mirror of https://gitee.com/openkylin/linux.git
257 lines
7.1 KiB
C
257 lines
7.1 KiB
C
/*
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* Copyright (C) 2008 IBM Corporation
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*
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* Author: 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_api.c
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* Implements must_appraise_or_measure, collect_measurement,
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* appraise_measurement, store_measurement and store_template.
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*/
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#include <linux/module.h>
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#include <linux/slab.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/evm.h>
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#include "ima.h"
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static const char *IMA_TEMPLATE_NAME = "ima";
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/*
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* ima_store_template - store ima template measurements
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*
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* Calculate the hash of a template entry, add the template entry
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* to an ordered list of measurement entries maintained inside the kernel,
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* and also update the aggregate integrity value (maintained inside the
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* configured TPM PCR) over the hashes of the current list of measurement
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* entries.
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*
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* Applications retrieve the current kernel-held measurement list through
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* the securityfs entries in /sys/kernel/security/ima. The signed aggregate
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* TPM PCR (called quote) can be retrieved using a TPM user space library
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* and is used to validate the measurement list.
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*
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* Returns 0 on success, error code otherwise
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*/
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int ima_store_template(struct ima_template_entry *entry,
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int violation, struct inode *inode)
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{
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const char *op = "add_template_measure";
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const char *audit_cause = "hashing_error";
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int result;
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memset(entry->digest, 0, sizeof(entry->digest));
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entry->template_name = IMA_TEMPLATE_NAME;
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entry->template_len = sizeof(entry->template);
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if (!violation) {
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result = ima_calc_buffer_hash(&entry->template,
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entry->template_len,
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entry->digest);
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if (result < 0) {
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integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
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entry->template_name, op,
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audit_cause, result, 0);
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return result;
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}
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}
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result = ima_add_template_entry(entry, violation, op, inode);
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return result;
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}
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/*
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* ima_add_violation - add violation to measurement list.
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*
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* Violations are flagged in the measurement list with zero hash values.
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* By extending the PCR with 0xFF's instead of with zeroes, the PCR
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* value is invalidated.
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*/
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void ima_add_violation(struct inode *inode, const unsigned char *filename,
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const char *op, const char *cause)
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{
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struct ima_template_entry *entry;
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int violation = 1;
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int result;
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/* can overflow, only indicator */
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atomic_long_inc(&ima_htable.violations);
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entry = kmalloc(sizeof(*entry), GFP_KERNEL);
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if (!entry) {
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result = -ENOMEM;
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goto err_out;
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}
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memset(&entry->template, 0, sizeof(entry->template));
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strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
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result = ima_store_template(entry, violation, inode);
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if (result < 0)
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kfree(entry);
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err_out:
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integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
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op, cause, result, 0);
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}
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/**
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* ima_get_action - appraise & measure decision based on policy.
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* @inode: pointer to inode to measure
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* @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
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* @function: calling function (FILE_CHECK, BPRM_CHECK, MMAP_CHECK, MODULE_CHECK)
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*
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* The policy is defined in terms of keypairs:
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* subj=, obj=, type=, func=, mask=, fsmagic=
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* subj,obj, and type: are LSM specific.
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* func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK
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* mask: contains the permission mask
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* fsmagic: hex value
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*
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* Returns IMA_MEASURE, IMA_APPRAISE mask.
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*
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*/
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int ima_get_action(struct inode *inode, int mask, int function)
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{
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int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
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if (!ima_appraise)
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flags &= ~IMA_APPRAISE;
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return ima_match_policy(inode, function, mask, flags);
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}
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int ima_must_measure(struct inode *inode, int mask, int function)
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{
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return ima_match_policy(inode, function, mask, IMA_MEASURE);
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}
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/*
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* ima_collect_measurement - collect file measurement
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*
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* Calculate the file hash, if it doesn't already exist,
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* storing the measurement and i_version in the iint.
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*
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* Must be called with iint->mutex held.
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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_collect_measurement(struct integrity_iint_cache *iint,
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struct file *file)
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{
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struct inode *inode = file_inode(file);
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const char *filename = file->f_dentry->d_name.name;
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int result = 0;
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if (!(iint->flags & IMA_COLLECTED)) {
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u64 i_version = file_inode(file)->i_version;
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iint->ima_xattr.type = IMA_XATTR_DIGEST;
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result = ima_calc_file_hash(file, iint->ima_xattr.digest);
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if (!result) {
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iint->version = i_version;
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iint->flags |= IMA_COLLECTED;
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}
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}
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if (result)
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integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
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filename, "collect_data", "failed",
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result, 0);
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return result;
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}
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/*
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* ima_store_measurement - store file measurement
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*
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* Create an "ima" template and then store the template by calling
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* ima_store_template.
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*
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* We only get here if the inode has not already been measured,
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* but the measurement could already exist:
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* - multiple copies of the same file on either the same or
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* different filesystems.
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* - the inode was previously flushed as well as the iint info,
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* containing the hashing info.
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*
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* Must be called with iint->mutex held.
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*/
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void ima_store_measurement(struct integrity_iint_cache *iint,
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struct file *file, const unsigned char *filename)
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{
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const char *op = "add_template_measure";
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const char *audit_cause = "ENOMEM";
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int result = -ENOMEM;
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struct inode *inode = file_inode(file);
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struct ima_template_entry *entry;
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int violation = 0;
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if (iint->flags & IMA_MEASURED)
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return;
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entry = kmalloc(sizeof(*entry), GFP_KERNEL);
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if (!entry) {
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integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
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op, audit_cause, result, 0);
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return;
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}
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memset(&entry->template, 0, sizeof(entry->template));
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memcpy(entry->template.digest, iint->ima_xattr.digest, IMA_DIGEST_SIZE);
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strcpy(entry->template.file_name,
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(strlen(filename) > IMA_EVENT_NAME_LEN_MAX) ?
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file->f_dentry->d_name.name : filename);
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result = ima_store_template(entry, violation, inode);
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if (!result || result == -EEXIST)
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iint->flags |= IMA_MEASURED;
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if (result < 0)
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kfree(entry);
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}
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void ima_audit_measurement(struct integrity_iint_cache *iint,
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const unsigned char *filename)
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{
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struct audit_buffer *ab;
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char hash[(IMA_DIGEST_SIZE * 2) + 1];
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int i;
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if (iint->flags & IMA_AUDITED)
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return;
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for (i = 0; i < IMA_DIGEST_SIZE; i++)
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hex_byte_pack(hash + (i * 2), iint->ima_xattr.digest[i]);
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hash[i * 2] = '\0';
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ab = audit_log_start(current->audit_context, GFP_KERNEL,
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AUDIT_INTEGRITY_RULE);
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if (!ab)
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return;
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audit_log_format(ab, "file=");
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audit_log_untrustedstring(ab, filename);
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audit_log_format(ab, " hash=");
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audit_log_untrustedstring(ab, hash);
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audit_log_task_info(ab, current);
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audit_log_end(ab);
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iint->flags |= IMA_AUDITED;
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}
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const char *ima_d_path(struct path *path, char **pathbuf)
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{
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char *pathname = NULL;
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/* We will allow 11 spaces for ' (deleted)' to be appended */
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*pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
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if (*pathbuf) {
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pathname = d_path(path, *pathbuf, PATH_MAX + 11);
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if (IS_ERR(pathname)) {
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kfree(*pathbuf);
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*pathbuf = NULL;
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pathname = NULL;
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}
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}
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return pathname;
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}
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