1 /*
2 * This file implements decoding of ZeroMQ network protocol(s).
3 *
4 *
5 * Copyright (c) 2013 The TCPDUMP project
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
21 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
27 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #ifdef HAVE_CONFIG_H
32 #include "config.h"
33 #endif
34
35 #include <tcpdump-stdinc.h>
36
37 #include <stdio.h>
38
39 #include "interface.h"
40 #include "extract.h"
41
42 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
43 * hex and ASCII under a single "-v" flag.
44 */
45 #define VBYTES 128
46
47 /*
48 * Below is an excerpt from the "13/ZMTP" specification:
49 *
50 * A ZMTP message consists of 1 or more frames.
51 *
52 * A ZMTP frame consists of a length, followed by a flags field and a frame
53 * body of (length - 1) octets. Note: the length includes the flags field, so
54 * an empty frame has a length of 1.
55 *
56 * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
57 * as a single octet. The minimum valid length of a frame is 1 octet, thus a
58 * length of 0 is invalid and such frames SHOULD be discarded silently.
59 *
60 * For frames with lengths of 255 and greater, the length SHALL BE encoded as
61 * a single octet with the value 255, followed by the length encoded as a
62 * 64-bit unsigned integer in network byte order. For frames with lengths of
63 * 1 to 254 octets this encoding MAY be also used.
64 *
65 * The flags field consists of a single octet containing various control
66 * flags. Bit 0 is the least significant bit.
67 *
68 * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
69 * are no more frames to follow. A value of 1 indicates that more frames
70 * will follow. On messages consisting of a single frame the MORE flag MUST
71 * be 0.
72 *
73 * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
74 * zero.
75 */
76
77 static const u_char *
zmtp1_print_frame(const u_char * cp,const u_char * ep)78 zmtp1_print_frame(const u_char *cp, const u_char *ep) {
79 u_int64_t body_len_declared, body_len_captured, header_len;
80 u_int8_t flags;
81
82 printf("\n\t");
83 TCHECK2(*cp, 1); /* length/0xFF */
84
85 if (cp[0] != 0xFF) {
86 header_len = 1; /* length */
87 body_len_declared = cp[0];
88 if (body_len_declared == 0)
89 return cp + header_len; /* skip to next frame */
90 printf(" frame flags+body (8-bit) length %u", cp[0]);
91 TCHECK2(*cp, header_len + 1); /* length, flags */
92 flags = cp[1];
93 } else {
94 header_len = 1 + 8; /* 0xFF, length */
95 printf(" frame flags+body (64-bit) length");
96 TCHECK2(*cp, header_len); /* 0xFF, length */
97 body_len_declared = EXTRACT_64BITS(cp + 1);
98 if (body_len_declared == 0)
99 return cp + header_len; /* skip to next frame */
100 printf(" %" PRIu64, body_len_declared);
101 TCHECK2(*cp, header_len + 1); /* 0xFF, length, flags */
102 flags = cp[9];
103 }
104
105 body_len_captured = ep - cp - header_len;
106 if (body_len_declared > body_len_captured)
107 printf(" (%" PRIu64 " captured)", body_len_captured);
108 printf(", flags 0x%02x", flags);
109
110 if (vflag) {
111 u_int64_t body_len_printed = MIN(body_len_captured, body_len_declared);
112
113 printf(" (%s|%s|%s|%s|%s|%s|%s|%s)",
114 flags & 0x80 ? "MBZ" : "-",
115 flags & 0x40 ? "MBZ" : "-",
116 flags & 0x20 ? "MBZ" : "-",
117 flags & 0x10 ? "MBZ" : "-",
118 flags & 0x08 ? "MBZ" : "-",
119 flags & 0x04 ? "MBZ" : "-",
120 flags & 0x02 ? "MBZ" : "-",
121 flags & 0x01 ? "MORE" : "-");
122
123 if (vflag == 1)
124 body_len_printed = MIN(VBYTES + 1, body_len_printed);
125 if (body_len_printed > 1) {
126 printf(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1);
127 hex_and_ascii_print("\n\t ", cp + header_len + 1, body_len_printed - 1);
128 printf("\n");
129 }
130 }
131
132 TCHECK2(*cp, header_len + body_len_declared); /* Next frame within the buffer ? */
133 return cp + header_len + body_len_declared;
134
135 trunc:
136 printf(" [|zmtp1]");
137 return ep;
138 }
139
140 void
zmtp1_print(const u_char * cp,u_int len)141 zmtp1_print(const u_char *cp, u_int len) {
142 const u_char *ep = MIN(snapend, cp + len);
143
144 printf(": ZMTP/1.0");
145 while (cp < ep)
146 cp = zmtp1_print_frame(cp, ep);
147 }
148
149 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
150 * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
151 * follows.
152 *
153 * In order for late joining consumers to be able to identify message
154 * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
155 * in network byte order specifying either the offset of the first message frame
156 * in the datagram or containing the value 0xFFFF if the datagram contains
157 * solely an intermediate part of a larger message.
158 *
159 * Note that offset specifies where the first message begins rather than the
160 * first message part. Thus, if there are trailing message parts at the
161 * beginning of the packet the offset ignores them and points to first initial
162 * message part in the packet.
163 */
164
165 static const u_char *
zmtp1_print_intermediate_part(const u_char * cp,const u_int len)166 zmtp1_print_intermediate_part(const u_char *cp, const u_int len) {
167 u_int frame_offset;
168 u_int64_t remaining_len;
169
170 TCHECK2(*cp, 2);
171 frame_offset = EXTRACT_16BITS(cp);
172 printf("\n\t frame offset 0x%04x", frame_offset);
173 cp += 2;
174 remaining_len = snapend - cp; /* without the frame length */
175
176 if (frame_offset == 0xFFFF)
177 frame_offset = len - 2; /* always within the declared length */
178 else if (2 + frame_offset > len) {
179 printf(" (exceeds datagram declared length)");
180 goto trunc;
181 }
182
183 /* offset within declared length of the datagram */
184 if (frame_offset) {
185 printf("\n\t frame intermediate part, %u bytes", frame_offset);
186 if (frame_offset > remaining_len)
187 printf(" (%"PRIu64" captured)", remaining_len);
188 if (vflag) {
189 u_int64_t len_printed = MIN(frame_offset, remaining_len);
190
191 if (vflag == 1)
192 len_printed = MIN(VBYTES, len_printed);
193 if (len_printed > 1) {
194 printf(", first %"PRIu64" byte(s):", len_printed);
195 hex_and_ascii_print("\n\t ", cp, len_printed);
196 printf("\n");
197 }
198 }
199 }
200 return cp + frame_offset;
201
202 trunc:
203 printf(" [|zmtp1]");
204 return cp + len;
205 }
206
207 void
zmtp1_print_datagram(const u_char * cp,const u_int len)208 zmtp1_print_datagram(const u_char *cp, const u_int len) {
209 const u_char *ep = MIN(snapend, cp + len);
210
211 cp = zmtp1_print_intermediate_part(cp, len);
212 while (cp < ep)
213 cp = zmtp1_print_frame(cp, ep);
214 }
215