text: /* Copyright (c) 2003, Roger Dingledine.
   * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   * Copyright (c) 2007-2017, The Tor Project, Inc. */
  /* See LICENSE for licensing information */
  
  /**
   * \file tortls.c
   * \brief Wrapper functions to present a consistent interface to
   * TLS, SSL, and X.509 functions from OpenSSL.
   **/
  
  /* (Unlike other tor functions, these
   * are prefixed with tor_ in order to avoid conflicting with OpenSSL
   * functions and variables.)
   */
  
  #include "orconfig.h"
  
  #define TORTLS_PRIVATE
  #define TORTLS_OPENSSL_PRIVATE
  
  #include <assert.h>
  #ifdef _WIN32 /*wrkard for dtls1.h >= 0.9.8m of "#include <winsock.h>"*/
    #include <winsock2.h>
    #include <ws2tcpip.h>
  #endif
  
  #include "compat.h"
  
  /* Some versions of OpenSSL declare SSL_get_selected_srtp_profile twice in
   * srtp.h. Suppress the GCC warning so we can build with -Wredundant-decl. */
  DISABLE_GCC_WARNING(redundant-decls)
  
  #include <openssl/opensslv.h>
  #include "crypto.h"
  
  #ifdef OPENSSL_NO_EC
  #error "We require OpenSSL with ECC support"
  #endif
  
  #include <openssl/ssl.h>
  #include <openssl/ssl3.h>
  #include <openssl/err.h>
  #include <openssl/tls1.h>
  #include <openssl/asn1.h>
  #include <openssl/bio.h>
  #include <openssl/bn.h>
  #include <openssl/rsa.h>
  
  ENABLE_GCC_WARNING(redundant-decls)
  
  #define TORTLS_PRIVATE
  #include "tortls.h"
  #include "util.h"
  #include "torlog.h"
  #include "container.h"
  #include <string.h>
  
  #define X509_get_notBefore_const(cert) \
    ((const ASN1_TIME*) X509_get_notBefore((X509 *)cert))
  #define X509_get_notAfter_const(cert) \
    ((const ASN1_TIME*) X509_get_notAfter((X509 *)cert))
  
  /* Copied from or.h */
  #define LEGAL_NICKNAME_CHARACTERS \
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
  
  /** How long do identity certificates live? (sec) */
  #define IDENTITY_CERT_LIFETIME  (365*24*60*60)
  
  #define ADDR(tls) (((tls) && (tls)->address) ? tls->address : "peer")
  
  #if OPENSSL_VERSION_NUMBER <  OPENSSL_V(1,0,0,'f')
  /* This is a version of OpenSSL before 1.0.0f. It does not have
   * the CVE-2011-4576 fix, and as such it can't use RELEASE_BUFFERS and
   * SSL3 safely at the same time.
   */
  #define DISABLE_SSL3_HANDSHAKE
  #endif
  
  /* We redefine these so that we can run correctly even if the vendor gives us
   * a version of OpenSSL that does not match its header files.  (Apple: I am
   * looking at you.)
   */
  #ifndef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
  #define SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION 0x00040000L
  #endif
  #ifndef SSL3_FLAGS_ALLOW_UNSAFE_LEGACY_RENEGOTIATION
  #define SSL3_FLAGS_ALLOW_UNSAFE_LEGACY_RENEGOTIATION 0x0010
  #endif
  
  /** Return values for tor_tls_classify_client_ciphers.
   *
   * @{
   */
  /** An error occurred when examining the client ciphers */
  #define CIPHERS_ERR -1
  /** The client cipher list indicates that a v1 handshake was in use. */
  #define CIPHERS_V1 1
  /** The client cipher list indicates that the client is using the v2 or the
   * v3 handshake, but that it is (probably!) lying about what ciphers it
   * supports */
  #define CIPHERS_V2 2
  /** The client cipher list indicates that the client is using the v2 or the
   * v3 handshake, and that it is telling the truth about what ciphers it
   * supports */
  #define CIPHERS_UNRESTRICTED 3
  /** @} */
  
  /** The ex_data index in which we store a pointer to an SSL object's
   * corresponding tor_tls_t object. */
  STATIC int tor_tls_object_ex_data_index = -1;
  
  /** Helper: Allocate tor_tls_object_ex_data_index. */
  STATIC void
  tor_tls_allocate_tor_tls_object_ex_data_index(void)
  {
    if (tor_tls_object_ex_data_index == -1) {
      tor_tls_object_ex_data_index =
        SSL_get_ex_new_index(0, NULL, NULL, NULL, NULL);
      tor_assert(tor_tls_object_ex_data_index != -1);
    }
  }
  
  /** Helper: given a SSL* pointer, return the tor_tls_t object using that
   * pointer. */
  STATIC tor_tls_t *
  tor_tls_get_by_ssl(const SSL *ssl)
  {
    tor_tls_t *result = SSL_get_ex_data(ssl, tor_tls_object_ex_data_index);
    if (result)
      tor_assert(result->magic == TOR_TLS_MAGIC);
    return result;
  }
  
  static void tor_tls_context_decref(tor_tls_context_t *ctx);
  static void tor_tls_context_incref(tor_tls_context_t *ctx);
  
  static int check_cert_lifetime_internal(int severity, const X509 *cert,
                                     time_t now,
                                     int past_tolerance, int future_tolerance);
  
  /** Global TLS contexts. We keep them here because nobody else needs
   * to touch them.
   *
   * @{ */
  STATIC tor_tls_context_t *server_tls_context = NULL;
  STATIC tor_tls_context_t *client_tls_context = NULL;
  /**@}*/
  
  /** True iff tor_tls_init() has been called. */
  static int tls_library_is_initialized = 0;
  
  /* Module-internal error codes. */
  #define TOR_TLS_SYSCALL_    (MIN_TOR_TLS_ERROR_VAL_ - 2)
  #define TOR_TLS_ZERORETURN_ (MIN_TOR_TLS_ERROR_VAL_ - 1)
  
  /** Write a description of the current state of <b>tls</b> into the
   * <b>sz</b>-byte buffer at <b>buf</b>. */
  void
  tor_tls_get_state_description(tor_tls_t *tls, char *buf, size_t sz)
  {
    const char *ssl_state;
    const char *tortls_state;
  
    if (PREDICT_UNLIKELY(!tls || !tls->ssl)) {
      strlcpy(buf, "(No SSL object)", sz);
      return;
    }
  
    ssl_state = SSL_state_string_long(tls->ssl);
    switch (tls->state) {
  #define CASE(st) case TOR_TLS_ST_##st: tortls_state = " in "#st ; break
      CASE(HANDSHAKE);
      CASE(OPEN);
      CASE(GOTCLOSE);
      CASE(SENTCLOSE);
      CASE(CLOSED);
      CASE(RENEGOTIATE);
  #undef CASE
    case TOR_TLS_ST_BUFFEREVENT:
      tortls_state = "";
      break;
    default:
      tortls_state = " in unknown TLS state";
      break;
    }
  
    tor_snprintf(buf, sz, "%s%s", ssl_state, tortls_state);
  }
  
  /** Log a single error <b>err</b> as returned by ERR_get_error(), which was
   * received while performing an operation <b>doing</b> on <b>tls</b>.  Log
   * the message at <b>severity</b>, in log domain <b>domain</b>. */
  void
  tor_tls_log_one_error(tor_tls_t *tls, unsigned long err,
                    int severity, int domain, const char *doing)
  {
    const char *state = NULL, *addr;
    const char *msg, *lib, *func;
  
    state = (tls && tls->ssl)?SSL_state_string_long(tls->ssl):"---";
  
    addr = tls ? tls->address : NULL;
  
    /* Some errors are known-benign, meaning they are the fault of the other
     * side of the connection. The caller doesn't know this, so override the
     * priority for those cases. */
    switch (ERR_GET_REASON(err)) {
      case SSL_R_HTTP_REQUEST:
      case SSL_R_HTTPS_PROXY_REQUEST:
      case SSL_R_RECORD_LENGTH_MISMATCH:
  #ifndef OPENSSL_1_1_API
      case SSL_R_RECORD_TOO_LARGE:
  #endif
      case SSL_R_UNKNOWN_PROTOCOL:
      case SSL_R_UNSUPPORTED_PROTOCOL:
        severity = LOG_INFO;
        break;
      default:
        break;
    }
  
    msg = (const char*)ERR_reason_error_string(err);
    lib = (const char*)ERR_lib_error_string(err);
    func = (const char*)ERR_func_error_string(err);
    if (!msg) msg = "(null)";
    if (!lib) lib = "(null)";
    if (!func) func = "(null)";
    if (doing) {
      tor_log(severity, domain, "TLS error while %s%s%s: %s (in %s:%s:%s)",
          doing, addr?" with ":"", addr?addr:"",
          msg, lib, func, state);
    } else {
      tor_log(severity, domain, "TLS error%s%s: %s (in %s:%s:%s)",
          addr?" with ":"", addr?addr:"",
          msg, lib, func, state);
    }
  }
  
  /** Log all pending tls errors at level <b>severity</b> in log domain
   * <b>domain</b>.  Use <b>doing</b> to describe our current activities.
   */
  STATIC void
  tls_log_errors(tor_tls_t *tls, int severity, int domain, const char *doing)
  {
    unsigned long err;
  
    while ((err = ERR_get_error()) != 0) {
      tor_tls_log_one_error(tls, err, severity, domain, doing);
    }
  }
  
  /** Convert an errno (or a WSAerrno on windows) into a TOR_TLS_* error
   * code. */
  STATIC int
  tor_errno_to_tls_error(int e)
  {
    switch (e) {
      case SOCK_ERRNO(ECONNRESET): // most common
        return TOR_TLS_ERROR_CONNRESET;
      case SOCK_ERRNO(ETIMEDOUT):
        return TOR_TLS_ERROR_TIMEOUT;
      case SOCK_ERRNO(EHOSTUNREACH):
      case SOCK_ERRNO(ENETUNREACH):
        return TOR_TLS_ERROR_NO_ROUTE;
      case SOCK_ERRNO(ECONNREFUSED):
        return TOR_TLS_ERROR_CONNREFUSED; // least common
      default:
        return TOR_TLS_ERROR_MISC;
    }
  }
  
  /** Given a TOR_TLS_* error code, return a string equivalent. */
  const char *
  tor_tls_err_to_string(int err)
  {
    if (err >= 0)
      return "[Not an error.]";
    switch (err) {
      case TOR_TLS_ERROR_MISC: return "misc error";
      case TOR_TLS_ERROR_IO: return "unexpected close";
      case TOR_TLS_ERROR_CONNREFUSED: return "connection refused";
      case TOR_TLS_ERROR_CONNRESET: return "connection reset";
      case TOR_TLS_ERROR_NO_ROUTE: return "host unreachable";
      case TOR_TLS_ERROR_TIMEOUT: return "connection timed out";
      case TOR_TLS_CLOSE: return "closed";
      case TOR_TLS_WANTREAD: return "want to read";
      case TOR_TLS_WANTWRITE: return "want to write";
      default: return "(unknown error code)";
    }
  }
  
  #define CATCH_SYSCALL 1
  #define CATCH_ZERO    2
  
  /** Given a TLS object and the result of an SSL_* call, use
   * SSL_get_error to determine whether an error has occurred, and if so
   * which one.  Return one of TOR_TLS_{DONE|WANTREAD|WANTWRITE|ERROR}.
   * If extra&CATCH_SYSCALL is true, return TOR_TLS_SYSCALL_ instead of
   * reporting syscall errors.  If extra&CATCH_ZERO is true, return
   * TOR_TLS_ZERORETURN_ instead of reporting zero-return errors.
   *
   * If an error has occurred, log it at level <b>severity</b> and describe the
   * current action as <b>doing</b>.
   */
  STATIC int
  tor_tls_get_error(tor_tls_t *tls, int r, int extra,
                    const char *doing, int severity, int domain)
  {
    int err = SSL_get_error(tls->ssl, r);
    int tor_error = TOR_TLS_ERROR_MISC;
    switch (err) {
      case SSL_ERROR_NONE:
        return TOR_TLS_DONE;
      case SSL_ERROR_WANT_READ:
        return TOR_TLS_WANTREAD;
      case SSL_ERROR_WANT_WRITE:
        return TOR_TLS_WANTWRITE;
      case SSL_ERROR_SYSCALL:
        if (extra&CATCH_SYSCALL)
          return TOR_TLS_SYSCALL_;
        if (r == 0) {
          tor_log(severity, LD_NET, "TLS error: unexpected close while %s (%s)",
              doing, SSL_state_string_long(tls->ssl));
          tor_error = TOR_TLS_ERROR_IO;
        } else {
          int e = tor_socket_errno(tls->socket);
          tor_log(severity, LD_NET,
              "TLS error: <syscall error while %s> (errno=%d: %s; state=%s)",
              doing, e, tor_socket_strerror(e),
              SSL_state_string_long(tls->ssl));
          tor_error = tor_errno_to_tls_error(e);
        }
        tls_log_errors(tls, severity, domain, doing);
        return tor_error;
      case SSL_ERROR_ZERO_RETURN:
        if (extra&CATCH_ZERO)
          return TOR_TLS_ZERORETURN_;
        tor_log(severity, LD_NET, "TLS connection closed while %s in state %s",
            doing, SSL_state_string_long(tls->ssl));
        tls_log_errors(tls, severity, domain, doing);
        return TOR_TLS_CLOSE;
      default:
        tls_log_errors(tls, severity, domain, doing);
        return TOR_TLS_ERROR_MISC;
    }
  }
  
  /** Initialize OpenSSL, unless it has already been initialized.
   */
  static void
  tor_tls_init(void)
  {
    check_no_tls_errors();
  
    if (!tls_library_is_initialized) {
      SSL_library_init();
      SSL_load_error_strings();
  
  #if (SIZEOF_VOID_P >= 8 &&                              \
       OPENSSL_VERSION_NUMBER >= OPENSSL_V_SERIES(1,0,1))
      long version = OpenSSL_version_num();
  
      /* LCOV_EXCL_START : we can't test these lines on the same machine */
      if (version >= OPENSSL_V_SERIES(1,0,1)) {
        /* Warn if we could *almost* be running with much faster ECDH.
           If we're built for a 64-bit target, using OpenSSL 1.0.1, but we
           don't have one of the built-in __uint128-based speedups, we are
           just one build operation away from an accelerated handshake.
  
           (We could be looking at OPENSSL_NO_EC_NISTP_64_GCC_128 instead of
            doing this test, but that gives compile-time options, not runtime
            behavior.)
        */
        EC_KEY *key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
        const EC_GROUP *g = key ? EC_KEY_get0_group(key) : NULL;
        const EC_METHOD *m = g ? EC_GROUP_method_of(g) : NULL;
        const int warn = (m == EC_GFp_simple_method() ||
                          m == EC_GFp_mont_method() ||
                          m == EC_GFp_nist_method());
        EC_KEY_free(key);
  
        if (warn)
          log_notice(LD_GENERAL, "We were built to run on a 64-bit CPU, with "
                     "OpenSSL 1.0.1 or later, but with a version of OpenSSL "
                     "that apparently lacks accelerated support for the NIST "
                     "P-224 and P-256 groups. Building openssl with such "
                     "support (using the enable-ec_nistp_64_gcc_128 option "
                     "when configuring it) would make ECDH much faster.");
      }
      /* LCOV_EXCL_STOP */
  #endif
  
      tor_tls_allocate_tor_tls_object_ex_data_index();
  
      tls_library_is_initialized = 1;
    }
  }
  
  /** Free all global TLS structures. */
  void
  tor_tls_free_all(void)
  {
    check_no_tls_errors();
  
    if (server_tls_context) {
      tor_tls_context_t *ctx = server_tls_context;
      server_tls_context = NULL;
      tor_tls_context_decref(ctx);
    }
    if (client_tls_context) {
      tor_tls_context_t *ctx = client_tls_context;
      client_tls_context = NULL;
      tor_tls_context_decref(ctx);
    }
  }
  
  /** We need to give OpenSSL a callback to verify certificates. This is
   * it: We always accept peer certs and complete the handshake.  We
   * don't validate them until later.
   */
  STATIC int
  always_accept_verify_cb(int preverify_ok,
                          X509_STORE_CTX *x509_ctx)
  {
    (void) preverify_ok;
    (void) x509_ctx;
    return 1;
  }
  
  /** Return a newly allocated X509 name with commonName <b>cname</b>. */
  static X509_NAME *
  tor_x509_name_new(const char *cname)
  {
    int nid;
    X509_NAME *name;
    /* LCOV_EXCL_BR_START : these branches will only fail on OOM errors */
    if (!(name = X509_NAME_new()))
      return NULL;
    if ((nid = OBJ_txt2nid("commonName")) == NID_undef) goto error;
    if (!(X509_NAME_add_entry_by_NID(name, nid, MBSTRING_ASC,
                                     (unsigned char*)cname, -1, -1, 0)))
      goto error;
    /* LCOV_EXCL_BR_STOP */
    return name;
   error:
    /* LCOV_EXCL_START : these lines will only execute on out of memory errors*/
    X509_NAME_free(name);
    return NULL;
    /* LCOV_EXCL_STOP */
  }
  
  /** Generate and sign an X509 certificate with the public key <b>rsa</b>,
   * signed by the private key <b>rsa_sign</b>.  The commonName of the
   * certificate will be <b>cname</b>; the commonName of the issuer will be
   * <b>cname_sign</b>. The cert will be valid for <b>cert_lifetime</b>
   * seconds, starting from some time in the past.
   *
   * Return a certificate on success, NULL on failure.
   */
  MOCK_IMPL(STATIC X509 *,
  tor_tls_create_certificate,(crypto_pk_t *rsa,
                              crypto_pk_t *rsa_sign,
                              const char *cname,
                              const char *cname_sign,
                              unsigned int cert_lifetime))
  {
    /* OpenSSL generates self-signed certificates with random 64-bit serial
     * numbers, so let's do that too. */
  #define SERIAL_NUMBER_SIZE 8
  
    time_t start_time, end_time;
    BIGNUM *serial_number = NULL;
    unsigned char serial_tmp[SERIAL_NUMBER_SIZE];
    EVP_PKEY *sign_pkey = NULL, *pkey=NULL;
    X509 *x509 = NULL;
    X509_NAME *name = NULL, *name_issuer=NULL;
  
    tor_tls_init();
  
    /* Make sure we're part-way through the certificate lifetime, rather
     * than having it start right now. Don't choose quite uniformly, since
     * then we might pick a time where we're about to expire. Lastly, be
     * sure to start on a day boundary. */
    time_t now = time(NULL);
    /* Our certificate lifetime will be cert_lifetime no matter what, but if we
     * start cert_lifetime in the past, we'll have 0 real lifetime.  instead we
     * start up to (cert_lifetime - min_real_lifetime - start_granularity) in
     * the past. */
    const time_t min_real_lifetime = 24*3600;
    const time_t start_granularity = 24*3600;
    time_t earliest_start_time = now - cert_lifetime + min_real_lifetime
      + start_granularity;
    /* Don't actually start in the future! */
    if (earliest_start_time >= now)
      earliest_start_time = now - 1;
    start_time = crypto_rand_time_range(earliest_start_time, now);
    /* Round the start time back to the start of a day. */
    start_time -= start_time % start_granularity;
  
    end_time = start_time + cert_lifetime;
  
    tor_assert(rsa);
    tor_assert(cname);
    tor_assert(rsa_sign);
    tor_assert(cname_sign);
    if (!(sign_pkey = crypto_pk_get_evp_pkey_(rsa_sign,1)))
      goto error;
    if (!(pkey = crypto_pk_get_evp_pkey_(rsa,0)))
      goto error;
    if (!(x509 = X509_new()))
      goto error;
    if (!(X509_set_version(x509, 2)))
      goto error;
  
    { /* our serial number is 8 random bytes. */
      crypto_rand((char *)serial_tmp, sizeof(serial_tmp));
      if (!(serial_number = BN_bin2bn(serial_tmp, sizeof(serial_tmp), NULL)))
        goto error;
      if (!(BN_to_ASN1_INTEGER(serial_number, X509_get_serialNumber(x509))))
        goto error;
    }
  
    if (!(name = tor_x509_name_new(cname)))
      goto error;
    if (!(X509_set_subject_name(x509, name)))
      goto error;
    if (!(name_issuer = tor_x509_name_new(cname_sign)))
      goto error;
    if (!(X509_set_issuer_name(x509, name_issuer)))
      goto error;
  
    if (!X509_time_adj(X509_get_notBefore(x509),0,&start_time))
      goto error;
    if (!X509_time_adj(X509_get_notAfter(x509),0,&end_time))
      goto error;
    if (!X509_set_pubkey(x509, pkey))
      goto error;
  
    if (!X509_sign(x509, sign_pkey, EVP_sha256()))
      goto error;
  
    goto done;
   error:
    if (x509) {
      X509_free(x509);
      x509 = NULL;
    }
   done:
    tls_log_errors(NULL, LOG_WARN, LD_NET, "generating certificate");
    if (sign_pkey)
      EVP_PKEY_free(sign_pkey);
    if (pkey)
      EVP_PKEY_free(pkey);
    if (serial_number)
      BN_clear_free(serial_number);
    if (name)
      X509_NAME_free(name);
    if (name_issuer)
      X509_NAME_free(name_issuer);
    return x509;
  
  #undef SERIAL_NUMBER_SIZE
  }
  
  /** List of ciphers that servers should select from when the client might be
   * claiming extra unsupported ciphers in order to avoid fingerprinting.  */
  #define SERVER_CIPHER_LIST                         \
    (TLS1_TXT_DHE_RSA_WITH_AES_256_SHA ":"           \
     TLS1_TXT_DHE_RSA_WITH_AES_128_SHA)
  
  /** List of ciphers that servers should select from when we actually have
   * our choice of what cipher to use. */
  static const char UNRESTRICTED_SERVER_CIPHER_LIST[] =
    /* This list is autogenerated with the gen_server_ciphers.py script;
     * don't hand-edit it. */
  #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_256_GCM_SHA384
         TLS1_TXT_ECDHE_RSA_WITH_AES_256_GCM_SHA384 ":"
  #endif
  #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_128_GCM_SHA256
         TLS1_TXT_ECDHE_RSA_WITH_AES_128_GCM_SHA256 ":"
  #endif
  #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_256_SHA384
         TLS1_TXT_ECDHE_RSA_WITH_AES_256_SHA384 ":"
  #endif
  #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_128_SHA256
         TLS1_TXT_ECDHE_RSA_WITH_AES_128_SHA256 ":"
  #endif
  #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_256_CBC_SHA
         TLS1_TXT_ECDHE_RSA_WITH_AES_256_CBC_SHA ":"
  #endif
  #ifdef TLS1_TXT_ECDHE_RSA_WITH_AES_128_CBC_SHA
         TLS1_TXT_ECDHE_RSA_WITH_AES_128_CBC_SHA ":"
  #endif
  #ifdef TLS1_TXT_DHE_RSA_WITH_AES_256_GCM_SHA384
         TLS1_TXT_DHE_RSA_WITH_AES_256_GCM_SHA384 ":"
  #endif
  #ifdef TLS1_TXT_DHE_RSA_WITH_AES_128_GCM_SHA256
         TLS1_TXT_DHE_RSA_WITH_AES_128_GCM_SHA256 ":"
  #endif
  #ifdef TLS1_TXT_DHE_RSA_WITH_AES_256_CCM
         TLS1_TXT_DHE_RSA_WITH_AES_256_CCM ":"
  #endif
  #ifdef TLS1_TXT_DHE_RSA_WITH_AES_128_CCM
         TLS1_TXT_DHE_RSA_WITH_AES_128_CCM ":"
  #endif
  #ifdef TLS1_TXT_DHE_RSA_WITH_AES_256_SHA256
         TLS1_TXT_DHE_RSA_WITH_AES_256_SHA256 ":"
  #endif
  #ifdef TLS1_TXT_DHE_RSA_WITH_AES_128_SHA256
         TLS1_TXT_DHE_RSA_WITH_AES_128_SHA256 ":"
  #endif
         /* Required */
         TLS1_TXT_DHE_RSA_WITH_AES_256_SHA ":"
         /* Required */
         TLS1_TXT_DHE_RSA_WITH_AES_128_SHA ":"
  #ifdef TLS1_TXT_ECDHE_RSA_WITH_CHACHA20_POLY1305
         TLS1_TXT_ECDHE_RSA_WITH_CHACHA20_POLY1305 ":"
  #endif
  #ifdef TLS1_TXT_DHE_RSA_WITH_CHACHA20_POLY1305
         TLS1_TXT_DHE_RSA_WITH_CHACHA20_POLY1305
  #endif
    ;
  
  /* Note: to set up your own private testing network with link crypto
   * disabled, set your Tors' cipher list to
   * (SSL3_TXT_RSA_NULL_SHA).  If you do this, you won't be able to communicate
   * with any of the "real" Tors, though. */
  
  #define CIPHER(id, name) name ":"
  #define XCIPHER(id, name)
  /** List of ciphers that clients should advertise, omitting items that
   * our OpenSSL doesn't know about. */
  static const char CLIENT_CIPHER_LIST[] =
  #include "ciphers.inc"
    /* Tell it not to use SSLv2 ciphers, so that it can select an SSLv3 version
     * of any cipher we say. */
    "!SSLv2"
    ;
  #undef CIPHER
  #undef XCIPHER
  
  /** Free all storage held in <b>cert</b> */
  void
  tor_x509_cert_free(tor_x509_cert_t *cert)
  {
    if (! cert)
      return;
    if (cert->cert)
      X509_free(cert->cert);
    tor_free(cert->encoded);
    memwipe(cert, 0x03, sizeof(*cert));
    /* LCOV_EXCL_BR_START since cert will never be NULL here */
    tor_free(cert);
    /* LCOV_EXCL_BR_STOP */
  }
  
  /**
   * Allocate a new tor_x509_cert_t to hold the certificate "x509_cert".
   *
   * Steals a reference to x509_cert.
   */
  MOCK_IMPL(STATIC tor_x509_cert_t *,
  tor_x509_cert_new,(X509 *x509_cert))
  {
    tor_x509_cert_t *cert;
    EVP_PKEY *pkey;
    RSA *rsa;
    int length;
    unsigned char *buf = NULL;
  
    if (!x509_cert)
      return NULL;
  
    length = i2d_X509(x509_cert, &buf);
    cert = tor_malloc_zero(sizeof(tor_x509_cert_t));
    if (length <= 0 || buf == NULL) {
      /* LCOV_EXCL_START for the same reason as the exclusion above */
      tor_free(cert);
      log_err(LD_CRYPTO, "Couldn't get length of encoded x509 certificate");
      X509_free(x509_cert);
      return NULL;
      /* LCOV_EXCL_STOP */
    }
    cert->encoded_len = (size_t) length;
    cert->encoded = tor_malloc(length);
    memcpy(cert->encoded, buf, length);
    OPENSSL_free(buf);
  
    cert->cert = x509_cert;
  
    crypto_common_digests(&cert->cert_digests,
                      (char*)cert->encoded, cert->encoded_len);
  
    if ((pkey = X509_get_pubkey(x509_cert)) &&
        (rsa = EVP_PKEY_get1_RSA(pkey))) {
      crypto_pk_t *pk = crypto_new_pk_from_rsa_(rsa);
      crypto_pk_get_common_digests(pk, &cert->pkey_digests);
      cert->pkey_digests_set = 1;
      crypto_pk_free(pk);
      EVP_PKEY_free(pkey);
    }
  
    return cert;
  }
  
  /** Return a new copy of <b>cert</b>. */
  tor_x509_cert_t *
  tor_x509_cert_dup(const tor_x509_cert_t *cert)
  {
    tor_assert(cert);
    X509 *x509 = cert->cert;
    return tor_x509_cert_new(X509_dup(x509));
  }
  
  /** Read a DER-encoded X509 cert, of length exactly <b>certificate_len</b>,
   * from a <b>certificate</b>.  Return a newly allocated tor_x509_cert_t on
   * success and NULL on failure. */
  tor_x509_cert_t *
  tor_x509_cert_decode(const uint8_t *certificate, size_t certificate_len)
  {
    X509 *x509;
    const unsigned char *cp = (const unsigned char *)certificate;
    tor_x509_cert_t *newcert;
    tor_assert(certificate);
    check_no_tls_errors();
  
    if (certificate_len > INT_MAX)
      goto err;
  
    x509 = d2i_X509(NULL, &cp, (int)certificate_len);
  
    if (!x509)
      goto err; /* Couldn't decode */
    if (cp - certificate != (int)certificate_len) {
      X509_free(x509);
      goto err; /* Didn't use all the bytes */
    }
    newcert = tor_x509_cert_new(x509);
    if (!newcert) {
      goto err;
    }
    if (newcert->encoded_len != certificate_len ||
        fast_memneq(newcert->encoded, certificate, certificate_len)) {
      /* Cert wasn't in DER */
      tor_x509_cert_free(newcert);
      goto err;
    }
    return newcert;
   err:
    tls_log_errors(NULL, LOG_INFO, LD_CRYPTO, "decoding a certificate");
    return NULL;
  }
  
  /** Set *<b>encoded_out</b> and *<b>size_out</b> to <b>cert</b>'s encoded DER
   * representation and length, respectively. */
  void
  tor_x509_cert_get_der(const tor_x509_cert_t *cert,
                   const uint8_t **encoded_out, size_t *size_out)
  {
    tor_assert(cert);
    tor_assert(encoded_out);
    tor_assert(size_out);
    *encoded_out = cert->encoded;
    *size_out = cert->encoded_len;
  }
  
  /** Return a set of digests for the public key in <b>cert</b>, or NULL if this
   * cert's public key is not one we know how to take the digest of. */
  const common_digests_t *
  tor_x509_cert_get_id_digests(const tor_x509_cert_t *cert)
  {
    if (cert->pkey_digests_set)
      return &cert->pkey_digests;
    else
      return NULL;
  }
  
  /** Return a set of digests for the public key in <b>cert</b>. */
  const common_digests_t *
  tor_x509_cert_get_cert_digests(const tor_x509_cert_t *cert)
  {
    return &cert->cert_digests;
  }
  
  /** Remove a reference to <b>ctx</b>, and free it if it has no more
   * references. */
  static void
  tor_tls_context_decref(tor_tls_context_t *ctx)
  {
    tor_assert(ctx);
    if (--ctx->refcnt == 0) {
      SSL_CTX_free(ctx->ctx);
      tor_x509_cert_free(ctx->my_link_cert);
      tor_x509_cert_free(ctx->my_id_cert);
      tor_x509_cert_free(ctx->my_auth_cert);
      crypto_pk_free(ctx->link_key);
      crypto_pk_free(ctx->auth_key);
      /* LCOV_EXCL_BR_START since ctx will never be NULL here */
      tor_free(ctx);
      /* LCOV_EXCL_BR_STOP */
    }
  }
  
  /** Set *<b>link_cert_out</b> and *<b>id_cert_out</b> to the link certificate
   * and ID certificate that we're currently using for our V3 in-protocol
   * handshake's certificate chain.  If <b>server</b> is true, provide the certs
   * that we use in server mode (auth, ID); otherwise, provide the certs that we
   * use in client mode. (link, ID) */
  int
  tor_tls_get_my_certs(int server,
                       const tor_x509_cert_t **link_cert_out,
                       const tor_x509_cert_t **id_cert_out)
  {
    tor_tls_context_t *ctx = server ? server_tls_context : client_tls_context;
    if (! ctx)
      return -1;
    if (link_cert_out)
      *link_cert_out = server ? ctx->my_link_cert : ctx->my_auth_cert;
    if (id_cert_out)
      *id_cert_out = ctx->my_id_cert;
    return 0;
  }
  
  /**
   * Return the authentication key that we use to authenticate ourselves as a
   * client in the V3 in-protocol handshake.
   */
  crypto_pk_t *
  tor_tls_get_my_client_auth_key(void)
  {
    if (! client_tls_context)
      return NULL;
    return client_tls_context->auth_key;
  }
  
  /**
   * Return a newly allocated copy of the public key that a certificate
   * certifies. Watch out! This returns NULL if the cert's key is not RSA.
   */
  crypto_pk_t *
  tor_tls_cert_get_key(tor_x509_cert_t *cert)
  {
    crypto_pk_t *result = NULL;
    EVP_PKEY *pkey = X509_get_pubkey(cert->cert);
    RSA *rsa;
    if (!pkey)
      return NULL;
    rsa = EVP_PKEY_get1_RSA(pkey);
    if (!rsa) {
      EVP_PKEY_free(pkey);
      return NULL;
    }
    result = crypto_new_pk_from_rsa_(rsa);
    EVP_PKEY_free(pkey);
    return result;
  }
  
  /** Return true iff the other side of <b>tls</b> has authenticated to us, and
   * the key certified in <b>cert</b> is the same as the key they used to do it.
   */
  MOCK_IMPL(int,
  tor_tls_cert_matches_key,(const tor_tls_t *tls, const tor_x509_cert_t *cert))
  {
    X509 *peercert = SSL_get_peer_certificate(tls->ssl);
    EVP_PKEY *link_key = NULL, *cert_key = NULL;
    int result;
  
    if (!peercert)
      return 0;
    link_key = X509_get_pubkey(peercert);
    cert_key = X509_get_pubkey(cert->cert);
  
    result = link_key && cert_key && EVP_PKEY_cmp(cert_key, link_key) == 1;
  
    X509_free(peercert);
    if (link_key)
      EVP_PKEY_free(link_key);
    if (cert_key)
      EVP_PKEY_free(cert_key);
  
    return result;
  }
  
  /** Check whether <b>cert</b> is well-formed, currently live, and correctly
   * signed by the public key in <b>signing_cert</b>.  If <b>check_rsa_1024</b>,
   * make sure that it has an RSA key with 1024 bits; otherwise, just check that
   * the key is long enough. Return 1 if the cert is good, and 0 if it's bad or
   * we couldn't check it. */
  int
  tor_tls_cert_is_valid(int severity,
                        const tor_x509_cert_t *cert,
                        const tor_x509_cert_t *signing_cert,
                        time_t now,
                        int check_rsa_1024)
  {
    check_no_tls_errors();
    EVP_PKEY *cert_key;
    int r, key_ok = 0;
  
    if (!signing_cert || !cert)
      goto bad;
  
    EVP_PKEY *signing_key = X509_get_pubkey(signing_cert->cert);
    if (!signing_key)
      goto bad;
    r = X509_verify(cert->cert, signing_key);
    EVP_PKEY_free(signing_key);
    if (r <= 0)
      goto bad;
  
    /* okay, the signature checked out right.  Now let's check the check the
     * lifetime. */
    if (check_cert_lifetime_internal(severity, cert->cert, now,
                                     48*60*60, 30*24*60*60) < 0)
      goto bad;
  
    cert_key = X509_get_pubkey(cert->cert);
    if (check_rsa_1024 && cert_key) {
      RSA *rsa = EVP_PKEY_get1_RSA(cert_key);
  #ifdef OPENSSL_1_1_API
      if (rsa && RSA_bits(rsa) == 1024)
  #else
      if (rsa && BN_num_bits(rsa->n) == 1024)
  #endif
        key_ok = 1;
      if (rsa)
        RSA_free(rsa);
    } else if (cert_key) {
      int min_bits = 1024;
  #ifdef EVP_PKEY_EC
      if (EVP_PKEY_base_id(cert_key) == EVP_PKEY_EC)
        min_bits = 128;
  #endif
      if (EVP_PKEY_bits(cert_key) >= min_bits)
        key_ok = 1;
    }
    EVP_PKEY_free(cert_key);
    if (!key_ok)
      goto bad;
  
    /* XXXX compare DNs or anything? */
  
    return 1;
   bad:
    tls_log_errors(NULL, LOG_INFO, LD_CRYPTO, "checking a certificate");
    return 0;
  }
  
  /** Increase the reference count of <b>ctx</b>. */
  static void
  tor_tls_context_incref(tor_tls_context_t *ctx)
  {
    ++ctx->refcnt;
  }
  
  /** Create new global client and server TLS contexts.
   *
   * If <b>server_identity</b> is NULL, this will not generate a server
   * TLS context. If TOR_TLS_CTX_IS_PUBLIC_SERVER is set in <b>flags</b>, use
   * the same TLS context for incoming and outgoing connections, and
   * ignore <b>client_identity</b>. If one of TOR_TLS_CTX_USE_ECDHE_P{224,256}
   * is set in <b>flags</b>, use that ECDHE group if possible; otherwise use
   * the default ECDHE group. */
  int
  tor_tls_context_init(unsigned flags,
                       crypto_pk_t *client_identity,
                       crypto_pk_t *server_identity,
                       unsigned int key_lifetime)
  {
    int rv1 = 0;
    int rv2 = 0;
    const int is_public_server = flags & TOR_TLS_CTX_IS_PUBLIC_SERVER;
    check_no_tls_errors();
  
    if (is_public_server) {
      tor_tls_context_t *new_ctx;
      tor_tls_context_t *old_ctx;
  
      tor_assert(server_identity != NULL);
  
      rv1 = tor_tls_context_init_one(&server_tls_context,
                                     server_identity,
                                     key_lifetime, flags, 0);
  
      if (rv1 >= 0) {
        new_ctx = server_tls_context;
        tor_tls_context_incref(new_ctx);
        old_ctx = client_tls_context;
        client_tls_context = new_ctx;
  
        if (old_ctx != NULL) {
          tor_tls_context_decref(old_ctx);
        }
      }
    } else {
      if (server_identity != NULL) {
        rv1 = tor_tls_context_init_one(&server_tls_context,
                                       server_identity,
                                       key_lifetime,
                                       flags,
                                       0);
      } else {
        tor_tls_context_t *old_ctx = server_tls_context;
        server_tls_context = NULL;
  
        if (old_ctx != NULL) {
          tor_tls_context_decref(old_ctx);
        }
      }
  
      rv2 = tor_tls_context_init_one(&client_tls_context,
                                     client_identity,
                                     key_lifetime,
                                     flags,
                                     1);
    }
  
    tls_log_errors(NULL, LOG_WARN, LD_CRYPTO, "constructing a TLS context");
    return MIN(rv1, rv2);
  }
  
  /** Create a new global TLS context.
   *
   * You can call this function multiple times.  Each time you call it,
   * it generates new certificates; all new connections will use
   * the new SSL context.
   */
  STATIC int
  tor_tls_context_init_one(tor_tls_context_t **ppcontext,
                           crypto_pk_t *identity,
                           unsigned int key_lifetime,
                           unsigned int flags,
                           int is_client)
  {
    tor_tls_context_t *new_ctx = tor_tls_context_new(identity,
                                                     key_lifetime,
                                                     flags,
                                                     is_client);
    tor_tls_context_t *old_ctx = *ppcontext;
  
    if (new_ctx != NULL) {
      *ppcontext = new_ctx;
  
      /* Free the old context if one existed. */
      if (old_ctx != NULL) {
        /* This is safe even if there are open connections: we reference-
         * count tor_tls_context_t objects. */
        tor_tls_context_decref(old_ctx);
      }
    }
  
    return ((new_ctx != NULL) ? 0 : -1);
  }
  
  /** The group we should use for ecdhe when none was selected. */
  #define  NID_tor_default_ecdhe_group NID_X9_62_prime256v1
  
  #define RSA_LINK_KEY_BITS 2048
  
  /** Create a new TLS context for use with Tor TLS handshakes.
   * <b>identity</b> should be set to the identity key used to sign the
   * certificate.
   */
  STATIC tor_tls_context_t *
  tor_tls_context_new(crypto_pk_t *identity, unsigned int key_lifetime,
                      unsigned flags, int is_client)
  {
    crypto_pk_t *rsa = NULL, *rsa_auth = NULL;
    EVP_PKEY *pkey = NULL;
    tor_tls_context_t *result = NULL;
    X509 *cert = NULL, *idcert = NULL, *authcert = NULL;
    char *nickname = NULL, *nn2 = NULL;
  
    tor_tls_init();
    nickname = crypto_random_hostname(8, 20, "www.", ".net");
  #ifdef DISABLE_V3_LINKPROTO_SERVERSIDE
    nn2 = crypto_random_hostname(8, 20, "www.", ".net");
  #else
    nn2 = crypto_random_hostname(8, 20, "www.", ".com");
  #endif
  
    /* Generate short-term RSA key for use with TLS. */
    if (!(rsa = crypto_pk_new()))
      goto error;
    if (crypto_pk_generate_key_with_bits(rsa, RSA_LINK_KEY_BITS)<0)
      goto error;
    if (!is_client) {
      /* Generate short-term RSA key for use in the in-protocol ("v3")
       * authentication handshake. */
      if (!(rsa_auth = crypto_pk_new()))
        goto error;
      if (crypto_pk_generate_key(rsa_auth)<0)
        goto error;
      /* Create a link certificate signed by identity key. */
      cert = tor_tls_create_certificate(rsa, identity, nickname, nn2,
                                        key_lifetime);
      /* Create self-signed certificate for identity key. */
      idcert = tor_tls_create_certificate(identity, identity, nn2, nn2,
                                          IDENTITY_CERT_LIFETIME);
      /* Create an authentication certificate signed by identity key. */
      authcert = tor_tls_create_certificate(rsa_auth, identity, nickname, nn2,
                                            key_lifetime);
      if (!cert || !idcert || !authcert) {
        log_warn(LD_CRYPTO, "Error creating certificate");
        goto error;
      }
    }
  
    result = tor_malloc_zero(sizeof(tor_tls_context_t));
    result->refcnt = 1;
    if (!is_client) {
      result->my_link_cert = tor_x509_cert_new(X509_dup(cert));
      result->my_id_cert = tor_x509_cert_new(X509_dup(idcert));
      result->my_auth_cert = tor_x509_cert_new(X509_dup(authcert));
      if (!result->my_link_cert || !result->my_id_cert || !result->my_auth_cert)
        goto error;
      result->link_key = crypto_pk_dup_key(rsa);
      result->auth_key = crypto_pk_dup_key(rsa_auth);
    }
  
  #if 0
    /* Tell OpenSSL to only use TLS1.  This may have subtly different results
     * from SSLv23_method() with SSLv2 and SSLv3 disabled, so we need to do some
     * investigation before we consider adjusting it. It should be compatible
     * with existing Tors. */
    if (!(result->ctx = SSL_CTX_new(TLSv1_method())))
      goto error;
  #endif
  
    /* Tell OpenSSL to use TLS 1.0 or later but not SSL2 or SSL3. */
  #ifdef HAVE_TLS_METHOD
    if (!(result->ctx = SSL_CTX_new(TLS_method())))
      goto error;
  #else
    if (!(result->ctx = SSL_CTX_new(SSLv23_method())))
      goto error;
  #endif
    SSL_CTX_set_options(result->ctx, SSL_OP_NO_SSLv2);
    SSL_CTX_set_options(result->ctx, SSL_OP_NO_SSLv3);
  
    /* Prefer the server's ordering of ciphers: the client's ordering has
    * historically been chosen for fingerprinting resistance. */
    SSL_CTX_set_options(result->ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);
  
    /* Disable TLS tickets if they're supported.  We never want to use them;
     * using them can make our perfect forward secrecy a little worse, *and*
     * create an opportunity to fingerprint us (since it's unusual to use them
     * with TLS sessions turned off).
     *
     * In 0.2.4, clients advertise support for them though, to avoid a TLS
     * distinguishability vector.  This can give us worse PFS, though, if we
     * get a server that doesn't set SSL_OP_NO_TICKET.  With luck, there will
     * be few such servers by the time 0.2.4 is more stable.
     */
  #ifdef SSL_OP_NO_TICKET
    if (! is_client) {
      SSL_CTX_set_options(result->ctx, SSL_OP_NO_TICKET);
    }
  #endif
  
    SSL_CTX_set_options(result->ctx, SSL_OP_SINGLE_DH_USE);
    SSL_CTX_set_options(result->ctx, SSL_OP_SINGLE_ECDH_USE);
  
  #ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
    SSL_CTX_set_options(result->ctx,
                        SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION);
  #endif
    /* Yes, we know what we are doing here.  No, we do not treat a renegotiation
     * as authenticating any earlier-received data.
     */
    {
      SSL_CTX_set_options(result->ctx,
                          SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION);
    }
  #ifdef SSL_OP_NO_COMPRESSION
    SSL_CTX_set_options(result->ctx, SSL_OP_NO_COMPRESSION);
  #endif
  #if OPENSSL_VERSION_NUMBER < OPENSSL_V_SERIES(1,1,0)
  #ifndef OPENSSL_NO_COMP
    /* Don't actually allow compression; it uses ram and time, but the data
     * we transmit is all encrypted anyway. */
    if (result->ctx->comp_methods)
      result->ctx->comp_methods = NULL;
  #endif
  #endif
  #ifdef SSL_MODE_RELEASE_BUFFERS
    SSL_CTX_set_mode(result->ctx, SSL_MODE_RELEASE_BUFFERS);
  #endif
    if (! is_client) {
      if (cert && !SSL_CTX_use_certificate(result->ctx,cert))
        goto error;
      X509_free(cert); /* We just added a reference to cert. */
      cert=NULL;
      if (idcert) {
        X509_STORE *s = SSL_CTX_get_cert_store(result->ctx);
        tor_assert(s);
        X509_STORE_add_cert(s, idcert);
        X509_free(idcert); /* The context now owns the reference to idcert */
        idcert = NULL;
      }
    }
    SSL_CTX_set_session_cache_mode(result->ctx, SSL_SESS_CACHE_OFF);
    if (!is_client) {
      tor_assert(rsa);
      if (!(pkey = crypto_pk_get_evp_pkey_(rsa,1)))
        goto error;
      if (!SSL_CTX_use_PrivateKey(result->ctx, pkey))
        goto error;
      EVP_PKEY_free(pkey);
      pkey = NULL;
      if (!SSL_CTX_check_private_key(result->ctx))
        goto error;
    }
    {
      crypto_dh_t *dh = crypto_dh_new(DH_TYPE_TLS);
      tor_assert(dh);
      SSL_CTX_set_tmp_dh(result->ctx, crypto_dh_get_dh_(dh));
      crypto_dh_free(dh);
    }
    if (! is_client) {
      int nid;
      EC_KEY *ec_key;
      if (flags & TOR_TLS_CTX_USE_ECDHE_P224)
        nid = NID_secp224r1;
      else if (flags & TOR_TLS_CTX_USE_ECDHE_P256)
        nid = NID_X9_62_prime256v1;
      else
        nid = NID_tor_default_ecdhe_group;
      /* Use P-256 for ECDHE. */
      ec_key = EC_KEY_new_by_curve_name(nid);
      if (ec_key != NULL) /*XXXX Handle errors? */
        SSL_CTX_set_tmp_ecdh(result->ctx, ec_key);
      EC_KEY_free(ec_key);
    }
    SSL_CTX_set_verify(result->ctx, SSL_VERIFY_PEER,
                       always_accept_verify_cb);
    /* let us realloc bufs that we're writing from */
    SSL_CTX_set_mode(result->ctx, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
  
    if (rsa)
      crypto_pk_free(rsa);
    if (rsa_auth)
      crypto_pk_free(rsa_auth);
    X509_free(authcert);
    tor_free(nickname);
    tor_free(nn2);
    return result;
  
   error:
    tls_log_errors(NULL, LOG_WARN, LD_NET, "creating TLS context");
    tor_free(nickname);
    tor_free(nn2);
    if (pkey)
      EVP_PKEY_free(pkey);
    if (rsa)
      crypto_pk_free(rsa);
    if (rsa_auth)
      crypto_pk_free(rsa_auth);
    if (result)
      tor_tls_context_decref(result);
    if (cert)
      X509_free(cert);
    if (idcert)
      X509_free(idcert);
    if (authcert)
      X509_free(authcert);
    return NULL;
  }
  
  /** Invoked when a TLS state changes: log the change at severity 'debug' */
  STATIC void
  tor_tls_debug_state_callback(const SSL *ssl, int type, int val)
  {
    /* LCOV_EXCL_START since this depends on whether debug is captured or not */
    log_debug(LD_HANDSHAKE, "SSL %p is now in state %s [type=%d,val=%d].",
              ssl, SSL_state_string_long(ssl), type, val);
    /* LCOV_EXCL_STOP */
  }
  
  /* Return the name of the negotiated ciphersuite in use on <b>tls</b> */
  const char *
  tor_tls_get_ciphersuite_name(tor_tls_t *tls)
  {
    return SSL_get_cipher(tls->ssl);
  }
  
  /* Here's the old V2 cipher list we sent from 0.2.1.1-alpha up to
   * 0.2.3.17-beta. If a client is using this list, we can't believe the ciphers
   * that it claims to support.  We'll prune this list to remove the ciphers
   * *we* don't recognize. */
  STATIC uint16_t v2_cipher_list[] = {
    0xc00a, /* TLS1_TXT_ECDHE_ECDSA_WITH_AES_256_CBC_SHA */
    0xc014, /* TLS1_TXT_ECDHE_RSA_WITH_AES_256_CBC_SHA */
    0x0039, /* TLS1_TXT_DHE_RSA_WITH_AES_256_SHA */
    0x0038, /* TLS1_TXT_DHE_DSS_WITH_AES_256_SHA */
    0xc00f, /* TLS1_TXT_ECDH_RSA_WITH_AES_256_CBC_SHA */
    0xc005, /* TLS1_TXT_ECDH_ECDSA_WITH_AES_256_CBC_SHA */
    0x0035, /* TLS1_TXT_RSA_WITH_AES_256_SHA */
    0xc007, /* TLS1_TXT_ECDHE_ECDSA_WITH_RC4_128_SHA */
    0xc009, /* TLS1_TXT_ECDHE_ECDSA_WITH_AES_128_CBC_SHA */
    0xc011, /* TLS1_TXT_ECDHE_RSA_WITH_RC4_128_SHA */
    0xc013, /* TLS1_TXT_ECDHE_RSA_WITH_AES_128_CBC_SHA */
    0x0033, /* TLS1_TXT_DHE_RSA_WITH_AES_128_SHA */
    0x0032, /* TLS1_TXT_DHE_DSS_WITH_AES_128_SHA */
    0xc00c, /* TLS1_TXT_ECDH_RSA_WITH_RC4_128_SHA */
    0xc00e, /* TLS1_TXT_ECDH_RSA_WITH_AES_128_CBC_SHA */
    0xc002, /* TLS1_TXT_ECDH_ECDSA_WITH_RC4_128_SHA */
    0xc004, /* TLS1_TXT_ECDH_ECDSA_WITH_AES_128_CBC_SHA */
    0x0004, /* SSL3_TXT_RSA_RC4_128_MD5 */
    0x0005, /* SSL3_TXT_RSA_RC4_128_SHA */
    0x002f, /* TLS1_TXT_RSA_WITH_AES_128_SHA */
    0xc008, /* TLS1_TXT_ECDHE_ECDSA_WITH_DES_192_CBC3_SHA */
    0xc012, /* TLS1_TXT_ECDHE_RSA_WITH_DES_192_CBC3_SHA */
    0x0016, /* SSL3_TXT_EDH_RSA_DES_192_CBC3_SHA */
    0x0013, /* SSL3_TXT_EDH_DSS_DES_192_CBC3_SHA */
    0xc00d, /* TLS1_TXT_ECDH_RSA_WITH_DES_192_CBC3_SHA */
    0xc003, /* TLS1_TXT_ECDH_ECDSA_WITH_DES_192_CBC3_SHA */
    0xfeff, /* SSL3_TXT_RSA_FIPS_WITH_3DES_EDE_CBC_SHA */
    0x000a, /* SSL3_TXT_RSA_DES_192_CBC3_SHA */
    0
  };
  /** Have we removed the unrecognized ciphers from v2_cipher_list yet? */
  static int v2_cipher_list_pruned = 0;
  
  /** Return 0 if <b>m</b> does not support the cipher with ID <b>cipher</b>;
   * return 1 if it does support it, or if we have no way to tell. */
  STATIC int
  find_cipher_by_id(const SSL *ssl, const SSL_METHOD *m, uint16_t cipher)
  {
    const SSL_CIPHER *c;
  #ifdef HAVE_SSL_CIPHER_FIND
    (void) m;
    {
      unsigned char cipherid[3];
      tor_assert(ssl);
      set_uint16(cipherid, htons(cipher));
      cipherid[2] = 0; /* If ssl23_get_cipher_by_char finds no cipher starting
                        * with a two-byte 'cipherid', it may look for a v2
                        * cipher with the appropriate 3 bytes. */
      c = SSL_CIPHER_find((SSL*)ssl, cipherid);
      if (c)
        tor_assert((SSL_CIPHER_get_id(c) & 0xffff) == cipher);
      return c != NULL;
    }
  #else
  
  # if defined(HAVE_STRUCT_SSL_METHOD_ST_GET_CIPHER_BY_CHAR)
    if (m && m->get_cipher_by_char) {
      unsigned char cipherid[3];
      set_uint16(cipherid, htons(cipher));
      cipherid[2] = 0; /* If ssl23_get_cipher_by_char finds no cipher starting
                        * with a two-byte 'cipherid', it may look for a v2
                        * cipher with the appropriate 3 bytes. */
      c = m->get_cipher_by_char(cipherid);
      if (c)
        tor_assert((c->id & 0xffff) == cipher);
      return c != NULL;
    }
  # endif
  # ifndef OPENSSL_1_1_API
    if (m && m->get_cipher && m->num_ciphers) {
      /* It would seem that some of the "let's-clean-up-openssl" forks have
       * removed the get_cipher_by_char function.  Okay, so now you get a
       * quadratic search.
       */
      int i;
      for (i = 0; i < m->num_ciphers(); ++i) {
        c = m->get_cipher(i);
        if (c && (c->id & 0xffff) == cipher) {
          return 1;
        }
      }
      return 0;
    }
  # endif
    (void) ssl;
    (void) m;
    (void) cipher;
    return 1; /* No way to search */
  #endif
  }
  
  /** Remove from v2_cipher_list every cipher that we don't support, so that
   * comparing v2_cipher_list to a client's cipher list will give a sensible
   * result. */
  static void
  prune_v2_cipher_list(const SSL *ssl)
  {
    uint16_t *inp, *outp;
  #ifdef HAVE_TLS_METHOD
    const SSL_METHOD *m = TLS_method();
  #else
    const SSL_METHOD *m = SSLv23_method();
  #endif
  
    inp = outp = v2_cipher_list;
    while (*inp) {
      if (find_cipher_by_id(ssl, m, *inp)) {
        *outp++ = *inp++;
      } else {
        inp++;
      }
    }
    *outp = 0;
  
    v2_cipher_list_pruned = 1;
  }
  
  /** Examine the client cipher list in <b>ssl</b>, and determine what kind of
   * client it is.  Return one of CIPHERS_ERR, CIPHERS_V1, CIPHERS_V2,
   * CIPHERS_UNRESTRICTED.
   **/
  STATIC int
  tor_tls_classify_client_ciphers(const SSL *ssl,
                                  STACK_OF(SSL_CIPHER) *peer_ciphers)
  {
    int i, res;
    tor_tls_t *tor_tls;
    if (PREDICT_UNLIKELY(!v2_cipher_list_pruned))
      prune_v2_cipher_list(ssl);
  
    tor_tls = tor_tls_get_by_ssl(ssl);
    if (tor_tls && tor_tls->client_cipher_list_type)
      return tor_tls->client_cipher_list_type;
  
    /* If we reached this point, we just got a client hello.  See if there is
     * a cipher list. */
    if (!peer_ciphers) {
      log_info(LD_NET, "No ciphers on session");
      res = CIPHERS_ERR;
      goto done;
    }
    /* Now we need to see if there are any ciphers whose presence means we're
     * dealing with an updated Tor. */
    for (i = 0; i < sk_SSL_CIPHER_num(peer_ciphers); ++i) {
      const SSL_CIPHER *cipher = sk_SSL_CIPHER_value(peer_ciphers, i);
      const char *ciphername = SSL_CIPHER_get_name(cipher);
      if (strcmp(ciphername, TLS1_TXT_DHE_RSA_WITH_AES_128_SHA) &&
          strcmp(ciphername, TLS1_TXT_DHE_RSA_WITH_AES_256_SHA) &&
          strcmp(ciphername, SSL3_TXT_EDH_RSA_DES_192_CBC3_SHA) &&
          strcmp(ciphername, "(NONE)")) {
        log_debug(LD_NET, "Got a non-version-1 cipher called '%s'", ciphername);
        // return 1;
        goto v2_or_higher;
      }
    }
    res = CIPHERS_V1;
    goto done;
   v2_or_higher:
    {
      const uint16_t *v2_cipher = v2_cipher_list;
      for (i = 0; i < sk_SSL_CIPHER_num(peer_ciphers); ++i) {
        const SSL_CIPHER *cipher = sk_SSL_CIPHER_value(peer_ciphers, i);
        uint16_t id = SSL_CIPHER_get_id(cipher) & 0xffff;
        if (id == 0x00ff) /* extended renegotiation indicator. */
          continue;
        if (!id || id != *v2_cipher) {
          res = CIPHERS_UNRESTRICTED;
          goto dump_ciphers;
        }
        ++v2_cipher;
      }
      if (*v2_cipher != 0) {
        res = CIPHERS_UNRESTRICTED;
        goto dump_ciphers;
      }
      res = CIPHERS_V2;
    }
  
   dump_ciphers:
    {
      smartlist_t *elts = smartlist_new();
      char *s;
      for (i = 0; i < sk_SSL_CIPHER_num(peer_ciphers); ++i) {
        const SSL_CIPHER *cipher = sk_SSL_CIPHER_value(peer_ciphers, i);
        const char *ciphername = SSL_CIPHER_get_name(cipher);
        smartlist_add(elts, (char*)ciphername);
      }
      s = smartlist_join_strings(elts, ":", 0, NULL);
      log_debug(LD_NET, "Got a %s V2/V3 cipher list from %s.  It is: '%s'",
                (res == CIPHERS_V2) ? "fictitious" : "real", ADDR(tor_tls), s);
      tor_free(s);
      smartlist_free(elts);
    }
   done:
    if (tor_tls)
      return tor_tls->client_cipher_list_type = res;
  
    return res;
  }
  
  /** Return true iff the cipher list suggested by the client for <b>ssl</b> is
   * a list that indicates that the client knows how to do the v2 TLS connection
   * handshake. */
  STATIC int
  tor_tls_client_is_using_v2_ciphers(const SSL *ssl)
  {
    STACK_OF(SSL_CIPHER) *ciphers;
  #ifdef HAVE_SSL_GET_CLIENT_CIPHERS
    ciphers = SSL_get_client_ciphers(ssl);
  #else
    SSL_SESSION *session;
    if (!(session = SSL_get_session((SSL *)ssl))) {
      log_info(LD_NET, "No session on TLS?");
      return CIPHERS_ERR;
    }
    ciphers = session->ciphers;
  #endif
  
    return tor_tls_classify_client_ciphers(ssl, ciphers) >= CIPHERS_V2;
  }
  
  /** Invoked when we're accepting a connection on <b>ssl</b>, and the connection
   * changes state. We use this:
   * <ul><li>To alter the state of the handshake partway through, so we
   *         do not send or request extra certificates in v2 handshakes.</li>
   * <li>To detect renegotiation</li></ul>
   */
  STATIC void
  tor_tls_server_info_callback(const SSL *ssl, int type, int val)
  {
    tor_tls_t *tls;
    (void) val;
  
    IF_BUG_ONCE(ssl == NULL) {
      return; // LCOV_EXCL_LINE
    }
  
    tor_tls_debug_state_callback(ssl, type, val);
  
    if (type != SSL_CB_ACCEPT_LOOP)
      return;
  
    OSSL_HANDSHAKE_STATE ssl_state = SSL_get_state(ssl);
    if (! STATE_IS_SW_SERVER_HELLO(ssl_state))
      return;
    tls = tor_tls_get_by_ssl(ssl);
    if (tls) {
      /* Check whether we're watching for renegotiates.  If so, this is one! */
      if (tls->negotiated_callback)
        tls->got_renegotiate = 1;
      if (tls->server_handshake_count < 127) /*avoid any overflow possibility*/
        ++tls->server_handshake_count;
    } else {
      log_warn(LD_BUG, "Couldn't look up the tls for an SSL*. How odd!");
      return;
    }
  
    /* Now check the cipher list. */
    if (tor_tls_client_is_using_v2_ciphers(ssl)) {
      if (tls->wasV2Handshake)
        return; /* We already turned this stuff off for the first handshake;
                 * This is a renegotiation. */
  
      /* Yes, we're casting away the const from ssl.  This is very naughty of us.
       * Let's hope openssl doesn't notice! */
  
      /* Set SSL_MODE_NO_AUTO_CHAIN to keep from sending back any extra certs. */
      SSL_set_mode((SSL*) ssl, SSL_MODE_NO_AUTO_CHAIN);
      /* Don't send a hello request. */
      SSL_set_verify((SSL*) ssl, SSL_VERIFY_NONE, NULL);
  
      if (tls) {
        tls->wasV2Handshake = 1;
      } else {
        /* LCOV_EXCL_START this line is not reachable */
        log_warn(LD_BUG, "Couldn't look up the tls for an SSL*. How odd!");
        /* LCOV_EXCL_STOP */
      }
    }
  }
  
  /** Callback to get invoked on a server after we've read the list of ciphers
   * the client supports, but before we pick our own ciphersuite.
   *
   * We can't abuse an info_cb for this, since by the time one of the
   * client_hello info_cbs is called, we've already picked which ciphersuite to
   * use.
   *
   * Technically, this function is an abuse of this callback, since the point of
   * a session_secret_cb is to try to set up and/or verify a shared-secret for
   * authentication on the fly.  But as long as we return 0, we won't actually be
   * setting up a shared secret, and all will be fine.
   */
  STATIC int
  tor_tls_session_secret_cb(SSL *ssl, void *secret, int *secret_len,
                            STACK_OF(SSL_CIPHER) *peer_ciphers,
                            CONST_IF_OPENSSL_1_1_API SSL_CIPHER **cipher,
                            void *arg)
  {
    (void) secret;
    (void) secret_len;
    (void) peer_ciphers;
    (void) cipher;
    (void) arg;
  
    if (tor_tls_classify_client_ciphers(ssl, peer_ciphers) ==
         CIPHERS_UNRESTRICTED) {
      SSL_set_cipher_list(ssl, UNRESTRICTED_SERVER_CIPHER_LIST);
    }
  
    SSL_set_session_secret_cb(ssl, NULL, NULL);
  
    return 0;
  }
  static void
  tor_tls_setup_session_secret_cb(tor_tls_t *tls)
  {
    SSL_set_session_secret_cb(tls->ssl, tor_tls_session_secret_cb, NULL);
  }
  
  /** Create a new TLS object from a file descriptor, and a flag to
   * determine whether it is functioning as a server.
   */
  tor_tls_t *
  tor_tls_new(int sock, int isServer)
  {
    BIO *bio = NULL;
    tor_tls_t *result = tor_malloc_zero(sizeof(tor_tls_t));
    tor_tls_context_t *context = isServer ? server_tls_context :
      client_tls_context;
    result->magic = TOR_TLS_MAGIC;
  
    check_no_tls_errors();
    tor_assert(context); /* make sure somebody made it first */
    if (!(result->ssl = SSL_new(context->ctx))) {
      tls_log_errors(NULL, LOG_WARN, LD_NET, "creating SSL object");
      tor_free(result);
      goto err;
    }
  
  #ifdef SSL_set_tlsext_host_name
    /* Browsers use the TLS hostname extension, so we should too. */
    if (!isServer) {
      char *fake_hostname = crypto_random_hostname(4,25, "www.",".com");
      SSL_set_tlsext_host_name(result->ssl, fake_hostname);
      tor_free(fake_hostname);
    }
  #endif
  
    if (!SSL_set_cipher_list(result->ssl,
                       isServer ? SERVER_CIPHER_LIST : CLIENT_CIPHER_LIST)) {
      tls_log_errors(NULL, LOG_WARN, LD_NET, "setting ciphers");
  #ifdef SSL_set_tlsext_host_name
      SSL_set_tlsext_host_name(result->ssl, NULL);
  #endif
      SSL_free(result->ssl);
      tor_free(result);
      goto err;
    }
    result->socket = sock;
    bio = BIO_new_socket(sock, BIO_NOCLOSE);
    if (! bio) {
      tls_log_errors(NULL, LOG_WARN, LD_NET, "opening BIO");
  #ifdef SSL_set_tlsext_host_name
      SSL_set_tlsext_host_name(result->ssl, NULL);
  #endif
      SSL_free(result->ssl);
      tor_free(result);
      goto err;
    }
    {
      int set_worked =
        SSL_set_ex_data(result->ssl, tor_tls_object_ex_data_index, result);
      if (!set_worked) {
        log_warn(LD_BUG,
                 "Couldn't set the tls for an SSL*; connection will fail");
      }
    }
    SSL_set_bio(result->ssl, bio, bio);
    tor_tls_context_incref(context);
    result->context = context;
    result->state = TOR_TLS_ST_HANDSHAKE;
    result->isServer = isServer;
    result->wantwrite_n = 0;
    result->last_write_count = (unsigned long) BIO_number_written(bio);
    result->last_read_count = (unsigned long) BIO_number_read(bio);
    if (result->last_write_count || result->last_read_count) {
      log_warn(LD_NET, "Newly created BIO has read count %lu, write count %lu",
               result->last_read_count, result->last_write_count);
    }
    if (isServer) {
      SSL_set_info_callback(result->ssl, tor_tls_server_info_callback);
    } else {
      SSL_set_info_callback(result->ssl, tor_tls_debug_state_callback);
    }
  
    if (isServer)
      tor_tls_setup_session_secret_cb(result);
  
    goto done;
   err:
    result = NULL;
   done:
    /* Not expected to get called. */
    tls_log_errors(NULL, LOG_WARN, LD_NET, "creating tor_tls_t object");
    return result;
  }
  
  /** Make future log messages about <b>tls</b> display the address
   * <b>address</b>.
   */
  void
  tor_tls_set_logged_address(tor_tls_t *tls, const char *address)
  {
    tor_assert(tls);
    tor_free(tls->address);
    tls->address = tor_strdup(address);
  }
  
  /** Set <b>cb</b> to be called with argument <b>arg</b> whenever <b>tls</b>
   * next gets a client-side renegotiate in the middle of a read.  Do not
   * invoke this function until <em>after</em> initial handshaking is done!
   */
  void
  tor_tls_set_renegotiate_callback(tor_tls_t *tls,
                                   void (*cb)(tor_tls_t *, void *arg),
                                   void *arg)
  {
    tls->negotiated_callback = cb;
    tls->callback_arg = arg;
    tls->got_renegotiate = 0;
    if (cb) {
      SSL_set_info_callback(tls->ssl, tor_tls_server_info_callback);
    } else {
      SSL_set_info_callback(tls->ssl, tor_tls_debug_state_callback);
    }
  }
  
  /** If this version of openssl requires it, turn on renegotiation on
   * <b>tls</b>.
   */
  void
  tor_tls_unblock_renegotiation(tor_tls_t *tls)
  {
    /* Yes, we know what we are doing here.  No, we do not treat a renegotiation
     * as authenticating any earlier-received data. */
    SSL_set_options(tls->ssl,
                    SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION);
  }
  
  /** If this version of openssl supports it, turn off renegotiation on
   * <b>tls</b>.  (Our protocol never requires this for security, but it's nice
   * to use belt-and-suspenders here.)
   */
  void
  tor_tls_block_renegotiation(tor_tls_t *tls)
  {
  #ifdef SUPPORT_UNSAFE_RENEGOTIATION_FLAG
    tls->ssl->s3->flags &= ~SSL3_FLAGS_ALLOW_UNSAFE_LEGACY_RENEGOTIATION;
  #else
    (void) tls;
  #endif
  }
  
  /** Assert that the flags that allow legacy renegotiation are still set */
  void
  tor_tls_assert_renegotiation_unblocked(tor_tls_t *tls)
  {
  #if defined(SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION) && \
    SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION != 0
    long options = SSL_get_options(tls->ssl);
    tor_assert(0 != (options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION));
  #else
    (void) tls;
  #endif
  }
  
  /** Return whether this tls initiated the connect (client) or
   * received it (server). */
  int
  tor_tls_is_server(tor_tls_t *tls)
  {
    tor_assert(tls);
    return tls->isServer;
  }
  
  /** Release resources associated with a TLS object.  Does not close the
   * underlying file descriptor.
   */
  void
  tor_tls_free(tor_tls_t *tls)
  {
    if (!tls)
      return;
    tor_assert(tls->ssl);
    {
      size_t r,w;
      tor_tls_get_n_raw_bytes(tls,&r,&w); /* ensure written_by_tls is updated */
    }
  #ifdef SSL_set_tlsext_host_name
    SSL_set_tlsext_host_name(tls->ssl, NULL);
  #endif
    SSL_free(tls->ssl);
    tls->ssl = NULL;
    tls->negotiated_callback = NULL;
    if (tls->context)
      tor_tls_context_decref(tls->context);
    tor_free(tls->address);
    tls->magic = 0x99999999;
    tor_free(tls);
  }
  
  /** Underlying function for TLS reading.  Reads up to <b>len</b>
   * characters from <b>tls</b> into <b>cp</b>.  On success, returns the
   * number of characters read.  On failure, returns TOR_TLS_ERROR,
   * TOR_TLS_CLOSE, TOR_TLS_WANTREAD, or TOR_TLS_WANTWRITE.
   */
  MOCK_IMPL(int,
  tor_tls_read,(tor_tls_t *tls, char *cp, size_t len))
  {
    int r, err;
    tor_assert(tls);
    tor_assert(tls->ssl);
    tor_assert(tls->state == TOR_TLS_ST_OPEN);
    tor_assert(len<INT_MAX);
    r = SSL_read(tls->ssl, cp, (int)len);
    if (r > 0) {
      if (tls->got_renegotiate) {
        /* Renegotiation happened! */
        log_info(LD_NET, "Got a TLS renegotiation from %s", ADDR(tls));
        if (tls->negotiated_callback)
          tls->negotiated_callback(tls, tls->callback_arg);
        tls->got_renegotiate = 0;
      }
      return r;
    }
    err = tor_tls_get_error(tls, r, CATCH_ZERO, "reading", LOG_DEBUG, LD_NET);
    if (err == TOR_TLS_ZERORETURN_ || err == TOR_TLS_CLOSE) {
      log_debug(LD_NET,"read returned r=%d; TLS is closed",r);
      tls->state = TOR_TLS_ST_CLOSED;
      return TOR_TLS_CLOSE;
    } else {
      tor_assert(err != TOR_TLS_DONE);
      log_debug(LD_NET,"read returned r=%d, err=%d",r,err);
      return err;
    }
  }
  
  /** Total number of bytes that we've used TLS to send.  Used to track TLS
   * overhead. */
  STATIC uint64_t total_bytes_written_over_tls = 0;
  /** Total number of bytes that TLS has put on the network for us. Used to
   * track TLS overhead. */
  STATIC uint64_t total_bytes_written_by_tls = 0;
  
  /** Underlying function for TLS writing.  Write up to <b>n</b>
   * characters from <b>cp</b> onto <b>tls</b>.  On success, returns the
   * number of characters written.  On failure, returns TOR_TLS_ERROR,
   * TOR_TLS_WANTREAD, or TOR_TLS_WANTWRITE.
   */
  int
  tor_tls_write(tor_tls_t *tls, const char *cp, size_t n)
  {
    int r, err;
    tor_assert(tls);
    tor_assert(tls->ssl);
    tor_assert(tls->state == TOR_TLS_ST_OPEN);
    tor_assert(n < INT_MAX);
    if (n == 0)
      return 0;
    if (tls->wantwrite_n) {
      /* if WANTWRITE last time, we must use the _same_ n as before */
      tor_assert(n >= tls->wantwrite_n);
      log_debug(LD_NET,"resuming pending-write, (%d to flush, reusing %d)",
                (int)n, (int)tls->wantwrite_n);
      n = tls->wantwrite_n;
      tls->wantwrite_n = 0;
    }
    r = SSL_write(tls->ssl, cp, (int)n);
    err = tor_tls_get_error(tls, r, 0, "writing", LOG_INFO, LD_NET);
    if (err == TOR_TLS_DONE) {
      total_bytes_written_over_tls += r;
      return r;
    }
    if (err == TOR_TLS_WANTWRITE || err == TOR_TLS_WANTREAD) {
      tls->wantwrite_n = n;
    }
    return err;
  }
  
  /** Perform initial handshake on <b>tls</b>.  When finished, returns
   * TOR_TLS_DONE.  On failure, returns TOR_TLS_ERROR, TOR_TLS_WANTREAD,
   * or TOR_TLS_WANTWRITE.
   */
  int
  tor_tls_handshake(tor_tls_t *tls)
  {
    int r;
    tor_assert(tls);
    tor_assert(tls->ssl);
    tor_assert(tls->state == TOR_TLS_ST_HANDSHAKE);
  
    check_no_tls_errors();
  
    OSSL_HANDSHAKE_STATE oldstate = SSL_get_state(tls->ssl);
  
    if (tls->isServer) {
      log_debug(LD_HANDSHAKE, "About to call SSL_accept on %p (%s)", tls,
                SSL_state_string_long(tls->ssl));
      r = SSL_accept(tls->ssl);
    } else {
      log_debug(LD_HANDSHAKE, "About to call SSL_connect on %p (%s)", tls,
                SSL_state_string_long(tls->ssl));
      r = SSL_connect(tls->ssl);
    }
  
    OSSL_HANDSHAKE_STATE newstate = SSL_get_state(tls->ssl);
  
    if (oldstate != newstate)
      log_debug(LD_HANDSHAKE, "After call, %p was in state %s",
                tls, SSL_state_string_long(tls->ssl));
    /* We need to call this here and not earlier, since OpenSSL has a penchant
     * for clearing its flags when you say accept or connect. */
    tor_tls_unblock_renegotiation(tls);
    r = tor_tls_get_error(tls,r,0, "handshaking", LOG_INFO, LD_HANDSHAKE);
    if (ERR_peek_error() != 0) {
      tls_log_errors(tls, tls->isServer ? LOG_INFO : LOG_WARN, LD_HANDSHAKE,
                     "handshaking");
      return TOR_TLS_ERROR_MISC;
    }
    if (r == TOR_TLS_DONE) {
      tls->state = TOR_TLS_ST_OPEN;
      return tor_tls_finish_handshake(tls);
    }
    return r;
  }
  
  /** Perform the final part of the intial TLS handshake on <b>tls</b>.  This
   * should be called for the first handshake only: it determines whether the v1
   * or the v2 handshake was used, and adjusts things for the renegotiation
   * handshake as appropriate.
   *
   * tor_tls_handshake() calls this on its own; you only need to call this if
   * bufferevent is doing the handshake for you.
   */
  int
  tor_tls_finish_handshake(tor_tls_t *tls)
  {
    int r = TOR_TLS_DONE;
    check_no_tls_errors();
    if (tls->isServer) {
      SSL_set_info_callback(tls->ssl, NULL);
      SSL_set_verify(tls->ssl, SSL_VERIFY_PEER, always_accept_verify_cb);
      SSL_clear_mode(tls->ssl, SSL_MODE_NO_AUTO_CHAIN);
      if (tor_tls_client_is_using_v2_ciphers(tls->ssl)) {
        /* This check is redundant, but back when we did it in the callback,
         * we might have not been able to look up the tor_tls_t if the code
         * was buggy.  Fixing that. */
        if (!tls->wasV2Handshake) {
          log_warn(LD_BUG, "For some reason, wasV2Handshake didn't"
                   " get set. Fixing that.");
        }
        tls->wasV2Handshake = 1;
        log_debug(LD_HANDSHAKE, "Completed V2 TLS handshake with client; waiting"
                  " for renegotiation.");
      } else {
        tls->wasV2Handshake = 0;
      }
    } else {
      /* Client-side */
      tls->wasV2Handshake = 1;
      /* XXXX this can move, probably? -NM */
      if (SSL_set_cipher_list(tls->ssl, SERVER_CIPHER_LIST) == 0) {
        tls_log_errors(NULL, LOG_WARN, LD_HANDSHAKE, "re-setting ciphers");
        r = TOR_TLS_ERROR_MISC;
      }
    }
    tls_log_errors(NULL, LOG_WARN, LD_NET, "finishing the handshake");
    return r;
  }
  
  /** Shut down an open tls connection <b>tls</b>.  When finished, returns
   * TOR_TLS_DONE.  On failure, returns TOR_TLS_ERROR, TOR_TLS_WANTREAD,
   * or TOR_TLS_WANTWRITE.
   */
  int
  tor_tls_shutdown(tor_tls_t *tls)
  {
    int r, err;
    char buf[128];
    tor_assert(tls);
    tor_assert(tls->ssl);
    check_no_tls_errors();
  
    while (1) {
      if (tls->state == TOR_TLS_ST_SENTCLOSE) {
        /* If we've already called shutdown once to send a close message,
         * we read until the other side has closed too.
         */
        do {
          r = SSL_read(tls->ssl, buf, 128);
        } while (r>0);
        err = tor_tls_get_error(tls, r, CATCH_ZERO, "reading to shut down",
                                LOG_INFO, LD_NET);
        if (err == TOR_TLS_ZERORETURN_) {
          tls->state = TOR_TLS_ST_GOTCLOSE;
          /* fall through... */
        } else {
          return err;
        }
      }
  
      r = SSL_shutdown(tls->ssl);
      if (r == 1) {
        /* If shutdown returns 1, the connection is entirely closed. */
        tls->state = TOR_TLS_ST_CLOSED;
        return TOR_TLS_DONE;
      }
      err = tor_tls_get_error(tls, r, CATCH_SYSCALL|CATCH_ZERO, "shutting down",
                              LOG_INFO, LD_NET);
      if (err == TOR_TLS_SYSCALL_) {
        /* The underlying TCP connection closed while we were shutting down. */
        tls->state = TOR_TLS_ST_CLOSED;
        return TOR_TLS_DONE;
      } else if (err == TOR_TLS_ZERORETURN_) {
        /* The TLS connection says that it sent a shutdown record, but
         * isn't done shutting down yet.  Make sure that this hasn't
         * happened before, then go back to the start of the function
         * and try to read.
         */
        if (tls->state == TOR_TLS_ST_GOTCLOSE ||
           tls->state == TOR_TLS_ST_SENTCLOSE) {
          log_warn(LD_NET,
              "TLS returned \"half-closed\" value while already half-closed");
          return TOR_TLS_ERROR_MISC;
        }
        tls->state = TOR_TLS_ST_SENTCLOSE;
        /* fall through ... */
      } else {
        return err;
      }
    } /* end loop */
  }
  
  /** Return true iff this TLS connection is authenticated.
   */
  int
  tor_tls_peer_has_cert(tor_tls_t *tls)
  {
    X509 *cert;
    cert = SSL_get_peer_certificate(tls->ssl);
    tls_log_errors(tls, LOG_WARN, LD_HANDSHAKE, "getting peer certificate");
    if (!cert)
      return 0;
    X509_free(cert);
    return 1;
  }
  
  /** Return a newly allocated copy of the peer certificate, or NULL if there
   * isn't one. */
  MOCK_IMPL(tor_x509_cert_t *,
  tor_tls_get_peer_cert,(tor_tls_t *tls))
  {
    X509 *cert;
    cert = SSL_get_peer_certificate(tls->ssl);
    tls_log_errors(tls, LOG_WARN, LD_HANDSHAKE, "getting peer certificate");
    if (!cert)
      return NULL;
    return tor_x509_cert_new(cert);
  }
  
  /** Return a newly allocated copy of the cerficate we used on the connection,
   * or NULL if somehow we didn't use one. */
  MOCK_IMPL(tor_x509_cert_t *,
  tor_tls_get_own_cert,(tor_tls_t *tls))
  {
    X509 *cert = SSL_get_certificate(tls->ssl);
    tls_log_errors(tls, LOG_WARN, LD_HANDSHAKE,
                   "getting own-connection certificate");
    if (!cert)
      return NULL;
    /* Fun inconsistency: SSL_get_peer_certificate increments the reference
     * count, but SSL_get_certificate does not. */
    X509 *duplicate = X509_dup(cert);
    if (BUG(duplicate == NULL))
      return NULL;
    return tor_x509_cert_new(duplicate);
  }
  
  /** Warn that a certificate lifetime extends through a certain range. */
  static void
  log_cert_lifetime(int severity, const X509 *cert, const char *problem,
                    time_t now)
  {
    BIO *bio = NULL;
    BUF_MEM *buf;
    char *s1=NULL, *s2=NULL;
    char mytime[33];
    struct tm tm;
    size_t n;
  
    if (problem)
      tor_log(severity, LD_GENERAL,
          "Certificate %s. Either their clock is set wrong, or your clock "
          "is wrong.",
             problem);
  
    if (!(bio = BIO_new(BIO_s_mem()))) {
      log_warn(LD_GENERAL, "Couldn't allocate BIO!"); goto end;
    }
    if (!(ASN1_TIME_print(bio, X509_get_notBefore_const(cert)))) {
      tls_log_errors(NULL, LOG_WARN, LD_NET, "printing certificate lifetime");
      goto end;
    }
    BIO_get_mem_ptr(bio, &buf);
    s1 = tor_strndup(buf->data, buf->length);
  
    (void)BIO_reset(bio);
    if (!(ASN1_TIME_print(bio, X509_get_notAfter_const(cert)))) {
      tls_log_errors(NULL, LOG_WARN, LD_NET, "printing certificate lifetime");
      goto end;
    }
    BIO_get_mem_ptr(bio, &buf);
    s2 = tor_strndup(buf->data, buf->length);
  
    n = strftime(mytime, 32, "%b %d %H:%M:%S %Y UTC", tor_gmtime_r(&now, &tm));
    if (n > 0) {
      tor_log(severity, LD_GENERAL,
          "(certificate lifetime runs from %s through %s. Your time is %s.)",
          s1,s2,mytime);
    } else {
      tor_log(severity, LD_GENERAL,
          "(certificate lifetime runs from %s through %s. "
          "Couldn't get your time.)",
          s1, s2);
    }
  
   end:
    /* Not expected to get invoked */
    tls_log_errors(NULL, LOG_WARN, LD_NET, "getting certificate lifetime");
    if (bio)
      BIO_free(bio);
    tor_free(s1);
    tor_free(s2);
  }
  
  /** Helper function: try to extract a link certificate and an identity
   * certificate from <b>tls</b>, and store them in *<b>cert_out</b> and
   * *<b>id_cert_out</b> respectively.  Log all messages at level
   * <b>severity</b>.
   *
   * Note that a reference is added to cert_out, so it needs to be
   * freed. id_cert_out doesn't. */
  MOCK_IMPL(STATIC void,
  try_to_extract_certs_from_tls,(int severity, tor_tls_t *tls,
                                 X509 **cert_out, X509 **id_cert_out))
  {
    X509 *cert = NULL, *id_cert = NULL;
    STACK_OF(X509) *chain = NULL;
    int num_in_chain, i;
    *cert_out = *id_cert_out = NULL;
    if (!(cert = SSL_get_peer_certificate(tls->ssl)))
      return;
    *cert_out = cert;
    if (!(chain = SSL_get_peer_cert_chain(tls->ssl)))
      return;
    num_in_chain = sk_X509_num(chain);
    /* 1 means we're receiving (server-side), and it's just the id_cert.
     * 2 means we're connecting (client-side), and it's both the link
     * cert and the id_cert.
     */
    if (num_in_chain < 1) {
      log_fn(severity,LD_PROTOCOL,
             "Unexpected number of certificates in chain (%d)",
             num_in_chain);
      return;
    }
    for (i=0; i<num_in_chain; ++i) {
      id_cert = sk_X509_value(chain, i);
      if (X509_cmp(id_cert, cert) != 0)
        break;
    }
    *id_cert_out = id_cert;
  }
  
  /** If the provided tls connection is authenticated and has a
   * certificate chain that is currently valid and signed, then set
   * *<b>identity_key</b> to the identity certificate's key and return
   * 0.  Else, return -1 and log complaints with log-level <b>severity</b>.
   */
  int
  tor_tls_verify(int severity, tor_tls_t *tls, crypto_pk_t **identity_key)
  {
    X509 *cert = NULL, *id_cert = NULL;
    EVP_PKEY *id_pkey = NULL;
    RSA *rsa;
    int r = -1;
  
    check_no_tls_errors();
    *identity_key = NULL;
  
    try_to_extract_certs_from_tls(severity, tls, &cert, &id_cert);
    if (!cert)
      goto done;
    if (!id_cert) {
      log_fn(severity,LD_PROTOCOL,"No distinct identity certificate found");
      goto done;
    }
    tls_log_errors(tls, severity, LD_HANDSHAKE, "before verifying certificate");
  
    if (!(id_pkey = X509_get_pubkey(id_cert)) ||
        X509_verify(cert, id_pkey) <= 0) {
      log_fn(severity,LD_PROTOCOL,"X509_verify on cert and pkey returned <= 0");
      tls_log_errors(tls, severity, LD_HANDSHAKE, "verifying certificate");
      goto done;
    }
  
    rsa = EVP_PKEY_get1_RSA(id_pkey);
    if (!rsa)
      goto done;
    *identity_key = crypto_new_pk_from_rsa_(rsa);
  
    r = 0;
  
   done:
    if (cert)
      X509_free(cert);
    if (id_pkey)
      EVP_PKEY_free(id_pkey);
  
    /* This should never get invoked, but let's make sure in case OpenSSL
     * acts unexpectedly. */
    tls_log_errors(tls, LOG_WARN, LD_HANDSHAKE, "finishing tor_tls_verify");
  
    return r;
  }
  
  /** Check whether the certificate set on the connection <b>tls</b> is expired
   * give or take <b>past_tolerance</b> seconds, or not-yet-valid give or take
   * <b>future_tolerance</b> seconds. Return 0 for valid, -1 for failure.
   *
   * NOTE: you should call tor_tls_verify before tor_tls_check_lifetime.
   */
  int
  tor_tls_check_lifetime(int severity, tor_tls_t *tls,
                         time_t now,
                         int past_tolerance, int future_tolerance)
  {
    X509 *cert;
    int r = -1;
  
    if (!(cert = SSL_get_peer_certificate(tls->ssl)))
      goto done;
  
    if (check_cert_lifetime_internal(severity, cert, now,
                                     past_tolerance, future_tolerance) < 0)
      goto done;
  
    r = 0;
   done:
    if (cert)
      X509_free(cert);
    /* Not expected to get invoked */
    tls_log_errors(tls, LOG_WARN, LD_NET, "checking certificate lifetime");
  
    return r;
  }
  
  /** Helper: check whether <b>cert</b> is expired give or take
   * <b>past_tolerance</b> seconds, or not-yet-valid give or take
   * <b>future_tolerance</b> seconds.  (Relative to the current time
   * <b>now</b>.)  If it is live, return 0.  If it is not live, log a message
   * and return -1. */
  static int
  check_cert_lifetime_internal(int severity, const X509 *cert,
                               time_t now,
                               int past_tolerance, int future_tolerance)
  {
    time_t t;
  
    t = now + future_tolerance;
    if (X509_cmp_time(X509_get_notBefore_const(cert), &t) > 0) {
      log_cert_lifetime(severity, cert, "not yet valid", now);
      return -1;
    }
    t = now - past_tolerance;
    if (X509_cmp_time(X509_get_notAfter_const(cert), &t) < 0) {
      log_cert_lifetime(severity, cert, "already expired", now);
      return -1;
    }
  
    return 0;
  }
  
  #ifdef TOR_UNIT_TESTS
  /* Testing only: return a new x509 cert with the same contents as <b>inp</b>,
     but with the expiration time <b>new_expiration_time</b>, signed with
     <b>signing_key</b>. */
  STATIC tor_x509_cert_t *
  tor_x509_cert_replace_expiration(const tor_x509_cert_t *inp,
                                   time_t new_expiration_time,
                                   crypto_pk_t *signing_key)
  {
    X509 *newc = X509_dup(inp->cert);
    X509_time_adj(X509_get_notAfter(newc), 0, &new_expiration_time);
    EVP_PKEY *pk = crypto_pk_get_evp_pkey_(signing_key, 1);
    tor_assert(X509_sign(newc, pk, EVP_sha256()));
    EVP_PKEY_free(pk);
    return tor_x509_cert_new(newc);
  }
  #endif
  
  /** Return the number of bytes available for reading from <b>tls</b>.
   */
  int
  tor_tls_get_pending_bytes(tor_tls_t *tls)
  {
    tor_assert(tls);
    return SSL_pending(tls->ssl);
  }
  
  /** If <b>tls</b> requires that the next write be of a particular size,
   * return that size.  Otherwise, return 0. */
  size_t
  tor_tls_get_forced_write_size(tor_tls_t *tls)
  {
    return tls->wantwrite_n;
  }
  
  /** Sets n_read and n_written to the number of bytes read and written,
   * respectively, on the raw socket used by <b>tls</b> since the last time this
   * function was called on <b>tls</b>. */
  void
  tor_tls_get_n_raw_bytes(tor_tls_t *tls, size_t *n_read, size_t *n_written)
  {
    BIO *wbio, *tmpbio;
    unsigned long r, w;
    r = (unsigned long) BIO_number_read(SSL_get_rbio(tls->ssl));
    /* We want the number of bytes actually for real written.  Unfortunately,
     * sometimes OpenSSL replaces the wbio on tls->ssl with a buffering bio,
     * which makes the answer turn out wrong.  Let's cope with that.  Note
     * that this approach will fail if we ever replace tls->ssl's BIOs with
     * buffering bios for reasons of our own.  As an alternative, we could
     * save the original BIO for  tls->ssl in the tor_tls_t structure, but
     * that would be tempting fate. */
    wbio = SSL_get_wbio(tls->ssl);
  #if OPENSSL_VERSION_NUMBER >= OPENSSL_VER(1,1,0,0,5)
    /* BIO structure is opaque as of OpenSSL 1.1.0-pre5-dev.  Again, not
     * supposed to use this form of the version macro, but the OpenSSL developers
     * introduced major API changes in the pre-release stage.
     */
    if (BIO_method_type(wbio) == BIO_TYPE_BUFFER &&
          (tmpbio = BIO_next(wbio)) != NULL)
      wbio = tmpbio;
  #else
    if (wbio->method == BIO_f_buffer() && (tmpbio = BIO_next(wbio)) != NULL)
      wbio = tmpbio;
  #endif
    w = (unsigned long) BIO_number_written(wbio);
  
    /* We are ok with letting these unsigned ints go "negative" here:
     * If we wrapped around, this should still give us the right answer, unless
     * we wrapped around by more than ULONG_MAX since the last time we called
     * this function.
     */
    *n_read = (size_t)(r - tls->last_read_count);
    *n_written = (size_t)(w - tls->last_write_count);
    if (*n_read > INT_MAX || *n_written > INT_MAX) {
      log_warn(LD_BUG, "Preposterously large value in tor_tls_get_n_raw_bytes. "
               "r=%lu, last_read=%lu, w=%lu, last_written=%lu",
               r, tls->last_read_count, w, tls->last_write_count);
    }
    total_bytes_written_by_tls += *n_written;
    tls->last_read_count = r;
    tls->last_write_count = w;
  }
  
  /** Return a ratio of the bytes that TLS has sent to the bytes that we've told
   * it to send. Used to track whether our TLS records are getting too tiny. */
  MOCK_IMPL(double,
  tls_get_write_overhead_ratio,(void))
  {
    if (total_bytes_written_over_tls == 0)
      return 1.0;
  
    return U64_TO_DBL(total_bytes_written_by_tls) /
      U64_TO_DBL(total_bytes_written_over_tls);
  }
  
  /** Implement check_no_tls_errors: If there are any pending OpenSSL
   * errors, log an error message. */
  void
  check_no_tls_errors_(const char *fname, int line)
  {
    if (ERR_peek_error() == 0)
      return;
    log_warn(LD_CRYPTO, "Unhandled OpenSSL errors found at %s:%d: ",
        tor_fix_source_file(fname), line);
    tls_log_errors(NULL, LOG_WARN, LD_NET, NULL);
  }
  
  /** Return true iff the initial TLS connection at <b>tls</b> did not use a v2
   * TLS handshake. Output is undefined if the handshake isn't finished. */
  int
  tor_tls_used_v1_handshake(tor_tls_t *tls)
  {
    return ! tls->wasV2Handshake;
  }
  
  /** Return the number of server handshakes that we've noticed doing on
   * <b>tls</b>. */
  int
  tor_tls_get_num_server_handshakes(tor_tls_t *tls)
  {
    return tls->server_handshake_count;
  }
  
  /** Return true iff the server TLS connection <b>tls</b> got the renegotiation
   * request it was waiting for. */
  int
  tor_tls_server_got_renegotiate(tor_tls_t *tls)
  {
    return tls->got_renegotiate;
  }
  
  #ifndef HAVE_SSL_GET_CLIENT_RANDOM
  static size_t
  SSL_get_client_random(SSL *s, uint8_t *out, size_t len)
  {
    if (len == 0)
      return SSL3_RANDOM_SIZE;
    tor_assert(len == SSL3_RANDOM_SIZE);
    tor_assert(s->s3);
    memcpy(out, s->s3->client_random, len);
    return len;
  }
  #endif
  
  #ifndef HAVE_SSL_GET_SERVER_RANDOM
  static size_t
  SSL_get_server_random(SSL *s, uint8_t *out, size_t len)
  {
    if (len == 0)
      return SSL3_RANDOM_SIZE;
    tor_assert(len == SSL3_RANDOM_SIZE);
    tor_assert(s->s3);
    memcpy(out, s->s3->server_random, len);
    return len;
  }
  #endif
  
  #ifndef HAVE_SSL_SESSION_GET_MASTER_KEY
  STATIC size_t
  SSL_SESSION_get_master_key(SSL_SESSION *s, uint8_t *out, size_t len)
  {
    tor_assert(s);
    if (len == 0)
      return s->master_key_length;
    tor_assert(len == (size_t)s->master_key_length);
    tor_assert(out);
    memcpy(out, s->master_key, len);
    return len;
  }
  #endif
  
  /** Set the DIGEST256_LEN buffer at <b>secrets_out</b> to the value used in
   * the v3 handshake to prove that the client knows the TLS secrets for the
   * connection <b>tls</b>.  Return 0 on success, -1 on failure.
   */
  MOCK_IMPL(int,
  tor_tls_get_tlssecrets,(tor_tls_t *tls, uint8_t *secrets_out))
  {
  #define TLSSECRET_MAGIC "Tor V3 handshake TLS cross-certification"
    uint8_t buf[128];
    size_t len;
    tor_assert(tls);
  
    SSL *const ssl = tls->ssl;
    SSL_SESSION *const session = SSL_get_session(ssl);
  
    tor_assert(ssl);
    tor_assert(session);
  
    const size_t server_random_len = SSL_get_server_random(ssl, NULL, 0);
    const size_t client_random_len = SSL_get_client_random(ssl, NULL, 0);
    const size_t master_key_len = SSL_SESSION_get_master_key(session, NULL, 0);
  
    tor_assert(server_random_len);
    tor_assert(client_random_len);
    tor_assert(master_key_len);
  
    len = client_random_len + server_random_len + strlen(TLSSECRET_MAGIC) + 1;
    tor_assert(len <= sizeof(buf));
  
    {
      size_t r = SSL_get_client_random(ssl, buf, client_random_len);
      tor_assert(r == client_random_len);
    }
  
    {
      size_t r = SSL_get_server_random(ssl,
                                       buf+client_random_len,
                                       server_random_len);
      tor_assert(r == server_random_len);
    }
  
    uint8_t *master_key = tor_malloc_zero(master_key_len);
    {
      size_t r = SSL_SESSION_get_master_key(session, master_key, master_key_len);
      tor_assert(r == master_key_len);
    }
  
    uint8_t *nextbuf = buf + client_random_len + server_random_len;
    memcpy(nextbuf, TLSSECRET_MAGIC, strlen(TLSSECRET_MAGIC) + 1);
  
    /*
      The value is an HMAC, using the TLS master key as the HMAC key, of
      client_random | server_random | TLSSECRET_MAGIC
    */
    crypto_hmac_sha256((char*)secrets_out,
                       (char*)master_key,
                       master_key_len,
                       (char*)buf, len);
    memwipe(buf, 0, sizeof(buf));
    memwipe(master_key, 0, master_key_len);
    tor_free(master_key);
  
    return 0;
  }
  
  /** Using the RFC5705 key material exporting construction, and the
   * provided <b>context</b> (<b>context_len</b> bytes long) and
   * <b>label</b> (a NUL-terminated string), compute a 32-byte secret in
   * <b>secrets_out</b> that only the parties to this TLS session can
   * compute.  Return 0 on success and -1 on failure.
   */
  MOCK_IMPL(int,
  tor_tls_export_key_material,(tor_tls_t *tls, uint8_t *secrets_out,
                               const uint8_t *context,
                               size_t context_len,
                               const char *label))
  {
    tor_assert(tls);
    tor_assert(tls->ssl);
  
    int r = SSL_export_keying_material(tls->ssl,
                                       secrets_out, DIGEST256_LEN,
                                       label, strlen(label),
                                       context, context_len, 1);
    return (r == 1) ? 0 : -1;
  }
  
  /** Examine the amount of memory used and available for buffers in <b>tls</b>.
   * Set *<b>rbuf_capacity</b> to the amount of storage allocated for the read
   * buffer and *<b>rbuf_bytes</b> to the amount actually used.
   * Set *<b>wbuf_capacity</b> to the amount of storage allocated for the write
   * buffer and *<b>wbuf_bytes</b> to the amount actually used.
   *
   * Return 0 on success, -1 on failure.*/
  int
  tor_tls_get_buffer_sizes(tor_tls_t *tls,
                           size_t *rbuf_capacity, size_t *rbuf_bytes,
                           size_t *wbuf_capacity, size_t *wbuf_bytes)
  {
  #if OPENSSL_VERSION_NUMBER >= OPENSSL_V_SERIES(1,1,0)
    (void)tls;
    (void)rbuf_capacity;
    (void)rbuf_bytes;
    (void)wbuf_capacity;
    (void)wbuf_bytes;
  
    return -1;
  #else
    if (tls->ssl->s3->rbuf.buf)
      *rbuf_capacity = tls->ssl->s3->rbuf.len;
    else
      *rbuf_capacity = 0;
    if (tls->ssl->s3->wbuf.buf)
      *wbuf_capacity = tls->ssl->s3->wbuf.len;
    else
      *wbuf_capacity = 0;
    *rbuf_bytes = tls->ssl->s3->rbuf.left;
    *wbuf_bytes = tls->ssl->s3->wbuf.left;
    return 0;
  #endif
  }
  
  /** Check whether the ECC group requested is supported by the current OpenSSL
   * library instance.  Return 1 if the group is supported, and 0 if not.
   */
  int
  evaluate_ecgroup_for_tls(const char *ecgroup)
  {
    EC_KEY *ec_key;
    int nid;
    int ret;
  
    if (!ecgroup)
      nid = NID_tor_default_ecdhe_group;
    else if (!strcasecmp(ecgroup, "P256"))
      nid = NID_X9_62_prime256v1;
    else if (!strcasecmp(ecgroup, "P224"))
      nid = NID_secp224r1;
    else
      return 0;
  
    ec_key = EC_KEY_new_by_curve_name(nid);
    ret = (ec_key != NULL);
    EC_KEY_free(ec_key);
  
    return ret;
  }
  
  