Bug#11765108 (Bug#58036) client utf32, utf16, ucs2 should be disallowed, they crash server

Problem: ucs2 was correctly disallowed in "SET NAMES" only,
while mysql_real_connect() and mysql_change_user() still allowed
to use ucs2, which made server crash.

Fix: disallow ucs2 in mysql_real_connect() and mysql_change_user().

  @ sql/set_var.cc
    Using new function.

  @ sql/sql_acl.cc
    - Return error if character set initialization failed
    - Getting rid of pointer aliasing:
      Initialize user_name to NULL, to avoid double free().

  @ sql/sql_connect.cc
    - in case of unsupported client character set send error and return true
    - in case of success return false

  @ sql/sql_connect.h
    - changing return type for thd_init_client_charset() to bool,
      to return errors to the caller

  @ sql/sql_parse.h
    - introducing a new function, to reuse in all places where we need
    to check client character set.

  @ tests/mysql_client_test.c
    Adding test

1 files changed, 4 insertions, 4 deletions

diff --git a/sql/sql_acl.cc b/sql/sql_acl.cc
index 427e2eb7346..9c57b3c102d 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -7799,7 +7799,8 @@ public:
   Thd_charset_adapter(THD *thd_arg) : thd (thd_arg) {} 
   bool init_client_charset(uint cs_number)
   {
-    thd_init_client_charset(thd, cs_number);
+    if (thd_init_client_charset(thd, cs_number))
+      return true;
     thd->update_charset();
     return thd->is_error();
   }
@@ -8929,9 +8930,8 @@ server_mpvio_initialize(THD *thd, MPVIO_EXT *mpvio, uint connect_errors,
   mpvio->auth_info.host_or_ip= thd->security_ctx->host_or_ip;
   mpvio->auth_info.host_or_ip_length= 
     (unsigned int) strlen(thd->security_ctx->host_or_ip);
-  mpvio->auth_info.user_name= thd->security_ctx->user;
-  mpvio->auth_info.user_name_length= thd->security_ctx->user ? 
-    (unsigned int) strlen(thd->security_ctx->user) : 0;
+  mpvio->auth_info.user_name= NULL;
+  mpvio->auth_info.user_name_length= 0;
   mpvio->connect_errors= connect_errors;
   mpvio->status= MPVIO_EXT::FAILURE;