src/basic/chase-symlinks.h

/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once

#include <dirent.h>
#include <stdio.h>

#include "stat-util.h"

typedef enum ChaseSymlinksFlags {
        CHASE_PREFIX_ROOT        = 1 << 0, /* The specified path will be prefixed by the specified root before beginning the iteration */
        CHASE_NONEXISTENT        = 1 << 1, /* It's OK if the path doesn't actually exist. */
        CHASE_NO_AUTOFS          = 1 << 2, /* Return -EREMOTE if autofs mount point found */
        CHASE_SAFE               = 1 << 3, /* Return -EPERM if we ever traverse from unprivileged to privileged files or directories */
        CHASE_TRAIL_SLASH        = 1 << 4, /* Any trailing slash will be preserved */
        CHASE_STEP               = 1 << 5, /* Just execute a single step of the normalization */
        CHASE_NOFOLLOW           = 1 << 6, /* Do not follow the path's right-most component. With ret_fd, when the path's
                                            * right-most component refers to symlink, return O_PATH fd of the symlink. */
        CHASE_WARN               = 1 << 7, /* Emit an appropriate warning when an error is encountered.
                                            * Note: this may do an NSS lookup, hence this flag cannot be used in PID 1. */
        CHASE_AT_RESOLVE_IN_ROOT = 1 << 8, /* Same as openat2()'s RESOLVE_IN_ROOT flag, symlinks are resolved
                                            * relative to the given directory fd instead of root. */
        CHASE_PROHIBIT_SYMLINKS  = 1 << 9, /* Refuse all symlinks */
} ChaseSymlinksFlags;

bool unsafe_transition(const struct stat *a, const struct stat *b);

/* How many iterations to execute before returning -ELOOP */
#define CHASE_SYMLINKS_MAX 32

int chase_symlinks(const char *path_with_prefix, const char *root, ChaseSymlinksFlags chase_flags, char **ret_path, int *ret_fd);

int chase_symlinks_and_open(const char *path, const char *root, ChaseSymlinksFlags chase_flags, int open_flags, char **ret_path);
int chase_symlinks_and_opendir(const char *path, const char *root, ChaseSymlinksFlags chase_flags, char **ret_path, DIR **ret_dir);
int chase_symlinks_and_stat(const char *path, const char *root, ChaseSymlinksFlags chase_flags, char **ret_path, struct stat *ret_stat, int *ret_fd);
int chase_symlinks_and_access(const char *path, const char *root, ChaseSymlinksFlags chase_flags, int access_mode, char **ret_path, int *ret_fd);
int chase_symlinks_and_fopen_unlocked(const char *path, const char *root, ChaseSymlinksFlags chase_flags, const char *open_flags, char **ret_path, FILE **ret_file);
int chase_symlinks_and_unlink(const char *path, const char *root, ChaseSymlinksFlags chase_flags, int unlink_flags, char **ret_path);

int chase_symlinks_at(int dir_fd, const char *path, ChaseSymlinksFlags flags, char **ret_path, int *ret_fd);