rdo/sessions.h

#pragma once

#include <limits.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <time.h>

int getpstartts(int pid, unsigned long long* startts) {
    char path[255], fc[1024];
    char* ptr = fc;

    snprintf(path, sizeof(path), "/proc/%d/stat", pid);
    int fd = open(path, O_RDONLY);

    if (fd < 0)
        err(1, "Could not open %s", path);

    int bytes_read = read(fd, fc, sizeof(fc));

    close(fd);

    if (bytes_read < 0)
        err(1, "Could not read %s", path);

    fc[bytes_read] = '\0';

    if (memchr(ptr, '\0', bytes_read) != NULL)
        return -1;

    ptr = strrchr(fc, ')');

    char* token = strtok(ptr, " ");

    for (int i = 0; i<20 && token; i++)
        token = strtok(NULL, " ");

    if (!token)
        return -1;

    unsigned long long temp_ts = strtoull(token, NULL, 10);
    if (temp_ts == 0 || temp_ts == ULLONG_MAX)
        return -1;

    *startts = temp_ts;
    return 0;
}

int ensuredir() {
    struct stat st;
    int fd = open("/var/run/rdo", O_RDONLY, O_DIRECTORY | O_NOFOLLOW);

    if (fd < 0) {
        if (errno == ENOENT) {
            if (mkdir("/var/run/rdo", 0700) < 0)
                err(1, "Could not create /var/run/rdo");

            fd = open("/var/run/rdo", O_RDONLY, O_DIRECTORY | O_NOFOLLOW);
            if (fd < 0)
                err(1, "Could not open /var/run/rdo");
        }
        else
            err(1, "Could not open /var/run/rdo");
    }

    if (fstat(fd, &st) < 0) {
        close(fd);
        err(1, "Could not fstat /var/run/rdo");
    }

    close(fd);

    if (st.st_uid != 0 || st.st_mode != (0700 | S_IFDIR))
        return -1;

    return 0;
}

void setsession(int pid, int ts_ttl, int ruid) {
    if (ts_ttl <= 0)
        return;

#ifdef TIOCSETVERAUTH
    (void)pid;
    (void)ruid;

    int ttyfd = open("/dev/tty", O_RDWR);
    ioctl(ttyfd, TIOCSETVERAUTH, &ts_ttl);
    close(ttyfd);

#else
    unsigned long long startts;
    char path[1024], ts_str[32];


    if (ensuredir() < 0 || getpstartts(pid, &startts) < 0)
        return;

    snprintf(path, sizeof(path), "/var/run/rdo/%d-%d-%llu", ruid, pid, startts);

    int fd = open(path, O_CREAT | O_EXCL | O_WRONLY, 0700);
    if (fd < 0) {
        if (errno == EEXIST)
            return;
        err(1, "Could not open %s", path);
    }

    snprintf(ts_str, sizeof(ts_str), "%llu", (unsigned long long)time(NULL));

    if (write(fd, ts_str, strlen(ts_str)) < 0) {
        close(fd);
        err(1, "Could not write to %s", path);
    }

    close(fd);
#endif

    return;
}

int getsession(int pid, int ts_ttl, int ruid) {
    if (ts_ttl <= 0)
        return -1;

#ifdef TIOCCHKVERAUTH
    (void)pid;
    (void)ruid;

    int ttyfd = open("/dev/tty", O_RDWR);
    int ret = ioctl(ttyfd, TIOCCHKVERAUTH);
    close(ttyfd);
    return ret;

#else
    unsigned long long startts, current;
    char path[1024], ts_str[32];

    if (ensuredir() < 0 || getpstartts(pid, &startts) < 0)
        return -1;

    snprintf(path, sizeof(path), "/var/run/rdo/%d-%d-%llu", ruid, pid, startts);

    int fd = open(path, O_RDONLY);
    if (fd < 0) {
        if (errno == ENOENT)
            return -1;
        err(1, "Could not open %s", path);
    }

    int bytes_read = read(fd, ts_str, sizeof(ts_str));

    close(fd);

    if (bytes_read < 0)
        err(1, "Could not read %s", path);
    ts_str[bytes_read] = '\0';

    startts = strtoull(ts_str, NULL, 10);
    current = time(NULL);

    if (current - startts > (unsigned int)ts_ttl) {
        unlink(path);
        return -1;
    }

    return 0;
#endif
}