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/* packet-ber.c
* Helpers for ASN.1/BER dissection
* Ronnie Sahlberg (C) 2004
*
* $Id: packet-ber.c,v 1.3 2004/03/01 09:11:23 sahlberg Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@ethereal.com>
* Copyright 1998 Gerald Combs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <glib.h>
#include <epan/packet.h>
#include <epan/strutil.h>
#include "prefs.h"
#include "packet-ber.h"
static gint proto_ber = -1;
static gint hf_ber_id_class = -1;
static gint hf_ber_id_pc = -1;
static gint hf_ber_id_uni_tag = -1;
static gint hf_ber_id_tag = -1;
static gint hf_ber_length = -1;
static gint hf_ber_bitstring_padding = -1;
static gint ett_ber_octet_string = -1;
static gboolean show_internal_ber_fields = FALSE;
proto_item *ber_last_created_item=NULL;
static const value_string ber_class_codes[] = {
{ BER_CLASS_UNI, "Universal" },
{ BER_CLASS_APP, "Application" },
{ BER_CLASS_CON, "Context Specific" },
{ BER_CLASS_PRI, "Private" },
{ 0, NULL }
};
static const true_false_string ber_pc_codes = {
"Constructed Encoding",
"Primitive Encoding"
};
static const value_string ber_uni_tag_codes[] = {
{ BER_UNI_TAG_BOOLEAN, "Boolean" },
{ BER_UNI_TAG_INTEGER, "Integer" },
{ BER_UNI_TAG_BITSTRING, "Bit-String" },
{ BER_UNI_TAG_OCTETSTRING, "Octet String" },
{ BER_UNI_TAG_SEQUENCE, "Sequence" },
{ BER_UNI_TAG_GENTIME, "Generalized Time" },
{ BER_UNI_TAG_GENSTR, "General String" },
{ 0, NULL }
};
/* this function dissects the identifier octer of the BER TLV.
* We only handle TAGs (and LENGTHs) that fit inside 32 bit integers.
*/
int
dissect_ber_identifier(packet_info *pinfo _U_, proto_tree *tree, tvbuff_t *tvb, int offset, guint8 *class, gboolean *pc, guint32 *tag)
{
guint8 id;
int old_offset=offset;
id=tvb_get_guint8(tvb, offset);
offset+=1;
*class=(id>>6)&0x03;
*pc=(id>>5)&0x01;
*tag=id&0x1f;
/*XXX handle case when TAG==0x1f */
if(show_internal_ber_fields){
proto_tree_add_uint(tree, hf_ber_id_class, tvb, old_offset, 1, id);
proto_tree_add_boolean(tree, hf_ber_id_pc, tvb, old_offset, 1, id);
if(*class==BER_CLASS_UNI){
proto_tree_add_uint(tree, hf_ber_id_uni_tag, tvb, old_offset, 1, *tag);
} else {
proto_tree_add_uint(tree, hf_ber_id_tag, tvb, old_offset, 1, *tag);
}
}
return offset;
}
/* this function dissects the identifier octer of the BER TLV.
* We only handle (TAGs and) LENGTHs that fit inside 32 bit integers.
*/
int
dissect_ber_length(packet_info *pinfo _U_, proto_tree *tree, tvbuff_t *tvb, int offset, guint32 *length)
{
guint8 id;
int old_offset=offset;
*length=0;
id=tvb_get_guint8(tvb, offset);
offset+=1;
if(!(id&0x80)){
*length=id;
if(show_internal_ber_fields){
proto_tree_add_uint(tree, hf_ber_length, tvb, old_offset, 1, *length);
}
return offset;
}
/* length byte has bit 8 set ! */
id&=0x7f;
while(id--){
guint tmpl;
tmpl=tvb_get_guint8(tvb, offset);
offset++;
*length=((*length)<<8)+tmpl;
}
if(show_internal_ber_fields){
/*XXX show the len byte */
proto_tree_add_uint(tree, hf_ber_length, tvb, old_offset+1, offset-old_offset+1, *length);
}
return offset;
}
/* func is NULL normally but
* if the octet string contains an ber encode struct we provide func as the
* dissector for that struct
*/
int
dissect_ber_octet_string(packet_info *pinfo, proto_tree *tree, tvbuff_t *tvb, int offset, gint hf_id, ber_callback func)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
int end_offset;
proto_item *it;
/* read header and len for the octet string */
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
end_offset=offset+len;
if(!len){
return end_offset;
}
/* sanity check: we only handle Constructed Universal Sequences */
if( (class!=BER_CLASS_UNI)
||(tag!=BER_UNI_TAG_OCTETSTRING) ){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: OctetString expected but Class:%d PC:%d Tag:%d was unexpected", class, pc, tag);
return end_offset;
}
if(hf_id!=-1){
it=proto_tree_add_item(tree, hf_id, tvb, offset, len, FALSE);
tree=proto_item_add_subtree(it, ett_ber_octet_string);
}
if(func){
tvbuff_t *next_tvb;
next_tvb=tvb_new_subset(tvb, offset, len, len);
func(pinfo, tree, next_tvb, 0);
}
/*qqq*/
return end_offset;
}
int
dissect_ber_integer(packet_info *pinfo, proto_tree *tree, tvbuff_t *tvb, int offset, gint hf_id, guint32 *value)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
guint32 val;
guint32 i;
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
/* if(class!=BER_CLASS_UNI)*/
val=0;
for(i=0;i<len;i++){
val=(val<<8)|tvb_get_guint8(tvb, offset);
offset++;
}
ber_last_created_item=NULL;
if(hf_id!=-1){
ber_last_created_item=proto_tree_add_uint(tree, hf_id, tvb, offset-len, len, val);
}
if(value){
*value=val;
}
return offset;
}
int
dissect_ber_boolean(packet_info *pinfo, proto_tree *tree, tvbuff_t *tvb, int offset, gint hf_id)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
guint8 val;
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
/* if(class!=BER_CLASS_UNI)*/
val=tvb_get_guint8(tvb, offset);
offset+=1;
ber_last_created_item=NULL;
if(hf_id!=-1){
ber_last_created_item=proto_tree_add_uint(tree, hf_id, tvb, offset-1, 1, val?1:0);
}
return offset;
}
/* this function dissects a BER sequence
*/
int
dissect_ber_sequence(packet_info *pinfo, proto_tree *parent_tree, tvbuff_t *tvb, int offset, ber_sequence *seq, gint hf_id, gint ett_id)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
proto_tree *tree=parent_tree;
proto_item *item=NULL;
int end_offset;
/* first we must read the sequence header */
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
end_offset=offset+len;
/* sanity check: we only handle Constructed Universal Sequences */
if( (class!=BER_CLASS_UNI)
||(!pc)
||(tag!=BER_UNI_TAG_SEQUENCE) ){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: Sequence expected but Class:%d PC:%d Tag:%d was unexpected", class, pc, tag);
return end_offset;
}
/* create subtree */
if(hf_id!=-1){
if(parent_tree){
item = proto_tree_add_item(parent_tree, hf_id, tvb, offset, len, FALSE);
tree = proto_item_add_subtree(item, ett_id);
}
}
/* loop over all entries until we reach the end of the sequence */
while(offset<end_offset){
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
int eoffset;
/* read header and len for next field */
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
eoffset=offset+len;
ber_sequence_try_again:
/* have we run out of known entries in the sequence ?*/
if(!seq->func){
/* it was not, move to the enxt one and try again */
proto_tree_add_text(tree, tvb, offset, len, "BER Error: This field lies beyond the end of the known sequence definition.");
offset=eoffset;
continue;
}
/* verify that this one is the one we want */
if( (seq->class!=class)
||(seq->tag!=tag) ){
/* it was not, move to the enxt one and try again */
if(seq->flags&BER_FLAGS_OPTIONAL){
/* well this one was optional so just skip to the next one and try again. */
seq++;
goto ber_sequence_try_again;
}
proto_tree_add_text(tree, tvb, offset, len, "BER Error: Wrong field");
seq++;
offset=eoffset;
continue;
}
/* call the dissector for this field */
seq->func(pinfo, tree, tvb, offset);
seq++;
offset=eoffset;
}
/* if we didnt end up at exactly offset, then we ate too many bytes */
if(offset!=end_offset){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: Sequence ate %d too many bytes", offset-end_offset);
}
return end_offset;
}
/* this function dissects a BER choice
*/
int
dissect_ber_choice(packet_info *pinfo, proto_tree *parent_tree, tvbuff_t *tvb, int offset, const ber_choice *ch, gint hf_id, gint ett_id)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
proto_tree *tree=parent_tree;
proto_item *item=NULL;
int end_offset;
/* first we must read the sequence header */
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
end_offset=offset+len;
/* create subtree */
if(hf_id!=-1){
if(parent_tree){
item = proto_tree_add_item(parent_tree, hf_id, tvb, offset, len, FALSE);
tree = proto_item_add_subtree(item, ett_id);
}
}
/* loop over all entries until we find the right choice or
run out of entries */
while(ch->func){
if( (ch->class==class)
&&(ch->tag==tag) ){
offset=ch->func(pinfo, tree, tvb, offset);
return end_offset;
break;
}
ch++;
}
/* oops no more entries and we still havent found
* our guy :-(
*/
proto_tree_add_text(tree, tvb, offset, len, "BER Error: This choice field was not found.");
return end_offset;
}
/* this function dissects a BER GeneralString
*/
int
dissect_ber_GeneralString(packet_info *pinfo, proto_tree *tree, tvbuff_t *tvb, int offset, gint hf_id, char *name_string, int name_len)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
int end_offset;
char str_arr[256];
guint32 max_len;
char *str;
str=str_arr;
max_len=255;
if(name_string){
str=name_string;
max_len=name_len;
}
/* first we must read the GeneralString header */
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
end_offset=offset+len;
/* sanity check: we only handle Universal GeneralString*/
if( (class!=BER_CLASS_UNI)
||(tag!=BER_UNI_TAG_GENSTR) ){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: GeneralString expected but Class:%d PC:%d Tag:%d was unexpected", class, pc, tag);
return end_offset;
}
if(len>=(max_len-1)){
len=max_len-1;
}
tvb_memcpy(tvb, str, offset, len);
str[len]=0;
if(hf_id!=-1){
proto_tree_add_string(tree, hf_id, tvb, offset, len, str);
}
return end_offset;
}
/* this function dissects a BER sequence of
*/
int
dissect_ber_sequence_of(packet_info *pinfo, proto_tree *parent_tree, tvbuff_t *tvb, int offset, ber_callback func, gint hf_id, gint ett_id)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
proto_tree *tree=parent_tree;
proto_item *item=NULL;
int end_offset;
/* first we must read the sequence header */
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
end_offset=offset+len;
/* sanity check: we only handle Constructed Universal Sequences */
if( (class!=BER_CLASS_UNI)
||(!pc)
||(tag!=BER_UNI_TAG_SEQUENCE) ){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: SequenceOf expected but Class:%d PC:%d Tag:%d was unexpected", class, pc, tag);
return end_offset;
}
/* create subtree */
if(hf_id!=-1){
if(parent_tree){
item = proto_tree_add_item(parent_tree, hf_id, tvb, offset, len, FALSE);
tree = proto_item_add_subtree(item, ett_id);
}
}
/* loop over all entries until we reach the end of the sequence */
while(offset<end_offset){
/* call the dissector for this field */
offset=func(pinfo, tree, tvb, offset);
}
/* if we didnt end up at exactly offset, then we ate too many bytes */
if(offset!=end_offset){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: SequenceOf ate %d too many bytes", offset-end_offset);
}
return end_offset;
}
int
dissect_ber_generalized_time(packet_info *pinfo, proto_tree *tree, tvbuff_t *tvb, int offset, gint hf_id)
{
char str[32];
const guint8 *tmpstr;
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
int end_offset;
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
end_offset=offset+len;
/* sanity check. we only handle universal/generalized time */
if( (class!=BER_CLASS_UNI)
||(tag!=BER_UNI_TAG_GENTIME)){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: GeneralizedTime expected but Class:%d PC:%d Tag:%d was unexpected", class, pc, tag);
return end_offset;
end_offset=offset+len;
}
tmpstr=tvb_get_ptr(tvb, offset, len);
snprintf(str, 31, "%.4s-%.2s-%.2s %.2s:%.2s:%.2s (%.1s)",
tmpstr, tmpstr+4, tmpstr+6, tmpstr+8,
tmpstr+10, tmpstr+12, tmpstr+14);
str[31]=0; /* just in case ... */
if(hf_id!=-1){
proto_tree_add_string(tree, hf_id, tvb, offset, len, str);
}
offset+=len;
return offset;
}
/* this function dissects a BER BIT-STRING
*/
int
dissect_ber_bitstring(packet_info *pinfo, proto_tree *parent_tree, tvbuff_t *tvb, int offset, gint hf_id, gint ett_id, unsigned char *bitstring, int bitstring_len, proto_item **it, proto_tree **tr)
{
guint8 class;
gboolean pc;
guint32 tag;
guint32 len;
proto_tree *tree=parent_tree;
proto_item *item=NULL;
int end_offset;
guint8 pad;
gboolean first_time=TRUE;
/* first we must read the sequence header */
offset=dissect_ber_identifier(pinfo, tree, tvb, offset, &class, &pc, &tag);
offset=dissect_ber_length(pinfo, tree, tvb, offset, &len);
end_offset=offset+len;
/* sanity check: we only handle Universal BitSrings */
if( (class!=BER_CLASS_UNI)
||(tag!=BER_UNI_TAG_BITSTRING) ){
proto_tree_add_text(tree, tvb, offset-2, 2, "BER Error: BitString expected but Class:%d PC:%d Tag:%d was unexpected", class, pc, tag);
return end_offset;
}
/* create subtree */
if(hf_id!=-1){
if(parent_tree){
item = proto_tree_add_item(parent_tree, hf_id, tvb, offset, len, FALSE);
tree = proto_item_add_subtree(item, ett_id);
}
}
if(tr){
*tr=tree;
}
if(it){
*it=item;
}
/* padding */
pad=tvb_get_guint8(tvb, offset);
proto_tree_add_item(tree, hf_ber_bitstring_padding, tvb, offset, 1, FALSE);
offset+=1;
len--;
/* XXX we should handle segmented bitstrings */
while(len--){
guint8 tmp;
tmp=tvb_get_guint8(tvb, offset);
offset++;
if(item){
if(first_time){
proto_item_append_text(item, " 0x");
}
proto_item_append_text(item, "%02x",tmp);
first_time=FALSE;
}
if(bitstring){
*(bitstring++)=tmp;
if(--bitstring_len<=0){
bitstring=NULL;
}
}
}
return end_offset;
}
void
proto_register_ber(void)
{
static hf_register_info hf[] = {
{ &hf_ber_id_class, {
"Class", "ber.id.class", FT_UINT8, BASE_DEC,
VALS(ber_class_codes), 0xc0, "Class of BER TLV Identifier", HFILL }},
{ &hf_ber_bitstring_padding, {
"Padding", "ber.bitstring.padding", FT_UINT8, BASE_DEC,
NULL, 0x0, "Number of unsused bits in the last octet of the bitstring", HFILL }},
{ &hf_ber_id_pc, {
"P/C", "ber.id.pc", FT_BOOLEAN, 8,
TFS(&ber_pc_codes), 0x20, "Primitive or Constructed BER encoding", HFILL }},
{ &hf_ber_id_uni_tag, {
"Tag", "ber.id.uni_tag", FT_UINT8, BASE_DEC,
VALS(ber_uni_tag_codes), 0x1f, "Universal tag type", HFILL }},
{ &hf_ber_id_tag, {
"Tag", "ber.id.tag", FT_UINT32, BASE_DEC,
NULL, 0, "Tag value for non-Universal classes", HFILL }},
{ &hf_ber_length, {
"Length", "ber.length", FT_UINT32, BASE_DEC,
NULL, 0, "Length of contents", HFILL }},
};
static gint *ett[] = {
&ett_ber_octet_string,
};
module_t *ber_module;
proto_ber = proto_register_protocol("ASN.1 BER", "BER", "ber");
proto_register_field_array(proto_ber, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
/* Register preferences */
ber_module = prefs_register_protocol(proto_ber, NULL);
prefs_register_bool_preference(ber_module, "show_internals",
"Show internal BER encapsulation tokens",
"Whether the dissector should also display internal"
" ASN.1 BER details such as Identifier and Length fields", &show_internal_ber_fields);
}
void
proto_reg_handoff_ber(void)
{
}
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