/* packet-opus.c

 * Routines for OPUS dissection

 * Copyright 2014, Owen Williams williams.owen@gmail.com

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 */

#include "config.h"

#include "tvbuff.h"

#include <epan/packet.h>

#include <epan/prefs.h>

#include <epan/expert.h>

#include <epan/unit_strings.h>

#include <epan/tfs.h>

#include <wsutil/array.h>

#include <ftypes/ftypes.h>

#include <proto.h>

#include <stdint.h>

#define MAX_FRAMES_COUNT 48

void proto_reg_handoff_opus(void);

void proto_register_opus(void);

static dissector_handle_t opus_handle;

/* Initialize the protocol and registered fields */

static int proto_opus;

static int hf_opus_toc_config;

static int hf_opus_toc_s;

static int hf_opus_toc_c;

static int hf_opus_frame;

static int hf_opus_frame_size;

static int hf_opus_frame_count_v;

static int hf_opus_frame_count_p;

static int hf_opus_frame_count_m;

static int hf_opus_padding;

static int hf_opus_padding_size;

/* Initialize the subtree pointers */

static int ett_opus;

static expert_field ei_opus_err_r1;

static expert_field ei_opus_err_r2;

static expert_field ei_opus_err_r3;

static expert_field ei_opus_err_r4;

static expert_field ei_opus_err_r5;

static expert_field ei_opus_err_r6;

static expert_field ei_opus_err_r7;

static expert_field ei_opus_padding_nonzero;

/* From RFC6716 chapter 3.1

 * The top five bits of the TOC byte, labeled "config", encode one of 32

 * possible configurations of operating mode, audio bandwidth, and frame size.

 */

static const value_string opus_codec_toc_config_request_vals[] = {

    {0, "NB, SILK-only ptime=10"},

    {1, "NB, SILK-only ptime=20"},

    {2, "NB, SILK-only ptime=40"},

    {3, "NB, SILK-only ptime=60"},

    {4, "MB, SILK-only ptime=10"},

    {5, "MB, SILK-only ptime=20"},

    {6, "MB, SILK-only ptime=40"},

    {7, "MB, SILK-only ptime=60"},

    {8, "WB, SILK-only ptime=10"},

    {9, "WB, SILK-only ptime=20"},

    {10, "WB, SILK-only ptime=40"},

    {11, "WB, SILK-only ptime=60"},

    {12, "SWB, Hybrid ptime=10"},

    {13, "SWB, Hybrid ptime=20"},

    {14, "FB, Hybrid ptime=10"},

    {15, "FB, Hybrid ptime=20"},

    {16, "NB, CELT-only ptime=2.5"},

    {17, "NB, CELT-only ptime=5"},

    {18, "NB, CELT-only ptime=10"},

    {19, "NB, CELT-only ptime=20"},

    {20, "WB, CELT-only ptime=2.5"},

    {21, "WB, CELT-only ptime=5"},

    {22, "WB, CELT-only ptime=10"},

    {23, "WB, CELT-only ptime=20"},

    {24, "SWB, CELT-only ptime=2.5"},

    {25, "SWB, CELT-only ptime=5"},

    {26, "SWB, CELT-only ptime=10"},

    {27, "SWB, CELT-only ptime=20"},

    {28, "FB, CELT-only ptime=2.5"},

    {29, "FB, CELT-only ptime=5"},

    {30, "FB, CELT-only ptime=10"},

    {31, "FB, CELT-only ptime=20"},

    {0, NULL}};

static value_string_ext opus_codec_toc_config_request_vals_ext

    = VALUE_STRING_EXT_INIT(opus_codec_toc_config_request_vals);

static const true_false_string toc_s_bit_vals = {"stereo", "mono"};

static const true_false_string fc_v_bit_vals = {"VBR", "CBR"};

static const true_false_string fc_p_bit_vals = {"Padding", "No Padding"};

static const value_string opus_codec_toc_c_request_vals[]

    = {{0, "1 frame in the packet"},

       {1, "2 frames in the packet, each with equal compressed size"},

       {2, "2 frames in the packet, with different compressed sizes"},

       {3, "an arbitrary number of frames in the packet"},

       {0, NULL}};

static value_string_ext opus_codec_toc_c_request_vals_ext

    = VALUE_STRING_EXT_INIT(opus_codec_toc_c_request_vals);

static int

parse_size_field(const unsigned char *ch, int32_t cn, int16_t *size)

{

    if (cn < 1) {

        *size = -1;

        return -1;

    }

    else if (ch[0] < 252) {

        *size = ch[0];

        return 1;

    }

    else if (cn < 2) {

        *size = -1;

        return -1;

    }

    else {

        *size = 4 * ch[1] + ch[0];

        return 2;

    }

}

static int16_t

opus_packet_get_samples_per_frame(const unsigned char *data, uint16_t Fs)

{

    int audiosize;

    if (data[0] & 0x80) {

        audiosize = ((data[0] >> 3) & 0x3);

        audiosize = (Fs << audiosize) / 400;

    }

    else if ((data[0] & 0x60) == 0x60) {

        audiosize = (data[0] & 0x08) ? Fs / 50 : Fs / 100;

    }

    else {

        audiosize = ((data[0] >> 3) & 0x3);

        if (audiosize == 3)

            audiosize = Fs * 60 / 1000;

        else

            audiosize = (Fs << audiosize) / 100;

    }

    return audiosize;

}

static int

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

{

    int idx;

    proto_item *item;

    proto_tree *opus_tree;

    int pkt_total = 0, offset = 0;

    unsigned cap_len = 0;

    uint8_t ch = 0, toc = 0, octet[2] = {0, 0};

    int octet_cnt = 0;

    int bytes = 0;

    int16_t framesize = 0;

    struct FRAME_T {

        int16_t begin;

        int16_t size;

    } frames[MAX_FRAMES_COUNT] = {{0}};

    int frame_count = 0;

    static int *toc_fields[]

        = {&hf_opus_toc_config, &hf_opus_toc_s, &hf_opus_toc_c, NULL};

    static int *frame_count_fields[]

        = {&hf_opus_frame_count_v, &hf_opus_frame_count_p,

        &hf_opus_frame_count_m, NULL};

    int padding_size = 0;

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

    item = proto_tree_add_item(tree, proto_opus, tvb, 0, -1, ENC_NA);

    opus_tree = proto_item_add_subtree(item, ett_opus);

    /*

     *  A ToC entry takes the following format, details defined in section-3.1:

     *

     *    0 1 2 3 4 5 6 7

     *   +-+-+-+-+-+-+-+-+

     *   | config  |s| c |

     *   +-+-+-+-+-+-+-+-+

     */

    proto_tree_add_bitmask_list(opus_tree, tvb, offset, 1, toc_fields, ENC_NA);

    cap_len = tvb_captured_length(tvb);

    pkt_total = tvb_reported_length_remaining(tvb, offset);

    if (pkt_total <= 0) {

        expert_add_info(pinfo, opus_tree, &ei_opus_err_r1);

        return cap_len;

    }

    toc = tvb_get_uint8(tvb, offset++);

    switch (toc & 0x3) {

    case 0: /* One frame */

        frames[0].begin = offset;

        frames[0].size = pkt_total - offset;

        frame_count = 1;

        break;

    case 1: /* Two CBR frames */

        if ((pkt_total - offset) & 0x1) {

            expert_add_info(pinfo, opus_tree, &ei_opus_err_r3);

            return cap_len;

        }

        frames[0].begin = offset;

        frames[0].size = frames[1].size = (pkt_total - offset) / 2;

        frames[1].begin = frames[0].begin + frames[0].size;

        frame_count = 2;

        break;

    case 2: /* Two VBR frames */

        if (offset >= pkt_total) {

            expert_add_info(pinfo, opus_tree, &ei_opus_err_r4);

            return cap_len;

        }

        /* offset < pkt_total */

        octet[octet_cnt++] = tvb_get_uint8(tvb, offset);

        if (offset + 1 < pkt_total) {

            octet[octet_cnt++] = tvb_get_uint8(tvb, offset + 1);

        }

        bytes = parse_size_field(octet, octet_cnt, &framesize);

        if (framesize < 0 || framesize > pkt_total) {

            expert_add_info(pinfo, opus_tree, &ei_opus_err_r1);

            return cap_len;

        }

        proto_tree_add_uint(opus_tree, hf_opus_frame_size, tvb, offset, bytes,

                            framesize);

        offset += bytes;

        /* frame[0] has size header, frame[1] is remaining */

        frames[0].begin = offset;

        frames[0].size = framesize;

        frames[1].begin = frames[0].begin + framesize;

        frames[1].size = -1;

        frame_count = 2;

        break;

    /* Multiple CBR/VBR frames (from 0 to 120 ms) */

    default: /* case 3:*/

        if ((pkt_total - offset) < 1) {

            expert_add_info(pinfo, opus_tree, &ei_opus_err_r6);

            return cap_len;

        }

        proto_tree_add_bitmask_list(opus_tree, tvb, offset, 1,

                                    frame_count_fields, ENC_NA);

        /* Number of frames encoded in bits 0 to 5 */

        ch = tvb_get_uint8(tvb, offset++);

        frame_count = ch & 0x3F;

        framesize = opus_packet_get_samples_per_frame(&toc, 48000U);

        if (frame_count <= 0

            || framesize * frame_count > 120 * MAX_FRAMES_COUNT) {

            expert_add_info(pinfo, opus_tree, &ei_opus_err_r5);

            return cap_len;

        }

        /* The smallest value the function above can return is 120, so

         * the below holds (but make it obvious). */

        ws_assert(frame_count <= MAX_FRAMES_COUNT);

        /* Padding flag (bit 6) used */

        if (ch & 0x40) {

            int p;

            int padding_begin = offset;

            do {

                int tmp;

                if (offset >= pkt_total) {

                    expert_add_info(pinfo, opus_tree, &ei_opus_err_r7);

                    return cap_len;

                }

                p = tvb_get_uint8(tvb, offset++);

                tmp = p == 255 ? 254 : p;

                padding_size += tmp;

            } while (p == 255);

            proto_tree_add_uint(opus_tree, hf_opus_padding_size, tvb,

                                padding_begin, offset - padding_begin,

                                padding_size);

            /* This padding size is the number of padding bytes at the

             * end of the packets "in addition to the byte(s) used to

             * indicate the size of the padding."

             */

            pkt_total -= padding_size;

        }

        /* VBR flag is bit 7 */

        if (ch & 0x80) { /* VBR case */

            for (idx = 0; idx < frame_count - 1; idx++) {

                if (offset >= pkt_total) {

                    expert_add_info(pinfo, opus_tree, &ei_opus_err_r7);

                    return cap_len;

                }

                octet_cnt = 0;

                octet[octet_cnt++] = tvb_get_uint8(tvb, offset);

                if (offset + 1 < pkt_total) {

                    octet[octet_cnt++] = tvb_get_uint8(tvb, offset);

                }

                bytes = parse_size_field(octet, octet_cnt, &frames[idx].size);

                if (frames[idx].size < 0

                    || frames[idx].size > (pkt_total - offset)) {

                    expert_add_info(pinfo, opus_tree, &ei_opus_err_r1);

                    return cap_len;

                }

                proto_tree_add_uint(opus_tree, hf_opus_frame_size, tvb, offset,

                                    bytes, frames[idx].size);

                offset += bytes;

            }

            for (idx = 0; idx < frame_count - 1; idx++) {

                frames[idx].begin = offset;

                offset += frames[idx].size;

            }

            if (offset > pkt_total) {

                expert_add_info(pinfo, opus_tree, &ei_opus_err_r7);

                return cap_len;

            }

            frames[idx].begin = offset;

            frames[idx].size = pkt_total - offset;

        }

        else { /* CBR case */

            if (offset > pkt_total) {

                expert_add_info(pinfo, opus_tree, &ei_opus_err_r6);

                return cap_len;

            }

            unsigned frame_size = (pkt_total - offset) / frame_count;

            if (frame_size * frame_count != (unsigned)(pkt_total - offset)) {

                expert_add_info(pinfo, opus_tree, &ei_opus_err_r6);

                return cap_len;

            }

            for (idx = 0; idx < frame_count; idx++) {

                frames[idx].begin = offset + idx * frame_size;

                frames[idx].size = frame_size;

            }

        }

        break;

    }

    for (idx = 0; idx < frame_count; idx++) {

        struct FRAME_T *f = &frames[idx];

        /* reject the frame which is larger than 1275. */

        if (f->size > 1275) {

            expert_add_info(pinfo, opus_tree, &ei_opus_err_r2);

            return cap_len;

        }

        proto_tree_add_item(opus_tree, hf_opus_frame, tvb, f->begin, f->size,

                            ENC_NA);

    }

    if (padding_size) {

        int padding_begin = tvb_reported_length(tvb) - padding_size;

        item = proto_tree_add_item(opus_tree, hf_opus_padding, tvb,

                                   padding_begin, padding_size, ENC_NA);

        /* RFC 6716: "The additional padding bytes appear at the end

         * of the packet and MUST be set to zero by the encoder to avoid

         * creating a covert channel."

         */

        for (int i = 0; i < padding_size; ++i) {

            if (tvb_get_uint8(tvb, padding_begin + i) != 0) {

                expert_add_info(pinfo, item, &ei_opus_padding_nonzero);

                break;

            }

        }

    }

    return cap_len;

}

void

proto_register_opus(void)

{

    module_t *opus_module;

    expert_module_t* expert_opus;

    static hf_register_info hf[] = {

        {&hf_opus_toc_config,

         {"TOC.config", "opus.TOC.config", FT_UINT8, BASE_DEC | BASE_EXT_STRING,

          &opus_codec_toc_config_request_vals_ext, 0xF8, "Opus TOC config",

          HFILL}},

        {&hf_opus_toc_s,

         {"TOC.S bit", "opus.TOC.s", FT_BOOLEAN, 8, TFS(&toc_s_bit_vals),

          0x04, NULL, HFILL}},

        {&hf_opus_toc_c,

         {"TOC.C bits", "opus.TOC.c", FT_UINT8, BASE_DEC | BASE_EXT_STRING,

          &opus_codec_toc_c_request_vals_ext, 0x03, "Opus TOC code", HFILL}},

        {&hf_opus_frame_count_m,

         {"Frame Count.m", "opus.FC.m", FT_UINT8, BASE_DEC, NULL, 0x3F,

          "Frame Count", HFILL}},

        {&hf_opus_frame_count_p,

         {"Frame Count.p bit", "opus.FC.p", FT_BOOLEAN, 8,

          TFS(&fc_p_bit_vals), 0x40, NULL, HFILL}},

        {&hf_opus_frame_count_v,

         {"Frame Count.v bit", "opus.FC.v", FT_BOOLEAN, 8,

          TFS(&fc_v_bit_vals), 0x80, NULL, HFILL}},

        {&hf_opus_frame_size,

         {"Frame Size", "opus.frame_size", FT_UINT16, BASE_DEC | BASE_UNIT_STRING,

          UNS(&units_byte_bytes), 0x0, NULL, HFILL}},

        {&hf_opus_frame,

         {"Frame Data", "opus.frame_data", FT_BYTES, BASE_NONE | BASE_ALLOW_ZERO,

          NULL, 0x0, NULL, HFILL}},

        {&hf_opus_padding,

         {"Padding", "opus.padding", FT_BYTES, BASE_NONE, NULL, 0x0, NULL,

          HFILL}},

        {&hf_opus_padding_size,

         {"Padding Size", "opus.padding_size", FT_UINT32, BASE_DEC, NULL, 0x0,

          "Additional padding bytes, not including the bytes indicating the padding size",

          HFILL}},

    };

    static int *ett[] = { &ett_opus, };

    static ei_register_info ei[] = {

        {&ei_opus_err_r1,

         {"opus.violate_r1", PI_PROTOCOL, PI_ERROR,

          "Error:[R1] Packets are at least one byte.", EXPFILL}},

        {&ei_opus_err_r2,

         {"opus.violate_r2", PI_MALFORMED, PI_ERROR,

          "Error:[R2] No implicit frame length is larger than 1275 bytes.",

          EXPFILL}},

        {&ei_opus_err_r3,

         {"opus.violate_r3", PI_MALFORMED, PI_ERROR,

          "Error:[R3] Code 1 packets have an odd total length, N, so that "

          "(N-1)/2 is an integer.",

          EXPFILL}},

        {&ei_opus_err_r4,

         {"opus.violate_r4", PI_MALFORMED, PI_ERROR,

          "Error:[R4] Code 2 packets have enough bytes after the TOC for a "

          "valid frame length, and that length is no larger than the number of"

          "bytes remaining in the packet.",

          EXPFILL}},

        {&ei_opus_err_r5,

         {"opus.violate_r5", PI_PROTOCOL, PI_ERROR,

          "Error:[R5] Code 3 packets contain at least one frame, but no more "

          "than 120 ms of audio total.",

          EXPFILL}},

        {&ei_opus_err_r6,

         {"opus.violate_r6", PI_PROTOCOL, PI_ERROR,

          "Error:[R6] The length of a CBR code 3 packet, N, is at least two "

          "bytes, the number of bytes added to indicate the padding size plus "

          "the trailing padding bytes themselves, P, is no more than N-2, and "

          "the frame count, M, satisfies the constraint that (N-2-P) is a "

          "non-negative integer multiple of M.",

          EXPFILL}},

        {&ei_opus_err_r7,

         {"opus.violate_r7", PI_PROTOCOL, PI_ERROR,

          "Error:[R7] VBR code 3 packets are large enough to contain all the "

          "header bytes (TOC byte, frame count byte, any padding length bytes, "

          "and any frame length bytes), plus the length of the first M-1 "

          "frames, plus any trailing padding bytes.",

          EXPFILL}},

        {&ei_opus_padding_nonzero,

         {"opus.padding.nonzero", PI_PROTOCOL, PI_WARN,

          "Additional padding bytes MUST be set to zero by the encoder",

          EXPFILL}},

    };

    proto_opus = proto_register_protocol("Opus Interactive Audio Codec", "OPUS", "opus"); /* name, short name, abbreviation */

    proto_register_field_array(proto_opus, hf, array_length(hf));

    proto_register_subtree_array(ett, array_length(ett));

    opus_module = prefs_register_protocol(proto_opus, NULL);

    expert_opus = expert_register_protocol(proto_opus);

    expert_register_field_array(expert_opus, ei, array_length(ei));

    prefs_register_obsolete_preference(opus_module, "dynamic.payload.type");

    opus_handle = register_dissector("opus", dissect_opus, proto_opus);

}

void

proto_reg_handoff_opus(void)

{

    dissector_add_string("rtp_dyn_payload_type" , "OPUS", opus_handle);

    dissector_add_uint_range_with_preference("rtp.pt", "", opus_handle);

}

/*

 * 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:

 */