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wireshark/ui/decode_as_utils.c

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/* decode_as_utils.c
*
* Routines to modify dissector tables on the fly.
*
* By David Hampton <dhampton@mac.com>
* Copyright 2001 David Hampton
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <stdlib.h>
#include <errno.h>
#include "epan/decode_as.h"
#include "epan/packet.h"
#include "epan/prefs.h"
#include "epan/prefs-int.h"
#include "ui/decode_as_utils.h"
#include "ui/simple_dialog.h"
#include "wsutil/file_util.h"
#include "wsutil/filesystem.h"
#include <wsutil/ws_assert.h>
#include "wsutil/cmdarg_err.h"
/* XXX - We might want to switch this to a UAT */
static const char* prev_display_dissector_name = NULL;
/*
* For a dissector table, print on the stream described by output,
* its short name (which is what's used in the "-d" option) and its
* descriptive name.
*/
static void
display_dissector_table_names(const char *table_name, const char *ui_name,
gpointer output)
{
if ((prev_display_dissector_name == NULL) ||
(strcmp(prev_display_dissector_name, table_name) != 0)) {
fprintf((FILE *)output, "\t%s (%s)\n", table_name, ui_name);
prev_display_dissector_name = table_name;
}
}
/*
* For a dissector handle, print on the stream described by output,
* the filter name (which is what's used in the "-d" option) and the full
* name for the protocol that corresponds to this handle.
*/
static void
display_dissector_names(const gchar *table _U_, gpointer handle, gpointer output)
{
int proto_id;
const gchar *proto_filter_name;
const gchar *proto_ui_name;
proto_id = dissector_handle_get_protocol_index((dissector_handle_t)handle);
if (proto_id != -1) {
proto_filter_name = proto_get_protocol_filter_name(proto_id);
proto_ui_name = proto_get_protocol_name(proto_id);
ws_assert(proto_filter_name != NULL);
ws_assert(proto_ui_name != NULL);
if ((prev_display_dissector_name == NULL) ||
(strcmp(prev_display_dissector_name, proto_filter_name) != 0)) {
fprintf((FILE *)output, "\t%s (%s)\n",
proto_filter_name,
proto_ui_name);
prev_display_dissector_name = proto_filter_name;
}
}
}
/*
* Allow dissector key names to be sorted alphabetically
*/
static gint
compare_dissector_key_name(gconstpointer dissector_a, gconstpointer dissector_b)
{
return strcmp((const char*)dissector_a, (const char*)dissector_b);
}
/*
* Print all layer type names supported.
* We send the output to the stream described by the handle output.
*/
static void
fprint_all_layer_types(FILE *output)
{
prev_display_dissector_name = NULL;
dissector_all_tables_foreach_table(display_dissector_table_names, (gpointer)output, (GCompareFunc)compare_dissector_key_name);
}
/*
* Print all protocol names supported for a specific layer type.
* table_name contains the layer type name in which the search is performed.
* We send the output to the stream described by the handle output.
*/
static void
fprint_all_protocols_for_layer_types(FILE *output, gchar *table_name)
{
prev_display_dissector_name = NULL;
dissector_table_foreach_handle(table_name,
display_dissector_names,
(gpointer)output);
}
/*
* The protocol_name_search structure is used by find_protocol_name_func()
* to pass parameters and store results
*/
struct protocol_name_search{
const char *searched_name; /* Protocol filter name we are looking for */
dissector_handle_t matched_handle; /* Handle for a dissector whose protocol has the specified filter name */
guint nb_match; /* How many dissectors matched searched_name */
};
typedef struct protocol_name_search *protocol_name_search_t;
/*
* This function parses all dissectors associated with a table to find the
* one whose protocol has the specified filter name. It is called
* as a reference function in a call to dissector_table_foreach_handle.
* The name we are looking for, as well as the results, are stored in the
* protocol_name_search struct pointed to by user_data.
* If called using dissector_table_foreach_handle, we actually parse the
* whole list of dissectors.
*/
static void
find_protocol_name_func(const gchar *table _U_, gpointer handle, gpointer user_data)
{
int proto_id;
const gchar *protocol_filter_name;
protocol_name_search_t search_info;
ws_assert(handle);
search_info = (protocol_name_search_t)user_data;
proto_id = dissector_handle_get_protocol_index((dissector_handle_t)handle);
if (proto_id != -1) {
protocol_filter_name = proto_get_protocol_filter_name(proto_id);
ws_assert(protocol_filter_name != NULL);
if (strcmp(protocol_filter_name, search_info->searched_name) == 0) {
/* Found a match */
if (search_info->nb_match == 0) {
/* Record this handle only if this is the first match */
search_info->matched_handle = (dissector_handle_t)handle; /* Record the handle for this matching dissector */
}
search_info->nb_match++;
}
}
}
/*
* The function below parses the command-line parameters for the decode as
* feature (a string pointer by cl_param).
* It checks the format of the command-line, searches for a matching table
* and dissector. If a table/dissector match is not found, we display a
* summary of the available tables/dissectors (on stderr) and return FALSE.
* If everything is fine, we get the "Decode as" preference activated,
* then we return TRUE.
*/
gboolean decode_as_command_option(const gchar *cl_param)
{
gchar *table_name;
guint32 selector = 0, selector2 = 0;
gchar *decoded_param;
gchar *remaining_param;
gchar *selector_str = NULL;
gchar *dissector_str;
dissector_handle_t dissector_matching;
dissector_table_t table_matching;
ftenum_t dissector_table_selector_type;
struct protocol_name_search user_protocol_name;
guint64 i;
char op = '\0';
/* The following code will allocate and copy the command-line options in a string pointed by decoded_param */
ws_assert(cl_param);
decoded_param = g_strdup(cl_param);
ws_assert(decoded_param);
/* The lines below will parse this string (modifying it) to extract all
necessary information. Note that decoded_param is still needed since
strings are not copied - we just save pointers. */
/* This section extracts a layer type (table_name) from decoded_param */
table_name = decoded_param; /* Layer type string starts from beginning */
remaining_param = strchr(table_name, '=');
if (remaining_param == NULL) {
/* Dissector tables of type FT_NONE aren't required to specify a value, so for now
just check for comma */
remaining_param = strchr(table_name, ',');
if (remaining_param == NULL) {
cmdarg_err("Parameter \"%s\" doesn't follow the template \"%s\"", cl_param, DECODE_AS_ARG_TEMPLATE);
} else {
*remaining_param = '\0'; /* Terminate the layer type string (table_name) where ',' was detected */
}
/* If the argument does not follow the template, carry on anyway to check
if the table name is at least correct. If remaining_param is NULL,
we'll exit anyway further down */
}
else {
*remaining_param = '\0'; /* Terminate the layer type string (table_name) where '=' was detected */
}
/* Remove leading and trailing spaces from the table name */
while (table_name[0] == ' ')
table_name++;
while (table_name[strlen(table_name) - 1] == ' ')
table_name[strlen(table_name) - 1] = '\0'; /* Note: if empty string, while loop will eventually exit */
/* The following part searches a table matching with the layer type specified */
table_matching = NULL;
/* Look for the requested table */
if (!(*(table_name))) { /* Is the table name empty, if so, don't even search for anything, display a message */
cmdarg_err("No layer type specified"); /* Note, we don't exit here, but table_matching will remain NULL, so we exit below */
}
else {
table_matching = find_dissector_table(table_name);
if (!table_matching) {
cmdarg_err("Unknown layer type -- %s", table_name); /* Note, we don't exit here, but table_matching will remain NULL, so we exit below */
}
}
if (!table_matching) {
/* Display a list of supported layer types to help the user, if the
specified layer type was not found */
cmdarg_err("Valid layer types are:");
fprint_all_layer_types(stderr);
}
if (remaining_param == NULL || !table_matching) {
/* Exit if the layer type was not found, or if no '=' separator was found
(see above) */
g_free(decoded_param);
return FALSE;
}
dissector_table_selector_type = get_dissector_table_selector_type(table_name);
if (dissector_table_selector_type != FT_NONE) {
if (*(remaining_param + 1) != '=') { /* Check for "==" and not only '=' */
cmdarg_err("WARNING: -d requires \"==\" instead of \"=\". Option will be treated as \"%s==%s\"", table_name, remaining_param + 1);
}
else {
remaining_param++; /* Move to the second '=' */
*remaining_param = '\0'; /* Remove the second '=' */
}
remaining_param++; /* Position after the layer type string */
/* This section extracts a selector value (selector_str) from decoded_param */
selector_str = remaining_param; /* Next part starts with the selector number */
remaining_param = strchr(selector_str, ',');
if (remaining_param == NULL) {
cmdarg_err("Parameter \"%s\" doesn't follow the template \"%s\"", cl_param, DECODE_AS_ARG_TEMPLATE);
/* If the argument does not follow the template, carry on anyway to check
if the selector value is at least correct. If remaining_param is NULL,
we'll exit anyway further down */
}
else {
*remaining_param = '\0'; /* Terminate the selector number string (selector_str) where ',' was detected */
}
}
switch (dissector_table_selector_type) {
case FT_UINT8:
case FT_UINT16:
case FT_UINT24:
case FT_UINT32:
{
/* The selector for this table is an unsigned number. Parse it as such.
Skip leading spaces for backwards compatibility (previously sscanf was used). */
gchar *str = selector_str;
gchar *end;
guint64 val;
while (g_ascii_isspace(*str)) {
str++;
}
val = g_ascii_strtoull(str, &end, 0);
if (str == end || val > G_MAXUINT32) {
cmdarg_err("Invalid selector number \"%s\"", selector_str);
g_free(decoded_param);
return FALSE;
}
selector = (guint32) val;
if (*end == '\0') {
/* not a range, but a single (valid) value */
op = '\0';
selector2 = 0;
} else if (*end == ':' || *end == '-') {
/* range value such as "8888:3" or "8888-8890" */
op = *end;
str = end + 1;
val = g_ascii_strtoull(str, &end, 0);
if (str == end || val > G_MAXUINT32 || *end != '\0') {
cmdarg_err("Invalid selector numeric range \"%s\"", selector_str);
g_free(decoded_param);
return FALSE;
}
selector2 = (guint32) val;
if (op == ':') {
if ((selector2 == 0) || ((guint64)selector + selector2 - 1) > G_MAXUINT32) {
cmdarg_err("Invalid selector numeric range \"%s\"", selector_str);
g_free(decoded_param);
return FALSE;
}
}
else if (selector2 < selector) {
/* We could swap them for the user, but maybe it's better to call
* this out as an error in case it's not what was intended? */
cmdarg_err("Invalid selector numeric range \"%s\"", selector_str);
g_free(decoded_param);
return FALSE;
}
} else {
/* neither a valid single value, nor a range. */
cmdarg_err("Invalid selector number \"%s\"", selector_str);
g_free(decoded_param);
return FALSE;
}
break;
}
case FT_STRING:
case FT_STRINGZ:
case FT_UINT_STRING:
case FT_STRINGZPAD:
case FT_STRINGZTRUNC:
/* The selector for this table is a string. */
break;
case FT_NONE:
/* There is no selector for this table */
break;
default:
/* There are currently no dissector tables with any types other
than the ones listed above. */
ws_assert_not_reached();
}
if (remaining_param == NULL) {
/* Exit if no ',' separator was found (see above) */
cmdarg_err("Valid protocols for layer type \"%s\" are:", table_name);
fprint_all_protocols_for_layer_types(stderr, table_name);
g_free(decoded_param);
return FALSE;
}
remaining_param++; /* Position after the selector number string */
/* This section extracts a protocol filter name (dissector_str) from decoded_param */
dissector_str = remaining_param; /* All the rest of the string is the dissector (decode as protocol) name */
/* Remove leading and trailing spaces from the dissector name */
while (dissector_str[0] == ' ')
dissector_str++;
while (dissector_str[strlen(dissector_str) - 1] == ' ')
dissector_str[strlen(dissector_str) - 1] = '\0'; /* Note: if empty string, while loop will eventually exit */
dissector_matching = NULL;
/* We now have a pointer to the handle for the requested table inside the variable table_matching */
if (!(*dissector_str)) { /* Is the dissector name empty, if so, don't even search for a matching dissector and display all dissectors found for the selected table */
cmdarg_err("No protocol name specified"); /* Note, we don't exit here, but dissector_matching will remain NULL, so we exit below */
}
else {
header_field_info *hfi = proto_registrar_get_byalias(dissector_str);
user_protocol_name.nb_match = 0;
if (hfi) {
user_protocol_name.searched_name = hfi->abbrev;
} else {
user_protocol_name.searched_name = dissector_str;
}
user_protocol_name.matched_handle = NULL;
dissector_table_foreach_handle(table_name, find_protocol_name_func, &user_protocol_name); /* Go and perform the search for this dissector in the this table's dissectors' names and shortnames */
if (user_protocol_name.nb_match != 0) {
dissector_matching = user_protocol_name.matched_handle;
if (user_protocol_name.nb_match > 1) {
cmdarg_err("WARNING: Protocol \"%s\" matched %u dissectors, first one will be used", dissector_str, user_protocol_name.nb_match);
}
}
else {
/* OK, check whether the problem is that there isn't any such
protocol, or that there is but it's not specified as a protocol
that's valid for that dissector table.
Note, we don't exit here, but dissector_matching will remain NULL,
so we exit below */
if (proto_get_id_by_filter_name(dissector_str) == -1) {
/* No such protocol */
cmdarg_err("Unknown protocol -- \"%s\"", dissector_str);
}
else {
cmdarg_err("Protocol \"%s\" isn't valid for layer type \"%s\"",
dissector_str, table_name);
}
}
}
if (!dissector_matching) {
cmdarg_err("Valid protocols for layer type \"%s\" are:", table_name);
fprint_all_protocols_for_layer_types(stderr, table_name);
g_free(decoded_param);
return FALSE;
}
/* This is the end of the code that parses the command-line options.
All information is now stored in the variables:
table_name
selector
dissector_matching
The above variables that are strings are still pointing to areas within
decoded_parm. decoded_parm thus still needs to be kept allocated in
until we stop needing these variables
decoded_param will be deallocated at each exit point of this function */
/* We now have a pointer to the handle for the requested dissector
(requested protocol) inside the variable dissector_matching */
switch (dissector_table_selector_type) {
case FT_UINT8:
case FT_UINT16:
case FT_UINT24:
case FT_UINT32:
/* The selector for this table is an unsigned number. */
if (op == '\0') {
dissector_change_uint(table_name, selector, dissector_matching);
}
else if (op == ':') {
for (i = selector; i < (guint64)selector + selector2; i++) {
dissector_change_uint(table_name, (guint32)i, dissector_matching);
}
}
else { /* op == '-' */
for (i = selector; i <= selector2; i++) {
dissector_change_uint(table_name, (guint32)i, dissector_matching);
}
}
break;
case FT_STRING:
case FT_STRINGZ:
case FT_UINT_STRING:
case FT_STRINGZPAD:
case FT_STRINGZTRUNC:
/* The selector for this table is a string. */
dissector_change_string(table_name, selector_str, dissector_matching);
break;
case FT_NONE:
/* Just directly set the dissector found. */
dissector_change_payload(table_name, dissector_matching);
break;
default:
/* There are currently no dissector tables with any types other
than the ones listed above. */
ws_assert_not_reached();
}
g_free(decoded_param); /* "Decode As" rule has been successfully added */
return TRUE;
}
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