2
* Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved.
3
* Redistribution and modifications are permitted subject to BSD license.
5
#include <asn_internal.h>
8
#define ADVANCE(num_bytes) do { \
9
size_t num = num_bytes; \
10
ptr = ((const char *)ptr) + num; \
12
consumed_myself += num; \
15
#define RETURN(_code) do { \
16
asn_dec_rval_t rval; \
18
if(opt_ctx) opt_ctx->step = step; /* Save context */ \
19
if(_code == RC_OK || opt_ctx) \
20
rval.consumed = consumed_myself; \
22
rval.consumed = 0; /* Context-free */ \
27
* The BER decoder of any type.
30
ber_decode(asn_codec_ctx_t *opt_codec_ctx,
31
asn_TYPE_descriptor_t *type_descriptor,
32
void **struct_ptr, const void *ptr, size_t size) {
33
asn_codec_ctx_t s_codec_ctx;
36
* Stack checker requires that the codec context
37
* must be allocated on the stack.
40
if(opt_codec_ctx->max_stack_size) {
41
s_codec_ctx = *opt_codec_ctx;
42
opt_codec_ctx = &s_codec_ctx;
45
/* If context is not given, be security-conscious anyway */
46
memset(&s_codec_ctx, 0, sizeof(s_codec_ctx));
47
s_codec_ctx.max_stack_size = _ASN_DEFAULT_STACK_MAX;
48
opt_codec_ctx = &s_codec_ctx;
52
* Invoke type-specific decoder.
54
return type_descriptor->ber_decoder(opt_codec_ctx, type_descriptor,
55
struct_ptr, /* Pointer to the destination structure */
56
ptr, size, /* Buffer and its size */
57
0 /* Default tag mode is 0 */
62
* Check the set of <TL<TL<TL...>>> tags matches the definition.
65
ber_check_tags(asn_codec_ctx_t *opt_codec_ctx,
66
asn_TYPE_descriptor_t *td, asn_struct_ctx_t *opt_ctx,
67
const void *ptr, size_t size, int tag_mode, int last_tag_form,
68
ber_tlv_len_t *last_length, int *opt_tlv_form) {
69
ssize_t consumed_myself = 0;
72
ber_tlv_tag_t tlv_tag;
73
ber_tlv_len_t tlv_len;
74
ber_tlv_len_t limit_len = -1;
75
int expect_00_terminators = 0;
76
int tlv_constr = -1; /* If CHOICE, opt_tlv_form is not given */
77
int step = opt_ctx ? opt_ctx->step : 0; /* Where we left previously */
81
* Make sure we didn't exceed the maximum stack size.
83
if(_ASN_STACK_OVERFLOW_CHECK(opt_codec_ctx))
87
* So what does all this implicit skip stuff mean?
89
* A ::= [5] IMPLICIT T
90
* B ::= [2] EXPLICIT T
91
* Where T is defined as
92
* T ::= [4] IMPLICIT SEQUENCE { ... }
94
* Let's say, we are starting to decode type A, given the
95
* following TLV stream: <5> <0>. What does this mean?
96
* It means that the type A contains type T which is,
98
* Remember though, that we are still in A. We cannot
99
* just pass control to the type T decoder. Why? Because
100
* the type T decoder expects <4> <0>, not <5> <0>.
101
* So, we must make sure we are going to receive <5> while
102
* still in A, then pass control to the T decoder, indicating
103
* that the tag <4> was implicitly skipped. The decoder of T
104
* hence will be prepared to treat <4> as valid tag, and decode
108
tagno = step /* Continuing where left previously */
111
ASN_DEBUG("ber_check_tags(%s, size=%ld, tm=%d, step=%d, tagno=%d)",
112
td->name, (long)size, tag_mode, step, tagno);
113
/* assert(td->tags_count >= 1) May not be the case for CHOICE or ANY */
115
if(tag_mode == 0 && tagno == td->tags_count) {
117
* This must be the _untagged_ ANY type,
118
* which outermost tag isn't known in advance.
119
* Fetch the tag and length separately.
121
tag_len = ber_fetch_tag(ptr, size, &tlv_tag);
123
case -1: RETURN(RC_FAIL);
124
case 0: RETURN(RC_WMORE);
126
tlv_constr = BER_TLV_CONSTRUCTED(ptr);
127
len_len = ber_fetch_length(tlv_constr,
128
(const char *)ptr + tag_len, size - tag_len, &tlv_len);
130
case -1: RETURN(RC_FAIL);
131
case 0: RETURN(RC_WMORE);
133
ASN_DEBUG("Advancing %ld in ANY case",
134
(long)(tag_len + len_len));
135
ADVANCE(tag_len + len_len);
137
assert(tagno < td->tags_count); /* At least one loop */
139
for((void)tagno; tagno < td->tags_count; tagno++, step++) {
142
* Fetch and process T from TLV.
144
tag_len = ber_fetch_tag(ptr, size, &tlv_tag);
145
ASN_DEBUG("Fetching tag from {%p,%ld}: "
146
"len %ld, step %d, tagno %d got %s",
148
(long)tag_len, step, tagno,
149
ber_tlv_tag_string(tlv_tag));
151
case -1: RETURN(RC_FAIL);
152
case 0: RETURN(RC_WMORE);
155
tlv_constr = BER_TLV_CONSTRUCTED(ptr);
158
* If {I}, don't check anything.
159
* If {I,B,C}, check B and C unless we're at I.
161
if(tag_mode != 0 && step == 0) {
163
* We don't expect tag to match here.
164
* It's just because we don't know how the tag
165
* is supposed to look like.
168
assert(tagno >= 0); /* Guaranteed by the code above */
169
if(tlv_tag != td->tags[tagno]) {
171
* Unexpected tag. Too bad.
173
ASN_DEBUG("Expected: %s, "
174
"expectation failed (tn=%d, tm=%d)",
175
ber_tlv_tag_string(td->tags[tagno]),
183
* Attention: if there are more tags expected,
184
* ensure that the current tag is presented
185
* in constructed form (it contains other tags!).
186
* If this one is the last one, check that the tag form
187
* matches the one given in descriptor.
189
if(tagno < (td->tags_count - 1)) {
190
if(tlv_constr == 0) {
191
ASN_DEBUG("tlv_constr = %d, expfail",
196
if(last_tag_form != tlv_constr
197
&& last_tag_form != -1) {
198
ASN_DEBUG("last_tag_form %d != %d",
199
last_tag_form, tlv_constr);
205
* Fetch and process L from TLV.
207
len_len = ber_fetch_length(tlv_constr,
208
(const char *)ptr + tag_len, size - tag_len, &tlv_len);
209
ASN_DEBUG("Fetchinig len = %ld", (long)len_len);
211
case -1: RETURN(RC_FAIL);
212
case 0: RETURN(RC_WMORE);
217
* As of today, the chain of tags
218
* must either contain several indefinite length TLVs,
219
* or several definite length ones.
220
* No mixing is allowed.
226
if(limit_len == -1) {
227
expect_00_terminators++;
229
ASN_DEBUG("Unexpected indefinite length "
230
"in a chain of definite lengths");
233
ADVANCE(tag_len + len_len);
236
if(expect_00_terminators) {
237
ASN_DEBUG("Unexpected definite length "
238
"in a chain of indefinite lengths");
244
* Check that multiple TLVs specify ever decreasing length,
245
* which is consistent.
247
if(limit_len == -1) {
248
limit_len = tlv_len + tag_len + len_len;
250
/* Too great tlv_len value? */
253
} else if(limit_len != tlv_len + tag_len + len_len) {
255
* Inner TLV specifies length which is inconsistent
256
* with the outer TLV's length value.
258
ASN_DEBUG("Outer TLV is %ld and inner is %ld",
259
(long)limit_len, (long)tlv_len);
263
ADVANCE(tag_len + len_len);
265
limit_len -= (tag_len + len_len);
266
if((ssize_t)size > limit_len) {
268
* Make sure that we won't consume more bytes
269
* from the parent frame than the inferred limit.
276
*opt_tlv_form = tlv_constr;
277
if(expect_00_terminators)
278
*last_length = -expect_00_terminators;
280
*last_length = tlv_len;