/*
 * 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"

/**
 * 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_profile: profile to change to  (NOT NULL)
 *
 * 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_profile *to_profile)
{
        struct task_struct *tracer;
        struct aa_profile *tracerp = NULL;
        int error = 0;

        rcu_read_lock();
        tracer = ptrace_parent(current);
        if (tracer)
                /* released below */
                tracerp = aa_get_task_profile(tracer);

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

        error = aa_may_ptrace(tracerp, to_profile, PTRACE_MODE_ATTACH);

out:
        rcu_read_unlock();
        aa_put_profile(tracerp);

        return error;
}

/**
 * change_profile_perms - find permissions for change_profile
 * @profile: the current profile  (NOT NULL)
 * @ns: the namespace being switched to  (NOT NULL)
 * @name: the name of the profile to change to  (NOT NULL)
 * @request: requested perms
 * @start: state to start matching in
 *
 * Returns: permission set
 */
static struct file_perms change_profile_perms(struct aa_profile *profile,
                                              struct aa_namespace *ns,
                                              const char *name, u32 request,
                                              unsigned int start)
{
        struct file_perms perms;
        struct path_cond cond = { };
        unsigned int state;

        if (unconfined(profile)) {
                perms.allow = AA_MAY_CHANGE_PROFILE | AA_MAY_ONEXEC;
                perms.audit = perms.quiet = perms.kill = 0;
                return perms;
        } else if (!profile->file.dfa) {
                return nullperms;
        } else if ((ns == profile->ns)) {
                /* try matching against rules with out namespace prepended */
                aa_str_perms(profile->file.dfa, start, name, &cond, &perms);
                if (COMBINED_PERM_MASK(perms) & request)
                        return perms;
        }

        /* try matching with namespace name and then profile */
        state = aa_dfa_match(profile->file.dfa, start, ns->base.name);
        state = aa_dfa_match_len(profile->file.dfa, state, ":", 1);
        aa_str_perms(profile->file.dfa, state, name, &cond, &perms);

        return 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->flags & PFLAG_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: profile or NULL if no match found
 */
static struct aa_profile *find_attach(struct aa_namespace *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;
}

/**
 * separate_fqname - separate the namespace and profile names
 * @fqname: the fqname name to split  (NOT NULL)
 * @ns_name: the namespace name if it exists  (NOT NULL)
 *
 * This is the xtable equivalent routine of aa_split_fqname.  It finds the
 * split in an xtable fqname which contains an embedded \0 instead of a :
 * if a namespace is specified.  This is done so the xtable is constant and
 * isn't re-split on every lookup.
 *
 * Either the profile or namespace name may be optional but if the namespace
 * is specified the profile name termination must be present.  This results
 * in the following possible encodings:
 * profile_name\0
 * :ns_name\0profile_name\0
 * :ns_name\0\0
 *
 * NOTE: the xtable fqname is pre-validated at load time in unpack_trans_table
 *
 * Returns: profile name if it is specified else NULL
 */
static const char *separate_fqname(const char *fqname, const char **ns_name)
{
        const char *name;

        if (fqname[0] == ':') {
                /* In this case there is guaranteed to be two \0 terminators
                 * in the string.  They are verified at load time by
                 * by unpack_trans_table
                 */
                *ns_name = fqname + 1;          /* skip : */
                name = *ns_name + strlen(*ns_name) + 1;
                if (!*name)
                        name = NULL;
        } else {
                *ns_name = NULL;
                name = fqname;
        }

        return name;
}

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
 *
 * Returns: refcounted profile, or NULL on failure (MAYBE NULL)
 */
static struct aa_profile *x_table_lookup(struct aa_profile *profile, u32 xindex)
{
        struct aa_profile *new_profile = NULL;
        struct aa_namespace *ns = profile->ns;
        u32 xtype = xindex & AA_X_TYPE_MASK;
        int index = xindex & AA_X_INDEX_MASK;
        const char *name;

        /* index is guaranteed to be in range, validated at load time */
        for (name = profile->file.trans.table[index]; !new_profile && name;
             name = next_name(xtype, name)) {
                struct aa_namespace *new_ns;
                const char *xname = NULL;

                new_ns = NULL;
                if (xindex & AA_X_CHILD) {
                        /* release by caller */
                        new_profile = aa_find_child(profile, name);
                        continue;
                } else if (*name == ':') {
                        /* switching namespace */
                        const char *ns_name;
                        xname = name = separate_fqname(name, &ns_name);
                        if (!xname)
                                /* no name so use profile name */
                                xname = profile->base.hname;
                        if (*ns_name == '@') {
                                /* TODO: variable support */
                                ;
                        }
                        /* released below */
                        new_ns = aa_find_namespace(ns, ns_name);
                        if (!new_ns)
                                continue;
                } else if (*name == '@') {
                        /* TODO: variable support */
                        continue;
                } else {
                        /* basic namespace lookup */
                        xname = name;
                }

                /* released by caller */
                new_profile = aa_lookup_profile(new_ns ? new_ns : ns, xname);
                aa_put_namespace(new_ns);
        }

        /* released by caller */
        return new_profile;
}

/**
 * x_to_profile - get target profile for a given xindex
 * @profile: current profile  (NOT NULL)
 * @name: name to lookup (NOT NULL)
 * @xindex: index into x transition table
 *
 * find profile for a transition index
 *
 * Returns: refcounted profile or NULL if not found available
 */
static struct aa_profile *x_to_profile(struct aa_profile *profile,
                                       const char *name, u32 xindex)
{
        struct aa_profile *new_profile = NULL;
        struct aa_namespace *ns = profile->ns;
        u32 xtype = xindex & AA_X_TYPE_MASK;

        switch (xtype) {
        case AA_X_NONE:
                /* fail exec unless ix || ux fallback - handled by caller */
                return NULL;
        case AA_X_NAME:
                if (xindex & AA_X_CHILD)
                        /* released by caller */
                        new_profile = find_attach(ns, &profile->base.profiles,
                                                  name);
                else
                        /* released by caller */
                        new_profile = find_attach(ns, &ns->base.profiles,
                                                  name);
                break;
        case AA_X_TABLE:
                /* released by caller */
                new_profile = x_table_lookup(profile, xindex);
                break;
        }

        /* released by caller */
        return new_profile;
}

/**
 * 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
 */
int apparmor_bprm_set_creds(struct linux_binprm *bprm)
{
        struct aa_task_cxt *cxt;
        struct aa_profile *profile, *new_profile = NULL;
        struct aa_namespace *ns;
        char *buffer = NULL;
        unsigned int state;
        struct file_perms perms = {};
        struct path_cond cond = {
                file_inode(bprm->file)->i_uid,
                file_inode(bprm->file)->i_mode
        };
        const char *name = NULL, *target = NULL, *info = NULL;
        int error = 0;

        if (bprm->cred_prepared)
                return 0;

        cxt = cred_cxt(bprm->cred);
        BUG_ON(!cxt);

        profile = aa_get_newest_profile(cxt->profile);
        /*
         * get the namespace from the replacement profile as replacement
         * can change the namespace
         */
        ns = profile->ns;
        state = profile->file.start;

        /* buffer freed below, name is pointer into buffer */
        error = aa_path_name(&bprm->file->f_path, profile->path_flags, &buffer,
                             &name, &info);
        if (error) {
                if (unconfined(profile) ||
                    (profile->flags & PFLAG_IX_ON_NAME_ERROR))
                        error = 0;
                name = bprm->filename;
                goto audit;
        }

        /* Test for onexec first as onexec directives override other
         * x transitions.
         */
        if (unconfined(profile)) {
                /* unconfined task */
                if (cxt->onexec)
                        /* change_profile on exec already been granted */
                        new_profile = aa_get_profile(cxt->onexec);
                else
                        new_profile = find_attach(ns, &ns->base.profiles, name);
                if (!new_profile)
                        goto cleanup;
                /*
                 * NOTE: Domain transitions from unconfined are allowed
                 * even when no_new_privs is set because this aways results
                 * in a further reduction of permissions.
                 */
                goto apply;
        }

        /* find exec permissions for name */
        state = aa_str_perms(profile->file.dfa, state, name, &cond, &perms);
        if (cxt->onexec) {
                struct file_perms cp;
                info = "change_profile onexec";
                if (!(perms.allow & AA_MAY_ONEXEC))
                        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);
                cp = change_profile_perms(profile, cxt->onexec->ns,
                                          cxt->onexec->base.name,
                                          AA_MAY_ONEXEC, state);

                if (!(cp.allow & AA_MAY_ONEXEC))
                        goto audit;
                new_profile = aa_get_newest_profile(cxt->onexec);
                goto apply;
        }

        if (perms.allow & MAY_EXEC) {
                /* exec permission determine how to transition */
                new_profile = x_to_profile(profile, name, perms.xindex);
                if (!new_profile) {
                        if (perms.xindex & AA_X_INHERIT) {
                                /* (p|c|n)ix - don't change profile but do
                                 * use the newest version, which was picked
                                 * up above when getting profile
                                 */
                                info = "ix fallback";
                                new_profile = aa_get_profile(profile);
                                goto x_clear;
                        } else if (perms.xindex & AA_X_UNCONFINED) {
                                new_profile = aa_get_newest_profile(ns->unconfined);
                                info = "ux fallback";
                        } else {
                                error = -ENOENT;
                                info = "profile not found";
                                /* remove MAY_EXEC to audit as failure */
                                perms.allow &= ~MAY_EXEC;
                        }
                }
        } else if (COMPLAIN_MODE(profile)) {
                /* no exec permission - are we in learning mode */
                new_profile = aa_new_null_profile(profile, 0);
                if (!new_profile) {
                        error = -ENOMEM;
                        info = "could not create null profile";
                } else {
                        error = -EACCES;
                        target = new_profile->base.hname;
                }
                perms.xindex |= AA_X_UNSAFE;
        } else
                /* fail exec */
                error = -EACCES;

        /*
         * Policy has specified a domain transition, if no_new_privs then
         * fail the exec.
         */
        if (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) {
                aa_put_profile(new_profile);
                error = -EPERM;
                goto cleanup;
        }

        if (!new_profile)
                goto audit;

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

        if (bprm->unsafe & (LSM_UNSAFE_PTRACE | LSM_UNSAFE_PTRACE_CAP)) {
                error = may_change_ptraced_domain(new_profile);
                if (error) {
                        aa_put_profile(new_profile);
                        goto audit;
                }
        }

        /* Determine if secure exec is needed.
         * Can be at this point for the following reasons:
         * 1. unconfined switching to confined
         * 2. confined switching to different confinement
         * 3. confined switching to unconfined
         *
         * Cases 2 and 3 are marked as requiring secure exec
         * (unless policy specified "unsafe exec")
         *
         * bprm->unsafe is used to cache the AA_X_UNSAFE permission
         * to avoid having to recompute in secureexec
         */
        if (!(perms.xindex & AA_X_UNSAFE)) {
                AA_DEBUG("scrubbing environment variables for %s profile=%s\n",
                         name, new_profile->base.hname);
                bprm->unsafe |= AA_SECURE_X_NEEDED;
        }
apply:
        target = new_profile->base.hname;
        /* when transitioning profiles clear unsafe personality bits */
        bprm->per_clear |= PER_CLEAR_ON_SETID;

x_clear:
        aa_put_profile(cxt->profile);
        /* transfer new profile reference will be released when cxt is freed */
        cxt->profile = new_profile;

        /* clear out all temporary/transitional state from the context */
        aa_clear_task_cxt_trans(cxt);

audit:
        error = aa_audit_file(profile, &perms, GFP_KERNEL, OP_EXEC, MAY_EXEC,
                              name, target, cond.uid, info, error);

cleanup:
        aa_put_profile(profile);
        kfree(buffer);

        return error;
}

/**
 * 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;
}

/**
 * apparmor_bprm_committing_creds - do task cleanup on committing new creds
 * @bprm: binprm for the exec  (NOT NULL)
 */
void apparmor_bprm_committing_creds(struct linux_binprm *bprm)
{
        struct aa_profile *profile = __aa_current_profile();
        struct aa_task_cxt *new_cxt = cred_cxt(bprm->cred);

        /* bail out if unconfined or not changing profile */
        if ((new_cxt->profile == profile) ||
            (unconfined(new_cxt->profile)))
                return;

        current->pdeath_signal = 0;

        /* reset soft limits and set hard limits for the new profile */
        __aa_transition_rlimits(profile, new_cxt->profile);
}

/**
 * apparmor_bprm_commited_cred - do cleanup after new creds committed
 * @bprm: binprm for the exec  (NOT NULL)
 */
void apparmor_bprm_committed_creds(struct linux_binprm *bprm)
{
        /* TODO: cleanup signals - ipc mediation */
        return;
}

/*
 * Functions for self directed profile change
 */

/**
 * new_compound_name - create an hname with @n2 appended to @n1
 * @n1: base of hname  (NOT NULL)
 * @n2: name to append (NOT NULL)
 *
 * Returns: new name or NULL on error
 */
static char *new_compound_name(const char *n1, const char *n2)
{
        char *name = kmalloc(strlen(n1) + strlen(n2) + 3, GFP_KERNEL);
        if (name)
                sprintf(name, "%s//%s", n1, n2);
        return name;
}

/**
 * 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
 * @permtest: true if this is just a permission test
 *
 * 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.
 *
 * Returns %0 on success, error otherwise.
 */
int aa_change_hat(const char *hats[], int count, u64 token, bool permtest)
{
        const struct cred *cred;
        struct aa_task_cxt *cxt;
        struct aa_profile *profile, *previous_profile, *hat = NULL;
        char *name = NULL;
        int i;
        struct file_perms perms = {};
        const char *target = NULL, *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))
                return -EPERM;

        /* released below */
        cred = get_current_cred();
        cxt = cred_cxt(cred);
        profile = aa_cred_profile(cred);
        previous_profile = cxt->previous;

        if (unconfined(profile)) {
                info = "unconfined";
                error = -EPERM;
                goto audit;
        }

        if (count) {
                /* attempting to change into a new hat or switch to a sibling */
                struct aa_profile *root;
                if (PROFILE_IS_HAT(profile))
                        root = aa_get_profile_rcu(&profile->parent);
                else
                        root = aa_get_profile(profile);

                /* find first matching hat */
                for (i = 0; i < count && !hat; i++)
                        /* released below */
                        hat = aa_find_child(root, hats[i]);
                if (!hat) {
                        if (!COMPLAIN_MODE(root) || permtest) {
                                if (list_empty(&root->base.profiles))
                                        error = -ECHILD;
                                else
                                        error = -ENOENT;
                                aa_put_profile(root);
                                goto out;
                        }

                        /*
                         * In complain mode and failed to match any hats.
                         * Audit the failure is based off of the first hat
                         * supplied.  This is done due how userspace
                         * interacts with change_hat.
                         *
                         * TODO: Add logging of all failed hats
                         */

                        /* freed below */
                        name = new_compound_name(root->base.hname, hats[0]);
                        aa_put_profile(root);
                        target = name;
                        /* released below */
                        hat = aa_new_null_profile(profile, 1);
                        if (!hat) {
                                info = "failed null profile create";
                                error = -ENOMEM;
                                goto audit;
                        }
                } else {
                        aa_put_profile(root);
                        target = hat->base.hname;
                        if (!PROFILE_IS_HAT(hat)) {
                                info = "target not hat";
                                error = -EPERM;
                                goto audit;
                        }
                }

                error = may_change_ptraced_domain(hat);
                if (error) {
                        info = "ptraced";
                        error = -EPERM;
                        goto audit;
                }

                if (!permtest) {
                        error = aa_set_current_hat(hat, token);
                        if (error == -EACCES)
                                /* kill task in case of brute force attacks */
                                perms.kill = AA_MAY_CHANGEHAT;
                        else if (name && !error)
                                /* reset error for learning of new hats */
                                error = -ENOENT;
                }
        } else if (previous_profile) {
                /* Return to saved profile.  Kill task if restore fails
                 * to avoid brute force attacks
                 */
                target = previous_profile->base.hname;
                error = aa_restore_previous_profile(token);
                perms.kill = AA_MAY_CHANGEHAT;
        } else
                /* ignore restores when there is no saved profile */
                goto out;

audit:
        if (!permtest)
                error = aa_audit_file(profile, &perms, GFP_KERNEL,
                                      OP_CHANGE_HAT, AA_MAY_CHANGEHAT, NULL,
                                      target, GLOBAL_ROOT_UID, info, error);

out:
        aa_put_profile(hat);
        kfree(name);
        put_cred(cred);

        return error;
}

/**
 * aa_change_profile - perform a one-way profile transition
 * @ns_name: name of the profile namespace to change to (MAYBE NULL)
 * @hname: name of profile to change to (MAYBE NULL)
 * @onexec: whether this transition is to take place immediately or at exec
 * @permtest: true if this is just a permission test
 *
 * 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 *ns_name, const char *hname, bool onexec,
                      bool permtest)
{
        const struct cred *cred;
        struct aa_profile *profile, *target = NULL;
        struct aa_namespace *ns = NULL;
        struct file_perms perms = {};
        const char *name = NULL, *info = NULL;
        int op, error = 0;
        u32 request;

        if (!hname && !ns_name)
                return -EINVAL;

        if (onexec) {
                request = AA_MAY_ONEXEC;
                op = OP_CHANGE_ONEXEC;
        } else {
                request = AA_MAY_CHANGE_PROFILE;
                op = OP_CHANGE_PROFILE;
        }

        cred = get_current_cred();
        profile = aa_cred_profile(cred);

        /*
         * Fail explicitly requested domain transitions if no_new_privs
         * and not unconfined.
         * Domain 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) && !unconfined(profile)) {
                put_cred(cred);
                return -EPERM;
        }

        if (ns_name) {
                /* released below */
                ns = aa_find_namespace(profile->ns, ns_name);
                if (!ns) {
                        /* we don't create new namespace in complain mode */
                        name = ns_name;
                        info = "namespace not found";
                        error = -ENOENT;
                        goto audit;
                }
        } else
                /* released below */
                ns = aa_get_namespace(profile->ns);

        /* if the name was not specified, use the name of the current profile */
        if (!hname) {
                if (unconfined(profile))
                        hname = ns->unconfined->base.hname;
                else
                        hname = profile->base.hname;
        }

        perms = change_profile_perms(profile, ns, hname, request,
                                     profile->file.start);
        if (!(perms.allow & request)) {
                error = -EACCES;
                goto audit;
        }

        /* released below */
        target = aa_lookup_profile(ns, hname);
        if (!target) {
                info = "profile not found";
                error = -ENOENT;
                if (permtest || !COMPLAIN_MODE(profile))
                        goto audit;
                /* released below */
                target = aa_new_null_profile(profile, 0);
                if (!target) {
                        info = "failed null profile create";
                        error = -ENOMEM;
                        goto audit;
                }
        }

        /* check if tracing task is allowed to trace target domain */
        error = may_change_ptraced_domain(target);
        if (error) {
                info = "ptrace prevents transition";
                goto audit;
        }

        if (permtest)
                goto audit;

        if (onexec)
                error = aa_set_current_onexec(target);
        else
                error = aa_replace_current_profile(target);

audit:
        if (!permtest)
                error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request,
                                      name, hname, GLOBAL_ROOT_UID, info, error);

        aa_put_namespace(ns);
        aa_put_profile(target);
        put_cred(cred);

        return error;
}