runner.c

#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#ifndef __APPLE__
#include <seccomp.h>
#else
#warning "###### This judger can not work under OSX, installation is only for dev dependencies! #####"
#endif
#include <signal.h>
#include <errno.h>
#include <pwd.h>
#include <sched.h>
#include <grp.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <sys/types.h>

#include "runner.h"
#include "logger.h"

#define STACK_SIZE (2 * 1024 * 1024)


int set_timer(int sec, int ms, int is_cpu_time) {
    struct itimerval time_val;
    time_val.it_interval.tv_sec = time_val.it_interval.tv_usec = 0;
    time_val.it_value.tv_sec = sec;
    time_val.it_value.tv_usec = ms * 1000;
    if (setitimer(is_cpu_time ? ITIMER_VIRTUAL : ITIMER_REAL, &time_val, NULL)) {
        return SETITIMER_FAILED;
    }
    return SUCCESS;
}


int child_process(void *clone_args){
    FILE *log_fp = ((struct clone_args *)clone_args)->log_fp;
    struct config *config = ((struct clone_args *)clone_args)->config;
    FILE *in_file = NULL, *out_file = NULL, *err_file = NULL;
    struct rlimit memory_limit, cpu_time_rlimit;
    gid_t group_list[] = {config->gid};
#ifndef __APPLE__
    int i;
    int syscalls_whitelist[] = {SCMP_SYS(read), SCMP_SYS(fstat),
                                SCMP_SYS(mmap), SCMP_SYS(mprotect), 
                                SCMP_SYS(munmap), SCMP_SYS(open), 
                                SCMP_SYS(arch_prctl), SCMP_SYS(brk), 
                                SCMP_SYS(access), SCMP_SYS(exit_group), 
                                SCMP_SYS(close), SCMP_SYS(readlink), 
                                SCMP_SYS(sysinfo), SCMP_SYS(lseek)};
    int syscalls_whitelist_length = sizeof(syscalls_whitelist) / sizeof(int);
    scmp_filter_ctx ctx = NULL;
#endif
    // child process
    // On success, these system calls return 0.
    // On error, -1 is returned, and errno is set appropriately.
    if (config->max_memory != MEMORY_UNLIMITED) {
        memory_limit.rlim_cur = memory_limit.rlim_max = (rlim_t) (config->max_memory) * 2;
        if (setrlimit(RLIMIT_AS, &memory_limit) == -1) {
            LOG_FATAL(log_fp, "setrlimit memory failed, errno: %d", errno);
            ERROR(log_fp, SETRLIMIT_FAILED);
        }
    }
    if (config->max_cpu_time != CPU_TIME_UNLIMITED) {
        // cpu time
        if (set_timer(config->max_cpu_time / 1000, config->max_cpu_time % 1000, 1) != SUCCESS) {
            LOG_FATAL(log_fp, "set cpu time timer failed");
            ERROR(log_fp, SETITIMER_FAILED);
        }
        // real time
        if (set_timer(config->max_real_time / 1000, config->max_real_time % 1000, 0) != SUCCESS) {
            LOG_FATAL(log_fp, "set real time timer failed");
            ERROR(log_fp, SETITIMER_FAILED);
        }

        // child process can not inherit timeout rules from parent process defined by setitimer, so we use setrlimit to
        // control child process max running time
        cpu_time_rlimit.rlim_cur = cpu_time_rlimit.rlim_max = (config->max_cpu_time + 1000) / 1000;
        if (setrlimit(RLIMIT_CPU, &cpu_time_rlimit) == -1) {
            LOG_FATAL(log_fp, "setrlimit cpu time failed, errno: %d", errno);
            ERROR(log_fp, SETRLIMIT_FAILED);
        }
    }

    // read stdin from in file
    // On success, these system calls return the new descriptor. 
    // On error, -1 is returned, and errno is set appropriately.
    if (config->in_file != NULL) {
        if ((in_file = fopen(config->in_file, "r")) == NULL) {
            LOG_FATAL(log_fp, "failed to open stdin redirect file");
            ERROR(log_fp, DUP2_FAILED);
        }
        if (dup2(fileno(in_file), fileno(stdin)) == -1) {
            LOG_FATAL(log_fp, "dup2 stdin failed, errno: %d", errno);
            ERROR(log_fp, DUP2_FAILED);
        }
    }
    // write stdout to out file
    if (config->out_file != NULL) {
        if ((out_file = fopen(config->out_file, "w")) == NULL) {
            LOG_FATAL(log_fp, "failed to open stdout redirect file");
            ERROR(log_fp, DUP2_FAILED);
        }
        if (dup2(fileno(out_file), fileno(stdout)) == -1) {
            LOG_FATAL(log_fp, "dup2 stdout failed, errno: %d", errno);
            ERROR(log_fp, DUP2_FAILED);
        }
    }
    // write stderr to err file
    if (config->err_file != NULL) {
        // if err_file and out_file are the same path, we use out_file pointer as err_file pointer, to avoid conflict
        if (strcmp(config->out_file, config->err_file) == 0) {
            err_file = out_file;
        }
        else {
            if ((err_file = fopen(config->err_file, "w")) == NULL) {
                LOG_FATAL(log_fp, "failed to open stderr redirect file");
                ERROR(log_fp, DUP2_FAILED);
            }
        }
        if (dup2(fileno(err_file), fileno(stderr)) == -1) {
            LOG_FATAL(log_fp, "dup2 stdout failed, errno: %d", errno);
            ERROR(log_fp, DUP2_FAILED);
        }
    }
    if (config->gid != -1 && (setgid(config->gid) == -1 || setgroups(sizeof(group_list) / sizeof(gid_t), group_list) == -1)) {
        LOG_FATAL(log_fp, "setgid failed, errno: %d", errno);
        ERROR(log_fp, SET_GID_FAILED);
    }
    if (config->uid != -1 && setuid(config->uid) == -1) {
        LOG_FATAL(log_fp, "setuid failed, errno: %d", errno);
        ERROR(log_fp, SET_UID_FAILED);
    }
#ifndef __APPLE__
    if (config->use_sandbox != 0) {
        // load seccomp rules
        ctx = seccomp_init(SCMP_ACT_KILL);
        if (!ctx) {
            LOG_FATAL(log_fp, "init seccomp failed");
            ERROR(log_fp, LOAD_SECCOMP_FAILED);
        }
        for (i = 0; i < syscalls_whitelist_length; i++) {
            if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, syscalls_whitelist[i], 0) != 0) {
                LOG_FATAL(log_fp, "load syscall white list failed");
                ERROR(log_fp, LOAD_SECCOMP_FAILED);
            }
        }
        // add extra rule for execve
        if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(execve), 1, SCMP_A0(SCMP_CMP_EQ, (scmp_datum_t)(config->path))) != 0) {
            LOG_FATAL(log_fp, "load execve rule failed");
            ERROR(log_fp, LOAD_SECCOMP_FAILED);
        }
        // only fd 0 1 2 are allowed
        if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1, SCMP_A0(SCMP_CMP_LE, 2)) != 0) {
            LOG_FATAL(log_fp, "load dup2 rule failed");
            ERROR(log_fp, LOAD_SECCOMP_FAILED);
        }
        if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(writev), 1, SCMP_A0(SCMP_CMP_LE, 2)) != 0) {
            LOG_FATAL(log_fp, "load dup2 rule failed");
            ERROR(log_fp, LOAD_SECCOMP_FAILED);
        }
        if (seccomp_load(ctx) != 0) {
            LOG_FATAL(log_fp, "seccomp load failed");
            ERROR(log_fp, LOAD_SECCOMP_FAILED);
        }
        seccomp_release(ctx);
    }
#endif
    execve(config->path, config->args, config->env);
    LOG_FATAL(log_fp, "execve failed, errno: %d", errno);
    ERROR(log_fp, EXCEVE_FAILED);
    return 1;
}


void run(struct config *config, struct result *result) {
    int status;
    struct rusage resource_usage;
    struct timeval start, end;
    
    int signal, pid;
    FILE *log_fp = NULL;
    char *stack = NULL;
    struct clone_args clone_args;
    
    log_fp = log_open(config->log_path);
    if(log_fp == NULL){
        result->flag = SYSTEM_ERROR;
        return;
    }

    gettimeofday(&start, NULL);

    if(config->max_memory < 1 && config->max_memory != MEMORY_UNLIMITED) {
        LOG_FATAL(log_fp, "max_memory must > 1 or unlimited");
        result->flag = SYSTEM_ERROR;
        log_close(log_fp);
        return;
    }
    if(config->max_cpu_time < 1 && config->max_cpu_time != CPU_TIME_UNLIMITED) {
        LOG_FATAL(log_fp, "max_cpu_time must > 1 or unlimited");
        result->flag = SYSTEM_ERROR;
        log_close(log_fp);
        return;
    }
    if((stack = malloc(STACK_SIZE)) == NULL) {
        LOG_FATAL(log_fp, "malloc stack failed");
        result->flag = SYSTEM_ERROR;
        log_close(log_fp);
        return; 
    }

    clone_args.config = config;
    clone_args.log_fp = log_fp;
    pid = clone(child_process, stack + STACK_SIZE, SIGCHLD, (void *)(&clone_args));

    if (pid < 0) {
        LOG_FATAL(log_fp, "fork failed, errno: %d", errno);
        result->flag = SYSTEM_ERROR;
        log_close(log_fp);
        return;
    }
    else {
        // parent process

        // on success, returns the process ID of the child whose state has changed;
        // On error, -1 is returned.
        if (wait4(pid, &status, 0, &resource_usage) == -1) {
            LOG_FATAL(log_fp, "wait4 failed");
            result->flag = SYSTEM_ERROR;
            log_close(log_fp);
            return;
        }
        LOG_DEBUG(log_fp, "exit status: %d", WEXITSTATUS(status));
        result->exit_status = WEXITSTATUS(status);
        result->cpu_time = (int) (resource_usage.ru_utime.tv_sec * 1000 +
                                  resource_usage.ru_utime.tv_usec / 1000 +
                                  resource_usage.ru_stime.tv_sec * 1000 +
                                  resource_usage.ru_stime.tv_usec / 1000);
         // avoid 0 ms
        if(result->cpu_time == 0) {
            result->cpu_time = 1;
        }

        // osx: ru_maxrss the maximum resident set size utilized (in bytes).
        // linux: ru_maxrss (since Linux 2.6.32)This  is  the  maximum  resident set size used (in kilobytes).
        // For RUSAGE_CHILDREN, this is the resident set size of the largest child,
        // not the maximum resident set size of the processtree.
        result->memory = resource_usage.ru_maxrss * 1024;

        result->signal = 0;
        result->flag = SUCCESS;

        if (WIFSIGNALED(status) != 0) {
            signal = WTERMSIG(status);
            LOG_DEBUG(log_fp, "signal: %d", signal);
            result->signal = signal;
            if (signal == SIGALRM) {
                result->flag = REAL_TIME_LIMIT_EXCEEDED;
            }
            else if (signal == SIGVTALRM) {
                result->flag = CPU_TIME_LIMIT_EXCEEDED;
            }
            else if (signal == SIGSEGV) {
                if (config->max_memory != MEMORY_UNLIMITED && result->memory > config->max_memory) {
                    result->flag = MEMORY_LIMIT_EXCEEDED;
                }
                else {
                    result->flag = RUNTIME_ERROR;
                }
            }
            // Child process error
            else if (signal == SIGUSR1){
                result->flag = SYSTEM_ERROR;
            }
            else {
                result->flag = RUNTIME_ERROR;
            }
        }
        else {
            if (config->max_memory != MEMORY_UNLIMITED && result->memory > config->max_memory) {
                result->flag = MEMORY_LIMIT_EXCEEDED;
            }
            if (WEXITSTATUS(status) != 0) {
                result->flag = RUNTIME_ERROR;
            }
        }
        gettimeofday(&end, NULL);
        result->real_time = (int) (end.tv_sec * 1000 + end.tv_usec / 1000 - start.tv_sec * 1000 - start.tv_usec / 1000);
        log_close(log_fp);
    }
}