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 * 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 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 * 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 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