MDEV-6572 "USE dbname" with a bad sequence erroneously connects to a wrong database

include/m_ctype.h

@@ -889,6 +889,10 @@ uint32 my_convert(char *to, uint32 to_length, CHARSET_INFO *to_cs,
     cannot be represented in the destination character set was found,
     or to NULL if all characters in the given range were successfully
     converted.
+
+  "src" is allowed to be a NULL pointer. In this case "src_length" must
+  be equal to 0. All "status" members are initialized to NULL, and 0 is
+  returned.
 */
 size_t my_convert_fix(CHARSET_INFO *dstcs, char *dst, size_t dst_length,
                       CHARSET_INFO *srccs, const char *src, size_t src_length,

mysql-test/r/ctype_utf8.result

@@ -9332,3 +9332,15 @@ DROP TABLE allbytes;
 #
 # End of 10.0 tests
 #
+#
+# Start of 10.1 tests
+#
+#
+# MDEV-6572 "USE dbname" with a bad sequence erroneously connects to a wrong database
+#
+SET NAMES utf8;
+SELECT * FROM `test😁😁test`;
+ERROR HY000: Invalid utf8 character string: 'test\xF0\x9F\x98\x81\xF0\x9F\x98\x81test'
+#
+# End of 10.1 tests
+#

mysql-test/r/ctype_utf8mb4.result

@@ -3356,3 +3356,15 @@ DROP TABLE t1;
 #
 # End of tests
 #
+#
+# Start of 10.1 tests
+#
+#
+# MDEV-6572 "USE dbname" with a bad sequence erroneously connects to a wrong database
+#
+SET NAMES utf8mb4;
+SELECT * FROM `test😁😁test`;
+ERROR HY000: Invalid utf8mb4 character string: 'test\xF0\x9F\x98\x81\xF0\x9F\x98\x81test'
+#
+# End of 10.1 tests
+#

mysql-test/r/mysql.result

@@ -519,5 +519,17 @@ a
 | a                 |
 | aaaaaaaaaaaaaaaaa |
 +-------------------+
+#
+# Start of 10.1 tests
+#
+#
+# MDEV-6572 "USE dbname" with a bad sequence erroneously connects to a wrong database
+#
+#
+# End of 10.1 tests
+#
+ERROR 1300 (HY000): Invalid utf8 character string: 'test\xF0\x9F\x98\x81 '
+ERROR 1300 (HY000): Invalid binary character string: 'test\xF0\x9F\x98\x81 '
+ERROR 1300 (HY000) at line 2: Invalid utf8 character string: 'test\xF0\x9F\x98\x81'
 
 End of tests

mysql-test/t/ctype_utf8.test

@@ -1756,3 +1756,19 @@ let $ctype_unescape_combinations=selected;
 --echo #
 --echo # End of 10.0 tests
 --echo #
+
+
+--echo #
+--echo # Start of 10.1 tests
+--echo #
+
+--echo #
+--echo # MDEV-6572 "USE dbname" with a bad sequence erroneously connects to a wrong database
+--echo #
+SET NAMES utf8;
+--error ER_INVALID_CHARACTER_STRING
+SELECT * FROM `test😁😁test`;
+
+--echo #
+--echo # End of 10.1 tests
+--echo #

mysql-test/t/ctype_utf8mb4.test

@@ -1880,3 +1880,18 @@ DROP TABLE t1;
 --echo #
 --echo # End of tests
 --echo #
+
+--echo #
+--echo # Start of 10.1 tests
+--echo #
+
+--echo #
+--echo # MDEV-6572 "USE dbname" with a bad sequence erroneously connects to a wrong database
+--echo #
+SET NAMES utf8mb4;
+--error ER_INVALID_CHARACTER_STRING
+SELECT * FROM `test😁😁test`;
+
+--echo #
+--echo # End of 10.1 tests
+--echo #

mysql-test/t/mysql.test

@@ -608,5 +608,29 @@ EOF
 #
 --exec $MYSQL -t -N -e "SELECT 'a' union select 'aaaaaaaaaaaaaaaaa'"
 
+--echo #
+--echo # Start of 10.1 tests
+--echo #
+
+--echo #
+--echo # MDEV-6572 "USE dbname" with a bad sequence erroneously connects to a wrong database
+--echo #
+
+--echo #
+--echo # End of 10.1 tests
+--echo #
+
+--error 1
+--exec $MYSQL --default-character-set=utf8 -e "select 1" "test😁 " 2>&1
+--error 1
+--exec $MYSQL --default-character-set=binary -e "select 1" "test😁 " 2>&1
+--write_file $MYSQLTEST_VARDIR/tmp/mdev-6572.sql
+SET NAMES utf8;
+USE test😁 ;
+EOF
+--error 1
+--exec $MYSQL --default-character-set=utf8 < $MYSQLTEST_VARDIR/tmp/mdev-6572.sql 2>&1
+--remove_file $MYSQLTEST_VARDIR/tmp/mdev-6572.sql
+
 --echo
 --echo End of tests

sql/sql_acl.cc

@@ -11701,7 +11701,6 @@ static ulong parse_client_handshake_packet(MPVIO_EXT *mpvio,
   char *passwd= strend(user)+1;
   uint user_len= passwd - user - 1, db_len;
   char *db= passwd;
-  char db_buff[SAFE_NAME_LEN + 1];      // buffer to store db in utf8
   char user_buff[USERNAME_LENGTH + 1];	// buffer to store user in utf8
   uint dummy_errors;
 
@@ -11738,12 +11737,9 @@ static ulong parse_client_handshake_packet(MPVIO_EXT *mpvio,
   char *client_plugin= next_field= passwd + passwd_len + (db ? db_len + 1 : 0);
 
   /* Since 4.1 all database names are stored in utf8 */
-  if (db)
-  {
-    db_len= copy_and_convert(db_buff, sizeof(db_buff) - 1, system_charset_info,
-                             db, db_len, thd->charset(), &dummy_errors);
-    db= db_buff;
-  }
+  if (thd->copy_with_error(system_charset_info, &mpvio->db,
+                           thd->charset(), db, db_len))
+    return packet_error;
 
   user_len= copy_and_convert(user_buff, sizeof(user_buff) - 1,
                              system_charset_info, user, user_len,
@@ -11773,8 +11769,6 @@ static ulong parse_client_handshake_packet(MPVIO_EXT *mpvio,
 
   Security_context *sctx= thd->security_ctx;
 
-  if (thd->make_lex_string(&mpvio->db, db, db_len) == 0)
-    return packet_error; /* The error is set by make_lex_string(). */
   my_free(sctx->user);
   if (!(sctx->user= my_strndup(user, user_len, MYF(MY_WME))))
     return packet_error; /* The error is set by my_strdup(). */

sql/sql_class.cc

@@ -2231,18 +2231,88 @@ bool THD::convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 			 const char *from, uint from_length,
 			 CHARSET_INFO *from_cs)
 {
-  DBUG_ENTER("convert_string");
+  DBUG_ENTER("THD::convert_string");
   size_t new_length= to_cs->mbmaxlen * from_length;
   uint dummy_errors;
-  if (!(to->str= (char*) alloc(new_length+1)))
-  {
-    to->length= 0;				// Safety fix
-    DBUG_RETURN(1);				// EOM
-  }
+  if (alloc_lex_string(to, new_length + 1))
+    DBUG_RETURN(true);                          // EOM
   to->length= copy_and_convert((char*) to->str, new_length, to_cs,
 			       from, from_length, from_cs, &dummy_errors);
   to->str[to->length]= 0;                       // Safety
-  DBUG_RETURN(0);
+  DBUG_RETURN(false);
+}
+
+
+/*
+  Convert a string between two character sets.
+  dstcs and srccs cannot be &my_charset_bin.
+*/
+bool THD::convert_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                      CHARSET_INFO *srccs, const char *src, uint src_length,
+                      String_copier *status)
+{
+  DBUG_ENTER("THD::convert_fix");
+  size_t dst_length= dstcs->mbmaxlen * src_length;
+  if (alloc_lex_string(dst, dst_length + 1))
+    DBUG_RETURN(true);                           // EOM
+  dst->length= status->convert_fix(dstcs, (char*) dst->str, dst_length,
+                                   srccs, src, src_length, src_length);
+  dst->str[dst->length]= 0;                      // Safety
+  DBUG_RETURN(false);
+}
+
+
+/*
+  Copy or convert a string.
+*/
+bool THD::copy_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                   CHARSET_INFO *srccs, const char *src, uint src_length,
+                   String_copier *status)
+{
+  DBUG_ENTER("THD::copy_fix");
+  size_t dst_length= dstcs->mbmaxlen * src_length;
+  if (alloc_lex_string(dst, dst_length + 1))
+    DBUG_RETURN(true);                          // EOM
+  dst->length= status->well_formed_copy(dstcs, dst->str, dst_length,
+                                        srccs, src, src_length, src_length);
+  dst->str[dst->length]= '\0';
+  DBUG_RETURN(false);
+}
+
+
+class String_copier_with_error: public String_copier
+{
+public:
+  bool check_errors(CHARSET_INFO *srccs, const char *src, uint src_length)
+  {
+    if (most_important_error_pos())
+    {
+      ErrConvString err(src, src_length, &my_charset_bin);
+      my_error(ER_INVALID_CHARACTER_STRING, MYF(0), srccs->csname, err.ptr());
+      return true;
+    }
+    return false;
+  }
+};
+
+
+bool THD::convert_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                             CHARSET_INFO *srccs,
+                             const char *src, uint src_length)
+{
+  String_copier_with_error status;
+  return convert_fix(dstcs, dst, srccs, src, src_length, &status) ||
+         status.check_errors(srccs, src, src_length);
+}
+
+
+bool THD::copy_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                          CHARSET_INFO *srccs,
+                          const char *src, uint src_length)
+{
+  String_copier_with_error status;
+  return copy_fix(dstcs, dst, srccs, src, src_length, &status) ||
+         status.check_errors(srccs, src, src_length);
 }
 
 

sql/sql_class.h

@@ -3106,9 +3106,49 @@ public:
     return make_lex_string(lex_str, str, length);
   }
 
+  // Allocate LEX_STRING for character set conversion
+  bool alloc_lex_string(LEX_STRING *dst, uint length)
+  {
+    if ((dst->str= (char*) alloc(length)))
+      return false;
+    dst->length= 0;  // Safety
+    return true;     // EOM
+  }
   bool convert_string(LEX_STRING *to, CHARSET_INFO *to_cs,
 		      const char *from, uint from_length,
 		      CHARSET_INFO *from_cs);
+  /*
+    Convert a strings between character sets.
+    Uses my_convert_fix(), which uses an mb_wc .. mc_mb loop internally.
+    dstcs and srccs cannot be &my_charset_bin.
+  */
+  bool convert_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                   CHARSET_INFO *srccs, const char *src, uint src_length,
+                   String_copier *status);
+
+  /*
+    Same as above, but additionally sends ER_INVALID_CHARACTER_STRING
+    in case of bad byte sequences or Unicode conversion problems.
+  */
+  bool convert_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                          CHARSET_INFO *srccs,
+                          const char *src, uint src_length);
+
+  /*
+    If either "dstcs" or "srccs" is &my_charset_bin,
+    then performs native copying using cs->cset->copy_fix().
+    Otherwise, performs Unicode conversion using convert_fix().
+  */
+  bool copy_fix(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                CHARSET_INFO *srccs, const char *src, uint src_length,
+                String_copier *status);
+
+  /*
+    Same as above, but additionally sends ER_INVALID_CHARACTER_STRING
+    in case of bad byte sequences or Unicode conversion problems.
+  */
+  bool copy_with_error(CHARSET_INFO *dstcs, LEX_STRING *dst,
+                       CHARSET_INFO *srccs, const char *src, uint src_length);
 
   bool convert_string(String *s, CHARSET_INFO *from_cs, CHARSET_INFO *to_cs);
 

sql/sql_parse.cc

@@ -1320,8 +1320,9 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
   {
     LEX_STRING tmp;
     status_var_increment(thd->status_var.com_stat[SQLCOM_CHANGE_DB]);
-    thd->convert_string(&tmp, system_charset_info,
-			packet, packet_length, thd->charset());
+    if (thd->copy_with_error(system_charset_info, &tmp,
+                             thd->charset(), packet, packet_length))
+      break;
     if (!mysql_change_db(thd, &tmp, FALSE))
     {
       general_log_write(thd, command, thd->db, thd->db_length);

sql/sql_string.h

@@ -57,6 +57,17 @@ public:
     return well_formed_error_pos() ? well_formed_error_pos() :
                                      cannot_convert_error_pos();
   }
+  /*
+    Convert a string between character sets.
+    "dstcs" and "srccs" cannot be &my_charset_bin.
+  */
+  uint convert_fix(CHARSET_INFO *dstcs, char *dst, uint dst_length,
+                   CHARSET_INFO *srccs, const char *src, uint src_length,
+                   uint nchars)
+  {
+    return my_convert_fix(dstcs, dst, dst_length,
+                          srccs, src, src_length, nchars, this);
+  }
   /*
      Copy a string. Fix bad bytes/characters one Unicode conversion,
      break on bad bytes in case of non-Unicode copying.

sql/sql_yacc.yy

@@ -13966,8 +13966,8 @@ IDENT_sys:
             }
             else
             {
-              if (thd->convert_string(&$$, system_charset_info,
-                                  $1.str, $1.length, thd->charset()))
+              if (thd->convert_with_error(system_charset_info, &$$,
+                                          thd->charset(), $1.str, $1.length))
                 MYSQL_YYABORT;
             }
           }