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Group d1_both.c by sending and receiving handshake messages. 

This file is still kind of a mess, but put the two halves together at least.

Change-Id: Ib21d9c4a7f4864cf80e521f7d0ebec029e5955a1
Reviewed-on: https://boringssl-review.googlesource.com/8502
Reviewed-by: Adam Langley <agl@google.com>
kris/onging/CECPQ3_patch15
David Benjamin 8 years ago
committed by Adam Langley
parent
32a3780bab
commit
9d632f4582
1 changed files with 422 additions and 416 deletions
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  1. +422
    -416
      ssl/d1_both.c

+ 422
- 416
ssl/d1_both.c View File

@@ -139,6 +139,9 @@ static const unsigned int kMinMTU = 256 - 28;
* the underlying BIO supplies one. */
static const unsigned int kDefaultMTU = 1500 - 28;


/* Receiving handshake messages. */

static void dtls1_hm_fragment_free(hm_fragment *frag) {
if (frag == NULL) {
return;
@@ -235,411 +238,137 @@ static void dtls1_hm_fragment_mark(hm_fragment *frag, size_t start,
frag->reassembly = NULL;
}

static void dtls1_update_mtu(SSL *ssl) {
/* TODO(davidben): What is this code doing and do we need it? */
if (ssl->d1->mtu < dtls1_min_mtu() &&
!(SSL_get_options(ssl) & SSL_OP_NO_QUERY_MTU)) {
long mtu = BIO_ctrl(ssl->wbio, BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
if (mtu >= 0 && mtu <= (1 << 30) && (unsigned)mtu >= dtls1_min_mtu()) {
ssl->d1->mtu = (unsigned)mtu;
} else {
ssl->d1->mtu = kDefaultMTU;
BIO_ctrl(ssl->wbio, BIO_CTRL_DGRAM_SET_MTU, ssl->d1->mtu, NULL);
}
}

/* The MTU should be above the minimum now. */
assert(ssl->d1->mtu >= dtls1_min_mtu());
/* dtls1_is_next_message_complete returns one if the next handshake message is
* complete and zero otherwise. */
static int dtls1_is_next_message_complete(SSL *ssl) {
hm_fragment *frag = ssl->d1->incoming_messages[ssl->d1->handshake_read_seq %
SSL_MAX_HANDSHAKE_FLIGHT];
return frag != NULL && frag->reassembly == NULL;
}

/* dtls1_max_record_size returns the maximum record body length that may be
* written without exceeding the MTU. It accounts for any buffering installed on
* the write BIO. If no record may be written, it returns zero. */
static size_t dtls1_max_record_size(SSL *ssl) {
size_t ret = ssl->d1->mtu;
size_t overhead = ssl_max_seal_overhead(ssl);
if (ret <= overhead) {
return 0;
/* dtls1_get_incoming_message returns the incoming message corresponding to
* |msg_hdr|. If none exists, it creates a new one and inserts it in the
* queue. Otherwise, it checks |msg_hdr| is consistent with the existing one. It
* returns NULL on failure. The caller does not take ownership of the result. */
static hm_fragment *dtls1_get_incoming_message(
SSL *ssl, const struct hm_header_st *msg_hdr) {
if (msg_hdr->seq < ssl->d1->handshake_read_seq ||
msg_hdr->seq - ssl->d1->handshake_read_seq >= SSL_MAX_HANDSHAKE_FLIGHT) {
return NULL;
}
ret -= overhead;

size_t pending = BIO_wpending(ssl->wbio);
if (ret <= pending) {
return 0;
size_t idx = msg_hdr->seq % SSL_MAX_HANDSHAKE_FLIGHT;
hm_fragment *frag = ssl->d1->incoming_messages[idx];
if (frag != NULL) {
assert(frag->msg_header.seq == msg_hdr->seq);
/* The new fragment must be compatible with the previous fragments from this
* message. */
if (frag->msg_header.type != msg_hdr->type ||
frag->msg_header.msg_len != msg_hdr->msg_len) {
OPENSSL_PUT_ERROR(SSL, SSL_R_FRAGMENT_MISMATCH);
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
return NULL;
}
return frag;
}
ret -= pending;

return ret;
/* This is the first fragment from this message. */
frag = dtls1_hm_fragment_new(msg_hdr->msg_len);
if (frag == NULL) {
return NULL;
}
memcpy(&frag->msg_header, msg_hdr, sizeof(*msg_hdr));
ssl->d1->incoming_messages[idx] = frag;
return frag;
}

static int dtls1_write_change_cipher_spec(SSL *ssl,
enum dtls1_use_epoch_t use_epoch) {
dtls1_update_mtu(ssl);
/* dtls1_process_handshake_record reads a handshake record and processes it. It
* returns one if the record was successfully processed and 0 or -1 on error. */
static int dtls1_process_handshake_record(SSL *ssl) {
SSL3_RECORD *rr = &ssl->s3->rrec;

/* During the handshake, wbio is buffered to pack messages together. Flush the
* buffer if the ChangeCipherSpec would not fit in a packet. */
if (dtls1_max_record_size(ssl) == 0) {
int ret = BIO_flush(ssl->wbio);
start:
if (rr->length == 0) {
int ret = dtls1_get_record(ssl);
if (ret <= 0) {
ssl->rwstate = SSL_WRITING;
return ret;
}
}

static const uint8_t kChangeCipherSpec[1] = {SSL3_MT_CCS};
int ret =
dtls1_write_record(ssl, SSL3_RT_CHANGE_CIPHER_SPEC, kChangeCipherSpec,
sizeof(kChangeCipherSpec), use_epoch);
if (ret <= 0) {
return ret;
}

ssl_do_msg_callback(ssl, 1 /* write */, ssl->version,
SSL3_RT_CHANGE_CIPHER_SPEC, kChangeCipherSpec,
sizeof(kChangeCipherSpec));
return 1;
}

/* dtls1_do_handshake_write writes handshake message |in| using the given epoch,
* starting |offset| bytes into the message body. It returns one on success. On
* error, it returns <= 0 and sets |*out_offset| to the number of bytes of body
* that were successfully written. This may be used to retry the write
* later. |in| must be a reassembled handshake message with the full DTLS
* handshake header. */
static int dtls1_do_handshake_write(SSL *ssl, size_t *out_offset,
const uint8_t *in, size_t offset,
size_t len,
enum dtls1_use_epoch_t use_epoch) {
dtls1_update_mtu(ssl);

int ret = -1;
CBB cbb;
CBB_zero(&cbb);
/* Allocate a temporary buffer to hold the message fragments to avoid
* clobbering the message. */
uint8_t *buf = OPENSSL_malloc(ssl->d1->mtu);
if (buf == NULL) {
goto err;
/* Cross-epoch records are discarded, but we may receive out-of-order
* application data between ChangeCipherSpec and Finished or a ChangeCipherSpec
* before the appropriate point in the handshake. Those must be silently
* discarded.
*
* However, only allow the out-of-order records in the correct epoch.
* Application data must come in the encrypted epoch, and ChangeCipherSpec in
* the unencrypted epoch (we never renegotiate). Other cases fall through and
* fail with a fatal error. */
if ((rr->type == SSL3_RT_APPLICATION_DATA &&
ssl->s3->aead_read_ctx != NULL) ||
(rr->type == SSL3_RT_CHANGE_CIPHER_SPEC &&
ssl->s3->aead_read_ctx == NULL)) {
rr->length = 0;
goto start;
}

/* Although it may be sent as multiple fragments, a DTLS message must be sent
* serialized as a single fragment for purposes of |ssl_do_msg_callback| and
* the handshake hash. */
CBS cbs, body;
struct hm_header_st hdr;
CBS_init(&cbs, in, len);
if (!dtls1_parse_fragment(&cbs, &hdr, &body) ||
hdr.frag_off != 0 ||
hdr.frag_len != CBS_len(&body) ||
hdr.msg_len != CBS_len(&body) ||
!CBS_skip(&body, offset) ||
CBS_len(&cbs) != 0) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
goto err;
if (rr->type != SSL3_RT_HANDSHAKE) {
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
return -1;
}

do {
/* During the handshake, wbio is buffered to pack messages together. Flush
* the buffer if there isn't enough room to make progress. */
if (dtls1_max_record_size(ssl) < DTLS1_HM_HEADER_LENGTH + 1) {
int flush_ret = BIO_flush(ssl->wbio);
if (flush_ret <= 0) {
ssl->rwstate = SSL_WRITING;
ret = flush_ret;
goto err;
}
assert(BIO_wpending(ssl->wbio) == 0);
}
CBS cbs;
CBS_init(&cbs, rr->data, rr->length);

size_t todo = dtls1_max_record_size(ssl);
if (todo < DTLS1_HM_HEADER_LENGTH + 1) {
/* To make forward progress, the MTU must, at minimum, fit the handshake
* header and one byte of handshake body. */
OPENSSL_PUT_ERROR(SSL, SSL_R_MTU_TOO_SMALL);
goto err;
while (CBS_len(&cbs) > 0) {
/* Read a handshake fragment. */
struct hm_header_st msg_hdr;
CBS body;
if (!dtls1_parse_fragment(&cbs, &msg_hdr, &body)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_HANDSHAKE_RECORD);
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
return -1;
}
todo -= DTLS1_HM_HEADER_LENGTH;

if (todo > CBS_len(&body)) {
todo = CBS_len(&body);
}
if (todo >= (1u << 24)) {
todo = (1u << 24) - 1;
const size_t frag_off = msg_hdr.frag_off;
const size_t frag_len = msg_hdr.frag_len;
const size_t msg_len = msg_hdr.msg_len;
if (frag_off > msg_len || frag_off + frag_len < frag_off ||
frag_off + frag_len > msg_len ||
msg_len > ssl_max_handshake_message_len(ssl)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_EXCESSIVE_MESSAGE_SIZE);
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
return -1;
}

size_t buf_len;
if (!CBB_init_fixed(&cbb, buf, ssl->d1->mtu) ||
!CBB_add_u8(&cbb, hdr.type) ||
!CBB_add_u24(&cbb, hdr.msg_len) ||
!CBB_add_u16(&cbb, hdr.seq) ||
!CBB_add_u24(&cbb, offset) ||
!CBB_add_u24(&cbb, todo) ||
!CBB_add_bytes(&cbb, CBS_data(&body), todo) ||
!CBB_finish(&cbb, NULL, &buf_len)) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
goto err;
if (msg_hdr.seq < ssl->d1->handshake_read_seq ||
msg_hdr.seq >
(unsigned)ssl->d1->handshake_read_seq + SSL_MAX_HANDSHAKE_FLIGHT) {
/* Ignore fragments from the past, or ones too far in the future. */
continue;
}

int write_ret =
dtls1_write_record(ssl, SSL3_RT_HANDSHAKE, buf, buf_len, use_epoch);
if (write_ret <= 0) {
ret = write_ret;
goto err;
hm_fragment *frag = dtls1_get_incoming_message(ssl, &msg_hdr);
if (frag == NULL) {
return -1;
}
assert(frag->msg_header.msg_len == msg_len);

if (!CBS_skip(&body, todo)) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
goto err;
if (frag->reassembly == NULL) {
/* The message is already assembled. */
continue;
}
offset += todo;
} while (CBS_len(&body) != 0);

ssl_do_msg_callback(ssl, 1 /* write */, ssl->version, SSL3_RT_HANDSHAKE, in,
len);

ret = 1;

err:
*out_offset = offset;
CBB_cleanup(&cbb);
OPENSSL_free(buf);
return ret;
}
assert(msg_len > 0);

void dtls_clear_outgoing_messages(SSL *ssl) {
size_t i;
for (i = 0; i < ssl->d1->outgoing_messages_len; i++) {
OPENSSL_free(ssl->d1->outgoing_messages[i].data);
ssl->d1->outgoing_messages[i].data = NULL;
/* Copy the body into the fragment. */
memcpy(frag->fragment + frag_off, CBS_data(&body), CBS_len(&body));
dtls1_hm_fragment_mark(frag, frag_off, frag_off + frag_len);
}
ssl->d1->outgoing_messages_len = 0;
}

/* dtls1_add_change_cipher_spec adds a ChangeCipherSpec to the current
* handshake flight. */
static int dtls1_add_change_cipher_spec(SSL *ssl) {
if (ssl->d1->outgoing_messages_len >= SSL_MAX_HANDSHAKE_FLIGHT) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return 0;
}

DTLS_OUTGOING_MESSAGE *msg =
&ssl->d1->outgoing_messages[ssl->d1->outgoing_messages_len];
msg->data = NULL;
msg->len = 0;
msg->epoch = ssl->d1->w_epoch;
msg->is_ccs = 1;

ssl->d1->outgoing_messages_len++;
return 1;
}

static int dtls1_add_message(SSL *ssl, uint8_t *data, size_t len) {
if (ssl->d1->outgoing_messages_len >= SSL_MAX_HANDSHAKE_FLIGHT) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
OPENSSL_free(data);
return 0;
}

DTLS_OUTGOING_MESSAGE *msg =
&ssl->d1->outgoing_messages[ssl->d1->outgoing_messages_len];
msg->data = data;
msg->len = len;
msg->epoch = ssl->d1->w_epoch;
msg->is_ccs = 0;

ssl->d1->outgoing_messages_len++;
return 1;
}

int dtls1_init_message(SSL *ssl, CBB *cbb, CBB *body, uint8_t type) {
/* Pick a modest size hint to save most of the |realloc| calls. */
if (!CBB_init(cbb, 64) ||
!CBB_add_u8(cbb, type) ||
!CBB_add_u24(cbb, 0 /* length (filled in later) */) ||
!CBB_add_u16(cbb, ssl->d1->handshake_write_seq) ||
!CBB_add_u24(cbb, 0 /* offset */) ||
!CBB_add_u24_length_prefixed(cbb, body)) {
return 0;
}

return 1;
}

int dtls1_finish_message(SSL *ssl, CBB *cbb) {
uint8_t *msg = NULL;
size_t len;
if (!CBB_finish(cbb, &msg, &len) ||
len > 0xffffffffu ||
len < DTLS1_HM_HEADER_LENGTH) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
OPENSSL_free(msg);
return 0;
}

/* Fix up the header. Copy the fragment length into the total message
* length. */
memcpy(msg + 1, msg + DTLS1_HM_HEADER_LENGTH - 3, 3);

ssl3_update_handshake_hash(ssl, msg, len);

ssl->d1->handshake_write_seq++;
ssl->init_off = 0;
return dtls1_add_message(ssl, msg, len);
}

int dtls1_write_message(SSL *ssl) {
if (ssl->d1->outgoing_messages_len == 0) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return -1;
}

const DTLS_OUTGOING_MESSAGE *msg =
&ssl->d1->outgoing_messages[ssl->d1->outgoing_messages_len - 1];
if (msg->is_ccs) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return -1;
}

size_t offset = ssl->init_off;
int ret = dtls1_do_handshake_write(ssl, &offset, msg->data, offset, msg->len,
dtls1_use_current_epoch);
ssl->init_off = offset;
return ret;
}

/* dtls1_is_next_message_complete returns one if the next handshake message is
* complete and zero otherwise. */
static int dtls1_is_next_message_complete(SSL *ssl) {
hm_fragment *frag = ssl->d1->incoming_messages[ssl->d1->handshake_read_seq %
SSL_MAX_HANDSHAKE_FLIGHT];
return frag != NULL && frag->reassembly == NULL;
}

/* dtls1_get_incoming_message returns the incoming message corresponding to
* |msg_hdr|. If none exists, it creates a new one and inserts it in the
* queue. Otherwise, it checks |msg_hdr| is consistent with the existing one. It
* returns NULL on failure. The caller does not take ownership of the result. */
static hm_fragment *dtls1_get_incoming_message(
SSL *ssl, const struct hm_header_st *msg_hdr) {
if (msg_hdr->seq < ssl->d1->handshake_read_seq ||
msg_hdr->seq - ssl->d1->handshake_read_seq >= SSL_MAX_HANDSHAKE_FLIGHT) {
return NULL;
}

size_t idx = msg_hdr->seq % SSL_MAX_HANDSHAKE_FLIGHT;
hm_fragment *frag = ssl->d1->incoming_messages[idx];
if (frag != NULL) {
assert(frag->msg_header.seq == msg_hdr->seq);
/* The new fragment must be compatible with the previous fragments from this
* message. */
if (frag->msg_header.type != msg_hdr->type ||
frag->msg_header.msg_len != msg_hdr->msg_len) {
OPENSSL_PUT_ERROR(SSL, SSL_R_FRAGMENT_MISMATCH);
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
return NULL;
}
return frag;
}

/* This is the first fragment from this message. */
frag = dtls1_hm_fragment_new(msg_hdr->msg_len);
if (frag == NULL) {
return NULL;
}
memcpy(&frag->msg_header, msg_hdr, sizeof(*msg_hdr));
ssl->d1->incoming_messages[idx] = frag;
return frag;
}

/* dtls1_process_handshake_record reads a handshake record and processes it. It
* returns one if the record was successfully processed and 0 or -1 on error. */
static int dtls1_process_handshake_record(SSL *ssl) {
SSL3_RECORD *rr = &ssl->s3->rrec;

start:
if (rr->length == 0) {
int ret = dtls1_get_record(ssl);
if (ret <= 0) {
return ret;
}
}

/* Cross-epoch records are discarded, but we may receive out-of-order
* application data between ChangeCipherSpec and Finished or a ChangeCipherSpec
* before the appropriate point in the handshake. Those must be silently
* discarded.
*
* However, only allow the out-of-order records in the correct epoch.
* Application data must come in the encrypted epoch, and ChangeCipherSpec in
* the unencrypted epoch (we never renegotiate). Other cases fall through and
* fail with a fatal error. */
if ((rr->type == SSL3_RT_APPLICATION_DATA &&
ssl->s3->aead_read_ctx != NULL) ||
(rr->type == SSL3_RT_CHANGE_CIPHER_SPEC &&
ssl->s3->aead_read_ctx == NULL)) {
rr->length = 0;
goto start;
}

if (rr->type != SSL3_RT_HANDSHAKE) {
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_UNEXPECTED_MESSAGE);
OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
return -1;
}

CBS cbs;
CBS_init(&cbs, rr->data, rr->length);

while (CBS_len(&cbs) > 0) {
/* Read a handshake fragment. */
struct hm_header_st msg_hdr;
CBS body;
if (!dtls1_parse_fragment(&cbs, &msg_hdr, &body)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_HANDSHAKE_RECORD);
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
return -1;
}

const size_t frag_off = msg_hdr.frag_off;
const size_t frag_len = msg_hdr.frag_len;
const size_t msg_len = msg_hdr.msg_len;
if (frag_off > msg_len || frag_off + frag_len < frag_off ||
frag_off + frag_len > msg_len ||
msg_len > ssl_max_handshake_message_len(ssl)) {
OPENSSL_PUT_ERROR(SSL, SSL_R_EXCESSIVE_MESSAGE_SIZE);
ssl3_send_alert(ssl, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
return -1;
}

if (msg_hdr.seq < ssl->d1->handshake_read_seq ||
msg_hdr.seq >
(unsigned)ssl->d1->handshake_read_seq + SSL_MAX_HANDSHAKE_FLIGHT) {
/* Ignore fragments from the past, or ones too far in the future. */
continue;
}

hm_fragment *frag = dtls1_get_incoming_message(ssl, &msg_hdr);
if (frag == NULL) {
return -1;
}
assert(frag->msg_header.msg_len == msg_len);

if (frag->reassembly == NULL) {
/* The message is already assembled. */
continue;
}
assert(msg_len > 0);

/* Copy the body into the fragment. */
memcpy(frag->fragment + frag_off, CBS_data(&body), CBS_len(&body));
dtls1_hm_fragment_mark(frag, frag_off, frag_off + frag_len);
}

rr->length = 0;
ssl_read_buffer_discard(ssl);
return 1;

rr->length = 0;
ssl_read_buffer_discard(ssl);
return 1;
}

/* dtls1_get_message reads a handshake message of message type |msg_type| (any
@@ -744,25 +473,326 @@ err:
return -1;
}

static int dtls1_retransmit_message(SSL *ssl,
const DTLS_OUTGOING_MESSAGE *msg) {
/* DTLS renegotiation is unsupported, so only epochs 0 (NULL cipher) and 1
* (negotiated cipher) exist. */
assert(ssl->d1->w_epoch == 0 || ssl->d1->w_epoch == 1);
assert(msg->epoch <= ssl->d1->w_epoch);
enum dtls1_use_epoch_t use_epoch = dtls1_use_current_epoch;
if (ssl->d1->w_epoch == 1 && msg->epoch == 0) {
use_epoch = dtls1_use_previous_epoch;
void dtls_clear_incoming_messages(SSL *ssl) {
size_t i;
for (i = 0; i < SSL_MAX_HANDSHAKE_FLIGHT; i++) {
dtls1_hm_fragment_free(ssl->d1->incoming_messages[i]);
ssl->d1->incoming_messages[i] = NULL;
}
}

/* TODO(davidben): This cannot handle non-blocking writes. */
int ret;
if (msg->is_ccs) {
ret = dtls1_write_change_cipher_spec(ssl, use_epoch);
} else {
size_t offset = 0;
ret = dtls1_do_handshake_write(ssl, &offset, msg->data, offset, msg->len,
use_epoch);
int dtls1_parse_fragment(CBS *cbs, struct hm_header_st *out_hdr,
CBS *out_body) {
memset(out_hdr, 0x00, sizeof(struct hm_header_st));

if (!CBS_get_u8(cbs, &out_hdr->type) ||
!CBS_get_u24(cbs, &out_hdr->msg_len) ||
!CBS_get_u16(cbs, &out_hdr->seq) ||
!CBS_get_u24(cbs, &out_hdr->frag_off) ||
!CBS_get_u24(cbs, &out_hdr->frag_len) ||
!CBS_get_bytes(cbs, out_body, out_hdr->frag_len)) {
return 0;
}

return 1;
}


/* Sending handshake messages. */

static void dtls1_update_mtu(SSL *ssl) {
/* TODO(davidben): What is this code doing and do we need it? */
if (ssl->d1->mtu < dtls1_min_mtu() &&
!(SSL_get_options(ssl) & SSL_OP_NO_QUERY_MTU)) {
long mtu = BIO_ctrl(ssl->wbio, BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
if (mtu >= 0 && mtu <= (1 << 30) && (unsigned)mtu >= dtls1_min_mtu()) {
ssl->d1->mtu = (unsigned)mtu;
} else {
ssl->d1->mtu = kDefaultMTU;
BIO_ctrl(ssl->wbio, BIO_CTRL_DGRAM_SET_MTU, ssl->d1->mtu, NULL);
}
}

/* The MTU should be above the minimum now. */
assert(ssl->d1->mtu >= dtls1_min_mtu());
}

/* dtls1_max_record_size returns the maximum record body length that may be
* written without exceeding the MTU. It accounts for any buffering installed on
* the write BIO. If no record may be written, it returns zero. */
static size_t dtls1_max_record_size(SSL *ssl) {
size_t ret = ssl->d1->mtu;

size_t overhead = ssl_max_seal_overhead(ssl);
if (ret <= overhead) {
return 0;
}
ret -= overhead;

size_t pending = BIO_wpending(ssl->wbio);
if (ret <= pending) {
return 0;
}
ret -= pending;

return ret;
}

static int dtls1_write_change_cipher_spec(SSL *ssl,
enum dtls1_use_epoch_t use_epoch) {
dtls1_update_mtu(ssl);

/* During the handshake, wbio is buffered to pack messages together. Flush the
* buffer if the ChangeCipherSpec would not fit in a packet. */
if (dtls1_max_record_size(ssl) == 0) {
int ret = BIO_flush(ssl->wbio);
if (ret <= 0) {
ssl->rwstate = SSL_WRITING;
return ret;
}
}

static const uint8_t kChangeCipherSpec[1] = {SSL3_MT_CCS};
int ret =
dtls1_write_record(ssl, SSL3_RT_CHANGE_CIPHER_SPEC, kChangeCipherSpec,
sizeof(kChangeCipherSpec), use_epoch);
if (ret <= 0) {
return ret;
}

ssl_do_msg_callback(ssl, 1 /* write */, ssl->version,
SSL3_RT_CHANGE_CIPHER_SPEC, kChangeCipherSpec,
sizeof(kChangeCipherSpec));
return 1;
}

/* dtls1_do_handshake_write writes handshake message |in| using the given epoch,
* starting |offset| bytes into the message body. It returns one on success. On
* error, it returns <= 0 and sets |*out_offset| to the number of bytes of body
* that were successfully written. This may be used to retry the write
* later. |in| must be a reassembled handshake message with the full DTLS
* handshake header. */
static int dtls1_do_handshake_write(SSL *ssl, size_t *out_offset,
const uint8_t *in, size_t offset,
size_t len,
enum dtls1_use_epoch_t use_epoch) {
dtls1_update_mtu(ssl);

int ret = -1;
CBB cbb;
CBB_zero(&cbb);
/* Allocate a temporary buffer to hold the message fragments to avoid
* clobbering the message. */
uint8_t *buf = OPENSSL_malloc(ssl->d1->mtu);
if (buf == NULL) {
goto err;
}

/* Although it may be sent as multiple fragments, a DTLS message must be sent
* serialized as a single fragment for purposes of |ssl_do_msg_callback| and
* the handshake hash. */
CBS cbs, body;
struct hm_header_st hdr;
CBS_init(&cbs, in, len);
if (!dtls1_parse_fragment(&cbs, &hdr, &body) ||
hdr.frag_off != 0 ||
hdr.frag_len != CBS_len(&body) ||
hdr.msg_len != CBS_len(&body) ||
!CBS_skip(&body, offset) ||
CBS_len(&cbs) != 0) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
goto err;
}

do {
/* During the handshake, wbio is buffered to pack messages together. Flush
* the buffer if there isn't enough room to make progress. */
if (dtls1_max_record_size(ssl) < DTLS1_HM_HEADER_LENGTH + 1) {
int flush_ret = BIO_flush(ssl->wbio);
if (flush_ret <= 0) {
ssl->rwstate = SSL_WRITING;
ret = flush_ret;
goto err;
}
assert(BIO_wpending(ssl->wbio) == 0);
}

size_t todo = dtls1_max_record_size(ssl);
if (todo < DTLS1_HM_HEADER_LENGTH + 1) {
/* To make forward progress, the MTU must, at minimum, fit the handshake
* header and one byte of handshake body. */
OPENSSL_PUT_ERROR(SSL, SSL_R_MTU_TOO_SMALL);
goto err;
}
todo -= DTLS1_HM_HEADER_LENGTH;

if (todo > CBS_len(&body)) {
todo = CBS_len(&body);
}
if (todo >= (1u << 24)) {
todo = (1u << 24) - 1;
}

size_t buf_len;
if (!CBB_init_fixed(&cbb, buf, ssl->d1->mtu) ||
!CBB_add_u8(&cbb, hdr.type) ||
!CBB_add_u24(&cbb, hdr.msg_len) ||
!CBB_add_u16(&cbb, hdr.seq) ||
!CBB_add_u24(&cbb, offset) ||
!CBB_add_u24(&cbb, todo) ||
!CBB_add_bytes(&cbb, CBS_data(&body), todo) ||
!CBB_finish(&cbb, NULL, &buf_len)) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
goto err;
}

int write_ret =
dtls1_write_record(ssl, SSL3_RT_HANDSHAKE, buf, buf_len, use_epoch);
if (write_ret <= 0) {
ret = write_ret;
goto err;
}

if (!CBS_skip(&body, todo)) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
goto err;
}
offset += todo;
} while (CBS_len(&body) != 0);

ssl_do_msg_callback(ssl, 1 /* write */, ssl->version, SSL3_RT_HANDSHAKE, in,
len);

ret = 1;

err:
*out_offset = offset;
CBB_cleanup(&cbb);
OPENSSL_free(buf);
return ret;
}

void dtls_clear_outgoing_messages(SSL *ssl) {
size_t i;
for (i = 0; i < ssl->d1->outgoing_messages_len; i++) {
OPENSSL_free(ssl->d1->outgoing_messages[i].data);
ssl->d1->outgoing_messages[i].data = NULL;
}
ssl->d1->outgoing_messages_len = 0;
}

/* dtls1_add_change_cipher_spec adds a ChangeCipherSpec to the current
* handshake flight. */
static int dtls1_add_change_cipher_spec(SSL *ssl) {
if (ssl->d1->outgoing_messages_len >= SSL_MAX_HANDSHAKE_FLIGHT) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return 0;
}

DTLS_OUTGOING_MESSAGE *msg =
&ssl->d1->outgoing_messages[ssl->d1->outgoing_messages_len];
msg->data = NULL;
msg->len = 0;
msg->epoch = ssl->d1->w_epoch;
msg->is_ccs = 1;

ssl->d1->outgoing_messages_len++;
return 1;
}

static int dtls1_add_message(SSL *ssl, uint8_t *data, size_t len) {
if (ssl->d1->outgoing_messages_len >= SSL_MAX_HANDSHAKE_FLIGHT) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
OPENSSL_free(data);
return 0;
}

DTLS_OUTGOING_MESSAGE *msg =
&ssl->d1->outgoing_messages[ssl->d1->outgoing_messages_len];
msg->data = data;
msg->len = len;
msg->epoch = ssl->d1->w_epoch;
msg->is_ccs = 0;

ssl->d1->outgoing_messages_len++;
return 1;
}

int dtls1_init_message(SSL *ssl, CBB *cbb, CBB *body, uint8_t type) {
/* Pick a modest size hint to save most of the |realloc| calls. */
if (!CBB_init(cbb, 64) ||
!CBB_add_u8(cbb, type) ||
!CBB_add_u24(cbb, 0 /* length (filled in later) */) ||
!CBB_add_u16(cbb, ssl->d1->handshake_write_seq) ||
!CBB_add_u24(cbb, 0 /* offset */) ||
!CBB_add_u24_length_prefixed(cbb, body)) {
return 0;
}

return 1;
}

int dtls1_finish_message(SSL *ssl, CBB *cbb) {
uint8_t *msg = NULL;
size_t len;
if (!CBB_finish(cbb, &msg, &len) ||
len > 0xffffffffu ||
len < DTLS1_HM_HEADER_LENGTH) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
OPENSSL_free(msg);
return 0;
}

/* Fix up the header. Copy the fragment length into the total message
* length. */
memcpy(msg + 1, msg + DTLS1_HM_HEADER_LENGTH - 3, 3);

ssl3_update_handshake_hash(ssl, msg, len);

ssl->d1->handshake_write_seq++;
ssl->init_off = 0;
return dtls1_add_message(ssl, msg, len);
}

int dtls1_write_message(SSL *ssl) {
if (ssl->d1->outgoing_messages_len == 0) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return -1;
}

const DTLS_OUTGOING_MESSAGE *msg =
&ssl->d1->outgoing_messages[ssl->d1->outgoing_messages_len - 1];
if (msg->is_ccs) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return -1;
}

size_t offset = ssl->init_off;
int ret = dtls1_do_handshake_write(ssl, &offset, msg->data, offset, msg->len,
dtls1_use_current_epoch);
ssl->init_off = offset;
return ret;
}

static int dtls1_retransmit_message(SSL *ssl,
const DTLS_OUTGOING_MESSAGE *msg) {
/* DTLS renegotiation is unsupported, so only epochs 0 (NULL cipher) and 1
* (negotiated cipher) exist. */
assert(ssl->d1->w_epoch == 0 || ssl->d1->w_epoch == 1);
assert(msg->epoch <= ssl->d1->w_epoch);
enum dtls1_use_epoch_t use_epoch = dtls1_use_current_epoch;
if (ssl->d1->w_epoch == 1 && msg->epoch == 0) {
use_epoch = dtls1_use_previous_epoch;
}

/* TODO(davidben): This cannot handle non-blocking writes. */
int ret;
if (msg->is_ccs) {
ret = dtls1_write_change_cipher_spec(ssl, use_epoch);
} else {
size_t offset = 0;
ret = dtls1_do_handshake_write(ssl, &offset, msg->data, offset, msg->len,
use_epoch);
}

return ret;
@@ -807,30 +837,6 @@ int dtls1_send_change_cipher_spec(SSL *ssl, int a, int b) {
return dtls1_write_change_cipher_spec(ssl, dtls1_use_current_epoch);
}

void dtls_clear_incoming_messages(SSL *ssl) {
size_t i;
for (i = 0; i < SSL_MAX_HANDSHAKE_FLIGHT; i++) {
dtls1_hm_fragment_free(ssl->d1->incoming_messages[i]);
ssl->d1->incoming_messages[i] = NULL;
}
}

unsigned int dtls1_min_mtu(void) {
return kMinMTU;
}

int dtls1_parse_fragment(CBS *cbs, struct hm_header_st *out_hdr,
CBS *out_body) {
memset(out_hdr, 0x00, sizeof(struct hm_header_st));

if (!CBS_get_u8(cbs, &out_hdr->type) ||
!CBS_get_u24(cbs, &out_hdr->msg_len) ||
!CBS_get_u16(cbs, &out_hdr->seq) ||
!CBS_get_u24(cbs, &out_hdr->frag_off) ||
!CBS_get_u24(cbs, &out_hdr->frag_len) ||
!CBS_get_bytes(cbs, out_body, out_hdr->frag_len)) {
return 0;
}

return 1;
}

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