1 /*
2  * AppArmor security module
3  *
4  * This file contains AppArmor functions for unpacking policy loaded from
5  * userspace.
6  *
7  * Copyright (C) 1998-2008 Novell/SUSE
8  * Copyright 2009-2010 Canonical Ltd.
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public License as
12  * published by the Free Software Foundation, version 2 of the
13  * License.
14  *
15  * AppArmor uses a serialized binary format for loading policy.
16  * To find policy format documentation look in Documentation/apparmor.txt
17  * All policy is validated before it is used.
18  */
19 
20 #include <asm/unaligned.h>
21 #include <linux/ctype.h>
22 #include <linux/errno.h>
23 
24 #include "include/apparmor.h"
25 #include "include/audit.h"
26 #include "include/context.h"
27 #include "include/match.h"
28 #include "include/policy.h"
29 #include "include/policy_unpack.h"
30 #include "include/sid.h"
31 
32 /*
33  * The AppArmor interface treats data as a type byte followed by the
34  * actual data.  The interface has the notion of a a named entry
35  * which has a name (AA_NAME typecode followed by name string) followed by
36  * the entries typecode and data.  Named types allow for optional
37  * elements and extensions to be added and tested for without breaking
38  * backwards compatibility.
39  */
40 
41 enum aa_code {
42 	AA_U8,
43 	AA_U16,
44 	AA_U32,
45 	AA_U64,
46 	AA_NAME,		/* same as string except it is items name */
47 	AA_STRING,
48 	AA_BLOB,
49 	AA_STRUCT,
50 	AA_STRUCTEND,
51 	AA_LIST,
52 	AA_LISTEND,
53 	AA_ARRAY,
54 	AA_ARRAYEND,
55 };
56 
57 /*
58  * aa_ext is the read of the buffer containing the serialized profile.  The
59  * data is copied into a kernel buffer in apparmorfs and then handed off to
60  * the unpack routines.
61  */
62 struct aa_ext {
63 	void *start;
64 	void *end;
65 	void *pos;		/* pointer to current position in the buffer */
66 	u32 version;
67 };
68 
69 /* audit callback for unpack fields */
70 static void audit_cb(struct audit_buffer *ab, void *va)
71 {
72 	struct common_audit_data *sa = va;
73 	if (sa->aad.iface.target) {
74 		struct aa_profile *name = sa->aad.iface.target;
75 		audit_log_format(ab, " name=");
76 		audit_log_untrustedstring(ab, name->base.hname);
77 	}
78 	if (sa->aad.iface.pos)
79 		audit_log_format(ab, " offset=%ld", sa->aad.iface.pos);
80 }
81 
82 /**
83  * audit_iface - do audit message for policy unpacking/load/replace/remove
84  * @new: profile if it has been allocated (MAYBE NULL)
85  * @name: name of the profile being manipulated (MAYBE NULL)
86  * @info: any extra info about the failure (MAYBE NULL)
87  * @e: buffer position info (NOT NULL)
88  * @error: error code
89  *
90  * Returns: %0 or error
91  */
92 static int audit_iface(struct aa_profile *new, const char *name,
93 		       const char *info, struct aa_ext *e, int error)
94 {
95 	struct aa_profile *profile = __aa_current_profile();
96 	struct common_audit_data sa;
97 	COMMON_AUDIT_DATA_INIT(&sa, NONE);
98 	sa.aad.iface.pos = e->pos - e->start;
99 	sa.aad.iface.target = new;
100 	sa.aad.name = name;
101 	sa.aad.info = info;
102 	sa.aad.error = error;
103 
104 	return aa_audit(AUDIT_APPARMOR_STATUS, profile, GFP_KERNEL, &sa,
105 			audit_cb);
106 }
107 
108 /* test if read will be in packed data bounds */
109 static bool inbounds(struct aa_ext *e, size_t size)
110 {
111 	return (size <= e->end - e->pos);
112 }
113 
114 /**
115  * aa_u16_chunck - test and do bounds checking for a u16 size based chunk
116  * @e: serialized data read head (NOT NULL)
117  * @chunk: start address for chunk of data (NOT NULL)
118  *
119  * Returns: the size of chunk found with the read head at the end of the chunk.
120  */
121 static size_t unpack_u16_chunk(struct aa_ext *e, char **chunk)
122 {
123 	size_t size = 0;
124 
125 	if (!inbounds(e, sizeof(u16)))
126 		return 0;
127 	size = le16_to_cpu(get_unaligned((u16 *) e->pos));
128 	e->pos += sizeof(u16);
129 	if (!inbounds(e, size))
130 		return 0;
131 	*chunk = e->pos;
132 	e->pos += size;
133 	return size;
134 }
135 
136 /* unpack control byte */
137 static bool unpack_X(struct aa_ext *e, enum aa_code code)
138 {
139 	if (!inbounds(e, 1))
140 		return 0;
141 	if (*(u8 *) e->pos != code)
142 		return 0;
143 	e->pos++;
144 	return 1;
145 }
146 
147 /**
148  * unpack_nameX - check is the next element is of type X with a name of @name
149  * @e: serialized data extent information  (NOT NULL)
150  * @code: type code
151  * @name: name to match to the serialized element.  (MAYBE NULL)
152  *
153  * check that the next serialized data element is of type X and has a tag
154  * name @name.  If @name is specified then there must be a matching
155  * name element in the stream.  If @name is NULL any name element will be
156  * skipped and only the typecode will be tested.
157  *
158  * Returns 1 on success (both type code and name tests match) and the read
159  * head is advanced past the headers
160  *
161  * Returns: 0 if either match fails, the read head does not move
162  */
163 static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name)
164 {
165 	/*
166 	 * May need to reset pos if name or type doesn't match
167 	 */
168 	void *pos = e->pos;
169 	/*
170 	 * Check for presence of a tagname, and if present name size
171 	 * AA_NAME tag value is a u16.
172 	 */
173 	if (unpack_X(e, AA_NAME)) {
174 		char *tag = NULL;
175 		size_t size = unpack_u16_chunk(e, &tag);
176 		/* if a name is specified it must match. otherwise skip tag */
177 		if (name && (!size || strcmp(name, tag)))
178 			goto fail;
179 	} else if (name) {
180 		/* if a name is specified and there is no name tag fail */
181 		goto fail;
182 	}
183 
184 	/* now check if type code matches */
185 	if (unpack_X(e, code))
186 		return 1;
187 
188 fail:
189 	e->pos = pos;
190 	return 0;
191 }
192 
193 static bool unpack_u32(struct aa_ext *e, u32 *data, const char *name)
194 {
195 	if (unpack_nameX(e, AA_U32, name)) {
196 		if (!inbounds(e, sizeof(u32)))
197 			return 0;
198 		if (data)
199 			*data = le32_to_cpu(get_unaligned((u32 *) e->pos));
200 		e->pos += sizeof(u32);
201 		return 1;
202 	}
203 	return 0;
204 }
205 
206 static bool unpack_u64(struct aa_ext *e, u64 *data, const char *name)
207 {
208 	if (unpack_nameX(e, AA_U64, name)) {
209 		if (!inbounds(e, sizeof(u64)))
210 			return 0;
211 		if (data)
212 			*data = le64_to_cpu(get_unaligned((u64 *) e->pos));
213 		e->pos += sizeof(u64);
214 		return 1;
215 	}
216 	return 0;
217 }
218 
219 static size_t unpack_array(struct aa_ext *e, const char *name)
220 {
221 	if (unpack_nameX(e, AA_ARRAY, name)) {
222 		int size;
223 		if (!inbounds(e, sizeof(u16)))
224 			return 0;
225 		size = (int)le16_to_cpu(get_unaligned((u16 *) e->pos));
226 		e->pos += sizeof(u16);
227 		return size;
228 	}
229 	return 0;
230 }
231 
232 static size_t unpack_blob(struct aa_ext *e, char **blob, const char *name)
233 {
234 	if (unpack_nameX(e, AA_BLOB, name)) {
235 		u32 size;
236 		if (!inbounds(e, sizeof(u32)))
237 			return 0;
238 		size = le32_to_cpu(get_unaligned((u32 *) e->pos));
239 		e->pos += sizeof(u32);
240 		if (inbounds(e, (size_t) size)) {
241 			*blob = e->pos;
242 			e->pos += size;
243 			return size;
244 		}
245 	}
246 	return 0;
247 }
248 
249 static int unpack_str(struct aa_ext *e, const char **string, const char *name)
250 {
251 	char *src_str;
252 	size_t size = 0;
253 	void *pos = e->pos;
254 	*string = NULL;
255 	if (unpack_nameX(e, AA_STRING, name)) {
256 		size = unpack_u16_chunk(e, &src_str);
257 		if (size) {
258 			/* strings are null terminated, length is size - 1 */
259 			if (src_str[size - 1] != 0)
260 				goto fail;
261 			*string = src_str;
262 		}
263 	}
264 	return size;
265 
266 fail:
267 	e->pos = pos;
268 	return 0;
269 }
270 
271 static int unpack_strdup(struct aa_ext *e, char **string, const char *name)
272 {
273 	const char *tmp;
274 	void *pos = e->pos;
275 	int res = unpack_str(e, &tmp, name);
276 	*string = NULL;
277 
278 	if (!res)
279 		return 0;
280 
281 	*string = kmemdup(tmp, res, GFP_KERNEL);
282 	if (!*string) {
283 		e->pos = pos;
284 		return 0;
285 	}
286 
287 	return res;
288 }
289 
290 /**
291  * verify_accept - verify the accept tables of a dfa
292  * @dfa: dfa to verify accept tables of (NOT NULL)
293  * @flags: flags governing dfa
294  *
295  * Returns: 1 if valid accept tables else 0 if error
296  */
297 static bool verify_accept(struct aa_dfa *dfa, int flags)
298 {
299 	int i;
300 
301 	/* verify accept permissions */
302 	for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {
303 		int mode = ACCEPT_TABLE(dfa)[i];
304 
305 		if (mode & ~DFA_VALID_PERM_MASK)
306 			return 0;
307 
308 		if (ACCEPT_TABLE2(dfa)[i] & ~DFA_VALID_PERM2_MASK)
309 			return 0;
310 	}
311 	return 1;
312 }
313 
314 /**
315  * unpack_dfa - unpack a file rule dfa
316  * @e: serialized data extent information (NOT NULL)
317  *
318  * returns dfa or ERR_PTR or NULL if no dfa
319  */
320 static struct aa_dfa *unpack_dfa(struct aa_ext *e)
321 {
322 	char *blob = NULL;
323 	size_t size;
324 	struct aa_dfa *dfa = NULL;
325 
326 	size = unpack_blob(e, &blob, "aadfa");
327 	if (size) {
328 		/*
329 		 * The dfa is aligned with in the blob to 8 bytes
330 		 * from the beginning of the stream.
331 		 */
332 		size_t sz = blob - (char *)e->start;
333 		size_t pad = ALIGN(sz, 8) - sz;
334 		int flags = TO_ACCEPT1_FLAG(YYTD_DATA32) |
335 			TO_ACCEPT2_FLAG(YYTD_DATA32);
336 
337 
338 		if (aa_g_paranoid_load)
339 			flags |= DFA_FLAG_VERIFY_STATES;
340 
341 		dfa = aa_dfa_unpack(blob + pad, size - pad, flags);
342 
343 		if (IS_ERR(dfa))
344 			return dfa;
345 
346 		if (!verify_accept(dfa, flags))
347 			goto fail;
348 	}
349 
350 	return dfa;
351 
352 fail:
353 	aa_put_dfa(dfa);
354 	return ERR_PTR(-EPROTO);
355 }
356 
357 /**
358  * unpack_trans_table - unpack a profile transition table
359  * @e: serialized data extent information  (NOT NULL)
360  * @profile: profile to add the accept table to (NOT NULL)
361  *
362  * Returns: 1 if table succesfully unpacked
363  */
364 static bool unpack_trans_table(struct aa_ext *e, struct aa_profile *profile)
365 {
366 	void *pos = e->pos;
367 
368 	/* exec table is optional */
369 	if (unpack_nameX(e, AA_STRUCT, "xtable")) {
370 		int i, size;
371 
372 		size = unpack_array(e, NULL);
373 		/* currently 4 exec bits and entries 0-3 are reserved iupcx */
374 		if (size > 16 - 4)
375 			goto fail;
376 		profile->file.trans.table = kzalloc(sizeof(char *) * size,
377 						    GFP_KERNEL);
378 		if (!profile->file.trans.table)
379 			goto fail;
380 
381 		profile->file.trans.size = size;
382 		for (i = 0; i < size; i++) {
383 			char *str;
384 			int c, j, size = unpack_strdup(e, &str, NULL);
385 			/* unpack_strdup verifies that the last character is
386 			 * null termination byte.
387 			 */
388 			if (!size)
389 				goto fail;
390 			profile->file.trans.table[i] = str;
391 			/* verify that name doesn't start with space */
392 			if (isspace(*str))
393 				goto fail;
394 
395 			/* count internal #  of internal \0 */
396 			for (c = j = 0; j < size - 2; j++) {
397 				if (!str[j])
398 					c++;
399 			}
400 			if (*str == ':') {
401 				/* beginning with : requires an embedded \0,
402 				 * verify that exactly 1 internal \0 exists
403 				 * trailing \0 already verified by unpack_strdup
404 				 */
405 				if (c != 1)
406 					goto fail;
407 				/* first character after : must be valid */
408 				if (!str[1])
409 					goto fail;
410 			} else if (c)
411 				/* fail - all other cases with embedded \0 */
412 				goto fail;
413 		}
414 		if (!unpack_nameX(e, AA_ARRAYEND, NULL))
415 			goto fail;
416 		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
417 			goto fail;
418 	}
419 	return 1;
420 
421 fail:
422 	aa_free_domain_entries(&profile->file.trans);
423 	e->pos = pos;
424 	return 0;
425 }
426 
427 static bool unpack_rlimits(struct aa_ext *e, struct aa_profile *profile)
428 {
429 	void *pos = e->pos;
430 
431 	/* rlimits are optional */
432 	if (unpack_nameX(e, AA_STRUCT, "rlimits")) {
433 		int i, size;
434 		u32 tmp = 0;
435 		if (!unpack_u32(e, &tmp, NULL))
436 			goto fail;
437 		profile->rlimits.mask = tmp;
438 
439 		size = unpack_array(e, NULL);
440 		if (size > RLIM_NLIMITS)
441 			goto fail;
442 		for (i = 0; i < size; i++) {
443 			u64 tmp = 0;
444 			int a = aa_map_resource(i);
445 			if (!unpack_u64(e, &tmp, NULL))
446 				goto fail;
447 			profile->rlimits.limits[a].rlim_max = tmp;
448 		}
449 		if (!unpack_nameX(e, AA_ARRAYEND, NULL))
450 			goto fail;
451 		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
452 			goto fail;
453 	}
454 	return 1;
455 
456 fail:
457 	e->pos = pos;
458 	return 0;
459 }
460 
461 /**
462  * unpack_profile - unpack a serialized profile
463  * @e: serialized data extent information (NOT NULL)
464  *
465  * NOTE: unpack profile sets audit struct if there is a failure
466  */
467 static struct aa_profile *unpack_profile(struct aa_ext *e)
468 {
469 	struct aa_profile *profile = NULL;
470 	const char *name = NULL;
471 	int error = -EPROTO;
472 	kernel_cap_t tmpcap;
473 	u32 tmp;
474 
475 	/* check that we have the right struct being passed */
476 	if (!unpack_nameX(e, AA_STRUCT, "profile"))
477 		goto fail;
478 	if (!unpack_str(e, &name, NULL))
479 		goto fail;
480 
481 	profile = aa_alloc_profile(name);
482 	if (!profile)
483 		return ERR_PTR(-ENOMEM);
484 
485 	/* profile renaming is optional */
486 	(void) unpack_str(e, &profile->rename, "rename");
487 
488 	/* xmatch is optional and may be NULL */
489 	profile->xmatch = unpack_dfa(e);
490 	if (IS_ERR(profile->xmatch)) {
491 		error = PTR_ERR(profile->xmatch);
492 		profile->xmatch = NULL;
493 		goto fail;
494 	}
495 	/* xmatch_len is not optional if xmatch is set */
496 	if (profile->xmatch) {
497 		if (!unpack_u32(e, &tmp, NULL))
498 			goto fail;
499 		profile->xmatch_len = tmp;
500 	}
501 
502 	/* per profile debug flags (complain, audit) */
503 	if (!unpack_nameX(e, AA_STRUCT, "flags"))
504 		goto fail;
505 	if (!unpack_u32(e, &tmp, NULL))
506 		goto fail;
507 	if (tmp)
508 		profile->flags |= PFLAG_HAT;
509 	if (!unpack_u32(e, &tmp, NULL))
510 		goto fail;
511 	if (tmp)
512 		profile->mode = APPARMOR_COMPLAIN;
513 	if (!unpack_u32(e, &tmp, NULL))
514 		goto fail;
515 	if (tmp)
516 		profile->audit = AUDIT_ALL;
517 
518 	if (!unpack_nameX(e, AA_STRUCTEND, NULL))
519 		goto fail;
520 
521 	/* path_flags is optional */
522 	if (unpack_u32(e, &profile->path_flags, "path_flags"))
523 		profile->path_flags |= profile->flags & PFLAG_MEDIATE_DELETED;
524 	else
525 		/* set a default value if path_flags field is not present */
526 		profile->path_flags = PFLAG_MEDIATE_DELETED;
527 
528 	if (!unpack_u32(e, &(profile->caps.allow.cap[0]), NULL))
529 		goto fail;
530 	if (!unpack_u32(e, &(profile->caps.audit.cap[0]), NULL))
531 		goto fail;
532 	if (!unpack_u32(e, &(profile->caps.quiet.cap[0]), NULL))
533 		goto fail;
534 	if (!unpack_u32(e, &tmpcap.cap[0], NULL))
535 		goto fail;
536 
537 	if (unpack_nameX(e, AA_STRUCT, "caps64")) {
538 		/* optional upper half of 64 bit caps */
539 		if (!unpack_u32(e, &(profile->caps.allow.cap[1]), NULL))
540 			goto fail;
541 		if (!unpack_u32(e, &(profile->caps.audit.cap[1]), NULL))
542 			goto fail;
543 		if (!unpack_u32(e, &(profile->caps.quiet.cap[1]), NULL))
544 			goto fail;
545 		if (!unpack_u32(e, &(tmpcap.cap[1]), NULL))
546 			goto fail;
547 		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
548 			goto fail;
549 	}
550 
551 	if (unpack_nameX(e, AA_STRUCT, "capsx")) {
552 		/* optional extended caps mediation mask */
553 		if (!unpack_u32(e, &(profile->caps.extended.cap[0]), NULL))
554 			goto fail;
555 		if (!unpack_u32(e, &(profile->caps.extended.cap[1]), NULL))
556 			goto fail;
557 	}
558 
559 	if (!unpack_rlimits(e, profile))
560 		goto fail;
561 
562 	/* get file rules */
563 	profile->file.dfa = unpack_dfa(e);
564 	if (IS_ERR(profile->file.dfa)) {
565 		error = PTR_ERR(profile->file.dfa);
566 		profile->file.dfa = NULL;
567 		goto fail;
568 	}
569 
570 	if (!unpack_u32(e, &profile->file.start, "dfa_start"))
571 		/* default start state */
572 		profile->file.start = DFA_START;
573 
574 	if (!unpack_trans_table(e, profile))
575 		goto fail;
576 
577 	if (!unpack_nameX(e, AA_STRUCTEND, NULL))
578 		goto fail;
579 
580 	return profile;
581 
582 fail:
583 	if (profile)
584 		name = NULL;
585 	else if (!name)
586 		name = "unknown";
587 	audit_iface(profile, name, "failed to unpack profile", e, error);
588 	aa_put_profile(profile);
589 
590 	return ERR_PTR(error);
591 }
592 
593 /**
594  * verify_head - unpack serialized stream header
595  * @e: serialized data read head (NOT NULL)
596  * @ns: Returns - namespace if one is specified else NULL (NOT NULL)
597  *
598  * Returns: error or 0 if header is good
599  */
600 static int verify_header(struct aa_ext *e, const char **ns)
601 {
602 	int error = -EPROTONOSUPPORT;
603 	/* get the interface version */
604 	if (!unpack_u32(e, &e->version, "version")) {
605 		audit_iface(NULL, NULL, "invalid profile format", e, error);
606 		return error;
607 	}
608 
609 	/* check that the interface version is currently supported */
610 	if (e->version != 5) {
611 		audit_iface(NULL, NULL, "unsupported interface version", e,
612 			    error);
613 		return error;
614 	}
615 
616 	/* read the namespace if present */
617 	if (!unpack_str(e, ns, "namespace"))
618 		*ns = NULL;
619 
620 	return 0;
621 }
622 
623 static bool verify_xindex(int xindex, int table_size)
624 {
625 	int index, xtype;
626 	xtype = xindex & AA_X_TYPE_MASK;
627 	index = xindex & AA_X_INDEX_MASK;
628 	if (xtype == AA_X_TABLE && index > table_size)
629 		return 0;
630 	return 1;
631 }
632 
633 /* verify dfa xindexes are in range of transition tables */
634 static bool verify_dfa_xindex(struct aa_dfa *dfa, int table_size)
635 {
636 	int i;
637 	for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {
638 		if (!verify_xindex(dfa_user_xindex(dfa, i), table_size))
639 			return 0;
640 		if (!verify_xindex(dfa_other_xindex(dfa, i), table_size))
641 			return 0;
642 	}
643 	return 1;
644 }
645 
646 /**
647  * verify_profile - Do post unpack analysis to verify profile consistency
648  * @profile: profile to verify (NOT NULL)
649  *
650  * Returns: 0 if passes verification else error
651  */
652 static int verify_profile(struct aa_profile *profile)
653 {
654 	if (aa_g_paranoid_load) {
655 		if (profile->file.dfa &&
656 		    !verify_dfa_xindex(profile->file.dfa,
657 				       profile->file.trans.size)) {
658 			audit_iface(profile, NULL, "Invalid named transition",
659 				    NULL, -EPROTO);
660 			return -EPROTO;
661 		}
662 	}
663 
664 	return 0;
665 }
666 
667 /**
668  * aa_unpack - unpack packed binary profile data loaded from user space
669  * @udata: user data copied to kmem  (NOT NULL)
670  * @size: the size of the user data
671  * @ns: Returns namespace profile is in if specified else NULL (NOT NULL)
672  *
673  * Unpack user data and return refcounted allocated profile or ERR_PTR
674  *
675  * Returns: profile else error pointer if fails to unpack
676  */
677 struct aa_profile *aa_unpack(void *udata, size_t size, const char **ns)
678 {
679 	struct aa_profile *profile = NULL;
680 	int error;
681 	struct aa_ext e = {
682 		.start = udata,
683 		.end = udata + size,
684 		.pos = udata,
685 	};
686 
687 	error = verify_header(&e, ns);
688 	if (error)
689 		return ERR_PTR(error);
690 
691 	profile = unpack_profile(&e);
692 	if (IS_ERR(profile))
693 		return profile;
694 
695 	error = verify_profile(profile);
696 	if (error) {
697 		aa_put_profile(profile);
698 		profile = ERR_PTR(error);
699 	}
700 
701 	/* return refcount */
702 	return profile;
703 }
704