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serverC

Opublikowano: 10 wrzesień 2020 | Super User |

| Odsłony: 83

/*
* tiny.c - a minimal HTTP server that serves static and
*          dynamic content with the GET method. Neither
*          robust, secure, nor modular. Use for instructional
*          purposes only.
*          Dave O'Hallaron, Carnegie Mellon
*
*          usage: tiny <port>
*/

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define BUFSIZE 1024
#define MAXERRS 16

extern char **environ; /* the environment */

/*
* error - wrapper for perror used for bad syscalls
*/
void error(char *msg) {
perror(msg);
exit(1);
}

/*
* cerror - returns an error message to the client
*/
void cerror(FILE *stream, char *cause, char *errno,
        char *shortmsg, char *longmsg) {
fprintf(stream, "HTTP/1.1 %s %s\n", errno, shortmsg);
fprintf(stream, "Content-type: text/html\n");
fprintf(stream, "\n");
fprintf(stream, "<html><title>Tiny Error</title>");
fprintf(stream, "<body bgcolor=""ffffff"">\n");
fprintf(stream, "%s: %s\n", errno, shortmsg);
fprintf(stream, "<p>%s: %s\n", longmsg, cause);
fprintf(stream, "<hr><em>The Tiny Web server</em>\n");
}

int main(int argc, char **argv) {

/* variables for connection management */
int parentfd;          /* parent socket */
int childfd;           /* child socket */
int portno;            /* port to listen on */
int clientlen;         /* byte size of client's address */
struct hostent *hostp; /* client host info */
char *hostaddrp;       /* dotted decimal host addr string */
int optval;            /* flag value for setsockopt */
struct sockaddr_in serveraddr; /* server's addr */
struct sockaddr_in clientaddr; /* client addr */

/* variables for connection I/O */
FILE *stream;          /* stream version of childfd */
char buf[BUFSIZE];     /* message buffer */
char method[BUFSIZE]; /* request method */
char uri[BUFSIZE];     /* request uri */
char version[BUFSIZE]; /* request method */
char filename[BUFSIZE];/* path derived from uri */
char filetype[BUFSIZE];/* path derived from uri */
char cgiargs[BUFSIZE]; /* cgi argument list */
char *p;               /* temporary pointer */
int is_static;         /* static request? */
struct stat sbuf;      /* file status */
int fd;                /* static content filedes */
int pid;               /* process id from fork */
int wait_status;       /* status from wait */

/* check command line args */
if (argc != 2) {
    fprintf(stderr, "usage: %s <port>\n", argv[0]);
    exit(1);
}
portno = atoi(argv[1]);

/* open socket descriptor */
parentfd = socket(AF_INET, SOCK_STREAM, 0);
if (parentfd < 0)
    error("ERROR opening socket");

/* allows us to restart server immediately */
optval = 1;
setsockopt(parentfd, SOL_SOCKET, SO_REUSEADDR,
         (const void *)&optval , sizeof(int));

/* bind port to socket */
bzero((char *) &serveraddr, sizeof(serveraddr));
serveraddr.sin_family = AF_INET;
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
serveraddr.sin_port = htons((unsigned short)portno);
if (bind(parentfd, (struct sockaddr *) &serveraddr,
       sizeof(serveraddr)) < 0)
    error("ERROR on binding");

/* get us ready to accept connection requests */
if (listen(parentfd, 5) < 0) /* allow 5 requests to queue up */
    error("ERROR on listen");

/*
   * main loop: wait for a connection request, parse HTTP,
   * serve requested content, close connection.
   */
clientlen = sizeof(clientaddr);
while (1) {

    /* wait for a connection request */
    childfd = accept(parentfd, (struct sockaddr *) &clientaddr, &clientlen);
    if (childfd < 0)
      error("ERROR on accept");

    /* determine who sent the message */
    hostp = gethostbyaddr((const char *)&clientaddr.sin_addr.s_addr,
            sizeof(clientaddr.sin_addr.s_addr), AF_INET);
    if (hostp == NULL)
      error("ERROR on gethostbyaddr");
    hostaddrp = inet_ntoa(clientaddr.sin_addr);
    if (hostaddrp == NULL)
      error("ERROR on inet_ntoa\n");

    /* open the child socket descriptor as a stream */
    if ((stream = fdopen(childfd, "r+")) == NULL)
      error("ERROR on fdopen");

    /* get the HTTP request line */
    fgets(buf, BUFSIZE, stream);
    printf("%s", buf);
    sscanf(buf, "%s %s %s\n", method, uri, version);

    /* tiny only supports the GET method */
    if (strcasecmp(method, "GET")) {
      cerror(stream, method, "501", "Not Implemented",
         "Tiny does not implement this method");
      fclose(stream);
      close(childfd);
      continue;
    }

    /* read (and ignore) the HTTP headers */
    fgets(buf, BUFSIZE, stream);
    printf("%s", buf);
    while(strcmp(buf, "\r\n")) {
      fgets(buf, BUFSIZE, stream);
      printf("%s", buf);
    }

    /* parse the uri [crufty] */
    if (!strstr(uri, "cgi-bin")) { /* static content */
      is_static = 1;
      strcpy(cgiargs, "");
      strcpy(filename, ".");
      strcat(filename, uri);
      if (uri[strlen(uri)-1] == '/')
    strcat(filename, "index.html");
    }
    else { /* dynamic content */
      is_static = 0;
      p = index(uri, '?');
      if (p) {
    strcpy(cgiargs, p+1);
    *p = '\0';
      }
      else {
    strcpy(cgiargs, "");
      }
      strcpy(filename, ".");
      strcat(filename, uri);
    }

    /* make sure the file exists */
    if (stat(filename, &sbuf) < 0) {
      cerror(stream, filename, "404", "Not found",
         "Tiny couldn't find this file");
      fclose(stream);
      close(childfd);
      continue;
    }

    /* serve static content */
    if (is_static) {
      if (strstr(filename, ".html"))
    strcpy(filetype, "text/html");
      else if (strstr(filename, ".gif"))
    strcpy(filetype, "image/gif");
      else if (strstr(filename, ".jpg"))
    strcpy(filetype, "image/jpg");
      else
    strcpy(filetype, "text/plain");

      /* print response header */
      fprintf(stream, "HTTP/1.1 200 OK\n");
      fprintf(stream, "Server: Tiny Web Server\n");
      fprintf(stream, "Content-length: %d\n", (int)sbuf.st_size);
      fprintf(stream, "Content-type: %s\n", filetype);
      fprintf(stream, "\r\n");
      fflush(stream);

      /* Use mmap to return arbitrary-sized response body */
      fd = open(filename, O_RDONLY);
      p = mmap(0, sbuf.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
      fwrite(p, 1, sbuf.st_size, stream);
      munmap(p, sbuf.st_size);
    }

    /* serve dynamic content */
    else {
      /* make sure file is a regular executable file */
      if (!(S_IFREG & sbuf.st_mode) || !(S_IXUSR & sbuf.st_mode)) {
    cerror(stream, filename, "403", "Forbidden",
           "You are not allow to access this item");
    fclose(stream);
    close(childfd);
    continue;
      }

      /* a real server would set other CGI environ vars as well*/
      setenv("QUERY_STRING", cgiargs, 1);

      /* print first part of response header */
      sprintf(buf, "HTTP/1.1 200 OK\n");
      write(childfd, buf, strlen(buf));
      sprintf(buf, "Server: Tiny Web Server\n");
      write(childfd, buf, strlen(buf));

      /* create and run the child CGI process so that all child
         output to stdout and stderr goes back to the client via the
         childfd socket descriptor */
      pid = fork();
      if (pid < 0) {
    perror("ERROR in fork");
    exit(1);
      }
      else if (pid > 0) { /* parent process */
    wait(&wait_status);
      }
      else { /* child process*/
    close(0); /* close stdin */
    dup2(childfd, 1); /* map socket to stdout */
    dup2(childfd, 2); /* map socket to stderr */
    if (execve(filename, NULL, environ) < 0) {
    perror("ERROR in execve");
    }
      }
    }

    /* clean up */
    fclose(stream);
    close(childfd);

}
}

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