Bug#20570: CURRENT_USER() in a VIEW with SQL SECURITY DEFINER returns

           invoker name

The bug was fixed similar to how context switch is handled in
Item_func_sp::execute_impl(): we store pointer to current
Name_resolution_context in Item_func_current_user class, and use
its Security_context in Item_func_current_user::fix_fields().

mysql-test/r/view_grant.result

@@ -618,3 +618,56 @@ ERROR HY000: There is no 'no-such-user'@'localhost' registered
 DROP VIEW v;
 DROP TABLE t1;
 USE test;
+DROP VIEW IF EXISTS v1;
+DROP VIEW IF EXISTS v2;
+DROP VIEW IF EXISTS v3;
+DROP FUNCTION IF EXISTS f1;
+DROP FUNCTION IF EXISTS f2;
+DROP PROCEDURE IF EXISTS p1;
+CREATE SQL SECURITY DEFINER VIEW v1 AS SELECT CURRENT_USER() AS cu;
+CREATE FUNCTION f1() RETURNS VARCHAR(77) SQL SECURITY INVOKER
+RETURN CURRENT_USER();
+CREATE SQL SECURITY DEFINER VIEW v2 AS SELECT f1() AS cu;
+CREATE PROCEDURE p1(OUT cu VARCHAR(77)) SQL SECURITY INVOKER
+SET cu= CURRENT_USER();
+CREATE FUNCTION f2() RETURNS VARCHAR(77) SQL SECURITY INVOKER
+BEGIN
+DECLARE cu VARCHAR(77);
+CALL p1(cu);
+RETURN cu;
+END|
+CREATE SQL SECURITY DEFINER VIEW v3 AS SELECT f2() AS cu;
+CREATE USER mysqltest_u1@localhost;
+GRANT ALL ON test.* TO mysqltest_u1@localhost;
+
+The following tests should all return 1.
+
+SELECT CURRENT_USER() = 'mysqltest_u1@localhost';
+CURRENT_USER() = 'mysqltest_u1@localhost'
+1
+SELECT f1() = 'mysqltest_u1@localhost';
+f1() = 'mysqltest_u1@localhost'
+1
+CALL p1(@cu);
+SELECT @cu = 'mysqltest_u1@localhost';
+@cu = 'mysqltest_u1@localhost'
+1
+SELECT f2() = 'mysqltest_u1@localhost';
+f2() = 'mysqltest_u1@localhost'
+1
+SELECT cu = 'root@localhost' FROM v1;
+cu = 'root@localhost'
+1
+SELECT cu = 'root@localhost' FROM v2;
+cu = 'root@localhost'
+1
+SELECT cu = 'root@localhost' FROM v3;
+cu = 'root@localhost'
+1
+DROP VIEW v3;
+DROP FUNCTION f2;
+DROP PROCEDURE p1;
+DROP FUNCTION f1;
+DROP VIEW v2;
+DROP VIEW v1;
+DROP USER mysqltest_u1@localhost;

mysql-test/t/view_grant.test

@@ -807,3 +807,65 @@ SELECT * FROM v;
 DROP VIEW v;
 DROP TABLE t1;
 USE test;
+
+
+#
+# BUG#20570: CURRENT_USER() in a VIEW with SQL SECURITY DEFINER
+# returns invoker name
+#
+--disable_warnings
+DROP VIEW IF EXISTS v1;
+DROP VIEW IF EXISTS v2;
+DROP VIEW IF EXISTS v3;
+DROP FUNCTION IF EXISTS f1;
+DROP FUNCTION IF EXISTS f2;
+DROP PROCEDURE IF EXISTS p1;
+--enable_warnings
+
+CREATE SQL SECURITY DEFINER VIEW v1 AS SELECT CURRENT_USER() AS cu;
+
+CREATE FUNCTION f1() RETURNS VARCHAR(77) SQL SECURITY INVOKER
+  RETURN CURRENT_USER();
+CREATE SQL SECURITY DEFINER VIEW v2 AS SELECT f1() AS cu;
+
+CREATE PROCEDURE p1(OUT cu VARCHAR(77)) SQL SECURITY INVOKER
+  SET cu= CURRENT_USER();
+delimiter |;
+CREATE FUNCTION f2() RETURNS VARCHAR(77) SQL SECURITY INVOKER
+BEGIN
+  DECLARE cu VARCHAR(77);
+  CALL p1(cu);
+  RETURN cu;
+END|
+delimiter ;|
+CREATE SQL SECURITY DEFINER VIEW v3 AS SELECT f2() AS cu;
+
+CREATE USER mysqltest_u1@localhost;
+GRANT ALL ON test.* TO mysqltest_u1@localhost;
+
+connect (conn1, localhost, mysqltest_u1,,);
+
+--echo
+--echo The following tests should all return 1.
+--echo
+SELECT CURRENT_USER() = 'mysqltest_u1@localhost';
+SELECT f1() = 'mysqltest_u1@localhost';
+CALL p1(@cu);
+SELECT @cu = 'mysqltest_u1@localhost';
+SELECT f2() = 'mysqltest_u1@localhost';
+SELECT cu = 'root@localhost' FROM v1;
+SELECT cu = 'root@localhost' FROM v2;
+SELECT cu = 'root@localhost' FROM v3;
+
+disconnect conn1;
+connection default;
+
+DROP VIEW v3;
+DROP FUNCTION f2;
+DROP PROCEDURE p1;
+DROP FUNCTION f1;
+DROP VIEW v2;
+DROP VIEW v1;
+DROP USER mysqltest_u1@localhost;
+
+# End of 5.0 tests.

sql/item_create.cc

@@ -296,12 +296,6 @@ Item *create_func_pow(Item* a, Item *b)
   return new Item_func_pow(a,b);
 }
 
-Item *create_func_current_user()
-{
-  current_thd->lex->safe_to_cache_query= 0;
-  return new Item_func_user(TRUE);
-}
-
 Item *create_func_radians(Item *a)
 {
   return new Item_func_units((char*) "radians",a,M_PI/180,0.0);

sql/item_create.h

@@ -73,7 +73,6 @@ Item *create_func_period_add(Item* a, Item *b);
 Item *create_func_period_diff(Item* a, Item *b);
 Item *create_func_pi(void);
 Item *create_func_pow(Item* a, Item *b);
-Item *create_func_current_user(void);
 Item *create_func_radians(Item *a);
 Item *create_func_release_lock(Item* a);
 Item *create_func_repeat(Item* a, Item *b);

sql/item_strfunc.cc

@@ -1650,42 +1650,51 @@ String *Item_func_database::val_str(String *str)
   return str;
 }
 
-// TODO: make USER() replicate properly (currently it is replicated to "")
 
-String *Item_func_user::val_str(String *str)
+/*
+  TODO: make USER() replicate properly (currently it is replicated to "")
+*/
+bool Item_func_user::init(const char *user, const char *host)
 {
   DBUG_ASSERT(fixed == 1);
-  THD          *thd=current_thd;
-  CHARSET_INFO *cs= system_charset_info;
-  const char   *host, *user;
-  uint		res_length;
-
-  if (is_current)
-  {
-    user= thd->security_ctx->priv_user;
-    host= thd->security_ctx->priv_host;
-  }
-  else
-  {
-    user= thd->main_security_ctx.user;
-    host= thd->main_security_ctx.host_or_ip;
-  }
 
   // For system threads (e.g. replication SQL thread) user may be empty
-  if (!user)
-    return &my_empty_string;
-  res_length= (strlen(user)+strlen(host)+2) * cs->mbmaxlen;
+  if (user)
+  {
+    CHARSET_INFO *cs= str_value.charset();
+    uint res_length= (strlen(user)+strlen(host)+2) * cs->mbmaxlen;
 
-  if (str->alloc(res_length))
+    if (str_value.alloc(res_length))
     {
       null_value=1;
-    return 0;
+      return TRUE;
     }
-  res_length=cs->cset->snprintf(cs, (char*)str->ptr(), res_length, "%s@%s",
-			        user, host);
-  str->length(res_length);
-  str->set_charset(cs);
-  return str;
+
+    res_length=cs->cset->snprintf(cs, (char*)str_value.ptr(), res_length,
+                                  "%s@%s", user, host);
+    str_value.length(res_length);
+    str_value.mark_as_const();
+  }
+  return FALSE;
+}
+
+
+bool Item_func_user::fix_fields(THD *thd, Item **ref)
+{
+  return (Item_func_sysconst::fix_fields(thd, ref) ||
+          init(thd->main_security_ctx.user,
+               thd->main_security_ctx.host_or_ip));
+}
+
+
+bool Item_func_current_user::fix_fields(THD *thd, Item **ref)
+{
+  if (Item_func_sysconst::fix_fields(thd, ref))
+    return TRUE;
+
+  Security_context *ctx= (context->security_ctx
+                          ? context->security_ctx : thd->security_ctx);
+  return init(ctx->priv_user, ctx->priv_host);
 }
 
 

sql/item_strfunc.h

@@ -385,21 +385,40 @@ public:
 
 class Item_func_user :public Item_func_sysconst
 {
-  bool is_current;
+protected:
+  bool init (const char *user, const char *host);
 
 public:
-  Item_func_user(bool is_current_arg)
-    :Item_func_sysconst(), is_current(is_current_arg) {}
-  String *val_str(String *);
+  Item_func_user()
+  {
+    str_value.set("", 0, system_charset_info);
+  }
+  String *val_str(String *)
+  {
+    DBUG_ASSERT(fixed == 1);
+    return (null_value ? 0 : &str_value);
+  }
+  bool fix_fields(THD *thd, Item **ref);
   void fix_length_and_dec()
   {
     max_length= ((USERNAME_LENGTH + HOSTNAME_LENGTH + 1) *
                  system_charset_info->mbmaxlen);
   }
-  const char *func_name() const
-    { return is_current ? "current_user" : "user"; }
-  const char *fully_qualified_func_name() const
-    { return is_current ? "current_user()" : "user()"; }
+  const char *func_name() const { return "user"; }
+  const char *fully_qualified_func_name() const { return "user()"; }
+};
+
+
+class Item_func_current_user :public Item_func_user
+{
+  Name_resolution_context *context;
+
+public:
+  Item_func_current_user(Name_resolution_context *context_arg)
+    : context(context_arg) {}
+  bool fix_fields(THD *thd, Item **ref);
+  const char *func_name() const { return "current_user"; }
+  const char *fully_qualified_func_name() const { return "current_user()"; }
 };
 
 

sql/sql_yacc.yy

@@ -4413,7 +4413,10 @@ simple_expr:
 	    Lex->safe_to_cache_query=0;
 	  }
 	| CURRENT_USER optional_braces
-          { $$= create_func_current_user(); }
+          {
+            $$= new Item_func_current_user(Lex->current_context());
+            Lex->safe_to_cache_query= 0;
+          }
 	| DATE_ADD_INTERVAL '(' expr ',' interval_expr interval ')'
 	  { $$= new Item_date_add_interval($3,$5,$6,0); }
 	| DATE_SUB_INTERVAL '(' expr ',' interval_expr interval ')'
@@ -4764,7 +4767,7 @@ simple_expr:
 	| UNIX_TIMESTAMP '(' expr ')'
 	  { $$= new Item_func_unix_timestamp($3); }
 	| USER '(' ')'
-	  { $$= new Item_func_user(FALSE); Lex->safe_to_cache_query=0; }
+	  { $$= new Item_func_user(); Lex->safe_to_cache_query=0; }
 	| UTC_DATE_SYM optional_braces
 	  { $$= new Item_func_curdate_utc(); Lex->safe_to_cache_query=0;}
 	| UTC_TIME_SYM optional_braces