/*
* 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.
*/

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: print-zeromq.c,v 1.5 2024/09/02 16:15:33 christos Exp $");
#endif

/* \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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