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AppArmor: contexts used in attaching policy to system objects

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AppArmor contexts attach profiles and state to tasks, files, etc. when
a direct profile reference is not sufficient.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
John Johansen 2010-07-29 14:47:59 -07:00 • committed by James Morris
parent 67012e8209
commit c75afcd153
2 changed files with 370 additions and 0 deletions
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216
security/apparmor/context.c Normal file
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/*
* AppArmor security module
*
* This file contains AppArmor functions used to manipulate object security
* contexts.
*
* Copyright (C) 1998-2008 Novell/SUSE
* Copyright 2009-2010 Canonical Ltd.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*
*
* AppArmor sets confinement on every task, via the the aa_task_cxt and
* the aa_task_cxt.profile, both of which are required and are not allowed
* to be NULL. The aa_task_cxt is not reference counted and is unique
* to each cred (which is reference count). The profile pointed to by
* the task_cxt is reference counted.
*
* TODO
* If a task uses change_hat it currently does not return to the old
* cred or task context but instead creates a new one. Ideally the task
* should return to the previous cred if it has not been modified.
*
*/
#include "include/context.h"
#include "include/policy.h"
/**
* aa_alloc_task_context - allocate a new task_cxt
* @flags: gfp flags for allocation
*
* Returns: allocated buffer or NULL on failure
*/
struct aa_task_cxt *aa_alloc_task_context(gfp_t flags)
{
return kzalloc(sizeof(struct aa_task_cxt), flags);
}
/**
* aa_free_task_context - free a task_cxt
* @cxt: task_cxt to free (MAYBE NULL)
*/
void aa_free_task_context(struct aa_task_cxt *cxt)
{
if (cxt) {
aa_put_profile(cxt->profile);
aa_put_profile(cxt->previous);
aa_put_profile(cxt->onexec);
kzfree(cxt);
}
}
/**
* aa_dup_task_context - duplicate a task context, incrementing reference counts
* @new: a blank task context (NOT NULL)
* @old: the task context to copy (NOT NULL)
*/
void aa_dup_task_context(struct aa_task_cxt *new, const struct aa_task_cxt *old)
{
*new = *old;
aa_get_profile(new->profile);
aa_get_profile(new->previous);
aa_get_profile(new->onexec);
}
/**
* aa_replace_current_profile - replace the current tasks profiles
* @profile: new profile (NOT NULL)
*
* Returns: 0 or error on failure
*/
int aa_replace_current_profile(struct aa_profile *profile)
{
struct aa_task_cxt *cxt = current_cred()->security;
struct cred *new;
BUG_ON(!profile);
if (cxt->profile == profile)
return 0;
new = prepare_creds();
if (!new)
return -ENOMEM;
cxt = new->security;
if (unconfined(profile) || (cxt->profile->ns != profile->ns)) {
/* if switching to unconfined or a different profile namespace
* clear out context state
*/
aa_put_profile(cxt->previous);
aa_put_profile(cxt->onexec);
cxt->previous = NULL;
cxt->onexec = NULL;
cxt->token = 0;
}
/* be careful switching cxt->profile, when racing replacement it
* is possible that cxt->profile->replacedby is the reference keeping
* @profile valid, so make sure to get its reference before dropping
* the reference on cxt->profile */
aa_get_profile(profile);
aa_put_profile(cxt->profile);
cxt->profile = profile;
commit_creds(new);
return 0;
}
/**
* aa_set_current_onexec - set the tasks change_profile to happen onexec
* @profile: system profile to set at exec (MAYBE NULL to clear value)
*
* Returns: 0 or error on failure
*/
int aa_set_current_onexec(struct aa_profile *profile)
{
struct aa_task_cxt *cxt;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
cxt = new->security;
aa_get_profile(profile);
aa_put_profile(cxt->onexec);
cxt->onexec = profile;
commit_creds(new);
return 0;
}
/**
* aa_set_current_hat - set the current tasks hat
* @profile: profile to set as the current hat (NOT NULL)
* @token: token value that must be specified to change from the hat
*
* Do switch of tasks hat. If the task is currently in a hat
* validate the token to match.
*
* Returns: 0 or error on failure
*/
int aa_set_current_hat(struct aa_profile *profile, u64 token)
{
struct aa_task_cxt *cxt;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
BUG_ON(!profile);
cxt = new->security;
if (!cxt->previous) {
/* transfer refcount */
cxt->previous = cxt->profile;
cxt->token = token;
} else if (cxt->token == token) {
aa_put_profile(cxt->profile);
} else {
/* previous_profile && cxt->token != token */
abort_creds(new);
return -EACCES;
}
cxt->profile = aa_get_profile(aa_newest_version(profile));
/* clear exec on switching context */
aa_put_profile(cxt->onexec);
cxt->onexec = NULL;
commit_creds(new);
return 0;
}
/**
* aa_restore_previous_profile - exit from hat context restoring the profile
* @token: the token that must be matched to exit hat context
*
* Attempt to return out of a hat to the previous profile. The token
* must match the stored token value.
*
* Returns: 0 or error of failure
*/
int aa_restore_previous_profile(u64 token)
{
struct aa_task_cxt *cxt;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
cxt = new->security;
if (cxt->token != token) {
abort_creds(new);
return -EACCES;
}
/* ignore restores when there is no saved profile */
if (!cxt->previous) {
abort_creds(new);
return 0;
}
aa_put_profile(cxt->profile);
cxt->profile = aa_newest_version(cxt->previous);
BUG_ON(!cxt->profile);
if (unlikely(cxt->profile != cxt->previous)) {
aa_get_profile(cxt->profile);
aa_put_profile(cxt->previous);
}
/* clear exec && prev information when restoring to previous context */
cxt->previous = NULL;
cxt->token = 0;
aa_put_profile(cxt->onexec);
cxt->onexec = NULL;
commit_creds(new);
return 0;
}