Permalink
Switch branches/tags
Nothing to show
Find file
Fetching contributors…
Cannot retrieve contributors at this time
284 lines (263 sloc) 7.49 KB
/*-
* Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved.
* Redistribution and modifications are permitted subject to BSD license.
*/
#include <asn_internal.h>
#undef ADVANCE
#define ADVANCE(num_bytes) do { \
size_t num = num_bytes; \
ptr = ((const char *)ptr) + num; \
size -= num; \
consumed_myself += num; \
} while(0)
#undef RETURN
#define RETURN(_code) do { \
asn_dec_rval_t rval; \
rval.code = _code; \
if(opt_ctx) opt_ctx->step = step; /* Save context */ \
if(_code == RC_OK || opt_ctx) \
rval.consumed = consumed_myself; \
else \
rval.consumed = 0; /* Context-free */ \
return rval; \
} while(0)
/*
* The BER decoder of any type.
*/
asn_dec_rval_t
ber_decode(asn_codec_ctx_t *opt_codec_ctx,
asn_TYPE_descriptor_t *type_descriptor,
void **struct_ptr, const void *ptr, size_t size) {
asn_codec_ctx_t s_codec_ctx;
/*
* Stack checker requires that the codec context
* must be allocated on the stack.
*/
if(opt_codec_ctx) {
if(opt_codec_ctx->max_stack_size) {
s_codec_ctx = *opt_codec_ctx;
opt_codec_ctx = &s_codec_ctx;
}
} else {
/* If context is not given, be security-conscious anyway */
memset(&s_codec_ctx, 0, sizeof(s_codec_ctx));
s_codec_ctx.max_stack_size = _ASN_DEFAULT_STACK_MAX;
opt_codec_ctx = &s_codec_ctx;
}
/*
* Invoke type-specific decoder.
*/
return type_descriptor->ber_decoder(opt_codec_ctx, type_descriptor,
struct_ptr, /* Pointer to the destination structure */
ptr, size, /* Buffer and its size */
0 /* Default tag mode is 0 */
);
}
/*
* Check the set of <TL<TL<TL...>>> tags matches the definition.
*/
asn_dec_rval_t
ber_check_tags(asn_codec_ctx_t *opt_codec_ctx,
asn_TYPE_descriptor_t *td, asn_struct_ctx_t *opt_ctx,
const void *ptr, size_t size, int tag_mode, int last_tag_form,
ber_tlv_len_t *last_length, int *opt_tlv_form) {
ssize_t consumed_myself = 0;
ssize_t tag_len;
ssize_t len_len;
ber_tlv_tag_t tlv_tag;
ber_tlv_len_t tlv_len;
ber_tlv_len_t limit_len = -1;
int expect_00_terminators = 0;
int tlv_constr = -1; /* If CHOICE, opt_tlv_form is not given */
int step = opt_ctx ? opt_ctx->step : 0; /* Where we left previously */
int tagno;
/*
* Make sure we didn't exceed the maximum stack size.
*/
if(_ASN_STACK_OVERFLOW_CHECK(opt_codec_ctx))
RETURN(RC_FAIL);
/*
* So what does all this implicit skip stuff mean?
* Imagine two types,
* A ::= [5] IMPLICIT T
* B ::= [2] EXPLICIT T
* Where T is defined as
* T ::= [4] IMPLICIT SEQUENCE { ... }
*
* Let's say, we are starting to decode type A, given the
* following TLV stream: <5> <0>. What does this mean?
* It means that the type A contains type T which is,
* in turn, empty.
* Remember though, that we are still in A. We cannot
* just pass control to the type T decoder. Why? Because
* the type T decoder expects <4> <0>, not <5> <0>.
* So, we must make sure we are going to receive <5> while
* still in A, then pass control to the T decoder, indicating
* that the tag <4> was implicitly skipped. The decoder of T
* hence will be prepared to treat <4> as valid tag, and decode
* it appropriately.
*/
tagno = step /* Continuing where left previously */
+ (tag_mode==1?-1:0)
;
ASN_DEBUG("ber_check_tags(%s, size=%ld, tm=%d, step=%d, tagno=%d)",
td->name, (long)size, tag_mode, step, tagno);
/* assert(td->tags_count >= 1) May not be the case for CHOICE or ANY */
if(tag_mode == 0 && tagno == td->tags_count) {
/*
* This must be the _untagged_ ANY type,
* which outermost tag isn't known in advance.
* Fetch the tag and length separately.
*/
tag_len = ber_fetch_tag(ptr, size, &tlv_tag);
switch(tag_len) {
case -1: RETURN(RC_FAIL);
case 0: RETURN(RC_WMORE);
}
tlv_constr = BER_TLV_CONSTRUCTED(ptr);
len_len = ber_fetch_length(tlv_constr,
(const char *)ptr + tag_len, size - tag_len, &tlv_len);
switch(len_len) {
case -1: RETURN(RC_FAIL);
case 0: RETURN(RC_WMORE);
}
ASN_DEBUG("Advancing %ld in ANY case",
(long)(tag_len + len_len));
ADVANCE(tag_len + len_len);
} else {
assert(tagno < td->tags_count); /* At least one loop */
}
for((void)tagno; tagno < td->tags_count; tagno++, step++) {
/*
* Fetch and process T from TLV.
*/
tag_len = ber_fetch_tag(ptr, size, &tlv_tag);
ASN_DEBUG("Fetching tag from {%p,%ld}: "
"len %ld, step %d, tagno %d got %s",
ptr, (long)size,
(long)tag_len, step, tagno,
ber_tlv_tag_string(tlv_tag));
switch(tag_len) {
case -1: RETURN(RC_FAIL);
case 0: RETURN(RC_WMORE);
}
tlv_constr = BER_TLV_CONSTRUCTED(ptr);
/*
* If {I}, don't check anything.
* If {I,B,C}, check B and C unless we're at I.
*/
if(tag_mode != 0 && step == 0) {
/*
* We don't expect tag to match here.
* It's just because we don't know how the tag
* is supposed to look like.
*/
} else {
assert(tagno >= 0); /* Guaranteed by the code above */
if(tlv_tag != td->tags[tagno]) {
/*
* Unexpected tag. Too bad.
*/
ASN_DEBUG("Expected: %s, "
"expectation failed (tn=%d, tm=%d)",
ber_tlv_tag_string(td->tags[tagno]),
tagno, tag_mode
);
RETURN(RC_FAIL);
}
}
/*
* Attention: if there are more tags expected,
* ensure that the current tag is presented
* in constructed form (it contains other tags!).
* If this one is the last one, check that the tag form
* matches the one given in descriptor.
*/
if(tagno < (td->tags_count - 1)) {
if(tlv_constr == 0) {
ASN_DEBUG("tlv_constr = %d, expfail",
tlv_constr);
RETURN(RC_FAIL);
}
} else {
if(last_tag_form != tlv_constr
&& last_tag_form != -1) {
ASN_DEBUG("last_tag_form %d != %d",
last_tag_form, tlv_constr);
RETURN(RC_FAIL);
}
}
/*
* Fetch and process L from TLV.
*/
len_len = ber_fetch_length(tlv_constr,
(const char *)ptr + tag_len, size - tag_len, &tlv_len);
ASN_DEBUG("Fetchinig len = %ld", (long)len_len);
switch(len_len) {
case -1: RETURN(RC_FAIL);
case 0: RETURN(RC_WMORE);
}
/*
* FIXME
* As of today, the chain of tags
* must either contain several indefinite length TLVs,
* or several definite length ones.
* No mixing is allowed.
*/
if(tlv_len == -1) {
/*
* Indefinite length.
*/
if(limit_len == -1) {
expect_00_terminators++;
} else {
ASN_DEBUG("Unexpected indefinite length "
"in a chain of definite lengths");
RETURN(RC_FAIL);
}
ADVANCE(tag_len + len_len);
continue;
} else {
if(expect_00_terminators) {
ASN_DEBUG("Unexpected definite length "
"in a chain of indefinite lengths");
RETURN(RC_FAIL);
}
}
/*
* Check that multiple TLVs specify ever decreasing length,
* which is consistent.
*/
if(limit_len == -1) {
limit_len = tlv_len + tag_len + len_len;
if(limit_len < 0) {
/* Too great tlv_len value? */
RETURN(RC_FAIL);
}
} else if(limit_len != tlv_len + tag_len + len_len) {
/*
* Inner TLV specifies length which is inconsistent
* with the outer TLV's length value.
*/
ASN_DEBUG("Outer TLV is %ld and inner is %ld",
(long)limit_len, (long)tlv_len);
RETURN(RC_FAIL);
}
ADVANCE(tag_len + len_len);
limit_len -= (tag_len + len_len);
if((ssize_t)size > limit_len) {
/*
* Make sure that we won't consume more bytes
* from the parent frame than the inferred limit.
*/
size = limit_len;
}
}
if(opt_tlv_form)
*opt_tlv_form = tlv_constr;
if(expect_00_terminators)
*last_length = -expect_00_terminators;
else
*last_length = tlv_len;
RETURN(RC_OK);
}