aboutsummaryrefslogtreecommitdiffstats
path: root/gpxe/src/crypto/asn1.c
blob: 154a8a840e9942dd7cd127d947560d31cfcb4faf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
/*
 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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 2 of the
 * License, or 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, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <stddef.h>
#include <errno.h>
#include <gpxe/asn1.h>

/** @file
 *
 * ASN.1 encoding
 *
 */

/**
 * Start parsing ASN.1 object
 *
 * @v cursor		ASN.1 object cursor
 * @v type		Expected type
 * @ret len		Length of object body, or negative error
 *
 * The object cursor will be updated to point to the start of the
 * object body (i.e. the first byte following the length byte(s)), and
 * the length of the object body (i.e. the number of bytes until the
 * following object tag, if any) is returned.
 *
 * If any error occurs (i.e. if the object is not of the expected
 * type, or if we overflow beyond the end of the ASN.1 object), then
 * the cursor will be invalidated and a negative value will be
 * returned.
 */
static int asn1_start ( struct asn1_cursor *cursor,
			       unsigned int type ) {
	unsigned int len_len;
	unsigned int len;
	int rc;

	/* Sanity check */
	if ( cursor->len < 2 /* Tag byte and first length byte */ ) {
		if ( cursor->len )
			DBGC ( cursor, "ASN1 %p too short\n", cursor );
		rc = -EINVAL;
		goto notfound;
	}

	/* Check the tag byte */
	if ( *( ( uint8_t * ) cursor->data ) != type ) {
		DBGC ( cursor, "ASN1 %p type mismatch (expected %d, got %d)\n",
		       cursor, type, *( ( uint8_t * ) cursor->data ) );
		rc = -ENXIO;
		goto notfound;
	}
	cursor->data++;
	cursor->len--;

	/* Extract length of the length field and sanity check */
	len_len = *( ( uint8_t * ) cursor->data );
	if ( len_len & 0x80 ) {
		len_len = ( len_len & 0x7f );
		cursor->data++;
		cursor->len--;
	} else {
		len_len = 1;
	}
	if ( cursor->len < len_len ) {
		DBGC ( cursor, "ASN1 %p bad length field length %d (max "
		       "%zd)\n", cursor, len_len, cursor->len );
		rc = -EINVAL;
		goto notfound;
	}

	/* Extract the length and sanity check */
	for ( len = 0 ; len_len ; len_len-- ) {
		len <<= 8;
		len |= *( ( uint8_t * ) cursor->data );
		cursor->data++;
		cursor->len--;
	}
	if ( cursor->len < len ) {
		DBGC ( cursor, "ASN1 %p bad length %d (max %zd)\n",
		       cursor, len, cursor->len );
		rc = -EINVAL;
		goto notfound;
	}

	return len;

 notfound:
	cursor->data = NULL;
	cursor->len = 0;
	return rc;
}

/**
 * Enter ASN.1 object
 *
 * @v cursor		ASN.1 object cursor
 * @v type		Expected type
 * @ret rc		Return status code
 *
 * The object cursor will be updated to point to the body of the
 * current ASN.1 object.  If any error occurs, the object cursor will
 * be invalidated.
 */
int asn1_enter ( struct asn1_cursor *cursor, unsigned int type ) {
	int len;

	len = asn1_start ( cursor, type );
	if ( len < 0 )
		return len;

	cursor->len = len;
	DBGC ( cursor, "ASN1 %p entered object type %02x (len %x)\n",
	       cursor, type, len );

	return 0;
}

/**
 * Skip ASN.1 object
 *
 * @v cursor		ASN.1 object cursor
 * @v type		Expected type
 * @ret rc		Return status code
 *
 * The object cursor will be updated to point to the next ASN.1
 * object.  If any error occurs, the object cursor will be
 * invalidated.
 */
int asn1_skip ( struct asn1_cursor *cursor, unsigned int type ) {
	int len;

	len = asn1_start ( cursor, type );
	if ( len < 0 )
		return len;

	cursor->data += len;
	cursor->len -= len;
	DBGC ( cursor, "ASN1 %p skipped object type %02x (len %x)\n",
	       cursor, type, len );

	if ( ! cursor->len ) {
		DBGC ( cursor, "ASN1 %p reached end of object\n", cursor );
		cursor->data = NULL;
		return -ENOENT;
	}

	return 0;
}