// SPDX-License-Identifier: GPL-2.0-only
/*
* Integrity Measurement Architecture
*
* Copyright (C) 2005,2006,2007,2008 IBM Corporation
*
* Authors:
* Reiner Sailer <[email protected]>
* Serge Hallyn <[email protected]>
* Kylene Hall <[email protected]>
* Mimi Zohar <[email protected]>
*
* File: ima_main.c
* implements the IMA hooks: ima_bprm_check, ima_file_mmap,
* and ima_file_check.
*/
#include <linux/module.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/kernel_read_file.h>
#include <linux/mount.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/ima.h>
#include <linux/fs.h>
#include <linux/iversion.h>
#include <linux/evm.h>
#include "ima.h"
#ifdef CONFIG_IMA_APPRAISE
int ima_appraise = IMA_APPRAISE_ENFORCE;
#else
int ima_appraise;
#endif
int __ro_after_init 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 {
pr_err("invalid hash algorithm \"%s\" for template \"%s\"",
str, IMA_TEMPLATE_IMA_NAME);
return 1;
}
goto out;
}
i = match_string(hash_algo_name, HASH_ALGO__LAST, str);
if (i < 0) {
pr_err("invalid hash algorithm \"%s\"", str);
return 1;
}
ima_hash_algo = i;
out:
hash_setup_done = 1;
return 1;
}
__setup("ima_hash=", hash_setup);
enum hash_algo ima_get_current_hash_algo(void)
{
return ima_hash_algo;
}
/* 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 || func == MMAP_CHECK_REQPROT) &&
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 ima_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 = ima_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 ima_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) {
struct kstat stat;
update = test_and_clear_bit(IMA_UPDATE_XATTR,
&iint->atomic_flags);
if ((iint->flags & IMA_NEW_FILE) ||
vfs_getattr_nosec(&file->f_path, &stat,
STATX_CHANGE_COOKIE,
AT_STATX_SYNC_AS_STAT) ||
!(stat.result_mask & STATX_CHANGE_COOKIE) ||
stat.change_cookie != iint->real_inode.version) {
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
*/
static void ima_file_free(struct file *file)
{
struct inode *inode = file_inode(file);
struct ima_iint_cache *iint;
if (!ima_policy_flag || !S_ISREG(inode->i_mode))
return;
iint = ima_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 *real_inode, *inode = file_inode(file);
struct ima_iint_cache *iint = NULL;
struct ima_template_desc *template_desc = NULL;
struct inode *metadata_inode;
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;
unsigned int allowed_algos = 0;
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(file_mnt_idmap(file), inode, cred, secid,
mask, func, &pcr, &template_desc, NULL,
&allowed_algos);
violation_check = ((func == FILE_CHECK || func == MMAP_CHECK ||
func == MMAP_CHECK_REQPROT) &&
(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 = ima_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_NONACTION_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;
}
/*
* On stacked filesystems, detect and re-evaluate file data and
* metadata changes.
*/
real_inode = d_real_inode(file_dentry(file));
if (real_inode != inode &&
(action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) {
if (!IS_I_VERSION(real_inode) ||
integrity_inode_attrs_changed(&iint->real_inode,
real_inode)) {
iint->flags &= ~IMA_DONE_MASK;
iint->measured_pcrs = 0;
}
/*
* Reset the EVM status when metadata changed.
*/
metadata_inode = d_inode(d_real(file_dentry(file),
D_REAL_METADATA));
if (evm_metadata_changed(inode, metadata_inode))
iint->flags &= ~(IMA_APPRAISED |
IMA_APPRAISED_SUBMASK);
}
/* 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, xattr_len);
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, xattr_len);
/*
* 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)) {
rc = ima_check_blacklist(iint, modsig, pcr);
if (rc != -EPERM) {
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;
/* Ensure the digest was generated using an allowed algorithm */
if (rc == 0 && must_appraise && allowed_algos != 0 &&
(allowed_algos & (1U << hash_algo)) == 0) {
rc = -EACCES;
integrity_audit_msg(AUDIT_INTEGRITY_DATA, file_inode(file),
pathname, "collect_data",
"denied-hash-algorithm", 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)
* @reqprot: protection requested by the application
* @prot: protection that will be applied by the kernel
* @flags: operational flags
*
* 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.
*/
static int ima_file_mmap(struct file *file, unsigned long reqprot,
unsigned long prot, unsigned long flags)
{
u32 secid;
int ret;
if (!file)
return 0;
security_current_getsecid_subj(&secid);
if (reqprot & PROT_EXEC) {
ret = process_measurement(file, current_cred(), secid, NULL,
0, MAY_EXEC, MMAP_CHECK_REQPROT);
if (ret)
return ret;
}
if (prot & PROT_EXEC)
return process_measurement(file, current_cred(), secid, NULL,
0, MAY_EXEC, MMAP_CHECK);
return 0;
}
/**
* ima_file_mprotect - based on policy, limit mprotect change
* @vma: vm_area_struct protection is set to
* @reqprot: protection requested by the application
* @prot: protection that will be applied by the kernel
*
* Files can be mmap'ed read/write and later changed to execute to circumvent
* IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore
* would be taken before i_mutex), files can not be measured or appraised at
* this point. Eliminate this integrity gap by denying the mprotect
* PROT_EXECUTE change, if an mmap appraise policy rule exists.
*
* On mprotect change success, return 0. On failure, return -EACESS.
*/
static int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
unsigned long prot)
{
struct ima_template_desc *template = NULL;
struct file *file;
char filename[NAME_MAX];
char *pathbuf = NULL;
const char *pathname = NULL;
struct inode *inode;
int result = 0;
int action;
u32 secid;
int pcr;
/* Is mprotect making an mmap'ed file executable? */
if (!(ima_policy_flag & IMA_APPRAISE) || !vma->vm_file ||
!(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC))
return 0;
security_current_getsecid_subj(&secid);
inode = file_inode(vma->vm_file);
action = ima_get_action(file_mnt_idmap(vma->vm_file), inode,
current_cred(), secid, MAY_EXEC, MMAP_CHECK,
&pcr, &template, NULL, NULL);
action |= ima_get_action(file_mnt_idmap(vma->vm_file), inode,
current_cred(), secid, MAY_EXEC,
MMAP_CHECK_REQPROT, &pcr, &template, NULL,
NULL);
/* Is the mmap'ed file in policy? */
if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))
return 0;
if (action & IMA_APPRAISE_SUBMASK)
result = -EPERM;
file = vma->vm_file;
pathname = ima_d_path(&file->f_path, &pathbuf, filename);
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, pathname,
"collect_data", "failed-mprotect", result, 0);
if (pathbuf)
__putname(pathbuf);
return result;
}
/**
* 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.
*/
static int ima_bprm_check(struct linux_binprm *bprm)
{
int ret;
u32 secid;
security_current_getsecid_subj(&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_file_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.
*/
static int ima_file_check(struct file *file, int mask)
{
u32 secid;
security_current_getsecid_subj(&secid);
return process_measurement(file, current_cred(), secid, NULL, 0,
mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
MAY_APPEND), FILE_CHECK);
}
static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
size_t buf_size)
{
struct ima_iint_cache *iint = NULL, tmp_iint;
int rc, hash_algo;
if (ima_policy_flag) {
iint = ima_iint_find(inode);
if (iint)
mutex_lock(&iint->mutex);
}
if ((!iint || !(iint->flags & IMA_COLLECTED)) && file) {
if (iint)
mutex_unlock(&iint->mutex);
memset(&tmp_iint, 0, sizeof(tmp_iint));
mutex_init(&tmp_iint.mutex);
rc = ima_collect_measurement(&tmp_iint, file, NULL, 0,
ima_hash_algo, NULL);
if (rc < 0) {
/* ima_hash could be allocated in case of failure. */
if (rc != -ENOMEM)
kfree(tmp_iint.ima_hash);
return -EOPNOTSUPP;
}
iint = &tmp_iint;
mutex_lock(&iint->mutex);
}
if (!iint)
return -EOPNOTSUPP;
/*
* ima_file_hash can be called when ima_collect_measurement has still
* not been called, we might not always have a hash.
*/
if (!iint->ima_hash || !(iint->flags & IMA_COLLECTED)) {
mutex_unlock(&iint->mutex);
return -EOPNOTSUPP;
}
if (buf) {
size_t copied_size;
copied_size = min_t(size_t, iint->ima_hash->length, buf_size);
memcpy(buf, iint->ima_hash->digest, copied_size);
}
hash_algo = iint->ima_hash->algo;
mutex_unlock(&iint->mutex);
if (iint == &tmp_iint)
kfree(iint->ima_hash);
return hash_algo;
}
/**
* ima_file_hash - return a measurement of the file
* @file: pointer to the file
* @buf: buffer in which to store the hash
* @buf_size: length of the buffer
*
* On success, return the hash algorithm (as defined in the enum hash_algo).
* If buf is not NULL, this function also outputs the hash into buf.
* If the hash is larger than buf_size, then only buf_size bytes will be copied.
* It generally just makes sense to pass a buffer capable of holding the largest
* possible hash: IMA_MAX_DIGEST_SIZE.
* The file hash returned is based on the entire file, including the appended
* signature.
*
* If the measurement cannot be performed, return -EOPNOTSUPP.
* If the parameters are incorrect, return -EINVAL.
*/
int ima_file_hash(struct file *file, char *buf, size_t buf_size)
{
if (!file)
return -EINVAL;
return __ima_inode_hash(file_inode(file), file, buf, buf_size);
}
EXPORT_SYMBOL_GPL(ima_file_hash);
/**
* ima_inode_hash - return the stored measurement if the inode has been hashed
* and is in the iint cache.
* @inode: pointer to the inode
* @buf: buffer in which to store the hash
* @buf_size: length of the buffer
*
* On success, return the hash algorithm (as defined in the enum hash_algo).
* If buf is not NULL, this function also outputs the hash into buf.
* If the hash is larger than buf_size, then only buf_size bytes will be copied.
* It generally just makes sense to pass a buffer capable of holding the largest
* possible hash: IMA_MAX_DIGEST_SIZE.
* The hash returned is based on the entire contents, including the appended
* signature.
*
* If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
* If the parameters are incorrect, return -EINVAL.
*/
int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
{
if (!inode)
return -EINVAL;
return __ima_inode_hash(inode, NULL, buf, buf_size);
}
EXPORT_SYMBOL_GPL(ima_inode_hash);
/**
* ima_post_create_tmpfile - mark newly created tmpfile as new
* @idmap: idmap of the mount the inode was found from
* @inode: inode of the 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.
*/
static void ima_post_create_tmpfile(struct mnt_idmap *idmap,
struct inode *inode)
{
struct ima_iint_cache *iint;
int must_appraise;
if (!ima_policy_flag || !S_ISREG(inode->i_mode))
return;
must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS,
FILE_CHECK);
if (!must_appraise)
return;
/* Nothing to do if we can't allocate memory */
iint = ima_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
* @idmap: idmap of the mount the inode was found from
* @dentry: newly created dentry
*
* Mark files created via the mknodat syscall as new, so that the
* file data can be written later.
*/
static void ima_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry)
{
struct ima_iint_cache *iint;
struct inode *inode = dentry->d_inode;
int must_appraise;
if (!ima_policy_flag || !S_ISREG(inode->i_mode))
return;
must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS,
FILE_CHECK);
if (!must_appraise)
return;
/* Nothing to do if we can't allocate memory */
iint = ima_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
* @contents: whether a subsequent call will be made to ima_post_read_file()
*
* 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.
*/
static int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
bool contents)
{
enum ima_hooks func;
u32 secid;
/*
* 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? It may be desirable to include the buffer address
* in this API and walk all the dma_map_single() mappings to check.
*/
/*
* There will be a call made to ima_post_read_file() with
* a filled buffer, so we don't need to perform an extra
* read early here.
*/
if (contents)
return 0;
/* Read entire file for all partial reads. */
func = read_idmap[read_id] ?: FILE_CHECK;
security_current_getsecid_subj(&secid);
return process_measurement(file, current_cred(), secid, NULL,
0, MAY_READ, func);
}
const int read_idmap[READING_MAX_ID] = {
[READING_FIRMWARE] = 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.
*/
static int ima_post_read_file(struct file *file, char *buf, loff_t size,
enum kernel_read_file_id read_id)
{
enum ima_hooks func;
u32 secid;
/* 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_current_getsecid_subj(&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
* @contents: whether the full contents will be available in a later
* call to ima_post_load_data().
*
* Callers of this LSM hook can not measure, appraise, or audit the
* data provided by userspace. Enforce policy rules requiring a file
* signature (eg. kexec'ed kernel image).
*
* For permission return 0, otherwise return -EACCES.
*/
static int ima_load_data(enum kernel_load_data_id id, bool contents)
{
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) && !contents) {
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 */
}
break;
default:
break;
}
return 0;
}
/**
* ima_post_load_data - appraise decision based on policy
* @buf: pointer to in memory file contents
* @size: size of in memory file contents
* @load_id: kernel load data caller identifier
* @description: @load_id-specific description of contents
*
* Measure/appraise/audit in memory buffer 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.
*/
static int ima_post_load_data(char *buf, loff_t size,
enum kernel_load_data_id load_id,
char *description)
{
if (load_id == LOADING_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;
}
/*
* Measure the init_module syscall buffer containing the ELF image.
*/
if (load_id == LOADING_MODULE)
ima_measure_critical_data("modules", "init_module",
buf, size, true, NULL, 0);
return 0;
}
/**
* process_buffer_measurement - Measure the buffer or the buffer data hash
* @idmap: idmap of the mount the inode was found from
* @inode: inode associated with the object being measured (NULL for KEY_CHECK)
* @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.
* @func: IMA hook
* @pcr: pcr to extend the measurement
* @func_data: func specific data, may be NULL
* @buf_hash: measure buffer data hash
* @digest: buffer digest will be written to
* @digest_len: buffer length
*
* Based on policy, either the buffer data or buffer data hash is measured
*
* Return: 0 if the buffer has been successfully measured, 1 if the digest
* has been written to the passed location but not added to a measurement entry,
* a negative value otherwise.
*/
int process_buffer_measurement(struct mnt_idmap *idmap,
struct inode *inode, const void *buf, int size,
const char *eventname, enum ima_hooks func,
int pcr, const char *func_data,
bool buf_hash, u8 *digest, size_t digest_len)
{
int ret = 0;
const char *audit_cause = "ENOMEM";
struct ima_template_entry *entry = NULL;
struct ima_iint_cache iint = {};
struct ima_event_data event_data = {.iint = &iint,
.filename = eventname,
.buf = buf,
.buf_len = size};
struct ima_template_desc *template;
struct ima_max_digest_data hash;
struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
struct ima_digest_data, hdr);
char digest_hash[IMA_MAX_DIGEST_SIZE];
int digest_hash_len = hash_digest_size[ima_hash_algo];
int violation = 0;
int action = 0;
u32 secid;
if (digest && digest_len < digest_hash_len)
return -EINVAL;
if (!ima_policy_flag && !digest)
return -ENOENT;
template = ima_template_desc_buf();
if (!template) {
ret = -EINVAL;
audit_cause = "ima_template_desc_buf";
goto out;
}
/*
* Both LSM hooks and auxilary based buffer measurements are
* based on policy. To avoid code duplication, differentiate
* between the LSM hooks and auxilary buffer measurements,
* retrieving the policy rule information only for the LSM hook
* buffer measurements.
*/
if (func) {
security_current_getsecid_subj(&secid);
action = ima_get_action(idmap, inode, current_cred(),
secid, 0, func, &pcr, &template,
func_data, NULL);
if (!(action & IMA_MEASURE) && !digest)
return -ENOENT;
}
if (!pcr)
pcr = CONFIG_IMA_MEASURE_PCR_IDX;
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) {
audit_cause = "hashing_error";
goto out;
}
if (buf_hash) {
memcpy(digest_hash, hash_hdr->digest, digest_hash_len);
ret = ima_calc_buffer_hash(digest_hash, digest_hash_len,
iint.ima_hash);
if (ret < 0) {
audit_cause = "hashing_error";
goto out;
}
event_data.buf = digest_hash;
event_data.buf_len = digest_hash_len;
}
if (digest)
memcpy(digest, iint.ima_hash->digest, digest_hash_len);
if (!ima_policy_flag || (func && !(action & IMA_MEASURE)))
return 1;
ret = ima_alloc_init_template(&event_data, &entry, template);
if (ret < 0) {
audit_cause = "alloc_entry";
goto out;
}
ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr);
if (ret < 0) {
audit_cause = "store_entry";
ima_free_template_entry(entry);
}
out:
if (ret < 0)
integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL, eventname,
func_measure_str(func),
audit_cause, ret, 0, ret);
return ret;
}
/**
* ima_kexec_cmdline - measure kexec cmdline boot args
* @kernel_fd: file descriptor of the kexec kernel being loaded
* @buf: pointer to buffer
* @size: size of buffer
*
* Buffers can only be measured, not appraised.
*/
void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
{
struct fd f;
if (!buf || !size)
return;
f = fdget(kernel_fd);
if (!fd_file(f))
return;
process_buffer_measurement(file_mnt_idmap(fd_file(f)), file_inode(fd_file(f)),
buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
NULL, false, NULL, 0);
fdput(f);
}
/**
* ima_measure_critical_data - measure kernel integrity critical data
* @event_label: unique event label for grouping and limiting critical data
* @event_name: event name for the record in the IMA measurement list
* @buf: pointer to buffer data
* @buf_len: length of buffer data (in bytes)
* @hash: measure buffer data hash
* @digest: buffer digest will be written to
* @digest_len: buffer length
*
* Measure data critical to the integrity of the kernel into the IMA log
* and extend the pcr. Examples of critical data could be various data
* structures, policies, and states stored in kernel memory that can
* impact the integrity of the system.
*
* Return: 0 if the buffer has been successfully measured, 1 if the digest
* has been written to the passed location but not added to a measurement entry,
* a negative value otherwise.
*/
int ima_measure_critical_data(const char *event_label,
const char *event_name,
const void *buf, size_t buf_len,
bool hash, u8 *digest, size_t digest_len)
{
if (!event_name || !event_label || !buf || !buf_len)
return -ENOPARAM;
return process_buffer_measurement(&nop_mnt_idmap, NULL, buf, buf_len,
event_name, CRITICAL_DATA, 0,
event_label, hash, digest,
digest_len);
}
EXPORT_SYMBOL_GPL(ima_measure_critical_data);
#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
/**
* ima_kernel_module_request - Prevent crypto-pkcs1pad(rsa,*) requests
* @kmod_name: kernel module name
*
* Avoid a verification loop where verifying the signature of the modprobe
* binary requires executing modprobe itself. Since the modprobe iint->mutex
* is already held when the signature verification is performed, a deadlock
* occurs as soon as modprobe is executed within the critical region, since
* the same lock cannot be taken again.
*
* This happens when public_key_verify_signature(), in case of RSA algorithm,
* use alg_name to store internal information in order to construct an
* algorithm on the fly, but crypto_larval_lookup() will try to use alg_name
* in order to load a kernel module with same name.
*
* Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules,
* we are safe to fail such module request from crypto_larval_lookup(), and
* avoid the verification loop.
*
* Return: Zero if it is safe to load the kernel module, -EINVAL otherwise.
*/
static int ima_kernel_module_request(char *kmod_name)
{
if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
return -EINVAL;
return 0;
}
#endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */
static int __init init_ima(void)
{
int error;
ima_appraise_parse_cmdline();
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();
}
if (error)
return error;
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_flags();
return error;
}
static struct security_hook_list ima_hooks[] __ro_after_init = {
LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
LSM_HOOK_INIT(file_post_open, ima_file_check),
LSM_HOOK_INIT(inode_post_create_tmpfile, ima_post_create_tmpfile),
LSM_HOOK_INIT(file_release, ima_file_free),
LSM_HOOK_INIT(mmap_file, ima_file_mmap),
LSM_HOOK_INIT(file_mprotect, ima_file_mprotect),
LSM_HOOK_INIT(kernel_load_data, ima_load_data),
LSM_HOOK_INIT(kernel_post_load_data, ima_post_load_data),
LSM_HOOK_INIT(kernel_read_file, ima_read_file),
LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file),
LSM_HOOK_INIT(path_post_mknod, ima_post_path_mknod),
#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
LSM_HOOK_INIT(key_post_create_or_update, ima_post_key_create_or_update),
#endif
#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
LSM_HOOK_INIT(kernel_module_request, ima_kernel_module_request),
#endif
LSM_HOOK_INIT(inode_free_security_rcu, ima_inode_free_rcu),
};
static const struct lsm_id ima_lsmid = {
.name = "ima",
.id = LSM_ID_IMA,
};
static int __init init_ima_lsm(void)
{
ima_iintcache_init();
security_add_hooks(ima_hooks, ARRAY_SIZE(ima_hooks), &ima_lsmid);
init_ima_appraise_lsm(&ima_lsmid);
return 0;
}
struct lsm_blob_sizes ima_blob_sizes __ro_after_init = {
.lbs_inode = sizeof(struct ima_iint_cache *),
};
DEFINE_LSM(ima) = {
.name = "ima",
.init = init_ima_lsm,
.order = LSM_ORDER_LAST,
.blobs = &ima_blob_sizes,
};
late_initcall(init_ima); /* Start IMA after the TPM is available */
Codebase Browser
linux