/*
 * AppArmor security module
 *
 * This file contains AppArmor mediation of files
 *
 * Copyright (C) 1998-2008 Novell/SUSE
 * Copyright 2009-2017 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/fs.h>
#include <linux/mount.h>
#include <linux/namei.h>

#include "include/apparmor.h"
#include "include/audit.h"
#include "include/cred.h"
#include "include/domain.h"
#include "include/file.h"
#include "include/match.h"
#include "include/mount.h"
#include "include/path.h"
#include "include/policy.h"


static void audit_mnt_flags(struct audit_buffer *ab, unsigned long flags)
{
        if (flags & MS_RDONLY)
                audit_log_format(ab, "ro");
        else
                audit_log_format(ab, "rw");
        if (flags & MS_NOSUID)
                audit_log_format(ab, ", nosuid");
        if (flags & MS_NODEV)
                audit_log_format(ab, ", nodev");
        if (flags & MS_NOEXEC)
                audit_log_format(ab, ", noexec");
        if (flags & MS_SYNCHRONOUS)
                audit_log_format(ab, ", sync");
        if (flags & MS_REMOUNT)
                audit_log_format(ab, ", remount");
        if (flags & MS_MANDLOCK)
                audit_log_format(ab, ", mand");
        if (flags & MS_DIRSYNC)
                audit_log_format(ab, ", dirsync");
        if (flags & MS_NOATIME)
                audit_log_format(ab, ", noatime");
        if (flags & MS_NODIRATIME)
                audit_log_format(ab, ", nodiratime");
        if (flags & MS_BIND)
                audit_log_format(ab, flags & MS_REC ? ", rbind" : ", bind");
        if (flags & MS_MOVE)
                audit_log_format(ab, ", move");
        if (flags & MS_SILENT)
                audit_log_format(ab, ", silent");
        if (flags & MS_POSIXACL)
                audit_log_format(ab, ", acl");
        if (flags & MS_UNBINDABLE)
                audit_log_format(ab, flags & MS_REC ? ", runbindable" :
                                 ", unbindable");
        if (flags & MS_PRIVATE)
                audit_log_format(ab, flags & MS_REC ? ", rprivate" :
                                 ", private");
        if (flags & MS_SLAVE)
                audit_log_format(ab, flags & MS_REC ? ", rslave" :
                                 ", slave");
        if (flags & MS_SHARED)
                audit_log_format(ab, flags & MS_REC ? ", rshared" :
                                 ", shared");
        if (flags & MS_RELATIME)
                audit_log_format(ab, ", relatime");
        if (flags & MS_I_VERSION)
                audit_log_format(ab, ", iversion");
        if (flags & MS_STRICTATIME)
                audit_log_format(ab, ", strictatime");
        if (flags & MS_NOUSER)
                audit_log_format(ab, ", nouser");
}

/**
 * audit_cb - call back for mount specific audit fields
 * @ab: audit_buffer  (NOT NULL)
 * @va: audit struct to audit values of  (NOT NULL)
 */
static void audit_cb(struct audit_buffer *ab, void *va)
{
        struct common_audit_data *sa = va;

        if (aad(sa)->mnt.type) {
                audit_log_format(ab, " fstype=");
                audit_log_untrustedstring(ab, aad(sa)->mnt.type);
        }
        if (aad(sa)->mnt.src_name) {
                audit_log_format(ab, " srcname=");
                audit_log_untrustedstring(ab, aad(sa)->mnt.src_name);
        }
        if (aad(sa)->mnt.trans) {
                audit_log_format(ab, " trans=");
                audit_log_untrustedstring(ab, aad(sa)->mnt.trans);
        }
        if (aad(sa)->mnt.flags) {
                audit_log_format(ab, " flags=\"");
                audit_mnt_flags(ab, aad(sa)->mnt.flags);
                audit_log_format(ab, "\"");
        }
        if (aad(sa)->mnt.data) {
                audit_log_format(ab, " options=");
                audit_log_untrustedstring(ab, aad(sa)->mnt.data);
        }
}

/**
 * audit_mount - handle the auditing of mount operations
 * @profile: the profile being enforced  (NOT NULL)
 * @op: operation being mediated (NOT NULL)
 * @name: name of object being mediated (MAYBE NULL)
 * @src_name: src_name of object being mediated (MAYBE_NULL)
 * @type: type of filesystem (MAYBE_NULL)
 * @trans: name of trans (MAYBE NULL)
 * @flags: filesystem idependent mount flags
 * @data: filesystem mount flags
 * @request: permissions requested
 * @perms: the permissions computed for the request (NOT NULL)
 * @info: extra information message (MAYBE NULL)
 * @error: 0 if operation allowed else failure error code
 *
 * Returns: %0 or error on failure
 */
static int audit_mount(struct aa_profile *profile, const char *op,
                       const char *name, const char *src_name,
                       const char *type, const char *trans,
                       unsigned long flags, const void *data, u32 request,
                       struct aa_perms *perms, const char *info, int error)
{
        int audit_type = AUDIT_APPARMOR_AUTO;
        DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, op);

        if (likely(!error)) {
                u32 mask = perms->audit;

                if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
                        mask = 0xffff;

                /* mask off perms that are not being force audited */
                request &= mask;

                if (likely(!request))
                        return 0;
                audit_type = AUDIT_APPARMOR_AUDIT;
        } else {
                /* only report permissions that were denied */
                request = request & ~perms->allow;

                if (request & perms->kill)
                        audit_type = AUDIT_APPARMOR_KILL;

                /* quiet known rejects, assumes quiet and kill do not overlap */
                if ((request & perms->quiet) &&
                    AUDIT_MODE(profile) != AUDIT_NOQUIET &&
                    AUDIT_MODE(profile) != AUDIT_ALL)
                        request &= ~perms->quiet;

                if (!request)
                        return error;
        }

        aad(&sa)->name = name;
        aad(&sa)->mnt.src_name = src_name;
        aad(&sa)->mnt.type = type;
        aad(&sa)->mnt.trans = trans;
        aad(&sa)->mnt.flags = flags;
        if (data && (perms->audit & AA_AUDIT_DATA))
                aad(&sa)->mnt.data = data;
        aad(&sa)->info = info;
        aad(&sa)->error = error;

        return aa_audit(audit_type, profile, &sa, audit_cb);
}

/**
 * match_mnt_flags - Do an ordered match on mount flags
 * @dfa: dfa to match against
 * @state: state to start in
 * @flags: mount flags to match against
 *
 * Mount flags are encoded as an ordered match. This is done instead of
 * checking against a simple bitmask, to allow for logical operations
 * on the flags.
 *
 * Returns: next state after flags match
 */
static unsigned int match_mnt_flags(struct aa_dfa *dfa, unsigned int state,
                                    unsigned long flags)
{
        unsigned int i;

        for (i = 0; i <= 31 ; ++i) {
                if ((1 << i) & flags)
                        state = aa_dfa_next(dfa, state, i + 1);
        }

        return state;
}

/**
 * compute_mnt_perms - compute mount permission associated with @state
 * @dfa: dfa to match against (NOT NULL)
 * @state: state match finished in
 *
 * Returns: mount permissions
 */
static struct aa_perms compute_mnt_perms(struct aa_dfa *dfa,
                                           unsigned int state)
{
        struct aa_perms perms = {
                .allow = dfa_user_allow(dfa, state),
                .audit = dfa_user_audit(dfa, state),
                .quiet = dfa_user_quiet(dfa, state),
                .xindex = dfa_user_xindex(dfa, state),
        };

        return perms;
}

static const char * const mnt_info_table[] = {
        "match succeeded",
        "failed mntpnt match",
        "failed srcname match",
        "failed type match",
        "failed flags match",
        "failed data match"
};

/*
 * Returns 0 on success else element that match failed in, this is the
 * index into the mnt_info_table above
 */
static int do_match_mnt(struct aa_dfa *dfa, unsigned int start,
                        const char *mntpnt, const char *devname,
                        const char *type, unsigned long flags,
                        void *data, bool binary, struct aa_perms *perms)
{
        unsigned int state;

        AA_BUG(!dfa);
        AA_BUG(!perms);

        state = aa_dfa_match(dfa, start, mntpnt);
        state = aa_dfa_null_transition(dfa, state);
        if (!state)
                return 1;

        if (devname)
                state = aa_dfa_match(dfa, state, devname);
        state = aa_dfa_null_transition(dfa, state);
        if (!state)
                return 2;

        if (type)
                state = aa_dfa_match(dfa, state, type);
        state = aa_dfa_null_transition(dfa, state);
        if (!state)
                return 3;

        state = match_mnt_flags(dfa, state, flags);
        if (!state)
                return 4;
        *perms = compute_mnt_perms(dfa, state);
        if (perms->allow & AA_MAY_MOUNT)
                return 0;

        /* only match data if not binary and the DFA flags data is expected */
        if (data && !binary && (perms->allow & AA_MNT_CONT_MATCH)) {
                state = aa_dfa_null_transition(dfa, state);
                if (!state)
                        return 4;

                state = aa_dfa_match(dfa, state, data);
                if (!state)
                        return 5;
                *perms = compute_mnt_perms(dfa, state);
                if (perms->allow & AA_MAY_MOUNT)
                        return 0;
        }

        /* failed at end of flags match */
        return 4;
}


static int path_flags(struct aa_profile *profile, const struct path *path)
{
        AA_BUG(!profile);
        AA_BUG(!path);

        return profile->path_flags |
                (S_ISDIR(path->dentry->d_inode->i_mode) ? PATH_IS_DIR : 0);
}

/**
 * match_mnt_path_str - handle path matching for mount
 * @profile: the confining profile
 * @mntpath: for the mntpnt (NOT NULL)
 * @buffer: buffer to be used to lookup mntpath
 * @devnme: string for the devname/src_name (MAY BE NULL OR ERRPTR)
 * @type: string for the dev type (MAYBE NULL)
 * @flags: mount flags to match
 * @data: fs mount data (MAYBE NULL)
 * @binary: whether @data is binary
 * @devinfo: error str if (IS_ERR(@devname))
 *
 * Returns: 0 on success else error
 */
static int match_mnt_path_str(struct aa_profile *profile,
                              const struct path *mntpath, char *buffer,
                              const char *devname, const char *type,
                              unsigned long flags, void *data, bool binary,
                              const char *devinfo)
{
        struct aa_perms perms = { };
        const char *mntpnt = NULL, *info = NULL;
        int pos, error;

        AA_BUG(!profile);
        AA_BUG(!mntpath);
        AA_BUG(!buffer);

        if (!PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
                return 0;

        error = aa_path_name(mntpath, path_flags(profile, mntpath), buffer,
                             &mntpnt, &info, profile->disconnected);
        if (error)
                goto audit;
        if (IS_ERR(devname)) {
                error = PTR_ERR(devname);
                devname = NULL;
                info = devinfo;
                goto audit;
        }

        error = -EACCES;
        pos = do_match_mnt(profile->policy.dfa,
                           profile->policy.start[AA_CLASS_MOUNT],
                           mntpnt, devname, type, flags, data, binary, &perms);
        if (pos) {
                info = mnt_info_table[pos];
                goto audit;
        }
        error = 0;

audit:
        return audit_mount(profile, OP_MOUNT, mntpnt, devname, type, NULL,
                           flags, data, AA_MAY_MOUNT, &perms, info, error);
}

/**
 * match_mnt - handle path matching for mount
 * @profile: the confining profile
 * @mntpath: for the mntpnt (NOT NULL)
 * @buffer: buffer to be used to lookup mntpath
 * @devpath: path devname/src_name (MAYBE NULL)
 * @devbuffer: buffer to be used to lookup devname/src_name
 * @type: string for the dev type (MAYBE NULL)
 * @flags: mount flags to match
 * @data: fs mount data (MAYBE NULL)
 * @binary: whether @data is binary
 *
 * Returns: 0 on success else error
 */
static int match_mnt(struct aa_profile *profile, const struct path *path,
                     char *buffer, struct path *devpath, char *devbuffer,
                     const char *type, unsigned long flags, void *data,
                     bool binary)
{
        const char *devname = NULL, *info = NULL;
        int error = -EACCES;

        AA_BUG(!profile);
        AA_BUG(devpath && !devbuffer);

        if (!PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
                return 0;

        if (devpath) {
                error = aa_path_name(devpath, path_flags(profile, devpath),
                                     devbuffer, &devname, &info,
                                     profile->disconnected);
                if (error)
                        devname = ERR_PTR(error);
        }

        return match_mnt_path_str(profile, path, buffer, devname, type, flags,
                                  data, binary, info);
}

int aa_remount(struct aa_label *label, const struct path *path,
               unsigned long flags, void *data)
{
        struct aa_profile *profile;
        char *buffer = NULL;
        bool binary;
        int error;

        AA_BUG(!label);
        AA_BUG(!path);

        binary = path->dentry->d_sb->s_type->fs_flags & FS_BINARY_MOUNTDATA;

        get_buffers(buffer);
        error = fn_for_each_confined(label, profile,
                        match_mnt(profile, path, buffer, NULL, NULL, NULL,
                                  flags, data, binary));
        put_buffers(buffer);

        return error;
}

int aa_bind_mount(struct aa_label *label, const struct path *path,
                  const char *dev_name, unsigned long flags)
{
        struct aa_profile *profile;
        char *buffer = NULL, *old_buffer = NULL;
        struct path old_path;
        int error;

        AA_BUG(!label);
        AA_BUG(!path);

        if (!dev_name || !*dev_name)
                return -EINVAL;

        flags &= MS_REC | MS_BIND;

        error = kern_path(dev_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
        if (error)
                return error;

        get_buffers(buffer, old_buffer);
        error = fn_for_each_confined(label, profile,
                        match_mnt(profile, path, buffer, &old_path, old_buffer,
                                  NULL, flags, NULL, false));
        put_buffers(buffer, old_buffer);
        path_put(&old_path);

        return error;
}

int aa_mount_change_type(struct aa_label *label, const struct path *path,
                         unsigned long flags)
{
        struct aa_profile *profile;
        char *buffer = NULL;
        int error;

        AA_BUG(!label);
        AA_BUG(!path);

        /* These are the flags allowed by do_change_type() */
        flags &= (MS_REC | MS_SILENT | MS_SHARED | MS_PRIVATE | MS_SLAVE |
                  MS_UNBINDABLE);

        get_buffers(buffer);
        error = fn_for_each_confined(label, profile,
                        match_mnt(profile, path, buffer, NULL, NULL, NULL,
                                  flags, NULL, false));
        put_buffers(buffer);

        return error;
}

int aa_move_mount(struct aa_label *label, const struct path *path,
                  const char *orig_name)
{
        struct aa_profile *profile;
        char *buffer = NULL, *old_buffer = NULL;
        struct path old_path;
        int error;

        AA_BUG(!label);
        AA_BUG(!path);

        if (!orig_name || !*orig_name)
                return -EINVAL;

        error = kern_path(orig_name, LOOKUP_FOLLOW, &old_path);
        if (error)
                return error;

        get_buffers(buffer, old_buffer);
        error = fn_for_each_confined(label, profile,
                        match_mnt(profile, path, buffer, &old_path, old_buffer,
                                  NULL, MS_MOVE, NULL, false));
        put_buffers(buffer, old_buffer);
        path_put(&old_path);

        return error;
}

int aa_new_mount(struct aa_label *label, const char *dev_name,
                 const struct path *path, const char *type, unsigned long flags,
                 void *data)
{
        struct aa_profile *profile;
        char *buffer = NULL, *dev_buffer = NULL;
        bool binary = true;
        int error;
        int requires_dev = 0;
        struct path tmp_path, *dev_path = NULL;

        AA_BUG(!label);
        AA_BUG(!path);

        if (type) {
                struct file_system_type *fstype;

                fstype = get_fs_type(type);
                if (!fstype)
                        return -ENODEV;
                binary = fstype->fs_flags & FS_BINARY_MOUNTDATA;
                requires_dev = fstype->fs_flags & FS_REQUIRES_DEV;
                put_filesystem(fstype);

                if (requires_dev) {
                        if (!dev_name || !*dev_name)
                                return -ENOENT;

                        error = kern_path(dev_name, LOOKUP_FOLLOW, &tmp_path);
                        if (error)
                                return error;
                        dev_path = &tmp_path;
                }
        }

        get_buffers(buffer, dev_buffer);
        if (dev_path) {
                error = fn_for_each_confined(label, profile,
                        match_mnt(profile, path, buffer, dev_path, dev_buffer,
                                  type, flags, data, binary));
        } else {
                error = fn_for_each_confined(label, profile,
                        match_mnt_path_str(profile, path, buffer, dev_name,
                                           type, flags, data, binary, NULL));
        }
        put_buffers(buffer, dev_buffer);
        if (dev_path)
                path_put(dev_path);

        return error;
}

static int profile_umount(struct aa_profile *profile, struct path *path,
                          char *buffer)
{
        struct aa_perms perms = { };
        const char *name = NULL, *info = NULL;
        unsigned int state;
        int error;

        AA_BUG(!profile);
        AA_BUG(!path);

        if (!PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
                return 0;

        error = aa_path_name(path, path_flags(profile, path), buffer, &name,
                             &info, profile->disconnected);
        if (error)
                goto audit;

        state = aa_dfa_match(profile->policy.dfa,
                             profile->policy.start[AA_CLASS_MOUNT],
                             name);
        perms = compute_mnt_perms(profile->policy.dfa, state);
        if (AA_MAY_UMOUNT & ~perms.allow)
                error = -EACCES;

audit:
        return audit_mount(profile, OP_UMOUNT, name, NULL, NULL, NULL, 0, NULL,
                           AA_MAY_UMOUNT, &perms, info, error);
}

int aa_umount(struct aa_label *label, struct vfsmount *mnt, int flags)
{
        struct aa_profile *profile;
        char *buffer = NULL;
        int error;
        struct path path = { .mnt = mnt, .dentry = mnt->mnt_root };

        AA_BUG(!label);
        AA_BUG(!mnt);

        get_buffers(buffer);
        error = fn_for_each_confined(label, profile,
                        profile_umount(profile, &path, buffer));
        put_buffers(buffer);

        return error;
}

/* helper fn for transition on pivotroot
 *
 * Returns: label for transition or ERR_PTR. Does not return NULL
 */
static struct aa_label *build_pivotroot(struct aa_profile *profile,
                                        const struct path *new_path,
                                        char *new_buffer,
                                        const struct path *old_path,
                                        char *old_buffer)
{
        const char *old_name, *new_name = NULL, *info = NULL;
        const char *trans_name = NULL;
        struct aa_perms perms = { };
        unsigned int state;
        int error;

        AA_BUG(!profile);
        AA_BUG(!new_path);
        AA_BUG(!old_path);

        if (profile_unconfined(profile) ||
            !PROFILE_MEDIATES(profile, AA_CLASS_MOUNT))
                return aa_get_newest_label(&profile->label);

        error = aa_path_name(old_path, path_flags(profile, old_path),
                             old_buffer, &old_name, &info,
                             profile->disconnected);
        if (error)
                goto audit;
        error = aa_path_name(new_path, path_flags(profile, new_path),
                             new_buffer, &new_name, &info,
                             profile->disconnected);
        if (error)
                goto audit;

        error = -EACCES;
        state = aa_dfa_match(profile->policy.dfa,
                             profile->policy.start[AA_CLASS_MOUNT],
                             new_name);
        state = aa_dfa_null_transition(profile->policy.dfa, state);
        state = aa_dfa_match(profile->policy.dfa, state, old_name);
        perms = compute_mnt_perms(profile->policy.dfa, state);

        if (AA_MAY_PIVOTROOT & perms.allow)
                error = 0;

audit:
        error = audit_mount(profile, OP_PIVOTROOT, new_name, old_name,
                            NULL, trans_name, 0, NULL, AA_MAY_PIVOTROOT,
                            &perms, info, error);
        if (error)
                return ERR_PTR(error);

        return aa_get_newest_label(&profile->label);
}

int aa_pivotroot(struct aa_label *label, const struct path *old_path,
                 const struct path *new_path)
{
        struct aa_profile *profile;
        struct aa_label *target = NULL;
        char *old_buffer = NULL, *new_buffer = NULL, *info = NULL;
        int error;

        AA_BUG(!label);
        AA_BUG(!old_path);
        AA_BUG(!new_path);

        get_buffers(old_buffer, new_buffer);
        target = fn_label_build(label, profile, GFP_ATOMIC,
                        build_pivotroot(profile, new_path, new_buffer,
                                        old_path, old_buffer));
        if (!target) {
                info = "label build failed";
                error = -ENOMEM;
                goto fail;
        } else if (!IS_ERR(target)) {
                error = aa_replace_current_label(target);
                if (error) {
                        /* TODO: audit target */
                        aa_put_label(target);
                        goto out;
                }
        } else
                /* already audited error */
                error = PTR_ERR(target);
out:
        put_buffers(old_buffer, new_buffer);

        return error;

fail:
        /* TODO: add back in auditing of new_name and old_name */
        error = fn_for_each(label, profile,
                        audit_mount(profile, OP_PIVOTROOT, NULL /*new_name */,
                                    NULL /* old_name */,
                                    NULL, NULL,
                                    0, NULL, AA_MAY_PIVOTROOT, &nullperms, info,
                                    error));
        goto out;
}