123 lines
2.8 KiB
C
123 lines
2.8 KiB
C
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/*
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* Copyright (c) 2017 Lev Walkin <vlm@lionet.info>.
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* All rights reserved.
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* Redistribution and modifications are permitted subject to BSD license.
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*/
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#include <asn_system.h>
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#include <asn_internal.h>
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#include <oer_support.h>
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/*
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* Fetch the length determinant (X.696 08/2015, #8.6) into *len_r.
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* RETURN VALUES:
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* 0: More data expected than bufptr contains.
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* -1: Fatal error deciphering length.
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* >0: Number of bytes used from bufptr.
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*/
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ssize_t
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oer_fetch_length(const void *bufptr, size_t size, size_t *len_r) {
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uint8_t first_byte;
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size_t len_len; /* Length of the length determinant */
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const uint8_t *b;
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const uint8_t *bend;
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size_t len;
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if(size == 0) {
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*len_r = 0;
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return 0;
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}
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first_byte = *(const uint8_t *)bufptr;
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if((first_byte & 0x80) == 0) { /* Short form */
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*len_r = first_byte; /* 0..127 */
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return 1;
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}
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len_len = (first_byte & 0x7f);
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if((1 + len_len) > size) {
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*len_r = 0;
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return 0;
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}
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b = (const uint8_t *)bufptr + 1;
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bend = b + len_len;
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for(; b < bend && *b == 0; b++) {
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/* Skip the leading 0-bytes */
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}
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if((bend - b) > (ssize_t)sizeof(size_t)) {
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/* Length is not representable by the native size_t type */
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*len_r = 0;
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return -1;
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}
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for(len = 0; b < bend; b++) {
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len = (len << 8) + *b;
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}
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if(len > RSIZE_MAX) { /* A bit of C11 validation */
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*len_r = 0;
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return -1;
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}
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*len_r = len;
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assert(len_len + 1 == (size_t)(bend - (const uint8_t *)bufptr));
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return len_len + 1;
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}
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/*
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* Serialize OER length. Returns the number of bytes serialized
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* or -1 if a given callback returned with negative result.
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*/
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ssize_t
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oer_serialize_length(size_t length, asn_app_consume_bytes_f *cb,
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void *app_key) {
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uint8_t scratch[1 + sizeof(length)];
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uint8_t *sp = scratch;
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int littleEndian = 1; /* Run-time detection */
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const uint8_t *pstart;
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const uint8_t *pend;
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const uint8_t *p;
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int add;
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if(length <= 127) {
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uint8_t b = length;
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if(cb(&b, 1, app_key) < 0) {
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return -1;
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}
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return 1;
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}
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if(*(char *)&littleEndian) {
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pstart = (const uint8_t *)&length + sizeof(length) - 1;
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pend = (const uint8_t *)&length;
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add = -1;
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} else {
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pstart = (const uint8_t *)&length;
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pend = pstart + sizeof(length);
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add = 1;
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}
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for(p = pstart; p != pend; p += add) {
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/* Skip leading zeros. */
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if(*p) break;
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}
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for(sp = scratch + 1; ; p += add) {
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*sp++ = *p;
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if(p == pend) break;
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}
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assert((sp - scratch) - 1 <= 0x7f);
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scratch[0] = 0x80 + ((sp - scratch) - 1);
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if(cb(scratch, sp - scratch, app_key) < 0) {
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return -1;
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}
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return sp - scratch;
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}
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