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 #include <sys/cdefs.h> 29 #ifndef lint 30 __RCSID("$NetBSD: print-zeromq.c,v 1.5 2024/09/02 16:15:33 christos Exp $"); 31 #endif 32 33 /* \summary: ZeroMQ Message Transport Protocol (ZMTP) printer */ 34 /* specification: https://rfc.zeromq.org/spec/13/ */ 35 36 #include <config.h> 37 38 #include "netdissect-stdinc.h" 39 40 #include "netdissect.h" 41 #include "extract.h" 42 43 44 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in 45 * hex and ASCII under a single "-v" flag. 46 */ 47 #define VBYTES 128 48 49 static const struct tok flags_bm[] = { 50 { 0x01, "MORE" }, 51 { 0x02, "R1" }, 52 { 0x04, "R2" }, 53 { 0x08, "R3" }, 54 { 0x10, "R4" }, 55 { 0x20, "R5" }, 56 { 0x40, "R6" }, 57 { 0x80, "R7" }, 58 { 0, NULL } 59 }; 60 61 /* 62 * Below is an excerpt from the "13/ZMTP" specification: 63 * 64 * A ZMTP message consists of 1 or more frames. 65 * 66 * A ZMTP frame consists of a length, followed by a flags field and a frame 67 * body of (length - 1) octets. Note: the length includes the flags field, so 68 * an empty frame has a length of 1. 69 * 70 * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded 71 * as a single octet. The minimum valid length of a frame is 1 octet, thus a 72 * length of 0 is invalid and such frames SHOULD be discarded silently. 73 * 74 * For frames with lengths of 255 and greater, the length SHALL BE encoded as 75 * a single octet with the value 255, followed by the length encoded as a 76 * 64-bit unsigned integer in network byte order. For frames with lengths of 77 * 1 to 254 octets this encoding MAY be also used. 78 * 79 * The flags field consists of a single octet containing various control 80 * flags. Bit 0 is the least significant bit. 81 * 82 * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there 83 * are no more frames to follow. A value of 1 indicates that more frames 84 * will follow. On messages consisting of a single frame the MORE flag MUST 85 * be 0. 86 * 87 * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be 88 * zero. 89 */ 90 91 static const u_char * 92 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep) 93 { 94 uint64_t body_len_declared, body_len_captured, header_len; 95 uint8_t flags; 96 97 ND_PRINT("\n\t"); 98 99 if (GET_U_1(cp) != 0xFF) { /* length/0xFF */ 100 header_len = 1; /* length */ 101 body_len_declared = GET_U_1(cp); 102 ND_PRINT(" frame flags+body (8-bit) length %" PRIu64, body_len_declared); 103 } else { 104 header_len = 1 + 8; /* 0xFF, length */ 105 ND_PRINT(" frame flags+body (64-bit) length"); 106 ND_TCHECK_LEN(cp, header_len); /* 0xFF, length */ 107 body_len_declared = GET_BE_U_8(cp + 1); 108 ND_PRINT(" %" PRIu64, body_len_declared); 109 } 110 if (body_len_declared == 0) 111 return cp + header_len; /* skip to the next frame */ 112 ND_TCHECK_LEN(cp, header_len + 1); /* ..., flags */ 113 flags = GET_U_1(cp + header_len); 114 115 body_len_captured = ep - cp - header_len; 116 if (body_len_declared > body_len_captured) 117 ND_PRINT(" (%" PRIu64 " captured)", body_len_captured); 118 ND_PRINT(", flags 0x%02x", flags); 119 120 if (ndo->ndo_vflag) { 121 uint64_t body_len_printed = ND_MIN(body_len_captured, body_len_declared); 122 123 ND_PRINT(" (%s)", bittok2str(flags_bm, "none", flags)); 124 if (ndo->ndo_vflag == 1) 125 body_len_printed = ND_MIN(VBYTES + 1, body_len_printed); 126 if (body_len_printed > 1) { 127 ND_PRINT(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1); 128 hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1); 129 } 130 } 131 132 /* 133 * Do not advance cp by the sum of header_len and body_len_declared 134 * before each offset has successfully passed ND_TCHECK_LEN() as the 135 * sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an 136 * infinite loop. 137 */ 138 cp += header_len; 139 ND_TCHECK_LEN(cp, body_len_declared); /* Next frame within the buffer ? */ 140 return cp + body_len_declared; 141 142 trunc: 143 nd_trunc_longjmp(ndo); 144 } 145 146 void 147 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len) 148 { 149 const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len); 150 151 ndo->ndo_protocol = "zmtp1"; 152 ND_PRINT(": ZMTP/1.0"); 153 while (cp < ep) 154 cp = zmtp1_print_frame(ndo, cp, ep); 155 } 156 157 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data" 158 * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page 159 * follows. 160 * 161 * In order for late joining consumers to be able to identify message 162 * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer 163 * in network byte order specifying either the offset of the first message frame 164 * in the datagram or containing the value 0xFFFF if the datagram contains 165 * solely an intermediate part of a larger message. 166 * 167 * Note that offset specifies where the first message begins rather than the 168 * first message part. Thus, if there are trailing message parts at the 169 * beginning of the packet the offset ignores them and points to first initial 170 * message part in the packet. 171 */ 172 173 static const u_char * 174 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len) 175 { 176 u_int frame_offset; 177 u_int remaining_len; 178 179 frame_offset = GET_BE_U_2(cp); 180 ND_PRINT("\n\t frame offset 0x%04x", frame_offset); 181 cp += 2; 182 remaining_len = ND_BYTES_AVAILABLE_AFTER(cp); /* without the frame length */ 183 184 if (frame_offset == 0xFFFF) 185 frame_offset = len - 2; /* always within the declared length */ 186 else if (2 + frame_offset > len) { 187 ND_PRINT(" (exceeds datagram declared length)"); 188 goto trunc; 189 } 190 191 /* offset within declared length of the datagram */ 192 if (frame_offset) { 193 ND_PRINT("\n\t frame intermediate part, %u bytes", frame_offset); 194 if (frame_offset > remaining_len) 195 ND_PRINT(" (%u captured)", remaining_len); 196 if (ndo->ndo_vflag) { 197 u_int len_printed = ND_MIN(frame_offset, remaining_len); 198 199 if (ndo->ndo_vflag == 1) 200 len_printed = ND_MIN(VBYTES, len_printed); 201 if (len_printed > 1) { 202 ND_PRINT(", first %u byte(s):", len_printed); 203 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed); 204 } 205 } 206 } 207 return cp + frame_offset; 208 209 trunc: 210 nd_trunc_longjmp(ndo); 211 } 212 213 void 214 zmtp1_datagram_print(netdissect_options *ndo, const u_char *cp, const u_int len) 215 { 216 const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len); 217 218 ndo->ndo_protocol = "zmtp1"; 219 cp = zmtp1_print_intermediate_part(ndo, cp, len); 220 while (cp < ep) 221 cp = zmtp1_print_frame(ndo, cp, ep); 222 } 223