Hydra - spawns a very annoying set of processes that can't be defeated without specialized tools

hydra.c

/*
 * Max DeLiso <maxdeliso@gmail.com>
 * Hydra.c
 */

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <fcntl.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <sys/prctl.h>

typedef unsigned char bool;
const bool false = 0;
const bool true = 1;

union semun {
   int val;
   struct semid_ds *buf;
   ushort *array;
};

int handleCmdLine(int argc, char **argv);
void installSignalHandlers();
void *setupShmem(int childCount);
int setupSem();
void autoReap(int sigNum);
void childProcedure(int n, int count, void *shmAddr, int semId);
bool semaphoreP(int semId);
void semaphoreV(int semId);

int main(int argc, char **argv)
{
   int i;
   int childCount;
   int semId;
   int returnCode;
   void *shmAddr;

   /* parse command line */
   childCount = handleCmdLine(argc, argv);

   /* setup signal handlers - this wil persist after fork */
   installSignalHandlers();

   /* acquire shared memory - this will be shared by all of the children */
   shmAddr = setupShmem(childCount);
   semId = setupSem();

   /* main forking loop */
   for (i = 0; i < childCount; i++) {
      switch (returnCode = fork()) {
      case 0:
         childProcedure(i, childCount, shmAddr, semId);
         exit(EXIT_SUCCESS);
         break;

      case -1:
         perror("fork()");
         exit(EXIT_FAILURE);
         break;

      default:
         ((int *)shmAddr)[i] = returnCode;
         break;
      }
   }

   /*detach shmem */
   if (shmdt(shmAddr) == -1) {
      perror("shmdt()");
      exit(1);
   }

   return (EXIT_SUCCESS);
}

int handleCmdLine(int argc, char **argv)
{
   int opt;
   int childCount = -1;

   while ((opt = getopt(argc, argv, "hvn:")) != -1) {
      switch (opt) {
      default:
      case 'h':
         printf("%s [-n count] [-h] [-v]\n", argv[0]);
         exit(0);
      case 'v':
         printf("%s: version 1.0\n", argv[0]);
         exit(0);
      case 'n':
         childCount = atoi(optarg);
         break;
      }
   }

   if (childCount == -1) {
      fprintf(stderr,
              "Fatal: you must specify a number of processes with -n\n");
      exit(1);
   }

   if (childCount <= 0) {
      fprintf(stderr, "Fatal: n out of range\n");
      exit(1);
   }

   return childCount;
}

void installSignalHandlers()
{
   struct sigaction childAction;
   const static int sigIgnList[] = {
      SIGHUP,
      SIGINT,
      SIGQUIT,
      SIGPIPE,
      SIGALRM,
      SIGTERM,
      SIGUSR1,
      SIGUSR2,
      SIGTSTP,
      SIGTTIN,
      SIGTTOU,
      SIGTRAP,
      SIGILL
   };

   int sigIgnListCount = sizeof(sigIgnList) / sizeof(sigIgnList[0]);
   int i;

   /* install autoreap signal handler */
   childAction.sa_handler = autoReap;
   sigemptyset(&childAction.sa_mask);
   childAction.sa_flags = 0;

   if (sigaction(SIGCHLD, &childAction, NULL) == -1) {
      perror("child: sigaction()");
      exit(1);
   }

   /* ignore signals that can be ignored */
   for (i = 0; i < sigIgnListCount; i++) {
      if (signal(sigIgnList[i], SIG_IGN)) {
         perror("child: signal()");
         exit(1);
      }
   }
}

void *setupShmem(int childCount)
{
   int shmId;
   int i;
   void *shmAddr;

   /* allocate shared memory */
   shmId = shmget(IPC_PRIVATE, childCount * sizeof(int), S_IRWXU);
   if (shmId == -1) {
      perror("shmget()");
      exit(1);
   }
   /* attach to current process */
   shmAddr = shmat(shmId, NULL, O_RDWR);
   if (shmAddr == (const void *)-1) {
      perror("shmat()");
      exit(1);
   }
   /* initialize to -1 (invalid) */
   for (i = 0; i < childCount; i++) {
      ((int *)shmAddr)[i] = -1;
   }

   return shmAddr;
}

int setupSem()
{
   int semId;
   union semun semArg;

   /* create semaphore */
   semId = semget(IPC_PRIVATE, 1, S_IRWXU);
   if (semId == -1) {
      perror("semget()");
      exit(1);
   }
   /* initialize to 1 */
   semArg.val = 1;
   if (semctl(semId, 0, SETVAL, semArg) < 0) {
      perror("semctl()");
      exit(1);
   }

   return semId;
}

void autoReap(int sigNum)
{
   int status;
   int pid;

   pid = wait(&status);
}

void childProcedure(int n, int count, void *shmAddr, int semId)
{
   int i;
   int ret;
   char nameBuf[32];
   char numBuf[32];

   /* generate unqiue process name */
   strcpy(nameBuf, "hydra-");
   sprintf(numBuf, "%i", n);
   strcat(nameBuf, numBuf);

   /* set it */
   if (prctl(PR_SET_NAME, nameBuf)) {
      perror("prctl(): could not set process name");
      exit(1);
   }

   /* iterate infinitely through the shared memory, pinging each peer */
   for (;;)
      /* for each of the children */
      for (i = 0; i < count; i++) {
         /* if the current child in shmem is not this one */
         if (((int *)shmAddr)[i] != -1 && getpid() != ((int *)shmAddr)[i]) {
            /* send a signal to see if it is still living */
            ret = kill((pid_t) ((int *)shmAddr)[i], 0);

            /* if it isn't... */
            if (ret == -1 && errno == ESRCH) {
               /* acquire the spawn mutex */
               if (semaphoreP(semId)) {
                  /* fork a new process */
                  switch (ret = fork()) {
                  case -1:
                     perror("child: fork()");
                     exit(1);
                  case 0:
                     /* and call this function with it */
                     ((int *)shmAddr)[i] = -1;
                     childProcedure(i, count, shmAddr, semId);
                  default:
                     /* while storing it's pid in the shared memory */
                     ((int *)shmAddr)[i] = ret;
                     break;
                  }
                  /* and release the spawn mutex */
                  semaphoreV(semId);
               }
            }
         }
      }
}

bool semaphoreP(int semId)
{
   struct sembuf semOps[1];
   int retCode;
   bool result;

   semOps[0].sem_num = 0;
   semOps[0].sem_op = -1;
   semOps[0].sem_flg = SEM_UNDO | IPC_NOWAIT;

   retCode = semop(semId, semOps, 1);

   if (retCode == 0) {
      result = true;
   } else if (retCode == -1 && errno == EAGAIN) {
      result = false;
   } else {
      perror("child: semop() P");
      exit(1);
   }

   return result;
}

void semaphoreV(int semId)
{
   struct sembuf semOps[1];
   int retCode;

   semOps[0].sem_num = 0;
   semOps[0].sem_op = 1;
   semOps[0].sem_flg = SEM_UNDO;

   retCode = semop(semId, semOps, 1);

   if (retCode == -1) {
      perror("child: semop() V");
   }
}

makefile

# Max DeLiso <maxdeliso@gmail.com>
# Hydra makefile

hydra:
	gcc -O2 hydra.c -o hydra

clean:
	rm -f hydra