1 /*-
2  * Copyright (c) 2019 Stormshield.
3  * Copyright (c) 2019 Semihalf.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
16  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
17  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
18  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
19  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
20  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
22  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
23  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
24  * POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include <sys/param.h>
31 #include <sys/ctype.h>
32 #include <sys/eventhandler.h>
33 #include <sys/fcntl.h>
34 #include <sys/lock.h>
35 #include <sys/module.h>
36 #include <sys/mutex.h>
37 #include <sys/namei.h>
38 #include <sys/proc.h>
39 #include <sys/systm.h>
40 #include <sys/vnode.h>
41 
42 #include <crypto/sha2/sha256.h>
43 #include <crypto/sha2/sha384.h>
44 #include <crypto/sha2/sha512.h>
45 
46 #include <security/mac_veriexec/mac_veriexec.h>
47 #include <security/mac_veriexec/mac_veriexec_internal.h>
48 
49 /* The following are based on sbin/veriexec */
50 struct fingerprint_type {
51 	const char	*fp_type;
52 	int		fp_size;
53 };
54 
55 struct fp_flag {
56 	const char	*flag_name;
57 	int		flag;
58 };
59 
60 static const struct fingerprint_type fp_table[] = {
61 	{"sha256=", SHA256_DIGEST_LENGTH},
62 #if MAXFINGERPRINTLEN >= SHA384_DIGEST_LENGTH
63 	{"sha384=", SHA384_DIGEST_LENGTH},
64 #endif
65 #if MAXFINGERPRINTLEN >= SHA512_DIGEST_LENGTH
66 	{"sha512=", SHA512_DIGEST_LENGTH},
67 #endif
68 	{NULL, 0}
69 };
70 
71 static const struct fp_flag flags_table[] = {
72 	{"indirect",  VERIEXEC_INDIRECT},
73 	{"no_ptrace", VERIEXEC_NOTRACE},
74 	{"trusted",   VERIEXEC_TRUSTED},
75 	{"no_fips",   VERIEXEC_NOFIPS},
76 	{NULL, 0}
77 };
78 
79 extern struct mtx ve_mutex;
80 
81 static unsigned char	hexchar_to_byte(unsigned char c);
82 static int		hexstring_to_bin(unsigned char *buf);
83 
84 static int	get_flags(const char *entry);
85 static int	get_fp(const char *entry, char **type,
86 		    unsigned char **digest, int *flags);
87 static int	verify_digest(const char *data, size_t len,
88 		    const unsigned char *expected_hash);
89 
90 static int	open_file(const char *path, struct nameidata *nid);
91 static char	*read_manifest(char *path, unsigned char *digest);
92 static int	parse_entry(char *entry, char *prefix);
93 static int	parse_manifest(char *path, unsigned char *hash, char *prefix);
94 
95 static unsigned char
96 hexchar_to_byte(unsigned char c)
97 {
98 
99 	if (isdigit(c))
100 		return (c - '0');
101 
102 	return (isupper(c) ? c - 'A' + 10 : c - 'a' + 10);
103 }
104 
105 static int
106 hexstring_to_bin(unsigned char *buf)
107 {
108 	size_t		i, len;
109 	unsigned char	byte;
110 
111 	len = strlen(buf);
112 	for (i = 0; i < len / 2; i++) {
113 		if (!isxdigit(buf[2 * i]) || !isxdigit(buf[2 * i + 1]))
114 			return (EINVAL);
115 
116 		byte = hexchar_to_byte(buf[2 * i]) << 4;
117 		byte += hexchar_to_byte(buf[2 * i + 1]);
118 		buf[i] = byte;
119 	}
120 	return (0);
121 }
122 
123 static int
124 get_flags(const char *entry)
125 {
126 	int	i;
127 	int	result = 0;
128 
129 	for (i = 0; flags_table[i].flag_name != NULL; i++)
130 		if (strstr(entry, flags_table[i].flag_name) != NULL)
131 			result |= flags_table[i].flag;
132 
133 	return (result);
134 }
135 
136 /*
137  * Parse a single line of manifest looking for a digest and its type.
138  * We expect it to be in form of "path shaX=hash".
139  * The line will be split into path, hash type and hash value.
140  */
141 static int
142 get_fp(const char *entry, char **type, unsigned char **digest, int *flags)
143 {
144 	char	*delimiter;
145 	char	*local_digest;
146 	char	*fp_type;
147 	char	*prev_fp_type;
148 	size_t	min_len;
149 	int	i;
150 
151 	delimiter = NULL;
152 	fp_type = NULL;
153 	prev_fp_type = NULL;
154 
155 	for (i = 0; fp_table[i].fp_type != NULL; i++) {
156 		fp_type = strstr(entry, fp_table[i].fp_type);
157 		/* Look for the last "shaX=hash" in line */
158 		while (fp_type != NULL) {
159 			prev_fp_type = fp_type;
160 			fp_type++;
161 			fp_type = strstr(fp_type, fp_table[i].fp_type);
162 		}
163 		fp_type = prev_fp_type;
164 		if (fp_type != NULL) {
165 			if (fp_type == entry || fp_type[-1] != ' ')
166 				return (EINVAL);
167 
168 			/*
169 			 * The entry should contain at least
170 			 * fp_type and digest in hexadecimal form.
171 			 */
172 			min_len = strlen(fp_table[i].fp_type) +
173 				2 * fp_table[i].fp_size;
174 
175 			if (strnlen(fp_type, min_len) < min_len)
176 				return (EINVAL);
177 
178 			local_digest = &fp_type[strlen(fp_table[i].fp_type)];
179 			delimiter = &local_digest[2 * fp_table[i].fp_size];
180 
181 			/*
182 			 * Make sure that digest is followed by
183 			 * some kind of delimiter.
184 			 */
185 			if (*delimiter != '\n' &&
186 			    *delimiter != '\0' &&
187 			    *delimiter != ' ')
188 				return (EINVAL);
189 
190 			/*
191 			 * Does the entry contain flags we need to parse?
192 			 */
193 			if (*delimiter == ' ' && flags != NULL)
194 				*flags = get_flags(delimiter);
195 
196 			/*
197 			 * Split entry into three parts:
198 			 * path, fp_type and digest.
199 			 */
200 			local_digest[-1] = '\0';
201 			*delimiter = '\0';
202 			fp_type[-1] = '\0';
203 			break;
204 		}
205 	}
206 
207 	if (fp_type == NULL)
208 		return (EINVAL);
209 
210 	if (type != NULL)
211 		*type = fp_type;
212 
213 	if (digest != NULL)
214 		*digest = local_digest;
215 
216 	return (0);
217 }
218 
219 /*
220  * Currently we verify manifest using sha256.
221  * In future another env with hash type could be introduced.
222  */
223 static int
224 verify_digest(const char *data, size_t len, const unsigned char *expected_hash)
225 {
226 	SHA256_CTX	ctx;
227 	unsigned char	hash[SHA256_DIGEST_LENGTH];
228 
229 	SHA256_Init(&ctx);
230 	SHA256_Update(&ctx, data, len);
231 	SHA256_Final(hash, &ctx);
232 
233 	return (memcmp(expected_hash, hash, SHA256_DIGEST_LENGTH));
234 }
235 
236 static int
237 open_file(const char *path, struct nameidata *nid)
238 {
239 	int flags, rc;
240 
241 	flags = FREAD;
242 
243 	pwd_ensure_dirs();
244 
245 	NDINIT(nid, LOOKUP, 0, UIO_SYSSPACE, path);
246 	rc = vn_open(nid, &flags, 0, NULL);
247 	NDFREE_PNBUF(nid);
248 	if (rc != 0)
249 		return (rc);
250 
251 	return (0);
252 }
253 
254 /*
255  * Read the manifest from location specified in path and verify its digest.
256  */
257 static char*
258 read_manifest(char *path, unsigned char *digest)
259 {
260 	struct nameidata	nid;
261 	struct vattr		va;
262 	char			*data;
263 	ssize_t			bytes_read, resid;
264 	int			rc;
265 
266 	data = NULL;
267 	bytes_read = 0;
268 
269 	rc = open_file(path, &nid);
270 	if (rc != 0)
271 		goto fail;
272 
273 	rc = VOP_GETATTR(nid.ni_vp, &va, curthread->td_ucred);
274 	if (rc != 0)
275 		goto fail;
276 
277 	data = (char *)malloc(va.va_size + 1, M_VERIEXEC, M_WAITOK);
278 
279 	while (bytes_read < va.va_size) {
280 		rc = vn_rdwr(
281 		    UIO_READ, nid.ni_vp, data,
282 		    va.va_size - bytes_read, bytes_read,
283 		    UIO_SYSSPACE, IO_NODELOCKED,
284 		    curthread->td_ucred, NOCRED, &resid, curthread);
285 		if (rc != 0)
286 			goto fail;
287 
288 		bytes_read = va.va_size - resid;
289 	}
290 
291 	data[bytes_read] = '\0';
292 
293 	VOP_UNLOCK(nid.ni_vp);
294 	(void)vn_close(nid.ni_vp, FREAD, curthread->td_ucred, curthread);
295 
296 	/*
297 	 * If digest is wrong someone might be trying to fool us.
298 	 */
299 	if (verify_digest(data, va.va_size, digest))
300 		panic("Manifest hash doesn't match expected value!");
301 
302 	return (data);
303 
304 fail:
305 	if (data != NULL)
306 		free(data, M_VERIEXEC);
307 
308 	return (NULL);
309 }
310 
311 /*
312  * Process single line.
313  * First split it into path, digest_type and digest.
314  * Then try to open the file and insert its fingerprint into metadata store.
315  */
316 static int
317 parse_entry(char *entry, char *prefix)
318 {
319 	struct nameidata	nid;
320 	struct vattr		va;
321 	char			path[MAXPATHLEN];
322 	char			*fp_type;
323 	unsigned char		*digest;
324 	int			rc, is_exec, flags;
325 
326 	fp_type = NULL;
327 	digest = NULL;
328 	flags = 0;
329 
330 	rc = get_fp(entry, &fp_type, &digest, &flags);
331 	if (rc != 0)
332 		return (rc);
333 
334 	rc = hexstring_to_bin(digest);
335 	if (rc != 0)
336 		return (rc);
337 
338 	if (strnlen(entry, MAXPATHLEN) == MAXPATHLEN)
339 		return (EINVAL);
340 
341 	/* If the path is not absolute prepend it with a prefix */
342 	if (prefix != NULL && entry[0] != '/') {
343 		rc = snprintf(path, MAXPATHLEN, "%s/%s",
344 			    prefix, entry);
345 		if (rc < 0)
346 			return (-rc);
347 	} else {
348 		strcpy(path, entry);
349 	}
350 
351 	rc = open_file(path, &nid);
352 	NDFREE_PNBUF(&nid);
353 	if (rc != 0)
354 		return (rc);
355 
356 	rc = VOP_GETATTR(nid.ni_vp, &va, curthread->td_ucred);
357 	if (rc != 0)
358 		goto out;
359 
360 	is_exec = (va.va_mode & VEXEC);
361 
362 	mtx_lock(&ve_mutex);
363 	rc = mac_veriexec_metadata_add_file(
364 	    is_exec == 0,
365 	    va.va_fsid, va.va_fileid, va.va_gen,
366 	    digest,
367 	    NULL, 0,
368 	    flags, fp_type, 1);
369 	mtx_unlock(&ve_mutex);
370 
371 out:
372 	VOP_UNLOCK(nid.ni_vp);
373 	vn_close(nid.ni_vp, FREAD, curthread->td_ucred, curthread);
374 	return (rc);
375 }
376 
377 /*
378  * Look for manifest in env that have beed passed by loader.
379  * This routine should be called right after the rootfs is mounted.
380  */
381 static int
382 parse_manifest(char *path, unsigned char *hash, char *prefix)
383 {
384 	char	*data;
385 	char	*entry;
386 	char	*next_entry;
387 	int	rc, success_count;
388 
389 	data = NULL;
390 	success_count = 0;
391 	rc = 0;
392 
393 	data = read_manifest(path, hash);
394 	if (data == NULL) {
395 		rc = EIO;
396 		goto out;
397 	}
398 
399 	entry = data;
400 	while (entry != NULL) {
401 		next_entry = strchr(entry, '\n');
402 		if (next_entry != NULL) {
403 			*next_entry = '\0';
404 			next_entry++;
405 		}
406 		if (entry[0] == '\n' || entry[0] == '\0') {
407 			entry = next_entry;
408 			continue;
409 		}
410 		if ((rc = parse_entry(entry, prefix)))
411 			printf("mac_veriexec_parser: Warning: Failed to parse"
412 			       " entry with rc:%d, entry:\"%s\"\n", rc, entry);
413 		else
414 			success_count++;
415 
416 		entry = next_entry;
417 	}
418 	rc = 0;
419 
420 out:
421 	if (data != NULL)
422 		free(data, M_VERIEXEC);
423 
424 	if (success_count == 0)
425 		rc = EINVAL;
426 
427 	return (rc);
428 }
429 
430 static void
431 parse_manifest_event(void *dummy)
432 {
433 	char		*manifest_path;
434 	char		*manifest_prefix;
435 	unsigned char	*manifest_hash;
436 	int		rc;
437 
438 	/* If the envs are not set fail silently */
439 	manifest_path = kern_getenv("veriexec.manifest_path");
440 	if (manifest_path == NULL)
441 		return;
442 
443 	manifest_hash = kern_getenv("veriexec.manifest_hash");
444 	if (manifest_hash == NULL) {
445 		freeenv(manifest_path);
446 		return;
447 	}
448 
449 	manifest_prefix = kern_getenv("veriexec.manifest_prefix");
450 
451 	if (strlen(manifest_hash) != 2 * SHA256_DIGEST_LENGTH)
452 		panic("veriexec.manifest_hash has incorrect size");
453 
454 	rc = hexstring_to_bin(manifest_hash);
455 	if (rc != 0)
456 		panic("mac_veriexec: veriexec.loader.manifest_hash"
457 		    " doesn't contain a hash in hexadecimal form");
458 
459 	rc = parse_manifest(manifest_path, manifest_hash, manifest_prefix);
460 	if (rc != 0)
461 		panic("mac_veriexec: Failed to parse manifest err=%d", rc);
462 
463 	mtx_lock(&ve_mutex);
464 	mac_veriexec_set_state(
465 	    VERIEXEC_STATE_LOADED | VERIEXEC_STATE_ACTIVE |
466 	    VERIEXEC_STATE_LOCKED | VERIEXEC_STATE_ENFORCE);
467 	mtx_unlock(&ve_mutex);
468 
469 	freeenv(manifest_path);
470 	freeenv(manifest_hash);
471 	if (manifest_prefix != NULL)
472 		freeenv(manifest_prefix);
473 }
474 
475 EVENTHANDLER_DEFINE(mountroot, parse_manifest_event, NULL, 0);
476