使用execvp(）;执行进程时加载用户环境;

Load user environment when executing process with execvp();

本文关键字：加载 用户 环境 进程 执行 execvp 使用      更新时间：2023-10-16

我有一个正在运行的守护进程，它可能会在连接中断时生成一个进程。这是使用execvp()和fork()来完成的。

问题是进程不应该以root身份运行，并且进程依赖于正确的用户环境。所以我正在寻找一种加载用户环境的方法。

当前，通过设置gid和uid，进程以另一个用户的身份执行。我已经尝试过使用作为命令su -l user -c command，但由于某些原因，该命令不起作用。

有人知道我如何加载用户环境（尤其是$HOME变量）吗？

提前谢谢。

您可以这样做：

#include <cstring>
#include <iostream>
#include <vector>
#include <stdio.h>
#include <pwd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
// Version 0 or 1
#ifndef VERSION
#define VERSION 1
#endif
// Please compile twise TEST_PROCESS = 0 and TEST_PROCESS = 1
#ifndef TEST_PROCESS
#define TEST_PROCESS 0
#endif
// User for the process started.
#ifndef USER
#error Please define a user (just a name, no string).
#endif
#define MAKE_STR(x) DO_MAKE_STR(x)
#define DO_MAKE_STR(x) #x
#define USER_NAME MAKE_STR(USER)
class UserEnvironment
{
    public:
    typedef std::vector<char*> Values;
    UserEnvironment(const char* user) {
        auto cmd = std::string("su - ") + user + " -c '. ~/.profile; env'";
        FILE* fp = popen(cmd.c_str(), "r");
        if(fp == 0)  perror(0);
        else {
            char* line = 0;
            size_t len = 0;
            ssize_t n = 0;
            while(1 < (n = getline(&line, &len, fp))) {
                line[n - 1] = 0;
                m_values.push_back(line);
                line = 0;
            }
            pclose(fp);
        }
        m_values.push_back(0);
    };
    ~UserEnvironment() {
        m_values.pop_back();
        for(char* p: m_values) free(p);
    }
    const Values& values() const { return m_values; }
    Values& values() { return m_values; }
    operator const Values& () const { return m_values; }
    operator Values& () { return m_values; }
    char* const * data() const { return m_values.data(); }
    char** data() { return m_values.data(); }
    private:
    Values m_values;
};
inline const char* get_home() {
    const char* home = getenv("HOME");
    if(home == 0) home = "[Missing]";
    return home;
}
#if ! TEST_PROCESS
// Debug/Test
int main() {
    const char* user = USER_NAME;
    int pid = fork();
    if(pid < 0) return 1;
    else if(pid) {
        const char* home = get_home();
        std::cout << "Running Demon: Home = " << home
            << ", User ID = " << getuid() << std::endl;
        wait(NULL);
    }
    else {
        struct passwd* pw = getpwnam(user);
        if( ! pw) {
            std::cout << "Invalid User [" << user << ']'<< std::endl;
        }
        else {
            char* process = strdup("Debug/TestProcess");
            char *const argv[] = {
                process,
                NULL
            };
        #if VERSION == 0
            // Oberwrite environment variables.
            // You might call clearenv();
            if(setgid(pw->pw_gid) == 0 && setuid(pw->pw_uid) == 0) {
                setenv("HOME", pw->pw_dir, 1);
                execvp(process, argv);
            }
        #else
            // Use the user environt.
            UserEnvironment environment(user);
            if(setgid(pw->pw_gid) == 0 && setuid(pw->pw_uid) == 0) {
                execvpe(process, argv, environment.data());
            }
        #endif
            free(process);
        }
    }
    const char* home = get_home();
    std::cout << "Exit: Home = " << home << ", User ID = " << getuid() << std::endl;
    return 0;
}
#else
// Debug/TestProcess
int main() {
    const char* home = get_home();
    std::cout
         << "Running Process: Home = " << home
         << ", User ID = " << getuid()
         << std::endl;
    system("env");
    exit(0);
}
#endif

注意：请编译两次以生成Debug/Test和Debug/TestProcess

结果：

Running Demon: Home = /root, User ID = 0
Running Process: Home = /home/..., User ID = 1000
... // The Environment
Exit: Home = /root, User ID = 0

sudo有一个附加选项-H，用于设置$HOME变量。所以你可以试试

sudo -H -u user command

而不是su命令行。

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