1/*
2 * src/lib/krb5/asn.1/asn1_get.c
3 *
4 * Copyright 1994 by the Massachusetts Institute of Technology.
5 * All Rights Reserved.
6 *
7 * Export of this software from the United States of America may
8 *   require a specific license from the United States Government.
9 *   It is the responsibility of any person or organization contemplating
10 *   export to obtain such a license before exporting.
11 *
12 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
13 * distribute this software and its documentation for any purpose and
14 * without fee is hereby granted, provided that the above copyright
15 * notice appear in all copies and that both that copyright notice and
16 * this permission notice appear in supporting documentation, and that
17 * the name of M.I.T. not be used in advertising or publicity pertaining
18 * to distribution of the software without specific, written prior
19 * permission.  Furthermore if you modify this software you must label
20 * your software as modified software and not distribute it in such a
21 * fashion that it might be confused with the original M.I.T. software.
22 * M.I.T. makes no representations about the suitability of
23 * this software for any purpose.  It is provided "as is" without express
24 * or implied warranty.
25 */
26
27#include "asn1_get.h"
28
29asn1_error_code
30asn1_get_tag_2(asn1buf *buf, taginfo *t)
31{
32    asn1_error_code retval;
33
34    if (buf == NULL || buf->base == NULL ||
35	buf->bound - buf->next + 1 <= 0) {
36	t->tagnum = ASN1_TAGNUM_CEILING; /* emphatically not an EOC tag */
37	t->asn1class = UNIVERSAL;
38	t->construction = PRIMITIVE;
39	t->length = 0;
40	t->indef = 0;
41	return 0;
42    }
43    {
44	/* asn1_get_id(buf, t) */
45	asn1_tagnum tn=0;
46	asn1_octet o;
47
48#define ASN1_CLASS_MASK 0xC0
49#define ASN1_CONSTRUCTION_MASK 0x20
50#define ASN1_TAG_NUMBER_MASK 0x1F
51
52	retval = asn1buf_remove_octet(buf,&o);
53	if (retval)
54	    return retval;
55
56	t->asn1class = (asn1_class)(o&ASN1_CLASS_MASK);
57	t->construction = (asn1_construction)(o&ASN1_CONSTRUCTION_MASK);
58	if ((o&ASN1_TAG_NUMBER_MASK) != ASN1_TAG_NUMBER_MASK){
59	    /* low-tag-number form */
60	    t->tagnum = (asn1_tagnum)(o&ASN1_TAG_NUMBER_MASK);
61	} else {
62	    /* high-tag-number form */
63	    do {
64		retval = asn1buf_remove_octet(buf,&o);
65		if (retval) return retval;
66		tn = (tn<<7) + (asn1_tagnum)(o&0x7F);
67	    }while(o&0x80);
68	    t->tagnum = tn;
69	}
70    }
71
72    {
73	/* asn1_get_length(buf, t) */
74	asn1_octet o;
75
76	t->indef = 0;
77	retval = asn1buf_remove_octet(buf,&o);
78	if (retval) return retval;
79	if ((o&0x80) == 0) {
80	    t->length = (int)(o&0x7F);
81	} else {
82	    int num;
83	    int len=0;
84
85	    for (num = (int)(o&0x7F); num>0; num--) {
86		retval = asn1buf_remove_octet(buf,&o);
87		if(retval) return retval;
88		len = (len<<8) + (int)o;
89	    }
90	    if (len < 0)
91		return ASN1_OVERRUN;
92	    if (!len)
93		t->indef = 1;
94	    t->length = len;
95	}
96    }
97    if (t->indef && t->construction != CONSTRUCTED)
98	return ASN1_MISMATCH_INDEF;
99    return 0;
100}
101
102asn1_error_code asn1_get_sequence(asn1buf *buf, unsigned int *retlen, int *indef)
103{
104    taginfo t;
105    asn1_error_code retval;
106
107    retval = asn1_get_tag_2(buf, &t);
108    if (retval)
109	return retval;
110    if (t.asn1class != UNIVERSAL || t.construction != CONSTRUCTED ||
111	t.tagnum != ASN1_SEQUENCE)
112	return ASN1_BAD_ID;
113    if (retlen)
114	*retlen = t.length;
115    if (indef)
116	*indef = t.indef;
117    return 0;
118}
119