1 /*
2 * Copyright (c) 2013 The TCPDUMP project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
15 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
16 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
17 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
18 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
20 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
21 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
24 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 * POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 /* \summary: ZeroMQ Message Transport Protocol (ZMTP) printer */
29
30 #ifdef HAVE_CONFIG_H
31 #include <config.h>
32 #endif
33
34 #include "netdissect-stdinc.h"
35
36 #include "netdissect.h"
37 #include "extract.h"
38
39
40 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
41 * hex and ASCII under a single "-v" flag.
42 */
43 #define VBYTES 128
44
45 /*
46 * Below is an excerpt from the "13/ZMTP" specification:
47 *
48 * A ZMTP message consists of 1 or more frames.
49 *
50 * A ZMTP frame consists of a length, followed by a flags field and a frame
51 * body of (length - 1) octets. Note: the length includes the flags field, so
52 * an empty frame has a length of 1.
53 *
54 * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
55 * as a single octet. The minimum valid length of a frame is 1 octet, thus a
56 * length of 0 is invalid and such frames SHOULD be discarded silently.
57 *
58 * For frames with lengths of 255 and greater, the length SHALL BE encoded as
59 * a single octet with the value 255, followed by the length encoded as a
60 * 64-bit unsigned integer in network byte order. For frames with lengths of
61 * 1 to 254 octets this encoding MAY be also used.
62 *
63 * The flags field consists of a single octet containing various control
64 * flags. Bit 0 is the least significant bit.
65 *
66 * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
67 * are no more frames to follow. A value of 1 indicates that more frames
68 * will follow. On messages consisting of a single frame the MORE flag MUST
69 * be 0.
70 *
71 * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
72 * zero.
73 */
74
75 static const u_char *
zmtp1_print_frame(netdissect_options * ndo,const u_char * cp,const u_char * ep)76 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
77 {
78 uint64_t body_len_declared, body_len_captured, header_len;
79 uint8_t flags;
80
81 ND_PRINT("\n\t");
82
83 if (GET_U_1(cp) != 0xFF) { /* length/0xFF */
84 header_len = 1; /* length */
85 body_len_declared = GET_U_1(cp);
86 ND_PRINT(" frame flags+body (8-bit) length %" PRIu64, body_len_declared);
87 } else {
88 header_len = 1 + 8; /* 0xFF, length */
89 ND_PRINT(" frame flags+body (64-bit) length");
90 ND_TCHECK_LEN(cp, header_len); /* 0xFF, length */
91 body_len_declared = GET_BE_U_8(cp + 1);
92 ND_PRINT(" %" PRIu64, body_len_declared);
93 }
94 if (body_len_declared == 0)
95 return cp + header_len; /* skip to the next frame */
96 ND_TCHECK_LEN(cp, header_len + 1); /* ..., flags */
97 flags = GET_U_1(cp + header_len);
98
99 body_len_captured = ep - cp - header_len;
100 if (body_len_declared > body_len_captured)
101 ND_PRINT(" (%" PRIu64 " captured)", body_len_captured);
102 ND_PRINT(", flags 0x%02x", flags);
103
104 if (ndo->ndo_vflag) {
105 uint64_t body_len_printed = ND_MIN(body_len_captured, body_len_declared);
106
107 ND_PRINT(" (%s|%s|%s|%s|%s|%s|%s|%s)",
108 flags & 0x80 ? "MBZ" : "-",
109 flags & 0x40 ? "MBZ" : "-",
110 flags & 0x20 ? "MBZ" : "-",
111 flags & 0x10 ? "MBZ" : "-",
112 flags & 0x08 ? "MBZ" : "-",
113 flags & 0x04 ? "MBZ" : "-",
114 flags & 0x02 ? "MBZ" : "-",
115 flags & 0x01 ? "MORE" : "-");
116
117 if (ndo->ndo_vflag == 1)
118 body_len_printed = ND_MIN(VBYTES + 1, body_len_printed);
119 if (body_len_printed > 1) {
120 ND_PRINT(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1);
121 hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
122 }
123 }
124
125 /*
126 * Do not advance cp by the sum of header_len and body_len_declared
127 * before each offset has successfully passed ND_TCHECK_LEN() as the
128 * sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an
129 * infinite loop.
130 */
131 cp += header_len;
132 ND_TCHECK_LEN(cp, body_len_declared); /* Next frame within the buffer ? */
133 return cp + body_len_declared;
134
135 trunc:
136 nd_trunc_longjmp(ndo);
137 }
138
139 void
zmtp1_print(netdissect_options * ndo,const u_char * cp,u_int len)140 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
141 {
142 const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
143
144 ndo->ndo_protocol = "zmtp1";
145 ND_PRINT(": ZMTP/1.0");
146 while (cp < ep)
147 cp = zmtp1_print_frame(ndo, cp, ep);
148 }
149
150 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
151 * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
152 * follows.
153 *
154 * In order for late joining consumers to be able to identify message
155 * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
156 * in network byte order specifying either the offset of the first message frame
157 * in the datagram or containing the value 0xFFFF if the datagram contains
158 * solely an intermediate part of a larger message.
159 *
160 * Note that offset specifies where the first message begins rather than the
161 * first message part. Thus, if there are trailing message parts at the
162 * beginning of the packet the offset ignores them and points to first initial
163 * message part in the packet.
164 */
165
166 static const u_char *
zmtp1_print_intermediate_part(netdissect_options * ndo,const u_char * cp,const u_int len)167 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
168 {
169 u_int frame_offset;
170 u_int remaining_len;
171
172 frame_offset = GET_BE_U_2(cp);
173 ND_PRINT("\n\t frame offset 0x%04x", frame_offset);
174 cp += 2;
175 remaining_len = ND_BYTES_AVAILABLE_AFTER(cp); /* without the frame length */
176
177 if (frame_offset == 0xFFFF)
178 frame_offset = len - 2; /* always within the declared length */
179 else if (2 + frame_offset > len) {
180 ND_PRINT(" (exceeds datagram declared length)");
181 goto trunc;
182 }
183
184 /* offset within declared length of the datagram */
185 if (frame_offset) {
186 ND_PRINT("\n\t frame intermediate part, %u bytes", frame_offset);
187 if (frame_offset > remaining_len)
188 ND_PRINT(" (%u captured)", remaining_len);
189 if (ndo->ndo_vflag) {
190 u_int len_printed = ND_MIN(frame_offset, remaining_len);
191
192 if (ndo->ndo_vflag == 1)
193 len_printed = ND_MIN(VBYTES, len_printed);
194 if (len_printed > 1) {
195 ND_PRINT(", first %u byte(s):", len_printed);
196 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
197 }
198 }
199 }
200 return cp + frame_offset;
201
202 trunc:
203 nd_trunc_longjmp(ndo);
204 }
205
206 void
zmtp1_datagram_print(netdissect_options * ndo,const u_char * cp,const u_int len)207 zmtp1_datagram_print(netdissect_options *ndo, const u_char *cp, const u_int len)
208 {
209 const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
210
211 ndo->ndo_protocol = "zmtp1";
212 cp = zmtp1_print_intermediate_part(ndo, cp, len);
213 while (cp < ep)
214 cp = zmtp1_print_frame(ndo, cp, ep);
215 }
216