Set libcrypto callbacks for all connection threads in libpq

Based on an analysis of the OpenSSL code with Jacob, moving to EVP for
the cryptohash computations makes necessary the setup of the libcrypto
callbacks that were getting set only for SSL connections, but not for
connections without SSL.  Not setting the callbacks makes the use of
threads potentially unsafe for connections calling cryptohashes during
authentication, like MD5 or SCRAM, if a failure happens during a
cryptohash computation.  The logic setting the libssl and libcrypto
states is then split into two parts, both using the same locking, with
libcrypto being set up for SSL and non-SSL connections, while SSL
connections set any libssl state afterwards as needed.

Prior to this commit, only SSL connections would have set libcrypto
callbacks that are necessary to ensure a proper thread locking when
using multiple concurrent threads in libpq (ENABLE_THREAD_SAFETY).  Note
that this is only required for OpenSSL 1.0.2 and 1.0.1 (oldest version
supported on HEAD), as 1.1.0 has its own internal locking and it has
dropped support for CRYPTO_set_locking_callback().

Tests with up to 300 threads with OpenSSL 1.0.1 and 1.0.2, mixing SSL
and non-SSL connection threads did not show any performance impact after
some micro-benchmarking.  pgbench can be used here with -C and a
mostly-empty script (with one \set meta-command for example) to stress
authentication requests, and we have mixed that with some custom
programs for testing.

Reported-by: Jacob Champion
Author: Michael Paquier
Reviewed-by: Jacob Champion
Discussion: https://postgr.es/m/fd3ba610085f1ff54623478cf2f7adf5af193cbb.camel@vmware.com

src/interfaces/libpq/fe-connect.c

@@ -2887,6 +2887,16 @@ keep_going:						/* We will come back to here until there is
 
 #ifdef USE_SSL
 
+				/*
+				 * Enable the libcrypto callbacks before checking if SSL needs
+				 * to be done.  This is done before sending the startup packet
+				 * as depending on the type of authentication done, like MD5
+				 * or SCRAM that use cryptohashes, the callbacks would be
+				 * required even without a SSL connection
+				 */
+				if (pqsecure_initialize(conn, false, true) < 0)
+					goto error_return;
+
 				/*
 				 * If SSL is enabled and we haven't already got encryption of
 				 * some sort running, request SSL instead of sending the
@@ -2998,8 +3008,14 @@ keep_going:						/* We will come back to here until there is
 					{
 						/* mark byte consumed */
 						conn->inStart = conn->inCursor;
-						/* Set up global SSL state if required */
-						if (pqsecure_initialize(conn) != 0)
+
+						/*
+						 * Set up global SSL state if required.  The crypto
+						 * state has already been set if libpq took care of
+						 * doing that, so there is no need to make that happen
+						 * again.
+						 */
+						if (pqsecure_initialize(conn, true, false) != 0)
 							goto error_return;
 					}
 					else if (SSLok == 'N')

src/interfaces/libpq/fe-secure-openssl.c

@@ -85,7 +85,7 @@ static bool pq_init_crypto_lib = true;
 static bool ssl_lib_initialized = false;
 
 #ifdef ENABLE_THREAD_SAFETY
-static long ssl_open_connections = 0;
+static long crypto_open_connections = 0;
 
 #ifndef WIN32
 static pthread_mutex_t ssl_config_mutex = PTHREAD_MUTEX_INITIALIZER;
@@ -111,7 +111,7 @@ pgtls_init_library(bool do_ssl, int do_crypto)
 	 * Disallow changing the flags while we have open connections, else we'd
 	 * get completely confused.
 	 */
-	if (ssl_open_connections != 0)
+	if (crypto_open_connections != 0)
 		return;
 #endif
 
@@ -635,7 +635,7 @@ pq_lockingcallback(int mode, int n, const char *file, int line)
  * override it.
  */
 int
-pgtls_init(PGconn *conn)
+pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto)
 {
 #ifdef ENABLE_THREAD_SAFETY
 #ifdef WIN32
@@ -684,22 +684,28 @@ pgtls_init(PGconn *conn)
 			}
 		}
 
-		if (ssl_open_connections++ == 0)
+		if (do_crypto && !conn->crypto_loaded)
 		{
-			/*
-			 * These are only required for threaded libcrypto applications,
-			 * but make sure we don't stomp on them if they're already set.
-			 */
-			if (CRYPTO_get_id_callback() == NULL)
-				CRYPTO_set_id_callback(pq_threadidcallback);
-			if (CRYPTO_get_locking_callback() == NULL)
-				CRYPTO_set_locking_callback(pq_lockingcallback);
+			if (crypto_open_connections++ == 0)
+			{
+				/*
+				 * These are only required for threaded libcrypto
+				 * applications, but make sure we don't stomp on them if
+				 * they're already set.
+				 */
+				if (CRYPTO_get_id_callback() == NULL)
+					CRYPTO_set_id_callback(pq_threadidcallback);
+				if (CRYPTO_get_locking_callback() == NULL)
+					CRYPTO_set_locking_callback(pq_lockingcallback);
+			}
+
+			conn->crypto_loaded = true;
 		}
 	}
 #endif							/* HAVE_CRYPTO_LOCK */
 #endif							/* ENABLE_THREAD_SAFETY */
 
-	if (!ssl_lib_initialized)
+	if (!ssl_lib_initialized && do_ssl)
 	{
 		if (pq_init_ssl_lib)
 		{
@@ -740,10 +746,10 @@ destroy_ssl_system(void)
 	if (pthread_mutex_lock(&ssl_config_mutex))
 		return;
 
-	if (pq_init_crypto_lib && ssl_open_connections > 0)
-		--ssl_open_connections;
+	if (pq_init_crypto_lib && crypto_open_connections > 0)
+		--crypto_open_connections;
 
-	if (pq_init_crypto_lib && ssl_open_connections == 0)
+	if (pq_init_crypto_lib && crypto_open_connections == 0)
 	{
 		/*
 		 * No connections left, unregister libcrypto callbacks, if no one
@@ -1402,46 +1408,63 @@ pgtls_close(PGconn *conn)
 {
 	bool		destroy_needed = false;
 
-	if (conn->ssl)
+	if (conn->ssl_in_use)
 	{
-		/*
-		 * We can't destroy everything SSL-related here due to the possible
-		 * later calls to OpenSSL routines which may need our thread
-		 * callbacks, so set a flag here and check at the end.
-		 */
-		destroy_needed = true;
+		if (conn->ssl)
+		{
+			/*
+			 * We can't destroy everything SSL-related here due to the
+			 * possible later calls to OpenSSL routines which may need our
+			 * thread callbacks, so set a flag here and check at the end.
+			 */
 
-		SSL_shutdown(conn->ssl);
-		SSL_free(conn->ssl);
-		conn->ssl = NULL;
-		conn->ssl_in_use = false;
-	}
+			SSL_shutdown(conn->ssl);
+			SSL_free(conn->ssl);
+			conn->ssl = NULL;
+			conn->ssl_in_use = false;
 
-	if (conn->peer)
-	{
-		X509_free(conn->peer);
-		conn->peer = NULL;
-	}
+			destroy_needed = true;
+		}
+
+		if (conn->peer)
+		{
+			X509_free(conn->peer);
+			conn->peer = NULL;
+		}
 
 #ifdef USE_SSL_ENGINE
-	if (conn->engine)
-	{
-		ENGINE_finish(conn->engine);
-		ENGINE_free(conn->engine);
-		conn->engine = NULL;
-	}
+		if (conn->engine)
+		{
+			ENGINE_finish(conn->engine);
+			ENGINE_free(conn->engine);
+			conn->engine = NULL;
+		}
 #endif
+	}
+	else
+	{
+		/*
+		 * In the non-SSL case, just remove the crypto callbacks if the
+		 * connection has then loaded.  This code path has no dependency
+		 * on any pending SSL calls.
+		 */
+		if (conn->crypto_loaded)
+			destroy_needed = true;
+	}
 
 	/*
-	 * This will remove our SSL locking hooks, if this is the last SSL
-	 * connection, which means we must wait to call it until after all SSL
-	 * calls have been made, otherwise we can end up with a race condition and
-	 * possible deadlocks.
+	 * This will remove our crypto locking hooks if this is the last
+	 * connection using libcrypto which means we must wait to call it until
+	 * after all the potential SSL calls have been made, otherwise we can end
+	 * up with a race condition and possible deadlocks.
 	 *
 	 * See comments above destroy_ssl_system().
 	 */
 	if (destroy_needed)
+	{
 		destroy_ssl_system();
+		conn->crypto_loaded = false;
+	}
 }
 
 

src/interfaces/libpq/fe-secure.c

@@ -159,12 +159,12 @@ PQinitOpenSSL(int do_ssl, int do_crypto)
  *	Initialize global SSL context
  */
 int
-pqsecure_initialize(PGconn *conn)
+pqsecure_initialize(PGconn *conn, bool do_ssl, bool do_crypto)
 {
 	int			r = 0;
 
 #ifdef USE_SSL
-	r = pgtls_init(conn);
+	r = pgtls_init(conn, do_ssl, do_crypto);
 #endif
 
 	return r;
@@ -191,8 +191,7 @@ void
 pqsecure_close(PGconn *conn)
 {
 #ifdef USE_SSL
-	if (conn->ssl_in_use)
-		pgtls_close(conn);
+	pgtls_close(conn);
 #endif
 }
 

src/interfaces/libpq/libpq-int.h

@@ -486,6 +486,11 @@ struct pg_conn
 	void	   *engine;			/* dummy field to keep struct the same if
 								 * OpenSSL version changes */
 #endif
+	bool		crypto_loaded;	/* Track if libcrypto locking callbacks have
+								 * been done for this connection. This can be
+								 * removed once support for OpenSSL 1.0.2 is
+								 * removed as this locking is handled
+								 * internally in OpenSSL >= 1.1.0. */
 #endif							/* USE_OPENSSL */
 #endif							/* USE_SSL */
 
@@ -667,7 +672,7 @@ extern int	pqWriteReady(PGconn *conn);
 
 /* === in fe-secure.c === */
 
-extern int	pqsecure_initialize(PGconn *);
+extern int	pqsecure_initialize(PGconn *, bool, bool);
 extern PostgresPollingStatusType pqsecure_open_client(PGconn *);
 extern void pqsecure_close(PGconn *);
 extern ssize_t pqsecure_read(PGconn *, void *ptr, size_t len);
@@ -696,11 +701,13 @@ extern void pgtls_init_library(bool do_ssl, int do_crypto);
  * Initialize SSL library.
  *
  * The conn parameter is only used to be able to pass back an error
- * message - no connection-local setup is made here.
+ * message - no connection-local setup is made here.  do_ssl controls
+ * if SSL is initialized, and do_crypto does the same for the crypto
+ * part.
  *
  * Returns 0 if OK, -1 on failure (adding a message to conn->errorMessage).
  */
-extern int	pgtls_init(PGconn *conn);
+extern int	pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto);
 
 /*
  *	Begin or continue negotiating a secure session.