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 static const char tstr[] = " [|zmtp1]";
40
41 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
42 * hex and ASCII under a single "-v" flag.
43 */
44 #define VBYTES 128
45
46 /*
47 * Below is an excerpt from the "13/ZMTP" specification:
48 *
49 * A ZMTP message consists of 1 or more frames.
50 *
51 * A ZMTP frame consists of a length, followed by a flags field and a frame
52 * body of (length - 1) octets. Note: the length includes the flags field, so
53 * an empty frame has a length of 1.
54 *
55 * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
56 * as a single octet. The minimum valid length of a frame is 1 octet, thus a
57 * length of 0 is invalid and such frames SHOULD be discarded silently.
58 *
59 * For frames with lengths of 255 and greater, the length SHALL BE encoded as
60 * a single octet with the value 255, followed by the length encoded as a
61 * 64-bit unsigned integer in network byte order. For frames with lengths of
62 * 1 to 254 octets this encoding MAY be also used.
63 *
64 * The flags field consists of a single octet containing various control
65 * flags. Bit 0 is the least significant bit.
66 *
67 * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
68 * are no more frames to follow. A value of 1 indicates that more frames
69 * will follow. On messages consisting of a single frame the MORE flag MUST
70 * be 0.
71 *
72 * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
73 * zero.
74 */
75
76 static const u_char *
zmtp1_print_frame(netdissect_options * ndo,const u_char * cp,const u_char * ep)77 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
78 {
79 uint64_t body_len_declared, body_len_captured, header_len;
80 uint8_t flags;
81
82 ND_PRINT((ndo, "\n\t"));
83 ND_TCHECK2(*cp, 1); /* length/0xFF */
84
85 if (cp[0] != 0xFF) {
86 header_len = 1; /* length */
87 body_len_declared = cp[0];
88 ND_PRINT((ndo, " frame flags+body (8-bit) length %" PRIu64, body_len_declared));
89 } else {
90 header_len = 1 + 8; /* 0xFF, length */
91 ND_PRINT((ndo, " frame flags+body (64-bit) length"));
92 ND_TCHECK2(*cp, header_len); /* 0xFF, length */
93 body_len_declared = EXTRACT_64BITS(cp + 1);
94 ND_PRINT((ndo, " %" PRIu64, body_len_declared));
95 }
96 if (body_len_declared == 0)
97 return cp + header_len; /* skip to the next frame */
98 ND_TCHECK2(*cp, header_len + 1); /* ..., flags */
99 flags = cp[header_len];
100
101 body_len_captured = ep - cp - header_len;
102 if (body_len_declared > body_len_captured)
103 ND_PRINT((ndo, " (%" PRIu64 " captured)", body_len_captured));
104 ND_PRINT((ndo, ", flags 0x%02x", flags));
105
106 if (ndo->ndo_vflag) {
107 uint64_t body_len_printed = min(body_len_captured, body_len_declared);
108
109 ND_PRINT((ndo, " (%s|%s|%s|%s|%s|%s|%s|%s)",
110 flags & 0x80 ? "MBZ" : "-",
111 flags & 0x40 ? "MBZ" : "-",
112 flags & 0x20 ? "MBZ" : "-",
113 flags & 0x10 ? "MBZ" : "-",
114 flags & 0x08 ? "MBZ" : "-",
115 flags & 0x04 ? "MBZ" : "-",
116 flags & 0x02 ? "MBZ" : "-",
117 flags & 0x01 ? "MORE" : "-"));
118
119 if (ndo->ndo_vflag == 1)
120 body_len_printed = min(VBYTES + 1, body_len_printed);
121 if (body_len_printed > 1) {
122 ND_PRINT((ndo, ", first %" PRIu64 " byte(s) of body:", body_len_printed - 1));
123 hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
124 ND_PRINT((ndo, "\n"));
125 }
126 }
127
128 /*
129 * Do not advance cp by the sum of header_len and body_len_declared
130 * before each offset has successfully passed ND_TCHECK2() as the
131 * sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an
132 * infinite loop.
133 */
134 cp += header_len;
135 ND_TCHECK2(*cp, body_len_declared); /* Next frame within the buffer ? */
136 return cp + body_len_declared;
137
138 trunc:
139 ND_PRINT((ndo, "%s", tstr));
140 return ep;
141 }
142
143 void
zmtp1_print(netdissect_options * ndo,const u_char * cp,u_int len)144 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
145 {
146 const u_char *ep = min(ndo->ndo_snapend, cp + len);
147
148 ND_PRINT((ndo, ": ZMTP/1.0"));
149 while (cp < ep)
150 cp = zmtp1_print_frame(ndo, cp, ep);
151 }
152
153 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
154 * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
155 * follows.
156 *
157 * In order for late joining consumers to be able to identify message
158 * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
159 * in network byte order specifying either the offset of the first message frame
160 * in the datagram or containing the value 0xFFFF if the datagram contains
161 * solely an intermediate part of a larger message.
162 *
163 * Note that offset specifies where the first message begins rather than the
164 * first message part. Thus, if there are trailing message parts at the
165 * beginning of the packet the offset ignores them and points to first initial
166 * message part in the packet.
167 */
168
169 static const u_char *
zmtp1_print_intermediate_part(netdissect_options * ndo,const u_char * cp,const u_int len)170 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
171 {
172 u_int frame_offset;
173 uint64_t remaining_len;
174
175 ND_TCHECK2(*cp, 2);
176 frame_offset = EXTRACT_16BITS(cp);
177 ND_PRINT((ndo, "\n\t frame offset 0x%04x", frame_offset));
178 cp += 2;
179 remaining_len = ndo->ndo_snapend - cp; /* without the frame length */
180
181 if (frame_offset == 0xFFFF)
182 frame_offset = len - 2; /* always within the declared length */
183 else if (2 + frame_offset > len) {
184 ND_PRINT((ndo, " (exceeds datagram declared length)"));
185 goto trunc;
186 }
187
188 /* offset within declared length of the datagram */
189 if (frame_offset) {
190 ND_PRINT((ndo, "\n\t frame intermediate part, %u bytes", frame_offset));
191 if (frame_offset > remaining_len)
192 ND_PRINT((ndo, " (%"PRIu64" captured)", remaining_len));
193 if (ndo->ndo_vflag) {
194 uint64_t len_printed = min(frame_offset, remaining_len);
195
196 if (ndo->ndo_vflag == 1)
197 len_printed = min(VBYTES, len_printed);
198 if (len_printed > 1) {
199 ND_PRINT((ndo, ", first %"PRIu64" byte(s):", len_printed));
200 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
201 ND_PRINT((ndo, "\n"));
202 }
203 }
204 }
205 return cp + frame_offset;
206
207 trunc:
208 ND_PRINT((ndo, "%s", tstr));
209 return cp + len;
210 }
211
212 void
zmtp1_print_datagram(netdissect_options * ndo,const u_char * cp,const u_int len)213 zmtp1_print_datagram(netdissect_options *ndo, const u_char *cp, const u_int len)
214 {
215 const u_char *ep = min(ndo->ndo_snapend, cp + len);
216
217 cp = zmtp1_print_intermediate_part(ndo, cp, len);
218 while (cp < ep)
219 cp = zmtp1_print_frame(ndo, cp, ep);
220 }
221