Linux 4.13.16

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

/*
 * AppArmor security module
 *
 * This file contains AppArmor mediation of files
 *
 * Copyright (C) 1998-2008 Novell/SUSE
 * Copyright 2009-2010 Canonical Ltd.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, version 2 of the
 * License.
 */

#include <linux/tty.h>
#include <linux/fdtable.h>
#include <linux/file.h>

#include "include/apparmor.h"
#include "include/audit.h"
#include "include/context.h"
#include "include/file.h"
#include "include/match.h"
#include "include/path.h"
#include "include/policy.h"
#include "include/label.h"

static u32 map_mask_to_chr_mask(u32 mask)
{
        u32 m = mask & PERMS_CHRS_MASK;

        if (mask & AA_MAY_GETATTR)
                m |= MAY_READ;
        if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
                m |= MAY_WRITE;

        return m;
}

/**
 * audit_file_mask - convert mask to permission string
 * @buffer: buffer to write string to (NOT NULL)
 * @mask: permission mask to convert
 */
static void audit_file_mask(struct audit_buffer *ab, u32 mask)
{
        char str[10];

        aa_perm_mask_to_str(str, aa_file_perm_chrs, map_mask_to_chr_mask(mask));
        audit_log_string(ab, str);
}

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

        if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
                audit_log_format(ab, " requested_mask=");
                audit_file_mask(ab, aad(sa)->request);
        }
        if (aad(sa)->denied & AA_AUDIT_FILE_MASK) {
                audit_log_format(ab, " denied_mask=");
                audit_file_mask(ab, aad(sa)->denied);
        }
        if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
                audit_log_format(ab, " fsuid=%d",
                                 from_kuid(&init_user_ns, fsuid));
                audit_log_format(ab, " ouid=%d",
                                 from_kuid(&init_user_ns, aad(sa)->fs.ouid));
        }

        if (aad(sa)->peer) {
                audit_log_format(ab, " target=");
                aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
                                FLAG_VIEW_SUBNS, GFP_ATOMIC);
        } else if (aad(sa)->fs.target) {
                audit_log_format(ab, " target=");
                audit_log_untrustedstring(ab, aad(sa)->fs.target);
        }
}

/**
 * aa_audit_file - handle the auditing of file operations
 * @profile: the profile being enforced  (NOT NULL)
 * @perms: the permissions computed for the request (NOT NULL)
 * @op: operation being mediated
 * @request: permissions requested
 * @name: name of object being mediated (MAYBE NULL)
 * @target: name of target (MAYBE NULL)
 * @tlabel: target label (MAY BE NULL)
 * @ouid: object uid
 * @info: extra information message (MAYBE NULL)
 * @error: 0 if operation allowed else failure error code
 *
 * Returns: %0 or error on failure
 */
int aa_audit_file(struct aa_profile *profile, struct aa_perms *perms,
                  const char *op, u32 request, const char *name,
                  const char *target, struct aa_label *tlabel,
                  kuid_t ouid, const char *info, int error)
{
        int type = AUDIT_APPARMOR_AUTO;
        DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, op);

        sa.u.tsk = NULL;
        aad(&sa)->request = request;
        aad(&sa)->name = name;
        aad(&sa)->fs.target = target;
        aad(&sa)->peer = tlabel;
        aad(&sa)->fs.ouid = ouid;
        aad(&sa)->info = info;
        aad(&sa)->error = error;
        sa.u.tsk = NULL;

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

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

                /* mask off perms that are not being force audited */
                aad(&sa)->request &= mask;

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

                if (aad(&sa)->request & perms->kill)
                        type = AUDIT_APPARMOR_KILL;

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

                if (!aad(&sa)->request)
                        return aad(&sa)->error;
        }

        aad(&sa)->denied = aad(&sa)->request & ~perms->allow;
        return aa_audit(type, profile, &sa, file_audit_cb);
}

/**
 * is_deleted - test if a file has been completely unlinked
 * @dentry: dentry of file to test for deletion  (NOT NULL)
 *
 * Returns: %1 if deleted else %0
 */
static inline bool is_deleted(struct dentry *dentry)
{
        if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0)
                return 1;
        return 0;
}

static int path_name(const char *op, struct aa_label *label,
                     const struct path *path, int flags, char *buffer,
                     const char **name, struct path_cond *cond, u32 request)
{
        struct aa_profile *profile;
        const char *info = NULL;
        int error;

        error = aa_path_name(path, flags, buffer, name, &info,
                             labels_profile(label)->disconnected);
        if (error) {
                fn_for_each_confined(label, profile,
                        aa_audit_file(profile, &nullperms, op, request, *name,
                                      NULL, NULL, cond->uid, info, error));
                return error;
        }

        return 0;
}

/**
 * map_old_perms - map old file perms layout to the new layout
 * @old: permission set in old mapping
 *
 * Returns: new permission mapping
 */
static u32 map_old_perms(u32 old)
{
        u32 new = old & 0xf;
        if (old & MAY_READ)
                new |= AA_MAY_GETATTR | AA_MAY_OPEN;
        if (old & MAY_WRITE)
                new |= AA_MAY_SETATTR | AA_MAY_CREATE | AA_MAY_DELETE |
                       AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_OPEN;
        if (old & 0x10)
                new |= AA_MAY_LINK;
        /* the old mapping lock and link_subset flags where overlaid
         * and use was determined by part of a pair that they were in
         */
        if (old & 0x20)
                new |= AA_MAY_LOCK | AA_LINK_SUBSET;
        if (old & 0x40) /* AA_EXEC_MMAP */
                new |= AA_EXEC_MMAP;

        return new;
}

/**
 * aa_compute_fperms - convert dfa compressed perms to internal perms
 * @dfa: dfa to compute perms for   (NOT NULL)
 * @state: state in dfa
 * @cond:  conditions to consider  (NOT NULL)
 *
 * TODO: convert from dfa + state to permission entry, do computation conversion
 *       at load time.
 *
 * Returns: computed permission set
 */
struct aa_perms aa_compute_fperms(struct aa_dfa *dfa, unsigned int state,
                                  struct path_cond *cond)
{
        struct aa_perms perms;

        /* FIXME: change over to new dfa format
         * currently file perms are encoded in the dfa, new format
         * splits the permissions from the dfa.  This mapping can be
         * done at profile load
         */
        perms.deny = 0;
        perms.kill = perms.stop = 0;
        perms.complain = perms.cond = 0;
        perms.hide = 0;
        perms.prompt = 0;

        if (uid_eq(current_fsuid(), cond->uid)) {
                perms.allow = map_old_perms(dfa_user_allow(dfa, state));
                perms.audit = map_old_perms(dfa_user_audit(dfa, state));
                perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
                perms.xindex = dfa_user_xindex(dfa, state);
        } else {
                perms.allow = map_old_perms(dfa_other_allow(dfa, state));
                perms.audit = map_old_perms(dfa_other_audit(dfa, state));
                perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
                perms.xindex = dfa_other_xindex(dfa, state);
        }
        perms.allow |= AA_MAY_GETATTR;

        /* change_profile wasn't determined by ownership in old mapping */
        if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
                perms.allow |= AA_MAY_CHANGE_PROFILE;
        if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
                perms.allow |= AA_MAY_ONEXEC;

        return perms;
}

/**
 * aa_str_perms - find permission that match @name
 * @dfa: to match against  (MAYBE NULL)
 * @state: state to start matching in
 * @name: string to match against dfa  (NOT NULL)
 * @cond: conditions to consider for permission set computation  (NOT NULL)
 * @perms: Returns - the permissions found when matching @name
 *
 * Returns: the final state in @dfa when beginning @start and walking @name
 */
unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
                          const char *name, struct path_cond *cond,
                          struct aa_perms *perms)
{
        unsigned int state;
        state = aa_dfa_match(dfa, start, name);
        *perms = aa_compute_fperms(dfa, state, cond);

        return state;
}

int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name,
                   u32 request, struct path_cond *cond, int flags,
                   struct aa_perms *perms)
{
        int e = 0;

        if (profile_unconfined(profile))
                return 0;
        aa_str_perms(profile->file.dfa, profile->file.start, name, cond, perms);
        if (request & ~perms->allow)
                e = -EACCES;
        return aa_audit_file(profile, perms, op, request, name, NULL, NULL,
                             cond->uid, NULL, e);
}


static int profile_path_perm(const char *op, struct aa_profile *profile,
                             const struct path *path, char *buffer, u32 request,
                             struct path_cond *cond, int flags,
                             struct aa_perms *perms)
{
        const char *name;
        int error;

        if (profile_unconfined(profile))
                return 0;

        error = path_name(op, &profile->label, path,
                          flags | profile->path_flags, buffer, &name, cond,
                          request);
        if (error)
                return error;
        return __aa_path_perm(op, profile, name, request, cond, flags,
                              perms);
}

/**
 * aa_path_perm - do permissions check & audit for @path
 * @op: operation being checked
 * @label: profile being enforced  (NOT NULL)
 * @path: path to check permissions of  (NOT NULL)
 * @flags: any additional path flags beyond what the profile specifies
 * @request: requested permissions
 * @cond: conditional info for this request  (NOT NULL)
 *
 * Returns: %0 else error if access denied or other error
 */
int aa_path_perm(const char *op, struct aa_label *label,
                 const struct path *path, int flags, u32 request,
                 struct path_cond *cond)
{
        struct aa_perms perms = {};
        struct aa_profile *profile;
        char *buffer = NULL;
        int error;

        flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
                                                                0);
        get_buffers(buffer);
        error = fn_for_each_confined(label, profile,
                        profile_path_perm(op, profile, path, buffer, request,
                                          cond, flags, &perms));

        put_buffers(buffer);

        return error;
}

/**
 * xindex_is_subset - helper for aa_path_link
 * @link: link permission set
 * @target: target permission set
 *
 * test target x permissions are equal OR a subset of link x permissions
 * this is done as part of the subset test, where a hardlink must have
 * a subset of permissions that the target has.
 *
 * Returns: %1 if subset else %0
 */
static inline bool xindex_is_subset(u32 link, u32 target)
{
        if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
            ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
                return 0;

        return 1;
}

static int profile_path_link(struct aa_profile *profile,
                             const struct path *link, char *buffer,
                             const struct path *target, char *buffer2,
                             struct path_cond *cond)
{
        const char *lname, *tname = NULL;
        struct aa_perms lperms = {}, perms;
        const char *info = NULL;
        u32 request = AA_MAY_LINK;
        unsigned int state;
        int error;

        error = path_name(OP_LINK, &profile->label, link, profile->path_flags,
                          buffer, &lname, cond, AA_MAY_LINK);
        if (error)
                goto audit;

        /* buffer2 freed below, tname is pointer in buffer2 */
        error = path_name(OP_LINK, &profile->label, target, profile->path_flags,
                          buffer2, &tname, cond, AA_MAY_LINK);
        if (error)
                goto audit;

        error = -EACCES;
        /* aa_str_perms - handles the case of the dfa being NULL */
        state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
                             cond, &lperms);

        if (!(lperms.allow & AA_MAY_LINK))
                goto audit;

        /* test to see if target can be paired with link */
        state = aa_dfa_null_transition(profile->file.dfa, state);
        aa_str_perms(profile->file.dfa, state, tname, cond, &perms);

        /* force audit/quiet masks for link are stored in the second entry
         * in the link pair.
         */
        lperms.audit = perms.audit;
        lperms.quiet = perms.quiet;
        lperms.kill = perms.kill;

        if (!(perms.allow & AA_MAY_LINK)) {
                info = "target restricted";
                lperms = perms;
                goto audit;
        }

        /* done if link subset test is not required */
        if (!(perms.allow & AA_LINK_SUBSET))
                goto done_tests;

        /* Do link perm subset test requiring allowed permission on link are
         * a subset of the allowed permissions on target.
         */
        aa_str_perms(profile->file.dfa, profile->file.start, tname, cond,
                     &perms);

        /* AA_MAY_LINK is not considered in the subset test */
        request = lperms.allow & ~AA_MAY_LINK;
        lperms.allow &= perms.allow | AA_MAY_LINK;

        request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
        if (request & ~lperms.allow) {
                goto audit;
        } else if ((lperms.allow & MAY_EXEC) &&
                   !xindex_is_subset(lperms.xindex, perms.xindex)) {
                lperms.allow &= ~MAY_EXEC;
                request |= MAY_EXEC;
                info = "link not subset of target";
                goto audit;
        }

done_tests:
        error = 0;

audit:
        return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
                             NULL, cond->uid, info, error);
}

/**
 * aa_path_link - Handle hard link permission check
 * @label: the label being enforced  (NOT NULL)
 * @old_dentry: the target dentry  (NOT NULL)
 * @new_dir: directory the new link will be created in  (NOT NULL)
 * @new_dentry: the link being created  (NOT NULL)
 *
 * Handle the permission test for a link & target pair.  Permission
 * is encoded as a pair where the link permission is determined
 * first, and if allowed, the target is tested.  The target test
 * is done from the point of the link match (not start of DFA)
 * making the target permission dependent on the link permission match.
 *
 * The subset test if required forces that permissions granted
 * on link are a subset of the permission granted to target.
 *
 * Returns: %0 if allowed else error
 */
int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
                 const struct path *new_dir, struct dentry *new_dentry)
{
        struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
        struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
        struct path_cond cond = {
                d_backing_inode(old_dentry)->i_uid,
                d_backing_inode(old_dentry)->i_mode
        };
        char *buffer = NULL, *buffer2 = NULL;
        struct aa_profile *profile;
        int error;

        /* buffer freed below, lname is pointer in buffer */
        get_buffers(buffer, buffer2);
        error = fn_for_each_confined(label, profile,
                        profile_path_link(profile, &link, buffer, &target,
                                          buffer2, &cond));
        put_buffers(buffer, buffer2);

        return error;
}

static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
                            u32 request)
{
        struct aa_label *l, *old;

        /* update caching of label on file_ctx */
        spin_lock(&fctx->lock);
        old = rcu_dereference_protected(fctx->label,
                                        spin_is_locked(&fctx->lock));
        l = aa_label_merge(old, label, GFP_ATOMIC);
        if (l) {
                if (l != old) {
                        rcu_assign_pointer(fctx->label, l);
                        aa_put_label(old);
                } else
                        aa_put_label(l);
                fctx->allow |= request;
        }
        spin_unlock(&fctx->lock);
}

static int __file_path_perm(const char *op, struct aa_label *label,
                            struct aa_label *flabel, struct file *file,
                            u32 request, u32 denied)
{
        struct aa_profile *profile;
        struct aa_perms perms = {};
        struct path_cond cond = {
                .uid = file_inode(file)->i_uid,
                .mode = file_inode(file)->i_mode
        };
        char *buffer;
        int flags, error;

        /* revalidation due to label out of date. No revocation at this time */
        if (!denied && aa_label_is_subset(flabel, label))
                /* TODO: check for revocation on stale profiles */
                return 0;

        flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
        get_buffers(buffer);

        /* check every profile in task label not in current cache */
        error = fn_for_each_not_in_set(flabel, label, profile,
                        profile_path_perm(op, profile, &file->f_path, buffer,
                                          request, &cond, flags, &perms));
        if (denied && !error) {
                /*
                 * check every profile in file label that was not tested
                 * in the initial check above.
                 *
                 * TODO: cache full perms so this only happens because of
                 * conditionals
                 * TODO: don't audit here
                 */
                if (label == flabel)
                        error = fn_for_each(label, profile,
                                profile_path_perm(op, profile, &file->f_path,
                                                  buffer, request, &cond, flags,
                                                  &perms));
                else
                        error = fn_for_each_not_in_set(label, flabel, profile,
                                profile_path_perm(op, profile, &file->f_path,
                                                  buffer, request, &cond, flags,
                                                  &perms));
        }
        if (!error)
                update_file_ctx(file_ctx(file), label, request);

        put_buffers(buffer);

        return error;
}

/**
 * aa_file_perm - do permission revalidation check & audit for @file
 * @op: operation being checked
 * @label: label being enforced   (NOT NULL)
 * @file: file to revalidate access permissions on  (NOT NULL)
 * @request: requested permissions
 *
 * Returns: %0 if access allowed else error
 */
int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
                 u32 request)
{
        struct aa_file_ctx *fctx;
        struct aa_label *flabel;
        u32 denied;
        int error = 0;

        AA_BUG(!label);
        AA_BUG(!file);

        fctx = file_ctx(file);

        rcu_read_lock();
        flabel  = rcu_dereference(fctx->label);
        AA_BUG(!flabel);

        /* revalidate access, if task is unconfined, or the cached cred
         * doesn't match or if the request is for more permissions than
         * was granted.
         *
         * Note: the test for !unconfined(flabel) is to handle file
         *       delegation from unconfined tasks
         */
        denied = request & ~fctx->allow;
        if (unconfined(label) || unconfined(flabel) ||
            (!denied && aa_label_is_subset(flabel, label)))
                goto done;

        /* TODO: label cross check */

        if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
                error = __file_path_perm(op, label, flabel, file, request,
                                         denied);

done:
        rcu_read_unlock();

        return error;
}

static void revalidate_tty(struct aa_label *label)
{
        struct tty_struct *tty;
        int drop_tty = 0;

        tty = get_current_tty();
        if (!tty)
                return;

        spin_lock(&tty->files_lock);
        if (!list_empty(&tty->tty_files)) {
                struct tty_file_private *file_priv;
                struct file *file;
                /* TODO: Revalidate access to controlling tty. */
                file_priv = list_first_entry(&tty->tty_files,
                                             struct tty_file_private, list);
                file = file_priv->file;

                if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE))
                        drop_tty = 1;
        }
        spin_unlock(&tty->files_lock);
        tty_kref_put(tty);

        if (drop_tty)
                no_tty();
}

static int match_file(const void *p, struct file *file, unsigned int fd)
{
        struct aa_label *label = (struct aa_label *)p;

        if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file)))
                return fd + 1;
        return 0;
}


/* based on selinux's flush_unauthorized_files */
void aa_inherit_files(const struct cred *cred, struct files_struct *files)
{
        struct aa_label *label = aa_get_newest_cred_label(cred);
        struct file *devnull = NULL;
        unsigned int n;

        revalidate_tty(label);

        /* Revalidate access to inherited open files. */
        n = iterate_fd(files, 0, match_file, label);
        if (!n) /* none found? */
                goto out;

        devnull = dentry_open(&aa_null, O_RDWR, cred);
        if (IS_ERR(devnull))
                devnull = NULL;
        /* replace all the matching ones with this */
        do {
                replace_fd(n - 1, devnull, 0);
        } while ((n = iterate_fd(files, n, match_file, label)) != 0);
        if (devnull)
                fput(devnull);
out:
        aa_put_label(label);
}