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 /* specification: https://rfc.zeromq.org/spec/13/ */
30
31 #include <config.h>
32
33 #include "netdissect-stdinc.h"
34
35 #include "netdissect.h"
36 #include "extract.h"
37
38
39 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
40 * hex and ASCII under a single "-v" flag.
41 */
42 #define VBYTES 128
43
44 static const struct tok flags_bm[] = {
45 { 0x01, "MORE" },
46 { 0x02, "R1" },
47 { 0x04, "R2" },
48 { 0x08, "R3" },
49 { 0x10, "R4" },
50 { 0x20, "R5" },
51 { 0x40, "R6" },
52 { 0x80, "R7" },
53 { 0, NULL }
54 };
55
56 /*
57 * Below is an excerpt from the "13/ZMTP" specification:
58 *
59 * A ZMTP message consists of 1 or more frames.
60 *
61 * A ZMTP frame consists of a length, followed by a flags field and a frame
62 * body of (length - 1) octets. Note: the length includes the flags field, so
63 * an empty frame has a length of 1.
64 *
65 * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
66 * as a single octet. The minimum valid length of a frame is 1 octet, thus a
67 * length of 0 is invalid and such frames SHOULD be discarded silently.
68 *
69 * For frames with lengths of 255 and greater, the length SHALL BE encoded as
70 * a single octet with the value 255, followed by the length encoded as a
71 * 64-bit unsigned integer in network byte order. For frames with lengths of
72 * 1 to 254 octets this encoding MAY be also used.
73 *
74 * The flags field consists of a single octet containing various control
75 * flags. Bit 0 is the least significant bit.
76 *
77 * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
78 * are no more frames to follow. A value of 1 indicates that more frames
79 * will follow. On messages consisting of a single frame the MORE flag MUST
80 * be 0.
81 *
82 * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
83 * zero.
84 */
85
86 static const u_char *
zmtp1_print_frame(netdissect_options * ndo,const u_char * cp,const u_char * ep)87 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
88 {
89 uint64_t body_len_declared, body_len_captured, header_len;
90 uint8_t flags;
91
92 ND_PRINT("\n\t");
93
94 if (GET_U_1(cp) != 0xFF) { /* length/0xFF */
95 header_len = 1; /* length */
96 body_len_declared = GET_U_1(cp);
97 ND_PRINT(" frame flags+body (8-bit) length %" PRIu64, body_len_declared);
98 } else {
99 header_len = 1 + 8; /* 0xFF, length */
100 ND_PRINT(" frame flags+body (64-bit) length");
101 ND_TCHECK_LEN(cp, header_len); /* 0xFF, length */
102 body_len_declared = GET_BE_U_8(cp + 1);
103 ND_PRINT(" %" PRIu64, body_len_declared);
104 }
105 if (body_len_declared == 0)
106 return cp + header_len; /* skip to the next frame */
107 ND_TCHECK_LEN(cp, header_len + 1); /* ..., flags */
108 flags = GET_U_1(cp + header_len);
109
110 body_len_captured = ep - cp - header_len;
111 if (body_len_declared > body_len_captured)
112 ND_PRINT(" (%" PRIu64 " captured)", body_len_captured);
113 ND_PRINT(", flags 0x%02x", flags);
114
115 if (ndo->ndo_vflag) {
116 uint64_t body_len_printed = ND_MIN(body_len_captured, body_len_declared);
117
118 ND_PRINT(" (%s)", bittok2str(flags_bm, "none", flags));
119 if (ndo->ndo_vflag == 1)
120 body_len_printed = ND_MIN(VBYTES + 1, body_len_printed);
121 if (body_len_printed > 1) {
122 ND_PRINT(", 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 }
125 }
126
127 /*
128 * Do not advance cp by the sum of header_len and body_len_declared
129 * before each offset has successfully passed ND_TCHECK_LEN() as the
130 * sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an
131 * infinite loop.
132 */
133 cp += header_len;
134 ND_TCHECK_LEN(cp, body_len_declared); /* Next frame within the buffer ? */
135 return cp + body_len_declared;
136
137 trunc:
138 nd_trunc_longjmp(ndo);
139 }
140
141 void
zmtp1_print(netdissect_options * ndo,const u_char * cp,u_int len)142 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
143 {
144 const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
145
146 ndo->ndo_protocol = "zmtp1";
147 ND_PRINT(": 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 *
zmtp1_print_intermediate_part(netdissect_options * ndo,const u_char * cp,const u_int len)169 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
170 {
171 u_int frame_offset;
172 u_int remaining_len;
173
174 frame_offset = GET_BE_U_2(cp);
175 ND_PRINT("\n\t frame offset 0x%04x", frame_offset);
176 cp += 2;
177 remaining_len = ND_BYTES_AVAILABLE_AFTER(cp); /* without the frame length */
178
179 if (frame_offset == 0xFFFF)
180 frame_offset = len - 2; /* always within the declared length */
181 else if (2 + frame_offset > len) {
182 ND_PRINT(" (exceeds datagram declared length)");
183 goto trunc;
184 }
185
186 /* offset within declared length of the datagram */
187 if (frame_offset) {
188 ND_PRINT("\n\t frame intermediate part, %u bytes", frame_offset);
189 if (frame_offset > remaining_len)
190 ND_PRINT(" (%u captured)", remaining_len);
191 if (ndo->ndo_vflag) {
192 u_int len_printed = ND_MIN(frame_offset, remaining_len);
193
194 if (ndo->ndo_vflag == 1)
195 len_printed = ND_MIN(VBYTES, len_printed);
196 if (len_printed > 1) {
197 ND_PRINT(", first %u byte(s):", len_printed);
198 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
199 }
200 }
201 }
202 return cp + frame_offset;
203
204 trunc:
205 nd_trunc_longjmp(ndo);
206 }
207
208 void
zmtp1_datagram_print(netdissect_options * ndo,const u_char * cp,const u_int len)209 zmtp1_datagram_print(netdissect_options *ndo, const u_char *cp, const u_int len)
210 {
211 const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
212
213 ndo->ndo_protocol = "zmtp1";
214 cp = zmtp1_print_intermediate_part(ndo, cp, len);
215 while (cp < ep)
216 cp = zmtp1_print_frame(ndo, cp, ep);
217 }
218