linux/security/integrity/ima/ima_appraise.c
Linus Torvalds 8b68150883 Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity
Pull integrity updates from Mimi Zohar:
 "Bug fixes, code clean up, and new features:

   - IMA policy rules can be defined in terms of LSM labels, making the
     IMA policy dependent on LSM policy label changes, in particular LSM
     label deletions. The new environment, in which IMA-appraisal is
     being used, frequently updates the LSM policy and permits LSM label
     deletions.

   - Prevent an mmap'ed shared file opened for write from also being
     mmap'ed execute. In the long term, making this and other similar
     changes at the VFS layer would be preferable.

   - The IMA per policy rule template format support is needed for a
     couple of new/proposed features (eg. kexec boot command line
     measurement, appended signatures, and VFS provided file hashes).

   - Other than the "boot-aggregate" record in the IMA measuremeent
     list, all other measurements are of file data. Measuring and
     storing the kexec boot command line in the IMA measurement list is
     the first buffer based measurement included in the measurement
     list"

* 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
  integrity: Introduce struct evm_xattr
  ima: Update MAX_TEMPLATE_NAME_LEN to fit largest reasonable definition
  KEXEC: Call ima_kexec_cmdline to measure the boot command line args
  IMA: Define a new template field buf
  IMA: Define a new hook to measure the kexec boot command line arguments
  IMA: support for per policy rule template formats
  integrity: Fix __integrity_init_keyring() section mismatch
  ima: Use designated initializers for struct ima_event_data
  ima: use the lsm policy update notifier
  LSM: switch to blocking policy update notifiers
  x86/ima: fix the Kconfig dependency for IMA_ARCH_POLICY
  ima: Make arch_policy_entry static
  ima: prevent a file already mmap'ed write to be mmap'ed execute
  x86/ima: check EFI SetupMode too
2019-07-08 20:28:59 -07:00

476 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2011 IBM Corporation
*
* Author:
* Mimi Zohar <zohar@us.ibm.com>
*/
#include <linux/init.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/magic.h>
#include <linux/ima.h>
#include <linux/evm.h>
#include "ima.h"
static int __init default_appraise_setup(char *str)
{
#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
if (strncmp(str, "off", 3) == 0)
ima_appraise = 0;
else if (strncmp(str, "log", 3) == 0)
ima_appraise = IMA_APPRAISE_LOG;
else if (strncmp(str, "fix", 3) == 0)
ima_appraise = IMA_APPRAISE_FIX;
#endif
return 1;
}
__setup("ima_appraise=", default_appraise_setup);
/*
* is_ima_appraise_enabled - return appraise status
*
* Only return enabled, if not in ima_appraise="fix" or "log" modes.
*/
bool is_ima_appraise_enabled(void)
{
return ima_appraise & IMA_APPRAISE_ENFORCE;
}
/*
* ima_must_appraise - set appraise flag
*
* Return 1 to appraise or hash
*/
int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
{
u32 secid;
if (!ima_appraise)
return 0;
security_task_getsecid(current, &secid);
return ima_match_policy(inode, current_cred(), secid, func, mask,
IMA_APPRAISE | IMA_HASH, NULL, NULL);
}
static int ima_fix_xattr(struct dentry *dentry,
struct integrity_iint_cache *iint)
{
int rc, offset;
u8 algo = iint->ima_hash->algo;
if (algo <= HASH_ALGO_SHA1) {
offset = 1;
iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
} else {
offset = 0;
iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
iint->ima_hash->xattr.ng.algo = algo;
}
rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
&iint->ima_hash->xattr.data[offset],
(sizeof(iint->ima_hash->xattr) - offset) +
iint->ima_hash->length, 0);
return rc;
}
/* Return specific func appraised cached result */
enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
enum ima_hooks func)
{
switch (func) {
case MMAP_CHECK:
return iint->ima_mmap_status;
case BPRM_CHECK:
return iint->ima_bprm_status;
case CREDS_CHECK:
return iint->ima_creds_status;
case FILE_CHECK:
case POST_SETATTR:
return iint->ima_file_status;
case MODULE_CHECK ... MAX_CHECK - 1:
default:
return iint->ima_read_status;
}
}
static void ima_set_cache_status(struct integrity_iint_cache *iint,
enum ima_hooks func,
enum integrity_status status)
{
switch (func) {
case MMAP_CHECK:
iint->ima_mmap_status = status;
break;
case BPRM_CHECK:
iint->ima_bprm_status = status;
break;
case CREDS_CHECK:
iint->ima_creds_status = status;
break;
case FILE_CHECK:
case POST_SETATTR:
iint->ima_file_status = status;
break;
case MODULE_CHECK ... MAX_CHECK - 1:
default:
iint->ima_read_status = status;
break;
}
}
static void ima_cache_flags(struct integrity_iint_cache *iint,
enum ima_hooks func)
{
switch (func) {
case MMAP_CHECK:
iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
break;
case BPRM_CHECK:
iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
break;
case CREDS_CHECK:
iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
break;
case FILE_CHECK:
case POST_SETATTR:
iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
break;
case MODULE_CHECK ... MAX_CHECK - 1:
default:
iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
break;
}
}
enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
int xattr_len)
{
struct signature_v2_hdr *sig;
enum hash_algo ret;
if (!xattr_value || xattr_len < 2)
/* return default hash algo */
return ima_hash_algo;
switch (xattr_value->type) {
case EVM_IMA_XATTR_DIGSIG:
sig = (typeof(sig))xattr_value;
if (sig->version != 2 || xattr_len <= sizeof(*sig))
return ima_hash_algo;
return sig->hash_algo;
break;
case IMA_XATTR_DIGEST_NG:
/* first byte contains algorithm id */
ret = xattr_value->data[0];
if (ret < HASH_ALGO__LAST)
return ret;
break;
case IMA_XATTR_DIGEST:
/* this is for backward compatibility */
if (xattr_len == 21) {
unsigned int zero = 0;
if (!memcmp(&xattr_value->data[16], &zero, 4))
return HASH_ALGO_MD5;
else
return HASH_ALGO_SHA1;
} else if (xattr_len == 17)
return HASH_ALGO_MD5;
break;
}
/* return default hash algo */
return ima_hash_algo;
}
int ima_read_xattr(struct dentry *dentry,
struct evm_ima_xattr_data **xattr_value)
{
ssize_t ret;
ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
0, GFP_NOFS);
if (ret == -EOPNOTSUPP)
ret = 0;
return ret;
}
/*
* ima_appraise_measurement - appraise file measurement
*
* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
* Assuming success, compare the xattr hash with the collected measurement.
*
* Return 0 on success, error code otherwise
*/
int ima_appraise_measurement(enum ima_hooks func,
struct integrity_iint_cache *iint,
struct file *file, const unsigned char *filename,
struct evm_ima_xattr_data *xattr_value,
int xattr_len)
{
static const char op[] = "appraise_data";
const char *cause = "unknown";
struct dentry *dentry = file_dentry(file);
struct inode *inode = d_backing_inode(dentry);
enum integrity_status status = INTEGRITY_UNKNOWN;
int rc = xattr_len, hash_start = 0;
if (!(inode->i_opflags & IOP_XATTR))
return INTEGRITY_UNKNOWN;
if (rc <= 0) {
if (rc && rc != -ENODATA)
goto out;
cause = iint->flags & IMA_DIGSIG_REQUIRED ?
"IMA-signature-required" : "missing-hash";
status = INTEGRITY_NOLABEL;
if (file->f_mode & FMODE_CREATED)
iint->flags |= IMA_NEW_FILE;
if ((iint->flags & IMA_NEW_FILE) &&
(!(iint->flags & IMA_DIGSIG_REQUIRED) ||
(inode->i_size == 0)))
status = INTEGRITY_PASS;
goto out;
}
status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
switch (status) {
case INTEGRITY_PASS:
case INTEGRITY_PASS_IMMUTABLE:
case INTEGRITY_UNKNOWN:
break;
case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */
case INTEGRITY_NOLABEL: /* No security.evm xattr. */
cause = "missing-HMAC";
goto out;
case INTEGRITY_FAIL: /* Invalid HMAC/signature. */
cause = "invalid-HMAC";
goto out;
default:
WARN_ONCE(true, "Unexpected integrity status %d\n", status);
}
switch (xattr_value->type) {
case IMA_XATTR_DIGEST_NG:
/* first byte contains algorithm id */
hash_start = 1;
/* fall through */
case IMA_XATTR_DIGEST:
if (iint->flags & IMA_DIGSIG_REQUIRED) {
cause = "IMA-signature-required";
status = INTEGRITY_FAIL;
break;
}
clear_bit(IMA_DIGSIG, &iint->atomic_flags);
if (xattr_len - sizeof(xattr_value->type) - hash_start >=
iint->ima_hash->length)
/* xattr length may be longer. md5 hash in previous
version occupied 20 bytes in xattr, instead of 16
*/
rc = memcmp(&xattr_value->data[hash_start],
iint->ima_hash->digest,
iint->ima_hash->length);
else
rc = -EINVAL;
if (rc) {
cause = "invalid-hash";
status = INTEGRITY_FAIL;
break;
}
status = INTEGRITY_PASS;
break;
case EVM_IMA_XATTR_DIGSIG:
set_bit(IMA_DIGSIG, &iint->atomic_flags);
rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
(const char *)xattr_value,
xattr_len,
iint->ima_hash->digest,
iint->ima_hash->length);
if (rc == -EOPNOTSUPP) {
status = INTEGRITY_UNKNOWN;
break;
}
if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
func == KEXEC_KERNEL_CHECK)
rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
(const char *)xattr_value,
xattr_len,
iint->ima_hash->digest,
iint->ima_hash->length);
if (rc) {
cause = "invalid-signature";
status = INTEGRITY_FAIL;
} else {
status = INTEGRITY_PASS;
}
break;
default:
status = INTEGRITY_UNKNOWN;
cause = "unknown-ima-data";
break;
}
out:
/*
* File signatures on some filesystems can not be properly verified.
* When such filesystems are mounted by an untrusted mounter or on a
* system not willing to accept such a risk, fail the file signature
* verification.
*/
if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) ||
(iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) {
status = INTEGRITY_FAIL;
cause = "unverifiable-signature";
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
op, cause, rc, 0);
} else if (status != INTEGRITY_PASS) {
/* Fix mode, but don't replace file signatures. */
if ((ima_appraise & IMA_APPRAISE_FIX) &&
(!xattr_value ||
xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
if (!ima_fix_xattr(dentry, iint))
status = INTEGRITY_PASS;
}
/* Permit new files with file signatures, but without data. */
if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) {
status = INTEGRITY_PASS;
}
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
op, cause, rc, 0);
} else {
ima_cache_flags(iint, func);
}
ima_set_cache_status(iint, func, status);
return status;
}
/*
* ima_update_xattr - update 'security.ima' hash value
*/
void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
{
struct dentry *dentry = file_dentry(file);
int rc = 0;
/* do not collect and update hash for digital signatures */
if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
return;
if ((iint->ima_file_status != INTEGRITY_PASS) &&
!(iint->flags & IMA_HASH))
return;
rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
if (rc < 0)
return;
inode_lock(file_inode(file));
ima_fix_xattr(dentry, iint);
inode_unlock(file_inode(file));
}
/**
* ima_inode_post_setattr - reflect file metadata changes
* @dentry: pointer to the affected dentry
*
* Changes to a dentry's metadata might result in needing to appraise.
*
* This function is called from notify_change(), which expects the caller
* to lock the inode's i_mutex.
*/
void ima_inode_post_setattr(struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
struct integrity_iint_cache *iint;
int action;
if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
|| !(inode->i_opflags & IOP_XATTR))
return;
action = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
if (!action)
__vfs_removexattr(dentry, XATTR_NAME_IMA);
iint = integrity_iint_find(inode);
if (iint) {
set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags);
if (!action)
clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
}
}
/*
* ima_protect_xattr - protect 'security.ima'
*
* Ensure that not just anyone can modify or remove 'security.ima'.
*/
static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return 1;
}
return 0;
}
static void ima_reset_appraise_flags(struct inode *inode, int digsig)
{
struct integrity_iint_cache *iint;
if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
return;
iint = integrity_iint_find(inode);
if (!iint)
return;
iint->measured_pcrs = 0;
set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags);
if (digsig)
set_bit(IMA_DIGSIG, &iint->atomic_flags);
else
clear_bit(IMA_DIGSIG, &iint->atomic_flags);
}
int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
const struct evm_ima_xattr_data *xvalue = xattr_value;
int result;
result = ima_protect_xattr(dentry, xattr_name, xattr_value,
xattr_value_len);
if (result == 1) {
if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
return -EINVAL;
ima_reset_appraise_flags(d_backing_inode(dentry),
xvalue->type == EVM_IMA_XATTR_DIGSIG);
result = 0;
}
return result;
}
int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
{
int result;
result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
if (result == 1) {
ima_reset_appraise_flags(d_backing_inode(dentry), 0);
result = 0;
}
return result;
}