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  */
  38 struct 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  */
  47 void 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  */
  63 void 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_get_task_profile - Get another task's profile
  73  * @task: task to query  (NOT NULL)
  74  *
  75  * Returns: counted reference to @task's profile
  76  */
  77 struct aa_profile *aa_get_task_profile(struct task_struct *task)
  78 {
  79         struct aa_profile *p;
  80
  81         rcu_read_lock();
  82         p = aa_get_profile(__aa_task_profile(task));
  83         rcu_read_unlock();
  84
  85         return p;
  86 }
  87
  88 /**
  89  * aa_replace_current_profile - replace the current tasks profiles
  90  * @profile: new profile  (NOT NULL)
  91  *
  92  * Returns: 0 or error on failure
  93  */
  94 int aa_replace_current_profile(struct aa_profile *profile)
  95 {
  96         struct aa_task_cxt *cxt = current_cxt();
  97         struct cred *new;
  98         BUG_ON(!profile);
  99
 100         if (cxt->profile == profile)
 101                 return 0;
 102
 103         new  = prepare_creds();
 104         if (!new)
 105                 return -ENOMEM;
 106
 107         cxt = cred_cxt(new);
 108         if (unconfined(profile) || (cxt->profile->ns != profile->ns))
 109                 /* if switching to unconfined or a different profile namespace
 110                  * clear out context state
 111                  */
 112                 aa_clear_task_cxt_trans(cxt);
 113
 114         /* be careful switching cxt->profile, when racing replacement it
 115          * is possible that cxt->profile->replacedby->profile is the reference
 116          * keeping @profile valid, so make sure to get its reference before
 117          * dropping the reference on cxt->profile */
 118         aa_get_profile(profile);
 119         aa_put_profile(cxt->profile);
 120         cxt->profile = profile;
 121
 122         commit_creds(new);
 123         return 0;
 124 }
 125
 126 /**
 127  * aa_set_current_onexec - set the tasks change_profile to happen onexec
 128  * @profile: system profile to set at exec  (MAYBE NULL to clear value)
 129  *
 130  * Returns: 0 or error on failure
 131  */
 132 int aa_set_current_onexec(struct aa_profile *profile)
 133 {
 134         struct aa_task_cxt *cxt;
 135         struct cred *new = prepare_creds();
 136         if (!new)
 137                 return -ENOMEM;
 138
 139         cxt = cred_cxt(new);
 140         aa_get_profile(profile);
 141         aa_put_profile(cxt->onexec);
 142         cxt->onexec = profile;
 143
 144         commit_creds(new);
 145         return 0;
 146 }
 147
 148 /**
 149  * aa_set_current_hat - set the current tasks hat
 150  * @profile: profile to set as the current hat  (NOT NULL)
 151  * @token: token value that must be specified to change from the hat
 152  *
 153  * Do switch of tasks hat.  If the task is currently in a hat
 154  * validate the token to match.
 155  *
 156  * Returns: 0 or error on failure
 157  */
 158 int aa_set_current_hat(struct aa_profile *profile, u64 token)
 159 {
 160         struct aa_task_cxt *cxt;
 161         struct cred *new = prepare_creds();
 162         if (!new)
 163                 return -ENOMEM;
 164         BUG_ON(!profile);
 165
 166         cxt = cred_cxt(new);
 167         if (!cxt->previous) {
 168                 /* transfer refcount */
 169                 cxt->previous = cxt->profile;
 170                 cxt->token = token;
 171         } else if (cxt->token == token) {
 172                 aa_put_profile(cxt->profile);
 173         } else {
 174                 /* previous_profile && cxt->token != token */
 175                 abort_creds(new);
 176                 return -EACCES;
 177         }
 178         cxt->profile = aa_get_newest_profile(profile);
 179         /* clear exec on switching context */
 180         aa_put_profile(cxt->onexec);
 181         cxt->onexec = NULL;
 182
 183         commit_creds(new);
 184         return 0;
 185 }
 186
 187 /**
 188  * aa_restore_previous_profile - exit from hat context restoring the profile
 189  * @token: the token that must be matched to exit hat context
 190  *
 191  * Attempt to return out of a hat to the previous profile.  The token
 192  * must match the stored token value.
 193  *
 194  * Returns: 0 or error of failure
 195  */
 196 int aa_restore_previous_profile(u64 token)
 197 {
 198         struct aa_task_cxt *cxt;
 199         struct cred *new = prepare_creds();
 200         if (!new)
 201                 return -ENOMEM;
 202
 203         cxt = cred_cxt(new);
 204         if (cxt->token != token) {
 205                 abort_creds(new);
 206                 return -EACCES;
 207         }
 208         /* ignore restores when there is no saved profile */
 209         if (!cxt->previous) {
 210                 abort_creds(new);
 211                 return 0;
 212         }
 213
 214         aa_put_profile(cxt->profile);
 215         cxt->profile = aa_get_newest_profile(cxt->previous);
 216         BUG_ON(!cxt->profile);
 217         /* clear exec && prev information when restoring to previous context */
 218         aa_clear_task_cxt_trans(cxt);
 219
 220         commit_creds(new);
 221         return 0;
 222 }