Move OpenSSL routines for min/max protocol setting to src/common/

Two routines have been added in OpenSSL 1.1.0 to set the protocol bounds
allowed within a given SSL context:
- SSL_CTX_set_min_proto_version
- SSL_CTX_set_max_proto_version

As Postgres supports OpenSSL down to 1.0.1 (as of HEAD), equivalent
replacements exist in the tree, which are only available for the
backend.  A follow-up patch is planned to add control of the SSL
protocol bounds for libpq, so move those routines to src/common/ so as
libpq can use them.

Author: Daniel Gustafsson
Discussion: https://postgr.es/m/4F246AE3-A7AE-471E-BD3D-C799D3748E03@yesql.se

1 files changed, 117 insertions, 0 deletions

diff --git a/src/common/protocol_openssl.c b/src/common/protocol_openssl.c
new file mode 100644
index 00000000000..bf6c62410da
--- /dev/null
+++ b/src/common/protocol_openssl.c
@@ -0,0 +1,117 @@
+/*-------------------------------------------------------------------------
+ *
+ * protocol_openssl.c
+ *	  OpenSSL functionality shared between frontend and backend
+ *
+ * This should only be used if code is compiled with OpenSSL support.
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *		  src/common/protocol_openssl.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
+
+#include "common/openssl.h"
+
+/*
+ * Replacements for APIs introduced in OpenSSL 1.1.0.
+ */
+#ifndef SSL_CTX_set_min_proto_version
+
+/*
+ * OpenSSL versions that support TLS 1.3 shouldn't get here because they
+ * already have these functions.  So we don't have to keep updating the below
+ * code for every new TLS version, and eventually it can go away.  But let's
+ * just check this to make sure ...
+ */
+#ifdef TLS1_3_VERSION
+#error OpenSSL version mismatch
+#endif
+
+int
+SSL_CTX_set_min_proto_version(SSL_CTX *ctx, int version)
+{
+	int			ssl_options = SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3;
+
+	if (version > TLS1_VERSION)
+		ssl_options |= SSL_OP_NO_TLSv1;
+
+	/*
+	 * Some OpenSSL versions define TLS*_VERSION macros but not the
+	 * corresponding SSL_OP_NO_* macro, so in those cases we have to return
+	 * unsuccessfully here.
+	 */
+#ifdef TLS1_1_VERSION
+	if (version > TLS1_1_VERSION)
+	{
+#ifdef SSL_OP_NO_TLSv1_1
+		ssl_options |= SSL_OP_NO_TLSv1_1;
+#else
+		return 0;
+#endif
+	}
+#endif
+#ifdef TLS1_2_VERSION
+	if (version > TLS1_2_VERSION)
+	{
+#ifdef SSL_OP_NO_TLSv1_2
+		ssl_options |= SSL_OP_NO_TLSv1_2;
+#else
+		return 0;
+#endif
+	}
+#endif
+
+	SSL_CTX_set_options(ctx, ssl_options);
+
+	return 1;					/* success */
+}
+
+int
+SSL_CTX_set_max_proto_version(SSL_CTX *ctx, int version)
+{
+	int			ssl_options = 0;
+
+	AssertArg(version != 0);
+
+	/*
+	 * Some OpenSSL versions define TLS*_VERSION macros but not the
+	 * corresponding SSL_OP_NO_* macro, so in those cases we have to return
+	 * unsuccessfully here.
+	 */
+#ifdef TLS1_1_VERSION
+	if (version < TLS1_1_VERSION)
+	{
+#ifdef SSL_OP_NO_TLSv1_1
+		ssl_options |= SSL_OP_NO_TLSv1_1;
+#else
+		return 0;
+#endif
+	}
+#endif
+#ifdef TLS1_2_VERSION
+	if (version < TLS1_2_VERSION)
+	{
+#ifdef SSL_OP_NO_TLSv1_2
+		ssl_options |= SSL_OP_NO_TLSv1_2;
+#else
+		return 0;
+#endif
+	}
+#endif
+
+	SSL_CTX_set_options(ctx, ssl_options);
+
+	return 1;					/* success */
+}
+
+#endif							/* !SSL_CTX_set_min_proto_version */