blob: 60027c643ecdf79ba00ea664153f103b2960e54e [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-only
/*
* Integrity Measurement Architecture
*
* Copyright (C) 2005,2006,2007,2008 IBM Corporation
*
* Authors:
* Reiner Sailer <sailer@watson.ibm.com>
* Serge Hallyn <serue@us.ibm.com>
* Kylene Hall <kylene@us.ibm.com>
* Mimi Zohar <zohar@us.ibm.com>
*
* File: ima_main.c
* implements the IMA hooks: ima_bprm_check, ima_file_mmap,
* and ima_file_check.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/mount.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/ima.h>
#include <linux/iversion.h>
#include <linux/fs.h>
#include "ima.h"
#ifdef CONFIG_IMA_APPRAISE
int ima_appraise = IMA_APPRAISE_ENFORCE;
#else
int ima_appraise;
#endif
int ima_hash_algo = HASH_ALGO_SHA1;
static int hash_setup_done;
static struct notifier_block ima_lsm_policy_notifier = {
.notifier_call = ima_lsm_policy_change,
};
static int __init hash_setup(char *str)
{
struct ima_template_desc *template_desc = ima_template_desc_current();
int i;
if (hash_setup_done)
return 1;
if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
if (strncmp(str, "sha1", 4) == 0)
ima_hash_algo = HASH_ALGO_SHA1;
else if (strncmp(str, "md5", 3) == 0)
ima_hash_algo = HASH_ALGO_MD5;
else
return 1;
goto out;
}
i = match_string(hash_algo_name, HASH_ALGO__LAST, str);
if (i < 0)
return 1;
ima_hash_algo = i;
out:
hash_setup_done = 1;
return 1;
}
__setup("ima_hash=", hash_setup);
/* Prevent mmap'ing a file execute that is already mmap'ed write */
static int mmap_violation_check(enum ima_hooks func, struct file *file,
char **pathbuf, const char **pathname,
char *filename)
{
struct inode *inode;
int rc = 0;
if ((func == MMAP_CHECK) && mapping_writably_mapped(file->f_mapping)) {
rc = -ETXTBSY;
inode = file_inode(file);
if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */
*pathname = ima_d_path(&file->f_path, pathbuf,
filename);
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname,
"mmap_file", "mmapped_writers", rc, 0);
}
return rc;
}
/*
* ima_rdwr_violation_check
*
* Only invalidate the PCR for measured files:
* - Opening a file for write when already open for read,
* results in a time of measure, time of use (ToMToU) error.
* - Opening a file for read when already open for write,
* could result in a file measurement error.
*
*/
static void ima_rdwr_violation_check(struct file *file,
struct integrity_iint_cache *iint,
int must_measure,
char **pathbuf,
const char **pathname,
char *filename)
{
struct inode *inode = file_inode(file);
fmode_t mode = file->f_mode;
bool send_tomtou = false, send_writers = false;
if (mode & FMODE_WRITE) {
if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
if (!iint)
iint = integrity_iint_find(inode);
/* IMA_MEASURE is set from reader side */
if (iint && test_bit(IMA_MUST_MEASURE,
&iint->atomic_flags))
send_tomtou = true;
}
} else {
if (must_measure)
set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
if (inode_is_open_for_write(inode) && must_measure)
send_writers = true;
}
if (!send_tomtou && !send_writers)
return;
*pathname = ima_d_path(&file->f_path, pathbuf, filename);
if (send_tomtou)
ima_add_violation(file, *pathname, iint,
"invalid_pcr", "ToMToU");
if (send_writers)
ima_add_violation(file, *pathname, iint,
"invalid_pcr", "open_writers");
}
static void ima_check_last_writer(struct integrity_iint_cache *iint,
struct inode *inode, struct file *file)
{
fmode_t mode = file->f_mode;
bool update;
if (!(mode & FMODE_WRITE))
return;
mutex_lock(&iint->mutex);
if (atomic_read(&inode->i_writecount) == 1) {
update = test_and_clear_bit(IMA_UPDATE_XATTR,
&iint->atomic_flags);
if (!IS_I_VERSION(inode) ||
!inode_eq_iversion(inode, iint->version) ||
(iint->flags & IMA_NEW_FILE)) {
iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
iint->measured_pcrs = 0;
if (update)
ima_update_xattr(iint, file);
}
}
mutex_unlock(&iint->mutex);
}
/**
* ima_file_free - called on __fput()
* @file: pointer to file structure being freed
*
* Flag files that changed, based on i_version
*/
void ima_file_free(struct file *file)
{
struct inode *inode = file_inode(file);
struct integrity_iint_cache *iint;
if (!ima_policy_flag || !S_ISREG(inode->i_mode))
return;
iint = integrity_iint_find(inode);
if (!iint)
return;
ima_check_last_writer(iint, inode, file);
}
static int process_measurement(struct file *file, const struct cred *cred,
u32 secid, char *buf, loff_t size, int mask,
enum ima_hooks func)
{
struct inode *inode = file_inode(file);
struct integrity_iint_cache *iint = NULL;
struct ima_template_desc *template_desc = NULL;
char *pathbuf = NULL;
char filename[NAME_MAX];
const char *pathname = NULL;
int rc = 0, action, must_appraise = 0;
int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
struct evm_ima_xattr_data *xattr_value = NULL;
struct modsig *modsig = NULL;
int xattr_len = 0;
bool violation_check;
enum hash_algo hash_algo;
if (!ima_policy_flag || !S_ISREG(inode->i_mode))
return 0;
/* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
* bitmask based on the appraise/audit/measurement policy.
* Included is the appraise submask.
*/
action = ima_get_action(inode, cred, secid, mask, func, &pcr,
&template_desc);
violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
(ima_policy_flag & IMA_MEASURE));
if (!action && !violation_check)
return 0;
must_appraise = action & IMA_APPRAISE;
/* Is the appraise rule hook specific? */
if (action & IMA_FILE_APPRAISE)
func = FILE_CHECK;
inode_lock(inode);
if (action) {
iint = integrity_inode_get(inode);
if (!iint)
rc = -ENOMEM;
}
if (!rc && violation_check)
ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
&pathbuf, &pathname, filename);
inode_unlock(inode);
if (rc)
goto out;
if (!action)
goto out;
mutex_lock(&iint->mutex);
if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
/* reset appraisal flags if ima_inode_post_setattr was called */
iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
IMA_ACTION_FLAGS);
/*
* Re-evaulate the file if either the xattr has changed or the
* kernel has no way of detecting file change on the filesystem.
* (Limited to privileged mounted filesystems.)
*/
if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) ||
((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
!(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
!(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
iint->flags &= ~IMA_DONE_MASK;
iint->measured_pcrs = 0;
}
/* Determine if already appraised/measured based on bitmask
* (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
* IMA_AUDIT, IMA_AUDITED)
*/
iint->flags |= action;
action &= IMA_DO_MASK;
action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
/* If target pcr is already measured, unset IMA_MEASURE action */
if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
action ^= IMA_MEASURE;
/* HASH sets the digital signature and update flags, nothing else */
if ((action & IMA_HASH) &&
!(test_bit(IMA_DIGSIG, &iint->atomic_flags))) {
xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
if ((xattr_value && xattr_len > 2) &&
(xattr_value->type == EVM_IMA_XATTR_DIGSIG))
set_bit(IMA_DIGSIG, &iint->atomic_flags);
iint->flags |= IMA_HASHED;
action ^= IMA_HASH;
set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
}
/* Nothing to do, just return existing appraised status */
if (!action) {
if (must_appraise) {
rc = mmap_violation_check(func, file, &pathbuf,
&pathname, filename);
if (!rc)
rc = ima_get_cache_status(iint, func);
}
goto out_locked;
}
if ((action & IMA_APPRAISE_SUBMASK) ||
strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) {
/* read 'security.ima' */
xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
/*
* Read the appended modsig if allowed by the policy, and allow
* an additional measurement list entry, if needed, based on the
* template format and whether the file was already measured.
*/
if (iint->flags & IMA_MODSIG_ALLOWED) {
rc = ima_read_modsig(func, buf, size, &modsig);
if (!rc && ima_template_has_modsig(template_desc) &&
iint->flags & IMA_MEASURED)
action |= IMA_MEASURE;
}
}
hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig);
if (rc != 0 && rc != -EBADF && rc != -EINVAL)
goto out_locked;
if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
pathname = ima_d_path(&file->f_path, &pathbuf, filename);
if (action & IMA_MEASURE)
ima_store_measurement(iint, file, pathname,
xattr_value, xattr_len, modsig, pcr,
template_desc);
if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
inode_lock(inode);
rc = ima_appraise_measurement(func, iint, file, pathname,
xattr_value, xattr_len, modsig);
inode_unlock(inode);
if (!rc)
rc = mmap_violation_check(func, file, &pathbuf,
&pathname, filename);
}
if (action & IMA_AUDIT)
ima_audit_measurement(iint, pathname);
if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
rc = 0;
out_locked:
if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
!(iint->flags & IMA_NEW_FILE))
rc = -EACCES;
mutex_unlock(&iint->mutex);
kfree(xattr_value);
ima_free_modsig(modsig);
out:
if (pathbuf)
__putname(pathbuf);
if (must_appraise) {
if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
return -EACCES;
if (file->f_mode & FMODE_WRITE)
set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
}
return 0;
}
/**
* ima_file_mmap - based on policy, collect/store measurement.
* @file: pointer to the file to be measured (May be NULL)
* @prot: contains the protection that will be applied by the kernel.
*
* Measure files being mmapped executable based on the ima_must_measure()
* policy decision.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_file_mmap(struct file *file, unsigned long prot)
{
u32 secid;
if (file && (prot & PROT_EXEC)) {
security_task_getsecid(current, &secid);
return process_measurement(file, current_cred(), secid, NULL,
0, MAY_EXEC, MMAP_CHECK);
}
return 0;
}
/**
* ima_bprm_check - based on policy, collect/store measurement.
* @bprm: contains the linux_binprm structure
*
* The OS protects against an executable file, already open for write,
* from being executed in deny_write_access() and an executable file,
* already open for execute, from being modified in get_write_access().
* So we can be certain that what we verify and measure here is actually
* what is being executed.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_bprm_check(struct linux_binprm *bprm)
{
int ret;
u32 secid;
security_task_getsecid(current, &secid);
ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
MAY_EXEC, BPRM_CHECK);
if (ret)
return ret;
security_cred_getsecid(bprm->cred, &secid);
return process_measurement(bprm->file, bprm->cred, secid, NULL, 0,
MAY_EXEC, CREDS_CHECK);
}
/**
* ima_path_check - based on policy, collect/store measurement.
* @file: pointer to the file to be measured
* @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND
*
* Measure files based on the ima_must_measure() policy decision.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_file_check(struct file *file, int mask)
{
u32 secid;
security_task_getsecid(current, &secid);
return process_measurement(file, current_cred(), secid, NULL, 0,
mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
MAY_APPEND), FILE_CHECK);
}
EXPORT_SYMBOL_GPL(ima_file_check);
/**
* ima_post_create_tmpfile - mark newly created tmpfile as new
* @file : newly created tmpfile
*
* No measuring, appraising or auditing of newly created tmpfiles is needed.
* Skip calling process_measurement(), but indicate which newly, created
* tmpfiles are in policy.
*/
void ima_post_create_tmpfile(struct inode *inode)
{
struct integrity_iint_cache *iint;
int must_appraise;
must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
if (!must_appraise)
return;
/* Nothing to do if we can't allocate memory */
iint = integrity_inode_get(inode);
if (!iint)
return;
/* needed for writing the security xattrs */
set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
iint->ima_file_status = INTEGRITY_PASS;
}
/**
* ima_post_path_mknod - mark as a new inode
* @dentry: newly created dentry
*
* Mark files created via the mknodat syscall as new, so that the
* file data can be written later.
*/
void ima_post_path_mknod(struct dentry *dentry)
{
struct integrity_iint_cache *iint;
struct inode *inode = dentry->d_inode;
int must_appraise;
must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
if (!must_appraise)
return;
/* Nothing to do if we can't allocate memory */
iint = integrity_inode_get(inode);
if (!iint)
return;
/* needed for re-opening empty files */
iint->flags |= IMA_NEW_FILE;
}
/**
* ima_read_file - pre-measure/appraise hook decision based on policy
* @file: pointer to the file to be measured/appraised/audit
* @read_id: caller identifier
*
* Permit reading a file based on policy. The policy rules are written
* in terms of the policy identifier. Appraising the integrity of
* a file requires a file descriptor.
*
* For permission return 0, otherwise return -EACCES.
*/
int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
{
/*
* READING_FIRMWARE_PREALLOC_BUFFER
*
* Do devices using pre-allocated memory run the risk of the
* firmware being accessible to the device prior to the completion
* of IMA's signature verification any more than when using two
* buffers?
*/
return 0;
}
const int read_idmap[READING_MAX_ID] = {
[READING_FIRMWARE] = FIRMWARE_CHECK,
[READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK,
[READING_MODULE] = MODULE_CHECK,
[READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
[READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
[READING_POLICY] = POLICY_CHECK
};
/**
* ima_post_read_file - in memory collect/appraise/audit measurement
* @file: pointer to the file to be measured/appraised/audit
* @buf: pointer to in memory file contents
* @size: size of in memory file contents
* @read_id: caller identifier
*
* Measure/appraise/audit in memory file based on policy. Policy rules
* are written in terms of a policy identifier.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_post_read_file(struct file *file, void *buf, loff_t size,
enum kernel_read_file_id read_id)
{
enum ima_hooks func;
u32 secid;
if (!file && read_id == READING_FIRMWARE) {
if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
(ima_appraise & IMA_APPRAISE_ENFORCE)) {
pr_err("Prevent firmware loading_store.\n");
return -EACCES; /* INTEGRITY_UNKNOWN */
}
return 0;
}
/* permit signed certs */
if (!file && read_id == READING_X509_CERTIFICATE)
return 0;
if (!file || !buf || size == 0) { /* should never happen */
if (ima_appraise & IMA_APPRAISE_ENFORCE)
return -EACCES;
return 0;
}
func = read_idmap[read_id] ?: FILE_CHECK;
security_task_getsecid(current, &secid);
return process_measurement(file, current_cred(), secid, buf, size,
MAY_READ, func);
}
/**
* ima_load_data - appraise decision based on policy
* @id: kernel load data caller identifier
*
* Callers of this LSM hook can not measure, appraise, or audit the
* data provided by userspace. Enforce policy rules requring a file
* signature (eg. kexec'ed kernel image).
*
* For permission return 0, otherwise return -EACCES.
*/
int ima_load_data(enum kernel_load_data_id id)
{
bool ima_enforce, sig_enforce;
ima_enforce =
(ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
switch (id) {
case LOADING_KEXEC_IMAGE:
if (IS_ENABLED(CONFIG_KEXEC_SIG)
&& arch_ima_get_secureboot()) {
pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
return -EACCES;
}
if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
return -EACCES; /* INTEGRITY_UNKNOWN */
}
break;
case LOADING_FIRMWARE:
if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE)) {
pr_err("Prevent firmware sysfs fallback loading.\n");
return -EACCES; /* INTEGRITY_UNKNOWN */
}
break;
case LOADING_MODULE:
sig_enforce = is_module_sig_enforced();
if (ima_enforce && (!sig_enforce
&& (ima_appraise & IMA_APPRAISE_MODULES))) {
pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
return -EACCES; /* INTEGRITY_UNKNOWN */
}
default:
break;
}
return 0;
}
/*
* process_buffer_measurement - Measure the buffer to ima log.
* @buf: pointer to the buffer that needs to be added to the log.
* @size: size of buffer(in bytes).
* @eventname: event name to be used for the buffer entry.
* @cred: a pointer to a credentials structure for user validation.
* @secid: the secid of the task to be validated.
*
* Based on policy, the buffer is measured into the ima log.
*/
static void process_buffer_measurement(const void *buf, int size,
const char *eventname,
const struct cred *cred, u32 secid)
{
int ret = 0;
struct ima_template_entry *entry = NULL;
struct integrity_iint_cache iint = {};
struct ima_event_data event_data = {.iint = &iint,
.filename = eventname,
.buf = buf,
.buf_len = size};
struct ima_template_desc *template_desc = NULL;
struct {
struct ima_digest_data hdr;
char digest[IMA_MAX_DIGEST_SIZE];
} hash = {};
int violation = 0;
int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
int action = 0;
action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr,
&template_desc);
if (!(action & IMA_MEASURE))
return;
iint.ima_hash = &hash.hdr;
iint.ima_hash->algo = ima_hash_algo;
iint.ima_hash->length = hash_digest_size[ima_hash_algo];
ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
if (ret < 0)
goto out;
ret = ima_alloc_init_template(&event_data, &entry, template_desc);
if (ret < 0)
goto out;
ret = ima_store_template(entry, violation, NULL, buf, pcr);
if (ret < 0)
ima_free_template_entry(entry);
out:
return;
}
/**
* ima_kexec_cmdline - measure kexec cmdline boot args
* @buf: pointer to buffer
* @size: size of buffer
*
* Buffers can only be measured, not appraised.
*/
void ima_kexec_cmdline(const void *buf, int size)
{
u32 secid;
if (buf && size != 0) {
security_task_getsecid(current, &secid);
process_buffer_measurement(buf, size, "kexec-cmdline",
current_cred(), secid);
}
}
static int __init init_ima(void)
{
int error;
ima_init_template_list();
hash_setup(CONFIG_IMA_DEFAULT_HASH);
error = ima_init();
if (error && strcmp(hash_algo_name[ima_hash_algo],
CONFIG_IMA_DEFAULT_HASH) != 0) {
pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
hash_setup_done = 0;
hash_setup(CONFIG_IMA_DEFAULT_HASH);
error = ima_init();
}
error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier);
if (error)
pr_warn("Couldn't register LSM notifier, error %d\n", error);
if (!error)
ima_update_policy_flag();
return error;
}
late_initcall(init_ima); /* Start IMA after the TPM is available */