spp_stream4.c

著名的入侵检测系统snort的最新版本的源码

/* $Id$ */

/*
** Copyright (C) 1998-2002 Martin Roesch <[e-mail]>
** Copyright (C) 2003-2005 Sourcefire, Inc.
**
** 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.
*/

/* spp_stream4 
 * 
 * Purpose: Stateful inspection and tcp stream reassembly in Snort
 *
 * Arguments:
 *   
 * Effect:
 *
 * Comments:
 *
 * Any comments?
 *
 */

/*
 * 04 Feb 2005: SAS Updated to handle favor_old and favor_new options.
 *                  favor_new traverses the tree in the opposite
 *                  direction and builds the stream using newer packets.
 *                  Also added checks for:
 *                  - PAWS (Timestamp option is set and 0) on an
 *                  establiahed session and ACK in the packet.  Win32
 *                  uses 0 Timestamp on Syn-only packets.
 *                  - Checks for NULL TCP flags in established session.
 *                  After the TWHS, all packets should have at least
 *                  ACK, RST, or FIN.
 *                  - Checks for overlaps (larger than an option
 *                  specified overlap_limit) in the reassembled stream.
 *                  When the overlap limit is reached, that side of the
 *                  stream is flushed and an evasion alert is raised.  
 *
 * 08 Feb 2005: AJM Update ACK when server sends RST, which enables client
 *                  stream to be reassembled upon flush.
 *                  - Also enable client reassembly upon client RST.
 *                  - Reset session alert count after flushing rebuilt packet.
 *
 * 28 Feb 2005: SAS Update to use hash table to Session storage.  Added new
 *                  files snort_stream_session.{c,h} that contain the sfxhash
 *                  interfaces.
 *                  - Added max_sessions configuration option.  Impacts the
 *                  meaning of memcap in that memcap now only relates to the
 *                  memory consumed by stored packets, not memory for session
 *                  structure.
 *
 * 07 Mar 2005: JRB/SAS Add user configurable flushpoints.  Added options:
 *                  flush_behavior, flush_base, flush_seed, flush_range to
 *                  stream4_reassemble preproc config.
 *
 * 31 Mar 2005: SAS Added server_inspect_limit option to limit the
 *                  amount of data that goes through rules inspection on
 *                  the server side.  The counter is reset when a client
 *                  packet is seen (ie, a request).
 */

/*  I N C L U D E S  ************************************************/

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

#define _STREAM4_INTERNAL_USAGE_ONLY_

#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#ifndef WIN32
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#endif /* WIN32 */
#include <time.h>
#include <rpc/types.h>

#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif

#include "bounds.h"
#include "decode.h"
#include "event.h"
#include "debug.h"
#include "util.h"
#include "plugbase.h"
#include "parser.h"
#include "mstring.h"
#include "checksum.h"
#include "log.h"
#include "generators.h"
#include "detect.h"
#include "perf.h"
#include "timersub.h"
#include "snort.h"
#include "stream.h"
#include "spp_stream4.h"
#include "event_queue.h"
#include "inline.h"
#include "sfsnprintfappend.h"

#include "snort_stream4_session.h"
#include "snort_stream4_udp.h"

#include "stream_ignore.h"
#include "stream_api.h"

#include "flow.h" /* For flowbits, now handled by Stream API */

#include "profiler.h"

/*  D E F I N E S  **************************************************/

/* normal TCP states */
#define CLOSED       0
#define LISTEN       1
#define SYN_RCVD     2
#define SYN_SENT     3
#define ESTABLISHED  4
#define CLOSE_WAIT   5
#define LAST_ACK     6
#define FIN_WAIT_1   7
#define CLOSING      8
#define FIN_WAIT_2   9
#define TIME_WAIT   10

/* extended states for fun stuff */
#define NMAP_FINGERPRINT_2S         30
#define NMAP_FINGERPRINT_NULL       31
#define NMAP_FINGERPRINT_UPSF       32
#define NMAP_FINGERPRINT_ZERO_ACK   33

#define ACTION_NOTHING                  0x00000000
#define ACTION_FLUSH_SERVER_STREAM      0x00000001
#define ACTION_FLUSH_CLIENT_STREAM      0x00000002
#define ACTION_DROP_SESSION             0x00000004
#define ACTION_ACK_SERVER_DATA          0x00000008
#define ACTION_ACK_CLIENT_DATA          0x00000010
#define ACTION_DATA_ON_SYN              0x00000020
#define ACTION_SET_SERVER_ISN           0x00000040
#define ACTION_COMPLETE_TWH             0x00000080
#define ACTION_ALERT_NMAP_FINGERPRINT   0x00000100
#define ACTION_INC_PORT                 0x00000200

#define PRUNE_QUANTA    30              /* seconds to timeout a session */
#define STREAM4_MEMORY_CAP     8388608  /* 8MB */
#define STREAM4_MAX_SESSIONS   8192     /* 8k */
#define STREAM4_CLEANUP   5             /* Cleanup 5 sessions at a time */
#define STREAM4_CACHE_PERCENT 0.1       /* Or cleanup 0.1 % sessions at a time */
#define STREAM4_TTL_LIMIT 5             /* default for TTL Limit */
#define DEFAULT_STREAM_TRACKERS 256000  /* 256k sessions by default */

#define STATS_HUMAN_READABLE   1
#define STATS_MACHINE_READABLE 2
#define STATS_BINARY           3

#define STATS_MAGIC  0xDEAD029A   /* magic for the binary stats file */

#define REVERSE     0
#define NO_REVERSE  1

#define ENFORCE_STATE_NONE 0
#define ENFORCE_STATE      1
#define ENFORCE_STATE_DROP 2

#define METHOD_FAVOR_NEW  0x01
#define METHOD_FAVOR_OLD  0x02

/* # of packets that we accept on an unestab conn */
#define UNESTABLISHED_MAX_PCOUNT 300

/* what pcap can hold is how this limit comes about -- cmg */
#define MAX_STREAM_SIZE (IP_MAXPACKET - IP_HEADER_LEN - TCP_HEADER_LEN - ETHERNET_HEADER_LEN) 

/* Macros to deal with sequence numbers - p810 TCP Illustrated vol 2 */
#define SEQ_LT(a,b)  ((int)((a) - (b)) <  0)
#define SEQ_LEQ(a,b) ((int)((a) - (b)) <= 0)
#define SEQ_GT(a,b)  ((int)((a) - (b)) >  0)
#define SEQ_GEQ(a,b) ((int)((a) - (b)) >= 0)
#define SEQ_EQ(a,b)  ((int)((a) - (b)) == 0)

#define NO_CHK_SEQ  0
#define CHK_SEQ     1


/* these are needed in snort versions before 2.0build something */
#ifndef SNORT_20
extern char *file_name;
extern int *file_line;
#endif /* SNORT_20 */

/* values for the smartbits detector/self perservation */
#define SELF_PRES_THRESHOLD        50
#define SELF_PRES_PERIOD           90

#define SUSPEND_THRESHOLD   200
#define SUSPEND_PERIOD      30

#define OPS_NORMAL              0
#define OPS_SELF_PRESERVATION   1
#define OPS_SUSPEND             2

#define MAXSIZE_IP              65535
#define MAX_TRACKER_AMOUNT      (MAX_STREAM_SIZE + 4000)



/* Support dynamic flush points */
#define FCOUNT 64
#define STREAM4_FLUSH_BASE 512
#define STREAM4_FLUSH_RANGE 1213

#define FLUSH_BEHAVIOR_RANDOM -1
#define FLUSH_BEHAVIOR_DEFAULT 0
#define FLUSH_BEHAVIOR_LARGE 1

/* Old flushpoints, for backward compat.  Use flush_behavior default */
static u_int32_t old_flush_points[FCOUNT] = { 128, 217, 189, 130, 240, 221, 134, 129,
                                               250, 232, 141, 131, 144, 177, 201, 130,
                                               230, 190, 177, 142, 130, 200, 173, 129,
                                               250, 244, 174, 151, 201, 190, 180, 198,
                                               220, 201, 142, 185, 219, 129, 194, 140,
                                               145, 191, 197, 183, 199, 220, 231, 245,
                                               233, 135, 143, 158, 174, 194, 200, 180,
                                               201, 142, 153, 187, 173, 199, 143, 201 };

static u_int32_t new_flush_points[FCOUNT] = { 1280, 2176, 1895, 1303, 2402, 2211, 1340, 1298,
                                              2500, 2320, 1413, 1313, 1444, 1776, 2015, 1305,
                                              2130, 1190, 1377, 1492, 1380, 2100, 1373, 1029,
                                              750, 444, 874, 551, 401, 390, 1801, 1898,
                                              2260, 2601, 642, 485, 619, 929, 794, 340,
                                              445, 1911, 497, 883, 399, 2201, 2431, 2145,
                                              433, 735, 543, 658, 1174, 2042, 1200, 1800,
                                              2015, 1142, 1530, 487, 673, 899, 743, 2101 };

#ifdef DEBUG
static char *state_names[] = { "CLOSED",
                              "LISTEN",
                              "SYN_RCVD",
                              "SYN_SENT",
                              "ESTABLISHED",
                              "CLOSE_WAIT",
                              "LAST_ACK",
                              "FIN_WAIT_1",
                              "CLOSING",
                              "FIN_WAIT_2",
                              "TIME_WAIT"};
#endif

/*  D A T A   S T R U C T U R E S  **********************************/
typedef struct _OverlapData
{
    u_int32_t seq_low;
    u_int32_t seq_hi;

} OverlapData;

typedef struct _BuildData
{
    Stream *stream;
    const u_int8_t *buf;
    u_int32_t total_size;
    /* u_int32_t build_flags; -- reserved for the day when we generate 1 stream event and log the stream */
} BuildData;

typedef struct _BinStats
{
    u_int32_t start_time;
    u_int32_t end_time;
    ip_t      sip;
    ip_t      cip;
    u_int16_t sport;
    u_int16_t cport;
    u_int32_t spackets;
    u_int32_t cpackets;
    u_int32_t sbytes;
    u_int32_t cbytes;
} BinStats;

typedef struct _StatsLog
{
    FILE *fp;
    char *filename;

} StatsLog;

typedef struct _StatsLogHeader
{
    u_int32_t magic;
    u_int32_t version_major;
    u_int32_t version_minor;
    u_int32_t timezone;
} StatsLogHeader;

typedef struct _S4Emergency
{
    long end_time;
    char old_reassemble_client;
    char old_reassemble_server;
    char old_reassembly_alerts;
    int old_assurance_mode;
    char old_stateful_mode;
    u_int32_t new_session_count;
    int status;
} S4Emergency;

typedef struct _StreamKey
{
    u_int32_t sip;
    u_int32_t cip;
    u_int16_t sport;
    u_int16_t cport;
} STREAM_KEY;

typedef Session *SessionPtr;

StatsLog *stats_log;

u_int32_t safe_alloc_faults;

/* we keep a stream packet queued up and ready to go for reassembly */
Packet *stream_pkt;

/*  G L O B A L S  **************************************************/

extern int do_detect, do_detect_content;
extern OptTreeNode *otn_tmp;

/* external globals from rules.c */
FILE *session_log;
Stream4Data s4data;
u_int32_t stream4_memory_usage;
u_int32_t ps_memory_usage;

/* stream4 emergency mode counters... */
S4Emergency s4_emergency;

/* List of Dynamic flushpoints */
u_int32_t flush_points[FCOUNT];

#ifdef PERF_PROFILING
PreprocStats stream4PerfStats;
PreprocStats stream4InsertPerfStats;
PreprocStats stream4BuildPerfStats;
PreprocStats stream4NewSessPerfStats;
PreprocStats stream4LUSessPerfStats;
PreprocStats stream4StatePerfStats;
PreprocStats stream4StateAsyncPerfStats;
PreprocStats stream4ActionPerfStats;
PreprocStats stream4ActionAsyncPerfStats;
PreprocStats stream4PrunePerfStats;
PreprocStats stream4FlushPerfStats;
PreprocStats stream4ProcessRebuiltPerfStats;
#endif

/*  P R O T O T Y P E S  ********************************************/
void *SafeAlloc(unsigned long, int, Session *);
void ParseStream4Args(char *);
void Stream4InitReassembler(char *);
void Stream4InitExternalOptions(char *);
void ReassembleStream4(Packet *, void *);
Session *CreateNewSession(Packet *, u_int32_t, u_int32_t);
void DropSession(Session *);
void DeleteSession(Session *, u_int32_t, char flag);
void DeleteSpd(StreamPacketData **);
int GetDirection(Session *, Packet *);
static int s4_shutdown = 0;