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/*
* Copyright (c) 2013 The TCPDUMP project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/* \summary: ZeroMQ Message Transport Protocol (ZMTP) printer */
/* specification: https://rfc.zeromq.org/spec/13/ */
#include <config.h>
#include "netdissect-stdinc.h"
#include "netdissect.h"
#include "extract.h"
/* Maximum number of ZMTP/1.0 frame body bytes (without the flags) to dump in
* hex and ASCII under a single "-v" flag.
*/
#define VBYTES 128
static const struct tok flags_bm[] = {
{ 0x01, "MORE" },
{ 0x02, "R1" },
{ 0x04, "R2" },
{ 0x08, "R3" },
{ 0x10, "R4" },
{ 0x20, "R5" },
{ 0x40, "R6" },
{ 0x80, "R7" },
{ 0, NULL }
};
/*
* Below is an excerpt from the "13/ZMTP" specification:
*
* A ZMTP message consists of 1 or more frames.
*
* A ZMTP frame consists of a length, followed by a flags field and a frame
* body of (length - 1) octets. Note: the length includes the flags field, so
* an empty frame has a length of 1.
*
* For frames with a length of 1 to 254 octets, the length SHOULD BE encoded
* as a single octet. The minimum valid length of a frame is 1 octet, thus a
* length of 0 is invalid and such frames SHOULD be discarded silently.
*
* For frames with lengths of 255 and greater, the length SHALL BE encoded as
* a single octet with the value 255, followed by the length encoded as a
* 64-bit unsigned integer in network byte order. For frames with lengths of
* 1 to 254 octets this encoding MAY be also used.
*
* The flags field consists of a single octet containing various control
* flags. Bit 0 is the least significant bit.
*
* - Bit 0 (MORE): More frames to follow. A value of 0 indicates that there
* are no more frames to follow. A value of 1 indicates that more frames
* will follow. On messages consisting of a single frame the MORE flag MUST
* be 0.
*
* - Bits 1-7: Reserved. Bits 1-7 are reserved for future use and SHOULD be
* zero.
*/
static const u_char *
zmtp1_print_frame(netdissect_options *ndo, const u_char *cp, const u_char *ep)
{
uint64_t body_len_declared, body_len_captured, header_len;
uint8_t flags;
ND_PRINT("\n\t");
if (GET_U_1(cp) != 0xFF) { /* length/0xFF */
header_len = 1; /* length */
body_len_declared = GET_U_1(cp);
ND_PRINT(" frame flags+body (8-bit) length %" PRIu64, body_len_declared);
} else {
header_len = 1 + 8; /* 0xFF, length */
ND_PRINT(" frame flags+body (64-bit) length");
ND_TCHECK_LEN(cp, header_len); /* 0xFF, length */
body_len_declared = GET_BE_U_8(cp + 1);
ND_PRINT(" %" PRIu64, body_len_declared);
}
if (body_len_declared == 0)
return cp + header_len; /* skip to the next frame */
ND_TCHECK_LEN(cp, header_len + 1); /* ..., flags */
flags = GET_U_1(cp + header_len);
body_len_captured = ep - cp - header_len;
if (body_len_declared > body_len_captured)
ND_PRINT(" (%" PRIu64 " captured)", body_len_captured);
ND_PRINT(", flags 0x%02x", flags);
if (ndo->ndo_vflag) {
uint64_t body_len_printed = ND_MIN(body_len_captured, body_len_declared);
ND_PRINT(" (%s)", bittok2str(flags_bm, "none", flags));
if (ndo->ndo_vflag == 1)
body_len_printed = ND_MIN(VBYTES + 1, body_len_printed);
if (body_len_printed > 1) {
ND_PRINT(", first %" PRIu64 " byte(s) of body:", body_len_printed - 1);
hex_and_ascii_print(ndo, "\n\t ", cp + header_len + 1, body_len_printed - 1);
}
}
/*
* Do not advance cp by the sum of header_len and body_len_declared
* before each offset has successfully passed ND_TCHECK_LEN() as the
* sum can roll over (9 + 0xfffffffffffffff7 = 0) and cause an
* infinite loop.
*/
cp += header_len;
ND_TCHECK_LEN(cp, body_len_declared); /* Next frame within the buffer ? */
return cp + body_len_declared;
trunc:
nd_trunc_longjmp(ndo);
}
void
zmtp1_print(netdissect_options *ndo, const u_char *cp, u_int len)
{
const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
ndo->ndo_protocol = "zmtp1";
ND_PRINT(": ZMTP/1.0");
while (cp < ep)
cp = zmtp1_print_frame(ndo, cp, ep);
}
/* The functions below decode a ZeroMQ datagram, supposedly stored in the "Data"
* field of an ODATA/RDATA [E]PGM packet. An excerpt from zmq_pgm(7) man page
* follows.
*
* In order for late joining consumers to be able to identify message
* boundaries, each PGM datagram payload starts with a 16-bit unsigned integer
* in network byte order specifying either the offset of the first message frame
* in the datagram or containing the value 0xFFFF if the datagram contains
* solely an intermediate part of a larger message.
*
* Note that offset specifies where the first message begins rather than the
* first message part. Thus, if there are trailing message parts at the
* beginning of the packet the offset ignores them and points to first initial
* message part in the packet.
*/
static const u_char *
zmtp1_print_intermediate_part(netdissect_options *ndo, const u_char *cp, const u_int len)
{
u_int frame_offset;
u_int remaining_len;
frame_offset = GET_BE_U_2(cp);
ND_PRINT("\n\t frame offset 0x%04x", frame_offset);
cp += 2;
remaining_len = ND_BYTES_AVAILABLE_AFTER(cp); /* without the frame length */
if (frame_offset == 0xFFFF)
frame_offset = len - 2; /* always within the declared length */
else if (2 + frame_offset > len) {
ND_PRINT(" (exceeds datagram declared length)");
goto trunc;
}
/* offset within declared length of the datagram */
if (frame_offset) {
ND_PRINT("\n\t frame intermediate part, %u bytes", frame_offset);
if (frame_offset > remaining_len)
ND_PRINT(" (%u captured)", remaining_len);
if (ndo->ndo_vflag) {
u_int len_printed = ND_MIN(frame_offset, remaining_len);
if (ndo->ndo_vflag == 1)
len_printed = ND_MIN(VBYTES, len_printed);
if (len_printed > 1) {
ND_PRINT(", first %u byte(s):", len_printed);
hex_and_ascii_print(ndo, "\n\t ", cp, len_printed);
}
}
}
return cp + frame_offset;
trunc:
nd_trunc_longjmp(ndo);
}
void
zmtp1_datagram_print(netdissect_options *ndo, const u_char *cp, const u_int len)
{
const u_char *ep = ND_MIN(ndo->ndo_snapend, cp + len);
ndo->ndo_protocol = "zmtp1";
cp = zmtp1_print_intermediate_part(ndo, cp, len);
while (cp < ep)
cp = zmtp1_print_frame(ndo, cp, ep);
}
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