Reorganize functions in be-secure-openssl.c

Move the functions within the file so that public interface functions come
first, followed by internal functions. Previously, be_tls_write was first,
then internal stuff, and finally the rest of the public interface, which
clearly didn't make much sense.

Per Andres Freund's complaint.

src/backend/libpq/be-secure-openssl.c

@@ -75,12 +75,17 @@
 #include "utils/memutils.h"
 
 
+static int my_sock_read(BIO *h, char *buf, int size);
+static int my_sock_write(BIO *h, const char *buf, int size);
+static BIO_METHOD *my_BIO_s_socket(void);
+static int my_SSL_set_fd(Port *port, int fd);
 
 static DH  *load_dh_file(int keylength);
 static DH  *load_dh_buffer(const char *, size_t);
 static DH  *tmp_dh_cb(SSL *s, int is_export, int keylength);
 static int	verify_cb(int, X509_STORE_CTX *);
 static void info_cb(const SSL *ssl, int type, int args);
+static void initialize_ecdh(void);
 static const char *SSLerrmessage(void);
 
 /* are we in the middle of a renegotiation? */
@@ -153,870 +158,876 @@ AaqLulO7R8Ifa1SwF2DteSGVtgWEN8gDpN3RBmmPTDngyF2DHb5qmpnznwtFKdTL\n\
 KWbuHn491xNO25CQWMtem80uKw+pTnisBRF/454n1Jnhub144YRBoN8CAQI=\n\
 -----END DH PARAMETERS-----\n";
 
+
+/* ------------------------------------------------------------ */
+/*						 Public interface						*/
+/* ------------------------------------------------------------ */
+
 /*
- *	Write data to a secure connection.
+ *	Initialize global SSL context.
  */
-ssize_t
-be_tls_write(Port *port, void *ptr, size_t len)
+void
+be_tls_init(void)
 {
-	ssize_t		n;
-	int			err;
+	struct stat buf;
 
-	/*
-	 * If SSL renegotiations are enabled and we're getting close to the
-	 * limit, start one now; but avoid it if there's one already in
-	 * progress.  Request the renegotiation 1kB before the limit has
-	 * actually expired.
-	 */
-	if (ssl_renegotiation_limit && !in_ssl_renegotiation &&
-		port->count > (ssl_renegotiation_limit - 1) * 1024L)
+	STACK_OF(X509_NAME) *root_cert_list = NULL;
+
+	if (!SSL_context)
 	{
-		in_ssl_renegotiation = true;
+#if SSLEAY_VERSION_NUMBER >= 0x0907000L
+		OPENSSL_config(NULL);
+#endif
+		SSL_library_init();
+		SSL_load_error_strings();
 
 		/*
-		 * The way we determine that a renegotiation has completed is by
-		 * observing OpenSSL's internal renegotiation counter.  Make sure
-		 * we start out at zero, and assume that the renegotiation is
-		 * complete when the counter advances.
-		 *
-		 * OpenSSL provides SSL_renegotiation_pending(), but this doesn't
-		 * seem to work in testing.
+		 * We use SSLv23_method() because it can negotiate use of the highest
+		 * mutually supported protocol version, while alternatives like
+		 * TLSv1_2_method() permit only one specific version.  Note that we
+		 * don't actually allow SSL v2 or v3, only TLS protocols (see below).
 		 */
-		SSL_clear_num_renegotiations(port->ssl);
-
-		SSL_set_session_id_context(port->ssl, (void *) &SSL_context,
-								   sizeof(SSL_context));
-		if (SSL_renegotiate(port->ssl) <= 0)
-			ereport(COMMERROR,
-					(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					 errmsg("SSL failure during renegotiation start")));
-		else
-		{
-			int			retries;
+		SSL_context = SSL_CTX_new(SSLv23_method());
+		if (!SSL_context)
+			ereport(FATAL,
+					(errmsg("could not create SSL context: %s",
+							SSLerrmessage())));
 
-			/*
-			 * A handshake can fail, so be prepared to retry it, but only
-			 * a few times.
-			 */
-			for (retries = 0;; retries++)
-			{
-				if (SSL_do_handshake(port->ssl) > 0)
-					break;	/* done */
-				ereport(COMMERROR,
-						(errcode(ERRCODE_PROTOCOL_VIOLATION),
-						 errmsg("SSL handshake failure on renegotiation, retrying")));
-				if (retries >= 20)
-					ereport(FATAL,
-							(errcode(ERRCODE_PROTOCOL_VIOLATION),
-							 errmsg("unable to complete SSL handshake")));
-			}
-		}
-	}
+		/*
+		 * Disable OpenSSL's moving-write-buffer sanity check, because it
+		 * causes unnecessary failures in nonblocking send cases.
+		 */
+		SSL_CTX_set_mode(SSL_context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
-wloop:
-	errno = 0;
-	n = SSL_write(port->ssl, ptr, len);
-	err = SSL_get_error(port->ssl, n);
-	switch (err)
-	{
-		case SSL_ERROR_NONE:
-			port->count += n;
-			break;
-		case SSL_ERROR_WANT_READ:
-		case SSL_ERROR_WANT_WRITE:
-#ifdef WIN32
-			pgwin32_waitforsinglesocket(SSL_get_fd(port->ssl),
-										(err == SSL_ERROR_WANT_READ) ?
-									FD_READ | FD_CLOSE : FD_WRITE | FD_CLOSE,
-										INFINITE);
-#endif
-			goto wloop;
-		case SSL_ERROR_SYSCALL:
-			/* leave it to caller to ereport the value of errno */
-			if (n != -1)
-			{
-				errno = ECONNRESET;
-				n = -1;
-			}
-			break;
-		case SSL_ERROR_SSL:
-			ereport(COMMERROR,
-					(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					 errmsg("SSL error: %s", SSLerrmessage())));
-			/* fall through */
-		case SSL_ERROR_ZERO_RETURN:
-			errno = ECONNRESET;
-			n = -1;
-			break;
-		default:
-			ereport(COMMERROR,
-					(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					 errmsg("unrecognized SSL error code: %d",
-							err)));
-			errno = ECONNRESET;
-			n = -1;
-			break;
-	}
+		/*
+		 * Load and verify server's certificate and private key
+		 */
+		if (SSL_CTX_use_certificate_chain_file(SSL_context,
+											   ssl_cert_file) != 1)
+			ereport(FATAL,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				  errmsg("could not load server certificate file \"%s\": %s",
+						 ssl_cert_file, SSLerrmessage())));
 
-	if (n >= 0)
-	{
-		/* is renegotiation complete? */
-		if (in_ssl_renegotiation &&
-			SSL_num_renegotiations(port->ssl) >= 1)
-		{
-			in_ssl_renegotiation = false;
-			port->count = 0;
-		}
+		if (stat(ssl_key_file, &buf) != 0)
+			ereport(FATAL,
+					(errcode_for_file_access(),
+					 errmsg("could not access private key file \"%s\": %m",
+							ssl_key_file)));
 
 		/*
-		 * if renegotiation is still ongoing, and we've gone beyond the
-		 * limit, kill the connection now -- continuing to use it can be
-		 * considered a security problem.
+		 * Require no public access to key file.
+		 *
+		 * XXX temporarily suppress check when on Windows, because there may
+		 * not be proper support for Unix-y file permissions.  Need to think
+		 * of a reasonable check to apply on Windows.  (See also the data
+		 * directory permission check in postmaster.c)
 		 */
-		if (in_ssl_renegotiation &&
-			port->count > ssl_renegotiation_limit * 1024L)
+#if !defined(WIN32) && !defined(__CYGWIN__)
+		if (!S_ISREG(buf.st_mode) || buf.st_mode & (S_IRWXG | S_IRWXO))
 			ereport(FATAL,
-					(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					 errmsg("SSL failed to renegotiate connection before limit expired")));
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				  errmsg("private key file \"%s\" has group or world access",
+						 ssl_key_file),
+				   errdetail("Permissions should be u=rw (0600) or less.")));
+#endif
+
+		if (SSL_CTX_use_PrivateKey_file(SSL_context,
+										ssl_key_file,
+										SSL_FILETYPE_PEM) != 1)
+			ereport(FATAL,
+					(errmsg("could not load private key file \"%s\": %s",
+							ssl_key_file, SSLerrmessage())));
+
+		if (SSL_CTX_check_private_key(SSL_context) != 1)
+			ereport(FATAL,
+					(errmsg("check of private key failed: %s",
+							SSLerrmessage())));
 	}
 
-	return n;
-}
+	/* set up ephemeral DH keys, and disallow SSL v2/v3 while at it */
+	SSL_CTX_set_tmp_dh_callback(SSL_context, tmp_dh_cb);
+	SSL_CTX_set_options(SSL_context,
+						SSL_OP_SINGLE_DH_USE |
+						SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3);
 
-/* ------------------------------------------------------------ */
-/*						OpenSSL specific code					*/
-/* ------------------------------------------------------------ */
+	/* set up ephemeral ECDH keys */
+	initialize_ecdh();
 
-/*
- * Private substitute BIO: this does the sending and receiving using send() and
- * recv() instead. This is so that we can enable and disable interrupts
- * just while calling recv(). We cannot have interrupts occurring while
- * the bulk of openssl runs, because it uses malloc() and possibly other
- * non-reentrant libc facilities. We also need to call send() and recv()
- * directly so it gets passed through the socket/signals layer on Win32.
- *
- * These functions are closely modelled on the standard socket BIO in OpenSSL;
- * see sock_read() and sock_write() in OpenSSL's crypto/bio/bss_sock.c.
- * XXX OpenSSL 1.0.1e considers many more errcodes than just EINTR as reasons
- * to retry; do we need to adopt their logic for that?
- */
+	/* set up the allowed cipher list */
+	if (SSL_CTX_set_cipher_list(SSL_context, SSLCipherSuites) != 1)
+		elog(FATAL, "could not set the cipher list (no valid ciphers available)");
 
-static bool my_bio_initialized = false;
-static BIO_METHOD my_bio_methods;
+	/* Let server choose order */
+	if (SSLPreferServerCiphers)
+		SSL_CTX_set_options(SSL_context, SSL_OP_CIPHER_SERVER_PREFERENCE);
 
-static int
-my_sock_read(BIO *h, char *buf, int size)
-{
-	int			res = 0;
+	/*
+	 * Load CA store, so we can verify client certificates if needed.
+	 */
+	if (ssl_ca_file[0])
+	{
+		if (SSL_CTX_load_verify_locations(SSL_context, ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+			ereport(FATAL,
+					(errmsg("could not load root certificate file \"%s\": %s",
+							ssl_ca_file, SSLerrmessage())));
+	}
 
-	if (buf != NULL)
+	/*----------
+	 * Load the Certificate Revocation List (CRL).
+	 * http://searchsecurity.techtarget.com/sDefinition/0,,sid14_gci803160,00.html
+	 *----------
+	 */
+	if (ssl_crl_file[0])
 	{
-		res = secure_raw_read(((Port *)h->ptr), buf, size);
-		BIO_clear_retry_flags(h);
-		if (res <= 0)
+		X509_STORE *cvstore = SSL_CTX_get_cert_store(SSL_context);
+
+		if (cvstore)
 		{
-			/* If we were interrupted, tell caller to retry */
-			if (errno == EINTR)
+			/* Set the flags to check against the complete CRL chain */
+			if (X509_STORE_load_locations(cvstore, ssl_crl_file, NULL) == 1)
 			{
-				BIO_set_retry_read(h);
+				/* OpenSSL 0.96 does not support X509_V_FLAG_CRL_CHECK */
+#ifdef X509_V_FLAG_CRL_CHECK
+				X509_STORE_set_flags(cvstore,
+						  X509_V_FLAG_CRL_CHECK | X509_V_FLAG_CRL_CHECK_ALL);
+#else
+				ereport(LOG,
+				(errmsg("SSL certificate revocation list file \"%s\" ignored",
+						ssl_crl_file),
+				 errdetail("SSL library does not support certificate revocation lists.")));
+#endif
 			}
-		}
-	}
+			else
+				ereport(FATAL,
+						(errmsg("could not load SSL certificate revocation list file \"%s\": %s",
+								ssl_crl_file, SSLerrmessage())));
+		}
+	}
 
-	return res;
+	if (ssl_ca_file[0])
+	{
+		/*
+		 * Always ask for SSL client cert, but don't fail if it's not
+		 * presented.  We might fail such connections later, depending on what
+		 * we find in pg_hba.conf.
+		 */
+		SSL_CTX_set_verify(SSL_context,
+						   (SSL_VERIFY_PEER |
+							SSL_VERIFY_CLIENT_ONCE),
+						   verify_cb);
+
+		/* Set flag to remember CA store is successfully loaded */
+		ssl_loaded_verify_locations = true;
+
+		/*
+		 * Tell OpenSSL to send the list of root certs we trust to clients in
+		 * CertificateRequests.  This lets a client with a keystore select the
+		 * appropriate client certificate to send to us.
+		 */
+		SSL_CTX_set_client_CA_list(SSL_context, root_cert_list);
+	}
 }
 
-static int
-my_sock_write(BIO *h, const char *buf, int size)
+/*
+ *	Attempt to negotiate SSL connection.
+ */
+int
+be_tls_open_server(Port *port)
 {
-	int			res = 0;
+	int			r;
+	int			err;
 
-	res = secure_raw_write(((Port *) h->ptr), buf, size);
-	BIO_clear_retry_flags(h);
-	if (res <= 0)
+	Assert(!port->ssl);
+	Assert(!port->peer);
+
+	if (!(port->ssl = SSL_new(SSL_context)))
 	{
-		if (errno == EINTR)
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("could not initialize SSL connection: %s",
+						SSLerrmessage())));
+		be_tls_close(port);
+		return -1;
+	}
+	if (!my_SSL_set_fd(port, port->sock))
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("could not set SSL socket: %s",
+						SSLerrmessage())));
+		be_tls_close(port);
+		return -1;
+	}
+	port->ssl_in_use = true;
+
+aloop:
+	r = SSL_accept(port->ssl);
+	if (r <= 0)
+	{
+		err = SSL_get_error(port->ssl, r);
+		switch (err)
 		{
-			BIO_set_retry_write(h);
+			case SSL_ERROR_WANT_READ:
+			case SSL_ERROR_WANT_WRITE:
+#ifdef WIN32
+				pgwin32_waitforsinglesocket(SSL_get_fd(port->ssl),
+											(err == SSL_ERROR_WANT_READ) ?
+						FD_READ | FD_CLOSE | FD_ACCEPT : FD_WRITE | FD_CLOSE,
+											INFINITE);
+#endif
+				goto aloop;
+			case SSL_ERROR_SYSCALL:
+				if (r < 0)
+					ereport(COMMERROR,
+							(errcode_for_socket_access(),
+							 errmsg("could not accept SSL connection: %m")));
+				else
+					ereport(COMMERROR,
+							(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					errmsg("could not accept SSL connection: EOF detected")));
+				break;
+			case SSL_ERROR_SSL:
+				ereport(COMMERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("could not accept SSL connection: %s",
+								SSLerrmessage())));
+				break;
+			case SSL_ERROR_ZERO_RETURN:
+				ereport(COMMERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				   errmsg("could not accept SSL connection: EOF detected")));
+				break;
+			default:
+				ereport(COMMERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("unrecognized SSL error code: %d",
+								err)));
+				break;
 		}
+		be_tls_close(port);
+		return -1;
 	}
 
-	return res;
-}
+	port->count = 0;
 
-static BIO_METHOD *
-my_BIO_s_socket(void)
-{
-	if (!my_bio_initialized)
+	/* Get client certificate, if available. */
+	port->peer = SSL_get_peer_certificate(port->ssl);
+
+	/* and extract the Common Name from it. */
+	port->peer_cn = NULL;
+	port->peer_cert_valid = false;
+	if (port->peer != NULL)
 	{
-		memcpy(&my_bio_methods, BIO_s_socket(), sizeof(BIO_METHOD));
-		my_bio_methods.bread = my_sock_read;
-		my_bio_methods.bwrite = my_sock_write;
-		my_bio_initialized = true;
-	}
-	return &my_bio_methods;
-}
+		int			len;
 
-/* This should exactly match openssl's SSL_set_fd except for using my BIO */
-static int
-my_SSL_set_fd(Port *port, int fd)
-{
-	int			ret = 0;
-	BIO		   *bio = NULL;
+		len = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
+										NID_commonName, NULL, 0);
+		if (len != -1)
+		{
+			char	   *peer_cn;
 
-	bio = BIO_new(my_BIO_s_socket());
+			peer_cn = MemoryContextAlloc(TopMemoryContext, len + 1);
+			r = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
+										  NID_commonName, peer_cn, len + 1);
+			peer_cn[len] = '\0';
+			if (r != len)
+			{
+				/* shouldn't happen */
+				pfree(peer_cn);
+				be_tls_close(port);
+				return -1;
+			}
 
-	if (bio == NULL)
-	{
-		SSLerr(SSL_F_SSL_SET_FD, ERR_R_BUF_LIB);
-		goto err;
+			/*
+			 * Reject embedded NULLs in certificate common name to prevent
+			 * attacks like CVE-2009-4034.
+			 */
+			if (len != strlen(peer_cn))
+			{
+				ereport(COMMERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("SSL certificate's common name contains embedded null")));
+				pfree(peer_cn);
+				be_tls_close(port);
+				return -1;
+			}
+
+			port->peer_cn = peer_cn;
+		}
+		port->peer_cert_valid = true;
 	}
-	/* Use 'ptr' to store pointer to PGconn */
-	bio->ptr = port;
 
-	BIO_set_fd(bio, fd, BIO_NOCLOSE);
-	SSL_set_bio(port->ssl, bio, bio);
-	ret = 1;
-err:
-	return ret;
+	ereport(DEBUG2,
+			(errmsg("SSL connection from \"%s\"",
+					port->peer_cn ? port->peer_cn : "(anonymous)")));
+
+	/* set up debugging/info callback */
+	SSL_CTX_set_info_callback(SSL_context, info_cb);
+
+	return 0;
 }
 
 /*
- *	Load precomputed DH parameters.
- *
- *	To prevent "downgrade" attacks, we perform a number of checks
- *	to verify that the DBA-generated DH parameters file contains
- *	what we expect it to contain.
+ *	Close SSL connection.
  */
-static DH  *
-load_dh_file(int keylength)
+void
+be_tls_close(Port *port)
 {
-	FILE	   *fp;
-	char		fnbuf[MAXPGPATH];
-	DH		   *dh = NULL;
-	int			codes;
-
-	/* attempt to open file.  It's not an error if it doesn't exist. */
-	snprintf(fnbuf, sizeof(fnbuf), "dh%d.pem", keylength);
-	if ((fp = fopen(fnbuf, "r")) == NULL)
-		return NULL;
-
-/*	flock(fileno(fp), LOCK_SH); */
-	dh = PEM_read_DHparams(fp, NULL, NULL, NULL);
-/*	flock(fileno(fp), LOCK_UN); */
-	fclose(fp);
-
-	/* is the prime the correct size? */
-	if (dh != NULL && 8 * DH_size(dh) < keylength)
+	if (port->ssl)
 	{
-		elog(LOG, "DH errors (%s): %d bits expected, %d bits found",
-			 fnbuf, keylength, 8 * DH_size(dh));
-		dh = NULL;
+		SSL_shutdown(port->ssl);
+		SSL_free(port->ssl);
+		port->ssl = NULL;
+		port->ssl_in_use = false;
 	}
 
-	/* make sure the DH parameters are usable */
-	if (dh != NULL)
+	if (port->peer)
 	{
-		if (DH_check(dh, &codes) == 0)
-		{
-			elog(LOG, "DH_check error (%s): %s", fnbuf, SSLerrmessage());
-			return NULL;
-		}
-		if (codes & DH_CHECK_P_NOT_PRIME)
-		{
-			elog(LOG, "DH error (%s): p is not prime", fnbuf);
-			return NULL;
-		}
-		if ((codes & DH_NOT_SUITABLE_GENERATOR) &&
-			(codes & DH_CHECK_P_NOT_SAFE_PRIME))
-		{
-			elog(LOG,
-				 "DH error (%s): neither suitable generator or safe prime",
-				 fnbuf);
-			return NULL;
-		}
+		X509_free(port->peer);
+		port->peer = NULL;
 	}
 
-	return dh;
+	if (port->peer_cn)
+	{
+		pfree(port->peer_cn);
+		port->peer_cn = NULL;
+	}
 }
 
 /*
- *	Load hardcoded DH parameters.
- *
- *	To prevent problems if the DH parameters files don't even
- *	exist, we can load DH parameters hardcoded into this file.
+ *	Read data from a secure connection.
  */
-static DH  *
-load_dh_buffer(const char *buffer, size_t len)
-{
-	BIO		   *bio;
-	DH		   *dh = NULL;
-
-	bio = BIO_new_mem_buf((char *) buffer, len);
-	if (bio == NULL)
-		return NULL;
-	dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
-	if (dh == NULL)
-		ereport(DEBUG2,
-				(errmsg_internal("DH load buffer: %s",
-								 SSLerrmessage())));
-	BIO_free(bio);
-
-	return dh;
-}
-
-/*
- *	Generate an ephemeral DH key.  Because this can take a long
- *	time to compute, we can use precomputed parameters of the
- *	common key sizes.
- *
- *	Since few sites will bother to precompute these parameter
- *	files, we also provide a fallback to the parameters provided
- *	by the OpenSSL project.
- *
- *	These values can be static (once loaded or computed) since
- *	the OpenSSL library can efficiently generate random keys from
- *	the information provided.
- */
-static DH  *
-tmp_dh_cb(SSL *s, int is_export, int keylength)
+ssize_t
+be_tls_read(Port *port, void *ptr, size_t len)
 {
-	DH		   *r = NULL;
-	static DH  *dh = NULL;
-	static DH  *dh512 = NULL;
-	static DH  *dh1024 = NULL;
-	static DH  *dh2048 = NULL;
-	static DH  *dh4096 = NULL;
+	ssize_t		n;
+	int			err;
 
-	switch (keylength)
+rloop:
+	errno = 0;
+	n = SSL_read(port->ssl, ptr, len);
+	err = SSL_get_error(port->ssl, n);
+	switch (err)
 	{
-		case 512:
-			if (dh512 == NULL)
-				dh512 = load_dh_file(keylength);
-			if (dh512 == NULL)
-				dh512 = load_dh_buffer(file_dh512, sizeof file_dh512);
-			r = dh512;
-			break;
-
-		case 1024:
-			if (dh1024 == NULL)
-				dh1024 = load_dh_file(keylength);
-			if (dh1024 == NULL)
-				dh1024 = load_dh_buffer(file_dh1024, sizeof file_dh1024);
-			r = dh1024;
+		case SSL_ERROR_NONE:
+			port->count += n;
 			break;
-
-		case 2048:
-			if (dh2048 == NULL)
-				dh2048 = load_dh_file(keylength);
-			if (dh2048 == NULL)
-				dh2048 = load_dh_buffer(file_dh2048, sizeof file_dh2048);
-			r = dh2048;
+		case SSL_ERROR_WANT_READ:
+		case SSL_ERROR_WANT_WRITE:
+			if (port->noblock)
+			{
+				errno = EWOULDBLOCK;
+				n = -1;
+				break;
+			}
+#ifdef WIN32
+			pgwin32_waitforsinglesocket(SSL_get_fd(port->ssl),
+										(err == SSL_ERROR_WANT_READ) ?
+									FD_READ | FD_CLOSE : FD_WRITE | FD_CLOSE,
+										INFINITE);
+#endif
+			goto rloop;
+		case SSL_ERROR_SYSCALL:
+			/* leave it to caller to ereport the value of errno */
+			if (n != -1)
+			{
+				errno = ECONNRESET;
+				n = -1;
+			}
 			break;
-
-		case 4096:
-			if (dh4096 == NULL)
-				dh4096 = load_dh_file(keylength);
-			if (dh4096 == NULL)
-				dh4096 = load_dh_buffer(file_dh4096, sizeof file_dh4096);
-			r = dh4096;
+		case SSL_ERROR_SSL:
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("SSL error: %s", SSLerrmessage())));
+			/* fall through */
+		case SSL_ERROR_ZERO_RETURN:
+			errno = ECONNRESET;
+			n = -1;
 			break;
-
 		default:
-			if (dh == NULL)
-				dh = load_dh_file(keylength);
-			r = dh;
-	}
-
-	/* this may take a long time, but it may be necessary... */
-	if (r == NULL || 8 * DH_size(r) < keylength)
-	{
-		ereport(DEBUG2,
-				(errmsg_internal("DH: generating parameters (%d bits)",
-								 keylength)));
-		r = DH_generate_parameters(keylength, DH_GENERATOR_2, NULL, NULL);
-	}
-
-	return r;
-}
-
-/*
- *	Certificate verification callback
- *
- *	This callback allows us to log intermediate problems during
- *	verification, but for now we'll see if the final error message
- *	contains enough information.
- *
- *	This callback also allows us to override the default acceptance
- *	criteria (e.g., accepting self-signed or expired certs), but
- *	for now we accept the default checks.
- */
-static int
-verify_cb(int ok, X509_STORE_CTX *ctx)
-{
-	return ok;
-}
-
-/*
- *	This callback is used to copy SSL information messages
- *	into the PostgreSQL log.
- */
-static void
-info_cb(const SSL *ssl, int type, int args)
-{
-	switch (type)
-	{
-		case SSL_CB_HANDSHAKE_START:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: handshake start")));
-			break;
-		case SSL_CB_HANDSHAKE_DONE:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: handshake done")));
-			break;
-		case SSL_CB_ACCEPT_LOOP:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: accept loop")));
-			break;
-		case SSL_CB_ACCEPT_EXIT:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: accept exit (%d)", args)));
-			break;
-		case SSL_CB_CONNECT_LOOP:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: connect loop")));
-			break;
-		case SSL_CB_CONNECT_EXIT:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: connect exit (%d)", args)));
-			break;
-		case SSL_CB_READ_ALERT:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: read alert (0x%04x)", args)));
-			break;
-		case SSL_CB_WRITE_ALERT:
-			ereport(DEBUG4,
-					(errmsg_internal("SSL: write alert (0x%04x)", args)));
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("unrecognized SSL error code: %d",
+							err)));
+			errno = ECONNRESET;
+			n = -1;
 			break;
 	}
-}
-
-#if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_ECDH)
-static void
-initialize_ecdh(void)
-{
-	EC_KEY	   *ecdh;
-	int			nid;
-
-	nid = OBJ_sn2nid(SSLECDHCurve);
-	if (!nid)
-		ereport(FATAL,
-				(errmsg("ECDH: unrecognized curve name: %s", SSLECDHCurve)));
-
-	ecdh = EC_KEY_new_by_curve_name(nid);
-	if (!ecdh)
-		ereport(FATAL,
-				(errmsg("ECDH: could not create key")));
 
-	SSL_CTX_set_options(SSL_context, SSL_OP_SINGLE_ECDH_USE);
-	SSL_CTX_set_tmp_ecdh(SSL_context, ecdh);
-	EC_KEY_free(ecdh);
+	return n;
 }
-#else
-#define initialize_ecdh()
-#endif
 
 /*
- *	Initialize global SSL context.
+ *	Write data to a secure connection.
  */
-void
-be_tls_init(void)
+ssize_t
+be_tls_write(Port *port, void *ptr, size_t len)
 {
-	struct stat buf;
-
-	STACK_OF(X509_NAME) *root_cert_list = NULL;
+	ssize_t		n;
+	int			err;
 
-	if (!SSL_context)
+	/*
+	 * If SSL renegotiations are enabled and we're getting close to the
+	 * limit, start one now; but avoid it if there's one already in
+	 * progress.  Request the renegotiation 1kB before the limit has
+	 * actually expired.
+	 */
+	if (ssl_renegotiation_limit && !in_ssl_renegotiation &&
+		port->count > (ssl_renegotiation_limit - 1) * 1024L)
 	{
-#if SSLEAY_VERSION_NUMBER >= 0x0907000L
-		OPENSSL_config(NULL);
-#endif
-		SSL_library_init();
-		SSL_load_error_strings();
-
-		/*
-		 * We use SSLv23_method() because it can negotiate use of the highest
-		 * mutually supported protocol version, while alternatives like
-		 * TLSv1_2_method() permit only one specific version.  Note that we
-		 * don't actually allow SSL v2 or v3, only TLS protocols (see below).
-		 */
-		SSL_context = SSL_CTX_new(SSLv23_method());
-		if (!SSL_context)
-			ereport(FATAL,
-					(errmsg("could not create SSL context: %s",
-							SSLerrmessage())));
-
-		/*
-		 * Disable OpenSSL's moving-write-buffer sanity check, because it
-		 * causes unnecessary failures in nonblocking send cases.
-		 */
-		SSL_CTX_set_mode(SSL_context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
-
-		/*
-		 * Load and verify server's certificate and private key
-		 */
-		if (SSL_CTX_use_certificate_chain_file(SSL_context,
-											   ssl_cert_file) != 1)
-			ereport(FATAL,
-					(errcode(ERRCODE_CONFIG_FILE_ERROR),
-				  errmsg("could not load server certificate file \"%s\": %s",
-						 ssl_cert_file, SSLerrmessage())));
-
-		if (stat(ssl_key_file, &buf) != 0)
-			ereport(FATAL,
-					(errcode_for_file_access(),
-					 errmsg("could not access private key file \"%s\": %m",
-							ssl_key_file)));
+		in_ssl_renegotiation = true;
 
 		/*
-		 * Require no public access to key file.
+		 * The way we determine that a renegotiation has completed is by
+		 * observing OpenSSL's internal renegotiation counter.  Make sure
+		 * we start out at zero, and assume that the renegotiation is
+		 * complete when the counter advances.
 		 *
-		 * XXX temporarily suppress check when on Windows, because there may
-		 * not be proper support for Unix-y file permissions.  Need to think
-		 * of a reasonable check to apply on Windows.  (See also the data
-		 * directory permission check in postmaster.c)
+		 * OpenSSL provides SSL_renegotiation_pending(), but this doesn't
+		 * seem to work in testing.
 		 */
-#if !defined(WIN32) && !defined(__CYGWIN__)
-		if (!S_ISREG(buf.st_mode) || buf.st_mode & (S_IRWXG | S_IRWXO))
-			ereport(FATAL,
-					(errcode(ERRCODE_CONFIG_FILE_ERROR),
-				  errmsg("private key file \"%s\" has group or world access",
-						 ssl_key_file),
-				   errdetail("Permissions should be u=rw (0600) or less.")));
-#endif
-
-		if (SSL_CTX_use_PrivateKey_file(SSL_context,
-										ssl_key_file,
-										SSL_FILETYPE_PEM) != 1)
-			ereport(FATAL,
-					(errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage())));
-
-		if (SSL_CTX_check_private_key(SSL_context) != 1)
-			ereport(FATAL,
-					(errmsg("check of private key failed: %s",
-							SSLerrmessage())));
-	}
-
-	/* set up ephemeral DH keys, and disallow SSL v2/v3 while at it */
-	SSL_CTX_set_tmp_dh_callback(SSL_context, tmp_dh_cb);
-	SSL_CTX_set_options(SSL_context,
-						SSL_OP_SINGLE_DH_USE |
-						SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3);
-
-	/* set up ephemeral ECDH keys */
-	initialize_ecdh();
-
-	/* set up the allowed cipher list */
-	if (SSL_CTX_set_cipher_list(SSL_context, SSLCipherSuites) != 1)
-		elog(FATAL, "could not set the cipher list (no valid ciphers available)");
+		SSL_clear_num_renegotiations(port->ssl);
 
-	/* Let server choose order */
-	if (SSLPreferServerCiphers)
-		SSL_CTX_set_options(SSL_context, SSL_OP_CIPHER_SERVER_PREFERENCE);
+		SSL_set_session_id_context(port->ssl, (void *) &SSL_context,
+								   sizeof(SSL_context));
+		if (SSL_renegotiate(port->ssl) <= 0)
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("SSL failure during renegotiation start")));
+		else
+		{
+			int			retries;
 
-	/*
-	 * Load CA store, so we can verify client certificates if needed.
-	 */
-	if (ssl_ca_file[0])
-	{
-		if (SSL_CTX_load_verify_locations(SSL_context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
-			ereport(FATAL,
-					(errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage())));
+			/*
+			 * A handshake can fail, so be prepared to retry it, but only
+			 * a few times.
+			 */
+			for (retries = 0;; retries++)
+			{
+				if (SSL_do_handshake(port->ssl) > 0)
+					break;	/* done */
+				ereport(COMMERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("SSL handshake failure on renegotiation, retrying")));
+				if (retries >= 20)
+					ereport(FATAL,
+							(errcode(ERRCODE_PROTOCOL_VIOLATION),
+							 errmsg("unable to complete SSL handshake")));
+			}
+		}
 	}
 
-	/*----------
-	 * Load the Certificate Revocation List (CRL).
-	 * http://searchsecurity.techtarget.com/sDefinition/0,,sid14_gci803160,00.html
-	 *----------
-	 */
-	if (ssl_crl_file[0])
+wloop:
+	errno = 0;
+	n = SSL_write(port->ssl, ptr, len);
+	err = SSL_get_error(port->ssl, n);
+	switch (err)
 	{
-		X509_STORE *cvstore = SSL_CTX_get_cert_store(SSL_context);
-
-		if (cvstore)
-		{
-			/* Set the flags to check against the complete CRL chain */
-			if (X509_STORE_load_locations(cvstore, ssl_crl_file, NULL) == 1)
-			{
-				/* OpenSSL 0.96 does not support X509_V_FLAG_CRL_CHECK */
-#ifdef X509_V_FLAG_CRL_CHECK
-				X509_STORE_set_flags(cvstore,
-						  X509_V_FLAG_CRL_CHECK | X509_V_FLAG_CRL_CHECK_ALL);
-#else
-				ereport(LOG,
-				(errmsg("SSL certificate revocation list file \"%s\" ignored",
-						ssl_crl_file),
-				 errdetail("SSL library does not support certificate revocation lists.")));
+		case SSL_ERROR_NONE:
+			port->count += n;
+			break;
+		case SSL_ERROR_WANT_READ:
+		case SSL_ERROR_WANT_WRITE:
+#ifdef WIN32
+			pgwin32_waitforsinglesocket(SSL_get_fd(port->ssl),
+										(err == SSL_ERROR_WANT_READ) ?
+									FD_READ | FD_CLOSE : FD_WRITE | FD_CLOSE,
+										INFINITE);
 #endif
+			goto wloop;
+		case SSL_ERROR_SYSCALL:
+			/* leave it to caller to ereport the value of errno */
+			if (n != -1)
+			{
+				errno = ECONNRESET;
+				n = -1;
 			}
-			else
-				ereport(FATAL,
-						(errmsg("could not load SSL certificate revocation list file \"%s\": %s",
-								ssl_crl_file, SSLerrmessage())));
-		}
+			break;
+		case SSL_ERROR_SSL:
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("SSL error: %s", SSLerrmessage())));
+			/* fall through */
+		case SSL_ERROR_ZERO_RETURN:
+			errno = ECONNRESET;
+			n = -1;
+			break;
+		default:
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("unrecognized SSL error code: %d",
+							err)));
+			errno = ECONNRESET;
+			n = -1;
+			break;
 	}
 
-	if (ssl_ca_file[0])
+	if (n >= 0)
 	{
-		/*
-		 * Always ask for SSL client cert, but don't fail if it's not
-		 * presented.  We might fail such connections later, depending on what
-		 * we find in pg_hba.conf.
-		 */
-		SSL_CTX_set_verify(SSL_context,
-						   (SSL_VERIFY_PEER |
-							SSL_VERIFY_CLIENT_ONCE),
-						   verify_cb);
-
-		/* Set flag to remember CA store is successfully loaded */
-		ssl_loaded_verify_locations = true;
+		/* is renegotiation complete? */
+		if (in_ssl_renegotiation &&
+			SSL_num_renegotiations(port->ssl) >= 1)
+		{
+			in_ssl_renegotiation = false;
+			port->count = 0;
+		}
 
 		/*
-		 * Tell OpenSSL to send the list of root certs we trust to clients in
-		 * CertificateRequests.  This lets a client with a keystore select the
-		 * appropriate client certificate to send to us.
+		 * if renegotiation is still ongoing, and we've gone beyond the
+		 * limit, kill the connection now -- continuing to use it can be
+		 * considered a security problem.
 		 */
-		SSL_CTX_set_client_CA_list(SSL_context, root_cert_list);
+		if (in_ssl_renegotiation &&
+			port->count > ssl_renegotiation_limit * 1024L)
+			ereport(FATAL,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("SSL failed to renegotiate connection before limit expired")));
 	}
+
+	return n;
 }
 
+/* ------------------------------------------------------------ */
+/*						Internal functions						*/
+/* ------------------------------------------------------------ */
+
 /*
- *	Attempt to negotiate SSL connection.
+ * Private substitute BIO: this does the sending and receiving using send() and
+ * recv() instead. This is so that we can enable and disable interrupts
+ * just while calling recv(). We cannot have interrupts occurring while
+ * the bulk of openssl runs, because it uses malloc() and possibly other
+ * non-reentrant libc facilities. We also need to call send() and recv()
+ * directly so it gets passed through the socket/signals layer on Win32.
+ *
+ * These functions are closely modelled on the standard socket BIO in OpenSSL;
+ * see sock_read() and sock_write() in OpenSSL's crypto/bio/bss_sock.c.
+ * XXX OpenSSL 1.0.1e considers many more errcodes than just EINTR as reasons
+ * to retry; do we need to adopt their logic for that?
  */
-int
-be_tls_open_server(Port *port)
-{
-	int			r;
-	int			err;
 
-	Assert(!port->ssl);
-	Assert(!port->peer);
+static bool my_bio_initialized = false;
+static BIO_METHOD my_bio_methods;
 
-	if (!(port->ssl = SSL_new(SSL_context)))
-	{
-		ereport(COMMERROR,
-				(errcode(ERRCODE_PROTOCOL_VIOLATION),
-				 errmsg("could not initialize SSL connection: %s",
-						SSLerrmessage())));
-		be_tls_close(port);
-		return -1;
-	}
-	if (!my_SSL_set_fd(port, port->sock))
+static int
+my_sock_read(BIO *h, char *buf, int size)
+{
+	int			res = 0;
+
+	if (buf != NULL)
 	{
-		ereport(COMMERROR,
-				(errcode(ERRCODE_PROTOCOL_VIOLATION),
-				 errmsg("could not set SSL socket: %s",
-						SSLerrmessage())));
-		be_tls_close(port);
-		return -1;
+		res = secure_raw_read(((Port *)h->ptr), buf, size);
+		BIO_clear_retry_flags(h);
+		if (res <= 0)
+		{
+			/* If we were interrupted, tell caller to retry */
+			if (errno == EINTR)
+			{
+				BIO_set_retry_read(h);
+			}
+		}
 	}
-	port->ssl_in_use = true;
 
-aloop:
-	r = SSL_accept(port->ssl);
-	if (r <= 0)
+	return res;
+}
+
+static int
+my_sock_write(BIO *h, const char *buf, int size)
+{
+	int			res = 0;
+
+	res = secure_raw_write(((Port *) h->ptr), buf, size);
+	BIO_clear_retry_flags(h);
+	if (res <= 0)
 	{
-		err = SSL_get_error(port->ssl, r);
-		switch (err)
+		if (errno == EINTR)
 		{
-			case SSL_ERROR_WANT_READ:
-			case SSL_ERROR_WANT_WRITE:
-#ifdef WIN32
-				pgwin32_waitforsinglesocket(SSL_get_fd(port->ssl),
-											(err == SSL_ERROR_WANT_READ) ?
-						FD_READ | FD_CLOSE | FD_ACCEPT : FD_WRITE | FD_CLOSE,
-											INFINITE);
-#endif
-				goto aloop;
-			case SSL_ERROR_SYSCALL:
-				if (r < 0)
-					ereport(COMMERROR,
-							(errcode_for_socket_access(),
-							 errmsg("could not accept SSL connection: %m")));
-				else
-					ereport(COMMERROR,
-							(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					errmsg("could not accept SSL connection: EOF detected")));
-				break;
-			case SSL_ERROR_SSL:
-				ereport(COMMERROR,
-						(errcode(ERRCODE_PROTOCOL_VIOLATION),
-						 errmsg("could not accept SSL connection: %s",
-								SSLerrmessage())));
-				break;
-			case SSL_ERROR_ZERO_RETURN:
-				ereport(COMMERROR,
-						(errcode(ERRCODE_PROTOCOL_VIOLATION),
-				   errmsg("could not accept SSL connection: EOF detected")));
-				break;
-			default:
-				ereport(COMMERROR,
-						(errcode(ERRCODE_PROTOCOL_VIOLATION),
-						 errmsg("unrecognized SSL error code: %d",
-								err)));
-				break;
+			BIO_set_retry_write(h);
 		}
-		be_tls_close(port);
-		return -1;
 	}
 
-	port->count = 0;
+	return res;
+}
 
-	/* Get client certificate, if available. */
-	port->peer = SSL_get_peer_certificate(port->ssl);
+static BIO_METHOD *
+my_BIO_s_socket(void)
+{
+	if (!my_bio_initialized)
+	{
+		memcpy(&my_bio_methods, BIO_s_socket(), sizeof(BIO_METHOD));
+		my_bio_methods.bread = my_sock_read;
+		my_bio_methods.bwrite = my_sock_write;
+		my_bio_initialized = true;
+	}
+	return &my_bio_methods;
+}
 
-	/* and extract the Common Name from it. */
-	port->peer_cn = NULL;
-	port->peer_cert_valid = false;
-	if (port->peer != NULL)
+/* This should exactly match openssl's SSL_set_fd except for using my BIO */
+static int
+my_SSL_set_fd(Port *port, int fd)
+{
+	int			ret = 0;
+	BIO		   *bio = NULL;
+
+	bio = BIO_new(my_BIO_s_socket());
+
+	if (bio == NULL)
 	{
-		int			len;
+		SSLerr(SSL_F_SSL_SET_FD, ERR_R_BUF_LIB);
+		goto err;
+	}
+	/* Use 'ptr' to store pointer to PGconn */
+	bio->ptr = port;
 
-		len = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
-										NID_commonName, NULL, 0);
-		if (len != -1)
-		{
-			char	   *peer_cn;
+	BIO_set_fd(bio, fd, BIO_NOCLOSE);
+	SSL_set_bio(port->ssl, bio, bio);
+	ret = 1;
+err:
+	return ret;
+}
 
-			peer_cn = MemoryContextAlloc(TopMemoryContext, len + 1);
-			r = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
-										  NID_commonName, peer_cn, len + 1);
-			peer_cn[len] = '\0';
-			if (r != len)
-			{
-				/* shouldn't happen */
-				pfree(peer_cn);
-				be_tls_close(port);
-				return -1;
-			}
+/*
+ *	Load precomputed DH parameters.
+ *
+ *	To prevent "downgrade" attacks, we perform a number of checks
+ *	to verify that the DBA-generated DH parameters file contains
+ *	what we expect it to contain.
+ */
+static DH  *
+load_dh_file(int keylength)
+{
+	FILE	   *fp;
+	char		fnbuf[MAXPGPATH];
+	DH		   *dh = NULL;
+	int			codes;
 
-			/*
-			 * Reject embedded NULLs in certificate common name to prevent
-			 * attacks like CVE-2009-4034.
-			 */
-			if (len != strlen(peer_cn))
-			{
-				ereport(COMMERROR,
-						(errcode(ERRCODE_PROTOCOL_VIOLATION),
-						 errmsg("SSL certificate's common name contains embedded null")));
-				pfree(peer_cn);
-				be_tls_close(port);
-				return -1;
-			}
+	/* attempt to open file.  It's not an error if it doesn't exist. */
+	snprintf(fnbuf, sizeof(fnbuf), "dh%d.pem", keylength);
+	if ((fp = fopen(fnbuf, "r")) == NULL)
+		return NULL;
+
+/*	flock(fileno(fp), LOCK_SH); */
+	dh = PEM_read_DHparams(fp, NULL, NULL, NULL);
+/*	flock(fileno(fp), LOCK_UN); */
+	fclose(fp);
+
+	/* is the prime the correct size? */
+	if (dh != NULL && 8 * DH_size(dh) < keylength)
+	{
+		elog(LOG, "DH errors (%s): %d bits expected, %d bits found",
+			 fnbuf, keylength, 8 * DH_size(dh));
+		dh = NULL;
+	}
 
-			port->peer_cn = peer_cn;
+	/* make sure the DH parameters are usable */
+	if (dh != NULL)
+	{
+		if (DH_check(dh, &codes) == 0)
+		{
+			elog(LOG, "DH_check error (%s): %s", fnbuf, SSLerrmessage());
+			return NULL;
+		}
+		if (codes & DH_CHECK_P_NOT_PRIME)
+		{
+			elog(LOG, "DH error (%s): p is not prime", fnbuf);
+			return NULL;
+		}
+		if ((codes & DH_NOT_SUITABLE_GENERATOR) &&
+			(codes & DH_CHECK_P_NOT_SAFE_PRIME))
+		{
+			elog(LOG,
+				 "DH error (%s): neither suitable generator or safe prime",
+				 fnbuf);
+			return NULL;
 		}
-		port->peer_cert_valid = true;
 	}
 
-	ereport(DEBUG2,
-			(errmsg("SSL connection from \"%s\"",
-					port->peer_cn ? port->peer_cn : "(anonymous)")));
+	return dh;
+}
 
-	/* set up debugging/info callback */
-	SSL_CTX_set_info_callback(SSL_context, info_cb);
+/*
+ *	Load hardcoded DH parameters.
+ *
+ *	To prevent problems if the DH parameters files don't even
+ *	exist, we can load DH parameters hardcoded into this file.
+ */
+static DH  *
+load_dh_buffer(const char *buffer, size_t len)
+{
+	BIO		   *bio;
+	DH		   *dh = NULL;
 
-	return 0;
+	bio = BIO_new_mem_buf((char *) buffer, len);
+	if (bio == NULL)
+		return NULL;
+	dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
+	if (dh == NULL)
+		ereport(DEBUG2,
+				(errmsg_internal("DH load buffer: %s",
+								 SSLerrmessage())));
+	BIO_free(bio);
+
+	return dh;
 }
 
 /*
- *	Close SSL connection.
+ *	Generate an ephemeral DH key.  Because this can take a long
+ *	time to compute, we can use precomputed parameters of the
+ *	common key sizes.
+ *
+ *	Since few sites will bother to precompute these parameter
+ *	files, we also provide a fallback to the parameters provided
+ *	by the OpenSSL project.
+ *
+ *	These values can be static (once loaded or computed) since
+ *	the OpenSSL library can efficiently generate random keys from
+ *	the information provided.
  */
-void
-be_tls_close(Port *port)
+static DH  *
+tmp_dh_cb(SSL *s, int is_export, int keylength)
 {
-	if (port->ssl)
-	{
-		SSL_shutdown(port->ssl);
-		SSL_free(port->ssl);
-		port->ssl = NULL;
-		port->ssl_in_use = false;
-	}
+	DH		   *r = NULL;
+	static DH  *dh = NULL;
+	static DH  *dh512 = NULL;
+	static DH  *dh1024 = NULL;
+	static DH  *dh2048 = NULL;
+	static DH  *dh4096 = NULL;
 
-	if (port->peer)
+	switch (keylength)
 	{
-		X509_free(port->peer);
-		port->peer = NULL;
+		case 512:
+			if (dh512 == NULL)
+				dh512 = load_dh_file(keylength);
+			if (dh512 == NULL)
+				dh512 = load_dh_buffer(file_dh512, sizeof file_dh512);
+			r = dh512;
+			break;
+
+		case 1024:
+			if (dh1024 == NULL)
+				dh1024 = load_dh_file(keylength);
+			if (dh1024 == NULL)
+				dh1024 = load_dh_buffer(file_dh1024, sizeof file_dh1024);
+			r = dh1024;
+			break;
+
+		case 2048:
+			if (dh2048 == NULL)
+				dh2048 = load_dh_file(keylength);
+			if (dh2048 == NULL)
+				dh2048 = load_dh_buffer(file_dh2048, sizeof file_dh2048);
+			r = dh2048;
+			break;
+
+		case 4096:
+			if (dh4096 == NULL)
+				dh4096 = load_dh_file(keylength);
+			if (dh4096 == NULL)
+				dh4096 = load_dh_buffer(file_dh4096, sizeof file_dh4096);
+			r = dh4096;
+			break;
+
+		default:
+			if (dh == NULL)
+				dh = load_dh_file(keylength);
+			r = dh;
 	}
 
-	if (port->peer_cn)
+	/* this may take a long time, but it may be necessary... */
+	if (r == NULL || 8 * DH_size(r) < keylength)
 	{
-		pfree(port->peer_cn);
-		port->peer_cn = NULL;
+		ereport(DEBUG2,
+				(errmsg_internal("DH: generating parameters (%d bits)",
+								 keylength)));
+		r = DH_generate_parameters(keylength, DH_GENERATOR_2, NULL, NULL);
 	}
+
+	return r;
 }
 
-ssize_t
-be_tls_read(Port *port, void *ptr, size_t len)
+/*
+ *	Certificate verification callback
+ *
+ *	This callback allows us to log intermediate problems during
+ *	verification, but for now we'll see if the final error message
+ *	contains enough information.
+ *
+ *	This callback also allows us to override the default acceptance
+ *	criteria (e.g., accepting self-signed or expired certs), but
+ *	for now we accept the default checks.
+ */
+static int
+verify_cb(int ok, X509_STORE_CTX *ctx)
 {
-	ssize_t		n;
-	int			err;
+	return ok;
+}
 
-rloop:
-	errno = 0;
-	n = SSL_read(port->ssl, ptr, len);
-	err = SSL_get_error(port->ssl, n);
-	switch (err)
+/*
+ *	This callback is used to copy SSL information messages
+ *	into the PostgreSQL log.
+ */
+static void
+info_cb(const SSL *ssl, int type, int args)
+{
+	switch (type)
 	{
-		case SSL_ERROR_NONE:
-			port->count += n;
+		case SSL_CB_HANDSHAKE_START:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: handshake start")));
 			break;
-		case SSL_ERROR_WANT_READ:
-		case SSL_ERROR_WANT_WRITE:
-			if (port->noblock)
-			{
-				errno = EWOULDBLOCK;
-				n = -1;
-				break;
-			}
-#ifdef WIN32
-			pgwin32_waitforsinglesocket(SSL_get_fd(port->ssl),
-										(err == SSL_ERROR_WANT_READ) ?
-									FD_READ | FD_CLOSE : FD_WRITE | FD_CLOSE,
-										INFINITE);
-#endif
-			goto rloop;
-		case SSL_ERROR_SYSCALL:
-			/* leave it to caller to ereport the value of errno */
-			if (n != -1)
-			{
-				errno = ECONNRESET;
-				n = -1;
-			}
+		case SSL_CB_HANDSHAKE_DONE:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: handshake done")));
 			break;
-		case SSL_ERROR_SSL:
-			ereport(COMMERROR,
-					(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					 errmsg("SSL error: %s", SSLerrmessage())));
-			/* fall through */
-		case SSL_ERROR_ZERO_RETURN:
-			errno = ECONNRESET;
-			n = -1;
+		case SSL_CB_ACCEPT_LOOP:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: accept loop")));
 			break;
-		default:
-			ereport(COMMERROR,
-					(errcode(ERRCODE_PROTOCOL_VIOLATION),
-					 errmsg("unrecognized SSL error code: %d",
-							err)));
-			errno = ECONNRESET;
-			n = -1;
+		case SSL_CB_ACCEPT_EXIT:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: accept exit (%d)", args)));
+			break;
+		case SSL_CB_CONNECT_LOOP:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: connect loop")));
+			break;
+		case SSL_CB_CONNECT_EXIT:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: connect exit (%d)", args)));
+			break;
+		case SSL_CB_READ_ALERT:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: read alert (0x%04x)", args)));
+			break;
+		case SSL_CB_WRITE_ALERT:
+			ereport(DEBUG4,
+					(errmsg_internal("SSL: write alert (0x%04x)", args)));
 			break;
 	}
+}
 
-	return n;
+static void
+initialize_ecdh(void)
+{
+#if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_ECDH)
+	EC_KEY	   *ecdh;
+	int			nid;
+
+	nid = OBJ_sn2nid(SSLECDHCurve);
+	if (!nid)
+		ereport(FATAL,
+				(errmsg("ECDH: unrecognized curve name: %s", SSLECDHCurve)));
+
+	ecdh = EC_KEY_new_by_curve_name(nid);
+	if (!ecdh)
+		ereport(FATAL,
+				(errmsg("ECDH: could not create key")));
+
+	SSL_CTX_set_options(SSL_context, SSL_OP_SINGLE_ECDH_USE);
+	SSL_CTX_set_tmp_ecdh(SSL_context, ecdh);
+	EC_KEY_free(ecdh);
+#endif
 }
 
 /*