Add GUC checks for ssl_min_protocol_version and ssl_max_protocol_version

Mixing incorrect bounds set in the SSL context leads to confusing error
messages generated by OpenSSL which are hard to act on.  New checks are
added within the GUC machinery to improve the user experience as they
apply to any SSL implementation, not only OpenSSL, and doing the checks
beforehand avoids the creation of a SSL during a reload (or startup)
which we know will never be used anyway.

Backpatch down to 12, as those parameters have been introduced by
e73e67c.

Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20200114035420.GE1515@paquier.xyz
Backpatch-through: 12

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index e5f8a1301faa3a33f1461029131245792466bd7b..e44f71e99109be44c37db7428f59f9d6b7277923 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -204,6 +204,10 @@ 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);
@@ -4594,7 +4598,7 @@ static struct config_enum ConfigureNamesEnum[] =
        &ssl_min_protocol_version,
        PG_TLS1_2_VERSION,
        ssl_protocol_versions_info + 1, /* don't allow PG_TLS_ANY */
-       NULL, NULL, NULL
+       check_ssl_min_protocol_version, NULL, NULL
    },
 
    {
@@ -4606,7 +4610,7 @@ static struct config_enum ConfigureNamesEnum[] =
        &ssl_max_protocol_version,
        PG_TLS_ANY,
        ssl_protocol_versions_info,
-       NULL, NULL, NULL
+       check_ssl_max_protocol_version, NULL, NULL
    },
 
    /* End-of-list marker */
@@ -11603,6 +11607,49 @@ 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)
 {

diff --git a/src/test/ssl/t/001_ssltests.pl b/src/test/ssl/t/001_ssltests.pl
index 83fcd5e839a2510c3d8b042635b9964bdc869b88..7b18402cf637f0d3e9f134ce60e5563c5801a93e 100644 (file)
--- a/src/test/ssl/t/001_ssltests.pl
+++ b/src/test/ssl/t/001_ssltests.pl
@@ -13,7 +13,7 @@ use SSLServer;
 
 if ($ENV{with_openssl} eq 'yes')
 {
-   plan tests => 84;
+   plan tests => 86;
 }
 else
 {
@@ -97,6 +97,24 @@ 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