Turn password_encryption GUC into an enum.

This makes the parameter easier to extend, to support other password-based
authentication protocols than MD5. (SCRAM is being worked on.)

The GUC still accepts on/off as aliases for "md5" and "plain", although
we may want to remove those once we actually add support for another
password hash type.

Michael Paquier, reviewed by David Steele, with some further edits by me.

Discussion: <CAB7nPqSMXU35g=W9X74HVeQp0uvgJxvYOuA4A-A3M+0wfEBv-w@mail.gmail.com>

5 files changed, 62 insertions, 34 deletions

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index a848a7edd11..e826c19698c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1163,21 +1163,22 @@ include_dir 'conf.d'
      </varlistentry>
 
      <varlistentry id="guc-password-encryption" xreflabel="password_encryption">
-      <term><varname>password_encryption</varname> (<type>boolean</type>)
+      <term><varname>password_encryption</varname> (<type>enum</type>)
       <indexterm>
        <primary><varname>password_encryption</> configuration parameter</primary>
       </indexterm>
       </term>
       <listitem>
        <para>
-        When a password is specified in <xref
-        linkend="sql-createuser"> or
-        <xref linkend="sql-alterrole">
-        without writing either <literal>ENCRYPTED</> or
-        <literal>UNENCRYPTED</>, this parameter determines whether the
-        password is to be encrypted. The default is <literal>on</>
-        (encrypt the password).
+        When a password is specified in <xref linkend="sql-createuser"> or
+        <xref linkend="sql-alterrole"> without writing either <literal>ENCRYPTED</>
+        or <literal>UNENCRYPTED</>, this parameter determines whether the
+        password is to be encrypted. The default value is <literal>md5</>, which
+        stores the password as an MD5 hash. Setting this to <literal>plain</> stores
+        it in plaintext. <literal>on</> and <literal>off</> are also accepted, as
+        aliases for <literal>md5</> and <literal>plain</>, respectively.
        </para>
+       
       </listitem>
      </varlistentry>
 
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index 4027c89b143..adc6b99b215 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -44,7 +44,7 @@ Oid			binary_upgrade_next_pg_authid_oid = InvalidOid;
 
 
 /* GUC parameter */
-extern bool Password_encryption;
+int			Password_encryption = PASSWORD_TYPE_MD5;
 
 /* Hook to check passwords in CreateRole() and AlterRole() */
 check_password_hook_type check_password_hook = NULL;
@@ -80,7 +80,7 @@ CreateRole(ParseState *pstate, CreateRoleStmt *stmt)
 	ListCell   *item;
 	ListCell   *option;
 	char	   *password = NULL;	/* user password */
-	bool		encrypt_password = Password_encryption; /* encrypt password? */
+	int			password_type = Password_encryption;
 	char		encrypted_password[MD5_PASSWD_LEN + 1];
 	bool		issuper = false;	/* Make the user a superuser? */
 	bool		inherit = true; /* Auto inherit privileges? */
@@ -140,9 +140,9 @@ CreateRole(ParseState *pstate, CreateRoleStmt *stmt)
 						 parser_errposition(pstate, defel->location)));
 			dpassword = defel;
 			if (strcmp(defel->defname, "encryptedPassword") == 0)
-				encrypt_password = true;
+				password_type = PASSWORD_TYPE_MD5;
 			else if (strcmp(defel->defname, "unencryptedPassword") == 0)
-				encrypt_password = false;
+				password_type = PASSWORD_TYPE_PLAINTEXT;
 		}
 		else if (strcmp(defel->defname, "sysid") == 0)
 		{
@@ -393,7 +393,7 @@ CreateRole(ParseState *pstate, CreateRoleStmt *stmt)
 
 	if (password)
 	{
-		if (!encrypt_password || isMD5(password))
+		if (password_type == PASSWORD_TYPE_PLAINTEXT || isMD5(password))
 			new_record[Anum_pg_authid_rolpassword - 1] =
 				CStringGetTextDatum(password);
 		else
@@ -505,7 +505,7 @@ AlterRole(AlterRoleStmt *stmt)
 	ListCell   *option;
 	char	   *rolename = NULL;
 	char	   *password = NULL;	/* user password */
-	bool		encrypt_password = Password_encryption; /* encrypt password? */
+	int			password_type = Password_encryption;
 	char		encrypted_password[MD5_PASSWD_LEN + 1];
 	int			issuper = -1;	/* Make the user a superuser? */
 	int			inherit = -1;	/* Auto inherit privileges? */
@@ -550,9 +550,9 @@ AlterRole(AlterRoleStmt *stmt)
 						 errmsg("conflicting or redundant options")));
 			dpassword = defel;
 			if (strcmp(defel->defname, "encryptedPassword") == 0)
-				encrypt_password = true;
+				password_type = PASSWORD_TYPE_MD5;
 			else if (strcmp(defel->defname, "unencryptedPassword") == 0)
-				encrypt_password = false;
+				password_type = PASSWORD_TYPE_PLAINTEXT;
 		}
 		else if (strcmp(defel->defname, "superuser") == 0)
 		{
@@ -804,7 +804,7 @@ AlterRole(AlterRoleStmt *stmt)
 	/* password */
 	if (password)
 	{
-		if (!encrypt_password || isMD5(password))
+		if (password_type == PASSWORD_TYPE_PLAINTEXT || isMD5(password))
 			new_record[Anum_pg_authid_rolpassword - 1] =
 				CStringGetTextDatum(password);
 		else
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ce4eef950b4..cced814d6ab 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -34,6 +34,7 @@
 #include "catalog/namespace.h"
 #include "commands/async.h"
 #include "commands/prepare.h"
+#include "commands/user.h"
 #include "commands/vacuum.h"
 #include "commands/variable.h"
 #include "commands/trigger.h"
@@ -394,6 +395,24 @@ static const struct config_enum_entry force_parallel_mode_options[] = {
 };
 
 /*
+ * password_encryption used to be a boolean, so accept all the likely
+ * variants of "on" and "off", too.
+ */
+static const struct config_enum_entry password_encryption_options[] = {
+	{"plain", PASSWORD_TYPE_PLAINTEXT, false},
+	{"md5", PASSWORD_TYPE_MD5, false},
+	{"off", PASSWORD_TYPE_PLAINTEXT, false},
+	{"on", PASSWORD_TYPE_MD5, false},
+	{"true", PASSWORD_TYPE_MD5, true},
+	{"false", PASSWORD_TYPE_PLAINTEXT, true},
+	{"yes", PASSWORD_TYPE_MD5, true},
+	{"no", PASSWORD_TYPE_PLAINTEXT, true},
+	{"1", PASSWORD_TYPE_MD5, true},
+	{"0", PASSWORD_TYPE_PLAINTEXT, true},
+	{NULL, 0, false}
+};
+
+/*
  * Options for enum values stored in other modules
  */
 extern const struct config_enum_entry wal_level_options[];
@@ -423,8 +442,6 @@ bool		check_function_bodies = true;
 bool		default_with_oids = false;
 bool		SQL_inheritance = true;
 
-bool		Password_encryption = true;
-
 int			log_min_error_statement = ERROR;
 int			log_min_messages = WARNING;
 int			client_min_messages = NOTICE;
@@ -1314,17 +1331,6 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 	{
-		{"password_encryption", PGC_USERSET, CONN_AUTH_SECURITY,
-			gettext_noop("Encrypt passwords."),
-			gettext_noop("When a password is specified in CREATE USER or "
-			   "ALTER USER without writing either ENCRYPTED or UNENCRYPTED, "
-						 "this parameter determines whether the password is to be encrypted.")
-		},
-		&Password_encryption,
-		true,
-		NULL, NULL, NULL
-	},
-	{
 		{"transform_null_equals", PGC_USERSET, COMPAT_OPTIONS_CLIENT,
 			gettext_noop("Treats \"expr=NULL\" as \"expr IS NULL\"."),
 			gettext_noop("When turned on, expressions of the form expr = NULL "
@@ -3810,6 +3816,18 @@ static struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"password_encryption", PGC_USERSET, CONN_AUTH_SECURITY,
+			gettext_noop("Encrypt passwords."),
+			gettext_noop("When a password is specified in CREATE USER or "
+			   "ALTER USER without writing either ENCRYPTED or UNENCRYPTED, "
+						 "this parameter determines whether the password is to be encrypted.")
+		},
+		&Password_encryption,
+		PASSWORD_TYPE_MD5, password_encryption_options,
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, 0, NULL, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index b1c3aea9ee0..05b1373594b 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -85,7 +85,7 @@
 #ssl_key_file = 'server.key'		# (change requires restart)
 #ssl_ca_file = ''			# (change requires restart)
 #ssl_crl_file = ''			# (change requires restart)
-#password_encryption = on
+#password_encryption = md5		# md5 or plain
 #db_user_namespace = off
 #row_security = on
 
diff --git a/src/include/commands/user.h b/src/include/commands/user.h
index 1f0cfcc86f9..102c2a5861f 100644
--- a/src/include/commands/user.h
+++ b/src/include/commands/user.h
@@ -16,10 +16,19 @@
 #include "parser/parse_node.h"
 
 
-/* Hook to check passwords in CreateRole() and AlterRole() */
-#define PASSWORD_TYPE_PLAINTEXT		0
-#define PASSWORD_TYPE_MD5			1
+/*
+ * Types of password, for Password_encryption GUC and the password_type
+ * argument of the check-password hook.
+ */
+typedef enum PasswordType
+{
+	PASSWORD_TYPE_PLAINTEXT = 0,
+	PASSWORD_TYPE_MD5
+} PasswordType;
 
+extern int	Password_encryption;	/* GUC */
+
+/* Hook to check passwords in CreateRole() and AlterRole() */
 typedef void (*check_password_hook_type) (const char *username, const char *password, int password_type, Datum validuntil_time, bool validuntil_null);
 
 extern PGDLLIMPORT check_password_hook_type check_password_hook;