suricata
decode-tcp.h
Go to the documentation of this file.
1 /* Copyright (C) 2007-2013 Open Information Security Foundation
2  *
3  * You can copy, redistribute or modify this Program under the terms of
4  * the GNU General Public License version 2 as published by the Free
5  * Software Foundation.
6  *
7  * This program is distributed in the hope that it will be useful,
8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10  * GNU General Public License for more details.
11  *
12  * You should have received a copy of the GNU General Public License
13  * version 2 along with this program; if not, write to the Free Software
14  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
15  * 02110-1301, USA.
16  */
17 
18 /**
19  * \file
20  *
21  * \author Victor Julien <victor@inliniac.net>
22  * \todo RAW* macro's should be returning the raw value, not the host order
23  */
24 
25 #ifndef __DECODE_TCP_H__
26 #define __DECODE_TCP_H__
27 
28 #define TCP_HEADER_LEN 20
29 #define TCP_OPTLENMAX 40
30 #define TCP_OPTMAX 20 /* every opt is at least 2 bytes
31  * (type + len), except EOL and NOP */
32 
33 /* TCP flags */
34 
35 #define TH_FIN 0x01
36 #define TH_SYN 0x02
37 #define TH_RST 0x04
38 #define TH_PUSH 0x08
39 #define TH_ACK 0x10
40 #define TH_URG 0x20
41 /** Establish a new connection reducing window */
42 #define TH_ECN 0x40
43 /** Echo Congestion flag */
44 #define TH_CWR 0x80
45 
46 /* tcp option codes */
47 #define TCP_OPT_EOL 0x00
48 #define TCP_OPT_NOP 0x01
49 #define TCP_OPT_MSS 0x02
50 #define TCP_OPT_WS 0x03
51 #define TCP_OPT_SACKOK 0x04
52 #define TCP_OPT_SACK 0x05
53 #define TCP_OPT_TS 0x08
54 
55 #define TCP_OPT_SACKOK_LEN 2
56 #define TCP_OPT_WS_LEN 3
57 #define TCP_OPT_TS_LEN 10
58 #define TCP_OPT_MSS_LEN 4
59 #define TCP_OPT_SACK_MIN_LEN 10 /* hdr 2, 1 pair 8 = 10 */
60 #define TCP_OPT_SACK_MAX_LEN 34 /* hdr 2, 4 pair 32= 34 */
61 
62 /** Max valid wscale value. */
63 #define TCP_WSCALE_MAX 14
64 
65 #define TCP_GET_RAW_OFFSET(tcph) (((tcph)->th_offx2 & 0xf0) >> 4)
66 #define TCP_GET_RAW_X2(tcph) (unsigned char)((tcph)->th_offx2 & 0x0f)
67 #define TCP_GET_RAW_SRC_PORT(tcph) SCNtohs((tcph)->th_sport)
68 #define TCP_GET_RAW_DST_PORT(tcph) SCNtohs((tcph)->th_dport)
69 
70 #define TCP_SET_RAW_TCP_OFFSET(tcph, value) ((tcph)->th_offx2 = (unsigned char)(((tcph)->th_offx2 & 0x0f) | (value << 4)))
71 #define TCP_SET_RAW_TCP_X2(tcph, value) ((tcph)->th_offx2 = (unsigned char)(((tcph)->th_offx2 & 0xf0) | (value & 0x0f)))
72 
73 #define TCP_GET_RAW_SEQ(tcph) SCNtohl((tcph)->th_seq)
74 #define TCP_GET_RAW_ACK(tcph) SCNtohl((tcph)->th_ack)
75 
76 #define TCP_GET_RAW_WINDOW(tcph) SCNtohs((tcph)->th_win)
77 #define TCP_GET_RAW_URG_POINTER(tcph) SCNtohs((tcph)->th_urp)
78 #define TCP_GET_RAW_SUM(tcph) SCNtohs((tcph)->th_sum)
79 
80 /** macro for getting the first timestamp from the packet in host order */
81 #define TCP_GET_TSVAL(p) ((p)->tcpvars.ts_val)
82 
83 /** macro for getting the second timestamp from the packet in host order. */
84 #define TCP_GET_TSECR(p) ((p)->tcpvars.ts_ecr)
85 
86 #define TCP_HAS_WSCALE(p) ((p)->tcpvars.ws.type == TCP_OPT_WS)
87 #define TCP_HAS_SACK(p) ((p)->tcpvars.sack.type == TCP_OPT_SACK)
88 #define TCP_HAS_SACKOK(p) ((p)->tcpvars.sackok.type == TCP_OPT_SACKOK)
89 #define TCP_HAS_TS(p) ((p)->tcpvars.ts_set == TRUE)
90 #define TCP_HAS_MSS(p) ((p)->tcpvars.mss.type == TCP_OPT_MSS)
91 
92 /** macro for getting the wscale from the packet. */
93 #define TCP_GET_WSCALE(p) (TCP_HAS_WSCALE((p)) ? \
94  (((*(uint8_t *)(p)->tcpvars.ws.data) <= TCP_WSCALE_MAX) ? \
95  (*(uint8_t *)((p)->tcpvars.ws.data)) : 0) : 0)
96 
97 #define TCP_GET_SACKOK(p) (TCP_HAS_SACKOK((p)) ? 1 : 0)
98 #define TCP_GET_SACK_PTR(p) TCP_HAS_SACK((p)) ? (p)->tcpvars.sack.data : NULL
99 #define TCP_GET_SACK_CNT(p) (TCP_HAS_SACK((p)) ? (((p)->tcpvars.sack.len - 2) / 8) : 0)
100 
101 #define TCP_GET_OFFSET(p) TCP_GET_RAW_OFFSET((p)->tcph)
102 #define TCP_GET_X2(p) TCP_GET_RAW_X2((p)->tcph)
103 #define TCP_GET_HLEN(p) (TCP_GET_OFFSET((p)) << 2)
104 #define TCP_GET_SRC_PORT(p) TCP_GET_RAW_SRC_PORT((p)->tcph)
105 #define TCP_GET_DST_PORT(p) TCP_GET_RAW_DST_PORT((p)->tcph)
106 #define TCP_GET_SEQ(p) TCP_GET_RAW_SEQ((p)->tcph)
107 #define TCP_GET_ACK(p) TCP_GET_RAW_ACK((p)->tcph)
108 #define TCP_GET_WINDOW(p) TCP_GET_RAW_WINDOW((p)->tcph)
109 #define TCP_GET_URG_POINTER(p) TCP_GET_RAW_URG_POINTER((p)->tcph)
110 #define TCP_GET_SUM(p) TCP_GET_RAW_SUM((p)->tcph)
111 #define TCP_GET_FLAGS(p) (p)->tcph->th_flags
112 
113 #define TCP_ISSET_FLAG_FIN(p) ((p)->tcph->th_flags & TH_FIN)
114 #define TCP_ISSET_FLAG_SYN(p) ((p)->tcph->th_flags & TH_SYN)
115 #define TCP_ISSET_FLAG_RST(p) ((p)->tcph->th_flags & TH_RST)
116 #define TCP_ISSET_FLAG_PUSH(p) ((p)->tcph->th_flags & TH_PUSH)
117 #define TCP_ISSET_FLAG_ACK(p) ((p)->tcph->th_flags & TH_ACK)
118 #define TCP_ISSET_FLAG_URG(p) ((p)->tcph->th_flags & TH_URG)
119 #define TCP_ISSET_FLAG_RES2(p) ((p)->tcph->th_flags & TH_RES2)
120 #define TCP_ISSET_FLAG_RES1(p) ((p)->tcph->th_flags & TH_RES1)
121 
122 typedef struct TCPOpt_ {
123  uint8_t type;
124  uint8_t len;
125  uint8_t *data;
126 } TCPOpt;
127 
128 typedef struct TCPOptSackRecord_ {
129  uint32_t le; /**< left edge, network order */
130  uint32_t re; /**< right edge, network order */
132 
133 typedef struct TCPHdr_
134 {
135  uint16_t th_sport; /**< source port */
136  uint16_t th_dport; /**< destination port */
137  uint32_t th_seq; /**< sequence number */
138  uint32_t th_ack; /**< acknowledgement number */
139  uint8_t th_offx2; /**< offset and reserved */
140  uint8_t th_flags; /**< pkt flags */
141  uint16_t th_win; /**< pkt window */
142  uint16_t th_sum; /**< checksum */
143  uint16_t th_urp; /**< urgent pointer */
144 } __attribute__((__packed__)) TCPHdr;
145 
146 typedef struct TCPVars_
147 {
148  /* commonly used and needed opts */
149  _Bool ts_set;
150  uint32_t ts_val; /* host-order */
151  uint32_t ts_ecr; /* host-order */
156 } TCPVars;
157 
158 #define CLEAR_TCP_PACKET(p) { \
159  (p)->level4_comp_csum = -1; \
160  PACKET_CLEAR_L4VARS((p)); \
161  (p)->tcph = NULL; \
162 }
163 
164 void DecodeTCPRegisterTests(void);
165 
166 /** -------- Inline functions ------- */
167 static inline uint16_t TCPChecksum(uint16_t *, uint16_t *, uint16_t, uint16_t);
168 static inline uint16_t TCPV6Checksum(uint16_t *, uint16_t *, uint16_t, uint16_t);
169 
170 /**
171  * \brief Calculate or validate the checksum for the TCP packet
172  *
173  * \param shdr Pointer to source address field from the IP packet. Used as a
174  * part of the pseudoheader for computing the checksum
175  * \param pkt Pointer to the start of the TCP packet
176  * \param tlen Total length of the TCP packet(header + payload)
177  * \param init The current checksum if validating, 0 if generating.
178  *
179  * \retval csum For validation 0 will be returned for success, for calculation
180  * this will be the checksum.
181  */
182 static inline uint16_t TCPChecksum(uint16_t *shdr, uint16_t *pkt,
183  uint16_t tlen, uint16_t init)
184 {
185  uint16_t pad = 0;
186  uint32_t csum = init;
187 
188  csum += shdr[0] + shdr[1] + shdr[2] + shdr[3] + htons(6) + htons(tlen);
189 
190  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
191  pkt[7] + pkt[9];
192 
193  tlen -= 20;
194  pkt += 10;
195 
196  while (tlen >= 32) {
197  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
198  pkt[7] +
199  pkt[8] +
200  pkt[9] + pkt[10] + pkt[11] + pkt[12] + pkt[13] +
201  pkt[14] + pkt[15];
202  tlen -= 32;
203  pkt += 16;
204  }
205 
206  while(tlen >= 8) {
207  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3];
208  tlen -= 8;
209  pkt += 4;
210  }
211 
212  while(tlen >= 4) {
213  csum += pkt[0] + pkt[1];
214  tlen -= 4;
215  pkt += 2;
216  }
217 
218  while (tlen > 1) {
219  csum += pkt[0];
220  pkt += 1;
221  tlen -= 2;
222  }
223 
224  if (tlen == 1) {
225  *(uint8_t *)(&pad) = (*(uint8_t *)pkt);
226  csum += pad;
227  }
228 
229  csum = (csum >> 16) + (csum & 0x0000FFFF);
230  csum += (csum >> 16);
231 
232  return (uint16_t)~csum;
233 }
234 
235 /**
236  * \brief Calculate or validate the checksum for the TCP packet
237  *
238  * \param shdr Pointer to source address field from the IPV6 packet. Used as a
239  * part of the psuedoheader for computing the checksum
240  * \param pkt Pointer to the start of the TCP packet
241  * \param tlen Total length of the TCP packet(header + payload)
242  * \param init The current checksum if validating, 0 if generating.
243  *
244  * \retval csum For validation 0 will be returned for success, for calculation
245  * this will be the checksum.
246  */
247 static inline uint16_t TCPV6Checksum(uint16_t *shdr, uint16_t *pkt,
248  uint16_t tlen, uint16_t init)
249 {
250  uint16_t pad = 0;
251  uint32_t csum = init;
252 
253  csum += shdr[0] + shdr[1] + shdr[2] + shdr[3] + shdr[4] + shdr[5] +
254  shdr[6] + shdr[7] + shdr[8] + shdr[9] + shdr[10] + shdr[11] +
255  shdr[12] + shdr[13] + shdr[14] + shdr[15] + htons(6) + htons(tlen);
256 
257  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
258  pkt[7] + pkt[9];
259 
260  tlen -= 20;
261  pkt += 10;
262 
263  while (tlen >= 32) {
264  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
265  pkt[7] + pkt[8] + pkt[9] + pkt[10] + pkt[11] + pkt[12] + pkt[13] +
266  pkt[14] + pkt[15];
267  tlen -= 32;
268  pkt += 16;
269  }
270 
271  while(tlen >= 8) {
272  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3];
273  tlen -= 8;
274  pkt += 4;
275  }
276 
277  while(tlen >= 4) {
278  csum += pkt[0] + pkt[1];
279  tlen -= 4;
280  pkt += 2;
281  }
282 
283  while (tlen > 1) {
284  csum += pkt[0];
285  pkt += 1;
286  tlen -= 2;
287  }
288 
289  if (tlen == 1) {
290  *(uint8_t *)(&pad) = (*(uint8_t *)pkt);
291  csum += pad;
292  }
293 
294  csum = (csum >> 16) + (csum & 0x0000FFFF);
295  csum += (csum >> 16);
296 
297  return (uint16_t)~csum;
298 }
299 
300 
301 #endif /* __DECODE_TCP_H__ */
302 
uint32_t ts_ecr
Definition: decode-tcp.h:151
uint16_t th_win
Definition: decode-tcp.h:141
void DecodeTCPRegisterTests(void)
Definition: decode-tcp.c:517
uint8_t len
Definition: decode-tcp.h:124
uint8_t th_flags
Definition: decode-tcp.h:140
uint16_t th_sum
Definition: decode-tcp.h:142
struct TCPVars_ TCPVars
uint16_t pad
uint32_t ts_val
Definition: decode-tcp.h:150
TCPOpt sackok
Definition: decode-tcp.h:153
uint8_t type
Definition: decode-tcp.h:123
uint16_t th_dport
Definition: decode-tcp.h:136
uint8_t * data
Definition: decode-tcp.h:125
struct TCPOpt_ TCPOpt
uint8_t th_offx2
Definition: decode-tcp.h:139
uint16_t th_urp
Definition: decode-tcp.h:143
TCPOpt mss
Definition: decode-tcp.h:155
struct TCPOptSackRecord_ TCPOptSackRecord
uint16_t th_sport
Definition: decode-tcp.h:135
_Bool ts_set
Definition: decode-tcp.h:149
TCPOpt sack
Definition: decode-tcp.h:152
uint32_t th_ack
Definition: decode-tcp.h:138
uint32_t th_seq
Definition: decode-tcp.h:137
struct TCPHdr_ __attribute__((__packed__)) TCPHdr
DNP3 link header.
TCPOpt ws
Definition: decode-tcp.h:154