Root/security/apparmor/policy_unpack.c

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
41enum 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 */
62struct 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 */
70static 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 */
92static 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 */
109static 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 */
121static 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 */
137static 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 */
163static 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
188fail:
189    e->pos = pos;
190    return 0;
191}
192
193static 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
206static 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
219static 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
232static 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
249static 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
266fail:
267    e->pos = pos;
268    return 0;
269}
270
271static 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 */
297static 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 */
320static 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
352fail:
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 */
364static 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
421fail:
422    aa_free_domain_entries(&profile->file.trans);
423    e->pos = pos;
424    return 0;
425}
426
427static 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
456fail:
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 */
467static 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
582fail:
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 */
600static 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
623static 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 */
634static 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 */
652static 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 */
677struct 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

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