CoCalc -- request.c

GitHub Repository: remzi-arpacidusseau/ostep-projects
Path: blob/master/concurrency-webserver/src/request.c
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#include "io_helper.h"
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#include "request.h"
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//
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// Some of this code stolen from Bryant/O'Halloran
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// Hopefully this is not a problem ... :)
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//
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#define MAXBUF (8192)
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void request_error(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg) {
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    char buf[MAXBUF], body[MAXBUF];
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    // Create the body of error message first (have to know its length for header)
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    sprintf(body, ""
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	    "<!doctype html>\r\n"
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	    "<head>\r\n"
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	    "  <title>OSTEP WebServer Error</title>\r\n"
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	    "</head>\r\n"
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	    "<body>\r\n"
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	    "  <h2>%s: %s</h2>\r\n" 
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	    "  <p>%s: %s</p>\r\n"
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	    "</body>\r\n"
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	    "</html>\r\n", errnum, shortmsg, longmsg, cause);
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    // Write out the header information for this response
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    sprintf(buf, "HTTP/1.0 %s %s\r\n", errnum, shortmsg);
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    write_or_die(fd, buf, strlen(buf));
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    sprintf(buf, "Content-Type: text/html\r\n");
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    write_or_die(fd, buf, strlen(buf));
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    sprintf(buf, "Content-Length: %lu\r\n\r\n", strlen(body));
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    write_or_die(fd, buf, strlen(buf));
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    // Write out the body last
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    write_or_die(fd, body, strlen(body));
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}
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//
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// Reads and discards everything up to an empty text line
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//
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void request_read_headers(int fd) {
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    char buf[MAXBUF];
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    readline_or_die(fd, buf, MAXBUF);
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    while (strcmp(buf, "\r\n")) {
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	readline_or_die(fd, buf, MAXBUF);
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    }
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    return;
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}
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//
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// Return 1 if static, 0 if dynamic content
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// Calculates filename (and cgiargs, for dynamic) from uri
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//
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int request_parse_uri(char *uri, char *filename, char *cgiargs) {
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    char *ptr;
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    if (!strstr(uri, "cgi")) { 
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	// static
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	strcpy(cgiargs, "");
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	sprintf(filename, ".%s", uri);
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	if (uri[strlen(uri)-1] == '/') {
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	    strcat(filename, "index.html");
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	}
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	return 1;
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    } else { 
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	// dynamic
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	ptr = index(uri, '?');
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	if (ptr) {
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	    strcpy(cgiargs, ptr+1);
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	    *ptr = '\0';
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	} else {
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	    strcpy(cgiargs, "");
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	}
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	sprintf(filename, ".%s", uri);
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	return 0;
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    }
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}
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//
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// Fills in the filetype given the filename
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//
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void request_get_filetype(char *filename, char *filetype) {
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    if (strstr(filename, ".html")) 
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	strcpy(filetype, "text/html");
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    else if (strstr(filename, ".gif")) 
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	strcpy(filetype, "image/gif");
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    else if (strstr(filename, ".jpg")) 
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	strcpy(filetype, "image/jpeg");
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    else 
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	strcpy(filetype, "text/plain");
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}
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void request_serve_dynamic(int fd, char *filename, char *cgiargs) {
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    char buf[MAXBUF], *argv[] = { NULL };
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    // The server does only a little bit of the header.  
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    // The CGI script has to finish writing out the header.
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    sprintf(buf, ""
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	    "HTTP/1.0 200 OK\r\n"
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	    "Server: OSTEP WebServer\r\n");
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    write_or_die(fd, buf, strlen(buf));
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    if (fork_or_die() == 0) {                        // child
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	setenv_or_die("QUERY_STRING", cgiargs, 1);   // args to cgi go here
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	dup2_or_die(fd, STDOUT_FILENO);              // make cgi writes go to socket (not screen)
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	extern char **environ;                       // defined by libc 
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	execve_or_die(filename, argv, environ);
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    } else {
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	wait_or_die(NULL);
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    }
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}
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void request_serve_static(int fd, char *filename, int filesize) {
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    int srcfd;
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    char *srcp, filetype[MAXBUF], buf[MAXBUF];
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    request_get_filetype(filename, filetype);
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    srcfd = open_or_die(filename, O_RDONLY, 0);
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    // Rather than call read() to read the file into memory, 
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    // which would require that we allocate a buffer, we memory-map the file
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    srcp = mmap_or_die(0, filesize, PROT_READ, MAP_PRIVATE, srcfd, 0);
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    close_or_die(srcfd);
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    // put together response
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    sprintf(buf, ""
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	    "HTTP/1.0 200 OK\r\n"
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	    "Server: OSTEP WebServer\r\n"
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	    "Content-Length: %d\r\n"
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	    "Content-Type: %s\r\n\r\n", 
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	    filesize, filetype);
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    write_or_die(fd, buf, strlen(buf));
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    //  Writes out to the client socket the memory-mapped file 
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    write_or_die(fd, srcp, filesize);
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    munmap_or_die(srcp, filesize);
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}
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// handle a request
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void request_handle(int fd) {
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    int is_static;
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    struct stat sbuf;
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    char buf[MAXBUF], method[MAXBUF], uri[MAXBUF], version[MAXBUF];
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    char filename[MAXBUF], cgiargs[MAXBUF];
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    readline_or_die(fd, buf, MAXBUF);
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    sscanf(buf, "%s %s %s", method, uri, version);
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    printf("method:%s uri:%s version:%s\n", method, uri, version);
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    if (strcasecmp(method, "GET")) {
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	request_error(fd, method, "501", "Not Implemented", "server does not implement this method");
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	return;
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    }
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    request_read_headers(fd);
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    is_static = request_parse_uri(uri, filename, cgiargs);
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    if (stat(filename, &sbuf) < 0) {
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	request_error(fd, filename, "404", "Not found", "server could not find this file");
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	return;
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    }
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    if (is_static) {
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	if (!(S_ISREG(sbuf.st_mode)) || !(S_IRUSR & sbuf.st_mode)) {
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	    request_error(fd, filename, "403", "Forbidden", "server could not read this file");
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	    return;
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	}
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	request_serve_static(fd, filename, sbuf.st_size);
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    } else {
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	if (!(S_ISREG(sbuf.st_mode)) || !(S_IXUSR & sbuf.st_mode)) {
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	    request_error(fd, filename, "403", "Forbidden", "server could not run this CGI program");
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	    return;
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	}
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	request_serve_dynamic(fd, filename, cgiargs);
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    }
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}
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