asn.c

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/* -*- c-basic-offset: 8 -*-
   rdesktop: A Remote Desktop Protocol client.
   ASN.1 utility functions
   Copyright 2012 Henrik Andersson <hean01@cendio.se> for Cendio AB
 
   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 3 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, see <http://www.gnu.org/licenses/>.
*/
 
#include "precomp.h"
 
 
/* Parse an ASN.1 BER header */
RD_BOOL
ber_parse_header(STREAM s, int tagval, int *length)
{
    int tag, len;
 
    if (tagval > 0xff)
    {
        in_uint16_be(s, tag);
    }
    else
    {
        in_uint8(s, tag);
    }
 
    if (tag != tagval)
    {
        error("expected tag %d, got %d\n", tagval, tag);
        return False;
    }
 
    in_uint8(s, len);
 
    if (len & 0x80)
    {
        len &= ~0x80;
        *length = 0;
        while (len--)
            next_be(s, *length);
    }
    else
        *length = len;
 
    return s_check(s);
}
 
/* Output an ASN.1 BER header */
void
ber_out_header(STREAM s, int tagval, int length)
{
    if (tagval > 0xff)
    {
        out_uint16_be(s, tagval);
    }
    else
    {
        out_uint8(s, tagval);
    }
 
    if (length >= 0x80)
    {
        out_uint8(s, 0x82);
        out_uint16_be(s, length);
    }
    else
        out_uint8(s, length);
}
 
/* Output an ASN.1 BER integer */
void
ber_out_integer(STREAM s, int value)
{
    ber_out_header(s, BER_TAG_INTEGER, 2);
    out_uint16_be(s, value);
}
 
RD_BOOL
ber_in_header(STREAM s, int *tagval, int *decoded_len)
{
    in_uint8(s, *tagval);
    in_uint8(s, *decoded_len);
 
    if (*decoded_len < 0x80)
        return True;
    else if (*decoded_len == 0x81)
    {
        in_uint8(s, *decoded_len);
        return True;
    }
    else if (*decoded_len == 0x82)
    {
        in_uint16_be(s, *decoded_len);
        return True;
    }
 
    return False;
}