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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_ctx and
* the aa_task_ctx.label, both of which are required and are not allowed
* to be NULL. The aa_task_ctx is not reference counted and is unique
* to each cred (which is reference count). The label pointed to by
* the task_ctx 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_ctx
* @flags: gfp flags for allocation
*
* Returns: allocated buffer or NULL on failure
*/
struct aa_task_ctx *aa_alloc_task_context(gfp_t flags)
{
return kzalloc(sizeof(struct aa_task_ctx), flags);
}
/**
* aa_free_task_context - free a task_ctx
* @ctx: task_ctx to free (MAYBE NULL)
*/
void aa_free_task_context(struct aa_task_ctx *ctx)
{
if (ctx) {
aa_put_label(ctx->label);
aa_put_label(ctx->previous);
aa_put_label(ctx->onexec);
kzfree(ctx);
}
}
/**
* 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_ctx *new, const struct aa_task_ctx *old)
{
*new = *old;
aa_get_label(new->label);
aa_get_label(new->previous);
aa_get_label(new->onexec);
}
/**
* aa_get_task_label - Get another task's label
* @task: task to query (NOT NULL)
*
* Returns: counted reference to @task's label
*/
struct aa_label *aa_get_task_label(struct task_struct *task)
{
struct aa_label *p;
rcu_read_lock();
p = aa_get_newest_label(__aa_task_raw_label(task));
rcu_read_unlock();
return p;
}
/**
* aa_replace_current_label - replace the current tasks label
* @label: new label (NOT NULL)
*
* Returns: 0 or error on failure
*/
int aa_replace_current_label(struct aa_label *label)
{
struct aa_task_ctx *ctx = current_ctx();
struct cred *new;
AA_BUG(!label);
if (ctx->label == label)
return 0;
if (current_cred() != current_real_cred())
return -EBUSY;
new = prepare_creds();
if (!new)
return -ENOMEM;
ctx = cred_ctx(new);
if (unconfined(label) || (labels_ns(ctx->label) != labels_ns(label)))
/* if switching to unconfined or a different label namespace
* clear out context state
*/
aa_clear_task_ctx_trans(ctx);
/*
* be careful switching ctx->profile, when racing replacement it
* is possible that ctx->profile->proxy->profile is the reference
* keeping @profile valid, so make sure to get its reference before
* dropping the reference on ctx->profile
*/
aa_get_label(label);
aa_put_label(ctx->label);
ctx->label = label;
commit_creds(new);
return 0;
}
/**
* aa_set_current_onexec - set the tasks change_profile to happen onexec
* @label: system label to set at exec (MAYBE NULL to clear value)
* @stack: whether stacking should be done
* Returns: 0 or error on failure
*/
int aa_set_current_onexec(struct aa_label *label, bool stack)
{
struct aa_task_ctx *ctx;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
ctx = cred_ctx(new);
aa_get_label(label);
aa_clear_task_ctx_trans(ctx);
ctx->onexec = label;
ctx->token = stack;
commit_creds(new);
return 0;
}
/**
* aa_set_current_hat - set the current tasks hat
* @label: label 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_label *label, u64 token)
{
struct aa_task_ctx *ctx;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
AA_BUG(!label);
ctx = cred_ctx(new);
if (!ctx->previous) {
/* transfer refcount */
ctx->previous = ctx->label;
ctx->token = token;
} else if (ctx->token == token) {
aa_put_label(ctx->label);
} else {
/* previous_profile && ctx->token != token */
abort_creds(new);
return -EACCES;
}
ctx->label = aa_get_newest_label(label);
/* clear exec on switching context */
aa_put_label(ctx->onexec);
ctx->onexec = NULL;
commit_creds(new);
return 0;
}
/**
* aa_restore_previous_label - exit from hat context restoring previous label
* @token: the token that must be matched to exit hat context
*
* Attempt to return out of a hat to the previous label. The token
* must match the stored token value.
*
* Returns: 0 or error of failure
*/
int aa_restore_previous_label(u64 token)
{
struct aa_task_ctx *ctx;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
ctx = cred_ctx(new);
if (ctx->token != token) {
abort_creds(new);
return -EACCES;
}
/* ignore restores when there is no saved label */
if (!ctx->previous) {
abort_creds(new);
return 0;
}
aa_put_label(ctx->label);
ctx->label = aa_get_newest_label(ctx->previous);
AA_BUG(!ctx->label);
/* clear exec && prev information when restoring to previous context */
aa_clear_task_ctx_trans(ctx);
commit_creds(new);
return 0;
}
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