security/integrity/ima/ima_api.c - linux - Git at Google

 /*
  * 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 <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 *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;

 	(*entry)->template_desc = template_desc;
 	for (i = 0; i < template_desc->num_fields; i++) {
 		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, file, filename, NULL, 0,
 					    cause};
 	int violation = 1;
 	int result;

 	/* can overflow, only indicator */
 	atomic_long_inc(&ima_htable.violations);

 	result = ima_alloc_init_template(&event_data, &entry);
 	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=
  *
  * 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
  *	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)
 {
 	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);
 }

 /*
  * 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)
 {
 	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, file, filename, xattr_value,
 					    xattr_len, NULL};
 	int violation = 0;

 	if (iint->measured_pcrs & (0x1 << pcr))
 		return;

 	result = ima_alloc_init_template(&event_data, &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, 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(current->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, current);
 	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;
 }
	/*
	* 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 <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 *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;

	(*entry)->template_desc = template_desc;
	for (i = 0; i < template_desc->num_fields; i++) {
	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, file, filename, NULL, 0,
	cause};
	int violation = 1;
	int result;

	/* can overflow, only indicator */
	atomic_long_inc(&ima_htable.violations);

	result = ima_alloc_init_template(&event_data, &entry);
	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=
	*
	* 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
	* 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)
	{
	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);
	}

	/*
	* 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)
	{
	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, file, filename, xattr_value,
	xattr_len, NULL};
	int violation = 0;

	if (iint->measured_pcrs & (0x1 << pcr))
	return;

	result = ima_alloc_init_template(&event_data, &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, 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(current->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, current);
	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;
	}