Merge branch 'nss_squashed' into nss_merge

1 files changed, 1708 insertions, 0 deletions

diff --git a/src/lib/tls/tortls_openssl.c b/src/lib/tls/tortls_openssl.c
new file mode 100644
index 0000000000..ab9712962b
--- /dev/null
+++ b/src/lib/tls/tortls_openssl.c
@@ -0,0 +1,1708 @@
+/* Copyright (c) 2003, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, 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
+#define TOR_X509_PRIVATE
+
+#ifdef _WIN32
+  /* We need to include these here, or else the dtls1.h header will include
+   * <winsock.h> and mess things up, in at least some openssl versions. */
+  #include <winsock2.h>
+  #include <ws2tcpip.h>
+#endif
+
+#include "lib/crypt_ops/crypto_cipher.h"
+#include "lib/crypt_ops/crypto_rand.h"
+#include "lib/crypt_ops/crypto_dh.h"
+#include "lib/crypt_ops/crypto_util.h"
+#include "lib/crypt_ops/compat_openssl.h"
+#include "lib/tls/x509.h"
+#include "lib/tls/x509_internal.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>
+
+#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)
+
+#include "lib/tls/tortls.h"
+#include "lib/tls/tortls_st.h"
+#include "lib/tls/tortls_internal.h"
+#include "lib/log/log.h"
+#include "lib/log/util_bug.h"
+#include "lib/container/smartlist.h"
+#include "lib/string/compat_string.h"
+#include "lib/string/printf.h"
+#include "lib/net/socket.h"
+#include "lib/intmath/cmp.h"
+#include "lib/ctime/di_ops.h"
+#include "lib/encoding/time_fmt.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "lib/arch/bytes.h"
+
+/* Copied from or.h */
+#define LEGAL_NICKNAME_CHARACTERS \
+  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+
+#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 /* OPENSSL_VERSION_NUMBER <  OPENSSL_V(1,0,0,'f') */
+
+/* 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. */
+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. */
+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;
+}
+
+/** 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.
+ */
+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);
+  }
+}
+
+#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>.
+ */
+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.
+ */
+void
+tor_tls_init(void)
+{
+  check_no_tls_errors();
+
+  if (!tls_library_is_initialized) {
+#ifdef OPENSSL_1_1_API
+    OPENSSL_init_ssl(OPENSSL_INIT_LOAD_SSL_STRINGS, NULL);
+#else
+    SSL_library_init();
+    SSL_load_error_strings();
+#endif
+
+#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 /* (SIZEOF_VOID_P >= 8 &&                              ... */
+
+    tor_tls_allocate_tor_tls_object_ex_data_index();
+
+    tls_library_is_initialized = 1;
+  }
+}
+
+/** 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.
+ */
+int
+always_accept_verify_cb(int preverify_ok,
+                        X509_STORE_CTX *x509_ctx)
+{
+  (void) preverify_ok;
+  (void) x509_ctx;
+  return 1;
+}
+
+/** List of ciphers that servers should select from when the client might be
+ * claiming extra unsupported ciphers in order to avoid fingerprinting.  */
+static const char SERVER_CIPHER_LIST[] =
+#ifdef  TLS1_3_TXT_AES_128_GCM_SHA256
+  /* This one can never actually get selected, since if the client lists it,
+   * we will assume that the client is honest, and not use this list.
+   * Nonetheless we list it if it's available, so that the server doesn't
+   * conclude that it has no valid ciphers if it's running with TLS1.3.
+   */
+  TLS1_3_TXT_AES_128_GCM_SHA256 ":"
+#endif
+  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[] =
+  /* Here are the TLS 1.3 ciphers we like, in the order we prefer. */
+#ifdef TLS1_3_TXT_AES_256_GCM_SHA384
+  TLS1_3_TXT_AES_256_GCM_SHA384 ":"
+#endif
+#ifdef TLS1_3_TXT_CHACHA20_POLY1305_SHA256
+  TLS1_3_TXT_CHACHA20_POLY1305_SHA256 ":"
+#endif
+#ifdef TLS1_3_TXT_AES_128_GCM_SHA256
+  TLS1_3_TXT_AES_128_GCM_SHA256 ":"
+#endif
+#ifdef TLS1_3_TXT_AES_128_CCM_SHA256
+  TLS1_3_TXT_AES_128_CCM_SHA256 ":"
+#endif
+
+  /* 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
+
+/** 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))
+{
+  tor_x509_cert_t *peer = tor_tls_get_peer_cert((tor_tls_t *)tls);
+  if (!peer)
+    return 0;
+
+  X509 *peercert = peer->cert;
+  EVP_PKEY *link_key = NULL, *cert_key = NULL;
+  int result;
+
+  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;
+
+  tor_x509_cert_free(peer);
+  if (link_key)
+    EVP_PKEY_free(link_key);
+  if (cert_key)
+    EVP_PKEY_free(cert_key);
+
+  return result;
+}
+
+void
+tor_tls_context_impl_free_(struct ssl_ctx_st *ctx)
+{
+  if (!ctx)
+    return;
+  SSL_CTX_free(ctx);
+}
+
+/** The group we should use for ecdhe when none was selected. */
+#define  NID_tor_default_ecdhe_group NID_X9_62_prime256v1
+
+/** 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.
+ */
+tor_tls_context_t *
+tor_tls_context_new(crypto_pk_t *identity, unsigned int key_lifetime,
+                    unsigned flags, int is_client)
+{
+  EVP_PKEY *pkey = NULL;
+  tor_tls_context_t *result = NULL;
+
+  tor_tls_init();
+
+  result = tor_malloc_zero(sizeof(tor_tls_context_t));
+  result->refcnt = 1;
+
+  if (! is_client) {
+    if (tor_tls_context_init_certificates(result, identity, key_lifetime,
+                                          flags) < 0) {
+      goto error;
+    }
+  }
+
+#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 /* 0 */
+
+  /* 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 /* defined(HAVE_TLS_METHOD) */
+  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);
+  }
+
+  /* Don't actually allow compression; it uses RAM and time, it makes TLS
+   * vulnerable to CRIME-style attacks, and most of the data we transmit over
+   * TLS is encrypted (and therefore uncompressible) anyway. */
+#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
+  if (result->ctx->comp_methods)
+    result->ctx->comp_methods = NULL;
+#endif
+#endif /* OPENSSL_VERSION_NUMBER < OPENSSL_V_SERIES(1,1,0) */
+
+#ifdef SSL_MODE_RELEASE_BUFFERS
+  SSL_CTX_set_mode(result->ctx, SSL_MODE_RELEASE_BUFFERS);
+#endif
+  if (! is_client) {
+    if (result->my_link_cert &&
+        !SSL_CTX_use_certificate(result->ctx,
+                                 result->my_link_cert->cert)) {
+      goto error;
+    }
+    if (result->my_id_cert) {
+      X509_STORE *s = SSL_CTX_get_cert_store(result->ctx);
+      tor_assert(s);
+      X509_STORE_add_cert(s, result->my_id_cert->cert);
+    }
+  }
+  SSL_CTX_set_session_cache_mode(result->ctx, SSL_SESS_CACHE_OFF);
+  if (!is_client) {
+    tor_assert(result->link_key);
+    if (!(pkey = crypto_pk_get_openssl_evp_pkey_(result->link_key,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;
+  }
+
+  {
+    DH *dh = crypto_dh_new_openssl_tls();
+    tor_assert(dh);
+    SSL_CTX_set_tmp_dh(result->ctx, dh);
+    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);
+
+  return result;
+
+ error:
+  tls_log_errors(NULL, LOG_WARN, LD_NET, "creating TLS context");
+  if (pkey)
+    EVP_PKEY_free(pkey);
+  if (result)
+    tor_tls_context_decref(result);
+  return NULL;
+}
+
+/** Invoked when a TLS state changes: log the change at severity 'debug' */
+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. */
+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, tor_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 /* !(defined(HAVE_SSL_CIPHER_FIND)) */
+
+# 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, tor_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 /* defined(HAVE_STRUCT_SSL_METHOD_ST_GET_CIPHER_BY_CHAR) */
+# 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 /* !defined(OPENSSL_1_1_API) */
+  (void) ssl;
+  (void) m;
+  (void) cipher;
+  return 1; /* No way to search */
+#endif /* defined(HAVE_SSL_CIPHER_FIND) */
+}
+
+/** 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.
+ **/
+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. */
+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 /* defined(HAVE_SSL_GET_CLIENT_CIPHERS) */
+
+  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>
+ */
+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;
+  } 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.
+ */
+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 = tor_tls_context_get(isServer);
+  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 /* defined(SSL_set_tlsext_host_name) */
+
+  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, 0);
+  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;
+}
+
+/** 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 /* defined(SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION) && ... */
+}
+
+void
+tor_tls_impl_free_(tor_tls_impl_t *ssl)
+{
+  if (!ssl)
+    return;
+
+#ifdef SSL_set_tlsext_host_name
+  SSL_set_tlsext_host_name(ssl, NULL);
+#endif
+  SSL_free(ssl);
+}
+
+/** 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 initial 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;
+}
+
+/** 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);
+}
+
+/** 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(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;
+}
+
+/** 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 /* !(OPENSSL_VERSION_NUMBER >= OPENSSL_VER(1,1,0,0,5)) */
+  if (wbio->method == BIO_f_buffer() && (tmpbio = BIO_next(wbio)) != NULL)
+    wbio = tmpbio;
+#endif /* OPENSSL_VERSION_NUMBER >= OPENSSL_VER(1,1,0,0,5) */
+  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 ((double)total_bytes_written_by_tls) /
+    ((double)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 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 /* !defined(HAVE_SSL_GET_CLIENT_RANDOM) */
+
+#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 /* !defined(HAVE_SSL_GET_SERVER_RANDOM) */
+
+#ifndef HAVE_SSL_SESSION_GET_MASTER_KEY
+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 /* !defined(HAVE_SSL_SESSION_GET_MASTER_KEY) */
+
+/** 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 /* !(OPENSSL_VERSION_NUMBER >= OPENSSL_V_SERIES(1,1,0)) */
+  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 /* OPENSSL_VERSION_NUMBER >= OPENSSL_V_SERIES(1,1,0) */
+}
+
+/** 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;
+}