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

   1 /*
   2  * This file implements decoding of ZeroMQ network protocol(s).
   3  *
   4  *
   5  * Copyright (c) 2013 The TCPDUMP project
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  18  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  21  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  23  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  24  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  25  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  27  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  28  * POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #define NETDISSECT_REWORKED
  32 #ifdef HAVE_CONFIG_H
  33 #include "config.h"
  34 #endif
  35
  36 #include <tcpdump-stdinc.h>
  37
  38 #include "interface.h"
  39 #include "extract.h"
  40
  41 static const char tstr[] = " [|zmtp1]";
  42
  43 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
  44  * hex and ASCII under a single "-v" flag.
  45  */
  46 #define VBYTES 128
  47
  48 /*
  49  * Below is an excerpt from the "13/ZMTP" specification:
  50  *
  51  * A ZMTP message consists of 1 or more frames.
  52  *
  53  * A ZMTP frame consists of a length, followed by a flags field and a frame
  54  * body of (length - 1) octets. Note: the length includes the flags field, so
  55  * an empty frame has a length of 1.
  56  *
  57  * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
  58  * as a single octet. The minimum valid length of a frame is 1 octet, thus a
  59  * length of 0 is invalid and such frames SHOULD be discarded silently.
  60  *
  61  * For frames with lengths of 255 and greater, the length SHALL BE encoded as
  62  * a single octet with the value 255, followed by the length encoded as a
  63  * 64-bit unsigned integer in network byte order. For frames with lengths of
  64  * 1 to 254 octets this encoding MAY be also used.
  65  *
  66  * The flags field consists of a single octet containing various control
  67  * flags. Bit 0 is the least significant bit.
  68  *
  69  * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
  70  *   are no more frames to follow. A value of 1 indicates that more frames
  71  *   will follow. On messages consisting of a single frame the MORE flag MUST
  72  *   be 0.
  73  *
  74  * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
  75  *   zero.
  76  */
  77
  78 static const u_char *
  79 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep) {
  80         u_int64_t body_len_declared, body_len_captured, header_len;
  81         u_int8_t flags;
  82
  83         ND_PRINT((ndo, "\n\t"));
  84         ND_TCHECK2(*cp, 1); /* length/0xFF */
  85
  86         if (cp[0] != 0xFF) {
  87                 header_len = 1; /* length */
  88                 body_len_declared = cp[0];
  89                 if (body_len_declared == 0)
  90                         return cp + header_len; /* skip to next frame */
  91                 ND_PRINT((ndo, " frame flags+body  (8-bit) length %u", cp[0]));
  92                 ND_TCHECK2(*cp, header_len + 1); /* length, flags */
  93                 flags = cp[1];
  94         } else {
  95                 header_len = 1 + 8; /* 0xFF, length */
  96                 ND_PRINT((ndo, " frame flags+body (64-bit) length"));
  97                 ND_TCHECK2(*cp, header_len); /* 0xFF, length */
  98                 body_len_declared = EXTRACT_64BITS(cp + 1);
  99                 if (body_len_declared == 0)
 100                         return cp + header_len; /* skip to next frame */
 101                 ND_PRINT((ndo, " %" PRIu64, body_len_declared));
 102                 ND_TCHECK2(*cp, header_len + 1); /* 0xFF, length, flags */
 103                 flags = cp[9];
 104         }
 105
 106         body_len_captured = ep - cp - header_len;
 107         if (body_len_declared > body_len_captured)
 108                 ND_PRINT((ndo, " (%" PRIu64 " captured)", body_len_captured));
 109         ND_PRINT((ndo, ", flags 0x%02x", flags));
 110
 111         if (ndo->ndo_vflag) {
 112                 u_int64_t body_len_printed = min(body_len_captured, body_len_declared);
 113
 114                 ND_PRINT((ndo, " (%s|%s|%s|%s|%s|%s|%s|%s)",
 115                         flags & 0x80 ? "MBZ" : "-",
 116                         flags & 0x40 ? "MBZ" : "-",
 117                         flags & 0x20 ? "MBZ" : "-",
 118                         flags & 0x10 ? "MBZ" : "-",
 119                         flags & 0x08 ? "MBZ" : "-",
 120                         flags & 0x04 ? "MBZ" : "-",
 121                         flags & 0x02 ? "MBZ" : "-",
 122                         flags & 0x01 ? "MORE" : "-"));
 123
 124                 if (ndo->ndo_vflag == 1)
 125                         body_len_printed = min(VBYTES + 1, body_len_printed);
 126                 if (body_len_printed > 1) {
 127                         ND_PRINT((ndo, ", 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                         ND_PRINT((ndo, "\n"));
 130                 }
 131         }
 132
 133         ND_TCHECK2(*cp, header_len + body_len_declared); /* Next frame within the buffer ? */
 134         return cp + header_len + body_len_declared;
 135
 136 trunc:
 137         ND_PRINT((ndo, "%s", tstr));
 138         return ep;
 139 }
 140
 141 void
 142 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len) {
 143         const u_char *ep = min(ndo->ndo_snapend, cp + len);
 144
 145         ND_PRINT((ndo, ": ZMTP/1.0"));
 146         while (cp < ep)
 147                 cp = zmtp1_print_frame(ndo, cp, ep);
 148 }
 149
 150 /* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
 151  * field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
 152  * follows.
 153  *
 154  * In order for late joining consumers to be able to identify message
 155  * boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
 156  * in network byte order specifying either the offset of the first message frame
 157  * in the datagram or containing the value 0xFFFF if the datagram contains
 158  * solely an intermediate part of a larger message.
 159  *
 160  * Note that offset specifies where the first message begins rather than the
 161  * first message part. Thus, if there are trailing message parts at the
 162  * beginning of the packet the offset ignores them and points to first initial
 163  * message part in the packet.
 164  */
 165
 166 static const u_char *
 167 zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len) {
 168         u_int frame_offset;
 169         u_int64_t remaining_len;
 170
 171         ND_TCHECK2(*cp, 2);
 172         frame_offset = EXTRACT_16BITS(cp);
 173         ND_PRINT((ndo, "\n\t frame offset 0x%04x", frame_offset));
 174         cp += 2;
 175         remaining_len = ndo->ndo_snapend - cp; /* without the frame length */
 176
 177         if (frame_offset == 0xFFFF)
 178                 frame_offset = len - 2; /* always within the declared length */
 179         else if (2 + frame_offset > len) {
 180                 ND_PRINT((ndo, " (exceeds datagram declared length)"));
 181                 goto trunc;
 182         }
 183
 184         /* offset within declared length of the datagram */
 185         if (frame_offset) {
 186                 ND_PRINT((ndo, "\n\t frame intermediate part, %u bytes", frame_offset));
 187                 if (frame_offset > remaining_len)
 188                         ND_PRINT((ndo, " (%"PRIu64" captured)", remaining_len));
 189                 if (ndo->ndo_vflag) {
 190                         u_int64_t len_printed = min(frame_offset, remaining_len);
 191
 192                         if (ndo->ndo_vflag == 1)
 193                                 len_printed = min(VBYTES, len_printed);
 194                         if (len_printed > 1) {
 195                                 ND_PRINT((ndo, ", first %"PRIu64" byte(s):", len_printed));
 196                                 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
 197                                 ND_PRINT((ndo, "\n"));
 198                         }
 199                 }
 200         }
 201         return cp + frame_offset;
 202
 203 trunc:
 204         ND_PRINT((ndo, "%s", tstr));
 205         return cp + len;
 206 }
 207
 208 void
 209 zmtp1_print_datagram(netdissect_options *ndo, const u_char *cp, const u_int len) {
 210         const u_char *ep = min(ndo->ndo_snapend, cp + len);
 211
 212         cp = zmtp1_print_intermediate_part(ndo, cp, len);
 213         while (cp < ep)
 214                 cp = zmtp1_print_frame(ndo, cp, ep);
 215 }