utils.c

#include <dirent.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "config.h"
#include "utils.h"

pid_t GetPid(const char* process_name) {
  if (process_name == NULL) {
    return -1;
  }
  DIR* dir = opendir("/proc");
  if (dir == NULL) {
    return -1;
  }
  struct dirent* entry;
  while((entry = readdir(dir)) != NULL) {
    size_t pid = atoi(entry->d_name);
    if (pid != 0) {
      char file_name[30];
      snprintf(file_name, 30, "/proc/%zu/cmdline", pid);
      FILE *fp = fopen(file_name, "r");
      char temp_name[50];
      if (fp != NULL) {
        fgets(temp_name, 50, fp);
        fclose(fp);
        if (strcmp(process_name, temp_name) == 0) {
          return pid;
        }
      }
    }
  }
  return -1;
}

bool IsSelinuxEnabled() {
  FILE* fp = fopen("/proc/filesystems", "r");
  char* line = (char*) calloc(50, sizeof(char));
  bool result = false;
  while(fgets(line, 50, fp)) {
    if (strstr(line, "selinuxfs")) {
      result = true;
    }
  }
  if (line) {
    free(line);
  }
  fclose(fp);
  return result;
}

void DisableSelinux() {
  FILE* fp = fopen("/proc/mounts", "r");
  char* line = (char*) calloc(1024, sizeof(char));
  while(fgets(line, 1024, fp)) {
    if (strstr(line, "selinuxfs")) {
      strtok(line, " ");
      char* selinux_dir = strtok(NULL, " ");
      char* selinux_path = strcat(selinux_dir, "/enforce");
      FILE* fp_selinux = fopen(selinux_path, "w");
      char* buf = "0"; // set selinux to permissive
      fwrite(buf, strlen(buf), 1, fp_selinux);
      fclose(fp_selinux);
      break;
    }
  }
  fclose(fp);
  if (line) {
    free(line);
  }
}

long GetModuleBaseAddr(pid_t pid, const char* module_name) {
  long base_addr_long = 0;
  if (pid == -1) {
    return 0;
  }
  char* file_name = (char*) calloc(50, sizeof(char));
  snprintf(file_name, 50, "/proc/%d/maps", pid);
  FILE* fp = fopen(file_name, "r");
  free(file_name);
  char line[512];
  if (fp != NULL) {
    while(fgets(line, 512, fp) != NULL) {
      if (strstr(line, module_name) != NULL) {
        char* base_addr = strtok(line, "-");
        base_addr_long = strtoul(base_addr, NULL, 16);
        break;
      }
    }
    fclose(fp);
  }
  return base_addr_long;
}

long GetRemoteFuctionAddr(pid_t remote_pid, const char* module_name, long local_function_addr) {
  pid_t pid = getpid();
  long local_base_addr = GetModuleBaseAddr(pid, module_name);
  long remote_base_addr = GetModuleBaseAddr(remote_pid, module_name);
  if (local_base_addr == 0 || remote_base_addr == 0) {
    return 0;
  }
  return local_function_addr + (remote_base_addr - local_base_addr);
}