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/*-
* 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>
#include <ber_tlv_length.h>
#include <ber_tlv_tag.h>

ssize_t
ber_fetch_length(int _is_constructed, const void *bufptr, size_t size,
ber_tlv_len_t *len_r) {
const uint8_t *buf = (const uint8_t *)bufptr;
unsigned oct;

if(size == 0)
return 0; /* Want more */

oct = *(const uint8_t *)buf;
if((oct & 0x80) == 0) {
/*
* Short definite length.
*/
*len_r = oct; /* & 0x7F */
return 1;
} else {
ber_tlv_len_t len;
size_t skipped;

if(_is_constructed && oct == 0x80) {
*len_r = -1; /* Indefinite length */
return 1;
}

if(oct == 0xff) {
/* Reserved in standard for future use. */
return -1;
}

oct &= 0x7F; /* Leave only the 7 LS bits */
for(len = 0, buf++, skipped = 1;
oct && (++skipped <= size); buf++, oct--) {

len = (len << 8) | *buf;
if(len < 0
|| (len >> ((8 * sizeof(len)) - 8) && oct > 1)) {
/*
* Too large length value.
*/
return -1;
}
}

if(oct == 0) {
ber_tlv_len_t lenplusepsilon = (size_t)len + 1024;
/*
* Here length may be very close or equal to 2G.
* However, the arithmetics used in some decoders
* may add some (small) quantities to the length,
* to check the resulting value against some limits.
* This may result in integer wrap-around, which
* we try to avoid by checking it earlier here.
*/
if(lenplusepsilon < 0) {
/* Too large length value */
return -1;
}

*len_r = len;
return skipped;
}

return 0; /* Want more */
}

}

ssize_t
ber_skip_length(asn_codec_ctx_t *opt_codec_ctx,
int _is_constructed, const void *ptr, size_t size) {
ber_tlv_len_t vlen; /* Length of V in TLV */
ssize_t tl; /* Length of L in TLV */
ssize_t ll; /* Length of L in TLV */
size_t skip;

/*
* Make sure we didn't exceed the maximum stack size.
*/
if(_ASN_STACK_OVERFLOW_CHECK(opt_codec_ctx))
return -1;

/*
* Determine the size of L in TLV.
*/
ll = ber_fetch_length(_is_constructed, ptr, size, &vlen);
if(ll <= 0) return ll;

/*
* Definite length.
*/
if(vlen >= 0) {
skip = ll + vlen;
if(skip > size)
return 0; /* Want more */
return skip;
}

/*
* Indefinite length!
*/
ASN_DEBUG("Skipping indefinite length");
for(skip = ll, ptr = ((const char *)ptr) + ll, size -= ll;;) {
ber_tlv_tag_t tag;

/* Fetch the tag */
tl = ber_fetch_tag(ptr, size, &tag);
if(tl <= 0) return tl;

ll = ber_skip_length(opt_codec_ctx,
BER_TLV_CONSTRUCTED(ptr),
((const char *)ptr) + tl, size - tl);
if(ll <= 0) return ll;

skip += tl + ll;

/*
* This may be the end of the indefinite length structure,
* two consecutive 0 octets.
* Check if it is true.
*/
if(((const uint8_t *)ptr)[0] == 0
&& ((const uint8_t *)ptr)[1] == 0)
return skip;

ptr = ((const char *)ptr) + tl + ll;
size -= tl + ll;
  }

/* UNREACHABLE */
}

size_t
der_tlv_length_serialize(ber_tlv_len_t len, void *bufp, size_t size) {
size_t required_size; /* Size of len encoding */
uint8_t *buf = (uint8_t *)bufp;
uint8_t *end;
size_t i;

if(len <= 127) {
/* Encoded in 1 octet */
if(size) *buf = (uint8_t)len;
return 1;
}

/*
* Compute the size of the subsequent bytes.
*/
for(required_size = 1, i = 8; i < 8 * sizeof(len); i += 8) {
if(len >> i)
required_size++;
else
break;
}

if(size <= required_size)
return required_size + 1;

*buf++ = (uint8_t)(0x80 | required_size); /* Length of the encoding */

/*
* Produce the len encoding, space permitting.
*/
end = buf + required_size;
for(i -= 8; buf < end; i -= 8, buf++)
*buf = (uint8_t)(len >> i);

return required_size + 1;
}

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