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/**********************************************************************
*
* This file is part of Cardpeek, the smart card reader utility.
*
* Copyright 2009-2013 by Alain Pannetrat <L1L1@gmx.com>
*
* Cardpeek 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 3 of the License, or
* (at your option) any later version.
*
* Cardpeek 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 Cardpeek. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include "misc.h"
#include "asn1.h" /* includes <bytestring> */
#define ASN1_VERIFY(bs) if (bs->width!=8) { log_printf(LOG_ERROR,"ASN1 operation requires 8 bit-width bytestring"); return BYTESTRING_ERROR; }
int FORCE_SINGLE_BYTE_LENGTH = 0;
int asn1_force_single_byte_length_parsing(int enable)
{
int retval = FORCE_SINGLE_BYTE_LENGTH;
FORCE_SINGLE_BYTE_LENGTH = enable;
log_printf(LOG_INFO,
"Setting ASN1 single byte length parsing to %s",
enable?"true":"false");
return retval;
}
int asn1_skip_tlv(unsigned *pos, const bytestring_t *tlvlist)
{
unsigned tag;
if (asn1_decode_tag(pos,tlvlist,&tag)!=BYTESTRING_OK)
return BYTESTRING_ERROR;
return asn1_skip_value(pos,tlvlist);
}
int asn1_decode_tag(unsigned *pos, const bytestring_t *tlv, unsigned *tag)
{
unsigned char element;
unsigned room = bytestring_get_size(tlv);
*tag = 0;
ASN1_VERIFY(tlv);
if (room<*pos+1)
{
log_printf(LOG_WARNING,"Error decoding tag in tlv");
return BYTESTRING_ERROR;
}
room -=*pos;
bytestring_get_element(&element,tlv,(*pos)++);
*tag=element;
room--;
if ((*tag&0x1F)!=0x1F)
return BYTESTRING_OK;
do {
*tag<<=8;
bytestring_get_element(&element,tlv,(*pos)++);
*tag|=element;
room--;
} while (((*tag&0xFF)>0x80) && room>0);
if (room==0 && (*tag&0xFF)>0x80)
{
log_printf(LOG_WARNING,"Tag length error in tlv");
return BYTESTRING_ERROR;
}
return BYTESTRING_OK;
}
int asn1_decode_length(unsigned *pos, const bytestring_t *lv, unsigned* len)
{
unsigned char element;
unsigned room = bytestring_get_size(lv);
unsigned i;
*len=0;
ASN1_VERIFY(lv);
if (room<*pos+1)
{
log_printf(LOG_WARNING,"Missing tlv length");
return BYTESTRING_ERROR;
}
room -=*pos;
bytestring_get_element(&element,lv,(*pos)++);
if ((element&0x80)==0x80 && !FORCE_SINGLE_BYTE_LENGTH)
{
unsigned len_of_len=element&0x7F;
if (room<=len_of_len || len_of_len>4)
{
log_printf(LOG_WARNING,"Length of length error in tlv");
return BYTESTRING_ERROR;
}
for (i=0;i<len_of_len;i++)
{
bytestring_get_element(&element,lv,(*pos)++);
*len=(*len<<8)+element;
}
}
else
{
*len=element;
}
return BYTESTRING_OK;
}
int asn1_skip_value(unsigned *pos, const bytestring_t *lv)
{
unsigned len;
if (asn1_decode_length(pos,lv,&len)!=BYTESTRING_OK)
return BYTESTRING_ERROR;
if (*pos+len>bytestring_get_size(lv))
return BYTESTRING_ERROR;
*pos+=len;
return BYTESTRING_OK;
}
int asn1_decode_value(unsigned *pos, const bytestring_t *lv, bytestring_t *val)
{
unsigned len;
bytestring_clear(val);
if (asn1_decode_length(pos,lv,&len)!=BYTESTRING_OK)
return BYTESTRING_ERROR;
if (*pos+len>bytestring_get_size(lv))
{
log_printf(LOG_ERROR,"Value length error in tlv at position %i: expected %i, have only %i",*pos,*pos+len,bytestring_get_size(lv));
*pos+=bytestring_get_size(lv);
return BYTESTRING_ERROR;
}
/***
{
log_printf(LOG_WARNING,"Value length error in tlv at position %i: expected %i, have only %i",*pos,*pos+len,bytestring_get_size(lv));
len = bytestring_get_size(lv)-*pos;
log_printf(LOG_WARNING,"Attempting to shrink tlv length to %i, with unpredictable results",len);
}
***/
bytestring_substr(val,*pos,len,lv);
*pos+=len;
return BYTESTRING_OK;
}
int asn1_decode_tlv(unsigned *pos, const bytestring_t *tlv, unsigned *tag, bytestring_t *val)
{
if (asn1_decode_tag(pos,tlv,tag)!=BYTESTRING_OK)
return BYTESTRING_ERROR;
if (asn1_decode_value(pos,tlv,val)!=BYTESTRING_OK)
{
log_printf(LOG_WARNING,"... after parsing tag `%X'",*tag);
return BYTESTRING_ERROR;
}
return BYTESTRING_OK;
}
int asn1_encode_tag(unsigned tag, bytestring_t* bertag)
{
ASN1_VERIFY(bertag);
bytestring_clear(bertag);
if (tag>0xFFFFFF)
bytestring_pushback(bertag,tag>>24);
if (tag>0xFFFF)
bytestring_pushback(bertag,(tag>>16)&0xFF);
if (tag>0xFF)
bytestring_pushback(bertag,(tag>>8)&0xFF);
bytestring_pushback(bertag,tag&0xFF);
return BYTESTRING_OK;
}
int asn1_encode_tlv(unsigned tag, const bytestring_t *val, bytestring_t *bertlv)
{
unsigned len = bytestring_get_size(val);
if (asn1_encode_tag(tag,bertlv)!=BYTESTRING_OK)
return BYTESTRING_ERROR;
if (len>0xFFFFFF)
{
bytestring_pushback(bertlv,0x84);
bytestring_pushback(bertlv,(len>>24)&0xFF);
bytestring_pushback(bertlv,(len>>16)&0xFF);
bytestring_pushback(bertlv,(len>>8)&0xFF);
bytestring_pushback(bertlv,(len)&0xFF);
}
else if (len>0xFFFF)
{
bytestring_pushback(bertlv,0x83);
bytestring_pushback(bertlv,(len>>16)&0xFF);
bytestring_pushback(bertlv,(len>>8)&0xFF);
bytestring_pushback(bertlv,(len)&0xFF);
}
else if (len>0xFF)
{
bytestring_pushback(bertlv,0x82);
bytestring_pushback(bertlv,(len>>8)&0xFF);
bytestring_pushback(bertlv,(len)&0xFF);
}
else if (len>0x80)
{
bytestring_pushback(bertlv,0x81);
bytestring_pushback(bertlv,(len)&0xFF);
}
else
bytestring_pushback(bertlv,len&0xFF);
bytestring_append(bertlv,val);
return BYTESTRING_OK;
}
/************************************************************/
const unsigned ANY_TAG = 0xFFFFFFFF;
static int seek_index(unsigned *pos, unsigned max, const bytestring_t *data, unsigned t_index, unsigned tag)
{
unsigned cindex = 0;
unsigned ctag=0;
while (cindex<=t_index && *pos<max)
{
if (asn1_decode_tag(pos,data,&ctag)!=BYTESTRING_OK)
return BYTESTRING_ERROR;
if (tag==ANY_TAG || tag==ctag)
{
if (t_index==cindex)
return BYTESTRING_OK;
else
cindex++;
}
if (!asn1_skip_value(pos,data))
return BYTESTRING_ERROR;
}
return BYTESTRING_ERROR;
}
static const char *parse_tag(unsigned *tag, const char *s)
{
char s_pos[15];
int s_pos_i;
*tag=ANY_TAG;
if (!isxdigit(*s))
return NULL;
s_pos_i=0;
while (isxdigit(*s) && s_pos_i<14)
{
s_pos[s_pos_i++]=*s++;
}
s_pos[s_pos_i]=0;
if (!isxdigit(*s))
{
*tag=strtol(s_pos,NULL,16);
return s;
}
return NULL;
}
static const char *parse_index(unsigned *t_index, const char *s)
{
char s_index[15];
int s_index_i;
*t_index=0;
if (*s!='[')
return NULL;
s++;
s_index_i=0;
while (isdigit(*s) && s_index_i<15)
{
s_index[s_index_i++]=*s++;
}
s_index[s_index_i]=0;
if (*s==']')
{
*t_index=atoi(s_index);
return s+1;
}
return NULL;
}
static int parse_path_internal(const char* path, unsigned *pos, unsigned max, const bytestring_t *src, bytestring_t *val)
{
unsigned tag=ANY_TAG;
unsigned t_index=0;
unsigned length;
while (*path=='/') path++;
if (*path==0)
goto parse_path_fail;
if (*path=='[')
path=parse_index(&t_index,path);
else
{
path=parse_tag(&tag,path);
if (path!=NULL && *path=='[')
path=parse_index(&t_index,path);
}
if (path==NULL) /* parse error */
goto parse_path_fail;
if (seek_index(pos,max,src,t_index,tag)==BYTESTRING_OK)
{
if (*path)
{
asn1_decode_length(pos,src,&length);
return parse_path_internal(path,pos,*pos+length,src,val);
}
return asn1_decode_value(pos,src,val);
}
parse_path_fail:
bytestring_clear(val);
return BYTESTRING_ERROR;
}
int asn1_parse_path(const char* path, const bytestring_t *src, bytestring_t *val)
{
unsigned pos=0;
return parse_path_internal(path,&pos,bytestring_get_size(src),src,val);
}
/***************************************************************/
#ifdef TEST_ASN1
#include <stdio.h>
int main(int argc, char **argv)
{
const char *s = "6F 25 84 07 A0 00 00 00 03 10 10 A5 1A 50 0A 56 49 53 41 43 52 45 44 49 54 87 01 01 5F 2D 08 65 6E 7A 68 6A 61 6B 6F";
bytestring_t* t = bytestring_new_from_hex(s);
unsigned tag,len;
bytestring_t* value = bytestring_new();
unsigned pos=0;
char *tmp;
asn1_force_single_byte_length_parsing(1);
tmp = bytestring_to_hex_string(t);
fprintf(stderr,"%s\n",tmp);
free(tmp);
fprintf(stderr,"retcode=%i\n",asn1_decode_tag(&pos,t,&tag));
fprintf(stderr,"pos=%i\n",pos);
fprintf(stderr,"tag=%x\n",tag);
fprintf(stderr,"retcode=%i\n",asn1_decode_value(&pos,t,value));
fprintf(stderr,"pos=%i\n",pos);
tmp = bytestring_to_hex_string(value);
fprintf(stderr,"val=%s\n",tmp);
free(tmp);
bytestring_free(t);
bytestring_free(value);
}
#endif
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