369 lines
10 KiB
C
369 lines
10 KiB
C
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/*
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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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/*
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* ima_free_template_entry - free an existing template entry
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*/
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void ima_free_template_entry(struct ima_template_entry *entry)
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{
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int i;
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for (i = 0; i < entry->template_desc->num_fields; i++)
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kfree(entry->template_data[i].data);
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kfree(entry);
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}
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/*
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* ima_alloc_init_template - create and initialize a new template entry
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*/
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int ima_alloc_init_template(struct ima_event_data *event_data,
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struct ima_template_entry **entry)
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{
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struct ima_template_desc *template_desc = ima_template_desc_current();
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int i, result = 0;
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*entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
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sizeof(struct ima_field_data), GFP_NOFS);
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if (!*entry)
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return -ENOMEM;
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(*entry)->template_desc = template_desc;
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for (i = 0; i < template_desc->num_fields; i++) {
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struct ima_template_field *field = template_desc->fields[i];
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u32 len;
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result = field->field_init(event_data,
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&((*entry)->template_data[i]));
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if (result != 0)
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goto out;
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len = (*entry)->template_data[i].len;
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(*entry)->template_data_len += sizeof(len);
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(*entry)->template_data_len += len;
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}
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return 0;
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out:
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ima_free_template_entry(*entry);
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*entry = NULL;
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return result;
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}
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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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const unsigned char *filename, int pcr)
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{
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static const char op[] = "add_template_measure";
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static const char audit_cause[] = "hashing_error";
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char *template_name = entry->template_desc->name;
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int result;
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struct {
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struct ima_digest_data hdr;
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char digest[TPM_DIGEST_SIZE];
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} hash;
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if (!violation) {
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int num_fields = entry->template_desc->num_fields;
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/* this function uses default algo */
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hash.hdr.algo = HASH_ALGO_SHA1;
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result = ima_calc_field_array_hash(&entry->template_data[0],
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entry->template_desc,
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num_fields, &hash.hdr);
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if (result < 0) {
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integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
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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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memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
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}
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entry->pcr = pcr;
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result = ima_add_template_entry(entry, violation, op, inode, filename);
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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 file *file, const unsigned char *filename,
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struct integrity_iint_cache *iint,
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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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struct inode *inode = file_inode(file);
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struct ima_event_data event_data = {iint, file, filename, NULL, 0,
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cause};
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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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result = ima_alloc_init_template(&event_data, &entry);
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if (result < 0) {
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result = -ENOMEM;
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goto err_out;
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}
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result = ima_store_template(entry, violation, inode,
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filename, CONFIG_IMA_MEASURE_PCR_IDX);
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if (result < 0)
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ima_free_template_entry(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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* @func: caller identifier
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* @pcr: pointer filled in if matched measure policy sets pcr=
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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, enum ima_hooks func, int *pcr)
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{
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int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
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flags &= ima_policy_flag;
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return ima_match_policy(inode, func, mask, flags, pcr);
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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, void *buf, loff_t size,
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enum hash_algo algo)
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{
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const char *audit_cause = "failed";
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struct inode *inode = file_inode(file);
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const char *filename = file->f_path.dentry->d_name.name;
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int result = 0;
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int length;
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void *tmpbuf;
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u64 i_version;
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struct {
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struct ima_digest_data hdr;
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char digest[IMA_MAX_DIGEST_SIZE];
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} hash;
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if (iint->flags & IMA_COLLECTED)
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goto out;
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/*
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* Dectecting file change is based on i_version. On filesystems
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* which do not support i_version, support is limited to an initial
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* measurement/appraisal/audit.
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*/
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i_version = file_inode(file)->i_version;
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hash.hdr.algo = algo;
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/* Initialize hash digest to 0's in case of failure */
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memset(&hash.digest, 0, sizeof(hash.digest));
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if (buf)
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result = ima_calc_buffer_hash(buf, size, &hash.hdr);
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else
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result = ima_calc_file_hash(file, &hash.hdr);
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if (result && result != -EBADF && result != -EINVAL)
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goto out;
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length = sizeof(hash.hdr) + hash.hdr.length;
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tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
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if (!tmpbuf) {
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result = -ENOMEM;
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goto out;
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}
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iint->ima_hash = tmpbuf;
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memcpy(iint->ima_hash, &hash, length);
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iint->version = i_version;
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/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
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if (!result)
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iint->flags |= IMA_COLLECTED;
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out:
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if (result) {
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if (file->f_flags & O_DIRECT)
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audit_cause = "failed(directio)";
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integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
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filename, "collect_data", audit_cause,
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result, 0);
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}
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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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struct evm_ima_xattr_data *xattr_value,
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int xattr_len, int pcr)
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{
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static const char op[] = "add_template_measure";
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static 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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struct ima_event_data event_data = {iint, file, filename, xattr_value,
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xattr_len, NULL};
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int violation = 0;
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if (iint->measured_pcrs & (0x1 << pcr))
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return;
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result = ima_alloc_init_template(&event_data, &entry);
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if (result < 0) {
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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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result = ima_store_template(entry, violation, inode, filename, pcr);
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if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
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iint->flags |= IMA_MEASURED;
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iint->measured_pcrs |= (0x1 << pcr);
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}
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if (result < 0)
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ima_free_template_entry(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[(iint->ima_hash->length * 2) + 1];
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const char *algo_name = hash_algo_name[iint->ima_hash->algo];
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char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
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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 < iint->ima_hash->length; i++)
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hex_byte_pack(hash + (i * 2), iint->ima_hash->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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snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
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audit_log_untrustedstring(ab, algo_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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/*
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* ima_d_path - return a pointer to the full pathname
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*
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* Attempt to return a pointer to the full pathname for use in the
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* IMA measurement list, IMA audit records, and auditing logs.
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*
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* On failure, return a pointer to a copy of the filename, not dname.
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* Returning a pointer to dname, could result in using the pointer
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* after the memory has been freed.
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*/
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const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
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{
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char *pathname = NULL;
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*pathbuf = __getname();
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if (*pathbuf) {
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pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
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if (IS_ERR(pathname)) {
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__putname(*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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if (!pathname) {
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strlcpy(namebuf, path->dentry->d_name.name, NAME_MAX);
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pathname = namebuf;
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}
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return pathname;
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}
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