CMUProjects/proxy.c at main · marcuswu5/CMUProjects · GitHub

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/**
 * proxy.c
 *
 * Acts as a server proxy
 * Handles multiple requests by creating threads. All processes are concurrently
 * handled. Server constantly searches for requests, and does not shut down
 * after processing requests. Proxy follows the HTTP/1.0 protocol, and
 * translates all HTTP/1.1 requests to HTTP/1.0 requests. All additional headers
 * given to the proxy are forwarded to the server. Connection based errors will
 * cause the proxy to end the connection. Function based errors notify the
 * server and attempt to continue. Any errors provided by the server are
 * forwarded back to the client.
 *
 */

#include "csapp.h"
#include "http_parser.h"

#include <assert.h>
#include <ctype.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

#include <errno.h>
#include <netdb.h>
#include <netinet/in.h>
#include <pthread.h>
#include <signal.h>
#include <sys/socket.h>
#include <sys/types.h>

/*
 * Debug macros, which can be enabled by adding -DDEBUG in the Makefile
 * Use these if you find them useful, or delete them if not
 */
#ifdef DEBUG
#define dbg_assert(...) assert(__VA_ARGS__)
#define dbg_printf(...) fprintf(stderr, __VA_ARGS__)
#else
#define dbg_assert(...)
#define dbg_printf(...)
#endif

/** @brief bool for verbose mode */
volatile bool verbose = false;

/** @brief the size of the http portion of a request */
#define HTTPSIZE 8;

/*
 * String to use for the User-Agent header.
 * Don't forget to terminate with \r\n
 */
static const char *header_user_agent = "Mozilla/5.0"
                                       " (X11; Linux x86_64; rv:3.10.0)"
                                       " Gecko/20250408 Firefox/63.0.1";

/*
 * clienterror - returns an error message to the client
 */
void clienterror(int fd, const char *errnum, const char *shortmsg,
                 const char *longmsg) {
    char buf[MAXLINE];
    char body[MAXBUF];
    size_t buflen;
    size_t bodylen;

    /* Build the HTTP response body */
    bodylen = snprintf(body, MAXBUF,
                       "<!DOCTYPE html>\r\n"
                       "<html>\r\n"
                       "<head><title>Tiny Error</title></head>\r\n"
                       "<body bgcolor=\"ffffff\">\r\n"
                       "<h1>%s: %s</h1>\r\n"
                       "<p>%s</p>\r\n"
                       "<hr /><em>The Tiny Web server</em>\r\n"
                       "</body></html>\r\n",
                       errnum, shortmsg, longmsg);
    if (bodylen >= MAXBUF) {
        return; // Overflow!
    }

    /* Build the HTTP response headers */
    buflen = snprintf(buf, MAXLINE,
                      "HTTP/1.0 %s %s\r\n"
                      "Content-Type: text/html\r\n"
                      "Content-Length: %zu\r\n\r\n",
                      errnum, shortmsg, bodylen);
    if (buflen >= MAXLINE) {
        return; // Overflow!
    }

    /* Write the headers */
    if (rio_writen(fd, buf, buflen) < 0) {
        fprintf(stderr, "Error writing error response headers to client\n");
        return;
    }

    /* Write the body */
    if (rio_writen(fd, body, bodylen) < 0) {
        fprintf(stderr, "Error writing error response body to client\n");
        return;
    }
}

void sigpipe_handler(int sig) {
    if (verbose) {
        sio_printf("SIGPIPE: %d caught by Handler\n", sig);
    }
}

/**
 * @brief Prints out the request parsed by parser
 *
 * Mostly used for debug purposes
 *
 * @param[in] parser The parser object
 */
void displayParseLine(parser_t *parser) {
    const char *parseVal;
    for (int i = 0; i < 7; i++) {
        if (parser_retrieve(parser, i, &parseVal) < 0) {
            sio_printf("Error parsing request\n");
        }
        if (verbose) {
            sio_printf("Got request: %s\n", parseVal);
        }
    }
}

/**
 * @brief connects to the server using the latest line parsed by parser
 *
 * @param[in] parser The parser that parsed the commnand
 * @param[out] hostHeader Pointer to location where a host header can be stored
 * @return file descriptor of connection
 */
int connectServer(parser_t *parser, char *hostHeader) {
    const char *host, *port, buf[MAXLINE];
    parser_retrieve(parser, HOST, &host);
    parser_retrieve(parser, PORT, &port);

    // Attempt connection
    int serverfd = open_clientfd(host, port);
    if (serverfd == -1) {
        if (verbose) {
            sio_printf("Server connection %s:%s not established\n", host, port);
        }
        return -1;
    } else if (serverfd == -2) {
        if (verbose) {
            sio_printf("%s:%s: %s\n", host, port, strerror(errno));
        }
        return -1;
    }
    if (verbose) {
        sio_printf("Successfully connected to %s at port %s\n", host, port);
    }
    sprintf(hostHeader, "Host: %s:%s\r\n", host, port);
    return serverfd;
}

/**
 * @brief gets the http version.
 * This should always return the same HTTP version
 *
 * @return the http request version that the proxy handles
 */
char *gethttp(void) {
    // Buffer is large enough to cover the string
    char buf[8];
    char *http;
    http = "HTTP/1.0";
    return http;
}

/**
 * @brief reads and parses the command line
 *
 * Handles any errors that might occur
 *
 * @param[out] line Mainly for debug purposes, stores the request line
 * @param[out] parseState Stores the parse state after parsing
 * @param[in] parser An initialized parser to be used for parsing
 * @param[in] fd The file descriptor to be parsed
 * @return number of request characters parsed on success, -1 on file reading
 * error, -2 on parsing error
 */
int readParse(char *line, parser_state *parseState, parser_t *parser, int fd) {
    // Initialize rio
    rio_t rio;
    rio_readinitb(&rio, fd);

    // Parse the request line
    ssize_t read = rio_readlineb(&rio, line, MAXLINE);
    if (read == 0) {
        return 0;
    } else if (read == -1) {
        if (verbose) {
            sio_printf("Error reading request\n");
        }
        return -1;
    } else {
        *parseState = parser_parse_line(parser, line);
        if (*parseState == ERROR) {
            if (verbose) {
                sio_printf("Error while parsing\n");
            }
            return -2;
        }
    }
    // Parse the other headers
    char tmpline[PARSER_MAXLINE] = "";
    if (rio_readlineb(&rio, &tmpline, PARSER_MAXLINE) < 0) {
        fprintf(stderr, "Failed to read client headers\n");
    }
    while (strcmp(tmpline, "\r\n")) {
        if (parser_parse_line(parser, tmpline) == ERROR) {
            fprintf(stderr, "Failed to parse client headers\n");
        }
        if (rio_readlineb(&rio, &tmpline, PARSER_MAXLINE) < 0) {
            fprintf(stderr, "Failed to read client headers\n");
        }
    }
    return read;
}

/**
 * @brief Given a request, forwards it to the host server
 *
 * @param[in] parser The parser that parsed the request
 * @param[in] count The number of words parsed, used for smaller buffer sizes
 * @param[in] clientfd The file descriptor of the client
 * @return 0 on success, -1 on failure
 */
int forward(parser_t *parser, ssize_t count, int clientfd) {
    // Create the connection to the server
    int serverfd;
    char hostHeader[PARSER_MAXLINE];
    if ((serverfd = connectServer(parser, hostHeader)) < 0) {
        return -1;
    }

    // Declare variables for request string
    const char *cmd, *pathname, *httpval;
    httpval = gethttp();

    parser_retrieve(parser, METHOD, &cmd);
    parser_retrieve(parser, PATH, &pathname);

    // Req is a string containing the request line
    // Add 5 for spaces, \n, \r
    size_t reqsize = strlen(cmd) + strlen(pathname) + strlen(httpval) + 4;
    char req[reqsize];

    snprintf(req, MAXLINE, "%s %s %s\r\n", cmd, pathname, httpval);

    // User-Agent header
    // Add 16 for additional characters
    size_t userAgentSize = strlen(header_user_agent) + 16;
    char userAgent[userAgentSize];
    sprintf(userAgent, "User-Agent: %s\r\n", header_user_agent);

    // Connection header
    char *connection = "Connection: close\r\n";
    // Proxy connection header
    char *proxyConnection = "Proxy-Connection: close\r\n";

    // Forwarding messages
    char fwd[PARSER_MAXLINE] = "";
    header_t *header = parser_lookup_header(parser, "Request-ID");
    while (header != NULL) {
        char join[PARSER_MAXLINE];
        sprintf(join, "%s: %s\r\n", header->name, header->value);
        strcat(fwd, join);
        header = parser_retrieve_next_header(parser);
    }

    // Construct the full message
    // Plus 2 for \r\n
    size_t msglen = strlen(req) + strlen(hostHeader) + strlen(userAgent) +
                    strlen(connection) + strlen(proxyConnection) + strlen(fwd) +
                    2;
    char msg[msglen];
    sprintf(msg, "%s%s%s%s%s%s\r\n", req, hostHeader, userAgent, connection,
            proxyConnection, fwd);
    if (verbose) {
        sio_printf("msg:\n%s\n", msg);
    }

    // Send the message
    if (rio_writen(serverfd, (void *)msg, strlen(msg)) < 0) {
        fprintf(stderr, "Failed to write message for client\n");
    }
    if (verbose) {
        sio_printf("Message sent\n");
    }

    // Read the response
    bool continueRead = true;

    while (continueRead) {
        size_t readlen;
        char response[MAXLINE];
        ssize_t read = rio_readn(serverfd, response, MAXLINE);
        if (read < 0) {
            fprintf(stderr, "Failed to read server response\n");
        }
        // Check if the entire response has been parsed
        if (read < MAXLINE) {
            continueRead = false;
            readlen = read;
            if (verbose) {
                sio_printf("Sending response to client\n");
            }
        } else {
            readlen = MAXLINE;
        }
        // Write the parsed data
        if (rio_writen(clientfd, response, readlen) < 0) {
            fprintf(stderr, "Failed to write message for client\n");
        }
    }

    if (verbose) {
        sio_printf("Response Sent, closing connection\n");
    }

    // Close the connection with the server
    close(serverfd);

    return 0;
}

/**
 * @brief handles a single request
 *
 * Creates a new thread to handle the request
 * @param[in] vargp pointer storing the fd of the client making the request
 * @return NULL when process terminates
 */
void *thread(void *vargp) {
    int clientfd = *((int *)vargp);
    bool connected = true;
    // Setup parser
    parser_t *parser = parser_new();

    // Hold the connection
    do {
        // Create the value to store parser data
        // Create the buffer
        char line[MAXLINE];
        parser_state parseState;
        int count = readParse(line, &parseState, parser, clientfd);
        if (count == 0) {
            connected = false;
        } else if (count == -1 || count == -2) {
            clienterror(clientfd, "400", "Bad Request",
                        "Did not recieve a proper request");
            // Reset parse
            parser_free(parser);
            parser = parser_new();
            // Wait for another request when there is an error
        } else {
            if (parseState == REQUEST) {
                const char *cmd;
                if (parser_retrieve(parser, METHOD, &cmd) < 0) {
                    fprintf(stderr, "Failed to read cmd\n");
                }
                if (strcmp(cmd, "POST") == 0) {
                    clienterror(clientfd, "501", "Not Implemented",
                                "Proxy does not accept POST requests");
                }
                if (verbose) {
                    displayParseLine(parser);
                }
                // Forward the messsage to the server
                int status = forward(parser, count, clientfd);
                // Reset parser (on error or success either way)
                parser_free(parser);
                parser = parser_new();
                if (status == -1) {
                    connected = false;
                }
                connected = false;

            } else {

                // Did not get a request
                clienterror(clientfd, "400", "Bad Request",
                            "Did not recieve a proper request");
                parser_free(parser);
                parser = parser_new();
            }
        }

    } while (connected);
    // Cleanup pointers
    parser_free(parser);
    close(clientfd);
    pthread_detach(pthread_self());
    return NULL;
}

int main(int argc, char **argv) {
    // Install the handler
    Signal(SIGPIPE, &sigpipe_handler);
    if (verbose) {
        sio_printf("Signal handler installed\n");
    }
    // Parse the command line
    char *port;
    if (argv[1] == NULL) {
        argv[1] = "8000";
    }
    port = argv[1];
    // Begin listening for connections
    int listenfd = open_listenfd(port);
    if (listenfd < 0) {
        sio_printf("Failed to connect to port %s\n", argv[1]);
        exit(0);
    }
    if (verbose) {
        sio_printf("Created port at %s\n", port);
    }

    // Initialize variables
    struct sockaddr clientaddr;
    socklen_t clientaddr_len;
    pthread_t tid;
    int *clientfd;
    // Keep the server on
    do {
        clientaddr_len = sizeof(clientaddr);
        clientfd = malloc(sizeof(int));
        if (clientfd == NULL) {
            // Try malloc again
        } else {
            // Wait for connection
            *clientfd = accept(listenfd, &clientaddr, &clientaddr_len);
            if (*clientfd < 0) {
                sio_printf("Failed to accept connection: %s\n",
                           strerror(errno));
            } else {
                if (verbose) {
                    sio_printf("Accepted client\n");
                }
            }
            // Create thread to handle the request
            int err;
            if ((err = pthread_create(&tid, NULL, thread, clientfd)) != 0) {
                sio_printf("Failed to create thread: %d\n", err);
                close(listenfd);
                return 0;
            }
        }
    } while (true);

    // Cleanup fd
    close(listenfd);

    return 0;
}