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

struct file_perms nullperms;


/**
 * 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];

        char *m = str;

        if (mask & AA_EXEC_MMAP)
                *m++ = 'm';
        if (mask & (MAY_READ | AA_MAY_META_READ))
                *m++ = 'r';
        if (mask & (MAY_WRITE | AA_MAY_META_WRITE | AA_MAY_CHMOD |
                    AA_MAY_CHOWN))
                *m++ = 'w';
        else if (mask & MAY_APPEND)
                *m++ = 'a';
        if (mask & AA_MAY_CREATE)
                *m++ = 'c';
        if (mask & AA_MAY_DELETE)
                *m++ = 'd';
        if (mask & AA_MAY_LINK)
                *m++ = 'l';
        if (mask & AA_MAY_LOCK)
                *m++ = 'k';
        if (mask & MAY_EXEC)
                *m++ = 'x';
        *m = '\0';

        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;
        uid_t fsuid = current_fsuid();

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

        if (sa->aad->fs.target) {
                audit_log_format(ab, " target=");
                audit_log_untrustedstring(ab, sa->aad->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)
 * @gfp: allocation flags
 * @op: operation being mediated
 * @request: permissions requested
 * @name: name of object being mediated (MAYBE NULL)
 * @target: name of target (MAYBE 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 file_perms *perms,
                  gfp_t gfp, int op, u32 request, const char *name,
                  const char *target, uid_t ouid, const char *info, int error)
{
        int type = AUDIT_APPARMOR_AUTO;
        struct common_audit_data sa;
        struct apparmor_audit_data aad = {0,};
        COMMON_AUDIT_DATA_INIT(&sa, NONE);
        sa.aad = &aad;
        aad.op = op,
        aad.fs.request = request;
        aad.name = name;
        aad.fs.target = target;
        aad.fs.ouid = ouid;
        aad.info = info;
        aad.error = error;

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

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

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

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

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

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

                if (!sa.aad->fs.request)
                        return COMPLAIN_MODE(profile) ? 0 : sa.aad->error;
        }

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

/**
 * 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_META_READ;
        if (old & MAY_WRITE)
                new |= AA_MAY_META_WRITE | AA_MAY_CREATE | AA_MAY_DELETE |
                        AA_MAY_CHMOD | AA_MAY_CHOWN;
        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;
}

/**
 * compute_perms - 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
 */
static struct file_perms compute_perms(struct aa_dfa *dfa, unsigned int state,
                                       struct path_cond *cond)
{
        struct file_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.kill = 0;

        if (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_META_READ;

        /* 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 file_perms *perms)
{
        unsigned int state;
        if (!dfa) {
                *perms = nullperms;
                return DFA_NOMATCH;
        }

        state = aa_dfa_match(dfa, start, name);
        *perms = compute_perms(dfa, state, cond);

        return state;
}

/**
 * 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) && dentry->d_inode->i_nlink == 0)
                return 1;
        return 0;
}

/**
 * aa_path_perm - do permissions check & audit for @path
 * @op: operation being checked
 * @profile: 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(int op, struct aa_profile *profile, struct path *path,
                 int flags, u32 request, struct path_cond *cond)
{
        char *buffer = NULL;
        struct file_perms perms = {};
        const char *name, *info = NULL;
        int error;

        flags |= profile->path_flags | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
        error = aa_path_name(path, flags, &buffer, &name, &info);
        if (error) {
                if (error == -ENOENT && is_deleted(path->dentry)) {
                        /* Access to open files that are deleted are
                         * give a pass (implicit delegation)
                         */
                        error = 0;
                        info = NULL;
                        perms.allow = request;
                }
        } else {
                aa_str_perms(profile->file.dfa, profile->file.start, name, cond,
                             &perms);
                if (request & ~perms.allow)
                        error = -EACCES;
        }
        error = aa_audit_file(profile, &perms, GFP_KERNEL, op, request, name,
                              NULL, cond->uid, info, error);
        kfree(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;
}

/**
 * aa_path_link - Handle hard link permission check
 * @profile: the profile 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_profile *profile, struct dentry *old_dentry,
                 struct path *new_dir, struct dentry *new_dentry)
{
        struct path link = { new_dir->mnt, new_dentry };
        struct path target = { new_dir->mnt, old_dentry };
        struct path_cond cond = {
                old_dentry->d_inode->i_uid,
                old_dentry->d_inode->i_mode
        };
        char *buffer = NULL, *buffer2 = NULL;
        const char *lname, *tname = NULL, *info = NULL;
        struct file_perms lperms, perms;
        u32 request = AA_MAY_LINK;
        unsigned int state;
        int error;

        lperms = nullperms;

        /* buffer freed below, lname is pointer in buffer */
        error = aa_path_name(&link, profile->path_flags, &buffer, &lname,
                             &info);
        if (error)
                goto audit;

        /* buffer2 freed below, tname is pointer in buffer2 */
        error = aa_path_name(&target, profile->path_flags, &buffer2, &tname,
                             &info);
        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";
                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:
        error = aa_audit_file(profile, &lperms, GFP_KERNEL, OP_LINK, request,
                              lname, tname, cond.uid, info, error);
        kfree(buffer);
        kfree(buffer2);

        return error;
}

/**
 * aa_file_perm - do permission revalidation check & audit for @file
 * @op: operation being checked
 * @profile: profile 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(int op, struct aa_profile *profile, struct file *file,
                 u32 request)
{
        struct path_cond cond = {
                .uid = file->f_path.dentry->d_inode->i_uid,
                .mode = file->f_path.dentry->d_inode->i_mode
        };

        return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
                            request, &cond);
}