fsvs-chrooter.c

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/************************************************************************
 * Copyright (C) 2007 Philipp Marek.
 *
 * This program is free software;  you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 ************************************************************************/


#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>

#include "../config.h"
#include "../interface.h"


#define STOP(...)                                                       \
    do {                                                                \
        fprintf(stderr, __VA_ARGS__);                                       \
        fprintf(stderr, "\n%s (%d)\n"                                       \
                "fsvs-chrooter (licensed under the GPLv3), (C) by Ph. Marek;"   \
                " version " FSVS_VERSION "\n",                                                              \
        strerror(errno), errno);                                            \
        exit(errno);                                                        \
    } while (0)


void open_keep_set(char *fn, char *env)
{
    char stg[10];
    int hdl;
    int flags;
    int status;


    hdl=open(fn, O_RDONLY);
    if (hdl<0) STOP("Cannot open directory %s", fn);

    flags=fcntl(hdl, F_GETFD);
    if ( flags == -1 )
        STOP("Cannot get fd flags");

    flags &= ~FD_CLOEXEC;
    status=fcntl(hdl, F_SETFD, flags);
    if ( flags == -1 )
        STOP("Cannot set fd flags");

    sprintf(stg,"%d",hdl);
  setenv(env, stg, 1);
}


int main(int argc, char *args[])
{
    errno=0;

    if ( getenv(CHROOTER_LIBS_ENV) == NULL)
        STOP("Please specify in %s which libraries should be preloaded.",
                CHROOTER_LIBS_ENV);

    open_keep_set("/", CHROOTER_ROOT_ENV);
    open_keep_set(".", CHROOTER_CWD_ENV);

    if (chroot(CHROOTER_JAIL)==-1)
        STOP("Cannot do chroot(%s)", CHROOTER_JAIL);

    if (chdir("/") == -1)
        STOP("Cannot do chdir(/) call");

    execvp("fsvs",args);
    STOP("Executing fsvs in the chroot jail failed");

    return 0;
}

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