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
  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
  40 /* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
  41  * hex and ASCII under a single "-v" flag.
  42  */
  43 #define VBYTES 128
  44
  45 /*
  46  * Below is an excerpt from the "13/ZMTP" specification:
  47  *
  48  * A ZMTP message consists of 1 or more frames.
  49  *
  50  * A ZMTP frame consists of a length, followed by a flags field and a frame
  51  * body of (length - 1) octets. Note: the length includes the flags field, so
  52  * an empty frame has a length of 1.
  53  *
  54  * For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
  55  * as a single octet. The minimum valid length of a frame is 1 octet, thus a
  56  * length of 0 is invalid and such frames SHOULD be discarded silently.
  57  *
  58  * For frames with lengths of 255 and greater, the length SHALL BE encoded as
  59  * a single octet with the value 255, followed by the length encoded as a
  60  * 64-bit unsigned integer in network byte order. For frames with lengths of
  61  * 1 to 254 octets this encoding MAY be also used.
  62  *
  63  * The flags field consists of a single octet containing various control
  64  * flags. Bit 0 is the least significant bit.
  65  *
  66  * - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
  67  *   are no more frames to follow. A value of 1 indicates that more frames
  68  *   will follow. On messages consisting of a single frame the MORE flag MUST
  69  *   be 0.
  70  *
  71  * - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
  72  *   zero.
  73  */
  74
  75 static const u_char *
  76 zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
  77 {
  78         uint64_t body_len_declared, body_len_captured, header_len;
  79         uint8_t flags;
  80
  81         ND_PRINT("\n\t");
  82         ND_TCHECK_1(cp); /* length/0xFF */
  83
  84         if (GET_U_1(cp) != 0xFF) {
  85                 header_len = 1; /* length */
  86                 body_len_declared = GET_U_1(cp);
  87                 ND_PRINT(" frame flags+body  (8-bit) length %" PRIu64, body_len_declared);
  88         } else {
  89                 header_len = 1 + 8; /* 0xFF, length */
  90                 ND_PRINT(" frame flags+body (64-bit) length");
  91                 ND_TCHECK_LEN(cp, header_len); /* 0xFF, length */
  92                 body_len_declared = GET_BE_U_8(cp + 1);
  93                 ND_PRINT(" %" PRIu64, body_len_declared);
  94         }
  95         if (body_len_declared == 0)
  96                 return cp + header_len; /* skip to the next frame */
  97         ND_TCHECK_LEN(cp, header_len + 1); /* ..., flags */
  98         flags = GET_U_1(cp + header_len);
  99
 100         body_len_captured = ep - cp - header_len;
 101         if (body_len_declared > body_len_captured)
 102                 ND_PRINT(" (%" PRIu64 " captured)", body_len_captured);
 103         ND_PRINT(", flags 0x%02x", flags);
 104
 105         if (ndo->ndo_vflag) {
 106                 uint64_t body_len_printed = min(body_len_captured, body_len_declared);
 107
 108                 ND_PRINT(" (%s|%s|%s|%s|%s|%s|%s|%s)",
 109                         flags & 0x80 ? "MBZ" : "-",
 110                         flags & 0x40 ? "MBZ" : "-",
 111                         flags & 0x20 ? "MBZ" : "-",
 112                         flags & 0x10 ? "MBZ" : "-",
 113                         flags & 0x08 ? "MBZ" : "-",
 114                         flags & 0x04 ? "MBZ" : "-",
 115                         flags & 0x02 ? "MBZ" : "-",
 116                         flags & 0x01 ? "MORE" : "-");
 117
 118                 if (ndo->ndo_vflag == 1)
 119                         body_len_printed = min(VBYTES + 1, body_len_printed);
 120                 if (body_len_printed > 1) {
 121                         ND_PRINT(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1);
 122                         hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
 123                 }
 124         }
 125
 126         /*
 127          * Do not advance cp by the sum of header_len and body_len_declared
 128          * before each offset has successfully passed ND_TCHECK_LEN() as the
 129          * sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an
 130          * infinite loop.
 131          */
 132         cp += header_len;
 133         ND_TCHECK_LEN(cp, body_len_declared); /* Next frame within the buffer ? */
 134         return cp + body_len_declared;
 135
 136 trunc:
 137         nd_print_trunc(ndo);
 138         return ep;
 139 }
 140
 141 void
 142 zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
 143 {
 144         const u_char *ep = 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         uint64_t remaining_len;
 173
 174         ND_TCHECK_2(cp);
 175         frame_offset = GET_BE_U_2(cp);
 176         ND_PRINT("\n\t frame offset 0x%04x", frame_offset);
 177         cp += 2;
 178         remaining_len = ndo->ndo_snapend - cp; /* without the frame length */
 179
 180         if (frame_offset == 0xFFFF)
 181                 frame_offset = len - 2; /* always within the declared length */
 182         else if (2 + frame_offset > len) {
 183                 ND_PRINT(" (exceeds datagram declared length)");
 184                 goto trunc;
 185         }
 186
 187         /* offset within declared length of the datagram */
 188         if (frame_offset) {
 189                 ND_PRINT("\n\t frame intermediate part, %u bytes", frame_offset);
 190                 if (frame_offset > remaining_len)
 191                         ND_PRINT(" (%"PRIu64" captured)", remaining_len);
 192                 if (ndo->ndo_vflag) {
 193                         uint64_t len_printed = min(frame_offset, remaining_len);
 194
 195                         if (ndo->ndo_vflag == 1)
 196                                 len_printed = min(VBYTES, len_printed);
 197                         if (len_printed > 1) {
 198                                 ND_PRINT(", first %"PRIu64" byte(s):", len_printed);
 199                                 hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
 200                         }
 201                 }
 202         }
 203         return cp + frame_offset;
 204
 205 trunc:
 206         nd_print_trunc(ndo);
 207         return cp + len;
 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 = 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 }