Change default of password_encryption to scram-sha-256

Also, the legacy values on/true/yes/1 for password_encryption that
mapped to md5 are removed.  The only valid values are now
scram-sha-256 and md5.
Reviewed-by: Jonathan S. Katz <jkatz@postgresql.org>
Discussion: https://www.postgresql.org/message-id/flat/d5b0ad33-7d94-bdd1-caac-43a1c782cab2%402ndquadrant.com

doc/src/sgml/config.sgml

@@ -1013,11 +1013,11 @@ include_dir 'conf.d'
       <listitem>
        <para>
         When a password is specified in <xref linkend="sql-createrole"/> or
-        <xref linkend="sql-alterrole"/>, this parameter determines the algorithm
-        to use to encrypt the password. The default value is <literal>md5</literal>,
-        which stores the password as an MD5 hash (<literal>on</literal> is also
-        accepted, as alias for <literal>md5</literal>). Setting this parameter to
-        <literal>scram-sha-256</literal> will encrypt the password with SCRAM-SHA-256.
+        <xref linkend="sql-alterrole"/>, this parameter determines the
+        algorithm to use to encrypt the password.  Possible values are
+        <literal>scram-sha-256</literal>, which will encrypt the password with
+        SCRAM-SHA-256, and <literal>md5</literal>, which stores the password
+        as an MD5 hash.  The default is <literal>scram-sha-256</literal>.
        </para>
        <para>
         Note that older clients might lack support for the SCRAM authentication

src/backend/commands/user.c

@@ -43,7 +43,7 @@ Oid			binary_upgrade_next_pg_authid_oid = InvalidOid;
 
 
 /* GUC parameter */
-int			Password_encryption = PASSWORD_TYPE_MD5;
+int			Password_encryption = PASSWORD_TYPE_SCRAM_SHA_256;
 
 /* Hook to check passwords in CreateRole() and AlterRole() */
 check_password_hook_type check_password_hook = NULL;

src/backend/utils/misc/guc.c

@@ -463,18 +463,9 @@ static const struct config_enum_entry plan_cache_mode_options[] = {
 	{NULL, 0, false}
 };
 
-/*
- * password_encryption used to be a boolean, so accept all the likely
- * variants of "on", too. "off" used to store passwords in plaintext,
- * but we don't support that anymore.
- */
 static const struct config_enum_entry password_encryption_options[] = {
 	{"md5", PASSWORD_TYPE_MD5, false},
 	{"scram-sha-256", PASSWORD_TYPE_SCRAM_SHA_256, false},
-	{"on", PASSWORD_TYPE_MD5, true},
-	{"true", PASSWORD_TYPE_MD5, true},
-	{"yes", PASSWORD_TYPE_MD5, true},
-	{"1", PASSWORD_TYPE_MD5, true},
 	{NULL, 0, false}
 };
 
@@ -4733,7 +4724,7 @@ static struct config_enum ConfigureNamesEnum[] =
 			NULL
 		},
 		&Password_encryption,
-		PASSWORD_TYPE_MD5, password_encryption_options,
+		PASSWORD_TYPE_SCRAM_SHA_256, password_encryption_options,
 		NULL, NULL, NULL
 	},
 

src/backend/utils/misc/postgresql.conf.sample

@@ -88,7 +88,7 @@
 # - Authentication -
 
 #authentication_timeout = 1min		# 1s-600s
-#password_encryption = md5		# md5 or scram-sha-256
+#password_encryption = scram-sha-256	# scram-sha-256 or md5
 #db_user_namespace = off
 
 # GSSAPI using Kerberos

src/bin/initdb/initdb.c

@@ -1204,12 +1204,18 @@ setup_config(void)
 							  "#update_process_title = off");
 #endif
 
-	if (strcmp(authmethodlocal, "scram-sha-256") == 0 ||
-		strcmp(authmethodhost, "scram-sha-256") == 0)
+	/*
+	 * Change password_encryption setting to md5 if md5 was chosen as an
+	 * authentication method, unless scram-sha-256 was also chosen.
+	 */
+	if ((strcmp(authmethodlocal, "md5") == 0 &&
+		 strcmp(authmethodhost, "scram-sha-256") != 0) ||
+		(strcmp(authmethodhost, "md5") == 0 &&
+		 strcmp(authmethodlocal, "scram-sha-256") != 0))
 	{
 		conflines = replace_token(conflines,
-								  "#password_encryption = md5",
-								  "password_encryption = scram-sha-256");
+								  "#password_encryption = scram-sha-256",
+								  "password_encryption = md5");
 	}
 
 	/*
@@ -2373,12 +2379,7 @@ check_need_password(const char *authmethodlocal, const char *authmethodhost)
 		 strcmp(authmethodhost, "scram-sha-256") == 0) &&
 		!(pwprompt || pwfilename))
 	{
-		pg_log_error("must specify a password for the superuser to enable %s authentication",
-					 (strcmp(authmethodlocal, "md5") == 0 ||
-					  strcmp(authmethodlocal, "password") == 0 ||
-					  strcmp(authmethodlocal, "scram-sha-256") == 0)
-					 ? authmethodlocal
-					 : authmethodhost);
+		pg_log_error("must specify a password for the superuser to enable password authentication");
 		exit(1);
 	}
 }

src/test/regress/expected/password.out

@@ -5,13 +5,14 @@
 SET password_encryption = 'novalue'; -- error
 ERROR:  invalid value for parameter "password_encryption": "novalue"
 HINT:  Available values: md5, scram-sha-256.
-SET password_encryption = true; -- ok
+SET password_encryption = true; -- error
+ERROR:  invalid value for parameter "password_encryption": "true"
+HINT:  Available values: md5, scram-sha-256.
 SET password_encryption = 'md5'; -- ok
 SET password_encryption = 'scram-sha-256'; -- ok
 -- consistency of password entries
 SET password_encryption = 'md5';
 CREATE ROLE regress_passwd1 PASSWORD 'role_pwd1';
-SET password_encryption = 'on';
 CREATE ROLE regress_passwd2 PASSWORD 'role_pwd2';
 SET password_encryption = 'scram-sha-256';
 CREATE ROLE regress_passwd3 PASSWORD 'role_pwd3';

src/test/regress/sql/password.sql

@@ -4,14 +4,13 @@
 
 -- Tests for GUC password_encryption
 SET password_encryption = 'novalue'; -- error
-SET password_encryption = true; -- ok
+SET password_encryption = true; -- error
 SET password_encryption = 'md5'; -- ok
 SET password_encryption = 'scram-sha-256'; -- ok
 
 -- consistency of password entries
 SET password_encryption = 'md5';
 CREATE ROLE regress_passwd1 PASSWORD 'role_pwd1';
-SET password_encryption = 'on';
 CREATE ROLE regress_passwd2 PASSWORD 'role_pwd2';
 SET password_encryption = 'scram-sha-256';
 CREATE ROLE regress_passwd3 PASSWORD 'role_pwd3';