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    Subject[PATCH 03/12] AppArmor: contexts used in attaching policy to system objects
    Date
    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>
    ---
    security/apparmor/context.c | 225 +++++++++++++++++++++++++++++++++++
    security/apparmor/include/context.h | 145 ++++++++++++++++++++++
    2 files changed, 370 insertions(+), 0 deletions(-)
    create mode 100644 security/apparmor/context.c
    create mode 100644 security/apparmor/include/context.h

    diff --git a/security/apparmor/context.c b/security/apparmor/context.c
    new file mode 100644
    index 0000000..823207d
    --- /dev/null
    +++ b/security/apparmor/context.c
    @@ -0,0 +1,225 @@
    +/*
    + * AppArmor security module
    + *
    + * This file contains AppArmor functions used to manipulate object security
    + * contexts.
    + *
    + * Copyright (C) 1998-2008 Novell/SUSE
    + * Copyright 2009 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.
    + */
    +
    +#include "include/context.h"
    +#include "include/policy.h"
    +
    +struct aa_task_context *aa_alloc_task_context(gfp_t flags)
    +{
    + return kzalloc(sizeof(struct aa_task_context), flags);
    +}
    +
    +void aa_free_task_context(struct aa_task_context *cxt)
    +{
    + if (cxt) {
    + aa_put_profile(cxt->sys.profile);
    + aa_put_profile(cxt->sys.previous);
    + aa_put_profile(cxt->sys.onexec);
    +
    + kzfree(cxt);
    + }
    +}
    +
    +/**
    + * aa_dup_task_context - duplicate a task context, incrementing reference counts
    + * @new: a blank task context
    + * @old: the task context to copy
    + */
    +void aa_dup_task_context(struct aa_task_context *new,
    + const struct aa_task_context *old)
    +{
    + *new = *old;
    + aa_get_profile(new->sys.profile);
    + aa_get_profile(new->sys.previous);
    + aa_get_profile(new->sys.onexec);
    +}
    +
    +/**
    + * aa_cred_policy - obtain cred's profiles
    + * @cred: cred to obtain profiles from
    + * @sys: return system profile
    + *
    + * does NOT increment reference count
    + */
    +void aa_cred_policy(const struct cred *cred, struct aa_profile **sys)
    +{
    + struct aa_task_context *cxt = cred->security;
    + BUG_ON(!cxt);
    + *sys = aa_confining_profile(cxt->sys.profile);
    +}
    +
    +/**
    + * aa_get_task_policy - get the cred with the task policy, and current profiles
    + * @task: task to get policy of
    + * @sys: return - pointer to system profile
    + *
    + * Returns: a refcounted task cred
    + *
    + * Only gets the cred ref count which has ref counts on the profiles returned
    + */
    +struct cred *aa_get_task_policy(const struct task_struct *task,
    + struct aa_profile **sys)
    +{
    + struct cred *cred = get_task_cred(task);
    + aa_cred_policy(cred, sys);
    + return cred;
    +}
    +
    +/**
    + * replace_group - replace a context group profile
    + * @cgrp: profile
    + * @profile: profile to replace cxt group
    + *
    + * Replace context grouping profile reference with @profile
    + */
    +static void replace_group(struct aa_task_cxt_group *cgrp,
    + struct aa_profile *profile)
    +{
    + if (cgrp->profile == profile)
    + return;
    +
    + if (!profile || (profile->flags & PFLAG_UNCONFINED) ||
    + (cgrp->profile && cgrp->profile->ns != profile->ns)) {
    + aa_put_profile(cgrp->previous);
    + aa_put_profile(cgrp->onexec);
    + cgrp->previous = NULL;
    + cgrp->onexec = NULL;
    + cgrp->token = 0;
    + }
    + aa_put_profile(cgrp->profile);
    + cgrp->profile = aa_get_profile(profile);
    +}
    +
    +/**
    + * aa_replace_current_profiles - replace the current tasks profiles
    + * @sys: new system profile
    + *
    + * Returns: error on failure
    + */
    +int aa_replace_current_profiles(struct aa_profile *sys)
    +{
    + struct aa_task_context *cxt;
    + struct cred *new = prepare_creds();
    + if (!new)
    + return -ENOMEM;
    +
    + cxt = new->security;
    + replace_group(&cxt->sys, sys);
    + /* todo add user group */
    +
    + commit_creds(new);
    + return 0;
    +}
    +
    +/**
    + * aa_set_current_onexec - set the tasks change_profile to happen onexec
    + * @sys: system profile to set at exec
    + *
    + * Returns: error on failure
    + */
    +int aa_set_current_onexec(struct aa_profile *sys)
    +{
    + struct aa_task_context *cxt;
    + struct cred *new = prepare_creds();
    + if (!new)
    + return -ENOMEM;
    +
    + cxt = new->security;
    + aa_put_profile(cxt->sys.onexec);
    + cxt->sys.onexec = aa_get_profile(sys);
    +
    + commit_creds(new);
    + return 0;
    +}
    +
    +/**
    + * aa_set_current_hat - set the current tasks hat
    + * @profile: profile to set as the current hat
    + * @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: error on failure
    + */
    +int aa_set_current_hat(struct aa_profile *profile, u64 token)
    +{
    + struct aa_task_context *cxt;
    + struct cred *new = prepare_creds();
    + if (!new)
    + return -ENOMEM;
    +
    + cxt = new->security;
    + if (!cxt->sys.previous) {
    + cxt->sys.previous = cxt->sys.profile;
    + cxt->sys.token = token;
    + } else if (cxt->sys.token == token) {
    + aa_put_profile(cxt->sys.profile);
    + } else {
    + /* previous_profile && cxt->token != token */
    + abort_creds(new);
    + return -EACCES;
    + }
    + cxt->sys.profile = aa_get_profile(profile);
    + /* clear exec on switching context */
    + aa_put_profile(cxt->sys.onexec);
    + cxt->sys.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: error of failure
    + */
    +int aa_restore_previous_profile(u64 token)
    +{
    + struct aa_task_context *cxt;
    + struct cred *new = prepare_creds();
    + if (!new)
    + return -ENOMEM;
    +
    + cxt = new->security;
    + if (cxt->sys.token != token) {
    + abort_creds(new);
    + return -EACCES;
    + }
    + /* ignore restores when there is no saved profile */
    + if (!cxt->sys.previous) {
    + abort_creds(new);
    + return 0;
    + }
    +
    + aa_put_profile(cxt->sys.profile);
    + cxt->sys.profile = aa_profile_newest(cxt->sys.previous);
    + if (unlikely(cxt->sys.profile != cxt->sys.previous)) {
    + aa_get_profile(cxt->sys.profile);
    + aa_put_profile(cxt->sys.previous);
    + }
    + /* clear exec && prev information when restoring to previous context */
    + cxt->sys.previous = NULL;
    + cxt->sys.token = 0;
    + aa_put_profile(cxt->sys.onexec);
    + cxt->sys.onexec = NULL;
    +
    + commit_creds(new);
    + return 0;
    +}
    diff --git a/security/apparmor/include/context.h b/security/apparmor/include/context.h
    new file mode 100644
    index 0000000..ffc83c6
    --- /dev/null
    +++ b/security/apparmor/include/context.h
    @@ -0,0 +1,145 @@
    +/*
    + * AppArmor security module
    + *
    + * This file contains AppArmor contexts used to associate "labels" to objects.
    + *
    + * Copyright (C) 1998-2008 Novell/SUSE
    + * Copyright 2009 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.
    + */
    +
    +#ifndef __AA_CONTEXT_H
    +#define __AA_CONTEXT_H
    +
    +#include <linux/cred.h>
    +#include <linux/slab.h>
    +#include <linux/sched.h>
    +
    +#include "policy.h"
    +
    +/* struct aa_file_cxt - the AppArmor context the file was opened in
    + * @profile: the profile the file was opened under
    + * @perms: the permission the file was opened with
    + */
    +struct aa_file_cxt {
    + struct aa_profile *profile;
    + u16 allowed;
    +};
    +
    +static inline struct aa_file_cxt *aa_alloc_file_context(gfp_t gfp)
    +{
    + return kzalloc(sizeof(struct aa_file_cxt), gfp);
    +}
    +
    +static inline void aa_free_file_context(struct aa_file_cxt *cxt)
    +{
    + aa_put_profile(cxt->profile);
    + kzfree(cxt);
    +}
    +
    +/* struct aa_task_cxt_group - a grouping label data for confined tasks
    + * @profile: the current profile
    + * @exec: profile to transition to on next exec
    + * @previous: profile the task may return to
    + * @token: magic value the task must know for returning to @previous_profile
    + *
    + * Contains the task's current profile (which could change due to
    + * change_hat). Plus the hat_magic needed during change_hat.
    + */
    +struct aa_task_cxt_group {
    + struct aa_profile *profile;
    + struct aa_profile *onexec;
    + struct aa_profile *previous;
    + u64 token;
    +};
    +
    +/**
    + * struct aa_task_context - primary label for confined tasks
    + * @sys: the system labeling for the task
    + *
    + * A task is confined by the intersection of its system and user profiles
    + */
    +struct aa_task_context {
    + struct aa_task_cxt_group sys;
    +};
    +
    +struct aa_task_context *aa_alloc_task_context(gfp_t flags);
    +void aa_free_task_context(struct aa_task_context *cxt);
    +void aa_dup_task_context(struct aa_task_context *new,
    + const struct aa_task_context *old);
    +void aa_cred_policy(const struct cred *cred, struct aa_profile **sys);
    +struct cred *aa_get_task_policy(const struct task_struct *task,
    + struct aa_profile **sys);
    +int aa_replace_current_profiles(struct aa_profile *sys);
    +void aa_put_task_policy(struct cred *cred);
    +int aa_set_current_onexec(struct aa_profile *sys);
    +int aa_set_current_hat(struct aa_profile *profile, u64 token);
    +int aa_restore_previous_profile(u64 cookie);
    +
    +static inline struct aa_task_context *__aa_task_cxt(struct task_struct *task)
    +{
    + return __task_cred(task)->security;
    +}
    +
    +/**
    + * __aa_task_is_confined - determine if @task has any confinement
    + * @task: task to check confinement of
    + *
    + * If @task != current needs to be in RCU safe critical section
    + */
    +static inline int __aa_task_is_confined(struct task_struct *task)
    +{
    + struct aa_task_context *cxt;
    + int rc = 1;
    +
    + cxt = __aa_task_cxt(task);
    + if (!cxt || (cxt->sys.profile->flags & PFLAG_UNCONFINED))
    + rc = 0;
    +
    + return rc;
    +}
    +
    +static inline const struct cred *aa_current_policy(struct aa_profile **sys)
    +{
    + const struct cred *cred = current_cred();
    + struct aa_task_context *cxt = cred->security;
    + BUG_ON(!cxt);
    + *sys = aa_confining_profile(cxt->sys.profile);
    +
    + return cred;
    +}
    +
    +static inline const struct cred *aa_current_policy_wupd(struct aa_profile **sys)
    +{
    + const struct cred *cred = current_cred();
    + struct aa_task_context *cxt = cred->security;
    + BUG_ON(!cxt);
    +
    + *sys = aa_profile_newest(cxt->sys.profile);
    + if (unlikely((cxt->sys.profile != *sys)))
    + aa_replace_current_profiles(*sys);
    + *sys = aa_filter_profile(*sys);
    +
    + return cred;
    +}
    +
    +static inline struct aa_profile *aa_current_profile(void)
    +{
    + const struct cred *cred = current_cred();
    + struct aa_task_context *cxt = cred->security;
    + BUG_ON(!cxt);
    + return aa_confining_profile(cxt->sys.profile);
    +}
    +
    +static inline struct aa_profile *aa_current_profile_wupd(void)
    +{
    + struct aa_profile *p;
    + aa_current_policy_wupd(&p);
    + return p;
    +}
    +
    +#endif /* __AA_CONTEXT_H */
    --
    1.6.3.3


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