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/* ber-help.c - BER herlper functions
* Copyright (C) 2001, 2012 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 either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - 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.
*
* or both in parallel, as here.
*
* 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 copies of the GNU General Public License
* and the GNU Lesser General Public License along with this program;
* if not, see <http://www.gnu.org/licenses/>.
*/
#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"
/* Fixme: The parser functions should check that primitive types don't
have the constructed bit set (which is not allowed). This saves us
some work when using these parsers */
static int
read_byte (ksba_reader_t 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
premature_eof (struct tag_info *ti)
{
/* Note: We do an strcmp on this string at othyer places. */
ti->err_string = "premature EOF";
return gpg_error (GPG_ERR_BAD_BER);
}
static gpg_error_t
eof_or_error (ksba_reader_t reader, struct tag_info *ti, int premature)
{
gpg_error_t err;
err = ksba_reader_error (reader);
if (err)
{
ti->err_string = "read error";
return err;
}
if (premature)
return premature_eof (ti);
return gpg_error (GPG_ERR_EOF);
}
/*
Read the tag and the length part from the TLV triplet.
*/
gpg_error_t
_ksba_ber_read_tl (ksba_reader_t 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
{
/* We silently ignore an overflow in the tag value. It is
not worth checking for it. */
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 gpg_error (GPG_ERR_BAD_BER);
}
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 gpg_error (GPG_ERR_BAD_BER);
}
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 gpg_error (GPG_ERR_BAD_BER);
}
else
{
unsigned long len = 0;
int count = c & 0x7f;
if (count > sizeof (len) || count > sizeof (size_t))
return gpg_error (GPG_ERR_BAD_BER);
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 gpg_error (GPG_ERR_BAD_BER);
}
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;
}
/*
Parse the buffer at the address BUFFER which of SIZE and return
the tag and the length part from the TLV triplet. Update BUFFER
and SIZE on success. */
gpg_error_t
_ksba_ber_parse_tl (unsigned char const **buffer, size_t *size,
struct tag_info *ti)
{
int c;
unsigned long tag;
const unsigned char *buf = *buffer;
size_t length = *size;
ti->length = 0;
ti->ndef = 0;
ti->nhdr = 0;
ti->err_string = NULL;
ti->non_der = 0;
/* Get the tag */
if (!length)
return premature_eof (ti);
c = *buf++; length--;
ti->buf[ti->nhdr++] = c;
ti->class = (c & 0xc0) >> 6;
ti->is_constructed = !!(c & 0x20);
tag = c & 0x1f;
if (tag == 0x1f)
{
tag = 0;
do
{
/* We silently ignore an overflow in the tag value. It is
not worth checking for it. */
tag <<= 7;
if (!length)
return premature_eof (ti);
c = *buf++; length--;
if (ti->nhdr >= DIM (ti->buf))
{
ti->err_string = "tag+length header too large";
return gpg_error (GPG_ERR_BAD_BER);
}
ti->buf[ti->nhdr++] = c;
tag |= c & 0x7f;
}
while (c & 0x80);
}
ti->tag = tag;
/* Get the length */
if (!length)
return premature_eof (ti);
c = *buf++; length--;
if (ti->nhdr >= DIM (ti->buf))
{
ti->err_string = "tag+length header too large";
return gpg_error (GPG_ERR_BAD_BER);
}
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 gpg_error (GPG_ERR_BAD_BER);
}
else
{
unsigned long len = 0;
int count = c & 0x7f;
if (count > sizeof (len) || count > sizeof (size_t))
return gpg_error (GPG_ERR_BAD_BER);
for (; count; count--)
{
len <<= 8;
if (!length)
return premature_eof (ti);
c = *buf++; length--;
if (ti->nhdr >= DIM (ti->buf))
{
ti->err_string = "tag+length header too large";
return gpg_error (GPG_ERR_BAD_BER);
}
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;
*buffer = buf;
*size = length;
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. */
gpg_error_t
_ksba_ber_write_tl (ksba_writer_t 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 gpg_error (GPG_ERR_NOT_IMPLEMENTED);
}
if (!tag && !class)
buf[buflen++] = 0; /* end tag */
else if (tag == TYPE_NULL && !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
objects - 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);
}
/* Encode TAG of CLASS in BUFFER. 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. It is assumed that the provide buffer is
large enough for storing the result - this is usually achieved by
using _ksba_ber_count_tl() in advance. Returns 0 in case of an
error or the length of the encoding.*/
size_t
_ksba_ber_encode_tl (unsigned char *buffer,
unsigned long tag,
enum tag_class class,
int constructed,
unsigned long length)
{
unsigned char *buf = buffer;
if (tag < 0x1f)
{
*buf = (class << 6) | tag;
if (constructed)
*buf |= 0x20;
buf++;
}
else
{
return 0; /*Not implemented*/
}
if (!tag && !class)
*buf++ = 0; /* end tag */
else if (tag == TYPE_NULL && !class)
*buf++ = 0; /* NULL tag */
else if (!length)
*buf++ = 0x80; /* indefinite length */
else if (length < 128)
*buf++ = 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++ = (0x80 | i);
if (i > 3)
*buf++ = length >> 24;
if (i > 2)
*buf++ = length >> 16;
if (i > 1)
*buf++ = length >> 8;
*buf++ = length;
}
return buf - buffer;
}
/* Calculate the length of the TL needed to encode a TAG of CLASS.
CONSTRUCTED is a flag telling whether the value is a constructed
one. LENGTH gives the length of the value; if it is 0 an
indefinite length is assumed. LENGTH is ignored for the NULL
tag. */
size_t
_ksba_ber_count_tl (unsigned long tag,
enum tag_class class,
int constructed,
unsigned long length)
{
int buflen = 0;
(void)constructed; /* Not used, but passed for uniformity of such calls. */
if (tag < 0x1f)
{
buflen++;
}
else
{
buflen++; /* assume one and let the actual write function bail out */
}
if (!tag && !class)
buflen++; /* end tag */
else if (tag == TYPE_NULL && !class)
buflen++; /* NULL tag */
else if (!length)
buflen++; /* indefinite length */
else if (length < 128)
buflen++;
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);
buflen++;
if (i > 3)
buflen++;
if (i > 2)
buflen++;
if (i > 1)
buflen++;
buflen++;
}
return buflen;
}

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