Revert "Add GUC checks for ssl_min_protocol_version and ssl_max_protocol_version"

This reverts commit 41aadeeb, as the GUC checks could run on older values
with the new values used, and result in incorrect errors if both
parameters are changed at the same time.

Per complaint from Tom Lane.

Discussion: https://postgr.es/m/27574.1581015893@sss.pgh.pa.us
Backpatch-through: 12

src/backend/utils/misc/guc.c

@@ -205,10 +205,6 @@ static const char *show_log_file_mode(void);
 static const char *show_data_directory_mode(void);
 static bool check_backtrace_functions(char **newval, void **extra, GucSource source);
 static void assign_backtrace_functions(const char *newval, void *extra);
-static bool check_ssl_min_protocol_version(int *newval, void **extra,
-										   GucSource source);
-static bool check_ssl_max_protocol_version(int *newval, void **extra,
-										   GucSource source);
 static bool check_recovery_target_timeline(char **newval, void **extra, GucSource source);
 static void assign_recovery_target_timeline(const char *newval, void *extra);
 static bool check_recovery_target(char **newval, void **extra, GucSource source);
@@ -4657,7 +4653,7 @@ static struct config_enum ConfigureNamesEnum[] =
 		&ssl_min_protocol_version,
 		PG_TLS1_2_VERSION,
 		ssl_protocol_versions_info + 1, /* don't allow PG_TLS_ANY */
-		check_ssl_min_protocol_version, NULL, NULL
+		NULL, NULL, NULL
 	},
 
 	{
@@ -4669,7 +4665,7 @@ static struct config_enum ConfigureNamesEnum[] =
 		&ssl_max_protocol_version,
 		PG_TLS_ANY,
 		ssl_protocol_versions_info,
-		check_ssl_max_protocol_version, NULL, NULL
+		NULL, NULL, NULL
 	},
 
 	/* End-of-list marker */
@@ -11642,49 +11638,6 @@ assign_backtrace_functions(const char *newval, void *extra)
 	backtrace_symbol_list = (char *) extra;
 }
 
-static bool
-check_ssl_min_protocol_version(int *newval, void **extra, GucSource source)
-{
-	int			new_ssl_min_protocol_version = *newval;
-
-	/* PG_TLS_ANY is not supported for the minimum bound */
-	Assert(new_ssl_min_protocol_version > PG_TLS_ANY);
-
-	if (ssl_max_protocol_version &&
-		new_ssl_min_protocol_version > ssl_max_protocol_version)
-	{
-		GUC_check_errhint("\"%s\" cannot be higher than \"%s\".",
-						  "ssl_min_protocol_version",
-						  "ssl_max_protocol_version");
-		GUC_check_errcode(ERRCODE_INVALID_PARAMETER_VALUE);
-		return false;
-	}
-
-	return true;
-}
-
-static bool
-check_ssl_max_protocol_version(int *newval, void **extra, GucSource source)
-{
-	int			new_ssl_max_protocol_version = *newval;
-
-	/* if PG_TLS_ANY, there is no need to check the bounds */
-	if (new_ssl_max_protocol_version == PG_TLS_ANY)
-		return true;
-
-	if (ssl_min_protocol_version &&
-		ssl_min_protocol_version > new_ssl_max_protocol_version)
-	{
-		GUC_check_errhint("\"%s\" cannot be lower than \"%s\".",
-						  "ssl_max_protocol_version",
-						  "ssl_min_protocol_version");
-		GUC_check_errcode(ERRCODE_INVALID_PARAMETER_VALUE);
-		return false;
-	}
-
-	return true;
-}
-
 static bool
 check_recovery_target_timeline(char **newval, void **extra, GucSource source)
 {

src/test/ssl/t/001_ssltests.pl

@@ -13,7 +13,7 @@ use SSLServer;
 
 if ($ENV{with_openssl} eq 'yes')
 {
-	plan tests => 93;
+	plan tests => 91;
 }
 else
 {
@@ -97,24 +97,6 @@ command_ok(
 	'restart succeeds with password-protected key file');
 $node->_update_pid(1);
 
-# Test compatibility of SSL protocols.
-# TLSv1.1 is lower than TLSv1.2, so it won't work.
-$node->append_conf(
-	'postgresql.conf',
-	qq{ssl_min_protocol_version='TLSv1.2'
-ssl_max_protocol_version='TLSv1.1'});
-command_fails(
-	[ 'pg_ctl', '-D', $node->data_dir, '-l', $node->logfile, 'restart' ],
-	'restart fails with incorrect SSL protocol bounds');
-# Go back to the defaults, this works.
-$node->append_conf(
-	'postgresql.conf',
-	qq{ssl_min_protocol_version='TLSv1.2'
-ssl_max_protocol_version=''});
-command_ok(
-	[ 'pg_ctl', '-D', $node->data_dir, '-l', $node->logfile, 'restart' ],
-	'restart succeeds with correct SSL protocol bounds');
-
 ### Run client-side tests.
 ###
 ### Test that libpq accepts/rejects the connection correctly, depending