[deliverable/linux.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 = NULL;
	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 = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)&xattr_value,
				0, GFP_NOFS);
	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, 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;
	}

	switch (xattr_value->type) {
	case IMA_XATTR_DIGEST:
		rc = memcmp(xattr_value->digest, iint->ima_xattr.digest,
			    IMA_DIGEST_SIZE);
		if (rc) {
			cause = "invalid-hash";
			status = INTEGRITY_FAIL;
			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);
			break;
		}
		status = INTEGRITY_PASS;
		break;
	case EVM_IMA_XATTR_DIGSIG:
		iint->flags |= IMA_DIGSIG;
		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
					     xattr_value->digest, rc - 1,
					     iint->ima_xattr.digest,
					     IMA_DIGEST_SIZE);
		if (rc == -EOPNOTSUPP) {
			status = INTEGRITY_UNKNOWN;
		} else if (rc) {
			cause = "invalid-signature";
			status = INTEGRITY_FAIL;
		} else {
			status = INTEGRITY_PASS;
		}
		break;
	default:
		status = INTEGRITY_UNKNOWN;
		cause = "unknown-ima-data";
		break;
	}

out:
	if (status != INTEGRITY_PASS) {
		if ((ima_appraise & IMA_APPRAISE_FIX) &&
		    (!xattr_value ||
		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
			ima_fix_xattr(dentry, iint);
			status = INTEGRITY_PASS;
		}
		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
				    op, cause, rc, 0);
	} else {
		iint->flags |= IMA_APPRAISED;
	}
	iint->ima_status = status;
	kfree(xattr_value);
	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;

	/* do not collect and update hash for digital signatures */
	if (iint->flags & IMA_DIGSIG)
		return;

	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;
8606404f	66	struct evm_ima_xattr_data *xattr_value = NULL;
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
8606404f DK	80	rc = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)&xattr_value,
8606404f DK	81	0, GFP_NOFS);
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
8606404f	92	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
2fe5d6de MZ	93	if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
	94	if ((status == INTEGRITY_NOLABEL)
	95	\|\| (status == INTEGRITY_NOXATTRS))
	96	cause = "missing-HMAC";
	97	else if (status == INTEGRITY_FAIL)
	98	cause = "invalid-HMAC";
	99	goto out;
	100	}
	101
8606404f DK	102	switch (xattr_value->type) {
	103	case IMA_XATTR_DIGEST:
	104	rc = memcmp(xattr_value->digest, iint->ima_xattr.digest,
	105	IMA_DIGEST_SIZE);
	106	if (rc) {
	107	cause = "invalid-hash";
	108	status = INTEGRITY_FAIL;
	109	print_hex_dump_bytes("security.ima: ", DUMP_PREFIX_NONE,
	110	xattr_value, sizeof(*xattr_value));
	111	print_hex_dump_bytes("collected: ", DUMP_PREFIX_NONE,
	112	(u8 *)&iint->ima_xattr,
	113	sizeof iint->ima_xattr);
	114	break;
	115	}
	116	status = INTEGRITY_PASS;
	117	break;
	118	case EVM_IMA_XATTR_DIGSIG:
	119	iint->flags \|= IMA_DIGSIG;
	120	rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
	121	xattr_value->digest, rc - 1,
	122	iint->ima_xattr.digest,
	123	IMA_DIGEST_SIZE);
	124	if (rc == -EOPNOTSUPP) {
	125	status = INTEGRITY_UNKNOWN;
	126	} else if (rc) {
	127	cause = "invalid-signature";
	128	status = INTEGRITY_FAIL;
	129	} else {
	130	status = INTEGRITY_PASS;
	131	}
	132	break;
	133	default:
	134	status = INTEGRITY_UNKNOWN;
	135	cause = "unknown-ima-data";
	136	break;
2fe5d6de	137	}
8606404f	138
2fe5d6de MZ	139	out:
2fe5d6de MZ	140	if (status != INTEGRITY_PASS) {
8606404f DK	141	if ((ima_appraise & IMA_APPRAISE_FIX) &&
	142	(!xattr_value \|\|
	143	xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
2fe5d6de MZ	144	ima_fix_xattr(dentry, iint);
	145	status = INTEGRITY_PASS;
	146	}
	147	integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
	148	op, cause, rc, 0);
8606404f DK	149	} else {
8606404f DK	150	iint->flags \|= IMA_APPRAISED;
2fe5d6de MZ	151	}
2fe5d6de MZ	152	iint->ima_status = status;
8606404f	153	kfree(xattr_value);
2fe5d6de MZ	154	return status;
	155	}
	156
	157	/*
	158	* ima_update_xattr - update 'security.ima' hash value
	159	*/
	160	void ima_update_xattr(struct integrity_iint_cache iint, struct file file)
	161	{
	162	struct dentry *dentry = file->f_dentry;
	163	int rc = 0;
	164
8606404f DK	165	/* do not collect and update hash for digital signatures */
	166	if (iint->flags & IMA_DIGSIG)
	167	return;
	168
2fe5d6de MZ	169	rc = ima_collect_measurement(iint, file);
	170	if (rc < 0)
	171	return;
8606404f	172
2fe5d6de MZ	173	ima_fix_xattr(dentry, iint);
	174	}
	175
	176	/**
	177	* ima_inode_post_setattr - reflect file metadata changes
	178	* @dentry: pointer to the affected dentry
	179	*
	180	* Changes to a dentry's metadata might result in needing to appraise.
	181	*
	182	* This function is called from notify_change(), which expects the caller
	183	* to lock the inode's i_mutex.
	184	*/
	185	void ima_inode_post_setattr(struct dentry *dentry)
	186	{
	187	struct inode *inode = dentry->d_inode;
	188	struct integrity_iint_cache *iint;
	189	int must_appraise, rc;
	190
	191	if (!ima_initialized \|\| !ima_appraise \|\| !S_ISREG(inode->i_mode)
	192	\|\| !inode->i_op->removexattr)
	193	return;
	194
	195	must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
	196	iint = integrity_iint_find(inode);
	197	if (iint) {
	198	if (must_appraise)
	199	iint->flags \|= IMA_APPRAISE;
	200	else
	201	iint->flags &= ~(IMA_APPRAISE \| IMA_APPRAISED);
	202	}
	203	if (!must_appraise)
	204	rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
	205	return;
	206	}
42c63330 MZ	207
	208	/*
	209	* ima_protect_xattr - protect 'security.ima'
	210	*
	211	* Ensure that not just anyone can modify or remove 'security.ima'.
	212	*/
	213	static int ima_protect_xattr(struct dentry dentry, const char xattr_name,
	214	const void *xattr_value, size_t xattr_value_len)
	215	{
	216	if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
	217	if (!capable(CAP_SYS_ADMIN))
	218	return -EPERM;
	219	return 1;
	220	}
	221	return 0;
	222	}
	223
	224	static void ima_reset_appraise_flags(struct inode *inode)
	225	{
	226	struct integrity_iint_cache *iint;
	227
	228	if (!ima_initialized \|\| !ima_appraise \|\| !S_ISREG(inode->i_mode))
	229	return;
	230
	231	iint = integrity_iint_find(inode);
	232	if (!iint)
	233	return;
	234
	235	iint->flags &= ~(IMA_COLLECTED \| IMA_APPRAISED \| IMA_MEASURED);
	236	return;
	237	}
	238
	239	int ima_inode_setxattr(struct dentry dentry, const char xattr_name,
	240	const void *xattr_value, size_t xattr_value_len)
	241	{
	242	int result;
	243
	244	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
	245	xattr_value_len);
	246	if (result == 1) {
	247	ima_reset_appraise_flags(dentry->d_inode);
	248	result = 0;
	249	}
	250	return result;
	251	}
	252
	253	int ima_inode_removexattr(struct dentry dentry, const char xattr_name)
	254	{
	255	int result;
	256
	257	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
	258	if (result == 1) {
	259	ima_reset_appraise_flags(dentry->d_inode);
	260	result = 0;
	261	}
	262	return result;
	263	}