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/* ber-help.c - BER herlper functions
* Copyright (C) 2001 g10 Code GmbH
*
* This file is part of KSBA.
*
* KSBA 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.
*
* KSBA 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
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "util.h"
#include "asn1-func.h" /* need some constants */
#include "ber-help.h"
static int
read_byte (KsbaReader reader)
{
unsigned char buf;
size_t nread;
int rc;
do
rc = ksba_reader_read (reader, &buf, 1, &nread);
while (!rc && !nread);
return rc? -1: buf;
}
static int
eof_or_error (KsbaReader reader, struct tag_info *ti, int premature)
{
if (ksba_reader_error (reader))
{
ti->err_string = "read error";
return KSBA_Read_Error;
}
if (premature)
{
ti->err_string = "premature EOF";
return KSBA_BER_Error;
}
return -1;
}
/*
Read the tag and the length part from the TLV triplet.
*/
KsbaError
_ksba_ber_read_tl (KsbaReader reader, struct tag_info *ti)
{
int c;
unsigned long tag;
ti->length = 0;
ti->ndef = 0;
ti->nhdr = 0;
ti->err_string = NULL;
ti->non_der = 0;
/* Get the tag */
c = read_byte (reader);
if (c==-1)
return eof_or_error (reader, ti, 0);
ti->buf[ti->nhdr++] = c;
ti->class = (c & 0xc0) >> 6;
ti->is_constructed = !!(c & 0x20);
tag = c & 0x1f;
if (tag == 0x1f)
{
tag = 0;
do
{
/* fixme: check for overflow of out datatype */
tag <<= 7;
c = read_byte (reader);
if (c == -1)
return eof_or_error (reader, ti, 1);
if (ti->nhdr >= DIM (ti->buf))
{
ti->err_string = "tag+length header too large";
return KSBA_BER_Error;
}
ti->buf[ti->nhdr++] = c;
tag |= c & 0x7f;
}
while (c & 0x80);
}
ti->tag = tag;
/* Get the length */
c = read_byte (reader);
if (c == -1)
return eof_or_error (reader, ti, 1);
if (ti->nhdr >= DIM (ti->buf))
{
ti->err_string = "tag+length header too large";
return KSBA_BER_Error;
}
ti->buf[ti->nhdr++] = c;
if ( !(c & 0x80) )
ti->length = c;
else if (c == 0x80)
{
ti->ndef = 1;
ti->non_der = 1;
}
else if (c == 0xff)
{
ti->err_string = "forbidden length value";
return KSBA_BER_Error;
}
else
{
unsigned long len = 0;
int count = c & 0x7f;
/* fixme: check for overflow of our length type */
for (; count; count--)
{
len <<= 8;
c = read_byte (reader);
if (c == -1)
return eof_or_error (reader, ti, 1);
if (ti->nhdr >= DIM (ti->buf))
{
ti->err_string = "tag+length header too large";
return KSBA_BER_Error;
}
ti->buf[ti->nhdr++] = c;
len |= c & 0xff;
}
ti->length = len;
}
/* Without this kludge some example certs can't be parsed */
if (ti->class == CLASS_UNIVERSAL && !ti->tag)
ti->length = 0;
return 0;
}
/* Write TAG of CLASS to WRITER. constructed is a flag telling
whether the value is a constructed one. length gives the length of
the value, if it is 0 undefinite length is assumed. length is
ignored for the NULL tag. */
KsbaError
_ksba_ber_write_tl (KsbaWriter writer,
unsigned long tag,
enum tag_class class,
int constructed,
unsigned long length)
{
unsigned char buf[50];
int buflen = 0;
if (tag < 0x1f)
{
*buf = (class << 6) | tag;
if (constructed)
*buf |= 0x20;
buflen++;
}
else
{
return KSBA_Not_Implemented;
}
if (!tag && !class)
buf[buflen++] = 0; /* NULL tag */
else if (!length)
buf[buflen++] = 0x80; /* indefinite length */
else if (length < 128)
buf[buflen++] = length;
else
{
int i;
/* fixme: if we know the sizeof an ulong we could support larger
objetcs - however this is pretty ridiculous */
i = (length <= 0xff ? 1:
length <= 0xffff ? 2:
length <= 0xffffff ? 3: 4);
buf[buflen++] = (0x80 | i);
if (i > 3)
buf[buflen++] = length >> 24;
if (i > 2)
buf[buflen++] = length >> 16;
if (i > 1)
buf[buflen++] = length >> 8;
buf[buflen++] = length;
}
return ksba_writer_write (writer, buf, buflen);
}

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Thu, Jul 17, 12:55 AM (1 d, 6 h)
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