setnsfpn.cpp

/* Cydia - iPhone UIKit Front-End for Debian APT
 * Copyright (C) 2008-2015  Jay Freeman (saurik)
*/

/* GNU General Public License, Version 3 {{{ */
/*
 * Cydia 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, either version 3 of the License,
 * or (at your option) any later version.
 *
 * Cydia is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Cydia.  If not, see <http://www.gnu.org/licenses/>.
**/
/* }}} */

#include <fcntl.h>
#include <dirent.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>

#define _syscall(expr) ({ typeof(expr) _value; for (;;) { \
    _value = (expr); \
    if ((long) _value != -1) \
        break; \
    if (errno != EINTR) { \
        perror(#expr); \
        return -1; \
    } \
} _value; })

extern "C" int __getdirentries64(int, char *, int, long *);

enum Recurse {
    RecurseYes,
    RecurseNo,
    RecurseMaybe,
};

struct File {
    int fd_;

    File(int fd);
    ~File();

    operator int() const;
};

File::File(int fd) :
    fd_(fd)
{
}

File::~File() {
    close(fd_);
}

File::operator int() const {
    return fd_;
}

static int setnsfpn(const char *path, size_t before, Recurse recurse) {
    File fd(_syscall(open_dprotected_np(path, O_RDONLY | O_SYMLINK, 0, O_DP_GETRAWENCRYPTED)));

    if (recurse == RecurseMaybe) {
        struct stat stat;
        _syscall(fstat(fd, &stat));
        switch (stat.st_mode & S_IFMT) {
            case S_IFLNK:
                return 0;
            default:
                return -1;

            case S_IFDIR:
                recurse = RecurseYes;
                break;
            case S_IFREG:
                recurse = RecurseNo;
                break;
        }
    }

    int mode(_syscall(fcntl(fd, F_GETPROTECTIONCLASS)));
    if (mode == 4)
        return 0;

    if (recurse == RecurseYes)
        for (long address(0);;) {
            char buffer[4096];
            int size(_syscall(__getdirentries64(fd, buffer, sizeof(buffer), &address)));
            if (size == 0)
                break;

            const char *next(buffer), *stop(next + size);
            while (next != stop) {
                const dirent *dir(reinterpret_cast<const dirent *>(next));
                const char *name(dir->d_name);
                size_t after(strlen(name));

                if (dir->d_ino == 0);
                else if (after == 1 && name[0] == '.');
                else if (after == 2 && name[0] == '.' && name[1] == '.');
                else {
                    size_t both(before + 1 + after);
                    char sub[both + 1];
                    memcpy(sub, path, before);
                    sub[before] = '/';
                    memcpy(sub + before + 1, name, after);
                    sub[both] = '\0';

                    switch (dir->d_type) {
                        case DT_LNK:
                            break;
                        default:
                            return -1;

                        case DT_DIR:
                            if (setnsfpn(sub, both, RecurseYes) != 0)
                                return -1;
                            break;
                        case DT_REG:
                            if (setnsfpn(sub, both, RecurseNo) != 0)
                                return -1;
                            break;
                    }
                }

                next += dir->d_reclen;
            }
        }

    _syscall(fcntl(fd, F_SETPROTECTIONCLASS, 4));
    return 0;
}

int main(int argc, const char *argv[]) {
    return setnsfpn(argv[1], strlen(argv[1]), RecurseMaybe);
}