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 * 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 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 * 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 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