/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 2020 - 2021, Jacob Hoffman-Andrews,
 * <github@hoffman-andrews.com>
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/
#include "curl_setup.h"

#ifdef USE_RUSTLS

#include "curl_printf.h"

#include <errno.h>
#include <crustls.h>

#include "inet_pton.h"
#include "urldata.h"
#include "sendf.h"
#include "vtls.h"
#include "select.h"
#include "strerror.h"
#include "multiif.h"

struct ssl_backend_data
{
  const struct rustls_client_config *config;
  struct rustls_connection *conn;
  bool data_pending;
};

/* For a given rustls_result error code, return the best-matching CURLcode. */
static CURLcode map_error(rustls_result r)
{
  if(rustls_result_is_cert_error(r)) {
    return CURLE_PEER_FAILED_VERIFICATION;
  }
  switch(r) {
    case RUSTLS_RESULT_OK:
      return CURLE_OK;
    case RUSTLS_RESULT_NULL_PARAMETER:
      return CURLE_BAD_FUNCTION_ARGUMENT;
    default:
      return CURLE_READ_ERROR;
  }
}

static bool
cr_data_pending(const struct connectdata *conn, int sockindex)
{
  const struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  struct ssl_backend_data *backend = connssl->backend;
  return backend->data_pending;
}

static CURLcode
cr_connect(struct Curl_easy *data UNUSED_PARAM,
                    struct connectdata *conn UNUSED_PARAM,
                    int sockindex UNUSED_PARAM)
{
  infof(data, "rustls_connect: unimplemented");
  return CURLE_SSL_CONNECT_ERROR;
}

static int
read_cb(void *userdata, uint8_t *buf, uintptr_t len, uintptr_t *out_n)
{
  ssize_t n = sread(*(int *)userdata, buf, len);
  if(n < 0) {
    return SOCKERRNO;
  }
  *out_n = n;
  return 0;
}

static int
write_cb(void *userdata, const uint8_t *buf, uintptr_t len, uintptr_t *out_n)
{
  ssize_t n = swrite(*(int *)userdata, buf, len);
  if(n < 0) {
    return SOCKERRNO;
  }
  *out_n = n;
  return 0;
}

/*
 * On each run:
 *  - Read a chunk of bytes from the socket into rustls' TLS input buffer.
 *  - Tell rustls to process any new packets.
 *  - Read out as many plaintext bytes from rustls as possible, until hitting
 *    error, EOF, or EAGAIN/EWOULDBLOCK, or plainbuf/plainlen is filled up.
 *
 * It's okay to call this function with plainbuf == NULL and plainlen == 0.
 * In that case, it will copy bytes from the socket into rustls' TLS input
 * buffer, and process packets, but won't consume bytes from rustls' plaintext
 * output buffer.
 */
static ssize_t
cr_recv(struct Curl_easy *data, int sockindex,
            char *plainbuf, size_t plainlen, CURLcode *err)
{
  struct connectdata *conn = data->conn;
  struct ssl_connect_data *const connssl = &conn->ssl[sockindex];
  struct ssl_backend_data *const backend = connssl->backend;
  struct rustls_connection *const rconn = backend->conn;
  size_t n = 0;
  size_t tls_bytes_read = 0;
  size_t plain_bytes_copied = 0;
  rustls_result rresult = 0;
  char errorbuf[255];
  rustls_io_result io_error;

  io_error = rustls_connection_read_tls(rconn, read_cb,
    &conn->sock[sockindex], &tls_bytes_read);
  if(io_error == EAGAIN || io_error == EWOULDBLOCK) {
    infof(data, "sread: EAGAIN or EWOULDBLOCK");
  }
  else if(io_error) {
    char buffer[STRERROR_LEN];
    failf(data, "reading from socket: %s",
          Curl_strerror(io_error, buffer, sizeof(buffer)));
    *err = CURLE_READ_ERROR;
    return -1;
  }
  else if(tls_bytes_read == 0) {
    failf(data, "connection closed without TLS close_notify alert");
    *err = CURLE_READ_ERROR;
    return -1;
  }

  infof(data, "cr_recv read %ld bytes from the network", tls_bytes_read);

  rresult = rustls_connection_process_new_packets(rconn);
  if(rresult != RUSTLS_RESULT_OK) {
    rustls_error(rresult, errorbuf, sizeof(errorbuf), &n);
    failf(data, "%.*s", n, errorbuf);
    *err = map_error(rresult);
    return -1;
  }

  backend->data_pending = TRUE;

  while(plain_bytes_copied < plainlen) {
    rresult = rustls_connection_read(rconn,
      (uint8_t *)plainbuf + plain_bytes_copied,
      plainlen - plain_bytes_copied,
      &n);
    if(rresult == RUSTLS_RESULT_ALERT_CLOSE_NOTIFY) {
      *err = CURLE_OK;
      return 0;
    }
    else if(rresult != RUSTLS_RESULT_OK) {
      failf(data, "error in rustls_connection_read");
      *err = CURLE_READ_ERROR;
      return -1;
    }
    else if(n == 0) {
      /* rustls returns 0 from connection_read to mean "all currently
        available data has been read." If we bring in more ciphertext with
        read_tls, more plaintext will become available. So don't tell curl
        this is an EOF. Instead, say "come back later." */
      infof(data, "cr_recv got 0 bytes of plaintext");
      backend->data_pending = FALSE;
      break;
    }
    else {
      infof(data, "cr_recv copied out %ld bytes of plaintext", n);
      plain_bytes_copied += n;
    }
  }

  /* If we wrote out 0 plaintext bytes, it might just mean we haven't yet
     read a full TLS record. Return CURLE_AGAIN so curl doesn't treat this
     as EOF. */
  if(plain_bytes_copied == 0) {
    *err = CURLE_AGAIN;
    return -1;
  }

  return plain_bytes_copied;
}

/*
 * On each call:
 *  - Copy `plainlen` bytes into rustls' plaintext input buffer (if > 0).
 *  - Fully drain rustls' plaintext output buffer into the socket until
 *    we get either an error or EAGAIN/EWOULDBLOCK.
 *
 * It's okay to call this function with plainbuf == NULL and plainlen == 0.
 * In that case, it won't read anything into rustls' plaintext input buffer.
 * It will only drain rustls' plaintext output buffer into the socket.
 */
static ssize_t
cr_send(struct Curl_easy *data, int sockindex,
        const void *plainbuf, size_t plainlen, CURLcode *err)
{
  struct connectdata *conn = data->conn;
  struct ssl_connect_data *const connssl = &conn->ssl[sockindex];
  struct ssl_backend_data *const backend = connssl->backend;
  struct rustls_connection *const rconn = backend->conn;
  size_t plainwritten = 0;
  size_t tlswritten = 0;
  size_t tlswritten_total = 0;
  rustls_result rresult;
  rustls_io_result io_error;

  infof(data, "cr_send %ld bytes of plaintext", plainlen);

  if(plainlen > 0) {
    rresult = rustls_connection_write(rconn, plainbuf, plainlen,
                                      &plainwritten);
    if(rresult != RUSTLS_RESULT_OK) {
      failf(data, "error in rustls_connection_write");
      *err = CURLE_WRITE_ERROR;
      return -1;
    }
    else if(plainwritten == 0) {
      failf(data, "EOF in rustls_connection_write");
      *err = CURLE_WRITE_ERROR;
      return -1;
    }
  }

  while(rustls_connection_wants_write(rconn)) {
    io_error = rustls_connection_write_tls(rconn, write_cb,
      &conn->sock[sockindex], &tlswritten);
    if(io_error == EAGAIN || io_error == EWOULDBLOCK) {
      infof(data, "swrite: EAGAIN after %ld bytes", tlswritten_total);
      *err = CURLE_AGAIN;
      return -1;
    }
    else if(io_error) {
      char buffer[STRERROR_LEN];
      failf(data, "writing to socket: %s",
            Curl_strerror(io_error, buffer, sizeof(buffer)));
      *err = CURLE_WRITE_ERROR;
      return -1;
    }
    if(tlswritten == 0) {
      failf(data, "EOF in swrite");
      *err = CURLE_WRITE_ERROR;
      return -1;
    }
    infof(data, "cr_send wrote %ld bytes to network", tlswritten);
    tlswritten_total += tlswritten;
  }

  return plainwritten;
}

/* A server certificate verify callback for rustls that always returns
   RUSTLS_RESULT_OK, or in other words disable certificate verification. */
static enum rustls_result
cr_verify_none(void *userdata UNUSED_PARAM,
               const rustls_verify_server_cert_params *params UNUSED_PARAM)
{
  return RUSTLS_RESULT_OK;
}

static bool
cr_hostname_is_ip(const char *hostname)
{
  struct in_addr in;
#ifdef ENABLE_IPV6
  struct in6_addr in6;
  if(Curl_inet_pton(AF_INET6, hostname, &in6) > 0) {
    return true;
  }
#endif /* ENABLE_IPV6 */
  if(Curl_inet_pton(AF_INET, hostname, &in) > 0) {
    return true;
  }
  return false;
}

static CURLcode
cr_init_backend(struct Curl_easy *data, struct connectdata *conn,
                struct ssl_backend_data *const backend)
{
  struct rustls_connection *rconn = backend->conn;
  struct rustls_client_config_builder *config_builder = NULL;
  const char *const ssl_cafile = SSL_CONN_CONFIG(CAfile);
  const bool verifypeer = SSL_CONN_CONFIG(verifypeer);
  const char *hostname = conn->host.name;
  char errorbuf[256];
  size_t errorlen;
  int result;
  rustls_slice_bytes alpn[2] = {
    { (const uint8_t *)ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH },
    { (const uint8_t *)ALPN_H2, ALPN_H2_LENGTH },
  };

  config_builder = rustls_client_config_builder_new();
#ifdef USE_HTTP2
  infof(data, "offering ALPN for HTTP/1.1 and HTTP/2");
  rustls_client_config_builder_set_protocols(config_builder, alpn, 2);
#else
  infof(data, "offering ALPN for HTTP/1.1 only");
  rustls_client_config_builder_set_protocols(config_builder, alpn, 1);
#endif
  if(!verifypeer) {
    rustls_client_config_builder_dangerous_set_certificate_verifier(
      config_builder, cr_verify_none);
    /* rustls doesn't support IP addresses (as of 0.19.0), and will reject
     * connections created with an IP address, even when certificate
     * verification is turned off. Set a placeholder hostname and disable
     * SNI. */
    if(cr_hostname_is_ip(hostname)) {
      rustls_client_config_builder_set_enable_sni(config_builder, false);
      hostname = "example.invalid";
    }
  }
  else if(ssl_cafile) {
    result = rustls_client_config_builder_load_roots_from_file(
      config_builder, ssl_cafile);
    if(result != RUSTLS_RESULT_OK) {
      failf(data, "failed to load trusted certificates");
      rustls_client_config_free(
        rustls_client_config_builder_build(config_builder));
      return CURLE_SSL_CACERT_BADFILE;
    }
  }

  backend->config = rustls_client_config_builder_build(config_builder);
  DEBUGASSERT(rconn == NULL);
  result = rustls_client_connection_new(backend->config, hostname, &rconn);
  if(result != RUSTLS_RESULT_OK) {
    rustls_error(result, errorbuf, sizeof(errorbuf), &errorlen);
    failf(data, "rustls_client_connection_new: %.*s", errorlen, errorbuf);
    return CURLE_COULDNT_CONNECT;
  }
  rustls_connection_set_userdata(rconn, backend);
  backend->conn = rconn;
  return CURLE_OK;
}

static void
cr_set_negotiated_alpn(struct Curl_easy *data, struct connectdata *conn,
  const struct rustls_connection *rconn)
{
  const uint8_t *protocol = NULL;
  size_t len = 0;

  rustls_connection_get_alpn_protocol(rconn, &protocol, &len);
  if(NULL == protocol) {
    infof(data, "ALPN, server did not agree to a protocol");
    return;
  }

#ifdef USE_HTTP2
  if(len == ALPN_H2_LENGTH && 0 == memcmp(ALPN_H2, protocol, len)) {
    infof(data, "ALPN, negotiated h2");
    conn->negnpn = CURL_HTTP_VERSION_2;
  }
  else
#endif
  if(len == ALPN_HTTP_1_1_LENGTH &&
      0 == memcmp(ALPN_HTTP_1_1, protocol, len)) {
    infof(data, "ALPN, negotiated http/1.1");
    conn->negnpn = CURL_HTTP_VERSION_1_1;
  }
  else {
    infof(data, "ALPN, negotiated an unrecognized protocol");
  }

  Curl_multiuse_state(data, conn->negnpn == CURL_HTTP_VERSION_2 ?
                      BUNDLE_MULTIPLEX : BUNDLE_NO_MULTIUSE);
}

static CURLcode
cr_connect_nonblocking(struct Curl_easy *data, struct connectdata *conn,
                       int sockindex, bool *done)
{
  struct ssl_connect_data *const connssl = &conn->ssl[sockindex];
  curl_socket_t sockfd = conn->sock[sockindex];
  struct ssl_backend_data *const backend = connssl->backend;
  struct rustls_connection *rconn = NULL;
  CURLcode tmperr = CURLE_OK;
  int result;
  int what;
  bool wants_read;
  bool wants_write;
  curl_socket_t writefd;
  curl_socket_t readfd;

  if(ssl_connection_none == connssl->state) {
    result = cr_init_backend(data, conn, connssl->backend);
    if(result != CURLE_OK) {
      return result;
    }
    connssl->state = ssl_connection_negotiating;
  }

  rconn = backend->conn;

  /* Read/write data until the handshake is done or the socket would block. */
  for(;;) {
    /*
    * Connection has been established according to rustls. Set send/recv
    * handlers, and update the state machine.
    * This check has to come last because is_handshaking starts out false,
    * then becomes true when we first write data, then becomes false again
    * once the handshake is done.
    */
    if(!rustls_connection_is_handshaking(rconn)) {
      infof(data, "Done handshaking");
      /* Done with the handshake. Set up callbacks to send/receive data. */
      connssl->state = ssl_connection_complete;

      cr_set_negotiated_alpn(data, conn, rconn);

      conn->recv[sockindex] = cr_recv;
      conn->send[sockindex] = cr_send;
      *done = TRUE;
      return CURLE_OK;
    }

    wants_read = rustls_connection_wants_read(rconn);
    wants_write = rustls_connection_wants_write(rconn);
    DEBUGASSERT(wants_read || wants_write);
    writefd = wants_write?sockfd:CURL_SOCKET_BAD;
    readfd = wants_read?sockfd:CURL_SOCKET_BAD;

    what = Curl_socket_check(readfd, CURL_SOCKET_BAD, writefd, 0);
    if(what < 0) {
      /* fatal error */
      failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
      return CURLE_SSL_CONNECT_ERROR;
    }
    if(0 == what) {
      infof(data, "Curl_socket_check: %s would block",
            wants_read&&wants_write ? "writing and reading" :
            wants_write ? "writing" : "reading");
      *done = FALSE;
      return CURLE_OK;
    }
    /* socket is readable or writable */

    if(wants_write) {
      infof(data, "rustls_connection wants us to write_tls.");
      cr_send(data, sockindex, NULL, 0, &tmperr);
      if(tmperr == CURLE_AGAIN) {
        infof(data, "writing would block");
        /* fall through */
      }
      else if(tmperr != CURLE_OK) {
        return tmperr;
      }
    }

    if(wants_read) {
      infof(data, "rustls_connection wants us to read_tls.");

      cr_recv(data, sockindex, NULL, 0, &tmperr);
      if(tmperr == CURLE_AGAIN) {
        infof(data, "reading would block");
        /* fall through */
      }
      else if(tmperr != CURLE_OK) {
        if(tmperr == CURLE_READ_ERROR) {
          return CURLE_SSL_CONNECT_ERROR;
        }
        else {
          return tmperr;
        }
      }
    }
  }

  /* We should never fall through the loop. We should return either because
     the handshake is done or because we can't read/write without blocking. */
  DEBUGASSERT(false);
}

/* returns a bitmap of flags for this connection's first socket indicating
   whether we want to read or write */
static int
cr_getsock(struct connectdata *conn, curl_socket_t *socks)
{
  struct ssl_connect_data *const connssl = &conn->ssl[FIRSTSOCKET];
  curl_socket_t sockfd = conn->sock[FIRSTSOCKET];
  struct ssl_backend_data *const backend = connssl->backend;
  struct rustls_connection *rconn = backend->conn;

  if(rustls_connection_wants_write(rconn)) {
    socks[0] = sockfd;
    return GETSOCK_WRITESOCK(0);
  }
  if(rustls_connection_wants_read(rconn)) {
    socks[0] = sockfd;
    return GETSOCK_READSOCK(0);
  }

  return GETSOCK_BLANK;
}

static void *
cr_get_internals(struct ssl_connect_data *connssl,
                 CURLINFO info UNUSED_PARAM)
{
  struct ssl_backend_data *backend = connssl->backend;
  return &backend->conn;
}

static void
cr_close(struct Curl_easy *data, struct connectdata *conn,
         int sockindex)
{
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  struct ssl_backend_data *backend = connssl->backend;
  CURLcode tmperr = CURLE_OK;
  ssize_t n = 0;

  if(backend->conn) {
    rustls_connection_send_close_notify(backend->conn);
    n = cr_send(data, sockindex, NULL, 0, &tmperr);
    if(n < 0) {
      failf(data, "error sending close notify: %d", tmperr);
    }

    rustls_connection_free(backend->conn);
    backend->conn = NULL;
  }
  if(backend->config) {
    rustls_client_config_free(backend->config);
    backend->config = NULL;
  }
}

const struct Curl_ssl Curl_ssl_rustls = {
  { CURLSSLBACKEND_RUSTLS, "rustls" },
  SSLSUPP_TLS13_CIPHERSUITES,      /* supports */
  sizeof(struct ssl_backend_data),

  Curl_none_init,                  /* init */
  Curl_none_cleanup,               /* cleanup */
  rustls_version,                  /* version */
  Curl_none_check_cxn,             /* check_cxn */
  Curl_none_shutdown,              /* shutdown */
  cr_data_pending,                 /* data_pending */
  Curl_none_random,                /* random */
  Curl_none_cert_status_request,   /* cert_status_request */
  cr_connect,                      /* connect */
  cr_connect_nonblocking,          /* connect_nonblocking */
  cr_getsock,                      /* cr_getsock */
  cr_get_internals,                /* get_internals */
  cr_close,                        /* close_one */
  Curl_none_close_all,             /* close_all */
  Curl_none_session_free,          /* session_free */
  Curl_none_set_engine,            /* set_engine */
  Curl_none_set_engine_default,    /* set_engine_default */
  Curl_none_engines_list,          /* engines_list */
  Curl_none_false_start,           /* false_start */
  NULL,                            /* sha256sum */
  NULL,                            /* associate_connection */
  NULL                             /* disassociate_connection */
};

#endif /* USE_RUSTLS */