/*

 * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * A simple launcher to launch a program as if it was launched by inetd.

 */

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <unistd.h>

#include <dirent.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <ctype.h>

#include "jni.h"

/*

 * Throws the exception of the given class name and detail message

 */

static void ThrowException(JNIEnv *env, const char *name, const char *msg) {

    jclass cls = (*env)->FindClass(env, name);

    if (cls != NULL) {

        (*env)->ThrowNew(env, cls, msg);

    }

}

/*

 * Convert a jstring to an ISO 8859_1 encoded C string

 */

static char* getString8859_1Chars(JNIEnv *env, jstring jstr) {

    int i;

    char *result;

    jint len = (*env)->GetStringLength(env, jstr);

    const jchar *str = (*env)->GetStringCritical(env, jstr, 0);

    if (str == 0) {

        return NULL;

    }

    result = (char*)malloc(len+1);

    if (result == 0) {

        (*env)->ReleaseStringCritical(env, jstr, str);

        ThrowException(env, "java/lang/OutOfMemoryError", NULL);

        return NULL;

    }

    for (i=0; i<len; i++) {

        jchar unicode = str[i];

        if (unicode <= 0x00ff)

            result[i] = unicode;

        else

            result[i] = '?';

    }

    result[len] = 0;

    (*env)->ReleaseStringCritical(env, jstr, str);

    return result;

}

/*

 * Class:     Launcher

 * Method:    launch0

 * Signature: ([Ljava/lang/String;I)V

 */

JNIEXPORT void JNICALL Java_Launcher_launch0

  (JNIEnv *env, jclass cls, jobjectArray cmdarray, jint serviceFd)

{

    pid_t pid;

    DIR* dp;

    struct dirent* dirp;

    int thisFd;

    char** cmdv;

    int i, cmdlen;

    /*

     * Argument 0 of the command array is the program name.

     * Here we just extract the program name and any arguments into

     * a command array suitable for use with execvp.

     */

    cmdlen = (*env)->GetArrayLength(env, cmdarray);

    if (cmdlen == 0) {

        ThrowException(env, "java/lang/IllegalArgumentException",

            "command array must at least include the program name");

        return;

    }

    cmdv = (char **)malloc((cmdlen + 1) * sizeof(char *));

    if (cmdv == NULL) {

        ThrowException(env, "java/lang/OutOfMemoryError", NULL);

        return;

    }

    for (i=0; i<cmdlen; i++) {

        jstring str = (*env)->GetObjectArrayElement(env, cmdarray, i);

        cmdv[i] = (char *) getString8859_1Chars(env, str);

        if (cmdv[i] == NULL) {

            return;

        }

    }

    /*

     * Command array must have NULL as the last entry

     */

    cmdv[cmdlen] = NULL;

    /*

     * Launch the program. As this isn't a complete inetd or Runtime.exec

     * implementation we don't have a reaper to pick up child exit status.

     */

#ifdef __solaris__

    pid = fork1();

#else

    pid = fork();

#endif

    if (pid != 0) {

        if (pid < 0) {

            ThrowException(env, "java/io/IOException", "fork failed");

        }

        return;

    }

    /*

     * We need to close all file descriptors except for serviceFd. To

     * get the list of open file descriptos we read through /proc/self/fd

     * but to open this requires a file descriptor. We could use a specific

     * file descriptor and fdopendir but Linux doesn't seem to support

     * fdopendir. Instead we use opendir and make an assumption on the

     * file descriptor that is used (by opening & closing a file).

     */

    thisFd = open("/dev/null", O_RDONLY);

    if (thisFd < 0) {

        _exit(-1);

    }

    close(thisFd);

    if ((dp = opendir("/proc/self/fd")) == NULL) {

        _exit(-1);

    }

    while ((dirp = readdir(dp)) != NULL) {

        if (isdigit(dirp->d_name[0])) {

            int fd = strtol(dirp->d_name, NULL, 10);

            if (fd != serviceFd && fd != thisFd) {

                close(fd);

            }

        }

    }

    closedir(dp);

    /*

     * At this point all file descriptors are closed except for

     * serviceFd. We not dup 0,1,2 to this file descriptor and

     * close serviceFd. This should leave us with only 0,1,2

     * open and all connected to the same socket.

     */

    dup2(serviceFd, STDIN_FILENO);

    dup2(serviceFd, STDOUT_FILENO);

    dup2(serviceFd, STDERR_FILENO);

    close(serviceFd);

    execvp(cmdv[0], cmdv);

    _exit(-1);

}