The Tcpdump Group git mirrors - tcpdump/blob - print-zeromq.c

   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 #ifdef HAVE_CONFIG_H
  32 #include <config.h>
  33 #endif
  34
  35 #include "netdissect-stdinc.h"
  36
  37 #include "netdissect.h"
  38 #include "extract.h"
  39
  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 static const struct tok flags_bm[] = {
  47         { 0x01, "MORE"  },
  48         { 0x02, "R1" },
  49         { 0x04, "R2" },
  50         { 0x08, "R3" },
  51         { 0x10, "R4" },
  52         { 0x20, "R5" },
  53         { 0x40, "R6" },
  54         { 0x80, "R7" },
  55         { 0, NULL }
  56 };
  57
  58 /*
  59  * Below is an excerpt from the "13/ZMTP" specification:
  60  *
  61  * A ZMTP message consists of 1 or more frames.
  62  *
  63  * A ZMTP frame consists of a length, followed by a flags field and a frame
  64  * body of (length - 1) octets. Note: the length includes the flags field, so
  65  * an empty frame has a length of 1.
  66  *
  67  * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
  68  * as a single octet. The minimum valid length of a frame is 1 octet, thus a
  69  * length of 0 is invalid and such frames SHOULD be discarded silently.
  70  *
  71  * For frames with lengths of 255 and greater, the length SHALL BE encoded as
  72  * a single octet with the value 255, followed by the length encoded as a
  73  * 64-bit unsigned integer in network byte order. For frames with lengths of
  74  * 1 to 254 octets this encoding MAY be also used.
  75  *
  76  * The flags field consists of a single octet containing various control
  77  * flags. Bit 0 is the least significant bit.
  78  *
  79  * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
  80  *   are no more frames to follow. A value of 1 indicates that more frames
  81  *   will follow. On messages consisting of a single frame the MORE flag MUST
  82  *   be 0.
  83  *
  84  * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
  85  *   zero.
  86  */
  87
  88 static const u_char *
  89 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
  90 {
  91         uint64_t body_len_declared, body_len_captured, header_len;
  92         uint8_t flags;
  93
  94         ND_PRINT("\n\t");
  95
  96         if (GET_U_1(cp) != 0xFF) {      /* length/0xFF */
  97                 header_len = 1; /* length */
  98                 body_len_declared = GET_U_1(cp);
  99                 ND_PRINT(" frame flags+body  (8-bit) length %" PRIu64, body_len_declared);
 100         } else {
 101                 header_len = 1 + 8; /* 0xFF, length */
 102                 ND_PRINT(" frame flags+body (64-bit) length");
 103                 ND_TCHECK_LEN(cp, header_len); /* 0xFF, length */
 104                 body_len_declared = GET_BE_U_8(cp + 1);
 105                 ND_PRINT(" %" PRIu64, body_len_declared);
 106         }
 107         if (body_len_declared == 0)
 108                 return cp + header_len; /* skip to the next frame */
 109         ND_TCHECK_LEN(cp, header_len + 1); /* ..., flags */
 110         flags = GET_U_1(cp + header_len);
 111
 112         body_len_captured = ep - cp - header_len;
 113         if (body_len_declared > body_len_captured)
 114                 ND_PRINT(" (%" PRIu64 " captured)", body_len_captured);
 115         ND_PRINT(", flags 0x%02x", flags);
 116
 117         if (ndo->ndo_vflag) {
 118                 uint64_t body_len_printed = ND_MIN(body_len_captured, body_len_declared);
 119
 120                 ND_PRINT(" (%s)", bittok2str(flags_bm, "none", flags));
 121                 if (ndo->ndo_vflag == 1)
 122                         body_len_printed = ND_MIN(VBYTES + 1, body_len_printed);
 123                 if (body_len_printed > 1) {
 124                         ND_PRINT(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1);
 125                         hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
 126                 }
 127         }
 128
 129         /*
 130          * Do not advance cp by the sum of header_len and body_len_declared
 131          * before each offset has successfully passed ND_TCHECK_LEN() as the
 132          * sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an
 133          * infinite loop.
 134          */
 135         cp += header_len;
 136         ND_TCHECK_LEN(cp, body_len_declared); /* Next frame within the buffer ? */
 137         return cp + body_len_declared;
 138
 139 trunc:
 140         nd_trunc_longjmp(ndo);
 141 }
 142
 143 void
 144 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
 145 {
 146         const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
 147
 148         ndo->ndo_protocol = "zmtp1";
 149         ND_PRINT(": ZMTP/1.0");
 150         while (cp < ep)
 151                 cp = zmtp1_print_frame(ndo, cp, ep);
 152 }
 153
 154 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
 155  * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
 156  * follows.
 157  *
 158  * In order for late joining consumers to be able to identify message
 159  * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
 160  * in network byte order specifying either the offset of the first message frame
 161  * in the datagram or containing the value 0xFFFF if the datagram contains
 162  * solely an intermediate part of a larger message.
 163  *
 164  * Note that offset specifies where the first message begins rather than the
 165  * first message part. Thus, if there are trailing message parts at the
 166  * beginning of the packet the offset ignores them and points to first initial
 167  * message part in the packet.
 168  */
 169
 170 static const u_char *
 171 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
 172 {
 173         u_int frame_offset;
 174         u_int remaining_len;
 175
 176         frame_offset = GET_BE_U_2(cp);
 177         ND_PRINT("\n\t frame offset 0x%04x", frame_offset);
 178         cp += 2;
 179         remaining_len = ND_BYTES_AVAILABLE_AFTER(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(" (exceeds datagram declared length)");
 185                 goto trunc;
 186         }
 187
 188         /* offset within declared length of the datagram */
 189         if (frame_offset) {
 190                 ND_PRINT("\n\t frame intermediate part, %u bytes", frame_offset);
 191                 if (frame_offset > remaining_len)
 192                         ND_PRINT(" (%u captured)", remaining_len);
 193                 if (ndo->ndo_vflag) {
 194                         u_int len_printed = ND_MIN(frame_offset, remaining_len);
 195
 196                         if (ndo->ndo_vflag == 1)
 197                                 len_printed = ND_MIN(VBYTES, len_printed);
 198                         if (len_printed > 1) {
 199                                 ND_PRINT(", first %u byte(s):", len_printed);
 200                                 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
 201                         }
 202                 }
 203         }
 204         return cp + frame_offset;
 205
 206 trunc:
 207         nd_trunc_longjmp(ndo);
 208 }
 209
 210 void
 211 zmtp1_datagram_print(netdissect_options *ndo, const u_char *cp, const u_int len)
 212 {
 213         const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
 214
 215         ndo->ndo_protocol = "zmtp1";
 216         cp = zmtp1_print_intermediate_part(ndo, cp, len);
 217         while (cp < ep)
 218                 cp = zmtp1_print_frame(ndo, cp, ep);
 219 }