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#include <crypto/hash_info.h>
19
20#include "ima.h"
21
22static int __init default_appraise_setup(char *str)
23{
24	if (strncmp(str, "off", 3) == 0)
25		ima_appraise = 0;
26	else if (strncmp(str, "log", 3) == 0)
27		ima_appraise = IMA_APPRAISE_LOG;
28	else if (strncmp(str, "fix", 3) == 0)
29		ima_appraise = IMA_APPRAISE_FIX;
30	return 1;
31}
32
33__setup("ima_appraise=", default_appraise_setup);
34
35/*
36 * ima_must_appraise - set appraise flag
37 *
38 * Return 1 to appraise
39 */
40int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
41{
42	if (!ima_appraise)
43		return 0;
44
45	return ima_match_policy(inode, func, mask, IMA_APPRAISE);
46}
47
48static int ima_fix_xattr(struct dentry *dentry,
49			 struct integrity_iint_cache *iint)
50{
51	int rc, offset;
52	u8 algo = iint->ima_hash->algo;
53
54	if (algo <= HASH_ALGO_SHA1) {
55		offset = 1;
56		iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
57	} else {
58		offset = 0;
59		iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
60		iint->ima_hash->xattr.ng.algo = algo;
61	}
62	rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
63				   &iint->ima_hash->xattr.data[offset],
64				   (sizeof(iint->ima_hash->xattr) - offset) +
65				   iint->ima_hash->length, 0);
66	return rc;
67}
68
69/* Return specific func appraised cached result */
70enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
71					   int func)
72{
73	switch (func) {
74	case MMAP_CHECK:
75		return iint->ima_mmap_status;
76	case BPRM_CHECK:
77		return iint->ima_bprm_status;
78	case MODULE_CHECK:
79		return iint->ima_module_status;
80	case FIRMWARE_CHECK:
81		return iint->ima_firmware_status;
82	case FILE_CHECK:
83	default:
84		return iint->ima_file_status;
85	}
86}
87
88static void ima_set_cache_status(struct integrity_iint_cache *iint,
89				 int func, enum integrity_status status)
90{
91	switch (func) {
92	case MMAP_CHECK:
93		iint->ima_mmap_status = status;
94		break;
95	case BPRM_CHECK:
96		iint->ima_bprm_status = status;
97		break;
98	case MODULE_CHECK:
99		iint->ima_module_status = status;
100		break;
101	case FIRMWARE_CHECK:
102		iint->ima_firmware_status = status;
103		break;
104	case FILE_CHECK:
105	default:
106		iint->ima_file_status = status;
107		break;
108	}
109}
110
111static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
112{
113	switch (func) {
114	case MMAP_CHECK:
115		iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
116		break;
117	case BPRM_CHECK:
118		iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
119		break;
120	case MODULE_CHECK:
121		iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED);
122		break;
123	case FIRMWARE_CHECK:
124		iint->flags |= (IMA_FIRMWARE_APPRAISED | IMA_APPRAISED);
125		break;
126	case FILE_CHECK:
127	default:
128		iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
129		break;
130	}
131}
132
133void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
134		       struct ima_digest_data *hash)
135{
136	struct signature_v2_hdr *sig;
137
138	if (!xattr_value || xattr_len < 2)
139		return;
140
141	switch (xattr_value->type) {
142	case EVM_IMA_XATTR_DIGSIG:
143		sig = (typeof(sig))xattr_value;
144		if (sig->version != 2 || xattr_len <= sizeof(*sig))
145			return;
146		hash->algo = sig->hash_algo;
147		break;
148	case IMA_XATTR_DIGEST_NG:
149		hash->algo = xattr_value->digest[0];
150		break;
151	case IMA_XATTR_DIGEST:
152		/* this is for backward compatibility */
153		if (xattr_len == 21) {
154			unsigned int zero = 0;
155			if (!memcmp(&xattr_value->digest[16], &zero, 4))
156				hash->algo = HASH_ALGO_MD5;
157			else
158				hash->algo = HASH_ALGO_SHA1;
159		} else if (xattr_len == 17)
160			hash->algo = HASH_ALGO_MD5;
161		break;
162	}
163}
164
165int ima_read_xattr(struct dentry *dentry,
166		   struct evm_ima_xattr_data **xattr_value)
167{
168	struct inode *inode = d_backing_inode(dentry);
169
170	if (!inode->i_op->getxattr)
171		return 0;
172
173	return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
174				  0, GFP_NOFS);
175}
176
177/*
178 * ima_appraise_measurement - appraise file measurement
179 *
180 * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
181 * Assuming success, compare the xattr hash with the collected measurement.
182 *
183 * Return 0 on success, error code otherwise
184 */
185int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
186			     struct file *file, const unsigned char *filename,
187			     struct evm_ima_xattr_data *xattr_value,
188			     int xattr_len, int opened)
189{
190	static const char op[] = "appraise_data";
191	char *cause = "unknown";
192	struct dentry *dentry = file->f_path.dentry;
193	struct inode *inode = d_backing_inode(dentry);
194	enum integrity_status status = INTEGRITY_UNKNOWN;
195	int rc = xattr_len, hash_start = 0;
196
197	if (!inode->i_op->getxattr)
198		return INTEGRITY_UNKNOWN;
199
200	if (rc <= 0) {
201		if (rc && rc != -ENODATA)
202			goto out;
203
204		cause = "missing-hash";
205		status = INTEGRITY_NOLABEL;
206		if (opened & FILE_CREATED) {
207			iint->flags |= IMA_NEW_FILE;
208			status = INTEGRITY_PASS;
209		}
210		goto out;
211	}
212
213	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
214	if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
215		if ((status == INTEGRITY_NOLABEL)
216		    || (status == INTEGRITY_NOXATTRS))
217			cause = "missing-HMAC";
218		else if (status == INTEGRITY_FAIL)
219			cause = "invalid-HMAC";
220		goto out;
221	}
222	switch (xattr_value->type) {
223	case IMA_XATTR_DIGEST_NG:
224		/* first byte contains algorithm id */
225		hash_start = 1;
226	case IMA_XATTR_DIGEST:
227		if (iint->flags & IMA_DIGSIG_REQUIRED) {
228			cause = "IMA-signature-required";
229			status = INTEGRITY_FAIL;
230			break;
231		}
232		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
233				iint->ima_hash->length)
234			/* xattr length may be longer. md5 hash in previous
235			   version occupied 20 bytes in xattr, instead of 16
236			 */
237			rc = memcmp(&xattr_value->digest[hash_start],
238				    iint->ima_hash->digest,
239				    iint->ima_hash->length);
240		else
241			rc = -EINVAL;
242		if (rc) {
243			cause = "invalid-hash";
244			status = INTEGRITY_FAIL;
245			break;
246		}
247		status = INTEGRITY_PASS;
248		break;
249	case EVM_IMA_XATTR_DIGSIG:
250		iint->flags |= IMA_DIGSIG;
251		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
252					     (const char *)xattr_value, rc,
253					     iint->ima_hash->digest,
254					     iint->ima_hash->length);
255		if (rc == -EOPNOTSUPP) {
256			status = INTEGRITY_UNKNOWN;
257		} else if (rc) {
258			cause = "invalid-signature";
259			status = INTEGRITY_FAIL;
260		} else {
261			status = INTEGRITY_PASS;
262		}
263		break;
264	default:
265		status = INTEGRITY_UNKNOWN;
266		cause = "unknown-ima-data";
267		break;
268	}
269
270out:
271	if (status != INTEGRITY_PASS) {
272		if ((ima_appraise & IMA_APPRAISE_FIX) &&
273		    (!xattr_value ||
274		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
275			if (!ima_fix_xattr(dentry, iint))
276				status = INTEGRITY_PASS;
277		}
278		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
279				    op, cause, rc, 0);
280	} else {
281		ima_cache_flags(iint, func);
282	}
283	ima_set_cache_status(iint, func, status);
284	return status;
285}
286
287/*
288 * ima_update_xattr - update 'security.ima' hash value
289 */
290void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
291{
292	struct dentry *dentry = file->f_path.dentry;
293	int rc = 0;
294
295	/* do not collect and update hash for digital signatures */
296	if (iint->flags & IMA_DIGSIG)
297		return;
298
299	rc = ima_collect_measurement(iint, file, NULL, NULL);
300	if (rc < 0)
301		return;
302
303	ima_fix_xattr(dentry, iint);
304}
305
306/**
307 * ima_inode_post_setattr - reflect file metadata changes
308 * @dentry: pointer to the affected dentry
309 *
310 * Changes to a dentry's metadata might result in needing to appraise.
311 *
312 * This function is called from notify_change(), which expects the caller
313 * to lock the inode's i_mutex.
314 */
315void ima_inode_post_setattr(struct dentry *dentry)
316{
317	struct inode *inode = d_backing_inode(dentry);
318	struct integrity_iint_cache *iint;
319	int must_appraise, rc;
320
321	if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
322	    || !inode->i_op->removexattr)
323		return;
324
325	must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
326	iint = integrity_iint_find(inode);
327	if (iint) {
328		iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
329				 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
330				 IMA_ACTION_FLAGS);
331		if (must_appraise)
332			iint->flags |= IMA_APPRAISE;
333	}
334	if (!must_appraise)
335		rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
336	return;
337}
338
339/*
340 * ima_protect_xattr - protect 'security.ima'
341 *
342 * Ensure that not just anyone can modify or remove 'security.ima'.
343 */
344static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
345			     const void *xattr_value, size_t xattr_value_len)
346{
347	if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
348		if (!capable(CAP_SYS_ADMIN))
349			return -EPERM;
350		return 1;
351	}
352	return 0;
353}
354
355static void ima_reset_appraise_flags(struct inode *inode, int digsig)
356{
357	struct integrity_iint_cache *iint;
358
359	if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
360		return;
361
362	iint = integrity_iint_find(inode);
363	if (!iint)
364		return;
365
366	iint->flags &= ~IMA_DONE_MASK;
367	if (digsig)
368		iint->flags |= IMA_DIGSIG;
369	return;
370}
371
372int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
373		       const void *xattr_value, size_t xattr_value_len)
374{
375	const struct evm_ima_xattr_data *xvalue = xattr_value;
376	int result;
377
378	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
379				   xattr_value_len);
380	if (result == 1) {
381		bool digsig;
382
383		if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
384			return -EINVAL;
385		digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG);
386		if (!digsig && (ima_appraise & IMA_APPRAISE_ENFORCE))
387			return -EPERM;
388		ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
389		result = 0;
390	}
391	return result;
392}
393
394int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
395{
396	int result;
397
398	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
399	if (result == 1) {
400		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
401		result = 0;
402	}
403	return result;
404}
405