// Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <openssl/ssl.h>

#include <assert.h>

#include <string.h>

#include <algorithm>

#include <openssl/bio.h>

#include <openssl/bytestring.h>

#include <openssl/err.h>

#include <openssl/evp.h>

#include <openssl/mem.h>

#include <openssl/rand.h>

#include "../crypto/internal.h"

#include "internal.h"

BSSL_NAMESPACE_BEGIN

ssl_open_record_t dtls1_process_ack(SSL *ssl, uint8_t *out_alert,

                                    DTLSRecordNumber ack_record_number,

                                    Span<const uint8_t> data) {

  // As a DTLS-1.3-capable client, it is possible to receive an ACK before we

  // receive ServerHello and learned the server picked DTLS 1.3. Thus, tolerate

  // but ignore ACKs before the version is set.

  if (!ssl_has_final_version(ssl)) {

    return ssl_open_record_discard;

  }

  // ACKs are only allowed in DTLS 1.3. Reject them if we've negotiated a

  // version and it's not 1.3.

  if (ssl_protocol_version(ssl) < TLS1_3_VERSION) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);

    *out_alert = SSL_AD_UNEXPECTED_MESSAGE;

    return ssl_open_record_error;

  }

  CBS cbs = data, record_numbers;

  if (!CBS_get_u16_length_prefixed(&cbs, &record_numbers) ||

      CBS_len(&cbs) != 0) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);

    *out_alert = SSL_AD_DECODE_ERROR;

    return ssl_open_record_error;

  }

  while (CBS_len(&record_numbers) != 0) {

    uint64_t epoch, seq;

    if (!CBS_get_u64(&record_numbers, &epoch) ||

        !CBS_get_u64(&record_numbers, &seq)) {

      OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);

      *out_alert = SSL_AD_DECODE_ERROR;

      return ssl_open_record_error;

    }

    // During the handshake, records must be ACKed at the same or higher epoch.

    // See https://www.rfc-editor.org/errata/eid8108. Additionally, if the

    // record does not fit in DTLSRecordNumber, it is definitely not a record

    // number that we sent.

    if ((ack_record_number.epoch() < ssl_encryption_application &&

         epoch > ack_record_number.epoch()) ||

        epoch > UINT16_MAX || seq > DTLSRecordNumber::kMaxSequence) {

      OPENSSL_PUT_ERROR(SSL, SSL_R_DECODE_ERROR);

      *out_alert = SSL_AD_ILLEGAL_PARAMETER;

      return ssl_open_record_error;

    }

    // Find the sent record that matches this ACK.

    DTLSRecordNumber number(static_cast<uint16_t>(epoch), seq);

    DTLSSentRecord *sent_record = nullptr;

    if (ssl->d1->sent_records != nullptr) {

      for (size_t i = 0; i < ssl->d1->sent_records->size(); i++) {

        if ((*ssl->d1->sent_records)[i].number == number) {

          sent_record = &(*ssl->d1->sent_records)[i];

          break;

        }

      }

    }

    if (sent_record == nullptr) {

      // We may have sent this record and forgotten it, so this is not an error.

      continue;

    }

    // Mark each message as ACKed.

    if (sent_record->first_msg == sent_record->last_msg) {

      ssl->d1->outgoing_messages[sent_record->first_msg].acked.MarkRange(

          sent_record->first_msg_start, sent_record->last_msg_end);

    } else {

      ssl->d1->outgoing_messages[sent_record->first_msg].acked.MarkRange(

          sent_record->first_msg_start, SIZE_MAX);

      for (size_t i = size_t{sent_record->first_msg} + 1;

           i < sent_record->last_msg; i++) {

        ssl->d1->outgoing_messages[i].acked.MarkRange(0, SIZE_MAX);

      }

      if (sent_record->last_msg_end != 0) {

        ssl->d1->outgoing_messages[sent_record->last_msg].acked.MarkRange(

            0, sent_record->last_msg_end);

      }

    }

    // Clear the state so we don't bother re-marking the messages next time.

    sent_record->first_msg = 0;

    sent_record->first_msg_start = 0;

    sent_record->last_msg = 0;

    sent_record->last_msg_end = 0;

  }

  // If the outgoing flight is now fully ACKed, we are done retransmitting.

  if (std::all_of(ssl->d1->outgoing_messages.begin(),

                  ssl->d1->outgoing_messages.end(),

                  [](const auto &msg) { return msg.IsFullyAcked(); })) {

    dtls1_stop_timer(ssl);

    dtls_clear_outgoing_messages(ssl);

    // DTLS 1.3 defers the key update to when the message is ACKed.

    if (ssl->s3->key_update_pending) {

      if (!tls13_rotate_traffic_key(ssl, evp_aead_seal)) {

        return ssl_open_record_error;

      }

      ssl->s3->key_update_pending = false;

    }

    // Check for deferred messages.

    if (ssl->d1->queued_key_update != QueuedKeyUpdate::kNone) {

      int request_type =

          ssl->d1->queued_key_update == QueuedKeyUpdate::kUpdateRequested

              ? SSL_KEY_UPDATE_REQUESTED

              : SSL_KEY_UPDATE_NOT_REQUESTED;

      ssl->d1->queued_key_update = QueuedKeyUpdate::kNone;

      if (!tls13_add_key_update(ssl, request_type)) {

        return ssl_open_record_error;

      }

    }

  } else {

    // We may still be able to drop unused write epochs.

    dtls_clear_unused_write_epochs(ssl);

    // TODO(crbug.com/42290594): Schedule a retransmit. The peer will have

    // waited before sending the ACK, so a partial ACK suggests packet loss.

  }

  ssl_do_msg_callback(ssl, /*is_write=*/0, SSL3_RT_ACK, data);

  return ssl_open_record_discard;

}

ssl_open_record_t dtls1_open_app_data(SSL *ssl, Span<uint8_t> *out,

                                      size_t *out_consumed, uint8_t *out_alert,

                                      Span<uint8_t> in) {

  assert(!SSL_in_init(ssl));

  uint8_t type;

  DTLSRecordNumber record_number;

  Span<uint8_t> record;

  auto ret = dtls_open_record(ssl, &type, &record_number, &record, out_consumed,

                              out_alert, in);

  if (ret != ssl_open_record_success) {

    return ret;

  }

  if (type == SSL3_RT_HANDSHAKE) {

    // Process handshake fragments for DTLS 1.3 post-handshake messages.

    if (ssl_protocol_version(ssl) >= TLS1_3_VERSION) {

      if (!dtls1_process_handshake_fragments(ssl, out_alert, record_number,

                                             record)) {

        return ssl_open_record_error;

      }

      return ssl_open_record_discard;

    }

    // Parse the first fragment header to determine if this is a pre-CCS or

    // post-CCS handshake record. DTLS resets handshake message numbers on each

    // handshake, so renegotiations and retransmissions are ambiguous.

    //

    // TODO(crbug.com/42290594): Move this logic into

    // |dtls1_process_handshake_fragments| and integrate it into DTLS 1.3

    // retransmit conditions.

    CBS cbs, body;

    struct hm_header_st msg_hdr;

    CBS_init(&cbs, record.data(), record.size());

    if (!dtls1_parse_fragment(&cbs, &msg_hdr, &body)) {

      OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_HANDSHAKE_RECORD);

      *out_alert = SSL_AD_DECODE_ERROR;

      return ssl_open_record_error;

    }

    if (msg_hdr.type == SSL3_MT_FINISHED &&

        msg_hdr.seq == ssl->d1->handshake_read_seq - 1) {

      if (!ssl->d1->sending_flight && msg_hdr.frag_off == 0) {

        // Retransmit our last flight of messages. If the peer sends the second

        // Finished, they may not have received ours. Only do this for the

        // first fragment, in case the Finished was fragmented.

        //

        // This is not really a timeout, but increment the timeout count so we

        // eventually give up.

        ssl->d1->num_timeouts++;

        ssl->d1->sending_flight = true;

      }

      return ssl_open_record_discard;

    }

    // Otherwise, this is a pre-CCS handshake message from an unsupported

    // renegotiation attempt. Fall through to the error path.

  }

  if (type == SSL3_RT_ACK) {

    return dtls1_process_ack(ssl, out_alert, record_number, record);

  }

  if (type != SSL3_RT_APPLICATION_DATA) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);

    *out_alert = SSL_AD_UNEXPECTED_MESSAGE;

    return ssl_open_record_error;

  }

  if (record.empty()) {

    return ssl_open_record_discard;

  }

  *out = record;

  return ssl_open_record_success;

}

int dtls1_write_app_data(SSL *ssl, bool *out_needs_handshake,

                         size_t *out_bytes_written, Span<const uint8_t> in) {

  assert(!SSL_in_init(ssl));

  *out_needs_handshake = false;

  if (ssl->s3->write_shutdown != ssl_shutdown_none) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_PROTOCOL_IS_SHUTDOWN);

    return -1;

  }

  // DTLS does not split the input across records.

  if (in.size() > SSL3_RT_MAX_PLAIN_LENGTH) {

    OPENSSL_PUT_ERROR(SSL, SSL_R_DTLS_MESSAGE_TOO_BIG);

    return -1;

  }

  if (in.empty()) {

    *out_bytes_written = 0;

    return 1;

  }

  // TODO(crbug.com/381113363): Use the 0-RTT epoch if writing 0-RTT.

  int ret = dtls1_write_record(ssl, SSL3_RT_APPLICATION_DATA, in,

                               ssl->d1->write_epoch.epoch());

  if (ret <= 0) {

    return ret;

  }

  *out_bytes_written = in.size();

  return 1;

}

int dtls1_write_record(SSL *ssl, int type, Span<const uint8_t> in,

                       uint16_t epoch) {

  SSLBuffer *buf = &ssl->s3->write_buffer;

  assert(in.size() <= SSL3_RT_MAX_PLAIN_LENGTH);

  // There should never be a pending write buffer in DTLS. One can't write half

  // a datagram, so the write buffer is always dropped in

  // |ssl_write_buffer_flush|.

  assert(buf->empty());

  if (in.size() > SSL3_RT_MAX_PLAIN_LENGTH) {

    OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);

    return -1;

  }

  DTLSRecordNumber record_number;

  size_t ciphertext_len;

  if (!buf->EnsureCap(dtls_seal_prefix_len(ssl, epoch),

                      in.size() + SSL_max_seal_overhead(ssl)) ||

      !dtls_seal_record(ssl, &record_number, buf->remaining().data(),

                        &ciphertext_len, buf->remaining().size(), type,

                        in.data(), in.size(), epoch)) {

    buf->Clear();

    return -1;

  }

  buf->DidWrite(ciphertext_len);

  int ret = ssl_write_buffer_flush(ssl);

  if (ret <= 0) {

    return ret;

  }

  return 1;

}

int dtls1_dispatch_alert(SSL *ssl) {

  int ret = dtls1_write_record(ssl, SSL3_RT_ALERT, ssl->s3->send_alert,

                               ssl->d1->write_epoch.epoch());

  if (ret <= 0) {

    return ret;

  }

  ssl->s3->alert_dispatch = false;

  // If the alert is fatal, flush the BIO now.

  if (ssl->s3->send_alert[0] == SSL3_AL_FATAL) {

    BIO_flush(ssl->wbio.get());

  }

  ssl_do_msg_callback(ssl, 1 /* write */, SSL3_RT_ALERT, ssl->s3->send_alert);

  int alert = (ssl->s3->send_alert[0] << 8) | ssl->s3->send_alert[1];

  ssl_do_info_callback(ssl, SSL_CB_WRITE_ALERT, alert);

  return 1;

}

BSSL_NAMESPACE_END