions,
						ima_dir, (void *)(uintptr_t)i,
						ascii_ops);
		if (IS_ERR(dentry))
			return PTR_ERR(dentry);

		if (algo == HASH_ALGO__LAST)
			snprintf(file_name, sizeof(file_name),
				 "binary_runtime_measurements_tpm_alg_%x%s",
				 ima_tpm_chip->allocated_banks[i].alg_id,
				 file_suffix);
		else
			snprintf(file_name, sizeof(file_name),
				 "binary_runtime_measurements_%s%s",
				 hash_algo_name[algo], file_suffix);

		dentry = securityfs_create_file(file_name, permissions,
						ima_dir, (void *)(uintptr_t)i,
						binary_ops);
		if (IS_ERR(dentry))
			return PTR_ERR(dentry);
	}

	return 0;
}

static int __init create_securityfs_staging_links(void)
{
	struct dentry *dentry;

	dentry = securityfs_create_symlink("binary_runtime_measurements_staged",
		ima_dir, "binary_runtime_measurements_sha1_staged", NULL);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	dentry = securityfs_create_symlink("ascii_runtime_measurements_staged",
		ima_dir, "ascii_runtime_measurements_sha1_staged", NULL);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	return 0;
}

/*
 * ima_open_policy: sequentialize access to the policy file
 */
static int ima_open_policy(struct inode *inode, struct file *filp)
{
	if (!(filp->f_flags & O_WRONLY)) {
#ifndef	CONFIG_IMA_READ_POLICY
		return -EACCES;
#else
		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
			return -EACCES;
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		return seq_open(filp, &ima_policy_seqops);
#endif
	}
	if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
		return -EBUSY;
	return 0;
}

/*
 * ima_release_policy - start using the new measure policy rules.
 *
 * Initially, ima_measure points to the default policy rules, now
 * point to the new policy rules, and remove the securityfs policy file,
 * assuming a valid policy.
 */
static int ima_release_policy(struct inode *inode, struct file *file)
{
	const char *cause = valid_policy ? "completed" : "failed";

	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
		return seq_release(inode, file);

	if (valid_policy && ima_check_policy() < 0) {
		cause = "failed";
		valid_policy = 0;
	}

	pr_info("policy update %s\n", cause);
	integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
			    "policy_update", cause, !valid_policy, 0);

	if (!valid_policy) {
		ima_delete_rules();
		valid_policy = 1;
		clear_bit(IMA_FS_BUSY, &ima_fs_flags);
		return 0;
	}

	ima_update_policy();
#if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
	securityfs_remove(file->f_path.dentry);
#elif defined(CONFIG_IMA_WRITE_POLICY)
	clear_bit(IMA_FS_BUSY, &ima_fs_flags);
#elif defined(CONFIG_IMA_READ_POLICY)
	inode->i_mode &= ~S_IWUSR;
#endif
	return 0;
}

static const struct file_operations ima_measure_policy_ops = {
	.open = ima_open_policy,
	.write = ima_write_policy,
	.read = seq_read,
	.release = ima_release_policy,
	.llseek = generic_file_llseek,
};

int __init ima_fs_init(void)
{
	struct dentry *dentry;
	int ret;

	ret = integrity_fs_init();
	if (ret < 0)
		return ret;

	ima_dir = securityfs_create_dir("ima", integrity_dir);
	if (IS_ERR(ima_dir)) {
		ret = PTR_ERR(ima_dir);
		goto out;
	}

	ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
						NULL);
	if (IS_ERR(ima_symlink)) {
		ret = PTR_ERR(ima_symlink);
		goto out;
	}

	ret = create_securityfs_measurement_lists(false);
	if (ret == 0 && IS_ENABLED(CONFIG_IMA_STAGING)) {
		ret = create_securityfs_measurement_lists(true);
		if (ret == 0)
			ret = create_securityfs_staging_links();
	}

	if (ret != 0)
		goto out;

	dentry = securityfs_create_symlink("binary_runtime_measurements", ima_dir,
				      "binary_runtime_measurements_sha1", NULL);
	if (IS_ERR(dentry)) {
		ret = PTR_ERR(dentry);
		goto out;
	}

	dentry = securityfs_create_symlink("ascii_runtime_measurements", ima_dir,
				      "ascii_runtime_measurements_sha1", NULL);
	if (IS_ERR(dentry)) {
		ret = PTR_ERR(dentry);
		goto out;
	}

	dentry = securityfs_create_file("runtime_measurements_count",
				   S_IRUSR | S_IRGRP, ima_dir, NULL,
				   &ima_measurements_count_ops);
	if (IS_ERR(dentry)) {
		ret = PTR_ERR(dentry);
		goto out;
	}

	dentry = securityfs_create_file("violations", S_IRUSR | S_IRGRP,
				   ima_dir, NULL, &ima_num_violations_ops);
	if (IS_ERR(dentry)) {
		ret = PTR_ERR(dentry);
		goto out;
	}

	dentry = securityfs_create_file("policy", POLICY_FILE_FLAGS,
					    ima_dir, NULL,
					    &ima_measure_policy_ops);
	if (IS_ERR(dentry)) {
		ret = PTR_ERR(dentry);
		goto out;
	}

	return 0;
out:
	securityfs_remove(ima_symlink);
	securityfs_remove(ima_dir);
	integrity_fs_fini();

	return ret;
}