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/*
* Copyright (C) 2008 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.
*
* File: ima_api.c
* Implements must_measure, collect_measurement, store_measurement,
* and store_template.
*/
#include <linux/module.h>
#include <linux/slab.h>
#include "ima.h"
static const char *IMA_TEMPLATE_NAME = "ima";
/*
* ima_store_template - store ima template measurements
*
* Calculate the hash of a template entry, add the template entry
* to an ordered list of measurement entries maintained inside the kernel,
* and also update the aggregate integrity value (maintained inside the
* configured TPM PCR) over the hashes of the current list of measurement
* entries.
*
* Applications retrieve the current kernel-held measurement list through
* the securityfs entries in /sys/kernel/security/ima. The signed aggregate
* TPM PCR (called quote) can be retrieved using a TPM user space library
* and is used to validate the measurement list.
*
* Returns 0 on success, error code otherwise
*/
int ima_store_template(struct ima_template_entry *entry,
int violation, struct inode *inode)
{
const char *op = "add_template_measure";
const char *audit_cause = "hashing_error";
int result;
memset(entry->digest, 0, sizeof(entry->digest));
entry->template_name = IMA_TEMPLATE_NAME;
entry->template_len = sizeof(entry->template);
if (!violation) {
result = ima_calc_template_hash(entry->template_len,
&entry->template,
entry->digest);
if (result < 0) {
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
entry->template_name, op,
audit_cause, result, 0);
return result;
}
}
result = ima_add_template_entry(entry, violation, op, inode);
return result;
}
/*
* ima_add_violation - add violation to measurement list.
*
* Violations are flagged in the measurement list with zero hash values.
* By extending the PCR with 0xFF's instead of with zeroes, the PCR
* value is invalidated.
*/
void ima_add_violation(struct inode *inode, const unsigned char *filename,
const char *op, const char *cause)
{
struct ima_template_entry *entry;
int violation = 1;
int result;
/* can overflow, only indicator */
atomic_long_inc(&ima_htable.violations);
entry = kmalloc(sizeof(*entry), GFP_KERNEL);
if (!entry) {
result = -ENOMEM;
goto err_out;
}
memset(&entry->template, 0, sizeof(entry->template));
strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
result = ima_store_template(entry, violation, inode);
if (result < 0)
kfree(entry);
err_out:
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
op, cause, result, 0);
}
/**
* ima_must_measure - measure decision based on policy.
* @inode: pointer to inode to measure
* @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
* @function: calling function (FILE_CHECK, BPRM_CHECK, FILE_MMAP)
*
* The policy is defined in terms of keypairs:
* subj=, obj=, type=, func=, mask=, fsmagic=
* subj,obj, and type: are LSM specific.
* func: FILE_CHECK | BPRM_CHECK | FILE_MMAP
* mask: contains the permission mask
* fsmagic: hex value
*
* Return 0 to measure. For matching a DONT_MEASURE policy, no policy,
* or other error, return an error code.
*/
int ima_must_measure(struct inode *inode, int mask, int function)
{
int must_measure;
must_measure = ima_match_policy(inode, function, mask);
return must_measure ? 0 : -EACCES;
}
/*
* ima_collect_measurement - collect file measurement
*
* Calculate the file hash, if it doesn't already exist,
* storing the measurement and i_version in the iint.
*
* Must be called with iint->mutex held.
*
* Return 0 on success, error code otherwise
*/
int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file)
{
int result = -EEXIST;
if (!(iint->flags & IMA_MEASURED)) {
u64 i_version = file->f_dentry->d_inode->i_version;
memset(iint->digest, 0, IMA_DIGEST_SIZE);
result = ima_calc_hash(file, iint->digest);
if (!result)
iint->version = i_version;
}
return result;
}
/*
* ima_store_measurement - store file measurement
*
* Create an "ima" template and then store the template by calling
* ima_store_template.
*
* We only get here if the inode has not already been measured,
* but the measurement could already exist:
* - multiple copies of the same file on either the same or
* different filesystems.
* - the inode was previously flushed as well as the iint info,
* containing the hashing info.
*
* Must be called with iint->mutex held.
*/
void ima_store_measurement(struct ima_iint_cache *iint, struct file *file,
const unsigned char *filename)
{
const char *op = "add_template_measure";
const char *audit_cause = "ENOMEM";
int result = -ENOMEM;
struct inode *inode = file->f_dentry->d_inode;
struct ima_template_entry *entry;
int violation = 0;
entry = kmalloc(sizeof(*entry), GFP_KERNEL);
if (!entry) {
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
op, audit_cause, result, 0);
return;
}
memset(&entry->template, 0, sizeof(entry->template));
memcpy(entry->template.digest, iint->digest, IMA_DIGEST_SIZE);
strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
result = ima_store_template(entry, violation, inode);
if (!result || result == -EEXIST)
iint->flags |= IMA_MEASURED;
if (result < 0)
kfree(entry);
}
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