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1 office 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 #define NETDISSECT_REWORKED
32 #ifdef HAVE_CONFIG_H
33 #include "config.h"
34 #endif
35  
36 #include <tcpdump-stdinc.h>
37  
38 #include "interface.h"
39 #include "extract.h"
40  
41 static const char tstr[] = " [|zmtp1]";
42  
43 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
44 * hex and ASCII under a single "-v" flag.
45 */
46 #define VBYTES 128
47  
48 /*
49 * Below is an excerpt from the "13/ZMTP" specification:
50 *
51 * A ZMTP message consists of 1 or more frames.
52 *
53 * A ZMTP frame consists of a length, followed by a flags field and a frame
54 * body of (length - 1) octets. Note: the length includes the flags field, so
55 * an empty frame has a length of 1.
56 *
57 * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
58 * as a single octet. The minimum valid length of a frame is 1 octet, thus a
59 * length of 0 is invalid and such frames SHOULD be discarded silently.
60 *
61 * For frames with lengths of 255 and greater, the length SHALL BE encoded as
62 * a single octet with the value 255, followed by the length encoded as a
63 * 64-bit unsigned integer in network byte order. For frames with lengths of
64 * 1 to 254 octets this encoding MAY be also used.
65 *
66 * The flags field consists of a single octet containing various control
67 * flags. Bit 0 is the least significant bit.
68 *
69 * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
70 * are no more frames to follow. A value of 1 indicates that more frames
71 * will follow. On messages consisting of a single frame the MORE flag MUST
72 * be 0.
73 *
74 * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
75 * zero.
76 */
77  
78 static const u_char *
79 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
80 {
81 uint64_t body_len_declared, body_len_captured, header_len;
82 uint8_t flags;
83  
84 ND_PRINT((ndo, "\n\t"));
85 ND_TCHECK2(*cp, 1); /* length/0xFF */
86  
87 if (cp[0] != 0xFF) {
88 header_len = 1; /* length */
89 body_len_declared = cp[0];
90 if (body_len_declared == 0)
91 return cp + header_len; /* skip to next frame */
92 ND_PRINT((ndo, " frame flags+body (8-bit) length %u", cp[0]));
93 ND_TCHECK2(*cp, header_len + 1); /* length, flags */
94 flags = cp[1];
95 } else {
96 header_len = 1 + 8; /* 0xFF, length */
97 ND_PRINT((ndo, " frame flags+body (64-bit) length"));
98 ND_TCHECK2(*cp, header_len); /* 0xFF, length */
99 body_len_declared = EXTRACT_64BITS(cp + 1);
100 if (body_len_declared == 0)
101 return cp + header_len; /* skip to next frame */
102 ND_PRINT((ndo, " %" PRIu64, body_len_declared));
103 ND_TCHECK2(*cp, header_len + 1); /* 0xFF, length, flags */
104 flags = cp[9];
105 }
106  
107 body_len_captured = ep - cp - header_len;
108 if (body_len_declared > body_len_captured)
109 ND_PRINT((ndo, " (%" PRIu64 " captured)", body_len_captured));
110 ND_PRINT((ndo, ", flags 0x%02x", flags));
111  
112 if (ndo->ndo_vflag) {
113 uint64_t body_len_printed = min(body_len_captured, body_len_declared);
114  
115 ND_PRINT((ndo, " (%s|%s|%s|%s|%s|%s|%s|%s)",
116 flags & 0x80 ? "MBZ" : "-",
117 flags & 0x40 ? "MBZ" : "-",
118 flags & 0x20 ? "MBZ" : "-",
119 flags & 0x10 ? "MBZ" : "-",
120 flags & 0x08 ? "MBZ" : "-",
121 flags & 0x04 ? "MBZ" : "-",
122 flags & 0x02 ? "MBZ" : "-",
123 flags & 0x01 ? "MORE" : "-"));
124  
125 if (ndo->ndo_vflag == 1)
126 body_len_printed = min(VBYTES + 1, body_len_printed);
127 if (body_len_printed > 1) {
128 ND_PRINT((ndo, ", first %" PRIu64 " byte(s) of body:", body_len_printed - 1));
129 hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
130 ND_PRINT((ndo, "\n"));
131 }
132 }
133  
134 ND_TCHECK2(*cp, header_len + body_len_declared); /* Next frame within the buffer ? */
135 return cp + header_len + body_len_declared;
136  
137 trunc:
138 ND_PRINT((ndo, "%s", tstr));
139 return ep;
140 }
141  
142 void
143 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
144 {
145 const u_char *ep = min(ndo->ndo_snapend, cp + len);
146  
147 ND_PRINT((ndo, ": ZMTP/1.0"));
148 while (cp < ep)
149 cp = zmtp1_print_frame(ndo, cp, ep);
150 }
151  
152 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
153 * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
154 * follows.
155 *
156 * In order for late joining consumers to be able to identify message
157 * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
158 * in network byte order specifying either the offset of the first message frame
159 * in the datagram or containing the value 0xFFFF if the datagram contains
160 * solely an intermediate part of a larger message.
161 *
162 * Note that offset specifies where the first message begins rather than the
163 * first message part. Thus, if there are trailing message parts at the
164 * beginning of the packet the offset ignores them and points to first initial
165 * message part in the packet.
166 */
167  
168 static const u_char *
169 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
170 {
171 u_int frame_offset;
172 uint64_t remaining_len;
173  
174 ND_TCHECK2(*cp, 2);
175 frame_offset = EXTRACT_16BITS(cp);
176 ND_PRINT((ndo, "\n\t frame offset 0x%04x", frame_offset));
177 cp += 2;
178 remaining_len = ndo->ndo_snapend - cp; /* without the frame length */
179  
180 if (frame_offset == 0xFFFF)
181 frame_offset = len - 2; /* always within the declared length */
182 else if (2 + frame_offset > len) {
183 ND_PRINT((ndo, " (exceeds datagram declared length)"));
184 goto trunc;
185 }
186  
187 /* offset within declared length of the datagram */
188 if (frame_offset) {
189 ND_PRINT((ndo, "\n\t frame intermediate part, %u bytes", frame_offset));
190 if (frame_offset > remaining_len)
191 ND_PRINT((ndo, " (%"PRIu64" captured)", remaining_len));
192 if (ndo->ndo_vflag) {
193 uint64_t len_printed = min(frame_offset, remaining_len);
194  
195 if (ndo->ndo_vflag == 1)
196 len_printed = min(VBYTES, len_printed);
197 if (len_printed > 1) {
198 ND_PRINT((ndo, ", first %"PRIu64" byte(s):", len_printed));
199 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
200 ND_PRINT((ndo, "\n"));
201 }
202 }
203 }
204 return cp + frame_offset;
205  
206 trunc:
207 ND_PRINT((ndo, "%s", tstr));
208 return cp + len;
209 }
210  
211 void
212 zmtp1_print_datagram(netdissect_options *ndo, const u_char *cp, const u_int len)
213 {
214 const u_char *ep = min(ndo->ndo_snapend, cp + len);
215  
216 cp = zmtp1_print_intermediate_part(ndo, cp, len);
217 while (cp < ep)
218 cp = zmtp1_print_frame(ndo, cp, ep);
219 }