// 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 [31mCONFIG_IMA_APPRAISE_BOOTPARAM[0m
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;
}
/*
* xattr_verify - verify xattr digest or signature
*
* Verify whether the hash or signature matches the file contents.
*
* Return 0 on success, error code otherwise.
*/
static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
struct evm_ima_xattr_data *xattr_value, int xattr_len,
enum integrity_status *status, const char **cause)
{
int rc = -EINVAL, hash_start = 0;
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([31mCONFIG_INTEGRITY_PLATFORM_KEYRING[0m) && 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;
}
return rc;
}
/*
* modsig_verify - verify modsig signature
*
* Verify whether the signature matches the file contents.
*
* Return 0 on success, error code otherwise.
*/
static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
enum integrity_status *status, const char **cause)
{
int rc;
rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig);
if (IS_ENABLED([31mCONFIG_INTEGRITY_PLATFORM_KEYRING[0m) && rc &&
func == KEXEC_KERNEL_CHECK)
rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM,
modsig);
if (rc) {
*cause = "invalid-signature";
*status = INTEGRITY_FAIL;
} else {
*status = INTEGRITY_PASS;
}
return rc;
}
/*
* 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, const struct modsig *modsig)
{
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;
bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;
/* If not appraising a modsig, we need an xattr. */
if (!(inode->i_opflags & IOP_XATTR) && !try_modsig)
return INTEGRITY_UNKNOWN;
/* If reading the xattr failed and there's no modsig, error out. */
if (rc <= 0 && !try_modsig) {
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. */
/* It's fine not to have xattrs when using a modsig. */
if (try_modsig)
break;
/* fall through */
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);
}
if (xattr_value)
rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
&cause);
/*
* If we have a modsig and either no imasig or the imasig's key isn't
* known, then try verifying the modsig.
*/
if (try_modsig &&
(!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG ||
rc == -ENOKEY))
rc = modsig_verify(func, modsig, &status, &cause);
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) && !try_modsig &&
(!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, NULL);
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;
}