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![Mimi Zohar](/assets/img/avatar_default.png)
With the new IMA policy 'appraise_type=' option, different hooks can require different methods for appraising a file's integrity. For example, the existing 'ima_appraise_tcb' policy defines a generic rule, requiring all root files to be appraised, without specfying the appraisal method. A more specific rule could require all kernel modules, for example, to be signed. appraise fowner=0 func=MODULE_CHECK appraise_type=imasig appraise fowner=0 As a result, the integrity appraisal results for the same inode, but for different hooks, could differ. This patch caches the integrity appraisal results on a per hook basis. Changelog v2: - Rename ima_cache_status() to ima_set_cache_status() - Rename and move get_appraise_status() to ima_get_cache_status() Changelog v0: - include IMA_APPRAISE/APPRAISED_SUBMASK in IMA_DO/DONE_MASK (Dmitry) - Support independent MODULE_CHECK appraise status. - fixed IMA_XXXX_APPRAISE/APPRAISED flags Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
317 lines
7.5 KiB
C
317 lines
7.5 KiB
C
/*
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* Copyright (C) 2011 IBM Corporation
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*
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* Author:
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* Mimi Zohar <zohar@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2 of the License.
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*/
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#include <linux/module.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/xattr.h>
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#include <linux/magic.h>
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#include <linux/ima.h>
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#include <linux/evm.h>
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#include "ima.h"
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static int __init default_appraise_setup(char *str)
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{
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if (strncmp(str, "off", 3) == 0)
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ima_appraise = 0;
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else if (strncmp(str, "fix", 3) == 0)
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ima_appraise = IMA_APPRAISE_FIX;
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return 1;
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}
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__setup("ima_appraise=", default_appraise_setup);
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/*
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* ima_must_appraise - set appraise flag
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*
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* Return 1 to appraise
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*/
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int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
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{
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if (!ima_appraise)
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return 0;
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return ima_match_policy(inode, func, mask, IMA_APPRAISE);
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}
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static int ima_fix_xattr(struct dentry *dentry,
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struct integrity_iint_cache *iint)
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{
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iint->ima_xattr.type = IMA_XATTR_DIGEST;
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return __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
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(u8 *)&iint->ima_xattr,
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sizeof(iint->ima_xattr), 0);
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}
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/* Return specific func appraised cached result */
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enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
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int func)
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{
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switch(func) {
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case MMAP_CHECK:
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return iint->ima_mmap_status;
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case BPRM_CHECK:
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return iint->ima_bprm_status;
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case MODULE_CHECK:
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return iint->ima_module_status;
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case FILE_CHECK:
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default:
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return iint->ima_file_status;
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}
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}
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static void ima_set_cache_status(struct integrity_iint_cache *iint,
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int func, enum integrity_status status)
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{
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switch(func) {
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case MMAP_CHECK:
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iint->ima_mmap_status = status;
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break;
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case BPRM_CHECK:
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iint->ima_bprm_status = status;
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break;
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case MODULE_CHECK:
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iint->ima_module_status = status;
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break;
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case FILE_CHECK:
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default:
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iint->ima_file_status = status;
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break;
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}
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}
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static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
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{
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switch(func) {
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case MMAP_CHECK:
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iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
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break;
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case BPRM_CHECK:
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iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
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break;
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case MODULE_CHECK:
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iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED);
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break;
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case FILE_CHECK:
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default:
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iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
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break;
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}
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}
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/*
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* ima_appraise_measurement - appraise file measurement
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*
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* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
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* Assuming success, compare the xattr hash with the collected measurement.
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*
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* Return 0 on success, error code otherwise
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*/
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int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
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struct file *file, const unsigned char *filename)
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{
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struct dentry *dentry = file->f_dentry;
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struct inode *inode = dentry->d_inode;
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struct evm_ima_xattr_data *xattr_value = NULL;
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enum integrity_status status = INTEGRITY_UNKNOWN;
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const char *op = "appraise_data";
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char *cause = "unknown";
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int rc;
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if (!ima_appraise)
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return 0;
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if (!inode->i_op->getxattr)
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return INTEGRITY_UNKNOWN;
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rc = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)&xattr_value,
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0, GFP_NOFS);
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if (rc <= 0) {
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if (rc && rc != -ENODATA)
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goto out;
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cause = "missing-hash";
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status =
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(inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
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goto out;
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}
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status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
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if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
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if ((status == INTEGRITY_NOLABEL)
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|| (status == INTEGRITY_NOXATTRS))
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cause = "missing-HMAC";
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else if (status == INTEGRITY_FAIL)
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cause = "invalid-HMAC";
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goto out;
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}
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switch (xattr_value->type) {
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case IMA_XATTR_DIGEST:
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if (iint->flags & IMA_DIGSIG_REQUIRED) {
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cause = "IMA signature required";
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status = INTEGRITY_FAIL;
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break;
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}
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rc = memcmp(xattr_value->digest, iint->ima_xattr.digest,
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IMA_DIGEST_SIZE);
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if (rc) {
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cause = "invalid-hash";
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status = INTEGRITY_FAIL;
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break;
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}
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status = INTEGRITY_PASS;
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break;
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case EVM_IMA_XATTR_DIGSIG:
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iint->flags |= IMA_DIGSIG;
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rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
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xattr_value->digest, rc - 1,
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iint->ima_xattr.digest,
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IMA_DIGEST_SIZE);
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if (rc == -EOPNOTSUPP) {
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status = INTEGRITY_UNKNOWN;
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} else if (rc) {
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cause = "invalid-signature";
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status = INTEGRITY_FAIL;
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} else {
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status = INTEGRITY_PASS;
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}
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break;
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default:
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status = INTEGRITY_UNKNOWN;
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cause = "unknown-ima-data";
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break;
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}
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out:
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if (status != INTEGRITY_PASS) {
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if ((ima_appraise & IMA_APPRAISE_FIX) &&
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(!xattr_value ||
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xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
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if (!ima_fix_xattr(dentry, iint))
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status = INTEGRITY_PASS;
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}
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integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
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op, cause, rc, 0);
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} else {
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ima_cache_flags(iint, func);
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}
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ima_set_cache_status(iint, func, status);
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kfree(xattr_value);
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return status;
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}
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/*
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* ima_update_xattr - update 'security.ima' hash value
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*/
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void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
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{
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struct dentry *dentry = file->f_dentry;
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int rc = 0;
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/* do not collect and update hash for digital signatures */
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if (iint->flags & IMA_DIGSIG)
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return;
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rc = ima_collect_measurement(iint, file);
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if (rc < 0)
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return;
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ima_fix_xattr(dentry, iint);
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}
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/**
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* ima_inode_post_setattr - reflect file metadata changes
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* @dentry: pointer to the affected dentry
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*
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* Changes to a dentry's metadata might result in needing to appraise.
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*
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* This function is called from notify_change(), which expects the caller
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* to lock the inode's i_mutex.
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*/
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void ima_inode_post_setattr(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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struct integrity_iint_cache *iint;
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int must_appraise, rc;
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if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)
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|| !inode->i_op->removexattr)
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return;
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must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
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iint = integrity_iint_find(inode);
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if (iint) {
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iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
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IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
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IMA_ACTION_FLAGS);
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if (must_appraise)
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iint->flags |= IMA_APPRAISE;
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}
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if (!must_appraise)
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rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
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return;
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}
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/*
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* ima_protect_xattr - protect 'security.ima'
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*
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* Ensure that not just anyone can modify or remove 'security.ima'.
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*/
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static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len)
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{
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if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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return 1;
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}
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return 0;
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}
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static void ima_reset_appraise_flags(struct inode *inode)
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{
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struct integrity_iint_cache *iint;
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if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode))
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return;
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iint = integrity_iint_find(inode);
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if (!iint)
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return;
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iint->flags &= ~IMA_DONE_MASK;
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return;
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}
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int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len)
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{
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int result;
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result = ima_protect_xattr(dentry, xattr_name, xattr_value,
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xattr_value_len);
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if (result == 1) {
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ima_reset_appraise_flags(dentry->d_inode);
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result = 0;
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}
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return result;
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}
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int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
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{
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int result;
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result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
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if (result == 1) {
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ima_reset_appraise_flags(dentry->d_inode);
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result = 0;
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}
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return result;
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}
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