Root/security/apparmor/context.c

1/*
2 * AppArmor security module
3 *
4 * This file contains AppArmor functions used to manipulate object security
5 * contexts.
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 *
16 * AppArmor sets confinement on every task, via the the aa_task_cxt and
17 * the aa_task_cxt.profile, both of which are required and are not allowed
18 * to be NULL. The aa_task_cxt is not reference counted and is unique
19 * to each cred (which is reference count). The profile pointed to by
20 * the task_cxt is reference counted.
21 *
22 * TODO
23 * If a task uses change_hat it currently does not return to the old
24 * cred or task context but instead creates a new one. Ideally the task
25 * should return to the previous cred if it has not been modified.
26 *
27 */
28
29#include "include/context.h"
30#include "include/policy.h"
31
32/**
33 * aa_alloc_task_context - allocate a new task_cxt
34 * @flags: gfp flags for allocation
35 *
36 * Returns: allocated buffer or NULL on failure
37 */
38struct aa_task_cxt *aa_alloc_task_context(gfp_t flags)
39{
40    return kzalloc(sizeof(struct aa_task_cxt), flags);
41}
42
43/**
44 * aa_free_task_context - free a task_cxt
45 * @cxt: task_cxt to free (MAYBE NULL)
46 */
47void aa_free_task_context(struct aa_task_cxt *cxt)
48{
49    if (cxt) {
50        aa_put_profile(cxt->profile);
51        aa_put_profile(cxt->previous);
52        aa_put_profile(cxt->onexec);
53
54        kzfree(cxt);
55    }
56}
57
58/**
59 * aa_dup_task_context - duplicate a task context, incrementing reference counts
60 * @new: a blank task context (NOT NULL)
61 * @old: the task context to copy (NOT NULL)
62 */
63void aa_dup_task_context(struct aa_task_cxt *new, const struct aa_task_cxt *old)
64{
65    *new = *old;
66    aa_get_profile(new->profile);
67    aa_get_profile(new->previous);
68    aa_get_profile(new->onexec);
69}
70
71/**
72 * aa_replace_current_profile - replace the current tasks profiles
73 * @profile: new profile (NOT NULL)
74 *
75 * Returns: 0 or error on failure
76 */
77int aa_replace_current_profile(struct aa_profile *profile)
78{
79    struct aa_task_cxt *cxt = current_cred()->security;
80    struct cred *new;
81    BUG_ON(!profile);
82
83    if (cxt->profile == profile)
84        return 0;
85
86    new = prepare_creds();
87    if (!new)
88        return -ENOMEM;
89
90    cxt = new->security;
91    if (unconfined(profile) || (cxt->profile->ns != profile->ns)) {
92        /* if switching to unconfined or a different profile namespace
93         * clear out context state
94         */
95        aa_put_profile(cxt->previous);
96        aa_put_profile(cxt->onexec);
97        cxt->previous = NULL;
98        cxt->onexec = NULL;
99        cxt->token = 0;
100    }
101    /* be careful switching cxt->profile, when racing replacement it
102     * is possible that cxt->profile->replacedby is the reference keeping
103     * @profile valid, so make sure to get its reference before dropping
104     * the reference on cxt->profile */
105    aa_get_profile(profile);
106    aa_put_profile(cxt->profile);
107    cxt->profile = profile;
108
109    commit_creds(new);
110    return 0;
111}
112
113/**
114 * aa_set_current_onexec - set the tasks change_profile to happen onexec
115 * @profile: system profile to set at exec (MAYBE NULL to clear value)
116 *
117 * Returns: 0 or error on failure
118 */
119int aa_set_current_onexec(struct aa_profile *profile)
120{
121    struct aa_task_cxt *cxt;
122    struct cred *new = prepare_creds();
123    if (!new)
124        return -ENOMEM;
125
126    cxt = new->security;
127    aa_get_profile(profile);
128    aa_put_profile(cxt->onexec);
129    cxt->onexec = profile;
130
131    commit_creds(new);
132    return 0;
133}
134
135/**
136 * aa_set_current_hat - set the current tasks hat
137 * @profile: profile to set as the current hat (NOT NULL)
138 * @token: token value that must be specified to change from the hat
139 *
140 * Do switch of tasks hat. If the task is currently in a hat
141 * validate the token to match.
142 *
143 * Returns: 0 or error on failure
144 */
145int aa_set_current_hat(struct aa_profile *profile, u64 token)
146{
147    struct aa_task_cxt *cxt;
148    struct cred *new = prepare_creds();
149    if (!new)
150        return -ENOMEM;
151    BUG_ON(!profile);
152
153    cxt = new->security;
154    if (!cxt->previous) {
155        /* transfer refcount */
156        cxt->previous = cxt->profile;
157        cxt->token = token;
158    } else if (cxt->token == token) {
159        aa_put_profile(cxt->profile);
160    } else {
161        /* previous_profile && cxt->token != token */
162        abort_creds(new);
163        return -EACCES;
164    }
165    cxt->profile = aa_get_profile(aa_newest_version(profile));
166    /* clear exec on switching context */
167    aa_put_profile(cxt->onexec);
168    cxt->onexec = NULL;
169
170    commit_creds(new);
171    return 0;
172}
173
174/**
175 * aa_restore_previous_profile - exit from hat context restoring the profile
176 * @token: the token that must be matched to exit hat context
177 *
178 * Attempt to return out of a hat to the previous profile. The token
179 * must match the stored token value.
180 *
181 * Returns: 0 or error of failure
182 */
183int aa_restore_previous_profile(u64 token)
184{
185    struct aa_task_cxt *cxt;
186    struct cred *new = prepare_creds();
187    if (!new)
188        return -ENOMEM;
189
190    cxt = new->security;
191    if (cxt->token != token) {
192        abort_creds(new);
193        return -EACCES;
194    }
195    /* ignore restores when there is no saved profile */
196    if (!cxt->previous) {
197        abort_creds(new);
198        return 0;
199    }
200
201    aa_put_profile(cxt->profile);
202    cxt->profile = aa_newest_version(cxt->previous);
203    BUG_ON(!cxt->profile);
204    if (unlikely(cxt->profile != cxt->previous)) {
205        aa_get_profile(cxt->profile);
206        aa_put_profile(cxt->previous);
207    }
208    /* clear exec && prev information when restoring to previous context */
209    cxt->previous = NULL;
210    cxt->token = 0;
211    aa_put_profile(cxt->onexec);
212    cxt->onexec = NULL;
213
214    commit_creds(new);
215    return 0;
216}
217

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