[mirror_ubuntu-bionic-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, int mask, enum ima_hooks func)
{
	if (!ima_appraise)
		return 0;

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

static int ima_fix_xattr(struct dentry *dentry,
			 struct integrity_iint_cache *iint)
{
	iint->ima_hash.type = IMA_XATTR_DIGEST;
	return __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
				     &iint->ima_hash.type,
				     1 + iint->ima_hash.length, 0);
}

/* Return specific func appraised cached result */
enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
					   int func)
{
	switch (func) {
	case MMAP_CHECK:
		return iint->ima_mmap_status;
	case BPRM_CHECK:
		return iint->ima_bprm_status;
	case MODULE_CHECK:
		return iint->ima_module_status;
	case FILE_CHECK:
	default:
		return iint->ima_file_status;
	}
}

static void ima_set_cache_status(struct integrity_iint_cache *iint,
				 int func, enum integrity_status status)
{
	switch (func) {
	case MMAP_CHECK:
		iint->ima_mmap_status = status;
		break;
	case BPRM_CHECK:
		iint->ima_bprm_status = status;
		break;
	case MODULE_CHECK:
		iint->ima_module_status = status;
		break;
	case FILE_CHECK:
	default:
		iint->ima_file_status = status;
		break;
	}
}

static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
{
	switch (func) {
	case MMAP_CHECK:
		iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
		break;
	case BPRM_CHECK:
		iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
		break;
	case MODULE_CHECK:
		iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED);
		break;
	case FILE_CHECK:
	default:
		iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
		break;
	}
}

void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
		       struct ima_digest_data *hash)
{
	struct signature_v2_hdr *sig;

	if (!xattr_value || xattr_len < 0 || xattr_len <= 1 + sizeof(*sig))
		return;

	sig = (typeof(sig)) xattr_value->digest;

	if (xattr_value->type != EVM_IMA_XATTR_DIGSIG || sig->version != 2)
		return;

	hash->algo = sig->hash_algo;
}

int ima_read_xattr(struct dentry *dentry,
		   struct evm_ima_xattr_data **xattr_value)
{
	struct inode *inode = dentry->d_inode;

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

	return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
				  0, GFP_NOFS);
}

/*
 * 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(int func, struct integrity_iint_cache *iint,
			     struct file *file, const unsigned char *filename,
			     struct evm_ima_xattr_data *xattr_value,
			     int xattr_len)
{
	struct dentry *dentry = file->f_dentry;
	struct inode *inode = dentry->d_inode;
	enum integrity_status status = INTEGRITY_UNKNOWN;
	const char *op = "appraise_data";
	char *cause = "unknown";
	int rc = xattr_len;

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

	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:
		if (iint->flags & IMA_DIGSIG_REQUIRED) {
			cause = "IMA signature required";
			status = INTEGRITY_FAIL;
			break;
		}
		if (xattr_len - 1 >= iint->ima_hash.length)
			/* xattr length may be longer. md5 hash in previous
			   version occupied 20 bytes in xattr, instead of 16
			 */
			rc = memcmp(xattr_value->digest,
				    iint->ima_hash.digest,
				    iint->ima_hash.length);
		else
			rc = -EINVAL;
		if (rc) {
			cause = "invalid-hash";
			status = INTEGRITY_FAIL;
			break;
		}
		status = INTEGRITY_PASS;
		break;
	case EVM_IMA_XATTR_DIGSIG:
		iint->flags |= IMA_DIGSIG;
		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
					     (const char *)xattr_value, rc,
					     iint->ima_hash.digest,
					     iint->ima_hash.length);
		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)) {
			if (!ima_fix_xattr(dentry, iint))
				status = INTEGRITY_PASS;
		}
		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
				    op, cause, rc, 0);
	} else {
		ima_cache_flags(iint, func);
	}
	ima_set_cache_status(iint, func, 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;

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

	rc = ima_collect_measurement(iint, file, NULL, NULL);
	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) {
		iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
				 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
				 IMA_ACTION_FLAGS);
		if (must_appraise)
			iint->flags |= IMA_APPRAISE;
	}
	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_DONE_MASK;
	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	*/
d26e1936	37	int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
2fe5d6de	38	{
07f6a794 MZ	39	if (!ima_appraise)
	40	return 0;
	41
	42	return ima_match_policy(inode, func, mask, IMA_APPRAISE);
2fe5d6de MZ	43	}
2fe5d6de MZ	44
def3e8b9	45	static int ima_fix_xattr(struct dentry *dentry,
c7c8bb23	46	struct integrity_iint_cache *iint)
2fe5d6de	47	{
c7c8bb23	48	iint->ima_hash.type = IMA_XATTR_DIGEST;
def3e8b9	49	return __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
c7c8bb23 DK	50	&iint->ima_hash.type,
c7c8bb23 DK	51	1 + iint->ima_hash.length, 0);
2fe5d6de MZ	52	}
2fe5d6de MZ	53
d79d72e0 MZ	54	/* Return specific func appraised cached result */
	55	enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
	56	int func)
	57	{
089bc8e9	58	switch (func) {
d79d72e0 MZ	59	case MMAP_CHECK:
	60	return iint->ima_mmap_status;
	61	case BPRM_CHECK:
	62	return iint->ima_bprm_status;
	63	case MODULE_CHECK:
	64	return iint->ima_module_status;
	65	case FILE_CHECK:
	66	default:
	67	return iint->ima_file_status;
	68	}
	69	}
	70
	71	static void ima_set_cache_status(struct integrity_iint_cache *iint,
	72	int func, enum integrity_status status)
	73	{
089bc8e9	74	switch (func) {
d79d72e0 MZ	75	case MMAP_CHECK:
	76	iint->ima_mmap_status = status;
	77	break;
	78	case BPRM_CHECK:
	79	iint->ima_bprm_status = status;
	80	break;
	81	case MODULE_CHECK:
	82	iint->ima_module_status = status;
	83	break;
	84	case FILE_CHECK:
	85	default:
	86	iint->ima_file_status = status;
	87	break;
	88	}
	89	}
	90
	91	static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
	92	{
089bc8e9	93	switch (func) {
d79d72e0 MZ	94	case MMAP_CHECK:
	95	iint->flags \|= (IMA_MMAP_APPRAISED \| IMA_APPRAISED);
	96	break;
	97	case BPRM_CHECK:
	98	iint->flags \|= (IMA_BPRM_APPRAISED \| IMA_APPRAISED);
	99	break;
	100	case MODULE_CHECK:
	101	iint->flags \|= (IMA_MODULE_APPRAISED \| IMA_APPRAISED);
	102	break;
	103	case FILE_CHECK:
	104	default:
	105	iint->flags \|= (IMA_FILE_APPRAISED \| IMA_APPRAISED);
	106	break;
	107	}
	108	}
	109
d3634d0f DK	110	void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
	111	struct ima_digest_data *hash)
	112	{
	113	struct signature_v2_hdr *sig;
	114
	115	if (!xattr_value \|\| xattr_len < 0 \|\| xattr_len <= 1 + sizeof(*sig))
	116	return;
	117
	118	sig = (typeof(sig)) xattr_value->digest;
	119
	120	if (xattr_value->type != EVM_IMA_XATTR_DIGSIG \|\| sig->version != 2)
	121	return;
	122
	123	hash->algo = sig->hash_algo;
	124	}
	125
	126	int ima_read_xattr(struct dentry *dentry,
	127	struct evm_ima_xattr_data **xattr_value)
	128	{
	129	struct inode *inode = dentry->d_inode;
	130
	131	if (!inode->i_op->getxattr)
	132	return 0;
	133
	134	return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
	135	0, GFP_NOFS);
	136	}
	137
2fe5d6de MZ	138	/*
	139	* ima_appraise_measurement - appraise file measurement
	140	*
	141	* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
	142	* Assuming success, compare the xattr hash with the collected measurement.
	143	*
	144	* Return 0 on success, error code otherwise
	145	*/
d79d72e0	146	int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
d3634d0f DK	147	struct file file, const unsigned char filename,
	148	struct evm_ima_xattr_data *xattr_value,
	149	int xattr_len)
2fe5d6de MZ	150	{
	151	struct dentry *dentry = file->f_dentry;
	152	struct inode *inode = dentry->d_inode;
2fe5d6de MZ	153	enum integrity_status status = INTEGRITY_UNKNOWN;
	154	const char *op = "appraise_data";
	155	char *cause = "unknown";
d3634d0f	156	int rc = xattr_len;
2fe5d6de MZ	157
	158	if (!ima_appraise)
	159	return 0;
	160	if (!inode->i_op->getxattr)
	161	return INTEGRITY_UNKNOWN;
	162
2fe5d6de MZ	163	if (rc <= 0) {
	164	if (rc && rc != -ENODATA)
	165	goto out;
	166
	167	cause = "missing-hash";
	168	status =
	169	(inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
	170	goto out;
	171	}
	172
8606404f	173	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
2fe5d6de MZ	174	if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
	175	if ((status == INTEGRITY_NOLABEL)
	176	\|\| (status == INTEGRITY_NOXATTRS))
	177	cause = "missing-HMAC";
	178	else if (status == INTEGRITY_FAIL)
	179	cause = "invalid-HMAC";
	180	goto out;
	181	}
8606404f DK	182	switch (xattr_value->type) {
8606404f DK	183	case IMA_XATTR_DIGEST:
0e5a247c DK	184	if (iint->flags & IMA_DIGSIG_REQUIRED) {
	185	cause = "IMA signature required";
	186	status = INTEGRITY_FAIL;
	187	break;
	188	}
d3634d0f DK	189	if (xattr_len - 1 >= iint->ima_hash.length)
	190	/* xattr length may be longer. md5 hash in previous
	191	version occupied 20 bytes in xattr, instead of 16
	192	*/
c7c8bb23 DK	193	rc = memcmp(xattr_value->digest,
	194	iint->ima_hash.digest,
	195	iint->ima_hash.length);
	196	else
	197	rc = -EINVAL;
8606404f DK	198	if (rc) {
	199	cause = "invalid-hash";
	200	status = INTEGRITY_FAIL;
8606404f DK	201	break;
	202	}
	203	status = INTEGRITY_PASS;
	204	break;
	205	case EVM_IMA_XATTR_DIGSIG:
	206	iint->flags \|= IMA_DIGSIG;
	207	rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
b1aaab22	208	(const char *)xattr_value, rc,
c7c8bb23 DK	209	iint->ima_hash.digest,
c7c8bb23 DK	210	iint->ima_hash.length);
8606404f DK	211	if (rc == -EOPNOTSUPP) {
	212	status = INTEGRITY_UNKNOWN;
	213	} else if (rc) {
	214	cause = "invalid-signature";
	215	status = INTEGRITY_FAIL;
	216	} else {
	217	status = INTEGRITY_PASS;
	218	}
	219	break;
	220	default:
	221	status = INTEGRITY_UNKNOWN;
	222	cause = "unknown-ima-data";
	223	break;
2fe5d6de	224	}
8606404f	225
2fe5d6de MZ	226	out:
2fe5d6de MZ	227	if (status != INTEGRITY_PASS) {
8606404f DK	228	if ((ima_appraise & IMA_APPRAISE_FIX) &&
	229	(!xattr_value \|\|
	230	xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
def3e8b9 DK	231	if (!ima_fix_xattr(dentry, iint))
def3e8b9 DK	232	status = INTEGRITY_PASS;
2fe5d6de MZ	233	}
	234	integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
	235	op, cause, rc, 0);
8606404f	236	} else {
d79d72e0	237	ima_cache_flags(iint, func);
2fe5d6de	238	}
d79d72e0	239	ima_set_cache_status(iint, func, status);
2fe5d6de MZ	240	return status;
	241	}
	242
	243	/*
	244	* ima_update_xattr - update 'security.ima' hash value
	245	*/
	246	void ima_update_xattr(struct integrity_iint_cache iint, struct file file)
	247	{
	248	struct dentry *dentry = file->f_dentry;
	249	int rc = 0;
	250
8606404f DK	251	/* do not collect and update hash for digital signatures */
	252	if (iint->flags & IMA_DIGSIG)
	253	return;
	254
d3634d0f	255	rc = ima_collect_measurement(iint, file, NULL, NULL);
2fe5d6de MZ	256	if (rc < 0)
2fe5d6de MZ	257	return;
8606404f	258
2fe5d6de MZ	259	ima_fix_xattr(dentry, iint);
	260	}
	261
	262	/**
	263	* ima_inode_post_setattr - reflect file metadata changes
	264	* @dentry: pointer to the affected dentry
	265	*
	266	* Changes to a dentry's metadata might result in needing to appraise.
	267	*
	268	* This function is called from notify_change(), which expects the caller
	269	* to lock the inode's i_mutex.
	270	*/
	271	void ima_inode_post_setattr(struct dentry *dentry)
	272	{
	273	struct inode *inode = dentry->d_inode;
	274	struct integrity_iint_cache *iint;
	275	int must_appraise, rc;
	276
	277	if (!ima_initialized \|\| !ima_appraise \|\| !S_ISREG(inode->i_mode)
	278	\|\| !inode->i_op->removexattr)
	279	return;
	280
	281	must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
	282	iint = integrity_iint_find(inode);
	283	if (iint) {
d79d72e0 MZ	284	iint->flags &= ~(IMA_APPRAISE \| IMA_APPRAISED \|
	285	IMA_APPRAISE_SUBMASK \| IMA_APPRAISED_SUBMASK \|
	286	IMA_ACTION_FLAGS);
2fe5d6de MZ	287	if (must_appraise)
2fe5d6de MZ	288	iint->flags \|= IMA_APPRAISE;
2fe5d6de MZ	289	}
	290	if (!must_appraise)
	291	rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
	292	return;
	293	}
42c63330 MZ	294
	295	/*
	296	* ima_protect_xattr - protect 'security.ima'
	297	*
	298	* Ensure that not just anyone can modify or remove 'security.ima'.
	299	*/
	300	static int ima_protect_xattr(struct dentry dentry, const char xattr_name,
	301	const void *xattr_value, size_t xattr_value_len)
	302	{
	303	if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
	304	if (!capable(CAP_SYS_ADMIN))
	305	return -EPERM;
	306	return 1;
	307	}
	308	return 0;
	309	}
	310
	311	static void ima_reset_appraise_flags(struct inode *inode)
	312	{
	313	struct integrity_iint_cache *iint;
	314
	315	if (!ima_initialized \|\| !ima_appraise \|\| !S_ISREG(inode->i_mode))
	316	return;
	317
	318	iint = integrity_iint_find(inode);
	319	if (!iint)
	320	return;
	321
45e2472e	322	iint->flags &= ~IMA_DONE_MASK;
42c63330 MZ	323	return;
	324	}
	325
	326	int ima_inode_setxattr(struct dentry dentry, const char xattr_name,
	327	const void *xattr_value, size_t xattr_value_len)
	328	{
	329	int result;
	330
	331	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
	332	xattr_value_len);
	333	if (result == 1) {
	334	ima_reset_appraise_flags(dentry->d_inode);
	335	result = 0;
	336	}
	337	return result;
	338	}
	339
	340	int ima_inode_removexattr(struct dentry dentry, const char xattr_name)
	341	{
	342	int result;
	343
	344	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
	345	if (result == 1) {
	346	ima_reset_appraise_flags(dentry->d_inode);
	347	result = 0;
	348	}
	349	return result;
	350	}