krb5/asn.1/asn1_get.c

/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * src/lib/krb5/asn.1/asn1_get.c
 *
 * Copyright 1994 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 */

#include "asn1_get.h"

asn1_error_code
asn1_get_tag_2(asn1buf *buf, taginfo *t)
{
    asn1_error_code retval;

    if (buf == NULL || buf->base == NULL ||
        buf->bound - buf->next + 1 <= 0) {
        t->tagnum = ASN1_TAGNUM_CEILING; /* emphatically not an EOC tag */
        t->asn1class = UNIVERSAL;
        t->construction = PRIMITIVE;
        t->length = 0;
        t->indef = 0;
        return 0;
    }
    {
        /* asn1_get_id(buf, t) */
        asn1_tagnum tn=0;
        asn1_octet o;

#define ASN1_CLASS_MASK 0xC0
#define ASN1_CONSTRUCTION_MASK 0x20
#define ASN1_TAG_NUMBER_MASK 0x1F

        retval = asn1buf_remove_octet(buf,&o);
        if (retval)
            return retval;

        t->asn1class = (asn1_class)(o&ASN1_CLASS_MASK);
        t->construction = (asn1_construction)(o&ASN1_CONSTRUCTION_MASK);
        if ((o&ASN1_TAG_NUMBER_MASK) != ASN1_TAG_NUMBER_MASK) {
            /* low-tag-number form */
            t->tagnum = (asn1_tagnum)(o&ASN1_TAG_NUMBER_MASK);
        } else {
            /* high-tag-number form */
            do {
                retval = asn1buf_remove_octet(buf,&o);
                if (retval) return retval;
                tn = (tn<<7) + (asn1_tagnum)(o&0x7F);
            } while (o&0x80);
            t->tagnum = tn;
        }
    }

    {
        /* asn1_get_length(buf, t) */
        asn1_octet o;

        t->indef = 0;
        retval = asn1buf_remove_octet(buf,&o);
        if (retval) return retval;
        if ((o&0x80) == 0) {
            t->length = (int)(o&0x7F);
        } else {
            int num;
            int len=0;

            for (num = (int)(o&0x7F); num>0; num--) {
                retval = asn1buf_remove_octet(buf,&o);
                if (retval) return retval;
                len = (len<<8) + (int)o;
            }
            if (len < 0)
                return ASN1_OVERRUN;
            if (!len)
                t->indef = 1;
            t->length = len;
        }
    }
    if (t->indef && t->construction != CONSTRUCTED)
        return ASN1_MISMATCH_INDEF;
    return 0;
}

asn1_error_code
asn1_get_sequence(asn1buf *buf, unsigned int *retlen, int *indef)
{
    taginfo t;
    asn1_error_code retval;

    retval = asn1_get_tag_2(buf, &t);
    if (retval)
        return retval;
    if (t.asn1class != UNIVERSAL || t.construction != CONSTRUCTED ||
        t.tagnum != ASN1_SEQUENCE)
        return ASN1_BAD_ID;
    if (retlen)
        *retlen = t.length;
    if (indef)
        *indef = t.indef;
    return 0;
}