Linux 4.13.16

[linux/fpc-iii.git] / security / apparmor / domain.c

/*
 * AppArmor security module
 *
 * This file contains AppArmor policy attachment and domain transitions
 *
 * Copyright (C) 2002-2008 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.
 */

#include <linux/errno.h>
#include <linux/fdtable.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>
#include <linux/personality.h>

#include "include/audit.h"
#include "include/apparmorfs.h"
#include "include/context.h"
#include "include/domain.h"
#include "include/file.h"
#include "include/ipc.h"
#include "include/match.h"
#include "include/path.h"
#include "include/policy.h"
#include "include/policy_ns.h"

/**
 * aa_free_domain_entries - free entries in a domain table
 * @domain: the domain table to free  (MAYBE NULL)
 */
void aa_free_domain_entries(struct aa_domain *domain)
{
        int i;
        if (domain) {
                if (!domain->table)
                        return;

                for (i = 0; i < domain->size; i++)
                        kzfree(domain->table[i]);
                kzfree(domain->table);
                domain->table = NULL;
        }
}

/**
 * may_change_ptraced_domain - check if can change profile on ptraced task
 * @to_label: profile to change to  (NOT NULL)
 * @info: message if there is an error
 *
 * Check if current is ptraced and if so if the tracing task is allowed
 * to trace the new domain
 *
 * Returns: %0 or error if change not allowed
 */
static int may_change_ptraced_domain(struct aa_label *to_label,
                                     const char **info)
{
        struct task_struct *tracer;
        struct aa_label *tracerl = NULL;
        int error = 0;

        rcu_read_lock();
        tracer = ptrace_parent(current);
        if (tracer)
                /* released below */
                tracerl = aa_get_task_label(tracer);

        /* not ptraced */
        if (!tracer || unconfined(tracerl))
                goto out;

        error = aa_may_ptrace(tracerl, to_label, PTRACE_MODE_ATTACH);

out:
        rcu_read_unlock();
        aa_put_label(tracerl);

        if (error)
                *info = "ptrace prevents transition";
        return error;
}

/**** TODO: dedup to aa_label_match - needs perm and dfa, merging
 * specifically this is an exact copy of aa_label_match except
 * aa_compute_perms is replaced with aa_compute_fperms
 * and policy.dfa with file.dfa
 ****/
/* match a profile and its associated ns component if needed
 * Assumes visibility test has already been done.
 * If a subns profile is not to be matched should be prescreened with
 * visibility test.
 */
static inline unsigned int match_component(struct aa_profile *profile,
                                           struct aa_profile *tp,
                                           bool stack, unsigned int state)
{
        const char *ns_name;

        if (stack)
                state = aa_dfa_match(profile->file.dfa, state, "&");
        if (profile->ns == tp->ns)
                return aa_dfa_match(profile->file.dfa, state, tp->base.hname);

        /* try matching with namespace name and then profile */
        ns_name = aa_ns_name(profile->ns, tp->ns, true);
        state = aa_dfa_match_len(profile->file.dfa, state, ":", 1);
        state = aa_dfa_match(profile->file.dfa, state, ns_name);
        state = aa_dfa_match_len(profile->file.dfa, state, ":", 1);
        return aa_dfa_match(profile->file.dfa, state, tp->base.hname);
}

/**
 * label_compound_match - find perms for full compound label
 * @profile: profile to find perms for
 * @label: label to check access permissions for
 * @stack: whether this is a stacking request
 * @start: state to start match in
 * @subns: whether to do permission checks on components in a subns
 * @request: permissions to request
 * @perms: perms struct to set
 *
 * Returns: 0 on success else ERROR
 *
 * For the label A//&B//&C this does the perm match for A//&B//&C
 * @perms should be preinitialized with allperms OR a previous permission
 *        check to be stacked.
 */
static int label_compound_match(struct aa_profile *profile,
                                struct aa_label *label, bool stack,
                                unsigned int state, bool subns, u32 request,
                                struct aa_perms *perms)
{
        struct aa_profile *tp;
        struct label_it i;
        struct path_cond cond = { };

        /* find first subcomponent that is visible */
        label_for_each(i, label, tp) {
                if (!aa_ns_visible(profile->ns, tp->ns, subns))
                        continue;
                state = match_component(profile, tp, stack, state);
                if (!state)
                        goto fail;
                goto next;
        }

        /* no component visible */
        *perms = allperms;
        return 0;

next:
        label_for_each_cont(i, label, tp) {
                if (!aa_ns_visible(profile->ns, tp->ns, subns))
                        continue;
                state = aa_dfa_match(profile->file.dfa, state, "//&");
                state = match_component(profile, tp, false, state);
                if (!state)
                        goto fail;
        }
        *perms = aa_compute_fperms(profile->file.dfa, state, &cond);
        aa_apply_modes_to_perms(profile, perms);
        if ((perms->allow & request) != request)
                return -EACCES;

        return 0;

fail:
        *perms = nullperms;
        return -EACCES;
}

/**
 * label_components_match - find perms for all subcomponents of a label
 * @profile: profile to find perms for
 * @label: label to check access permissions for
 * @stack: whether this is a stacking request
 * @start: state to start match in
 * @subns: whether to do permission checks on components in a subns
 * @request: permissions to request
 * @perms: an initialized perms struct to add accumulation to
 *
 * Returns: 0 on success else ERROR
 *
 * For the label A//&B//&C this does the perm match for each of A and B and C
 * @perms should be preinitialized with allperms OR a previous permission
 *        check to be stacked.
 */
static int label_components_match(struct aa_profile *profile,
                                  struct aa_label *label, bool stack,
                                  unsigned int start, bool subns, u32 request,
                                  struct aa_perms *perms)
{
        struct aa_profile *tp;
        struct label_it i;
        struct aa_perms tmp;
        struct path_cond cond = { };
        unsigned int state = 0;

        /* find first subcomponent to test */
        label_for_each(i, label, tp) {
                if (!aa_ns_visible(profile->ns, tp->ns, subns))
                        continue;
                state = match_component(profile, tp, stack, start);
                if (!state)
                        goto fail;
                goto next;
        }

        /* no subcomponents visible - no change in perms */
        return 0;

next:
        tmp = aa_compute_fperms(profile->file.dfa, state, &cond);
        aa_apply_modes_to_perms(profile, &tmp);
        aa_perms_accum(perms, &tmp);
        label_for_each_cont(i, label, tp) {
                if (!aa_ns_visible(profile->ns, tp->ns, subns))
                        continue;
                state = match_component(profile, tp, stack, start);
                if (!state)
                        goto fail;
                tmp = aa_compute_fperms(profile->file.dfa, state, &cond);
                aa_apply_modes_to_perms(profile, &tmp);
                aa_perms_accum(perms, &tmp);
        }

        if ((perms->allow & request) != request)
                return -EACCES;

        return 0;

fail:
        *perms = nullperms;
        return -EACCES;
}

/**
 * label_match - do a multi-component label match
 * @profile: profile to match against (NOT NULL)
 * @label: label to match (NOT NULL)
 * @stack: whether this is a stacking request
 * @state: state to start in
 * @subns: whether to match subns components
 * @request: permission request
 * @perms: Returns computed perms (NOT NULL)
 *
 * Returns: the state the match finished in, may be the none matching state
 */
static int label_match(struct aa_profile *profile, struct aa_label *label,
                       bool stack, unsigned int state, bool subns, u32 request,
                       struct aa_perms *perms)
{
        int error;

        *perms = nullperms;
        error = label_compound_match(profile, label, stack, state, subns,
                                     request, perms);
        if (!error)
                return error;

        *perms = allperms;
        return label_components_match(profile, label, stack, state, subns,
                                      request, perms);
}

/******* end TODO: dedup *****/

/**
 * change_profile_perms - find permissions for change_profile
 * @profile: the current profile  (NOT NULL)
 * @target: label to transition to (NOT NULL)
 * @stack: whether this is a stacking request
 * @request: requested perms
 * @start: state to start matching in
 *
 *
 * Returns: permission set
 *
 * currently only matches full label A//&B//&C or individual components A, B, C
 * not arbitrary combinations. Eg. A//&B, C
 */
static int change_profile_perms(struct aa_profile *profile,
                                struct aa_label *target, bool stack,
                                u32 request, unsigned int start,
                                struct aa_perms *perms)
{
        if (profile_unconfined(profile)) {
                perms->allow = AA_MAY_CHANGE_PROFILE | AA_MAY_ONEXEC;
                perms->audit = perms->quiet = perms->kill = 0;
                return 0;
        }

        /* TODO: add profile in ns screening */
        return label_match(profile, target, stack, start, true, request, perms);
}

/**
 * __attach_match_ - find an attachment match
 * @name - to match against  (NOT NULL)
 * @head - profile list to walk  (NOT NULL)
 *
 * Do a linear search on the profiles in the list.  There is a matching
 * preference where an exact match is preferred over a name which uses
 * expressions to match, and matching expressions with the greatest
 * xmatch_len are preferred.
 *
 * Requires: @head not be shared or have appropriate locks held
 *
 * Returns: profile or NULL if no match found
 */
static struct aa_profile *__attach_match(const char *name,
                                         struct list_head *head)
{
        int len = 0;
        struct aa_profile *profile, *candidate = NULL;

        list_for_each_entry_rcu(profile, head, base.list) {
                if (profile->label.flags & FLAG_NULL)
                        continue;
                if (profile->xmatch && profile->xmatch_len > len) {
                        unsigned int state = aa_dfa_match(profile->xmatch,
                                                          DFA_START, name);
                        u32 perm = dfa_user_allow(profile->xmatch, state);
                        /* any accepting state means a valid match. */
                        if (perm & MAY_EXEC) {
                                candidate = profile;
                                len = profile->xmatch_len;
                        }
                } else if (!strcmp(profile->base.name, name))
                        /* exact non-re match, no more searching required */
                        return profile;
        }

        return candidate;
}

/**
 * find_attach - do attachment search for unconfined processes
 * @ns: the current namespace  (NOT NULL)
 * @list: list to search  (NOT NULL)
 * @name: the executable name to match against  (NOT NULL)
 *
 * Returns: label or NULL if no match found
 */
static struct aa_label *find_attach(struct aa_ns *ns, struct list_head *list,
                                    const char *name)
{
        struct aa_profile *profile;

        rcu_read_lock();
        profile = aa_get_profile(__attach_match(name, list));
        rcu_read_unlock();

        return profile ? &profile->label : NULL;
}

static const char *next_name(int xtype, const char *name)
{
        return NULL;
}

/**
 * x_table_lookup - lookup an x transition name via transition table
 * @profile: current profile (NOT NULL)
 * @xindex: index into x transition table
 * @name: returns: name tested to find label (NOT NULL)
 *
 * Returns: refcounted label, or NULL on failure (MAYBE NULL)
 */
static struct aa_label *x_table_lookup(struct aa_profile *profile, u32 xindex,
                                       const char **name)
{
        struct aa_label *label = NULL;
        u32 xtype = xindex & AA_X_TYPE_MASK;
        int index = xindex & AA_X_INDEX_MASK;

        AA_BUG(!name);

        /* index is guaranteed to be in range, validated at load time */
        /* TODO: move lookup parsing to unpack time so this is a straight
         *       index into the resultant label
         */
        for (*name = profile->file.trans.table[index]; !label && *name;
             *name = next_name(xtype, *name)) {
                if (xindex & AA_X_CHILD) {
                        struct aa_profile *new_profile;
                        /* release by caller */
                        new_profile = aa_find_child(profile, *name);
                        if (new_profile)
                                label = &new_profile->label;
                        continue;
                }
                label = aa_label_parse(&profile->label, *name, GFP_ATOMIC,
                                       true, false);
                if (IS_ERR(label))
                        label = NULL;
        }

        /* released by caller */

        return label;
}

/**
 * x_to_label - get target label for a given xindex
 * @profile: current profile  (NOT NULL)
 * @name: name to lookup (NOT NULL)
 * @xindex: index into x transition table
 * @lookupname: returns: name used in lookup if one was specified (NOT NULL)
 *
 * find label for a transition index
 *
 * Returns: refcounted label or NULL if not found available
 */
static struct aa_label *x_to_label(struct aa_profile *profile,
                                   const char *name, u32 xindex,
                                   const char **lookupname,
                                   const char **info)
{
        struct aa_label *new = NULL;
        struct aa_ns *ns = profile->ns;
        u32 xtype = xindex & AA_X_TYPE_MASK;
        const char *stack = NULL;

        switch (xtype) {
        case AA_X_NONE:
                /* fail exec unless ix || ux fallback - handled by caller */
                *lookupname = NULL;
                break;
        case AA_X_TABLE:
                /* TODO: fix when perm mapping done at unload */
                stack = profile->file.trans.table[xindex & AA_X_INDEX_MASK];
                if (*stack != '&') {
                        /* released by caller */
                        new = x_table_lookup(profile, xindex, lookupname);
                        stack = NULL;
                        break;
                }
                /* fall through to X_NAME */
        case AA_X_NAME:
                if (xindex & AA_X_CHILD)
                        /* released by caller */
                        new = find_attach(ns, &profile->base.profiles,
                                                name);
                else
                        /* released by caller */
                        new = find_attach(ns, &ns->base.profiles,
                                                name);
                *lookupname = name;
                break;
        }

        if (!new) {
                if (xindex & AA_X_INHERIT) {
                        /* (p|c|n)ix - don't change profile but do
                         * use the newest version
                         */
                        *info = "ix fallback";
                        /* no profile && no error */
                        new = aa_get_newest_label(&profile->label);
                } else if (xindex & AA_X_UNCONFINED) {
                        new = aa_get_newest_label(ns_unconfined(profile->ns));
                        *info = "ux fallback";
                }
        }

        if (new && stack) {
                /* base the stack on post domain transition */
                struct aa_label *base = new;

                new = aa_label_parse(base, stack, GFP_ATOMIC, true, false);
                if (IS_ERR(new))
                        new = NULL;
                aa_put_label(base);
        }

        /* released by caller */
        return new;
}

static struct aa_label *profile_transition(struct aa_profile *profile,
                                           const struct linux_binprm *bprm,
                                           char *buffer, struct path_cond *cond,
                                           bool *secure_exec)
{
        struct aa_label *new = NULL;
        const char *info = NULL, *name = NULL, *target = NULL;
        unsigned int state = profile->file.start;
        struct aa_perms perms = {};
        bool nonewprivs = false;
        int error = 0;

        AA_BUG(!profile);
        AA_BUG(!bprm);
        AA_BUG(!buffer);

        error = aa_path_name(&bprm->file->f_path, profile->path_flags, buffer,
                             &name, &info, profile->disconnected);
        if (error) {
                if (profile_unconfined(profile) ||
                    (profile->label.flags & FLAG_IX_ON_NAME_ERROR)) {
                        AA_DEBUG("name lookup ix on error");
                        error = 0;
                        new = aa_get_newest_label(&profile->label);
                }
                name = bprm->filename;
                goto audit;
        }

        if (profile_unconfined(profile)) {
                new = find_attach(profile->ns, &profile->ns->base.profiles,
                                  name);
                if (new) {
                        AA_DEBUG("unconfined attached to new label");
                        return new;
                }
                AA_DEBUG("unconfined exec no attachment");
                return aa_get_newest_label(&profile->label);
        }

        /* find exec permissions for name */
        state = aa_str_perms(profile->file.dfa, state, name, cond, &perms);
        if (perms.allow & MAY_EXEC) {
                /* exec permission determine how to transition */
                new = x_to_label(profile, name, perms.xindex, &target, &info);
                if (new && new->proxy == profile->label.proxy && info) {
                        /* hack ix fallback - improve how this is detected */
                        goto audit;
                } else if (!new) {
                        error = -EACCES;
                        info = "profile transition not found";
                        /* remove MAY_EXEC to audit as failure */
                        perms.allow &= ~MAY_EXEC;
                }
        } else if (COMPLAIN_MODE(profile)) {
                /* no exec permission - learning mode */
                struct aa_profile *new_profile = aa_new_null_profile(profile,
                                                              false, name,
                                                              GFP_ATOMIC);
                if (!new_profile) {
                        error = -ENOMEM;
                        info = "could not create null profile";
                } else {
                        error = -EACCES;
                        new = &new_profile->label;
                }
                perms.xindex |= AA_X_UNSAFE;
        } else
                /* fail exec */
                error = -EACCES;

        if (!new)
                goto audit;

        /* Policy has specified a domain transitions. if no_new_privs and
         * confined and not transitioning to the current domain fail.
         *
         * NOTE: Domain transitions from unconfined and to stritly stacked
         * subsets are allowed even when no_new_privs is set because this
         * aways results in a further reduction of permissions.
         */
        if ((bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) &&
            !profile_unconfined(profile) &&
            !aa_label_is_subset(new, &profile->label)) {
                error = -EPERM;
                info = "no new privs";
                nonewprivs = true;
                perms.allow &= ~MAY_EXEC;
                goto audit;
        }

        if (!(perms.xindex & AA_X_UNSAFE)) {
                if (DEBUG_ON) {
                        dbg_printk("apparmor: scrubbing environment variables"
                                   " for %s profile=", name);
                        aa_label_printk(new, GFP_ATOMIC);
                        dbg_printk("\n");
                }
                *secure_exec = true;
        }

audit:
        aa_audit_file(profile, &perms, OP_EXEC, MAY_EXEC, name, target, new,
                      cond->uid, info, error);
        if (!new || nonewprivs) {
                aa_put_label(new);
                return ERR_PTR(error);
        }

        return new;
}

static int profile_onexec(struct aa_profile *profile, struct aa_label *onexec,
                          bool stack, const struct linux_binprm *bprm,
                          char *buffer, struct path_cond *cond,
                          bool *secure_exec)
{
        unsigned int state = profile->file.start;
        struct aa_perms perms = {};
        const char *xname = NULL, *info = "change_profile onexec";
        int error = -EACCES;

        AA_BUG(!profile);
        AA_BUG(!onexec);
        AA_BUG(!bprm);
        AA_BUG(!buffer);

        if (profile_unconfined(profile)) {
                /* change_profile on exec already granted */
                /*
                 * NOTE: Domain transitions from unconfined are allowed
                 * even when no_new_privs is set because this aways results
                 * in a further reduction of permissions.
                 */
                return 0;
        }

        error = aa_path_name(&bprm->file->f_path, profile->path_flags, buffer,
                             &xname, &info, profile->disconnected);
        if (error) {
                if (profile_unconfined(profile) ||
                    (profile->label.flags & FLAG_IX_ON_NAME_ERROR)) {
                        AA_DEBUG("name lookup ix on error");
                        error = 0;
                }
                xname = bprm->filename;
                goto audit;
        }

        /* find exec permissions for name */
        state = aa_str_perms(profile->file.dfa, state, xname, cond, &perms);
        if (!(perms.allow & AA_MAY_ONEXEC)) {
                info = "no change_onexec valid for executable";
                goto audit;
        }
        /* test if this exec can be paired with change_profile onexec.
         * onexec permission is linked to exec with a standard pairing
         * exec\0change_profile
         */
        state = aa_dfa_null_transition(profile->file.dfa, state);
        error = change_profile_perms(profile, onexec, stack, AA_MAY_ONEXEC,
                                     state, &perms);
        if (error) {
                perms.allow &= ~AA_MAY_ONEXEC;
                goto audit;
        }
        /* Policy has specified a domain transitions. if no_new_privs and
         * confined and not transitioning to the current domain fail.
         *
         * NOTE: Domain transitions from unconfined and to stritly stacked
         * subsets are allowed even when no_new_privs is set because this
         * aways results in a further reduction of permissions.
         */
        if ((bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) &&
            !profile_unconfined(profile) &&
            !aa_label_is_subset(onexec, &profile->label)) {
                error = -EPERM;
                info = "no new privs";
                perms.allow &= ~AA_MAY_ONEXEC;
                goto audit;
        }

        if (!(perms.xindex & AA_X_UNSAFE)) {
                if (DEBUG_ON) {
                        dbg_printk("apparmor: scrubbing environment "
                                   "variables for %s label=", xname);
                        aa_label_printk(onexec, GFP_ATOMIC);
                        dbg_printk("\n");
                }
                *secure_exec = true;
        }

audit:
        return aa_audit_file(profile, &perms, OP_EXEC, AA_MAY_ONEXEC, xname,
                             NULL, onexec, cond->uid, info, error);
}

/* ensure none ns domain transitions are correctly applied with onexec */

static struct aa_label *handle_onexec(struct aa_label *label,
                                      struct aa_label *onexec, bool stack,
                                      const struct linux_binprm *bprm,
                                      char *buffer, struct path_cond *cond,
                                      bool *unsafe)
{
        struct aa_profile *profile;
        struct aa_label *new;
        int error;

        AA_BUG(!label);
        AA_BUG(!onexec);
        AA_BUG(!bprm);
        AA_BUG(!buffer);

        if (!stack) {
                error = fn_for_each_in_ns(label, profile,
                                profile_onexec(profile, onexec, stack,
                                               bprm, buffer, cond, unsafe));
                if (error)
                        return ERR_PTR(error);
                new = fn_label_build_in_ns(label, profile, GFP_ATOMIC,
                                aa_get_newest_label(onexec),
                                profile_transition(profile, bprm, buffer,
                                                   cond, unsafe));

        } else {
                /* TODO: determine how much we want to losen this */
                error = fn_for_each_in_ns(label, profile,
                                profile_onexec(profile, onexec, stack, bprm,
                                               buffer, cond, unsafe));
                if (error)
                        return ERR_PTR(error);
                new = fn_label_build_in_ns(label, profile, GFP_ATOMIC,
                                aa_label_merge(&profile->label, onexec,
                                               GFP_ATOMIC),
                                profile_transition(profile, bprm, buffer,
                                                   cond, unsafe));
        }

        if (new)
                return new;

        /* TODO: get rid of GLOBAL_ROOT_UID */
        error = fn_for_each_in_ns(label, profile,
                        aa_audit_file(profile, &nullperms, OP_CHANGE_ONEXEC,
                                      AA_MAY_ONEXEC, bprm->filename, NULL,
                                      onexec, GLOBAL_ROOT_UID,
                                      "failed to build target label", -ENOMEM));
        return ERR_PTR(error);
}

/**
 * apparmor_bprm_set_creds - set the new creds on the bprm struct
 * @bprm: binprm for the exec  (NOT NULL)
 *
 * Returns: %0 or error on failure
 *
 * TODO: once the other paths are done see if we can't refactor into a fn
 */
int apparmor_bprm_set_creds(struct linux_binprm *bprm)
{
        struct aa_task_ctx *ctx;
        struct aa_label *label, *new = NULL;
        struct aa_profile *profile;
        char *buffer = NULL;
        const char *info = NULL;
        int error = 0;
        bool unsafe = false;
        struct path_cond cond = {
                file_inode(bprm->file)->i_uid,
                file_inode(bprm->file)->i_mode
        };

        if (bprm->cred_prepared)
                return 0;

        ctx = cred_ctx(bprm->cred);
        AA_BUG(!ctx);

        label = aa_get_newest_label(ctx->label);

        /* buffer freed below, name is pointer into buffer */
        get_buffers(buffer);
        /* Test for onexec first as onexec override other x transitions. */
        if (ctx->onexec)
                new = handle_onexec(label, ctx->onexec, ctx->token,
                                    bprm, buffer, &cond, &unsafe);
        else
                new = fn_label_build(label, profile, GFP_ATOMIC,
                                profile_transition(profile, bprm, buffer,
                                                   &cond, &unsafe));

        AA_BUG(!new);
        if (IS_ERR(new)) {
                error = PTR_ERR(new);
                goto done;
        } else if (!new) {
                error = -ENOMEM;
                goto done;
        }

        /* TODO: Add ns level no_new_privs subset test */

        if (bprm->unsafe & LSM_UNSAFE_SHARE) {
                /* FIXME: currently don't mediate shared state */
                ;
        }

        if (bprm->unsafe & (LSM_UNSAFE_PTRACE)) {
                /* TODO: test needs to be profile of label to new */
                error = may_change_ptraced_domain(new, &info);
                if (error)
                        goto audit;
        }

        if (unsafe) {
                if (DEBUG_ON) {
                        dbg_printk("scrubbing environment variables for %s "
                                   "label=", bprm->filename);
                        aa_label_printk(new, GFP_ATOMIC);
                        dbg_printk("\n");
                }
                bprm->unsafe |= AA_SECURE_X_NEEDED;
        }

        if (label->proxy != new->proxy) {
                /* when transitioning clear unsafe personality bits */
                if (DEBUG_ON) {
                        dbg_printk("apparmor: clearing unsafe personality "
                                   "bits. %s label=", bprm->filename);
                        aa_label_printk(new, GFP_ATOMIC);
                        dbg_printk("\n");
                }
                bprm->per_clear |= PER_CLEAR_ON_SETID;
        }
        aa_put_label(ctx->label);
        /* transfer reference, released when ctx is freed */
        ctx->label = new;

done:
        /* clear out temporary/transitional state from the context */
        aa_clear_task_ctx_trans(ctx);

        aa_put_label(label);
        put_buffers(buffer);

        return error;

audit:
        error = fn_for_each(label, profile,
                        aa_audit_file(profile, &nullperms, OP_EXEC, MAY_EXEC,
                                      bprm->filename, NULL, new,
                                      file_inode(bprm->file)->i_uid, info,
                                      error));
        aa_put_label(new);
        goto done;
}

/**
 * apparmor_bprm_secureexec - determine if secureexec is needed
 * @bprm: binprm for exec  (NOT NULL)
 *
 * Returns: %1 if secureexec is needed else %0
 */
int apparmor_bprm_secureexec(struct linux_binprm *bprm)
{
        /* the decision to use secure exec is computed in set_creds
         * and stored in bprm->unsafe.
         */
        if (bprm->unsafe & AA_SECURE_X_NEEDED)
                return 1;

        return 0;
}

/*
 * Functions for self directed profile change
 */


/* helper fn for change_hat
 *
 * Returns: label for hat transition OR ERR_PTR.  Does NOT return NULL
 */
static struct aa_label *build_change_hat(struct aa_profile *profile,
                                         const char *name, bool sibling)
{
        struct aa_profile *root, *hat = NULL;
        const char *info = NULL;
        int error = 0;

        if (sibling && PROFILE_IS_HAT(profile)) {
                root = aa_get_profile_rcu(&profile->parent);
        } else if (!sibling && !PROFILE_IS_HAT(profile)) {
                root = aa_get_profile(profile);
        } else {
                info = "conflicting target types";
                error = -EPERM;
                goto audit;
        }

        hat = aa_find_child(root, name);
        if (!hat) {
                error = -ENOENT;
                if (COMPLAIN_MODE(profile)) {
                        hat = aa_new_null_profile(profile, true, name,
                                                  GFP_KERNEL);
                        if (!hat) {
                                info = "failed null profile create";
                                error = -ENOMEM;
                        }
                }
        }
        aa_put_profile(root);

audit:
        aa_audit_file(profile, &nullperms, OP_CHANGE_HAT, AA_MAY_CHANGEHAT,
                      name, hat ? hat->base.hname : NULL,
                      hat ? &hat->label : NULL, GLOBAL_ROOT_UID, NULL,
                      error);
        if (!hat || (error && error != -ENOENT))
                return ERR_PTR(error);
        /* if hat && error - complain mode, already audited and we adjust for
         * complain mode allow by returning hat->label
         */
        return &hat->label;
}

/* helper fn for changing into a hat
 *
 * Returns: label for hat transition or ERR_PTR. Does not return NULL
 */
static struct aa_label *change_hat(struct aa_label *label, const char *hats[],
                                   int count, int flags)
{
        struct aa_profile *profile, *root, *hat = NULL;
        struct aa_label *new;
        struct label_it it;
        bool sibling = false;
        const char *name, *info = NULL;
        int i, error;

        AA_BUG(!label);
        AA_BUG(!hats);
        AA_BUG(count < 1);

        if (PROFILE_IS_HAT(labels_profile(label)))
                sibling = true;

        /*find first matching hat */
        for (i = 0; i < count && !hat; i++) {
                name = hats[i];
                label_for_each_in_ns(it, labels_ns(label), label, profile) {
                        if (sibling && PROFILE_IS_HAT(profile)) {
                                root = aa_get_profile_rcu(&profile->parent);
                        } else if (!sibling && !PROFILE_IS_HAT(profile)) {
                                root = aa_get_profile(profile);
                        } else {        /* conflicting change type */
                                info = "conflicting targets types";
                                error = -EPERM;
                                goto fail;
                        }
                        hat = aa_find_child(root, name);
                        aa_put_profile(root);
                        if (!hat) {
                                if (!COMPLAIN_MODE(profile))
                                        goto outer_continue;
                                /* complain mode succeed as if hat */
                        } else if (!PROFILE_IS_HAT(hat)) {
                                info = "target not hat";
                                error = -EPERM;
                                aa_put_profile(hat);
                                goto fail;
                        }
                        aa_put_profile(hat);
                }
                /* found a hat for all profiles in ns */
                goto build;
outer_continue:
        ;
        }
        /* no hats that match, find appropriate error
         *
         * In complain mode audit of the failure is based off of the first
         * hat supplied.  This is done due how userspace interacts with
         * change_hat.
         */
        name = NULL;
        label_for_each_in_ns(it, labels_ns(label), label, profile) {
                if (!list_empty(&profile->base.profiles)) {
                        info = "hat not found";
                        error = -ENOENT;
                        goto fail;
                }
        }
        info = "no hats defined";
        error = -ECHILD;

fail:
        label_for_each_in_ns(it, labels_ns(label), label, profile) {
                /*
                 * no target as it has failed to be found or built
                 *
                 * change_hat uses probing and should not log failures
                 * related to missing hats
                 */
                /* TODO: get rid of GLOBAL_ROOT_UID */
                if (count > 1 || COMPLAIN_MODE(profile)) {
                        aa_audit_file(profile, &nullperms, OP_CHANGE_HAT,
                                      AA_MAY_CHANGEHAT, name, NULL, NULL,
                                      GLOBAL_ROOT_UID, info, error);
                }
        }
        return ERR_PTR(error);

build:
        new = fn_label_build_in_ns(label, profile, GFP_KERNEL,
                                   build_change_hat(profile, name, sibling),
                                   aa_get_label(&profile->label));
        if (!new) {
                info = "label build failed";
                error = -ENOMEM;
                goto fail;
        } /* else if (IS_ERR) build_change_hat has logged error so return new */

        return new;
}

/**
 * aa_change_hat - change hat to/from subprofile
 * @hats: vector of hat names to try changing into (MAYBE NULL if @count == 0)
 * @count: number of hat names in @hats
 * @token: magic value to validate the hat change
 * @flags: flags affecting behavior of the change
 *
 * Returns %0 on success, error otherwise.
 *
 * Change to the first profile specified in @hats that exists, and store
 * the @hat_magic in the current task context.  If the count == 0 and the
 * @token matches that stored in the current task context, return to the
 * top level profile.
 *
 * change_hat only applies to profiles in the current ns, and each profile
 * in the ns must make the same transition otherwise change_hat will fail.
 */
int aa_change_hat(const char *hats[], int count, u64 token, int flags)
{
        const struct cred *cred;
        struct aa_task_ctx *ctx;
        struct aa_label *label, *previous, *new = NULL, *target = NULL;
        struct aa_profile *profile;
        struct aa_perms perms = {};
        const char *info = NULL;
        int error = 0;

        /*
         * Fail explicitly requested domain transitions if no_new_privs.
         * There is no exception for unconfined as change_hat is not
         * available.
         */
        if (task_no_new_privs(current)) {
                /* not an apparmor denial per se, so don't log it */
                AA_DEBUG("no_new_privs - change_hat denied");
                return -EPERM;
        }

        /* released below */
        cred = get_current_cred();
        ctx = cred_ctx(cred);
        label = aa_get_newest_cred_label(cred);
        previous = aa_get_newest_label(ctx->previous);

        if (unconfined(label)) {
                info = "unconfined can not change_hat";
                error = -EPERM;
                goto fail;
        }

        if (count) {
                new = change_hat(label, hats, count, flags);
                AA_BUG(!new);
                if (IS_ERR(new)) {
                        error = PTR_ERR(new);
                        new = NULL;
                        /* already audited */
                        goto out;
                }

                error = may_change_ptraced_domain(new, &info);
                if (error)
                        goto fail;

                if (flags & AA_CHANGE_TEST)
                        goto out;

                target = new;
                error = aa_set_current_hat(new, token);
                if (error == -EACCES)
                        /* kill task in case of brute force attacks */
                        goto kill;
        } else if (previous && !(flags & AA_CHANGE_TEST)) {
                /* Return to saved label.  Kill task if restore fails
                 * to avoid brute force attacks
                 */
                target = previous;
                error = aa_restore_previous_label(token);
                if (error) {
                        if (error == -EACCES)
                                goto kill;
                        goto fail;
                }
        } /* else ignore @flags && restores when there is no saved profile */

out:
        aa_put_label(new);
        aa_put_label(previous);
        aa_put_label(label);
        put_cred(cred);

        return error;

kill:
        info = "failed token match";
        perms.kill = AA_MAY_CHANGEHAT;

fail:
        fn_for_each_in_ns(label, profile,
                aa_audit_file(profile, &perms, OP_CHANGE_HAT,
                              AA_MAY_CHANGEHAT, NULL, NULL, target,
                              GLOBAL_ROOT_UID, info, error));

        goto out;
}


static int change_profile_perms_wrapper(const char *op, const char *name,
                                        struct aa_profile *profile,
                                        struct aa_label *target, bool stack,
                                        u32 request, struct aa_perms *perms)
{
        const char *info = NULL;
        int error = 0;

        /*
         * Fail explicitly requested domain transitions when no_new_privs
         * and not unconfined OR the transition results in a stack on
         * the current label.
         * Stacking domain transitions and transitions from unconfined are
         * allowed even when no_new_privs is set because this aways results
         * in a reduction of permissions.
         */
        if (task_no_new_privs(current) && !stack &&
            !profile_unconfined(profile) &&
            !aa_label_is_subset(target, &profile->label)) {
                info = "no new privs";
                error = -EPERM;
        }

        if (!error)
                error = change_profile_perms(profile, target, stack, request,
                                             profile->file.start, perms);
        if (error)
                error = aa_audit_file(profile, perms, op, request, name,
                                      NULL, target, GLOBAL_ROOT_UID, info,
                                      error);

        return error;
}

/**
 * aa_change_profile - perform a one-way profile transition
 * @fqname: name of profile may include namespace (NOT NULL)
 * @onexec: whether this transition is to take place immediately or at exec
 * @flags: flags affecting change behavior
 *
 * Change to new profile @name.  Unlike with hats, there is no way
 * to change back.  If @name isn't specified the current profile name is
 * used.
 * If @onexec then the transition is delayed until
 * the next exec.
 *
 * Returns %0 on success, error otherwise.
 */
int aa_change_profile(const char *fqname, int flags)
{
        struct aa_label *label, *new = NULL, *target = NULL;
        struct aa_profile *profile;
        struct aa_perms perms = {};
        const char *info = NULL;
        const char *auditname = fqname;         /* retain leading & if stack */
        bool stack = flags & AA_CHANGE_STACK;
        int error = 0;
        char *op;
        u32 request;

        if (!fqname || !*fqname) {
                AA_DEBUG("no profile name");
                return -EINVAL;
        }

        if (flags & AA_CHANGE_ONEXEC) {
                request = AA_MAY_ONEXEC;
                if (stack)
                        op = OP_STACK_ONEXEC;
                else
                        op = OP_CHANGE_ONEXEC;
        } else {
                request = AA_MAY_CHANGE_PROFILE;
                if (stack)
                        op = OP_STACK;
                else
                        op = OP_CHANGE_PROFILE;
        }

        label = aa_get_current_label();

        if (*fqname == '&') {
                stack = true;
                /* don't have label_parse() do stacking */
                fqname++;
        }
        target = aa_label_parse(label, fqname, GFP_KERNEL, true, false);
        if (IS_ERR(target)) {
                struct aa_profile *tprofile;

                info = "label not found";
                error = PTR_ERR(target);
                target = NULL;
                /*
                 * TODO: fixme using labels_profile is not right - do profile
                 * per complain profile
                 */
                if ((flags & AA_CHANGE_TEST) ||
                    !COMPLAIN_MODE(labels_profile(label)))
                        goto audit;
                /* released below */
                tprofile = aa_new_null_profile(labels_profile(label), false,
                                               fqname, GFP_KERNEL);
                if (!tprofile) {
                        info = "failed null profile create";
                        error = -ENOMEM;
                        goto audit;
                }
                target = &tprofile->label;
                goto check;
        }

        /*
         * self directed transitions only apply to current policy ns
         * TODO: currently requiring perms for stacking and straight change
         *       stacking doesn't strictly need this. Determine how much
         *       we want to loosen this restriction for stacking
         *
         * if (!stack) {
         */
        error = fn_for_each_in_ns(label, profile,
                        change_profile_perms_wrapper(op, auditname,
                                                     profile, target, stack,
                                                     request, &perms));
        if (error)
                /* auditing done in change_profile_perms_wrapper */
                goto out;

        /* } */

check:
        /* check if tracing task is allowed to trace target domain */
        error = may_change_ptraced_domain(target, &info);
        if (error && !fn_for_each_in_ns(label, profile,
                                        COMPLAIN_MODE(profile)))
                goto audit;

        /* TODO: add permission check to allow this
         * if ((flags & AA_CHANGE_ONEXEC) && !current_is_single_threaded()) {
         *      info = "not a single threaded task";
         *      error = -EACCES;
         *      goto audit;
         * }
         */
        if (flags & AA_CHANGE_TEST)
                goto out;

        if (!(flags & AA_CHANGE_ONEXEC)) {
                /* only transition profiles in the current ns */
                if (stack)
                        new = aa_label_merge(label, target, GFP_KERNEL);
                else
                        new = fn_label_build_in_ns(label, profile, GFP_KERNEL,
                                        aa_get_label(target),
                                        aa_get_label(&profile->label));
                if (IS_ERR_OR_NULL(new)) {
                        info = "failed to build target label";
                        error = PTR_ERR(new);
                        new = NULL;
                        perms.allow = 0;
                        goto audit;
                }
                error = aa_replace_current_label(new);
        } else
                /* full transition will be built in exec path */
                error = aa_set_current_onexec(target, stack);

audit:
        error = fn_for_each_in_ns(label, profile,
                        aa_audit_file(profile, &perms, op, request, auditname,
                                      NULL, new ? new : target,
                                      GLOBAL_ROOT_UID, info, error));

out:
        aa_put_label(new);
        aa_put_label(target);
        aa_put_label(label);

        return error;
}