This patch fixes the detection of the 'open_writers' violation for mmaped files. before) an 'open_writers' violation is detected if the policy contains a rule with the criteria: func=FILE_CHECK mask=MAY_READ after) an 'open_writers' violation is detected if the current event matches one of the policy rules. With the old behaviour, the 'open_writers' violation is not detected in the following case: policy: measure func=FILE_MMAP mask=MAY_EXEC steps: 1) open a shared library for writing 2) execute a binary that links that shared library 3) during the binary execution, modify the shared library and save the change result: the 'open_writers' violation measurement is not present in the IMA list. Only binaries executed are protected from writes. For libraries mapped in memory there is the flag MAP_DENYWRITE for this purpose, but according to the output of 'man mmap', the mmap flag is ignored. Since ima_rdwr_violation_check() is now called by process_measurement() the information about if the inode must be measured is already provided by ima_get_action(). Thus the unnecessary function ima_must_measure() has been removed. Changes in v3 (Dmitry Kasatkin): - Violation for MMAP_CHECK function are verified since this patch - Changed patch description a bit Signed-off-by: Roberto Sassu <roberto.sassu@polito.it> Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
361 lines
9.6 KiB
C
361 lines
9.6 KiB
C
/*
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* Copyright (C) 2005,2006,2007,2008 IBM Corporation
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*
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* Authors:
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* Reiner Sailer <sailer@watson.ibm.com>
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* Serge Hallyn <serue@us.ibm.com>
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* Kylene Hall <kylene@us.ibm.com>
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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
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*
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* File: ima_main.c
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* implements the IMA hooks: ima_bprm_check, ima_file_mmap,
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* and ima_file_check.
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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/binfmts.h>
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#include <linux/mount.h>
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#include <linux/mman.h>
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#include <linux/slab.h>
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#include <linux/xattr.h>
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#include <linux/ima.h>
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#include <crypto/hash_info.h>
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#include "ima.h"
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int ima_initialized;
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#ifdef CONFIG_IMA_APPRAISE
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int ima_appraise = IMA_APPRAISE_ENFORCE;
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#else
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int ima_appraise;
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#endif
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int ima_hash_algo = HASH_ALGO_SHA1;
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static int hash_setup_done;
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static int __init hash_setup(char *str)
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{
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struct ima_template_desc *template_desc = ima_template_desc_current();
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int i;
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if (hash_setup_done)
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return 1;
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if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
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if (strncmp(str, "sha1", 4) == 0)
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ima_hash_algo = HASH_ALGO_SHA1;
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else if (strncmp(str, "md5", 3) == 0)
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ima_hash_algo = HASH_ALGO_MD5;
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goto out;
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}
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for (i = 0; i < HASH_ALGO__LAST; i++) {
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if (strcmp(str, hash_algo_name[i]) == 0) {
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ima_hash_algo = i;
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break;
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}
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}
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out:
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hash_setup_done = 1;
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return 1;
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}
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__setup("ima_hash=", hash_setup);
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/*
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* ima_rdwr_violation_check
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*
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* Only invalidate the PCR for measured files:
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* - Opening a file for write when already open for read,
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* results in a time of measure, time of use (ToMToU) error.
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* - Opening a file for read when already open for write,
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* could result in a file measurement error.
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*
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*/
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static void ima_rdwr_violation_check(struct file *file,
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struct integrity_iint_cache *iint,
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int must_measure,
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char **pathbuf,
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const char **pathname)
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{
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struct inode *inode = file_inode(file);
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fmode_t mode = file->f_mode;
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bool send_tomtou = false, send_writers = false;
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if (mode & FMODE_WRITE) {
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if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
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if (!iint)
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iint = integrity_iint_find(inode);
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/* IMA_MEASURE is set from reader side */
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if (iint && (iint->flags & IMA_MEASURE))
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send_tomtou = true;
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}
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} else {
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if ((atomic_read(&inode->i_writecount) > 0) && must_measure)
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send_writers = true;
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}
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if (!send_tomtou && !send_writers)
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return;
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*pathname = ima_d_path(&file->f_path, pathbuf);
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if (send_tomtou)
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ima_add_violation(file, *pathname, "invalid_pcr", "ToMToU");
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if (send_writers)
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ima_add_violation(file, *pathname,
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"invalid_pcr", "open_writers");
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}
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static void ima_check_last_writer(struct integrity_iint_cache *iint,
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struct inode *inode, struct file *file)
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{
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fmode_t mode = file->f_mode;
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if (!(mode & FMODE_WRITE))
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return;
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mutex_lock(&inode->i_mutex);
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if (atomic_read(&inode->i_writecount) == 1) {
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if ((iint->version != inode->i_version) ||
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(iint->flags & IMA_NEW_FILE)) {
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iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
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if (iint->flags & IMA_APPRAISE)
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ima_update_xattr(iint, file);
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}
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}
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mutex_unlock(&inode->i_mutex);
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}
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/**
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* ima_file_free - called on __fput()
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* @file: pointer to file structure being freed
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*
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* Flag files that changed, based on i_version
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*/
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void ima_file_free(struct file *file)
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{
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struct inode *inode = file_inode(file);
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struct integrity_iint_cache *iint;
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if (!iint_initialized || !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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ima_check_last_writer(iint, inode, file);
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}
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static int process_measurement(struct file *file, int mask, int function,
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int opened)
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{
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struct inode *inode = file_inode(file);
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struct integrity_iint_cache *iint = NULL;
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struct ima_template_desc *template_desc;
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char *pathbuf = NULL;
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const char *pathname = NULL;
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int rc = -ENOMEM, action, must_appraise;
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struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL;
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int xattr_len = 0;
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bool violation_check;
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if (!ima_policy_flag || !S_ISREG(inode->i_mode))
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return 0;
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/* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
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* bitmask based on the appraise/audit/measurement policy.
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* Included is the appraise submask.
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*/
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action = ima_get_action(inode, mask, function);
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violation_check = ((function == FILE_CHECK || function == MMAP_CHECK) &&
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(ima_policy_flag & IMA_MEASURE));
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if (!action && !violation_check)
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return 0;
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must_appraise = action & IMA_APPRAISE;
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/* Is the appraise rule hook specific? */
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if (action & IMA_FILE_APPRAISE)
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function = FILE_CHECK;
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mutex_lock(&inode->i_mutex);
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if (action) {
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iint = integrity_inode_get(inode);
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if (!iint)
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goto out;
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}
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if (violation_check) {
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ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
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&pathbuf, &pathname);
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if (!action) {
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rc = 0;
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goto out_free;
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}
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}
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/* Determine if already appraised/measured based on bitmask
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* (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
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* IMA_AUDIT, IMA_AUDITED)
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*/
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iint->flags |= action;
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action &= IMA_DO_MASK;
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action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
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/* Nothing to do, just return existing appraised status */
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if (!action) {
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if (must_appraise)
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rc = ima_get_cache_status(iint, function);
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goto out_digsig;
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}
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template_desc = ima_template_desc_current();
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if ((action & IMA_APPRAISE_SUBMASK) ||
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strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
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xattr_ptr = &xattr_value;
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rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
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if (rc != 0) {
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if (file->f_flags & O_DIRECT)
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rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
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goto out_digsig;
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}
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if (!pathname) /* ima_rdwr_violation possibly pre-fetched */
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pathname = ima_d_path(&file->f_path, &pathbuf);
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if (action & IMA_MEASURE)
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ima_store_measurement(iint, file, pathname,
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xattr_value, xattr_len);
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if (action & IMA_APPRAISE_SUBMASK)
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rc = ima_appraise_measurement(function, iint, file, pathname,
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xattr_value, xattr_len, opened);
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if (action & IMA_AUDIT)
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ima_audit_measurement(iint, pathname);
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out_digsig:
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if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
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rc = -EACCES;
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kfree(xattr_value);
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out_free:
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kfree(pathbuf);
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out:
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mutex_unlock(&inode->i_mutex);
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if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
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return -EACCES;
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return 0;
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}
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/**
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* ima_file_mmap - based on policy, collect/store measurement.
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* @file: pointer to the file to be measured (May be NULL)
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* @prot: contains the protection that will be applied by the kernel.
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*
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* Measure files being mmapped executable based on the ima_must_measure()
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* policy decision.
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*
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* On success return 0. On integrity appraisal error, assuming the file
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* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
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*/
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int ima_file_mmap(struct file *file, unsigned long prot)
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{
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if (file && (prot & PROT_EXEC))
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return process_measurement(file, MAY_EXEC, MMAP_CHECK, 0);
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return 0;
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}
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/**
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* ima_bprm_check - based on policy, collect/store measurement.
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* @bprm: contains the linux_binprm structure
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*
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* The OS protects against an executable file, already open for write,
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* from being executed in deny_write_access() and an executable file,
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* already open for execute, from being modified in get_write_access().
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* So we can be certain that what we verify and measure here is actually
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* what is being executed.
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*
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* On success return 0. On integrity appraisal error, assuming the file
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* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
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*/
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int ima_bprm_check(struct linux_binprm *bprm)
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{
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return process_measurement(bprm->file, MAY_EXEC, BPRM_CHECK, 0);
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}
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/**
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* ima_path_check - based on policy, collect/store measurement.
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* @file: pointer to the file to be measured
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* @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
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*
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* Measure files based on the ima_must_measure() policy decision.
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*
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* On success return 0. On integrity appraisal error, assuming the file
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* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
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*/
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int ima_file_check(struct file *file, int mask, int opened)
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{
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return process_measurement(file,
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mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
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FILE_CHECK, opened);
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}
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EXPORT_SYMBOL_GPL(ima_file_check);
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/**
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* ima_module_check - based on policy, collect/store/appraise measurement.
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* @file: pointer to the file to be measured/appraised
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*
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* Measure/appraise kernel modules based on policy.
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*
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* On success return 0. On integrity appraisal error, assuming the file
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* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
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*/
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int ima_module_check(struct file *file)
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{
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if (!file) {
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#ifndef CONFIG_MODULE_SIG_FORCE
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if ((ima_appraise & IMA_APPRAISE_MODULES) &&
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(ima_appraise & IMA_APPRAISE_ENFORCE))
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return -EACCES; /* INTEGRITY_UNKNOWN */
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#endif
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return 0; /* We rely on module signature checking */
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}
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return process_measurement(file, MAY_EXEC, MODULE_CHECK, 0);
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}
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int ima_fw_from_file(struct file *file, char *buf, size_t size)
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{
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if (!file) {
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if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
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(ima_appraise & IMA_APPRAISE_ENFORCE))
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return -EACCES; /* INTEGRITY_UNKNOWN */
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return 0;
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}
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return process_measurement(file, MAY_EXEC, FIRMWARE_CHECK, 0);
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}
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static int __init init_ima(void)
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{
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int error;
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hash_setup(CONFIG_IMA_DEFAULT_HASH);
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error = ima_init();
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if (!error) {
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ima_initialized = 1;
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ima_update_policy_flag();
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}
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return error;
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}
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late_initcall(init_ima); /* Start IMA after the TPM is available */
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MODULE_DESCRIPTION("Integrity Measurement Architecture");
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MODULE_LICENSE("GPL");
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