suricata
decode-tcp.h
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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 #define TCP_OPT_TFO 0x22 /* TCP Fast Open */
55 #define TCP_OPT_EXP1 0xfd /* Experimental, could be TFO */
56 #define TCP_OPT_EXP2 0xfe /* Experimental, could be TFO */
57 
58 #define TCP_OPT_SACKOK_LEN 2
59 #define TCP_OPT_WS_LEN 3
60 #define TCP_OPT_TS_LEN 10
61 #define TCP_OPT_MSS_LEN 4
62 #define TCP_OPT_SACK_MIN_LEN 10 /* hdr 2, 1 pair 8 = 10 */
63 #define TCP_OPT_SACK_MAX_LEN 34 /* hdr 2, 4 pair 32= 34 */
64 #define TCP_OPT_TFO_MIN_LEN 6 /* kind, len, 6 */
65 #define TCP_OPT_TFO_MAX_LEN 20 /* kind, len, 18 */
66 
67 /** Max valid wscale value. */
68 #define TCP_WSCALE_MAX 14
69 
70 #define TCP_GET_RAW_OFFSET(tcph) (((tcph)->th_offx2 & 0xf0) >> 4)
71 #define TCP_GET_RAW_X2(tcph) (unsigned char)((tcph)->th_offx2 & 0x0f)
72 #define TCP_GET_RAW_SRC_PORT(tcph) SCNtohs((tcph)->th_sport)
73 #define TCP_GET_RAW_DST_PORT(tcph) SCNtohs((tcph)->th_dport)
74 
75 #define TCP_SET_RAW_TCP_OFFSET(tcph, value) ((tcph)->th_offx2 = (unsigned char)(((tcph)->th_offx2 & 0x0f) | (value << 4)))
76 #define TCP_SET_RAW_TCP_X2(tcph, value) ((tcph)->th_offx2 = (unsigned char)(((tcph)->th_offx2 & 0xf0) | (value & 0x0f)))
77 
78 #define TCP_GET_RAW_SEQ(tcph) SCNtohl((tcph)->th_seq)
79 #define TCP_GET_RAW_ACK(tcph) SCNtohl((tcph)->th_ack)
80 
81 #define TCP_GET_RAW_WINDOW(tcph) SCNtohs((tcph)->th_win)
82 #define TCP_GET_RAW_URG_POINTER(tcph) SCNtohs((tcph)->th_urp)
83 #define TCP_GET_RAW_SUM(tcph) SCNtohs((tcph)->th_sum)
84 
85 /** macro for getting the first timestamp from the packet in host order */
86 #define TCP_GET_TSVAL(p) ((p)->tcpvars.ts_val)
87 
88 /** macro for getting the second timestamp from the packet in host order. */
89 #define TCP_GET_TSECR(p) ((p)->tcpvars.ts_ecr)
90 
91 #define TCP_HAS_WSCALE(p) ((p)->tcpvars.ws.type == TCP_OPT_WS)
92 #define TCP_HAS_SACK(p) ((p)->tcpvars.sack.type == TCP_OPT_SACK)
93 #define TCP_HAS_SACKOK(p) ((p)->tcpvars.sackok.type == TCP_OPT_SACKOK)
94 #define TCP_HAS_TS(p) ((p)->tcpvars.ts_set == TRUE)
95 #define TCP_HAS_MSS(p) ((p)->tcpvars.mss.type == TCP_OPT_MSS)
96 #define TCP_HAS_TFO(p) ((p)->tcpvars.tfo.type == TCP_OPT_TFO)
97 
98 /** macro for getting the wscale from the packet. */
99 #define TCP_GET_WSCALE(p) (TCP_HAS_WSCALE((p)) ? \
100  (((*(uint8_t *)(p)->tcpvars.ws.data) <= TCP_WSCALE_MAX) ? \
101  (*(uint8_t *)((p)->tcpvars.ws.data)) : 0) : 0)
102 
103 #define TCP_GET_SACKOK(p) (TCP_HAS_SACKOK((p)) ? 1 : 0)
104 #define TCP_GET_SACK_PTR(p) TCP_HAS_SACK((p)) ? (p)->tcpvars.sack.data : NULL
105 #define TCP_GET_SACK_CNT(p) (TCP_HAS_SACK((p)) ? (((p)->tcpvars.sack.len - 2) / 8) : 0)
106 #define TCP_GET_MSS(p) SCNtohs(*(uint16_t *)((p)->tcpvars.mss.data))
107 
108 #define TCP_GET_OFFSET(p) TCP_GET_RAW_OFFSET((p)->tcph)
109 #define TCP_GET_X2(p) TCP_GET_RAW_X2((p)->tcph)
110 #define TCP_GET_HLEN(p) (TCP_GET_OFFSET((p)) << 2)
111 #define TCP_GET_SRC_PORT(p) TCP_GET_RAW_SRC_PORT((p)->tcph)
112 #define TCP_GET_DST_PORT(p) TCP_GET_RAW_DST_PORT((p)->tcph)
113 #define TCP_GET_SEQ(p) TCP_GET_RAW_SEQ((p)->tcph)
114 #define TCP_GET_ACK(p) TCP_GET_RAW_ACK((p)->tcph)
115 #define TCP_GET_WINDOW(p) TCP_GET_RAW_WINDOW((p)->tcph)
116 #define TCP_GET_URG_POINTER(p) TCP_GET_RAW_URG_POINTER((p)->tcph)
117 #define TCP_GET_SUM(p) TCP_GET_RAW_SUM((p)->tcph)
118 #define TCP_GET_FLAGS(p) (p)->tcph->th_flags
119 
120 #define TCP_ISSET_FLAG_FIN(p) ((p)->tcph->th_flags & TH_FIN)
121 #define TCP_ISSET_FLAG_SYN(p) ((p)->tcph->th_flags & TH_SYN)
122 #define TCP_ISSET_FLAG_RST(p) ((p)->tcph->th_flags & TH_RST)
123 #define TCP_ISSET_FLAG_PUSH(p) ((p)->tcph->th_flags & TH_PUSH)
124 #define TCP_ISSET_FLAG_ACK(p) ((p)->tcph->th_flags & TH_ACK)
125 #define TCP_ISSET_FLAG_URG(p) ((p)->tcph->th_flags & TH_URG)
126 #define TCP_ISSET_FLAG_RES2(p) ((p)->tcph->th_flags & TH_RES2)
127 #define TCP_ISSET_FLAG_RES1(p) ((p)->tcph->th_flags & TH_RES1)
128 
129 typedef struct TCPOpt_ {
130  uint8_t type;
131  uint8_t len;
132  const uint8_t *data;
133 } TCPOpt;
134 
135 typedef struct TCPOptSackRecord_ {
136  uint32_t le; /**< left edge, network order */
137  uint32_t re; /**< right edge, network order */
139 
140 typedef struct TCPHdr_
141 {
142  uint16_t th_sport; /**< source port */
143  uint16_t th_dport; /**< destination port */
144  uint32_t th_seq; /**< sequence number */
145  uint32_t th_ack; /**< acknowledgement number */
146  uint8_t th_offx2; /**< offset and reserved */
147  uint8_t th_flags; /**< pkt flags */
148  uint16_t th_win; /**< pkt window */
149  uint16_t th_sum; /**< checksum */
150  uint16_t th_urp; /**< urgent pointer */
151 } __attribute__((__packed__)) TCPHdr;
152 
153 typedef struct TCPVars_
154 {
155  /* commonly used and needed opts */
156  _Bool ts_set;
157  uint32_t ts_val; /* host-order */
158  uint32_t ts_ecr; /* host-order */
163  TCPOpt tfo; /* tcp fast open */
164 } TCPVars;
165 
166 #define CLEAR_TCP_PACKET(p) { \
167  (p)->level4_comp_csum = -1; \
168  PACKET_CLEAR_L4VARS((p)); \
169  (p)->tcph = NULL; \
170 }
171 
172 void DecodeTCPRegisterTests(void);
173 
174 /** -------- Inline functions ------- */
175 static inline uint16_t TCPChecksum(uint16_t *, uint16_t *, uint16_t, uint16_t);
176 static inline uint16_t TCPV6Checksum(uint16_t *, uint16_t *, uint16_t, uint16_t);
177 
178 /**
179  * \brief Calculate or validate the checksum for the TCP packet
180  *
181  * \param shdr Pointer to source address field from the IP packet. Used as a
182  * part of the pseudoheader for computing the checksum
183  * \param pkt Pointer to the start of the TCP packet
184  * \param tlen Total length of the TCP packet(header + payload)
185  * \param init The current checksum if validating, 0 if generating.
186  *
187  * \retval csum For validation 0 will be returned for success, for calculation
188  * this will be the checksum.
189  */
190 static inline uint16_t TCPChecksum(uint16_t *shdr, uint16_t *pkt,
191  uint16_t tlen, uint16_t init)
192 {
193  uint16_t pad = 0;
194  uint32_t csum = init;
195 
196  csum += shdr[0] + shdr[1] + shdr[2] + shdr[3] + htons(6) + htons(tlen);
197 
198  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
199  pkt[7] + pkt[9];
200 
201  tlen -= 20;
202  pkt += 10;
203 
204  while (tlen >= 32) {
205  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
206  pkt[7] +
207  pkt[8] +
208  pkt[9] + pkt[10] + pkt[11] + pkt[12] + pkt[13] +
209  pkt[14] + pkt[15];
210  tlen -= 32;
211  pkt += 16;
212  }
213 
214  while(tlen >= 8) {
215  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3];
216  tlen -= 8;
217  pkt += 4;
218  }
219 
220  while(tlen >= 4) {
221  csum += pkt[0] + pkt[1];
222  tlen -= 4;
223  pkt += 2;
224  }
225 
226  while (tlen > 1) {
227  csum += pkt[0];
228  pkt += 1;
229  tlen -= 2;
230  }
231 
232  if (tlen == 1) {
233  *(uint8_t *)(&pad) = (*(uint8_t *)pkt);
234  csum += pad;
235  }
236 
237  csum = (csum >> 16) + (csum & 0x0000FFFF);
238  csum += (csum >> 16);
239 
240  return (uint16_t)~csum;
241 }
242 
243 /**
244  * \brief Calculate or validate the checksum for the TCP packet
245  *
246  * \param shdr Pointer to source address field from the IPV6 packet. Used as a
247  * part of the psuedoheader for computing the checksum
248  * \param pkt Pointer to the start of the TCP packet
249  * \param tlen Total length of the TCP packet(header + payload)
250  * \param init The current checksum if validating, 0 if generating.
251  *
252  * \retval csum For validation 0 will be returned for success, for calculation
253  * this will be the checksum.
254  */
255 static inline uint16_t TCPV6Checksum(uint16_t *shdr, uint16_t *pkt,
256  uint16_t tlen, uint16_t init)
257 {
258  uint16_t pad = 0;
259  uint32_t csum = init;
260 
261  csum += shdr[0] + shdr[1] + shdr[2] + shdr[3] + shdr[4] + shdr[5] +
262  shdr[6] + shdr[7] + shdr[8] + shdr[9] + shdr[10] + shdr[11] +
263  shdr[12] + shdr[13] + shdr[14] + shdr[15] + htons(6) + htons(tlen);
264 
265  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
266  pkt[7] + pkt[9];
267 
268  tlen -= 20;
269  pkt += 10;
270 
271  while (tlen >= 32) {
272  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3] + pkt[4] + pkt[5] + pkt[6] +
273  pkt[7] + pkt[8] + pkt[9] + pkt[10] + pkt[11] + pkt[12] + pkt[13] +
274  pkt[14] + pkt[15];
275  tlen -= 32;
276  pkt += 16;
277  }
278 
279  while(tlen >= 8) {
280  csum += pkt[0] + pkt[1] + pkt[2] + pkt[3];
281  tlen -= 8;
282  pkt += 4;
283  }
284 
285  while(tlen >= 4) {
286  csum += pkt[0] + pkt[1];
287  tlen -= 4;
288  pkt += 2;
289  }
290 
291  while (tlen > 1) {
292  csum += pkt[0];
293  pkt += 1;
294  tlen -= 2;
295  }
296 
297  if (tlen == 1) {
298  *(uint8_t *)(&pad) = (*(uint8_t *)pkt);
299  csum += pad;
300  }
301 
302  csum = (csum >> 16) + (csum & 0x0000FFFF);
303  csum += (csum >> 16);
304 
305  return (uint16_t)~csum;
306 }
307 
308 
309 #endif /* __DECODE_TCP_H__ */
310 
uint32_t ts_ecr
Definition: decode-tcp.h:158
uint16_t th_win
Definition: decode-tcp.h:148
void DecodeTCPRegisterTests(void)
Definition: decode-tcp.c:552
uint8_t len
Definition: decode-tcp.h:131
const uint8_t * data
Definition: decode-tcp.h:132
uint8_t th_flags
Definition: decode-tcp.h:147
TCPOpt tfo
Definition: decode-tcp.h:163
uint16_t th_sum
Definition: decode-tcp.h:149
struct TCPVars_ TCPVars
uint16_t pad
uint32_t ts_val
Definition: decode-tcp.h:157
TCPOpt sackok
Definition: decode-tcp.h:160
uint8_t type
Definition: decode-tcp.h:130
uint16_t th_dport
Definition: decode-tcp.h:143
struct TCPOpt_ TCPOpt
uint8_t th_offx2
Definition: decode-tcp.h:146
uint16_t th_urp
Definition: decode-tcp.h:150
TCPOpt mss
Definition: decode-tcp.h:162
struct TCPOptSackRecord_ TCPOptSackRecord
uint16_t th_sport
Definition: decode-tcp.h:142
_Bool ts_set
Definition: decode-tcp.h:156
TCPOpt sack
Definition: decode-tcp.h:159
uint32_t th_ack
Definition: decode-tcp.h:145
uint32_t th_seq
Definition: decode-tcp.h:144
struct TCPHdr_ __attribute__((__packed__)) TCPHdr
DNP3 link header.
TCPOpt ws
Definition: decode-tcp.h:161