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linux-next/security/integrity/ima/ima_api.c
Roberto Sassu b6f8f16f41 ima: do not include field length in template digest calc for ima template
To maintain compatibility with userspace tools, the field length must not
be included in the template digest calculation for the 'ima' template.

Fixes commit: a71dc65 ima: switch to new template management mechanism

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
2013-11-25 07:26:28 -05:00

324 lines
9.0 KiB
C

/*
* 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_appraise_or_measure, collect_measurement,
* appraise_measurement, store_measurement and store_template.
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/evm.h>
#include <crypto/hash_info.h>
#include "ima.h"
/*
* ima_alloc_init_template - create and initialize a new template entry
*/
int ima_alloc_init_template(struct integrity_iint_cache *iint,
struct file *file, const unsigned char *filename,
struct evm_ima_xattr_data *xattr_value,
int xattr_len, struct ima_template_entry **entry)
{
struct ima_template_desc *template_desc = ima_template_desc_current();
int i, result = 0;
*entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
sizeof(struct ima_field_data), GFP_NOFS);
if (!*entry)
return -ENOMEM;
for (i = 0; i < template_desc->num_fields; i++) {
struct ima_template_field *field = template_desc->fields[i];
u32 len;
result = field->field_init(iint, file, filename,
xattr_value, xattr_len,
&((*entry)->template_data[i]));
if (result != 0)
goto out;
len = (*entry)->template_data[i].len;
(*entry)->template_data_len += sizeof(len);
(*entry)->template_data_len += len;
}
(*entry)->template_desc = template_desc;
return 0;
out:
kfree(*entry);
*entry = NULL;
return result;
}
/*
* 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 unsigned char *filename)
{
const char *op = "add_template_measure";
const char *audit_cause = "hashing_error";
char *template_name = entry->template_desc->name;
int result;
struct {
struct ima_digest_data hdr;
char digest[TPM_DIGEST_SIZE];
} hash;
if (!violation) {
int num_fields = entry->template_desc->num_fields;
/* this function uses default algo */
hash.hdr.algo = HASH_ALGO_SHA1;
result = ima_calc_field_array_hash(&entry->template_data[0],
entry->template_desc,
num_fields, &hash.hdr);
if (result < 0) {
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
template_name, op,
audit_cause, result, 0);
return result;
}
memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
}
result = ima_add_template_entry(entry, violation, op, inode, filename);
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 file *file, const unsigned char *filename,
const char *op, const char *cause)
{
struct ima_template_entry *entry;
struct inode *inode = file->f_dentry->d_inode;
int violation = 1;
int result;
/* can overflow, only indicator */
atomic_long_inc(&ima_htable.violations);
result = ima_alloc_init_template(NULL, file, filename,
NULL, 0, &entry);
if (result < 0) {
result = -ENOMEM;
goto err_out;
}
result = ima_store_template(entry, violation, inode, filename);
if (result < 0)
kfree(entry);
err_out:
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
op, cause, result, 0);
}
/**
* ima_get_action - appraise & 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, MMAP_CHECK, MODULE_CHECK)
*
* 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 | MMAP_CHECK | MODULE_CHECK
* mask: contains the permission mask
* fsmagic: hex value
*
* Returns IMA_MEASURE, IMA_APPRAISE mask.
*
*/
int ima_get_action(struct inode *inode, int mask, int function)
{
int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
if (!ima_appraise)
flags &= ~IMA_APPRAISE;
return ima_match_policy(inode, function, mask, flags);
}
int ima_must_measure(struct inode *inode, int mask, int function)
{
return ima_match_policy(inode, function, mask, IMA_MEASURE);
}
/*
* 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 integrity_iint_cache *iint,
struct file *file,
struct evm_ima_xattr_data **xattr_value,
int *xattr_len)
{
struct inode *inode = file_inode(file);
const char *filename = file->f_dentry->d_name.name;
int result = 0;
struct {
struct ima_digest_data hdr;
char digest[IMA_MAX_DIGEST_SIZE];
} hash;
if (xattr_value)
*xattr_len = ima_read_xattr(file->f_dentry, xattr_value);
if (!(iint->flags & IMA_COLLECTED)) {
u64 i_version = file_inode(file)->i_version;
/* use default hash algorithm */
hash.hdr.algo = ima_hash_algo;
if (xattr_value)
ima_get_hash_algo(*xattr_value, *xattr_len, &hash.hdr);
result = ima_calc_file_hash(file, &hash.hdr);
if (!result) {
int length = sizeof(hash.hdr) + hash.hdr.length;
void *tmpbuf = krealloc(iint->ima_hash, length,
GFP_NOFS);
if (tmpbuf) {
iint->ima_hash = tmpbuf;
memcpy(iint->ima_hash, &hash, length);
iint->version = i_version;
iint->flags |= IMA_COLLECTED;
} else
result = -ENOMEM;
}
}
if (result)
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
filename, "collect_data", "failed",
result, 0);
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 integrity_iint_cache *iint,
struct file *file, const unsigned char *filename,
struct evm_ima_xattr_data *xattr_value,
int xattr_len)
{
const char *op = "add_template_measure";
const char *audit_cause = "ENOMEM";
int result = -ENOMEM;
struct inode *inode = file_inode(file);
struct ima_template_entry *entry;
int violation = 0;
if (iint->flags & IMA_MEASURED)
return;
result = ima_alloc_init_template(iint, file, filename,
xattr_value, xattr_len, &entry);
if (result < 0) {
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
op, audit_cause, result, 0);
return;
}
result = ima_store_template(entry, violation, inode, filename);
if (!result || result == -EEXIST)
iint->flags |= IMA_MEASURED;
if (result < 0)
kfree(entry);
}
void ima_audit_measurement(struct integrity_iint_cache *iint,
const unsigned char *filename)
{
struct audit_buffer *ab;
char hash[(iint->ima_hash->length * 2) + 1];
const char *algo_name = hash_algo_name[iint->ima_hash->algo];
char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
int i;
if (iint->flags & IMA_AUDITED)
return;
for (i = 0; i < iint->ima_hash->length; i++)
hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
hash[i * 2] = '\0';
ab = audit_log_start(current->audit_context, GFP_KERNEL,
AUDIT_INTEGRITY_RULE);
if (!ab)
return;
audit_log_format(ab, "file=");
audit_log_untrustedstring(ab, filename);
audit_log_format(ab, " hash=");
snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
audit_log_untrustedstring(ab, algo_hash);
audit_log_task_info(ab, current);
audit_log_end(ab);
iint->flags |= IMA_AUDITED;
}
const char *ima_d_path(struct path *path, char **pathbuf)
{
char *pathname = NULL;
/* We will allow 11 spaces for ' (deleted)' to be appended */
*pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
if (*pathbuf) {
pathname = d_path(path, *pathbuf, PATH_MAX + 11);
if (IS_ERR(pathname)) {
kfree(*pathbuf);
*pathbuf = NULL;
pathname = NULL;
}
}
return pathname;
}