// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2008 IBM Corporation
*
* Author: Mimi Zohar <zohar@us.ibm.com>
*
* File: ima_api.c
* Implements must_appraise_or_measure, collect_measurement,
* appraise_measurement, store_measurement and store_template.
*/
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/evm.h>
#include <linux/iversion.h>
#include "ima.h"
/*
* ima_free_template_entry - free an existing template entry
*/
void ima_free_template_entry(struct ima_template_entry *entry)
{
int i;
for (i = 0; i < entry->template_desc->num_fields; i++)
kfree(entry->template_data[i].data);
kfree(entry);
}
/*
* ima_alloc_init_template - create and initialize a new template entry
*/
int ima_alloc_init_template(struct ima_event_data *event_data,
struct ima_template_entry **entry,
struct ima_template_desc *desc)
{
struct ima_template_desc *template_desc;
int i, result = 0;
if (desc)
template_desc = desc;
else
template_desc = ima_template_desc_current();
*entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
sizeof(struct ima_field_data), GFP_NOFS);
if (!*entry)
return -ENOMEM;
(*entry)->template_desc = template_desc;
for (i = 0; i < template_desc->num_fields; i++) {
const struct ima_template_field *field =
template_desc->fields[i];
u32 len;
result = field->field_init(event_data,
&((*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;
}
return 0;
out:
ima_free_template_entry(*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, int pcr)
{
static const char op[] = "add_template_measure";
static 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);
}
entry->pcr = pcr;
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,
struct integrity_iint_cache *iint,
const char *op, const char *cause)
{
struct ima_template_entry *entry;
struct inode *inode = file_inode(file);
struct ima_event_data event_data = { .iint = iint,
.file = file,
.filename = filename,
.violation = cause };
int violation = 1;
int result;
/* can overflow, only indicator */
atomic_long_inc(&ima_htable.violations);
result = ima_alloc_init_template(&event_data, &entry, NULL);
if (result < 0) {
result = -ENOMEM;
goto err_out;
}
result = ima_store_template(entry, violation, inode,
filename, CONFIG_IMA_MEASURE_PCR_IDX);
if (result < 0)
ima_free_template_entry(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
* @cred: pointer to credentials structure to validate
* @secid: secid of the task being validated
* @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
* MAY_APPEND)
* @func: caller identifier
* @pcr: pointer filled in if matched measure policy sets pcr=
* @template_desc: pointer filled in if matched measure policy sets template=
*
* 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 | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
* | KEXEC_CMDLINE
* mask: contains the permission mask
* fsmagic: hex value
*
* Returns IMA_MEASURE, IMA_APPRAISE mask.
*
*/
int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
int mask, enum ima_hooks func, int *pcr,
struct ima_template_desc **template_desc)
{
int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
flags &= ima_policy_flag;
return ima_match_policy(inode, cred, secid, func, mask, flags, pcr,
template_desc);
}
/*
* 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, void *buf, loff_t size,
enum hash_algo algo)
{
const char *audit_cause = "failed";
struct inode *inode = file_inode(file);
const char *filename = file->f_path.dentry->d_name.name;
int result = 0;
int length;
void *tmpbuf;
u64 i_version;
struct {
struct ima_digest_data hdr;
char digest[IMA_MAX_DIGEST_SIZE];
} hash;
if (iint->flags & IMA_COLLECTED)
goto out;
/*
* Dectecting file change is based on i_version. On filesystems
* which do not support i_version, support is limited to an initial
* measurement/appraisal/audit.
*/
i_version = inode_query_iversion(inode);
hash.hdr.algo = algo;
/* Initialize hash digest to 0's in case of failure */
memset(&hash.digest, 0, sizeof(hash.digest));
if (buf)
result = ima_calc_buffer_hash(buf, size, &hash.hdr);
else
result = ima_calc_file_hash(file, &hash.hdr);
if (result && result != -EBADF && result != -EINVAL)
goto out;
length = sizeof(hash.hdr) + hash.hdr.length;
tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
if (!tmpbuf) {
result = -ENOMEM;
goto out;
}
iint->ima_hash = tmpbuf;
memcpy(iint->ima_hash, &hash, length);
iint->version = i_version;
/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
if (!result)
iint->flags |= IMA_COLLECTED;
out:
if (result) {
if (file->f_flags & O_DIRECT)
audit_cause = "failed(directio)";
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
filename, "collect_data", audit_cause,
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, int pcr,
struct ima_template_desc *template_desc)
{
static const char op[] = "add_template_measure";
static const char audit_cause[] = "ENOMEM";
int result = -ENOMEM;
struct inode *inode = file_inode(file);
struct ima_template_entry *entry;
struct ima_event_data event_data = { .iint = iint,
.file = file,
.filename = filename,
.xattr_value = xattr_value,
.xattr_len = xattr_len };
int violation = 0;
if (iint->measured_pcrs & (0x1 << pcr))
return;
result = ima_alloc_init_template(&event_data, &entry, template_desc);
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, pcr);
if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
iint->flags |= IMA_MEASURED;
iint->measured_pcrs |= (0x1 << pcr);
}
if (result < 0)
ima_free_template_entry(entry);
}
void ima_audit_measurement(struct integrity_iint_cache *iint,
const unsigned char *filename)
{
struct audit_buffer *ab;
char *hash;
const char *algo_name = hash_algo_name[iint->ima_hash->algo];
int i;
if (iint->flags & IMA_AUDITED)
return;
hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
if (!hash)
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(audit_context(), GFP_KERNEL,
AUDIT_INTEGRITY_RULE);
if (!ab)
goto out;
audit_log_format(ab, "file=");
audit_log_untrustedstring(ab, filename);
audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);
audit_log_task_info(ab);
audit_log_end(ab);
iint->flags |= IMA_AUDITED;
out:
kfree(hash);
return;
}
/*
* ima_d_path - return a pointer to the full pathname
*
* Attempt to return a pointer to the full pathname for use in the
* IMA measurement list, IMA audit records, and auditing logs.
*
* On failure, return a pointer to a copy of the filename, not dname.
* Returning a pointer to dname, could result in using the pointer
* after the memory has been freed.
*/
const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
{
char *pathname = NULL;
*pathbuf = __getname();
if (*pathbuf) {
pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
if (IS_ERR(pathname)) {
__putname(*pathbuf);
*pathbuf = NULL;
pathname = NULL;
}
}
if (!pathname) {
strlcpy(namebuf, path->dentry->d_name.name, NAME_MAX);
pathname = namebuf;
}
return pathname;
}
