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948c656c66
openssl/ssl/quic/quic_wire_pkt.c
Hugo Landau 948c656c66 TX key update support, RX time and PN reporting, general refactoring 
- Adds an RX time field to the OSSL_QRX_PKT structure.

- Adds a timekeeping argument to ossl_demux_new which is used to determine
  packet reception time.

- Adds a decoded PN field to the OSSL_QRX_PKT structure.
  This has to be decoded by the QRX anyway, and its omission was an oversight.

- Key update support for the TX side.

- Minor refactoring.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18949)
2022-09-02 10:03:55 +02:00

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/*
* Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "internal/quic_wire_pkt.h"
int ossl_quic_hdr_protector_init(QUIC_HDR_PROTECTOR *hpr,
OSSL_LIB_CTX *libctx,
const char *propq,
uint32_t cipher_id,
const unsigned char *quic_hp_key,
size_t quic_hp_key_len)
{
const char *cipher_name = NULL;
switch (cipher_id) {
case QUIC_HDR_PROT_CIPHER_AES_128:
cipher_name = "AES-128-ECB";
break;
case QUIC_HDR_PROT_CIPHER_AES_256:
cipher_name = "AES-256-ECB";
break;
case QUIC_HDR_PROT_CIPHER_CHACHA:
cipher_name = "ChaCha20";
break;
default:
return 0;
}
hpr->cipher_ctx = EVP_CIPHER_CTX_new();
if (hpr->cipher_ctx == NULL)
return 0;
hpr->cipher = EVP_CIPHER_fetch(libctx, cipher_name, propq);
if (hpr->cipher == NULL
|| quic_hp_key_len != (size_t)EVP_CIPHER_get_key_length(hpr->cipher))
goto err;
if (!EVP_CipherInit_ex(hpr->cipher_ctx, hpr->cipher, NULL,
quic_hp_key, NULL, 1))
goto err;
hpr->libctx = libctx;
hpr->propq = propq;
hpr->cipher_id = cipher_id;
return 1;
err:
ossl_quic_hdr_protector_cleanup(hpr);
return 0;
}
void ossl_quic_hdr_protector_cleanup(QUIC_HDR_PROTECTOR *hpr)
{
EVP_CIPHER_CTX_free(hpr->cipher_ctx);
hpr->cipher_ctx = NULL;
EVP_CIPHER_free(hpr->cipher);
hpr->cipher = NULL;
}
static int hdr_generate_mask(QUIC_HDR_PROTECTOR *hpr,
const unsigned char *sample, size_t sample_len,
unsigned char *mask)
{
int l = 0;
unsigned char dst[16];
static const unsigned char zeroes[5] = {0};
size_t i;
if (hpr->cipher_id == QUIC_HDR_PROT_CIPHER_AES_128
|| hpr->cipher_id == QUIC_HDR_PROT_CIPHER_AES_256) {
if (sample_len < 16)
return 0;
if (!EVP_CipherInit_ex(hpr->cipher_ctx, NULL, NULL, NULL, NULL, 1)
|| !EVP_CipherUpdate(hpr->cipher_ctx, dst, &l, sample, 16))
return 0;
for (i = 0; i < 5; ++i)
mask[i] = dst[i];
} else if (hpr->cipher_id == QUIC_HDR_PROT_CIPHER_CHACHA) {
if (sample_len < 16)
return 0;
if (!EVP_CipherInit_ex(hpr->cipher_ctx, NULL, NULL, NULL, sample, 1)
|| !EVP_CipherUpdate(hpr->cipher_ctx, mask, &l,
zeroes, sizeof(zeroes)))
return 0;
} else {
assert(0);
return 0;
}
return 1;
}
int ossl_quic_hdr_protector_decrypt(QUIC_HDR_PROTECTOR *hpr,
QUIC_PKT_HDR_PTRS *ptrs)
{
return ossl_quic_hdr_protector_decrypt_fields(hpr,
ptrs->raw_sample,
ptrs->raw_sample_len,
ptrs->raw_start,
ptrs->raw_pn);
}
int ossl_quic_hdr_protector_decrypt_fields(QUIC_HDR_PROTECTOR *hpr,
const unsigned char *sample,
size_t sample_len,
unsigned char *first_byte,
unsigned char *pn_bytes)
{
unsigned char mask[5], pn_len, i;
if (!hdr_generate_mask(hpr, sample, sample_len, mask))
return 0;
*first_byte ^= mask[0] & ((*first_byte & 0x80) != 0 ? 0xf : 0x1f);
pn_len = (*first_byte & 0x3) + 1;
for (i = 0; i < pn_len; ++i)
pn_bytes[i] ^= mask[i + 1];
return 1;
}
int ossl_quic_hdr_protector_encrypt(QUIC_HDR_PROTECTOR *hpr,
QUIC_PKT_HDR_PTRS *ptrs)
{
return ossl_quic_hdr_protector_encrypt_fields(hpr,
ptrs->raw_sample,
ptrs->raw_sample_len,
ptrs->raw_start,
ptrs->raw_pn);
}
int ossl_quic_hdr_protector_encrypt_fields(QUIC_HDR_PROTECTOR *hpr,
const unsigned char *sample,
size_t sample_len,
unsigned char *first_byte,
unsigned char *pn_bytes)
{
unsigned char mask[5], pn_len, i;
if (!hdr_generate_mask(hpr, sample, sample_len, mask))
return 0;
pn_len = (*first_byte & 0x3) + 1;
for (i = 0; i < pn_len; ++i)
pn_bytes[i] ^= mask[i + 1];
*first_byte ^= mask[0] & ((*first_byte & 0x80) != 0 ? 0xf : 0x1f);
return 1;
}
int ossl_quic_wire_decode_pkt_hdr(PACKET *pkt,
size_t short_conn_id_len,
int partial,
QUIC_PKT_HDR *hdr,
QUIC_PKT_HDR_PTRS *ptrs)
{
unsigned int b0;
unsigned char *pn = NULL;
size_t l = PACKET_remaining(pkt);
if (ptrs != NULL) {
ptrs->raw_start = (unsigned char *)PACKET_data(pkt);
ptrs->raw_sample = NULL;
ptrs->raw_sample_len = 0;
ptrs->raw_pn = NULL;
}
if (l < QUIC_MIN_VALID_PKT_LEN
|| !PACKET_get_1(pkt, &b0))
return 0;
hdr->partial = partial;
if ((b0 & 0x80) == 0) {
/* Short header. */
if (short_conn_id_len > QUIC_MAX_CONN_ID_LEN)
return 0;
if ((b0 & 0x40) == 0 /* fixed bit not set? */
|| l < QUIC_MIN_VALID_PKT_LEN_CRYPTO)
return 0;
hdr->type = QUIC_PKT_TYPE_1RTT;
hdr->fixed = 1;
hdr->spin_bit = (b0 & 0x20) != 0;
if (partial) {
hdr->key_phase = 0; /* protected, zero for now */
hdr->pn_len = 0; /* protected, zero for now */
} else {
hdr->key_phase = (b0 & 0x4) != 0;
hdr->pn_len = (b0 & 0x3) + 1;
}
/* Copy destination connection ID field to header structure. */
if (!PACKET_copy_bytes(pkt, hdr->dst_conn_id.id, short_conn_id_len))
return 0;
hdr->dst_conn_id.id_len = short_conn_id_len;
/*
* Skip over the PN. If this is a partial decode, the PN length field
* currently has header protection applied. Thus we do not know the
* length of the PN but we are allowed to assume it is 4 bytes long at
* this stage.
*/
memset(hdr->pn, 0, sizeof(hdr->pn));
pn = (unsigned char *)PACKET_data(pkt);
if (partial) {
if (!PACKET_forward(pkt, sizeof(hdr->pn)))
return 0;
} else {
if (!PACKET_copy_bytes(pkt, hdr->pn, hdr->pn_len))
return 0;
}
/* Fields not used in short-header packets. */
hdr->version = 0;
hdr->src_conn_id.id_len = 0;
hdr->token = NULL;
hdr->token_len = 0;
/*
* Short-header packets always come last in a datagram, the length
* is the remainder of the buffer.
*/
hdr->len = PACKET_remaining(pkt);
hdr->data = PACKET_data(pkt);
/*
* Skip over payload. Since this is a short header packet, which cannot
* be followed by any other kind of packet, this advances us to the end
* of the datagram.
*/
if (!PACKET_forward(pkt, hdr->len))
return 0;
} else {
/* Long header. */
unsigned long version;
unsigned int dst_conn_id_len, src_conn_id_len, raw_type;
if (!PACKET_get_net_4(pkt, &version))
return 0;
/*
* All QUIC packets must have the fixed bit set, except exceptionally
* for Version Negotiation packets.
*/
if (version != 0 && (b0 & 0x40) == 0)
return 0;
if (!PACKET_get_1(pkt, &dst_conn_id_len)
|| dst_conn_id_len > QUIC_MAX_CONN_ID_LEN
|| !PACKET_copy_bytes(pkt, hdr->dst_conn_id.id, dst_conn_id_len)
|| !PACKET_get_1(pkt, &src_conn_id_len)
|| src_conn_id_len > QUIC_MAX_CONN_ID_LEN
|| !PACKET_copy_bytes(pkt, hdr->src_conn_id.id, src_conn_id_len))
return 0;
hdr->version = (uint32_t)version;
hdr->dst_conn_id.id_len = (unsigned char)dst_conn_id_len;
hdr->src_conn_id.id_len = (unsigned char)src_conn_id_len;
if (version == 0) {
/*
* Version negotiation packet. Version negotiation packets are
* identified by a version field of 0 and the type bits in the first
* byte are ignored (they may take any value, and we ignore them).
*/
hdr->type = QUIC_PKT_TYPE_VERSION_NEG;
hdr->fixed = (b0 & 0x40) != 0;
hdr->data = PACKET_data(pkt);
hdr->len = PACKET_remaining(pkt);
/* Version negotiation packets are always fully decoded. */
hdr->partial = 0;
/* Fields not used in version negotiation packets. */
hdr->pn_len = 0;
hdr->spin_bit = 0;
hdr->key_phase = 0;
hdr->token = NULL;
hdr->token_len = 0;
memset(hdr->pn, 0, sizeof(hdr->pn));
if (!PACKET_forward(pkt, hdr->len))
return 0;
} else if (version != QUIC_VERSION_1) {
/* Unknown version, do not decode. */
return 0;
} else {
if (l < QUIC_MIN_VALID_PKT_LEN_CRYPTO)
return 0;
/* Get long packet type and decode to QUIC_PKT_TYPE_*. */
raw_type = ((b0 >> 4) & 0x3);
switch (raw_type) {
case 0:
hdr->type = QUIC_PKT_TYPE_INITIAL;
break;
case 1:
hdr->type = QUIC_PKT_TYPE_0RTT;
break;
case 2:
hdr->type = QUIC_PKT_TYPE_HANDSHAKE;
break;
case 3:
hdr->type = QUIC_PKT_TYPE_RETRY;
break;
}
hdr->pn_len = 0;
hdr->fixed = 1;
/* Fields not used in long-header packets. */
hdr->spin_bit = 0;
hdr->key_phase = 0;
if (hdr->type == QUIC_PKT_TYPE_INITIAL) {
/* Initial packet. */
uint64_t token_len;
if (!PACKET_get_quic_vlint(pkt, &token_len)
|| token_len > SIZE_MAX
|| !PACKET_get_bytes(pkt, &hdr->token, token_len))
return 0;
hdr->token_len = (size_t)token_len;
if (token_len == 0)
hdr->token = NULL;
} else {
hdr->token = NULL;
hdr->token_len = 0;
}
if (hdr->type == QUIC_PKT_TYPE_RETRY) {
/* Retry packet. */
hdr->data = PACKET_data(pkt);
hdr->len = PACKET_remaining(pkt);
/* Retry packets are always fully decoded. */
hdr->partial = 0;
/* Fields not used in Retry packets. */
memset(hdr->pn, 0, sizeof(hdr->pn));
if (!PACKET_forward(pkt, hdr->len))
return 0;
} else {
/* Initial, 0-RTT or Handshake packet. */
uint64_t len;
hdr->pn_len = partial ? 0 : (b0 & 3) + 1;
if (!PACKET_get_quic_vlint(pkt, &len)
|| len < sizeof(hdr->pn)
|| len > PACKET_remaining(pkt))
return 0;
/*
* Skip over the PN. If this is a partial decode, the PN length
* field currently has header protection applied. Thus we do not
* know the length of the PN but we are allowed to assume it is
* 4 bytes long at this stage.
*/
pn = (unsigned char *)PACKET_data(pkt);
memset(hdr->pn, 0, sizeof(hdr->pn));
if (partial) {
if (!PACKET_forward(pkt, sizeof(hdr->pn)))
return 0;
hdr->len = (size_t)(len - sizeof(hdr->pn));
} else {
if (!PACKET_copy_bytes(pkt, hdr->pn, hdr->pn_len))
return 0;
hdr->len = (size_t)(len - hdr->pn_len);
}
hdr->data = PACKET_data(pkt);
/* Skip over packet body. */
if (!PACKET_forward(pkt, hdr->len))
return 0;
}
}
}
if (ptrs != NULL) {
ptrs->raw_pn = pn;
if (pn != NULL) {
ptrs->raw_sample = pn + 4;
ptrs->raw_sample_len = PACKET_end(pkt) - ptrs->raw_sample;
}
}
return 1;
}
int ossl_quic_wire_encode_pkt_hdr(WPACKET *pkt,
size_t short_conn_id_len,
const QUIC_PKT_HDR *hdr,
QUIC_PKT_HDR_PTRS *ptrs)
{
unsigned char b0;
size_t off_start, off_sample, off_pn;
unsigned char *start = WPACKET_get_curr(pkt);
if (!WPACKET_get_total_written(pkt, &off_start))
return 0;
if (ptrs != NULL) {
ptrs->raw_start = NULL;
ptrs->raw_sample = NULL;
ptrs->raw_sample_len = 0;
ptrs->raw_pn = 0;
}
/* Cannot serialize a partial header, or one whose DCID length is wrong. */
if (hdr->partial
|| (hdr->type == QUIC_PKT_TYPE_1RTT
&& hdr->dst_conn_id.id_len != short_conn_id_len))
return 0;
if (hdr->type == QUIC_PKT_TYPE_1RTT) {
/* Short header. */
/*
* Cannot serialize a header whose DCID length is wrong, or with an
* invalid PN length.
*/
if (hdr->dst_conn_id.id_len != short_conn_id_len
|| short_conn_id_len > QUIC_MAX_CONN_ID_LEN
|| hdr->pn_len < 1 || hdr->pn_len > 4)
return 0;
b0 = (hdr->spin_bit << 5)
| (hdr->key_phase << 2)
| (hdr->pn_len - 1)
| 0x40; /* fixed bit */
if (!WPACKET_put_bytes_u8(pkt, b0)
|| !WPACKET_memcpy(pkt, hdr->dst_conn_id.id, short_conn_id_len)
|| !WPACKET_get_total_written(pkt, &off_pn)
|| !WPACKET_memcpy(pkt, hdr->pn, hdr->pn_len))
return 0;
} else {
/* Long header. */
unsigned int raw_type;
if (hdr->dst_conn_id.id_len > QUIC_MAX_CONN_ID_LEN
|| hdr->src_conn_id.id_len > QUIC_MAX_CONN_ID_LEN)
return 0;
if (ossl_quic_pkt_type_has_pn(hdr->type)
&& (hdr->pn_len < 1 || hdr->pn_len > 4))
return 0;
switch (hdr->type) {
case QUIC_PKT_TYPE_VERSION_NEG:
if (hdr->version != 0)
return 0;
/* Version negotiation packets use zero for the type bits */
raw_type = 0;
break;
case QUIC_PKT_TYPE_INITIAL: raw_type = 0; break;
case QUIC_PKT_TYPE_0RTT: raw_type = 1; break;
case QUIC_PKT_TYPE_HANDSHAKE: raw_type = 2; break;
case QUIC_PKT_TYPE_RETRY: raw_type = 3; break;
default:
return 0;
}
b0 = (raw_type << 4) | 0x80; /* long */
if (hdr->type != QUIC_PKT_TYPE_VERSION_NEG || hdr->fixed)
b0 |= 0x40; /* fixed */
if (ossl_quic_pkt_type_has_pn(hdr->type))
b0 |= hdr->pn_len - 1;
if (!WPACKET_put_bytes_u8(pkt, b0)
|| !WPACKET_put_bytes_u32(pkt, hdr->version)
|| !WPACKET_put_bytes_u8(pkt, hdr->dst_conn_id.id_len)
|| !WPACKET_memcpy(pkt, hdr->dst_conn_id.id,
hdr->dst_conn_id.id_len)
|| !WPACKET_put_bytes_u8(pkt, hdr->src_conn_id.id_len)
|| !WPACKET_memcpy(pkt, hdr->src_conn_id.id,
hdr->src_conn_id.id_len))
return 0;
if (hdr->type == QUIC_PKT_TYPE_VERSION_NEG
|| hdr->type == QUIC_PKT_TYPE_RETRY) {
if (!WPACKET_reserve_bytes(pkt, hdr->len, NULL))
return 0;
return 1;
}
if (hdr->type == QUIC_PKT_TYPE_INITIAL) {
if (!WPACKET_quic_write_vlint(pkt, hdr->token_len)
|| !WPACKET_memcpy(pkt, hdr->token, hdr->token_len))
return 0;
}
if (!WPACKET_quic_write_vlint(pkt, hdr->len + hdr->pn_len)
|| !WPACKET_get_total_written(pkt, &off_pn)
|| !WPACKET_memcpy(pkt, hdr->pn, hdr->pn_len))
return 0;
}
if (!WPACKET_reserve_bytes(pkt, hdr->len, NULL))
return 0;
off_sample = off_pn + 4;
if (ptrs != NULL) {
ptrs->raw_start = start;
ptrs->raw_sample = start + (off_sample - off_start);
ptrs->raw_sample_len
= WPACKET_get_curr(pkt) + hdr->len - ptrs->raw_sample;
ptrs->raw_pn = start + (off_pn - off_start);
}
return 1;
}
int ossl_quic_wire_get_encoded_pkt_hdr_len(size_t short_conn_id_len,
const QUIC_PKT_HDR *hdr)
{
size_t len = 0, enclen;
/* Cannot serialize a partial header, or one whose DCID length is wrong. */
if (hdr->partial
|| (hdr->type == QUIC_PKT_TYPE_1RTT
&& hdr->dst_conn_id.id_len != short_conn_id_len))
return 0;
if (hdr->type == QUIC_PKT_TYPE_1RTT) {
/* Short header. */
/*
* Cannot serialize a header whose DCID length is wrong, or with an
* invalid PN length.
*/
if (hdr->dst_conn_id.id_len != short_conn_id_len
|| short_conn_id_len > QUIC_MAX_CONN_ID_LEN
|| hdr->pn_len < 1 || hdr->pn_len > 4)
return 0;
return 1 + short_conn_id_len + hdr->pn_len;
} else {
/* Long header. */
if (hdr->dst_conn_id.id_len > QUIC_MAX_CONN_ID_LEN
|| hdr->src_conn_id.id_len > QUIC_MAX_CONN_ID_LEN)
return 0;
len += 1 /* Initial byte */ + 4 /* Version */
+ 1 + hdr->dst_conn_id.id_len /* DCID Len, DCID */
+ 1 + hdr->src_conn_id.id_len /* SCID Len, SCID */
;
if (ossl_quic_pkt_type_has_pn(hdr->type)) {
if (hdr->pn_len < 1 || hdr->pn_len > 4)
return 0;
len += hdr->pn_len;
}
if (hdr->type == QUIC_PKT_TYPE_INITIAL) {
enclen = ossl_quic_vlint_encode_len(hdr->token_len);
if (!enclen)
return 0;
len += enclen;
}
if (!ossl_quic_pkt_type_must_be_last(hdr->type)) {
enclen = ossl_quic_vlint_encode_len(hdr->len);
if (!enclen)
return 0;
len += enclen;
}
return len;
}
}
int ossl_quic_wire_get_pkt_hdr_dst_conn_id(const unsigned char *buf,
size_t buf_len,
size_t short_conn_id_len,
QUIC_CONN_ID *dst_conn_id)
{
unsigned char b0;
size_t blen;
if (buf_len < QUIC_MIN_VALID_PKT_LEN
|| short_conn_id_len > QUIC_MAX_CONN_ID_LEN)
return 0;
b0 = buf[0];
if ((b0 & 0x80) != 0) {
/*
* Long header. We need 6 bytes (initial byte, 4 version bytes, DCID
* length byte to begin with). This is covered by the buf_len test
* above.
*/
/*
* If the version field is non-zero (meaning that this is not a Version
* Negotiation packet), the fixed bit must be set.
*/
if ((buf[1] || buf[2] || buf[3] || buf[4]) && (b0 & 0x40) == 0)
return 0;
blen = (size_t)buf[5]; /* DCID Length */
if (blen > QUIC_MAX_CONN_ID_LEN
|| buf_len < QUIC_MIN_VALID_PKT_LEN + blen)
return 0;
dst_conn_id->id_len = (unsigned char)blen;
memcpy(dst_conn_id->id, buf + 6, blen);
return 1;
} else {
/* Short header. */
if ((b0 & 0x40) == 0)
/* Fixed bit not set, not a valid QUIC packet header. */
return 0;
if (buf_len < QUIC_MIN_VALID_PKT_LEN_CRYPTO + short_conn_id_len)
return 0;
dst_conn_id->id_len = short_conn_id_len;
memcpy(dst_conn_id->id, buf + 1, short_conn_id_len);
return 1;
}
}
int ossl_quic_wire_decode_pkt_hdr_pn(const unsigned char *enc_pn,
size_t enc_pn_len,
QUIC_PN largest_pn,
QUIC_PN *res_pn)
{
int64_t expected_pn, truncated_pn, candidate_pn, pn_win, pn_hwin, pn_mask;
switch (enc_pn_len) {
case 1:
truncated_pn = enc_pn[0];
break;
case 2:
truncated_pn = ((QUIC_PN)enc_pn[0] << 8)
| (QUIC_PN)enc_pn[1];
break;
case 3:
truncated_pn = ((QUIC_PN)enc_pn[0] << 16)
| ((QUIC_PN)enc_pn[1] << 8)
| (QUIC_PN)enc_pn[2];
break;
case 4:
truncated_pn = ((QUIC_PN)enc_pn[0] << 24)
| ((QUIC_PN)enc_pn[1] << 16)
| ((QUIC_PN)enc_pn[2] << 8)
| (QUIC_PN)enc_pn[3];
break;
default:
return 0;
}
/* Implemented as per RFC 9000 Section A.3. */
expected_pn = largest_pn + 1;
pn_win = ((int64_t)1) << (enc_pn_len * 8);
pn_hwin = pn_win / 2;
pn_mask = pn_win - 1;
candidate_pn = (expected_pn & ~pn_mask) | truncated_pn;
if (candidate_pn <= expected_pn - pn_hwin
&& candidate_pn < (((int64_t)1) << 62) - pn_win)
*res_pn = candidate_pn + pn_win;
else if (candidate_pn > expected_pn + pn_hwin
&& candidate_pn >= pn_win)
*res_pn = candidate_pn - pn_win;
else
*res_pn = candidate_pn;
return 1;
}
/* From RFC 9000 Section A.2. Simplified implementation. */
int ossl_quic_wire_determine_pn_len(QUIC_PN pn,
QUIC_PN largest_acked)
{
uint64_t num_unacked
= (largest_acked == QUIC_PN_INVALID) ? pn + 1 : pn - largest_acked;
/*
* num_unacked \in [ 0, 2** 7] -> 1 byte
* num_unacked \in (2** 7, 2**15] -> 2 bytes
* num_unacked \in (2**15, 2**23] -> 3 bytes
* num_unacked \in (2**23, ] -> 4 bytes
*/
if (num_unacked <= (1U<<7)) return 1;
if (num_unacked <= (1U<<15)) return 2;
if (num_unacked <= (1U<<23)) return 3;
return 4;
}
int ossl_quic_wire_encode_pkt_hdr_pn(QUIC_PN pn,
unsigned char *enc_pn,
size_t enc_pn_len)
{
switch (enc_pn_len) {
case 1:
enc_pn[0] = (unsigned char)pn;
break;
case 2:
enc_pn[1] = (unsigned char)pn;
enc_pn[0] = (unsigned char)(pn >> 8);
break;
case 3:
enc_pn[2] = (unsigned char)pn;
enc_pn[1] = (unsigned char)(pn >> 8);
enc_pn[0] = (unsigned char)(pn >> 16);
break;
case 4:
enc_pn[3] = (unsigned char)pn;
enc_pn[2] = (unsigned char)(pn >> 8);
enc_pn[1] = (unsigned char)(pn >> 16);
enc_pn[0] = (unsigned char)(pn >> 24);
break;
default:
return 0;
}
return 1;
}
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