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  • 提到的案例正在使用内核（5.4.0-91-generic）在 ubuntu 上工作，但它不适用于内核（4.19.71）
  • 在更改用户 ID 和组 ID 后，我正在使用 launcher.cpp 启动应用程序，
  • 但在那之后 test_app.cpp 无法使用 syslog 进行记录。（没有日志记录）
  • 验证日志日志的命令：journalctl -f
  • 我能在日志中看到的所有 launcher.cpp 日志只有启动 test_app.cpp 日志没有出现。

启动测试应用程序的命令：

  • $sudo ./launcher test_server ./test_app

下面是启动器和测试应用程序代码：

启动器.cpp：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <grp.h>
#include<syslog.h>


typedef struct AppID{
    unsigned int userID;
    unsigned int groupID;
    char appName[100];
    unsigned int appGroupSize;
    gid_t groups[64];
}AppID;

const struct AppID appList[]={
    {3070 ,3070  ,"test_server"      ,4 ,{ 100, 110, 3010, 3020 }},
};

static inline void settingAppID(const char* nameExec){
    gid_t oldgid = getegid();
    uid_t olduid = geteuid();
    gid_t newgid = 0;
    uid_t newuid = 0;

    for(unsigned int i=0;i<sizeof(appList)/sizeof(AppID);++i)
    {
        if(strlen(nameExec) < strlen(appList[i].appName))
            continue;
        if(memcmp(nameExec , appList[i].appName , strlen(appList[i].appName))==0){
            if(appList[i].appGroupSize > 0){
                setgroups( appList[i].appGroupSize, appList[i].groups );
            }

            newuid = appList[i].userID;
            newgid = appList[i].groupID;

            if (newgid != oldgid && setregid(newgid, newgid) == -1)
            {
                exit(1);
            }
            if (newuid != olduid && setreuid(newuid, newuid) == -1)
            {
                exit(1);
            }

            // verify that the changes are successful
            if (newgid != oldgid && (setegid(oldgid) != -1 || getegid() != newgid))
            {
                exit(1);
            }
            if (newuid != olduid && (seteuid(olduid) != -1 || geteuid() != newuid))
            {
                exit(1);
            }
            break;
        }
    }
    return;
}

int main(int argc, char* argv[]){
    if(argc < 3){
        exit(1);
    }

    syslog (LOG_NOTICE, "launcher : Program started by User ");

    settingAppID(argv[1]);

    syslog (LOG_NOTICE, "launcher : Program started by User ");

    closelog();

    execvp (argv[2],&argv[2]);
    return 0;
}

test_app.cpp：

#include<syslog.h>
int main()
{
    openlog("launcher", LOG_PID|LOG_CONS, LOG_USER);
    syslog (LOG_NOTICE, "test : Program started by User ");
    syslog (LOG_INFO, "test : A tree falls in a forest");
    syslog (LOG_NOTICE, "test : Program started by User ");
    syslog (LOG_INFO, "test : A tree falls in a forest");
    closelog();
    return 0;
}
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