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1.1 root 1: /*
2: * Copyright (C) 2007 Michael Brown <[email protected]>.
3: *
4: * This program is free software; you can redistribute it and/or
5: * modify it under the terms of the GNU General Public License as
6: * published by the Free Software Foundation; either version 2 of the
7: * License, or any later version.
8: *
9: * This program is distributed in the hope that it will be useful, but
10: * WITHOUT ANY WARRANTY; without even the implied warranty of
11: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12: * General Public License for more details.
13: *
14: * You should have received a copy of the GNU General Public License
15: * along with this program; if not, write to the Free Software
16: * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17: */
18:
19: FILE_LICENCE ( GPL2_OR_LATER );
20:
21: #include <stdint.h>
22: #include <stddef.h>
23: #include <errno.h>
24: #include <ipxe/asn1.h>
25:
26: /** @file
27: *
28: * ASN.1 encoding
29: *
30: */
31:
32: /**
33: * Start parsing ASN.1 object
34: *
35: * @v cursor ASN.1 object cursor
36: * @v type Expected type
37: * @ret len Length of object body, or negative error
38: *
39: * The object cursor will be updated to point to the start of the
40: * object body (i.e. the first byte following the length byte(s)), and
41: * the length of the object body (i.e. the number of bytes until the
42: * following object tag, if any) is returned.
43: *
44: * If any error occurs (i.e. if the object is not of the expected
45: * type, or if we overflow beyond the end of the ASN.1 object), then
46: * the cursor will be invalidated and a negative value will be
47: * returned.
48: */
49: static int asn1_start ( struct asn1_cursor *cursor,
50: unsigned int type ) {
51: unsigned int len_len;
52: unsigned int len;
53: int rc;
54:
55: /* Sanity check */
56: if ( cursor->len < 2 /* Tag byte and first length byte */ ) {
57: if ( cursor->len )
58: DBGC ( cursor, "ASN1 %p too short\n", cursor );
59: rc = -EINVAL;
60: goto notfound;
61: }
62:
63: /* Check the tag byte */
64: if ( *( ( uint8_t * ) cursor->data ) != type ) {
65: DBGC ( cursor, "ASN1 %p type mismatch (expected %d, got %d)\n",
66: cursor, type, *( ( uint8_t * ) cursor->data ) );
67: rc = -ENXIO;
68: goto notfound;
69: }
70: cursor->data++;
71: cursor->len--;
72:
73: /* Extract length of the length field and sanity check */
74: len_len = *( ( uint8_t * ) cursor->data );
75: if ( len_len & 0x80 ) {
76: len_len = ( len_len & 0x7f );
77: cursor->data++;
78: cursor->len--;
79: } else {
80: len_len = 1;
81: }
82: if ( cursor->len < len_len ) {
83: DBGC ( cursor, "ASN1 %p bad length field length %d (max "
84: "%zd)\n", cursor, len_len, cursor->len );
85: rc = -EINVAL;
86: goto notfound;
87: }
88:
89: /* Extract the length and sanity check */
90: for ( len = 0 ; len_len ; len_len-- ) {
91: len <<= 8;
92: len |= *( ( uint8_t * ) cursor->data );
93: cursor->data++;
94: cursor->len--;
95: }
96: if ( cursor->len < len ) {
97: DBGC ( cursor, "ASN1 %p bad length %d (max %zd)\n",
98: cursor, len, cursor->len );
99: rc = -EINVAL;
100: goto notfound;
101: }
102:
103: return len;
104:
105: notfound:
106: cursor->data = NULL;
107: cursor->len = 0;
108: return rc;
109: }
110:
111: /**
112: * Enter ASN.1 object
113: *
114: * @v cursor ASN.1 object cursor
115: * @v type Expected type
116: * @ret rc Return status code
117: *
118: * The object cursor will be updated to point to the body of the
119: * current ASN.1 object. If any error occurs, the object cursor will
120: * be invalidated.
121: */
122: int asn1_enter ( struct asn1_cursor *cursor, unsigned int type ) {
123: int len;
124:
125: len = asn1_start ( cursor, type );
126: if ( len < 0 )
127: return len;
128:
129: cursor->len = len;
130: DBGC ( cursor, "ASN1 %p entered object type %02x (len %x)\n",
131: cursor, type, len );
132:
133: return 0;
134: }
135:
136: /**
137: * Skip ASN.1 object
138: *
139: * @v cursor ASN.1 object cursor
140: * @v type Expected type
141: * @ret rc Return status code
142: *
143: * The object cursor will be updated to point to the next ASN.1
144: * object. If any error occurs, the object cursor will be
145: * invalidated.
146: */
147: int asn1_skip ( struct asn1_cursor *cursor, unsigned int type ) {
148: int len;
149:
150: len = asn1_start ( cursor, type );
151: if ( len < 0 )
152: return len;
153:
154: cursor->data += len;
155: cursor->len -= len;
156: DBGC ( cursor, "ASN1 %p skipped object type %02x (len %x)\n",
157: cursor, type, len );
158:
159: if ( ! cursor->len ) {
160: DBGC ( cursor, "ASN1 %p reached end of object\n", cursor );
161: cursor->data = NULL;
162: return -ENOENT;
163: }
164:
165: return 0;
166: }
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