sf_snort_plugin_api.c

snort2.8.4版本

/*
 * sf_snort_plugin_api.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 2 as
 * published by the Free Software Foundation.  You may not use, modify or
 * distribute this program under any other version of the GNU General
 * Public License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) 2005-2008 Sourcefire, Inc.
 *
 * Author: Steve Sturges
 *         Andy  Mullican
 *
 * Date: 5/2005
 *
 * Dyanmic Rule Engine
 */
#include "sf_snort_packet.h"
#include "sf_snort_plugin_api.h"
#include "sf_dynamic_engine.h"

/* Need access to the snort-isms that were passed to the engine */
extern DynamicEngineData _ded;

/*
 *  Get the start and end of the buffer, as divined by the packet flags.
 *  This function is useful so that we don't have to figure out which buffer
 *  we are looking at twice, if we want to check two offsets one after the other.
 *
 *  return 1 if successful
 *  return < 0 if unsuccessful
 */
ENGINE_LINKAGE int getBuffer(void *packet, int flags, const u_int8_t **start, const u_int8_t **end)
{
    SFSnortPacket *p = (SFSnortPacket *)packet;
    if ((flags & CONTENT_BUF_NORMALIZED) && (p->flags & FLAG_ALT_DECODE))
    {
        *start = _ded.altBuffer;
        *end = *start + p->normalized_payload_size;
    }
    else if ((flags & CONTENT_BUF_RAW) || (flags & CONTENT_BUF_NORMALIZED))
    {
        *start = p->payload;
        *end = *start + p->payload_size;
    }
    else if (flags & CONTENT_BUF_URI)
    {
        if (p->flags & FLAG_HTTP_DECODE)
        {
            *start = _ded.uriBuffers[HTTP_BUFFER_URI]->uriBuffer;
            *end = *start + _ded.uriBuffers[HTTP_BUFFER_URI]->uriLength;
        }
        else
        {
            return CONTENT_TYPE_MISMATCH;
        }
    }
    else if (flags & CONTENT_BUF_HEADER)
    {
        if (p->flags & FLAG_HTTP_DECODE)
        {
            *start = _ded.uriBuffers[HTTP_BUFFER_HEADER]->uriBuffer;
            *end = *start + _ded.uriBuffers[HTTP_BUFFER_HEADER]->uriLength;
        }
        else
        {
            return CONTENT_TYPE_MISMATCH;
        }
    }
    else if (flags & CONTENT_BUF_POST)
    {
        if (p->flags & FLAG_HTTP_DECODE)
        {
            *start = _ded.uriBuffers[HTTP_BUFFER_CLIENT_BODY]->uriBuffer;
            *end = *start + _ded.uriBuffers[HTTP_BUFFER_CLIENT_BODY]->uriLength;
        }
        else
        {
            return CONTENT_TYPE_MISMATCH;
        }
    }
    else if (flags & CONTENT_BUF_METHOD)
    {
        if (p->flags & FLAG_HTTP_DECODE)
        {
            *start = _ded.uriBuffers[HTTP_BUFFER_METHOD]->uriBuffer;
            *end = *start + _ded.uriBuffers[HTTP_BUFFER_METHOD]->uriLength;
        }
        else
        {
            return CONTENT_TYPE_MISMATCH;
        }
    }
    else if (flags & CONTENT_BUF_COOKIE)
    {
        if (p->flags & FLAG_HTTP_DECODE)
        {
            *start = _ded.uriBuffers[HTTP_BUFFER_COOKIE]->uriBuffer;
            *end = *start + _ded.uriBuffers[HTTP_BUFFER_COOKIE]->uriLength;
        }
        else
        {
            return CONTENT_TYPE_MISMATCH;
        }
    }
    else
    {
        return CONTENT_TYPE_MISSING;
    }

    return CURSOR_IN_BOUNDS;
}


int checkCursorSimple(const u_int8_t *cursor, int flags, const u_int8_t *start, const u_int8_t *end, int offset)
{
    if ( cursor == NULL || !(flags & CONTENT_RELATIVE) )
        cursor = start;

    if ((cursor + offset < end) && (cursor + offset >= start))
        return CURSOR_IN_BOUNDS;

    return CURSOR_OUT_OF_BOUNDS;
}

/* Returns one if cursor is within the buffer */
int checkCursorInternal(void *p, int flags, int offset, const u_int8_t *cursor)
{
    const u_int8_t *start;
    const u_int8_t *end;
    int ret;
    SFSnortPacket *sp = (SFSnortPacket *) p;

    ret = getBuffer(sp, flags, &start, &end);

    if ( ret < 0 )
    {
        return ret;
    }  
    
    return checkCursorSimple(cursor, flags, start, end, offset);
}

int setCursorInternal(void *p, int flags, int offset, const u_int8_t **cursor)
{
    const u_int8_t *start;
    const u_int8_t *end;
    int       ret;
    SFSnortPacket *sp = (SFSnortPacket *) p;

    if(!cursor)
    {
        return RULE_NOMATCH;
    }

    ret = getBuffer(sp, flags, &start, &end);

    if ( ret < 0 )
    {
        return ret;
    }    

    if ( flags & JUMP_FROM_BEGINNING )
    {
        ret = checkCursorSimple(start, flags, start, end, offset);
    }
    else
    {
        ret = checkCursorSimple(*cursor, flags, start, end, offset);
    }

    if ( ret <= 0 )
    {
        return ret;
    }

    if ( flags & JUMP_FROM_BEGINNING )
    {
        *cursor = start + offset;
    }
    else
    {
        if ( !(flags & CONTENT_RELATIVE) )
            *cursor = start + offset;
        else if (cursor)
            *cursor += offset;
        else /* if not set, don't try to use it */
            *cursor = start + offset;
    }

    return CURSOR_IN_BOUNDS;
}

        /*    API FUNCTIONS    */


/* 
 *  Check cursor function
 * 
 *          p: packet data structure, same as the one found in snort.
 * cursorInfo: data defined in the detection plugin for this rule cursor option
 *     cursor: current position within buffer
 *
 * Returns: 
 *    > 0 : match found
 *    = 0 : no match found
 *    < 0 : error
 *
 * Predefined constants: 
 *    (see sf_snort_plugin_api.h for more values)
 *    CURSOR_IN_BOUNDS     -  if content specifier is found within buffer 
 *    CURSOR_OUT_OF_BOUNDS -  if content specifier is not found within buffer 
 * 
 * Notes:
 *   Since we are checking the cursor position within a buffer, relativity is assumed.
 *     To check absolute position within a buffer, a NULL pointer can be passed in.
 *     In this case, offset will be checked from the start of the given buffer.
 *
 *   Currently support:
 *    options:
 *      offset
 *    buffers:
 *      normalized(alt-decode)
 *      raw
 *      uri
 *      
 */
ENGINE_LINKAGE int checkCursor(void *p, CursorInfo* cursorInfo, const u_int8_t *cursor)
{
    return checkCursorInternal(p, cursorInfo->flags, cursorInfo->offset, cursor);
}

/* 
 *  Set cursor function
 * 
 *          p: packet data structure, same as the one found in snort.
 * cursorInfo: data defined in the detection plugin for this rule cursor option
 *     cursor: updated to point to offset bytes after the buffer start
 *
 * Returns: 
 *    > 0 : match found
 *    = 0 : no match found
 *    < 0 : error
 *
 * Predefined constants: 
 *    (see sf_snort_plugin_api.h for more values)
 *    CURSOR_IN_BOUNDS     -  if content specifier is found within buffer 
 *    CURSOR_OUT_OF_BOUNDS -  if content specifier is not found within buffer 
 * 
 * Notes:
 *
 *   Currently support:
 *    options:
 *      offset
 *    buffers:
 *      normalized(alt-decode)
 *      raw
 *      uri
 *      
 */
ENGINE_LINKAGE int setCursor(void *p, CursorInfo* cursorInfo, const u_int8_t **cursor)
{
    return setCursorInternal(p, cursorInfo->flags, cursorInfo->offset, cursor);
}

ENGINE_LINKAGE void setTempCursor(const u_int8_t **temp_cursor, const u_int8_t **cursor)
{
    *temp_cursor = *cursor;
}

ENGINE_LINKAGE void revertTempCursor(const u_int8_t **temp_cursor, const u_int8_t **cursor)
{
    *cursor = *temp_cursor;
}

/* 
 *  Check flow function
 * 
 *          p: packet data structure, same as the one found in snort.
 *  flowFlags: data defined in the detection plugin for this rule option
 *
 * Returns: 
 *    > 0 : match found
 *    = 0 : no match found
 *
 * Predefined constants: 
 *    (see sf_snort_plugin_api.h for more values)
 *    RULE_MATCH   -  if packet flow matches rule
 *    RULE_NOMATCH -  if packet flow does not match rule 
 * 
 */
ENGINE_LINKAGE int checkFlow(void *p, FlowFlags *flowFlags)
{
    SFSnortPacket *sp = (SFSnortPacket *) p;

    if ((sp->flags & (flowFlags->flags & 0xFF)) != flowFlags->flags)
        return RULE_NOMATCH;

    if ((flowFlags->flags & FLOW_ONLY_REASSMBLED) &&
        !(sp->flags & FLAG_REBUILT_STREAM))
        return RULE_NOMATCH;

    if ((flowFlags->flags & FLOW_IGNORE_REASSEMBLED) &&
        (sp->flags & FLAG_REBUILT_STREAM))
        return RULE_NOMATCH;

    return RULE_MATCH;
}

/* 
 *  Process flowbits function
 * 
 *          p: packet data structure, same as the one found in snort.
 *   flowBits: data defined in the detection plugin for this rule option
 *
 * Returns: 
 *    > 0 : match found
 *    = 0 : no match found
 *
 * Predefined constants: 
 *    (see sf_snort_plugin_api.h for more values)
 *    RULE_MATCH   -  if flowbit operation succeeded
 *    RULE_NOMATCH -  if flowbit operation failed 
 * 
 */
ENGINE_LINKAGE int processFlowbits(void *p, FlowBitsInfo *flowBits)
{
    /* flowbitCheck returns non-zero if the flow bit operation succeeded. */
    if (_ded.flowbitCheck(p, flowBits->operation, flowBits->id))
        return RULE_MATCH;

    return RULE_NOMATCH;

}

/* 
 *  Detect ASN1 function
 * 
 *          p: packet data structure, same as the one found in snort.
 *       asn1: data defined in the detection plugin for this rule option
 *     cursor: current position within buffer
 *
 * Returns: 
 *    > 0 : match found
 *    = 0 : no match found
 *
 * Predefined constants: 
 *    (see sf_snort_plugin_api.h for more values)
 *    RULE_MATCH   -  if asn1 specifier is found within buffer 
 *    RULE_NOMATCH -  if asn1 specifier is not found within buffer 
 * 
 */
ENGINE_LINKAGE int detectAsn1(void *p, Asn1Context* asn1, const u_int8_t *cursor)
{
    /* asn1Detect returns non-zero if the options matched. */
    if (_ded.asn1Detect(p, (void *) asn1, cursor))
        return RULE_MATCH;

    return RULE_NOMATCH;
}

/* 
 *  Store Rule Specific session data
 *  
 *          p: packet data structure, same as the one found in snort.
 *          rule_data: data to store in the session
 *
 * Returns: 
 *    nothing
 *
 */
ENGINE_LINKAGE void storeRuleData(void *p, void *rule_data)
{
    _ded.setRuleData(p, rule_data); 
}

/* 
 *  Retrieve Rule Specific session data
 * 
 *          p: packet data structure, same as the one found in snort.
 *
 * Returns: 
 *    pointer to rule specific session data, NULL if none available
 *
 */
ENGINE_LINKAGE void *getRuleData(void *p)