linux/security/integrity/ima/ima_appraise.c

407 lines
9.9 KiB
C

/*
* Copyright (C) 2011 IBM Corporation
*
* Author:
* Mimi Zohar <zohar@us.ibm.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 2 of the License.
*/
#include <linux/module.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)
{
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;
return 1;
}
__setup("ima_appraise=", default_appraise_setup);
/*
* ima_must_appraise - set appraise flag
*
* Return 1 to appraise
*/
int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
{
if (!ima_appraise)
return 0;
return ima_match_policy(inode, func, mask, IMA_APPRAISE, 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 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 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 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;
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:
return xattr_value->digest[0];
break;
case IMA_XATTR_DIGEST:
/* this is for backward compatibility */
if (xattr_len == 21) {
unsigned int zero = 0;
if (!memcmp(&xattr_value->digest[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, int opened)
{
static const char op[] = "appraise_data";
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 = "missing-hash";
status = INTEGRITY_NOLABEL;
if (opened & FILE_CREATED) {
iint->flags |= IMA_NEW_FILE;
status = INTEGRITY_PASS;
}
goto out;
}
status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
if ((status == INTEGRITY_NOLABEL)
|| (status == INTEGRITY_NOXATTRS))
cause = "missing-HMAC";
else if (status == INTEGRITY_FAIL)
cause = "invalid-HMAC";
goto out;
}
switch (xattr_value->type) {
case IMA_XATTR_DIGEST_NG:
/* first byte contains algorithm id */
hash_start = 1;
case IMA_XATTR_DIGEST:
if (iint->flags & IMA_DIGSIG_REQUIRED) {
cause = "IMA-signature-required";
status = INTEGRITY_FAIL;
break;
}
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->digest[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:
iint->flags |= IMA_DIGSIG;
rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
(const char *)xattr_value, rc,
iint->ima_hash->digest,
iint->ima_hash->length);
if (rc == -EOPNOTSUPP) {
status = INTEGRITY_UNKNOWN;
} else if (rc) {
cause = "invalid-signature";
status = INTEGRITY_FAIL;
} else {
status = INTEGRITY_PASS;
}
break;
default:
status = INTEGRITY_UNKNOWN;
cause = "unknown-ima-data";
break;
}
out:
if (status != INTEGRITY_PASS) {
if ((ima_appraise & IMA_APPRAISE_FIX) &&
(!xattr_value ||
xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
if (!ima_fix_xattr(dentry, iint))
status = INTEGRITY_PASS;
} else 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 (iint->flags & IMA_DIGSIG)
return;
rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
if (rc < 0)
return;
ima_fix_xattr(dentry, iint);
}
/**
* 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 must_appraise;
if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
|| !(inode->i_opflags & IOP_XATTR))
return;
must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
iint = integrity_iint_find(inode);
if (iint) {
iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
IMA_ACTION_RULE_FLAGS);
if (must_appraise)
iint->flags |= IMA_APPRAISE;
}
if (!must_appraise)
__vfs_removexattr(dentry, XATTR_NAME_IMA);
}
/*
* 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->flags &= ~IMA_DONE_MASK;
iint->measured_pcrs = 0;
if (digsig)
iint->flags |= IMA_DIGSIG;
return;
}
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) ? 1 : 0);
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;
}