[mirror_ubuntu-zesty-kernel.git] / security / integrity / ima / ima_appraise.c

/*
 * Copyright (C) 2011 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.
 */
#include <linux/module.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/magic.h>
#include <linux/ima.h>
#include <linux/evm.h>

#include "ima.h"

static int __init default_appraise_setup(char *str)
{
	if (strncmp(str, "off", 3) == 0)
		ima_appraise = 0;
	else if (strncmp(str, "fix", 3) == 0)
		ima_appraise = IMA_APPRAISE_FIX;
	return 1;
}

__setup("ima_appraise=", default_appraise_setup);

/*
 * ima_must_appraise - set appraise flag
 *
 * Return 1 to appraise
 */
int ima_must_appraise(struct inode *inode, enum ima_hooks func, int mask)
{
	if (!ima_appraise)
		return 0;

	return ima_match_policy(inode, func, mask, IMA_APPRAISE);
}

static void ima_fix_xattr(struct dentry *dentry,
			  struct integrity_iint_cache *iint)
{
	iint->ima_xattr.type = IMA_XATTR_DIGEST;
	__vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, (u8 *)&iint->ima_xattr,
			      sizeof iint->ima_xattr, 0);
}

/*
 * ima_appraise_measurement - appraise file measurement
 *
 * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
 * Assuming success, compare the xattr hash with the collected measurement.
 *
 * Return 0 on success, error code otherwise
 */
int ima_appraise_measurement(struct integrity_iint_cache *iint,
			     struct file *file, const unsigned char *filename)
{
	struct dentry *dentry = file->f_dentry;
	struct inode *inode = dentry->d_inode;
	struct evm_ima_xattr_data xattr_value;
	enum integrity_status status = INTEGRITY_UNKNOWN;
	const char *op = "appraise_data";
	char *cause = "unknown";
	int rc;

	if (!ima_appraise)
		return 0;
	if (!inode->i_op->getxattr)
		return INTEGRITY_UNKNOWN;

	if (iint->flags & IMA_APPRAISED)
		return iint->ima_status;

	rc = inode->i_op->getxattr(dentry, XATTR_NAME_IMA, (u8 *)&xattr_value,
				   sizeof xattr_value);
	if (rc <= 0) {
		if (rc && rc != -ENODATA)
			goto out;

		cause = "missing-hash";
		status =
		    (inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
		goto out;
	}

	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, (u8 *)&xattr_value,
				 rc, iint);
	if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
		if ((status == INTEGRITY_NOLABEL)
		    || (status == INTEGRITY_NOXATTRS))
			cause = "missing-HMAC";
		else if (status == INTEGRITY_FAIL)
			cause = "invalid-HMAC";
		goto out;
	}

	rc = memcmp(xattr_value.digest, iint->ima_xattr.digest,
		    IMA_DIGEST_SIZE);
	if (rc) {
		status = INTEGRITY_FAIL;
		cause = "invalid-hash";
		print_hex_dump_bytes("security.ima: ", DUMP_PREFIX_NONE,
				     &xattr_value, sizeof xattr_value);
		print_hex_dump_bytes("collected: ", DUMP_PREFIX_NONE,
				     (u8 *)&iint->ima_xattr,
				     sizeof iint->ima_xattr);
		goto out;
	}
	status = INTEGRITY_PASS;
	iint->flags |= IMA_APPRAISED;
out:
	if (status != INTEGRITY_PASS) {
		if (ima_appraise & IMA_APPRAISE_FIX) {
			ima_fix_xattr(dentry, iint);
			status = INTEGRITY_PASS;
		}
		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
				    op, cause, rc, 0);
	}
	iint->ima_status = status;
	return status;
}

/*
 * ima_update_xattr - update 'security.ima' hash value
 */
void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
{
	struct dentry *dentry = file->f_dentry;
	int rc = 0;

	rc = ima_collect_measurement(iint, file);
	if (rc < 0)
		return;
	ima_fix_xattr(dentry, iint);
}

/**
 * ima_inode_post_setattr - reflect file metadata changes
 * @dentry: pointer to the affected dentry
 *
 * Changes to a dentry's metadata might result in needing to appraise.
 *
 * This function is called from notify_change(), which expects the caller
 * to lock the inode's i_mutex.
 */
void ima_inode_post_setattr(struct dentry *dentry)
{
	struct inode *inode = dentry->d_inode;
	struct integrity_iint_cache *iint;
	int must_appraise, rc;

	if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)
	    || !inode->i_op->removexattr)
		return;

	must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
	iint = integrity_iint_find(inode);
	if (iint) {
		if (must_appraise)
			iint->flags |= IMA_APPRAISE;
		else
			iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED);
	}
	if (!must_appraise)
		rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
	return;
}

/*
 * ima_protect_xattr - protect 'security.ima'
 *
 * Ensure that not just anyone can modify or remove 'security.ima'.
 */
static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
			     const void *xattr_value, size_t xattr_value_len)
{
	if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		return 1;
	}
	return 0;
}

static void ima_reset_appraise_flags(struct inode *inode)
{
	struct integrity_iint_cache *iint;

	if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode))
		return;

	iint = integrity_iint_find(inode);
	if (!iint)
		return;

	iint->flags &= ~(IMA_COLLECTED | IMA_APPRAISED | IMA_MEASURED);
	return;
}

int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
		       const void *xattr_value, size_t xattr_value_len)
{
	int result;

	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
				   xattr_value_len);
	if (result == 1) {
		ima_reset_appraise_flags(dentry->d_inode);
		result = 0;
	}
	return result;
}

int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
{
	int result;

	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
	if (result == 1) {
		ima_reset_appraise_flags(dentry->d_inode);
		result = 0;
	}
	return result;
}
Commit	Line	Data
2fe5d6de MZ	1	/*
	2	* Copyright (C) 2011 IBM Corporation
	3	*
	4	* Author:
	5	* Mimi Zohar <zohar@us.ibm.com>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License as published by
	9	* the Free Software Foundation, version 2 of the License.
	10	*/
	11	#include <linux/module.h>
	12	#include <linux/file.h>
	13	#include <linux/fs.h>
	14	#include <linux/xattr.h>
	15	#include <linux/magic.h>
	16	#include <linux/ima.h>
	17	#include <linux/evm.h>
	18
	19	#include "ima.h"
	20
	21	static int __init default_appraise_setup(char *str)
	22	{
	23	if (strncmp(str, "off", 3) == 0)
	24	ima_appraise = 0;
	25	else if (strncmp(str, "fix", 3) == 0)
	26	ima_appraise = IMA_APPRAISE_FIX;
	27	return 1;
	28	}
	29
	30	__setup("ima_appraise=", default_appraise_setup);
	31
	32	/*
	33	* ima_must_appraise - set appraise flag
	34	*
	35	* Return 1 to appraise
	36	*/
	37	int ima_must_appraise(struct inode *inode, enum ima_hooks func, int mask)
	38	{
07f6a794 MZ	39	if (!ima_appraise)
	40	return 0;
	41
	42	return ima_match_policy(inode, func, mask, IMA_APPRAISE);
2fe5d6de MZ	43	}
	44
	45	static void ima_fix_xattr(struct dentry *dentry,
	46	struct integrity_iint_cache *iint)
	47	{
5a44b412 MZ	48	iint->ima_xattr.type = IMA_XATTR_DIGEST;
	49	__vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, (u8 *)&iint->ima_xattr,
	50	sizeof iint->ima_xattr, 0);
2fe5d6de MZ	51	}
	52
	53	/*
	54	* ima_appraise_measurement - appraise file measurement
	55	*
	56	* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
	57	* Assuming success, compare the xattr hash with the collected measurement.
	58	*
	59	* Return 0 on success, error code otherwise
	60	*/
	61	int ima_appraise_measurement(struct integrity_iint_cache *iint,
	62	struct file file, const unsigned char filename)
	63	{
	64	struct dentry *dentry = file->f_dentry;
	65	struct inode *inode = dentry->d_inode;
5a44b412	66	struct evm_ima_xattr_data xattr_value;
2fe5d6de MZ	67	enum integrity_status status = INTEGRITY_UNKNOWN;
	68	const char *op = "appraise_data";
	69	char *cause = "unknown";
	70	int rc;
	71
	72	if (!ima_appraise)
	73	return 0;
	74	if (!inode->i_op->getxattr)
	75	return INTEGRITY_UNKNOWN;
	76
	77	if (iint->flags & IMA_APPRAISED)
	78	return iint->ima_status;
	79
5a44b412 MZ	80	rc = inode->i_op->getxattr(dentry, XATTR_NAME_IMA, (u8 *)&xattr_value,
5a44b412 MZ	81	sizeof xattr_value);
2fe5d6de MZ	82	if (rc <= 0) {
	83	if (rc && rc != -ENODATA)
	84	goto out;
	85
	86	cause = "missing-hash";
	87	status =
	88	(inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
	89	goto out;
	90	}
	91
5a44b412 MZ	92	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, (u8 *)&xattr_value,
5a44b412 MZ	93	rc, iint);
2fe5d6de MZ	94	if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
	95	if ((status == INTEGRITY_NOLABEL)
	96	\|\| (status == INTEGRITY_NOXATTRS))
	97	cause = "missing-HMAC";
	98	else if (status == INTEGRITY_FAIL)
	99	cause = "invalid-HMAC";
	100	goto out;
	101	}
	102
5a44b412 MZ	103	rc = memcmp(xattr_value.digest, iint->ima_xattr.digest,
5a44b412 MZ	104	IMA_DIGEST_SIZE);
2fe5d6de MZ	105	if (rc) {
	106	status = INTEGRITY_FAIL;
	107	cause = "invalid-hash";
	108	print_hex_dump_bytes("security.ima: ", DUMP_PREFIX_NONE,
5a44b412	109	&xattr_value, sizeof xattr_value);
2fe5d6de	110	print_hex_dump_bytes("collected: ", DUMP_PREFIX_NONE,
5a44b412 MZ	111	(u8 *)&iint->ima_xattr,
5a44b412 MZ	112	sizeof iint->ima_xattr);
2fe5d6de MZ	113	goto out;
	114	}
	115	status = INTEGRITY_PASS;
	116	iint->flags \|= IMA_APPRAISED;
	117	out:
	118	if (status != INTEGRITY_PASS) {
	119	if (ima_appraise & IMA_APPRAISE_FIX) {
	120	ima_fix_xattr(dentry, iint);
	121	status = INTEGRITY_PASS;
	122	}
	123	integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
	124	op, cause, rc, 0);
	125	}
	126	iint->ima_status = status;
	127	return status;
	128	}
	129
	130	/*
	131	* ima_update_xattr - update 'security.ima' hash value
	132	*/
	133	void ima_update_xattr(struct integrity_iint_cache iint, struct file file)
	134	{
	135	struct dentry *dentry = file->f_dentry;
	136	int rc = 0;
	137
	138	rc = ima_collect_measurement(iint, file);
	139	if (rc < 0)
	140	return;
	141	ima_fix_xattr(dentry, iint);
	142	}
	143
	144	/**
	145	* ima_inode_post_setattr - reflect file metadata changes
	146	* @dentry: pointer to the affected dentry
	147	*
	148	* Changes to a dentry's metadata might result in needing to appraise.
	149	*
	150	* This function is called from notify_change(), which expects the caller
	151	* to lock the inode's i_mutex.
	152	*/
	153	void ima_inode_post_setattr(struct dentry *dentry)
	154	{
	155	struct inode *inode = dentry->d_inode;
	156	struct integrity_iint_cache *iint;
	157	int must_appraise, rc;
	158
	159	if (!ima_initialized \|\| !ima_appraise \|\| !S_ISREG(inode->i_mode)
	160	\|\| !inode->i_op->removexattr)
	161	return;
	162
	163	must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
	164	iint = integrity_iint_find(inode);
	165	if (iint) {
	166	if (must_appraise)
	167	iint->flags \|= IMA_APPRAISE;
	168	else
	169	iint->flags &= ~(IMA_APPRAISE \| IMA_APPRAISED);
	170	}
	171	if (!must_appraise)
	172	rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
	173	return;
	174	}
42c63330 MZ	175
	176	/*
	177	* ima_protect_xattr - protect 'security.ima'
	178	*
	179	* Ensure that not just anyone can modify or remove 'security.ima'.
	180	*/
	181	static int ima_protect_xattr(struct dentry dentry, const char xattr_name,
	182	const void *xattr_value, size_t xattr_value_len)
	183	{
	184	if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
	185	if (!capable(CAP_SYS_ADMIN))
	186	return -EPERM;
	187	return 1;
	188	}
	189	return 0;
	190	}
	191
	192	static void ima_reset_appraise_flags(struct inode *inode)
	193	{
	194	struct integrity_iint_cache *iint;
	195
	196	if (!ima_initialized \|\| !ima_appraise \|\| !S_ISREG(inode->i_mode))
	197	return;
	198
	199	iint = integrity_iint_find(inode);
	200	if (!iint)
	201	return;
	202
	203	iint->flags &= ~(IMA_COLLECTED \| IMA_APPRAISED \| IMA_MEASURED);
	204	return;
	205	}
	206
	207	int ima_inode_setxattr(struct dentry dentry, const char xattr_name,
	208	const void *xattr_value, size_t xattr_value_len)
	209	{
	210	int result;
	211
	212	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
	213	xattr_value_len);
	214	if (result == 1) {
	215	ima_reset_appraise_flags(dentry->d_inode);
	216	result = 0;
	217	}
	218	return result;
	219	}
	220
	221	int ima_inode_removexattr(struct dentry dentry, const char xattr_name)
	222	{
	223	int result;
	224
	225	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
	226	if (result == 1) {
	227	ima_reset_appraise_flags(dentry->d_inode);
	228	result = 0;
	229	}
	230	return result;
	231	}