http.c

/*
 * Copyright (c) 2011 and 2012, Dustin Lundquist <dustin@null-ptr.net>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>
#include <stdlib.h> /* malloc() */
#include <string.h> /* strncpy() */
#include <strings.h> /* strncasecmp() */
#include <ctype.h> /* isblank() */

#include "http.h"
#include "protocol.h"

#define SERVER_NAME_LEN 256

static int parse_http_header(const char *, size_t, char **);
static int get_header(const char *, const char *, int, char **);
static int next_header(const char **, int *);

static const protocol_t http_protocol_st = {
    .default_port =                 80,
    .parse_packet = &parse_http_header,
};
const protocol_t *const http_protocol = &http_protocol_st;

/*
 * Parses a HTTP request for the Host: header
 *
 * Returns:
 *  >=0  - length of the hostname and updates *hostname
 *         caller is responsible for freeing *hostname
 *  -1   - Incomplete request
 *  -2   - No Host header included in this request
 *  -3   - Invalid hostname pointer
 *  -4   - malloc failure
 *  < -4 - Invalid HTTP request
 *
 */
static int
parse_http_header(const char *data, size_t data_len, char **hostname)
{
    int result, i;

    if (hostname == NULL)
        return -3;

    if (data_len == 0)
        return -1;

    result = get_header("Host:", data, data_len, hostname);
    if (result < 0)
        return result;

    /*
     *  if the user specifies the port in the request, it is included here.
     *  Host: example.com:80
     *  so we trim off port portion
     */
    for (i = result - 1; i >= 0; i--)
        if ((*hostname)[i] == ':') {
            (*hostname)[i] = '\0';
            result         = i;
            break;
        }

    return result;
}

static int
get_header(const char *header, const char *data, int data_len, char **value)
{
    int len, header_len;

    header_len = strlen(header);

    /* loop through headers stopping at first blank line */
    while ((len = next_header(&data, &data_len)) != 0)
        if (len > header_len && strncasecmp(header, data, header_len) == 0) {
            /* Eat leading whitespace */
            while (header_len < len && isblank(data[header_len]))
                header_len++;

            *value = malloc(len - header_len + 1);
            if (*value == NULL)
                return -4;

            strncpy(*value, data + header_len, len - header_len);
            (*value)[len - header_len] = '\0';

            return len - header_len;
        }

    /* If there is no data left after reading all the headers then we do not
     * have a complete HTTP request, there must be a blank line */
    if (data_len == 0)
        return -1;

    return -2;
}

static int
next_header(const char **data, int *len)
{
    int header_len;

    /* perhaps we can optimize this to reuse the value of header_len, rather
     * than scanning twice.
     * Walk our data stream until the end of the header */
    while (*len > 2 && (*data)[0] != '\r' && (*data)[1] != '\n') {
        (*len)--;
        (*data)++;
    }

    /* advanced past the <CR><LF> pair */
    *data += 2;
    *len  -= 2;

    /* Find the length of the next header */
    header_len = 0;
    while (*len > header_len + 1
           && (*data)[header_len] != '\r'
           && (*data)[header_len + 1] != '\n')
        header_len++;

    return header_len;
}