/* J. David's webserver */
/* This is a simple webserver.
* Created November 1999 by J. David Blackstone.
* CSE 4344 (Network concepts), Prof. Zeigler
* University of Texas at Arlington
*/
/* This program compiles for Sparc Solaris 2.6.
* To compile for Linux:
*  1) Comment out the #include line.
*  2) Comment out the line that defines the variable newthread.
*  3) Comment out the two lines that run pthread_create().
*  4) Uncomment the line that runs accept_request().
*  5) Remove -lsocket from the Makefile.
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
//#include
#include
#include

#define ISspace(x) isspace((int)(x))

#define SERVER_STRING "Server: jdbhttpd/0.1.0rn"

void accept_request(int);
void bad_request(int);
void cat(int, FILE *);
void cannot_execute(int);
void error_die(const char *);
void execute_cgi(int, const char *, const char *, const char *);
int get_line(int, char *, int);
void headers(int, const char *);
void not_found(int);
void serve_file(int, const char *);
int startup(u_short *);
void unimplemented(int);

/**********************************************************************/
/* A request has caused a call to accept() on the server port to
* return.  Process the request appropriately.
* Parameters: the socket connected to the client */
/**********************************************************************/
void accept_request(int client)
{
char buf[1024];
int numchars;
char method[255];
char url[255];
char path[512];
size_t i, j;
struct stat st;
int cgi = 0;      /* becomes true if server decides this is a CGI
                    * program */
char *query_string = NULL;

numchars = get_line(client, buf, sizeof(buf));
i = 0; j = 0;
while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
{
  method = buf[j];
  i++; j++;
}
method = '';

if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
{
  unimplemented(client);
  return;
}

if (strcasecmp(method, "POST") == 0)
  cgi = 1;

i = 0;
while (ISspace(buf[j]) && (j < sizeof(buf)))
  j++;
while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
{
  url = buf[j];
  i++; j++;
}
url = '';

if (strcasecmp(method, "GET") == 0)
{
  query_string = url;
  while ((*query_string != '?') && (*query_string != ''))
   query_string++;
  if (*query_string == '?')
  {
   cgi = 1;
   *query_string = '';
   query_string++;
  }
}

sprintf(path, "htdocs%s", url);
if (path[strlen(path) - 1] == '/')
  strcat(path, "index.html");
if (stat(path, &st) == -1) {
  while ((numchars > 0) && strcmp("n", buf))  /* read & discard headers */
   numchars = get_line(client, buf, sizeof(buf));
  not_found(client);
}
else
{
  if ((st.st_mode & S_IFMT) == S_IFDIR)
   strcat(path, "/index.html");
  if ((st.st_mode & S_IXUSR) ||
      (st.st_mode & S_IXGRP) ||
      (st.st_mode & S_IXOTH)    )
   cgi = 1;
  if (!cgi)
   serve_file(client, path);
  else
   execute_cgi(client, path, method, query_string);
}

close(client);
}

/**********************************************************************/
/* Inform the client that a request it has made has a problem.
* Parameters: client socket */
/**********************************************************************/
void bad_request(int client)
{
char buf[1024];

sprintf(buf, "HTTP/1.0 400 BAD REQUESTrn");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "Content-type: text/htmlrn");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "rn");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "

Your browser sent a bad request, ");
send(client, buf, sizeof(buf), 0);
sprintf(buf, "such as a POST without a Content-Length.rn");
send(client, buf, sizeof(buf), 0);
}

/**********************************************************************/
/* Put the entire contents of a file out on a socket.  This function
* is named after the UNIX "cat" command, because it might have been
* easier just to do something like pipe, fork, and exec("cat").
* Parameters: the client socket descriptor
*             FILE pointer for the file to cat */
/**********************************************************************/
void cat(int client, FILE *resource)
{
char buf[1024];

fgets(buf, sizeof(buf), resource);
while (!feof(resource))
{
  send(client, buf, strlen(buf), 0);
  fgets(buf, sizeof(buf), resource);
}
}

/**********************************************************************/
/* Inform the client that a CGI script could not be executed.
* Parameter: the client socket descriptor. */
/**********************************************************************/
void cannot_execute(int client)
{
char buf[1024];

sprintf(buf, "HTTP/1.0 500 Internal Server Errorrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-type: text/htmlrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "rn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "

Error prohibited CGI execution.rn");
send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Print out an error message with perror() (for system errors; based
* on value of errno, which indicates system call errors) and exit the
* program indicating an error. */
/**********************************************************************/
void error_die(const char *sc)
{
perror(sc);
exit(1);
}

/**********************************************************************/
/* Execute a CGI script.  Will need to set environment variables as
* appropriate.
* Parameters: client socket descriptor
*             path to the CGI script */
/**********************************************************************/
void execute_cgi(int client, const char *path,
                 const char *method, const char *query_string)
{
char buf[1024];
int cgi_output[2];
int cgi_input[2];
pid_t pid;
int status;
int i;
char c;
int numchars = 1;
int content_length = -1;

buf[0] = 'A'; buf[1] = '';
if (strcasecmp(method, "GET") == 0)
  while ((numchars > 0) && strcmp("n", buf))  /* read & discard headers */
   numchars = get_line(client, buf, sizeof(buf));
else    /* POST */
{
  numchars = get_line(client, buf, sizeof(buf));
  while ((numchars > 0) && strcmp("n", buf))
  {
   buf[15] = '';
   if (strcasecmp(buf, "Content-Length:") == 0)
    content_length = atoi(&(buf[16]));
   numchars = get_line(client, buf, sizeof(buf));
  }
  if (content_length == -1) {
   bad_request(client);
   return;
  }
}

sprintf(buf, "HTTP/1.0 200 OKrn");
send(client, buf, strlen(buf), 0);

if (pipe(cgi_output) < 0) {
  cannot_execute(client);
  return;
}
if (pipe(cgi_input) < 0) {
  cannot_execute(client);
  return;
}

if ( (pid = fork()) < 0 ) {
  cannot_execute(client);
  return;
}
if (pid == 0)  /* child: CGI script */
{
  char meth_env[255];
  char query_env[255];
  char length_env[255];

  dup2(cgi_output[1], 1);
  dup2(cgi_input[0], 0);
  close(cgi_output[0]);
  close(cgi_input[1]);
  sprintf(meth_env, "REQUEST_METHOD=%s", method);
  putenv(meth_env);
  if (strcasecmp(method, "GET") == 0) {
   sprintf(query_env, "QUERY_STRING=%s", query_string);
   putenv(query_env);
  }
  else {   /* POST */
   sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
   putenv(length_env);
  }
  execl(path, path, NULL);
  exit(0);
} else {    /* parent */
  close(cgi_output[1]);
  close(cgi_input[0]);
  if (strcasecmp(method, "POST") == 0)
   for (i = 0; i < content_length; i++) {
    recv(client, &c, 1, 0);
    write(cgi_input[1], &c, 1);
   }
  while (read(cgi_output[0], &c, 1) > 0)
   send(client, &c, 1, 0);

  close(cgi_output[0]);
  close(cgi_input[1]);
  waitpid(pid, &status, 0);
}
}

/**********************************************************************/
/* Get a line from a socket, whether the line ends in a newline,
* carriage return, or a CRLF combination.  Terminates the string read
* with a null character.  If no newline indicator is found before the
* end of the buffer, the string is terminated with a null.  If any of
* the above three line terminators is read, the last character of the
* string will be a linefeed and the string will be terminated with a
* null character.
* Parameters: the socket descriptor
*             the buffer to save the data in
*             the size of the buffer
* Returns: the number of bytes stored (excluding null) */
/**********************************************************************/
int get_line(int sock, char *buf, int size)
{
int i = 0;
char c = '';
int n;

while ((i < size - 1) && (c != 'n'))
{
  n = recv(sock, &c, 1, 0);
  /* DEBUG printf("%02Xn", c); */
  if (n > 0)
  {
   if (c == 'r')
   {
    n = recv(sock, &c, 1, MSG_PEEK);
    /* DEBUG printf("%02Xn", c); */
    if ((n > 0) && (c == 'n'))
     recv(sock, &c, 1, 0);
    else
     c = 'n';
   }
   buf = c;
   i++;
  }
  else
   c = 'n';
}
buf = '';

return(i);
}

/**********************************************************************/
/* Return the informational HTTP headers about a file. */
/* Parameters: the socket to print the headers on
*             the name of the file */
/**********************************************************************/
void headers(int client, const char *filename)
{
char buf[1024];
(void)filename;  /* could use filename to determine file type */

strcpy(buf, "HTTP/1.0 200 OKrn");
send(client, buf, strlen(buf), 0);
strcpy(buf, SERVER_STRING);
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-Type: text/htmlrn");
send(client, buf, strlen(buf), 0);
strcpy(buf, "rn");
send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Give a client a 404 not found status message. */
/**********************************************************************/
void not_found(int client)
{
char buf[1024];

sprintf(buf, "HTTP/1.0 404 NOT FOUNDrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, SERVER_STRING);
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-Type: text/htmlrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "rn");
send(client, buf, strlen(buf), 0);
sprintf(buf, " rn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "

The server could not fulfillrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "your request because the resource specifiedrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "is unavailable or nonexistent.rn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "rn");
send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Send a regular file to the client.  Use headers, and report
* errors to client if they occur.
* Parameters: a pointer to a file structure produced from the socket
*              file descriptor
*             the name of the file to serve */
/**********************************************************************/
void serve_file(int client, const char *filename)
{
FILE *resource = NULL;
int numchars = 1;
char buf[1024];

buf[0] = 'A'; buf[1] = '';
while ((numchars > 0) && strcmp("n", buf))  /* read & discard headers */
  numchars = get_line(client, buf, sizeof(buf));

resource = fopen(filename, "r");
if (resource == NULL)
  not_found(client);
else
{
  headers(client, filename);
  cat(client, resource);
}
fclose(resource);
}

/**********************************************************************/
/* This function starts the process of listening for web connections
* on a specified port.  If the port is 0, then dynamically allocate a
* port and modify the original port variable to reflect the actual
* port.
* Parameters: pointer to variable containing the port to connect on
* Returns: the socket */
/**********************************************************************/
int startup(u_short *port)
{
int httpd = 0;
struct sockaddr_in name;

httpd = socket(PF_INET, SOCK_STREAM, 0);
if (httpd == -1)
  error_die("socket");
memset(&name, 0, sizeof(name));
name.sin_family = AF_INET;
name.sin_port = htons(*port);
name.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0)
  error_die("bind");
if (*port == 0)  /* if dynamically allocating a port */
{
  socklen_t  namelen = sizeof(name);
  if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)
   error_die("getsockname");
  *port = ntohs(name.sin_port);
}
if (listen(httpd, 5) < 0)
  error_die("listen");
return(httpd);
}

/**********************************************************************/
/* Inform the client that the requested web method has not been
* implemented.
* Parameter: the client socket */
/**********************************************************************/
void unimplemented(int client)
{
char buf[1024];

sprintf(buf, "HTTP/1.0 501 Method Not Implementedrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, SERVER_STRING);
send(client, buf, strlen(buf), 0);
sprintf(buf, "Content-Type: text/htmlrn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "rn");
send(client, buf, strlen(buf), 0);
sprintf(buf, " rn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "

HTTP request method not supported.rn");
send(client, buf, strlen(buf), 0);
sprintf(buf, "rn");
send(client, buf, strlen(buf), 0);
}

/**********************************************************************/

int main(void)
{
int server_sock = -1;
u_short port = 0;
int client_sock = -1;
struct sockaddr_in client_name;
socklen_t  client_name_len = sizeof(client_name);
//pthread_t newthread;

server_sock = startup(&port);
printf("httpd running on port %dn", port);

while (1)
{
  client_sock = accept(server_sock,
                       (struct sockaddr *)&client_name,
                       &client_name_len);
  if (client_sock == -1)
    error_die("accept");
  accept_request(client_sock);
//if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)
//  perror("pthread_create");
  }

close(server_sock);

return(0);
}