/* decode_as.c

 * Routines for dissector Decode As handlers

 *

 * 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 <glib.h>

#include "decode_as.h"

#include <epan/packet.h>

#include "prefs.h"

#include "prefs-int.h"

#include "wsutil/file_util.h"

#include "wsutil/filesystem.h"

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <wsutil/ws_assert.h>

GList *decode_as_list;

void register_decode_as(decode_as_t* reg)

{

    dissector_table_t decode_table;

    /* Ensure valid functions */

    ws_assert(reg->populate_list);

    ws_assert(reg->reset_value);

    ws_assert(reg->change_value);

    decode_table = find_dissector_table(reg->table_name);

    if (decode_table != NULL)

    {

        dissector_table_allow_decode_as(decode_table);

    }

    decode_as_list = g_list_prepend(decode_as_list, reg);

}

static void next_proto_prompt(packet_info *pinfo _U_, char *result)

{

    snprintf(result, MAX_DECODE_AS_PROMPT_LEN, "Next level protocol as");

}

static void *next_proto_value(packet_info *pinfo _U_)

{

    return 0;

}

static build_valid_func next_proto_values[] = { next_proto_value };

static decode_as_value_t next_proto_da_values =

                        { next_proto_prompt, 1, next_proto_values };

dissector_table_t register_decode_as_next_proto(int proto, const char *table_name, const char *ui_name, build_label_func label_func)

{

    decode_as_t *da;

    dissector_table_t dt = register_dissector_table(table_name, ui_name, proto, FT_NONE, BASE_NONE);

    da = wmem_new0(wmem_epan_scope(), decode_as_t);

    da->name = wmem_strdup(wmem_epan_scope(), proto_get_protocol_filter_name(proto));

    da->table_name = wmem_strdup(wmem_epan_scope(), table_name);

    da->num_items = 1;

    if (label_func == NULL)

    {

        da->values = &next_proto_da_values;

    }

    else

    {

        da->values = wmem_new(wmem_epan_scope(), decode_as_value_t);

        da->values->label_func = label_func;

        da->values->num_values = 1;

        da->values->build_values = next_proto_values;

    }

    da->populate_list = decode_as_default_populate_list;

    da->reset_value = decode_as_default_reset;

    da->change_value = decode_as_default_change;

    register_decode_as(da);

    return dt;

}

struct decode_as_default_populate

{

    decode_as_add_to_list_func add_to_list;

    void *ui_element;

};

static void

decode_proto_add_to_list (const char *table_name, void *value, void *user_data)

{

    struct decode_as_default_populate* populate = (struct decode_as_default_populate*)user_data;

    const char      *dissector_description;

    int        i;

    dissector_handle_t handle;

    handle = (dissector_handle_t)value;

    dissector_description = dissector_handle_get_description(handle);

    i = dissector_handle_get_protocol_index(handle);

    if (i >= 0 && !proto_is_protocol_enabled(find_protocol_by_id(i)))

        return;

    populate->add_to_list(table_name, dissector_description, value, populate->ui_element);

}

void decode_as_default_populate_list(const char *table_name, decode_as_add_to_list_func add_to_list, void *ui_element)

{

    struct decode_as_default_populate populate;

    populate.add_to_list = add_to_list;

    populate.ui_element = ui_element;

    dissector_table_foreach_handle(table_name, decode_proto_add_to_list, &populate);

}

bool decode_as_default_reset(const char *name, const void *pattern)

{

    switch (get_dissector_table_selector_type(name)) {

    case FT_UINT8:

    case FT_UINT16:

    case FT_UINT24:

    case FT_UINT32:

        dissector_reset_uint(name, GPOINTER_TO_UINT(pattern));

        return true;

    case FT_NONE:

        dissector_reset_payload(name);

        return true;

    case FT_STRING:

    case FT_STRINGZ:

    case FT_UINT_STRING:

    case FT_STRINGZPAD:

    case FT_STRINGZTRUNC:

        dissector_reset_string(name, (!pattern)?"":(const char *) pattern);

        return true;

    default:

        return false;

    };

    return true;

}

bool decode_as_default_change(const char *name, const void *pattern, const void *handle, const char *list_name _U_)

{

    const dissector_handle_t dissector = (const dissector_handle_t)handle;

    switch (get_dissector_table_selector_type(name)) {

    case FT_UINT8:

    case FT_UINT16:

    case FT_UINT24:

    case FT_UINT32:

        dissector_change_uint(name, GPOINTER_TO_UINT(pattern), dissector);

        return true;

    case FT_NONE:

        dissector_change_payload(name, dissector);

        return true;

    case FT_STRING:

    case FT_STRINGZ:

    case FT_UINT_STRING:

    case FT_STRINGZPAD:

    case FT_STRINGZTRUNC:

        dissector_change_string(name, (!pattern)?"":(const char *) pattern, dissector);

        return true;

    default:

        return false;

    };

    return true;

}

/* Some useful utilities for Decode As */

/*

 * A list of dissectors that need to be reset.

 */

static GSList *dissector_reset_list;

/*

 * A callback function to parse each "decode as" entry in the file and apply the change

 */

static prefs_set_pref_e

read_set_decode_as_entries(char *key, const char *value,

                           void *user_data,

                           bool return_range_errors _U_)

{

    char *values[4] = {NULL, NULL, NULL, NULL};

    char delimiter[4] = {',', ',', ',','\0'};

    char *pch;

    unsigned i, j;

    GHashTable* processed_entries = (GHashTable*)user_data;

    dissector_table_t sub_dissectors;

    prefs_set_pref_e retval = PREFS_SET_OK;

    bool is_valid = false;

    if (strcmp(key, DECODE_AS_ENTRY) == 0) {

        /* Parse csv into table, selector, initial, current */

        for (i = 0; i < 4; i++) {

            pch = strchr(value, delimiter[i]);

            if (pch == NULL) {

                for (j = 0; j < i; j++) {

                    g_free(values[j]);

                }

                return PREFS_SET_SYNTAX_ERR;

            }

            values[i] = g_strndup(value, pch - value);

            value = pch + 1;

        }

        sub_dissectors = find_dissector_table(values[0]);

        if (sub_dissectors != NULL) {

            dissector_handle_t handle;

            ftenum_t selector_type;

            pref_t* pref_value;

            module_t *module;

            const char* proto_name;

            selector_type = dissector_table_get_type(sub_dissectors);

            handle = dissector_table_get_dissector_handle(sub_dissectors, values[3]);

            if (handle != NULL || g_ascii_strcasecmp(values[3], DECODE_AS_NONE) == 0) {

                is_valid = true;

            }

            if (is_valid) {

                if (FT_IS_STRING(selector_type)) {

                    dissector_change_string(values[0], values[1], handle);

                } else {

                    char *p;

                    long long_value;

                    long_value = strtol(values[1], &p, 0);

                    if (p == values[0] || *p != '\0' || long_value < 0 ||

                          (unsigned long)long_value > UINT_MAX) {

                        retval = PREFS_SET_SYNTAX_ERR;

                        is_valid = false;

                    } else {

                        dissector_change_uint(values[0], (unsigned)long_value, handle);

                    }

                    /* Now apply the value data back to dissector table preference */

                    if (handle != NULL) {

                        proto_name = proto_get_protocol_filter_name(dissector_handle_get_protocol_index(handle));

                        module = prefs_find_module(proto_name);

                        // values[0] is the dissector table

                        char *pref_name = ws_strdup_printf("%s%s", values[0], dissector_handle_get_pref_suffix(handle));

                        pref_value = prefs_find_preference(module, pref_name);

                        g_free(pref_name);

                        if (pref_value != NULL) {

                            bool replace = false;

                            if (g_hash_table_lookup(processed_entries, proto_name) == NULL) {

                                /* First decode as entry for this protocol, ranges may be replaced */

                                replace = true;

                                /* Remember we've processed this protocol */

                                g_hash_table_insert(processed_entries, (void *)proto_name, (void *)proto_name);

                            }

                            prefs_add_decode_as_value(pref_value, (unsigned)long_value, replace);

                            module->prefs_changed_flags |= prefs_get_effect_flags(pref_value);

                        }

                    }

                }

            }

            if (is_valid) {

                decode_build_reset_list(values[0], selector_type, values[1], NULL, NULL);

            }

        } else {

            retval = PREFS_SET_SYNTAX_ERR;

        }

    } else {

        retval = PREFS_SET_NO_SUCH_PREF;

    }

    for (i = 0; i < 4; i++) {

        g_free(values[i]);

    }

    return retval;

}

void

load_decode_as_entries(const char* app_env_var_prefix)

{

    char   *daf_path;

    FILE   *daf;

    decode_clear_all();

    daf_path = get_persconffile_path(DECODE_AS_ENTRIES_FILE_NAME, true, app_env_var_prefix);

    if ((daf = ws_fopen(daf_path, "r")) != NULL) {

        /* Store saved entries for better range processing */

        GHashTable* processed_entries = g_hash_table_new(g_str_hash, g_str_equal);

        read_prefs_file(daf_path, daf, read_set_decode_as_entries, processed_entries);

        g_hash_table_destroy(processed_entries);

        fclose(daf);

    }

    g_free(daf_path);

}

/* Make a sorted list of the entries as we are fetching them from a hash table. Then write it out from the sorted list */

static void

decode_as_write_entry (const char *table_name, ftenum_t selector_type,

                       void *key, void *value, void *user_data)

{

    GList **decode_as_rows_list = (GList **)user_data;

    dissector_handle_t current, initial;

    const char *current_dissector_name, *initial_dissector_name, *decode_as_row;

    current = dtbl_entry_get_handle((dtbl_entry_t *)value);

    if (current == NULL)

        current_dissector_name = DECODE_AS_NONE;

    else

        current_dissector_name = dissector_handle_get_description(current);

    initial = dtbl_entry_get_initial_handle((dtbl_entry_t *)value);

    if (initial == NULL)

        initial_dissector_name = DECODE_AS_NONE;

    else

        initial_dissector_name = dissector_handle_get_description(initial);

    switch (selector_type) {

    case FT_UINT8:

    case FT_UINT16:

    case FT_UINT24:

    case FT_UINT32:

        /*

         * XXX - write these in decimal, regardless of the base of

         * the dissector table's selector, as older versions of

         * Wireshark used atoi() when reading this file, and

         * failed to handle hex or octal numbers.

         *

         * That will be fixed in future 1.10 and 1.12 releases,

         * but pre-1.10 releases are at end-of-life and won't

         * be fixed.

         */

        decode_as_row = ws_strdup_printf(

            DECODE_AS_ENTRY ": %s,%u,%s,%s\n",

            table_name, GPOINTER_TO_UINT(key), initial_dissector_name,

            current_dissector_name);

        break;

    case FT_NONE:

        /*

         * XXX - Just put a placeholder for the key value.  Currently

         * FT_NONE dissector table uses a single uint value for

         * a placeholder

         */

        decode_as_row = ws_strdup_printf(

            DECODE_AS_ENTRY ": %s,0,%s,%s\n",

            table_name, initial_dissector_name,

            current_dissector_name);

        break;

    case FT_STRING:

    case FT_STRINGZ:

    case FT_UINT_STRING:

    case FT_STRINGZPAD:

    case FT_STRINGZTRUNC:

        decode_as_row = ws_strdup_printf(

            DECODE_AS_ENTRY ": %s,%s,%s,%s\n",

            table_name, (char *)key, initial_dissector_name,

            current_dissector_name);

        break;

    default:

        ws_assert_not_reached();

        break;

    }

    /* Do we need a better sort function ???*/

    *decode_as_rows_list = g_list_insert_sorted (*decode_as_rows_list, (void *)decode_as_row,

        (GCompareFunc)g_ascii_strcasecmp);

}

/* Print the sorted rows to File */

static void

decode_as_print_rows(void *data, void *user_data)

{

    FILE *da_file = (FILE *)user_data;

    const char *decode_as_row = (const char *)data;

    fprintf(da_file, "%s",decode_as_row);

}

int

save_decode_as_entries(const char* app_name, const char* app_env_var_prefix, char** err)

{

    char *pf_dir_path;

    char *daf_path;

    FILE *da_file;

    GList *decode_as_rows_list = NULL;

    if (create_persconffile_dir(app_env_var_prefix, &pf_dir_path) == -1) {

        *err = ws_strdup_printf("Can't create directory\n\"%s\"\nfor recent file: %s.",

                                pf_dir_path, g_strerror(errno));

        g_free(pf_dir_path);

        return -1;

    }

    daf_path = get_persconffile_path(DECODE_AS_ENTRIES_FILE_NAME, true, app_env_var_prefix);

    if ((da_file = ws_fopen(daf_path, "w")) == NULL) {

        *err = ws_strdup_printf("Can't open decode_as_entries file\n\"%s\": %s.",

                                daf_path, g_strerror(errno));

        g_free(daf_path);

        return -1;

    }

    fprintf(da_file, "# \"Decode As\" entries file for %s " VERSION ".\n"

        "#\n"

        "# This file is regenerated each time \"Decode As\" preferences\n"

        "# are saved within %s. Making manual changes should be safe,\n"

        "# however.\n",

        app_name, app_name);

    dissector_all_tables_foreach_changed(decode_as_write_entry, &decode_as_rows_list);

    g_list_foreach(decode_as_rows_list, decode_as_print_rows, da_file);

    fclose(da_file);

    g_free(daf_path);

    g_list_free_full(decode_as_rows_list, g_free);

    return 0;

}

/*

 * Data structure for tracking which dissector need to be reset.  This

 * structure is necessary as a hash table entry cannot be removed

 * while a g_hash_table_foreach walk is in progress.

 */

typedef struct dissector_delete_item {

    /* The name of the dissector table */

    char *ddi_table_name;

    /* The type of the selector in that dissector table */

    ftenum_t ddi_selector_type;

    /* The selector in the dissector table */

    union {

        unsigned   sel_uint;

        char    *sel_string;

    } ddi_selector;

} dissector_delete_item_t;

void

decode_build_reset_list (const char *table_name, ftenum_t selector_type,

                         void *key, void *value _U_,

                         void *user_data _U_)

{

    dissector_delete_item_t *item;

    item = g_new(dissector_delete_item_t,1);

    item->ddi_table_name = g_strdup(table_name);

    item->ddi_selector_type = selector_type;

    switch (selector_type) {

    case FT_UINT8:

    case FT_UINT16:

    case FT_UINT24:

    case FT_UINT32:

        item->ddi_selector.sel_uint = GPOINTER_TO_UINT(key);

        break;

    case FT_NONE:

        /* Not really needed, but prevents the assert */

        item->ddi_selector.sel_uint = 0;

        break;

    case FT_STRING:

    case FT_STRINGZ:

    case FT_UINT_STRING:

    case FT_STRINGZPAD:

    case FT_STRINGZTRUNC:

        item->ddi_selector.sel_string = g_strdup((char *)key);

        break;

    default:

        ws_assert_not_reached();

    }

    dissector_reset_list = g_slist_prepend(dissector_reset_list, item);

}

/* clear all settings */

void

decode_clear_all(void)

{

    dissector_delete_item_t *item;

    GSList *tmp;

    dissector_all_tables_foreach_changed(decode_build_reset_list, NULL);

    for (tmp = dissector_reset_list; tmp; tmp = g_slist_next(tmp)) {

        item = (dissector_delete_item_t *)tmp->data;

        switch (item->ddi_selector_type) {

        case FT_UINT8:

        case FT_UINT16:

        case FT_UINT24:

        case FT_UINT32:

            dissector_reset_uint(item->ddi_table_name,

                                 item->ddi_selector.sel_uint);

            break;

        case FT_NONE:

            dissector_reset_payload(item->ddi_table_name);

            break;

        case FT_STRING:

        case FT_STRINGZ:

        case FT_UINT_STRING:

        case FT_STRINGZPAD:

        case FT_STRINGZTRUNC:

            dissector_reset_string(item->ddi_table_name,

                                   item->ddi_selector.sel_string);

            g_free(item->ddi_selector.sel_string);

            break;

        default:

            ws_assert_not_reached();

        }

        g_free(item->ddi_table_name);

        g_free(item);

    }

    g_slist_free(dissector_reset_list);

    dissector_reset_list = NULL;

    for (GList* cur = decode_as_list; cur; cur = cur->next) {

        decode_as_t* entry = (decode_as_t*)cur->data;

        if (entry->reset_all != NULL) {

            entry->reset_all();

        }

    }

}

void

decode_cleanup(void)

{

    g_list_free(decode_as_list);

    decode_as_list = NULL;

}

/*

 * Editor modelines

 *

 * Local Variables:

 * c-basic-offset: 4

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

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

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

 */