/* SPDX-License-Identifier: LGPL-2.1+ */

#include <errno.h>

#include <fcntl.h>

#include <stdbool.h>

#include <stdlib.h>

#include <sys/stat.h>

#include <syslog.h>

#include <unistd.h>

#include "alloc-util.h"

#include "base-filesystem.h"

#include "fd-util.h"

#include "log.h"

#include "macro.h"

#include "nulstr-util.h"

#include "path-util.h"

#include "string-util.h"

#include "umask-util.h"

#include "user-util.h"

typedef struct BaseFilesystem {

        const char *dir;

        mode_t mode;

        const char *target;

        const char *exists;

        bool ignore_failure;

} BaseFilesystem;

static const BaseFilesystem table[] = {

        { "bin",      0, "usr/bin\0",                  NULL },

        { "lib",      0, "usr/lib\0",                  NULL },

        { "root",  0755, NULL,                         NULL, true },

        { "sbin",     0, "usr/sbin\0",                 NULL },

        { "usr",   0755, NULL,                         NULL },

        { "var",   0755, NULL,                         NULL },

        { "etc",   0755, NULL,                         NULL },

        { "proc",  0755, NULL,                         NULL, true },

        { "sys",   0755, NULL,                         NULL, true },

        { "dev",   0755, NULL,                         NULL, true },

#if defined(__i386__) || defined(__x86_64__)

        { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"

                         "usr/lib64\0",                "ld-linux-x86-64.so.2" },

#endif

};

int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {

        _cleanup_close_ int fd = -1;

        size_t i;

        int r;

        fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);

        if (fd < 0)

                return log_error_errno(errno, "Failed to open root file system: %m");

        for (i = 0; i < ELEMENTSOF(table); i ++) {

                if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)

                        continue;

                if (table[i].target) {

                        const char *target = NULL, *s;

                        /* check if one of the targets exists */

                        NULSTR_FOREACH(s, table[i].target) {

                                if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)

                                        continue;

                                /* check if a specific file exists at the target path */

                                if (table[i].exists) {

                                        _cleanup_free_ char *p = NULL;

                                        p = path_join(s, table[i].exists);

                                        if (!p)

                                                return log_oom();

                                        if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)

                                                continue;

                                }

                                target = s;

                                break;

                        }

                        if (!target)

                                continue;

                        if (symlinkat(target, fd, table[i].dir) < 0) {

                                log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,

                                               "Failed to create symlink at %s/%s: %m", root, table[i].dir);

                                if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)

                                        continue;

                                return -errno;

                        }

                        if (uid_is_valid(uid) || gid_is_valid(gid)) {

                                if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)

                                        return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);

                        }

                        continue;

                }

                RUN_WITH_UMASK(0000)

                        r = mkdirat(fd, table[i].dir, table[i].mode);

                if (r < 0) {

                        log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,

                                       "Failed to create directory at %s/%s: %m", root, table[i].dir);

                        if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)

                                continue;

                        return -errno;

                }

                if (uid != UID_INVALID || gid != UID_INVALID) {

                        if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)

                                return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);

                }

        }

        return 0;

}