/* packet-gelf.c

 * Routines for Graylog Extended Log Format (GELF) dissection

 *

 * Slava Bacherikov <slava@bacher09.org>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/expert.h>

#include <epan/to_str.h>

#include <epan/reassemble.h>

#define HEADER_GZIP 0x1f8b

#define HEADER_CHUNKED 0x1e0f

/* not sure if this really used

seen this here: https://github.com/lusis/gelfd/blob/229cf5f1f913a35db648b195300d1aaae841d522/lib/gelfd.rb#L7 */

#define HEADER_UNCOMPRESSED 0x1f3c

#define HEADER_UNCOMPRESSED_PLAIN 0x7b22 // json payload without real header

/* minimal size of json message with only required fields */

#define MIN_PLAIN_MSG 48

#define MIN_ZLIB_MSG  46

/* make 32 bit message id from 64 bit message id */

#define BUILD_MESSAGE_ID(X) ((X[3] << 3 | X[2] << 2 | X[1] << 1 | X[0]) ^ \

                            (X[4] << 3 | X[5] << 2 | X[6] << 1 | X[7]))

void proto_register_gelf(void);

void proto_reg_handoff_gelf(void);

static dissector_handle_t json_handle;

static int proto_gelf;

static dissector_handle_t gelf_udp_handle;

static int ett_gelf;

static int hf_gelf_pdu_type;

static int hf_gelf_pdu_message_id;

static int hf_gelf_pdu_chunk_number;

static int hf_gelf_pdu_chunk_count;

static int hf_gelf_pdu_chunked;

static const value_string gelf_udp_types[] = {

    { HEADER_GZIP, "gzip" },

    { 0x7801, "zlib" },

    { 0x785e, "zlib" },

    { 0x789c, "zlib" },

    { 0x78da, "zlib" },

    { HEADER_CHUNKED, "chunked" },

    { HEADER_UNCOMPRESSED, "uncompressed" },

    { HEADER_UNCOMPRESSED_PLAIN, "uncompressed plain json" },

    { 0, NULL }

};

static reassembly_table gelf_udp_reassembly_table;

static int ett_gelf_fragment;

static int ett_gelf_fragments;

static int hf_gelf_fragments;

static int hf_gelf_fragment;

static int hf_gelf_fragment_overlap;

static int hf_gelf_fragment_overlap_conflict;

static int hf_gelf_fragment_multiple_tails;

static int hf_gelf_fragment_too_long_fragment;

static int hf_gelf_fragment_error;

static int hf_gelf_fragment_count;

static int hf_gelf_reassembled_in;

static int hf_gelf_reassembled_length;

static const fragment_items gelf_fragment_items = {

    &ett_gelf_fragment,

    &ett_gelf_fragments,

    &hf_gelf_fragments,

    &hf_gelf_fragment,

    &hf_gelf_fragment_overlap,

    &hf_gelf_fragment_overlap_conflict,

    &hf_gelf_fragment_multiple_tails,

    &hf_gelf_fragment_too_long_fragment,

    &hf_gelf_fragment_error,

    &hf_gelf_fragment_count,

    &hf_gelf_reassembled_in,

    &hf_gelf_reassembled_length,

    NULL,

    "GELF fragments"

};

static expert_field ei_gelf_invalid_header;

static expert_field ei_gelf_broken_compression;

static inline bool

is_simple_zlib(uint16_t header) {

    return header == 0x7801 || header == 0x785e || header == 0x789c || header == 0x78da;

}

static int

dissect_gelf_simple_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, uint16_t header,

                        proto_item* pdu_item)

{

    int len;

    tvbuff_t *next_tvb;

    len = tvb_captured_length(tvb);

    if (header == HEADER_GZIP || is_simple_zlib(header)) {

        next_tvb = tvb_child_uncompress_zlib(tvb, tvb, 0, len);

        if (next_tvb) {

            add_new_data_source(pinfo, next_tvb, "compressed data");

            call_dissector(json_handle, next_tvb, pinfo, tree);

        } else {

            expert_add_info_format(pinfo, pdu_item, &ei_gelf_broken_compression,

                                   "Can't uncompress message");

        }

        return len;

    } else if (header == HEADER_UNCOMPRESSED) {

        next_tvb = tvb_new_subset_remaining(tvb, 2);

        if (next_tvb) {

            call_dissector(json_handle, next_tvb, pinfo, tree);

        }

        return len;

    } else if (header == HEADER_UNCOMPRESSED_PLAIN) {

        if (call_dissector(json_handle, tvb, pinfo, tree) == 0) {

            return 0;

        }

        return len;

    }

    return 0;

}

static int

dissect_gelf(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, bool heur_check)

{

    uint16_t header;

    unsigned captured_length;

    proto_item *it;

    captured_length = tvb_captured_length(tvb);

    if (captured_length < 2)

        return 0;

    header = tvb_get_ntohs(tvb, 0);

    if (heur_check) {

        unsigned min_len;

        uint8_t number, count;

        switch(header) {

            case HEADER_GZIP:

                min_len = MIN_ZLIB_MSG;

                break;

            case HEADER_UNCOMPRESSED_PLAIN:

                min_len = MIN_PLAIN_MSG;

                break;

            case HEADER_UNCOMPRESSED:

                min_len = MIN_PLAIN_MSG + 2;

                break;

            case HEADER_CHUNKED:

                /* 10 bytes is chunked header + 2 bytes of data */

                min_len = 10 + 2;

                break;

            default:

                if (is_simple_zlib(header)) {

                    min_len = MIN_ZLIB_MSG;

                } else {

                    return 0;

                }

                break;

        }

        if (tvb_reported_length(tvb) < min_len)

            return 0;

        if (header == HEADER_CHUNKED && captured_length >= 10) {

            number = tvb_get_uint8(tvb, 10);

            count = tvb_get_uint8(tvb, 11);

            if (number >= count)

                return 0;

        }

    }

    proto_item *ti = proto_tree_add_item(tree, proto_gelf, tvb, 0, -1, ENC_NA);

    proto_tree *gelf_tree = proto_item_add_subtree(ti, ett_gelf);

    proto_item *pdu_item = proto_tree_add_item(gelf_tree, hf_gelf_pdu_type, tvb, 0, 2, ENC_BIG_ENDIAN);

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "GELF");

    if (header == HEADER_CHUNKED) {

        uint32_t number, count, short_id, data_len;

        GByteArray *bytes;

        char message_id[17];

        bool more_frags;

        fragment_head *fd_head;

        message_id[0] = '\0';

        bytes = g_byte_array_sized_new(8);

        it = proto_tree_add_boolean(gelf_tree, hf_gelf_pdu_chunked, tvb, 0, 2, true);

        proto_item_set_generated(it);

        proto_tree_add_bytes_item(gelf_tree, hf_gelf_pdu_message_id, tvb, 2, 8, ENC_BIG_ENDIAN, bytes,

                                  NULL, NULL);

        proto_tree_add_item_ret_uint(gelf_tree, hf_gelf_pdu_chunk_number, tvb, 10, 1, ENC_BIG_ENDIAN,

                                     &number);

        proto_tree_add_item_ret_uint(gelf_tree, hf_gelf_pdu_chunk_count, tvb, 11, 1, ENC_BIG_ENDIAN,

                                     &count);

        bytes_to_hexstr(message_id, bytes->data, 8);

        message_id[16] = '\0';

        // HACK: convert 64 bit message id to 32 bit :)

        short_id = BUILD_MESSAGE_ID(bytes->data);

        g_byte_array_free(bytes, true);

        col_add_fstr(pinfo->cinfo, COL_INFO, "Chunked packet: id: %s, number %u, count %u", message_id,

                     number, count);

        data_len = tvb_captured_length_remaining(tvb, 12);

        more_frags = (count == number + 1) ? false : true;

        fd_head = fragment_add_seq_check(&gelf_udp_reassembly_table, tvb, 12, pinfo, short_id, NULL, number,

                                         data_len, more_frags);

        if (fd_head != NULL) {

            tvbuff_t *newtvb;

            newtvb = process_reassembled_data(tvb, 12, pinfo, "Reassembled GELF", fd_head,

                                              &gelf_fragment_items, NULL, gelf_tree);

            if (newtvb != NULL) {

                uint16_t newheader = tvb_get_ntohs(newtvb, 0);

                dissect_gelf_simple_udp(newtvb, pinfo, tree, newheader, pdu_item);

           }

        }

        return captured_length;

    } else {

        it = proto_tree_add_boolean(gelf_tree, hf_gelf_pdu_chunked, tvb, 0, 2, false);

        proto_item_set_generated(it);

        switch(header) {

            case HEADER_GZIP:

                col_set_str(pinfo->cinfo, COL_INFO, "GZIP");

                break;

            case HEADER_UNCOMPRESSED_PLAIN:

                col_set_str(pinfo->cinfo, COL_INFO, "uncompressed plain");

                break;

            case HEADER_UNCOMPRESSED:

                col_set_str(pinfo->cinfo, COL_INFO, "uncompressed");

                break;

            default:

                if (is_simple_zlib(header)) {

                    col_set_str(pinfo->cinfo, COL_INFO, "ZLIB");

                } else {

                    expert_add_info_format(pinfo, pdu_item, &ei_gelf_invalid_header,

                                           "Invalid header magic");

                    return 0;

                }

                break;

        }

        return dissect_gelf_simple_udp(tvb, pinfo, tree, header, pdu_item);

    }

}

static int

dissect_gelf_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) {

    return dissect_gelf(tvb, pinfo, tree, false);

}

static bool

dissect_gelf_heur_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)

{

    if (dissect_gelf(tvb, pinfo, tree, true) > 0) {

        return true;

    } else {

        return false;

    }

}

void

proto_register_gelf(void)

{

    static  hf_register_info hf[] = {

        { &hf_gelf_pdu_type,

            {

                "GELF Type", "gelf.type", FT_UINT16,

                BASE_HEX, VALS(gelf_udp_types), 0x0,

                NULL, HFILL

            }

        },

        { &hf_gelf_pdu_message_id,

            {

                "Message id", "gelf.chunk.msg_id", FT_BYTES,

                BASE_NONE, NULL, 0x0,

                NULL, HFILL

            }

        },

        { &hf_gelf_pdu_chunk_number,

            {

                "Chunk number", "gelf.chunk.number", FT_UINT8,

                BASE_DEC, NULL, 0x0,

                NULL, HFILL

            }

        },

        { &hf_gelf_pdu_chunk_count,

            {

                "Chunk count", "gelf.chunk.count", FT_UINT8,

                BASE_DEC, NULL, 0x0,

                NULL, HFILL

            }

        },

        { &hf_gelf_pdu_chunked,

            {

                "Chunked message", "gelf.chunked", FT_BOOLEAN,

                BASE_NONE, NULL, 0x0,

                NULL, HFILL

            }

        }

        /* Fragmentation */,

        { &hf_gelf_fragments,

            {

                "GELF fragments", "gelf.fragments", FT_NONE, BASE_NONE,

                NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_fragment,

            {

                "GELF fragment", "gelf.fragment", FT_FRAMENUM, BASE_NONE,

                NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_fragment_overlap,

            {

                "GELF fragment overlap", "gelf.fragment.overlap", FT_BOOLEAN,

                BASE_NONE, NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_fragment_overlap_conflict,

            {

                "GELF fragment overlapping with conflicting data",

                "gelf.fragment.overlap.conflicts", FT_BOOLEAN, BASE_NONE,

                NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_fragment_multiple_tails,

            {

                "GELF has multiple tail fragments",

                "gelf.fragment.multiple_tails", FT_BOOLEAN, BASE_NONE,

                NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_fragment_too_long_fragment,

            {

                "GELF fragment too long", "gelf.fragment.too_long_fragment",

                FT_BOOLEAN, BASE_NONE, NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_fragment_error,

            {

                "GELF defragmentation error", "gelf.fragment.error", FT_FRAMENUM,

                BASE_NONE, NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_fragment_count,

            {

                "GELF fragment count", "gelf.fragment.count", FT_UINT32, BASE_DEC,

                NULL, 0x00, NULL, HFILL

            }

        },

        { &hf_gelf_reassembled_in,

            {

                "Reassembled GELF in frame", "gelf.reassembled.in", FT_FRAMENUM, BASE_NONE,

                NULL, 0x00, "This GELF packet is reassembled in this frame", HFILL

            }

        },

        { &hf_gelf_reassembled_length,

            {

                "Reassembled GELF length", "gelf.reassembled.length", FT_UINT32, BASE_DEC,

                NULL, 0x00, "The total length of the reassembled payload", HFILL

            }

        },

    };

    static ei_register_info ei_gelf[] = {

        { &ei_gelf_invalid_header,

            {

                "gelf.invalid_header", PI_MALFORMED, PI_ERROR, "Invalid header", EXPFILL

            }

        },

        { &ei_gelf_broken_compression,

            {

                "gelf.broken_compression", PI_MALFORMED, PI_ERROR, "Can't unpack message", EXPFILL

            }

        }

    };

    static int *ett[] = {

        &ett_gelf,

        &ett_gelf_fragment,

        &ett_gelf_fragments

    };

    expert_module_t *expert_gelf;

    proto_gelf = proto_register_protocol("Graylog Extended Log Format", "GELF", "gelf");

    gelf_udp_handle = register_dissector("gelf-udp", dissect_gelf_udp, proto_gelf);

    proto_register_field_array(proto_gelf, hf, array_length(hf));

    proto_register_subtree_array(ett, array_length(ett));

    expert_gelf = expert_register_protocol(proto_gelf);

    expert_register_field_array(expert_gelf, ei_gelf, array_length(ei_gelf));

    reassembly_table_register(&gelf_udp_reassembly_table, &addresses_reassembly_table_functions);

}

void

proto_reg_handoff_gelf(void)

{

    dissector_add_for_decode_as("udp.port", gelf_udp_handle);

    heur_dissector_add("udp", dissect_gelf_heur_udp,  "GELF over UDP", "gelf_udp", proto_gelf,

                       HEURISTIC_DISABLE);

    json_handle = find_dissector_add_dependency("json", proto_gelf);

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local variables:

 * c-basic-offset: 4

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * vi: set shiftwidth=4 tabstop=8 expandtab:

 * :indentSize=4:tabSize=8:noTabs=true:

 */