path: root/htp/htp_request_generic.c

/***************************************************************************
 * Copyright (c) 2009-2010 Open Information Security Foundation
 * Copyright (c) 2010-2013 Qualys, Inc.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.

 * - 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.

 * - Neither the name of the Qualys, Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 * 
 * 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,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 ***************************************************************************/

/**
 * @file
 * @author Ivan Ristic <ivanr@webkreator.com>
 */

#include "htp_config_auto.h"

#include "htp_private.h"

/**
 * Extract one request header. A header can span multiple lines, in
 * which case they will be folded into one before parsing is attempted.
 *
 * @param[in] connp
 * @param[in] data
 * @param[in] len
 * @return HTP_OK or HTP_ERROR
 */
htp_status_t htp_process_request_header_generic(htp_connp_t *connp, unsigned char *data, size_t len) {
    // Create a new header structure.
    htp_header_t *h = calloc(1, sizeof (htp_header_t));
    if (h == NULL) return HTP_ERROR;

    // Now try to parse the header.
    if (htp_parse_request_header_generic(connp, h, data, len) != HTP_OK) {
        free(h);
        return HTP_ERROR;
    }

    #ifdef HTP_DEBUG
    fprint_bstr(stderr, "Header name", h->name);
    fprint_bstr(stderr, "Header value", h->value);
    #endif

    // Do we already have a header with the same name?
    htp_header_t *h_existing = htp_table_get(connp->in_tx->request_headers, h->name);
    if (h_existing != NULL) {
        // TODO Do we want to have a list of the headers that are
        //      allowed to be combined in this way?
        if ((h_existing->flags & HTP_FIELD_REPEATED) == 0) {
            // This is the second occurence for this header.
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Repetition for header");
        } else {
            // For simplicity reasons, we count the repetitions of all headers
            if (connp->in_tx->req_header_repetitions < HTP_MAX_HEADERS_REPETITIONS) {
                connp->in_tx->req_header_repetitions++;
            } else {
                bstr_free(h->name);
                bstr_free(h->value);
                free(h);
                return HTP_OK;
            }
        }
        // Keep track of repeated same-name headers.
        h_existing->flags |= HTP_FIELD_REPEATED;

        // Having multiple C-L headers is against the RFC but
        // servers may ignore the subsequent headers if the values are the same.
        if (bstr_cmp_c_nocase(h->name, "Content-Length") == 0) {
            // Don't use string comparison here because we want to
            // ignore small formatting differences.

            int64_t existing_cl = htp_parse_content_length(h_existing->value, NULL);
            int64_t new_cl = htp_parse_content_length(h->value, NULL);
            // Ambiguous response C-L value.
            if ((existing_cl == -1) || (new_cl == -1) || (existing_cl != new_cl)) {
                htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Ambiguous request C-L value");
            }
            // Ignoring the new C-L header that has the same value as the previous ones.
        } else {
            // Add to the existing header.
            bstr *new_value = bstr_expand(h_existing->value, bstr_len(h_existing->value) + 2 + bstr_len(h->value));
            if (new_value == NULL) {
                bstr_free(h->name);
                bstr_free(h->value);
                free(h);
                return HTP_ERROR;
            }

            h_existing->value = new_value;
            bstr_add_mem_noex(h_existing->value, ", ", 2);
            bstr_add_noex(h_existing->value, h->value);
        }

        // The new header structure is no longer needed.
        bstr_free(h->name);
        bstr_free(h->value);
        free(h);
    } else {
        // Add as a new header.
        if (htp_table_add(connp->in_tx->request_headers, h->name, h) != HTP_OK) {
            bstr_free(h->name);
            bstr_free(h->value);
            free(h);
        }
    }

    return HTP_OK;
}

/**
 * Generic request header parser.
 *
 * @param[in] connp
 * @param[in] h
 * @param[in] data
 * @param[in] len
 * @return HTP_OK or HTP_ERROR
 */
htp_status_t htp_parse_request_header_generic(htp_connp_t *connp, htp_header_t *h, unsigned char *data, size_t len) {
    size_t name_start, name_end;
    size_t value_start, value_end;

    htp_chomp(data, &len);

    name_start = 0;

    // Look for the colon.
    size_t colon_pos = 0;
    while ((colon_pos < len) && (data[colon_pos] != '\0') && (data[colon_pos] != ':')) colon_pos++;

    if ((colon_pos == len) || (data[colon_pos] == '\0')) {
        // Missing colon.

        h->flags |= HTP_FIELD_UNPARSEABLE;

        // Log only once per transaction.
        if (!(connp->in_tx->flags & HTP_FIELD_UNPARSEABLE)) {
            connp->in_tx->flags |= HTP_FIELD_UNPARSEABLE;
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request field invalid: colon missing");
        }

        // We handle this case as a header with an empty name, with the value equal
        // to the entire input string.

        // TODO Apache will respond to this problem with a 400.

        // Now extract the name and the value
        h->name = bstr_dup_c("");
        if (h->name == NULL) return HTP_ERROR;

        h->value = bstr_dup_mem(data, len);
        if (h->value == NULL) {
            bstr_free(h->name);
            return HTP_ERROR;
        }

        return HTP_OK;
    }

    if (colon_pos == 0) {
        // Empty header name.

        h->flags |= HTP_FIELD_INVALID;

        // Log only once per transaction.
        if (!(connp->in_tx->flags & HTP_FIELD_INVALID)) {
            connp->in_tx->flags |= HTP_FIELD_INVALID;
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request field invalid: empty name");
        }
    }

    name_end = colon_pos;

    // Ignore LWS after field-name.
    size_t prev = name_end;
    while ((prev > name_start) && (htp_is_lws(data[prev - 1]))) {
        // LWS after header name.

        prev--;
        name_end--;

        h->flags |= HTP_FIELD_INVALID;

        // Log only once per transaction.
        if (!(connp->in_tx->flags & HTP_FIELD_INVALID)) {
            connp->in_tx->flags |= HTP_FIELD_INVALID;
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request field invalid: LWS after name");
        }
    }

    // Header value.

    value_start = colon_pos;

    // Go over the colon.
    if (value_start < len) {
        value_start++;
    }

    // Ignore LWS before field-content.
    while ((value_start < len) && (htp_is_lws(data[value_start]))) {
        value_start++;
    }

    // Look for the end of field-content.
    value_end = len;

    // Ignore LWS after field-content.
    prev = value_end - 1;
    while ((prev > value_start) && (htp_is_lws(data[prev]))) {
        prev--;
        value_end--;
    }

    // Check that the header name is a token.
    size_t i = name_start;
    while (i < name_end) {
        if (!htp_is_token(data[i])) {
            // Incorrectly formed header name.

            h->flags |= HTP_FIELD_INVALID;

            // Log only once per transaction.
            if (!(connp->in_tx->flags & HTP_FIELD_INVALID)) {
                connp->in_tx->flags |= HTP_FIELD_INVALID;
                htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request header name is not a token");
            }

            break;
        }

        i++;
    }

    // Now extract the name and the value
    h->name = bstr_dup_mem(data + name_start, name_end - name_start);
    if (h->name == NULL) return HTP_ERROR;

    h->value = bstr_dup_mem(data + value_start, value_end - value_start);
    if (h->value == NULL) {
        bstr_free(h->name);
        return HTP_ERROR;
    }

    return HTP_OK;
}

/**
 * Generic request line parser.
 *
 * @param[in] connp
 * @return HTP_OK or HTP_ERROR
 */
htp_status_t htp_parse_request_line_generic(htp_connp_t *connp) {
    return htp_parse_request_line_generic_ex(connp, 0 /* NUL does not terminates line */);
}

htp_status_t htp_parse_request_line_generic_ex(htp_connp_t *connp, int nul_terminates) {
    htp_tx_t *tx = connp->in_tx;
    unsigned char *data = bstr_ptr(tx->request_line);
    size_t len = bstr_len(tx->request_line);
    size_t pos = 0;
    size_t mstart = 0;
    size_t start;
    size_t bad_delim;

    if (nul_terminates) {
        // The line ends with the first NUL byte.
        
        size_t newlen = 0;
        while ((pos < len) && (data[pos] != '\0')) {
            pos++;
            newlen++;
        }

        // Start again, with the new length.
        len = newlen;
        pos = 0;
    }

    // skip past leading whitespace. IIS allows this
    while ((pos < len) && htp_is_space(data[pos])) pos++;
    if (pos) {
        htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request line: leading whitespace");
        mstart = pos;

        if (connp->cfg->requestline_leading_whitespace_unwanted != HTP_UNWANTED_IGNORE) {
            // reset mstart so that we copy the whitespace into the method
            mstart = 0;
            // set expected response code to this anomaly
            tx->response_status_expected_number = connp->cfg->requestline_leading_whitespace_unwanted;
        }
    }

    // The request method starts at the beginning of the
    // line and ends with the first whitespace character.
    while ((pos < len) && (!htp_is_space(data[pos]))) pos++;

    // No, we don't care if the method is empty.

    tx->request_method = bstr_dup_mem(data + mstart, pos - mstart);
    if (tx->request_method == NULL) return HTP_ERROR;

    #ifdef HTP_DEBUG
    fprint_raw_data(stderr, __func__, bstr_ptr(tx->request_method), bstr_len(tx->request_method));
    #endif

    tx->request_method_number = htp_convert_method_to_number(tx->request_method);

    bad_delim = 0;
    // Ignore whitespace after request method. The RFC allows
    // for only one SP, but then suggests any number of SP and HT
    // should be permitted. Apache uses isspace(), which is even
    // more permitting, so that's what we use here.
    while ((pos < len) && (isspace(data[pos]))) {
        if (!bad_delim && data[pos] != 0x20) {
            bad_delim++;
        }
        pos++;
    }
// Too much performance overhead for fuzzing
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
    if (bad_delim) {
        htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request line: non-compliant delimiter between Method and URI");
    }
#endif

    // Is there anything after the request method?
    if (pos == len) {
        // No, this looks like a HTTP/0.9 request.

        tx->is_protocol_0_9 = 1;
        tx->request_protocol_number = HTP_PROTOCOL_0_9;
        if (tx->request_method_number == HTP_M_UNKNOWN)
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request line: unknown method only");

        return HTP_OK;
    }

    start = pos;
    bad_delim = 0;
    if (tx->connp->cfg->allow_space_uri) {
        pos = len - 1;
        // Skips the spaces at the end of line (after protocol)
        while (pos > start && htp_is_space(data[pos])) pos--;
        // The URI ends with the last whitespace.
        while ((pos > start) && (data[pos] != 0x20)) {
            if (!bad_delim && htp_is_space(data[pos])) {
                bad_delim++;
            }
            pos--;
        }
        /* if we've seen some 'bad' delimiters, we retry with those */
        if (bad_delim && pos == start) {
            // special case: even though RFC's allow only SP (0x20), many
            // implementations allow other delimiters, like tab or other
            // characters that isspace() accepts.
            pos = len - 1;
            while ((pos > start) && (!htp_is_space(data[pos]))) pos--;
        } else {
            // reset bad_delim found in protocol part
            bad_delim = 0;
            for (size_t i = start; i < pos; i++) {
                if (data[i] != 0x20 && htp_is_space(data[i])) {
                    bad_delim = 1;
                    break;
                }
            }
        }
        if (bad_delim) {
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
            // warn regardless if we've seen non-compliant chars
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request line: URI contains non-compliant delimiter");
#endif
        } else if (pos == start) {
            pos = len;
        }
    } else {
        // The URI ends with the first whitespace.
        while ((pos < len) && (data[pos] != 0x20)) {
            if (!bad_delim && htp_is_space(data[pos])) {
                bad_delim++;
            }
            pos++;
        }
        /* if we've seen some 'bad' delimiters, we retry with those */
        if (bad_delim && pos == len) {
            // special case: even though RFC's allow only SP (0x20), many
            // implementations allow other delimiters, like tab or other
            // characters that isspace() accepts.
            pos = start;
            while ((pos < len) && (!htp_is_space(data[pos]))) pos++;
        }
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
        if (bad_delim) {
            // warn regardless if we've seen non-compliant chars
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request line: URI contains non-compliant delimiter");
        }
#endif
    }

    tx->request_uri = bstr_dup_mem(data + start, pos - start);
    if (tx->request_uri == NULL) return HTP_ERROR;

    #ifdef HTP_DEBUG
    fprint_raw_data(stderr, __func__, bstr_ptr(tx->request_uri), bstr_len(tx->request_uri));
    #endif

    // Ignore whitespace after URI.
    while ((pos < len) && (htp_is_space(data[pos]))) pos++;

    // Is there protocol information available?
    if (pos == len) {
        // No, this looks like a HTTP/0.9 request.

        tx->is_protocol_0_9 = 1;
        tx->request_protocol_number = HTP_PROTOCOL_0_9;
        if (tx->request_method_number == HTP_M_UNKNOWN)
            htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request line: unknown method and no protocol");

        return HTP_OK;
    }

    // The protocol information continues until the end of the line.
    tx->request_protocol = bstr_dup_mem(data + pos, len - pos);
    if (tx->request_protocol == NULL) return HTP_ERROR;

    tx->request_protocol_number = htp_parse_protocol(tx->request_protocol);
    if (tx->request_method_number == HTP_M_UNKNOWN && tx->request_protocol_number == HTP_PROTOCOL_INVALID)
        htp_log(connp, HTP_LOG_MARK, HTP_LOG_WARNING, 0, "Request line: unknown method and invalid protocol");

    #ifdef HTP_DEBUG
    fprint_raw_data(stderr, __func__, bstr_ptr(tx->request_protocol), bstr_len(tx->request_protocol));
    #endif

    return HTP_OK;
}