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_ctx and
  17  * the aa_task_ctx.profile, both of which are required and are not allowed
  18  * to be NULL.  The aa_task_ctx is not reference counted and is unique
  19  * to each cred (which is reference count).  The profile pointed to by
  20  * the task_ctx 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_ctx
  34  * @flags: gfp flags for allocation
  35  *
  36  * Returns: allocated buffer or NULL on failure
  37  */
  38 struct aa_task_ctx *aa_alloc_task_context(gfp_t flags)
  39 {
  40         return kzalloc(sizeof(struct aa_task_ctx), flags);
  41 }
  42
  43 /**
  44  * aa_free_task_context - free a task_ctx
  45  * @ctx: task_ctx to free (MAYBE NULL)
  46  */
  47 void aa_free_task_context(struct aa_task_ctx *ctx)
  48 {
  49         if (ctx) {
  50                 aa_put_profile(ctx->profile);
  51                 aa_put_profile(ctx->previous);
  52                 aa_put_profile(ctx->onexec);
  53
  54                 kzfree(ctx);
  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_ctx *new, const struct aa_task_ctx *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_ctx *ctx = current_ctx();
  97         struct cred *new;
  98         AA_BUG(!profile);
  99
 100         if (ctx->profile == profile)
 101                 return 0;
 102
 103         if (current_cred() != current_real_cred())
 104                 return -EBUSY;
 105
 106         new  = prepare_creds();
 107         if (!new)
 108                 return -ENOMEM;
 109
 110         ctx = cred_ctx(new);
 111         if (unconfined(profile) || (ctx->profile->ns != profile->ns))
 112                 /* if switching to unconfined or a different profile namespace
 113                  * clear out context state
 114                  */
 115                 aa_clear_task_ctx_trans(ctx);
 116
 117         /*
 118          * be careful switching ctx->profile, when racing replacement it
 119          * is possible that ctx->profile->proxy->profile is the reference
 120          * keeping @profile valid, so make sure to get its reference before
 121          * dropping the reference on ctx->profile
 122          */
 123         aa_get_profile(profile);
 124         aa_put_profile(ctx->profile);
 125         ctx->profile = profile;
 126
 127         commit_creds(new);
 128         return 0;
 129 }
 130
 131 /**
 132  * aa_set_current_onexec - set the tasks change_profile to happen onexec
 133  * @profile: system profile to set at exec  (MAYBE NULL to clear value)
 134  *
 135  * Returns: 0 or error on failure
 136  */
 137 int aa_set_current_onexec(struct aa_profile *profile)
 138 {
 139         struct aa_task_ctx *ctx;
 140         struct cred *new = prepare_creds();
 141         if (!new)
 142                 return -ENOMEM;
 143
 144         ctx = cred_ctx(new);
 145         aa_get_profile(profile);
 146         aa_put_profile(ctx->onexec);
 147         ctx->onexec = profile;
 148
 149         commit_creds(new);
 150         return 0;
 151 }
 152
 153 /**
 154  * aa_set_current_hat - set the current tasks hat
 155  * @profile: profile to set as the current hat  (NOT NULL)
 156  * @token: token value that must be specified to change from the hat
 157  *
 158  * Do switch of tasks hat.  If the task is currently in a hat
 159  * validate the token to match.
 160  *
 161  * Returns: 0 or error on failure
 162  */
 163 int aa_set_current_hat(struct aa_profile *profile, u64 token)
 164 {
 165         struct aa_task_ctx *ctx;
 166         struct cred *new = prepare_creds();
 167         if (!new)
 168                 return -ENOMEM;
 169         AA_BUG(!profile);
 170
 171         ctx = cred_ctx(new);
 172         if (!ctx->previous) {
 173                 /* transfer refcount */
 174                 ctx->previous = ctx->profile;
 175                 ctx->token = token;
 176         } else if (ctx->token == token) {
 177                 aa_put_profile(ctx->profile);
 178         } else {
 179                 /* previous_profile && ctx->token != token */
 180                 abort_creds(new);
 181                 return -EACCES;
 182         }
 183         ctx->profile = aa_get_newest_profile(profile);
 184         /* clear exec on switching context */
 185         aa_put_profile(ctx->onexec);
 186         ctx->onexec = NULL;
 187
 188         commit_creds(new);
 189         return 0;
 190 }
 191
 192 /**
 193  * aa_restore_previous_profile - exit from hat context restoring the profile
 194  * @token: the token that must be matched to exit hat context
 195  *
 196  * Attempt to return out of a hat to the previous profile.  The token
 197  * must match the stored token value.
 198  *
 199  * Returns: 0 or error of failure
 200  */
 201 int aa_restore_previous_profile(u64 token)
 202 {
 203         struct aa_task_ctx *ctx;
 204         struct cred *new = prepare_creds();
 205         if (!new)
 206                 return -ENOMEM;
 207
 208         ctx = cred_ctx(new);
 209         if (ctx->token != token) {
 210                 abort_creds(new);
 211                 return -EACCES;
 212         }
 213         /* ignore restores when there is no saved profile */
 214         if (!ctx->previous) {
 215                 abort_creds(new);
 216                 return 0;
 217         }
 218
 219         aa_put_profile(ctx->profile);
 220         ctx->profile = aa_get_newest_profile(ctx->previous);
 221         AA_BUG(!ctx->profile);
 222         /* clear exec && prev information when restoring to previous context */
 223         aa_clear_task_ctx_trans(ctx);
 224
 225         commit_creds(new);
 226         return 0;
 227 }