SCRUM: Secure auth

Implement mysql_change_user
Get rid of double user search at authentication
Some cleanups


client/mysqladmin.c:
  Fix long line
include/mysql_com.h:
  Fix long lines
libmysql/libmysql.c:
  mysql_change_user() for new auth + some fixes
sql/password.c:
  Add author info so who is guilty in errors would be known :)
sql/sql_acl.cc:
  Move class definitions to .h
sql/sql_acl.h:
  Add class definitions
sql/sql_parse.cc:
  Get rid of double user search. Implement mysql_change_user

client/mysqladmin.c

@@ -768,8 +768,9 @@ static int execute_commands(MYSQL *mysql,int argc, char **argv)
 	return 1;
       }
       if (argv[1][0])
-	make_scrambled_password(crypted_pw,argv[1],(find_type(argv[0],&command_typelib,2)
-                                ==ADMIN_OLD_PASSWORD),&rand_st);
+	make_scrambled_password(crypted_pw,argv[1],(find_type(argv[0],
+                                &command_typelib,2)==ADMIN_OLD_PASSWORD),
+                                &rand_st);
       else
 	crypted_pw[0]=0;			/* No password */
       sprintf(buff,"set password='%s',sql_log_off=0",crypted_pw);

include/mysql_com.h

@@ -280,18 +280,22 @@ extern unsigned long net_buffer_length;
 void randominit(struct rand_struct *,unsigned long seed1,
 		unsigned long seed2);
 double rnd(struct rand_struct *);
-void make_scrambled_password(char *to,const char *password,my_bool force_old_scramble,struct rand_struct *rand_st);
+void make_scrambled_password(char *to,const char *password,
+     my_bool force_old_scramble,struct rand_struct *rand_st);
 int get_password_length(my_bool force_old_scramble);
 char get_password_version(const char* password);
 void create_random_string(int length,struct rand_struct *rand_st,char* target);
-my_bool validate_password(const char* password, const char* message, ulong* salt);
+my_bool validate_password(const char* password, const char* message,
+        ulong* salt);
 void password_hash_stage1(char *to, const char *password);
 void password_hash_stage2(char *to,const char *salt);
 void password_crypt(const char* from,char* to, const char* password,int length);
-void get_hash_and_password(ulong* salt, uint8 pversion,char* hash, unsigned char* bin_password);
+void get_hash_and_password(ulong* salt, unsigned char  pversion,char* hash, 
+     unsigned char* bin_password);
 void get_salt_from_password(unsigned long *res,const char *password);
 void create_key_from_old_password(const char* password,char* key);
-void make_password_from_salt(char *to, unsigned long *hash_res, uint8 password_version);
+void make_password_from_salt(char *to, unsigned long *hash_res, 
+     unsigned char  password_version);
 char *scramble(char *to,const char *message,const char *password,
 	       my_bool old_ver);
 my_bool check_scramble(const char *, const char *message,

libmysql/libmysql.c

@@ -2228,8 +2228,8 @@ Try also with PIPE or TCP/IP
   {
     if (passwd[0])
     {
-      /* Use something for not empty password not to match it against empty one */
-      end=scramble(strend(buff+5)+1, mysql->scramble_buff,"~MySQL#!",
+      /* Use something for not empty password not to match against empty one */
+      end=scramble(strend(buff+5)+1, mysql->scramble_buff,"\1~MySQL#!\2",
                  (my_bool) (mysql->protocol_version == 9));
     }
     else  /* For empty password*/ 
@@ -2409,7 +2409,11 @@ static my_bool mysql_reconnect(MYSQL *mysql)
 my_bool	STDCALL mysql_change_user(MYSQL *mysql, const char *user, 
 				  const char *passwd, const char *db)
 {
-  char buff[512],*pos=buff;
+  char buff[512],*end=buff;
+  ulong		pkt_length;
+  char          password_hash[20]; /* Used for tmp storage of stage1 hash */
+  NET		*net= &mysql->net;
+  
   DBUG_ENTER("mysql_change_user");
 
   if (!user)
@@ -2417,12 +2421,83 @@ my_bool	STDCALL mysql_change_user(MYSQL *mysql, const char *user,
   if (!passwd)
     passwd="";
     
-  pos=strmov(pos,user)+1;
-  pos=scramble(pos, mysql->scramble_buff, passwd,
+   /* Store user into the buffer */
+  end=strmov(end,user)+1;
+   
+  /* 
+    We always start with old type handshake the only difference is message sent
+    If server handles secure connection type we'll not send the real scramble
+  */
+  if (mysql->server_capabilities & CLIENT_SECURE_CONNECTION)
+  {
+    if (passwd[0])
+    {
+      /* Use something for not empty password not to match it against empty one */
+      end=scramble(end, mysql->scramble_buff,"\1~MySQL#!\2",
                  (my_bool) (mysql->protocol_version == 9));                 
-  pos=strmov(pos+1,db ? db : "");
-  if (simple_command(mysql,COM_CHANGE_USER, buff,(ulong) (pos-buff),0))
-    DBUG_RETURN(1);
+    }             
+    else  /* For empty password*/ 
+      *end=0; /* Store zero length scramble */
+  }
+  /* Real scramble is sent only for servers. This is to be blocked by option */
+  else
+    end=scramble(end, mysql->scramble_buff, passwd,
+                 (my_bool) (mysql->protocol_version == 9));
+                                              
+  /* Add database if needed */	       
+  end=strmov(end+1,db ? db : "");
+  
+  /* Write authentication package */ 
+  
+  simple_command(mysql,COM_CHANGE_USER, buff,(ulong) (end-buff),1);
+  
+  /* We shall only query sever if it expect us to do so */     
+  if ( (pkt_length=net_safe_read(mysql)) == packet_error)
+    goto error;
+
+  if  (mysql->server_capabilities & CLIENT_SECURE_CONNECTION)
+  {
+    /* This should basically always happen with new server unless empty password */
+    if (pkt_length==24) /* We have new hash back */
+    {
+      /* Old passwords will have zero at the first byte of hash */
+      if (net->read_pos[0]) 
+      {
+        /* Build full password hash as it is required to decode scramble */        
+        password_hash_stage1(buff, passwd);        
+        /* Store copy as we'll need it later */
+        memcpy(password_hash,buff,20);
+        /* Finally hash complete password using hash we got from server */
+        password_hash_stage2(password_hash,net->read_pos);
+        /* Decypt and store scramble 4 = hash for stage2 */
+        password_crypt(net->read_pos+4,mysql->scramble_buff,password_hash,20);
+        mysql->scramble_buff[20]=0;    
+        /* Encode scramble with password. Recycle buffer */
+        password_crypt(mysql->scramble_buff,buff,buff,20);
+      }
+      else
+      {
+        /* Create password to decode scramble */
+        create_key_from_old_password(passwd,password_hash);
+        /* Decypt and store scramble 4 = hash for stage2 */
+        password_crypt(net->read_pos+4,mysql->scramble_buff,password_hash,20);
+        mysql->scramble_buff[20]=0;    
+        /* Finally scramble decoded scramble with password */    
+        scramble(buff, mysql->scramble_buff, passwd,
+                  (my_bool) (mysql->protocol_version == 9));    
+      }    
+      /* Write second package of authentication */
+      if (my_net_write(net,buff,20) || net_flush(net))
+      {
+        net->last_errno= CR_SERVER_LOST; 
+        strmov(net->last_error,ER(net->last_errno));    
+        goto error;
+      }
+      /* Read What server thinks about out new auth message report */ 
+      if (net_safe_read(mysql) == packet_error)
+          goto error;
+    }
+  }
       
   my_free(mysql->user,MYF(MY_ALLOW_ZERO_PTR));
   my_free(mysql->passwd,MYF(MY_ALLOW_ZERO_PTR));
@@ -2432,6 +2507,10 @@ my_bool	STDCALL mysql_change_user(MYSQL *mysql, const char *user,
   mysql->passwd=my_strdup(passwd,MYF(MY_WME));
   mysql->db=    db ? my_strdup(db,MYF(MY_WME)) : 0;
   DBUG_RETURN(0);
+  
+  error:
+  DBUG_RETURN(1);
+   
 }
 
 

sql/password.c

@@ -49,6 +49,8 @@
   stronger. Now if one will steal mysql database content he will not be able 
   to break into MySQL.
 
+  New Password handling functions by Peter Zaitsev
+  
   
 *****************************************************************************/
 

sql/sql_acl.cc

@@ -33,52 +33,6 @@
 #include <stdarg.h>
 
 
-struct acl_host_and_ip
-{
-  char *hostname;
-  long ip,ip_mask;			// Used with masked ip:s
-};
-
-
-class ACL_ACCESS {
-public:
-  ulong sort;
-  ulong access;
-};
-
-
-/* ACL_HOST is used if no host is specified */
-
-class ACL_HOST :public ACL_ACCESS
-{
-public:
-  acl_host_and_ip host;
-  char *db;
-};
-
-
-class ACL_USER :public ACL_ACCESS
-{
-public:
-  acl_host_and_ip host;
-  uint hostname_length;
-  USER_RESOURCES user_resource;
-  char *user,*password;
-  ulong salt[6]; // New password has longer length
-  uint8 pversion; // password version 
-  enum SSL_type ssl_type;
-  const char *ssl_cipher, *x509_issuer, *x509_subject;
-};
-
-
-class ACL_DB :public ACL_ACCESS
-{
-public:
-  acl_host_and_ip host;
-  char *user,*db;
-};
-
-
 class acl_entry :public hash_filo_element
 {
 public:
@@ -105,6 +59,7 @@ static HASH acl_check_hosts, hash_tables;
 static DYNAMIC_ARRAY acl_wild_hosts;
 static hash_filo *acl_cache;
 static uint grant_version=0;
+static uint priv_version=0; /* Version of priv tables. incremented by acl_init */
 static ulong get_access(TABLE *form,uint fieldnr);
 static int acl_compare(ACL_ACCESS *a,ACL_ACCESS *b);
 static ulong get_sort(uint count,...);
@@ -149,6 +104,8 @@ my_bool acl_init(THD *org_thd, bool dont_read_acl_tables)
     DBUG_RETURN(0); /* purecov: tested */
   }    
   
+  priv_version++; /* Priveleges updated */
+  
   /*
     To be able to run this from boot, we allocate a temporary THD
   */
@@ -515,15 +472,23 @@ void prepare_scramble(THD* thd, ACL_USER *acl_user,char* prepared_scramble)
 /*
   Get master privilges for user (priviliges for all tables).
   Required before connecting to MySQL
+  
+  as we have 2 stage handshake now we cache user not to lookup
+  it second time. At the second stage we do not lookup user in case 
+  we already know it;
+  
 */
 
 ulong acl_getroot(THD *thd, const char *host, const char *ip, const char *user,
 		  const char *password,const char *message,char **priv_user,
-		  bool old_ver, USER_RESOURCES  *mqh,char* prepared_scramble,int stage)
+		  bool old_ver, USER_RESOURCES  *mqh,char* prepared_scramble,
+                  int stage,uint *cur_priv_version,ACL_USER** hint_user)
 {
   ulong user_access=NO_ACCESS;
   *priv_user=(char*) user;
   bool password_correct=0;
+  ACL_USER *acl_user=NULL;
+  
   DBUG_ENTER("acl_getroot");
 
   bzero(mqh,sizeof(USER_RESOURCES));
@@ -534,24 +499,47 @@ ulong acl_getroot(THD *thd, const char *host, const char *ip, const char *user,
   }
   VOID(pthread_mutex_lock(&acl_cache->lock));
   
+  
   /*
     Get possible access from user_list. This is or'ed to others not
     fully specified
+    
+    If we have cached user use it, in other case look it up.
   */
+  
+  if (stage && (*cur_priv_version==priv_version))
+    acl_user=*hint_user;
+  else  
     for (uint i=0 ; i < acl_users.elements ; i++)
     {
-    ACL_USER *acl_user=dynamic_element(&acl_users,i,ACL_USER*);
-    if (!acl_user->user || !strcmp(user,acl_user->user))
+      ACL_USER *acl_user_search=dynamic_element(&acl_users,i,ACL_USER*);
+      if (!acl_user_search->user || !strcmp(user,acl_user_search->user))
       {
-      if (compare_hostname(&acl_user->host,host,ip))
+        if (compare_hostname(&acl_user_search->host,host,ip))
         {
+          /* Found mathing user */ 
+          acl_user=acl_user_search;
+          /* Store it as a cache */
+          *hint_user=acl_user;
+          *cur_priv_version=priv_version;
+          break;
+        }  
+      }
+    } 
+    
+  
+  /* Now we have acl_user found and may start our checks */
+  
+  if (acl_user)      
+  { 
+    /* Password should present for both or absend for both */       
     if (!acl_user->password && !*password ||
        (acl_user->password && *password))
     {    
       /* Quick check and accept for empty passwords*/
       if (!acl_user->password && !*password)
         password_correct=1;
-          else
+      else /* Normal password presents */
       {    
         /* New version password is checked differently */
         if (acl_user->pversion)
@@ -577,9 +565,16 @@ ulong acl_getroot(THD *thd, const char *host, const char *ip, const char *user,
               prepare_scramble(thd,acl_user,prepared_scramble);                 
         }    
       }
-          /* If password correct continue with checking other limitations */          
-          if (password_correct)                     
-	  {
+    }
+  }
+  
+  /* If user not found password_correct will also be zero */
+  if (!password_correct)           
+   goto unlock_and_exit; 
+  
+  /* OK. User found and password checked continue validation */
+  
+            
 #ifdef HAVE_OPENSSL
   Vio *vio=thd->net.vio;
   /*
@@ -615,8 +610,7 @@ ulong acl_getroot(THD *thd, const char *host, const char *ip, const char *user,
     if (acl_user->ssl_cipher)
     {
       DBUG_PRINT("info",("comparing ciphers: '%s' and '%s'",
-	  			 acl_user->ssl_cipher,
-	  			 SSL_get_cipher(vio->ssl_)));
+        	 acl_user->ssl_cipher,SSL_get_cipher(vio->ssl_)));
       if (!strcmp(acl_user->ssl_cipher,SSL_get_cipher(vio->ssl_)))
         user_access=acl_user->access;
       else
@@ -666,26 +660,13 @@ ulong acl_getroot(THD *thd, const char *host, const char *ip, const char *user,
   *mqh=acl_user->user_resource;
   if (!acl_user->user)
     *priv_user=(char*) "";	// Change to anonymous user /* purecov: inspected */
-	    break;
-	  } // correct password
-        } // found matching user
     
-#ifndef ALLOW_DOWNGRADE_OF_USERS
-	break;				// Wrong password breaks loop /* purecov: inspected */
-#endif
-      }
-    }
-  }
+unlock_and_exit:
   VOID(pthread_mutex_unlock(&acl_cache->lock));
   DBUG_RETURN(user_access);
 }
 
 
-/*
-** Functions to add and change user and database privileges when one
-** changes things with GRANT
-*/
-
 static byte* check_get_key(ACL_USER *buff,uint *length,
 			   my_bool not_used __attribute__((unused)))
 {

sql/sql_acl.h

@@ -79,6 +79,55 @@
 #define fix_rights_for_column(A) (((A) & COL_ACLS) | ((A & ~COL_ACLS) << 7))
 #define get_rights_for_column(A) (((A) & COL_ACLS) | ((A & ~COL_ACLS) >> 7))
 
+/* Classes */
+
+struct acl_host_and_ip
+{
+  char *hostname;
+  long ip,ip_mask;                      // Used with masked ip:s
+};
+
+
+class ACL_ACCESS {
+public:
+  ulong sort;
+  ulong access;
+};
+
+
+/* ACL_HOST is used if no host is specified */
+
+class ACL_HOST :public ACL_ACCESS
+{
+public:
+  acl_host_and_ip host;
+  char *db;
+};
+
+
+class ACL_USER :public ACL_ACCESS
+{
+public:
+  acl_host_and_ip host;
+  uint hostname_length;
+  USER_RESOURCES user_resource;
+  char *user,*password;
+  ulong salt[6]; // New password has longer length
+  uint8 pversion; // password version
+  enum SSL_type ssl_type;
+  const char *ssl_cipher, *x509_issuer, *x509_subject;
+};
+
+
+class ACL_DB :public ACL_ACCESS
+{
+public:
+  acl_host_and_ip host;
+  char *user,*db;
+};
+
+
+
 /* prototypes */
 
 my_bool  acl_init(THD *thd, bool dont_read_acl_tables);
@@ -88,7 +137,8 @@ ulong acl_get(const char *host, const char *ip, const char *bin_ip,
 	      const char *user, const char *db);
 ulong acl_getroot(THD *thd, const char *host, const char *ip, const char *user,
 		  const char *password,const char *scramble,char **priv_user,
-		  bool old_ver, USER_RESOURCES *max,char* prepared_scramble, int stage);
+		  bool old_ver, USER_RESOURCES *max,char* prepared_scramble,
+                  int stage, uint *cur_priv_version, ACL_USER **cached_user);
 bool acl_check_host(const char *host, const char *ip);
 bool check_change_password(THD *thd, const char *host, const char *user);
 bool change_password(THD *thd, const char *host, const char *user,

sql/sql_parse.cc

@@ -188,14 +188,16 @@ static int get_or_create_user_conn(THD *thd, const char *user,
   thd->user, thd->master_access, thd->priv_user, thd->db, thd->db_access
 */
 
-static bool check_user(THD *thd,enum_server_command command, const char *user,
+static int check_user(THD *thd,enum_server_command command, const char *user,
 		       const char *passwd, const char *db, bool check_count, 
                        bool do_send_error, char* crypted_scramble,int stage,
-                       bool had_password)
+                       bool had_password,uint *cur_priv_version, 
+                       ACL_USER** hint_user)
 {
   thd->db=0;
   thd->db_length=0;
   USER_RESOURCES ur;
+  
   /* We shall avoid dupplicate user allocations here */ 
   if (!(thd->user))
     if (!(thd->user = my_strdup(user, MYF(0))))
@@ -207,7 +209,9 @@ static bool check_user(THD *thd,enum_server_command command, const char *user,
 				 passwd, thd->scramble, &thd->priv_user,
 				 protocol_version == 9 ||
 				 !(thd->client_capabilities &
-				   CLIENT_LONG_PASSWORD),&ur,crypted_scramble,stage);
+				   CLIENT_LONG_PASSWORD),&ur,crypted_scramble,
+                                   stage,cur_priv_version,hint_user);
+                                   
   DBUG_PRINT("info",
 	     ("Capabilities: %d  packet_length: %d  Host: '%s'  User: '%s'  Using password: %s  Access: %u  db: '%s'",
 	      thd->client_capabilities, thd->max_client_packet_length,
@@ -261,6 +265,7 @@ static bool check_user(THD *thd,enum_server_command command, const char *user,
   if (thd->user_connect && thd->user_connect->user_resources.connections && 
       check_for_max_user_connections(thd, thd->user_connect))
     return -1;
+ 
   if (db && db[0])
   {
     bool error=test(mysql_change_db(thd,db));
@@ -626,6 +631,9 @@ check_connections(THD *thd)
     
   char prepared_scramble[SCRAMBLE41_LENGTH+4]; /* Buffer for scramble and hash */
   
+  ACL_USER* cached_user;
+  uint cur_priv_version;
+   
   /* Simple connect only for old clients. New clients always use secure auth */
   bool simple_connect=(!(thd->client_capabilities & CLIENT_SECURE_CONNECTION));
   
@@ -634,7 +642,7 @@ check_connections(THD *thd)
   
   /* Check user permissions. If password failure we'll get scramble back */
   if (check_user(thd,COM_CONNECT, user, passwd, db, 1, simple_connect,
-      prepared_scramble,0,using_password))
+      prepared_scramble,0,using_password,&cur_priv_version,&cached_user)<0)
   { 
     /* If The client is old we just have to return error */
     if (simple_connect)
@@ -682,7 +690,8 @@ check_connections(THD *thd)
       }
     /* Final attempt to check the user based on reply */ 
     if (check_user(thd,COM_CONNECT, tmp_user, (char*)net->read_pos, 
-        tmp_db, 1, 1,prepared_scramble,1,using_password))
+        tmp_db, 1, 1,prepared_scramble,1,using_password,&cur_priv_version,
+        &cached_user))
       return -1;
   }
   thd->password=using_password;
@@ -1040,20 +1049,100 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
     uint save_db_access=    thd->db_access;
     uint save_db_length=    thd->db_length;
     char *save_user=	    thd->user;
+    thd->user=NULL; /* Needed for check_user to allocate new user */
     char *save_priv_user=   thd->priv_user;
     char *save_db=	    thd->db;
     USER_CONN *save_uc=     thd->user_connect;
+    bool simple_connect;
+    bool using_password;
+    
+    ulong pkt_len=0; /* Length of reply packet */
+    
+    /* Small check for incomming packet */
 
     if ((uint) ((uchar*) db - net->read_pos) > packet_length)
-    {						// Check if protocol is ok
-      send_error(thd, ER_UNKNOWN_COM_ERROR);
-      break;
+      goto restore_user_err;
+    
+    /* Now we shall basically perform authentication again */
+    
+     /* We can get only old hash at this point */
+    if (passwd[0] && strlen(passwd)!=SCRAMBLE_LENGTH) 
+      goto restore_user_err;
+      
+    char prepared_scramble[SCRAMBLE41_LENGTH+4];/* Buffer for scramble,hash */  
+    ACL_USER* cached_user;                      /* Cached user */
+    uint cur_priv_version;                      /* Cached grant version */
+   
+    /* Simple connect only for old clients. New clients always use sec. auth*/
+    simple_connect=(!(thd->client_capabilities & CLIENT_SECURE_CONNECTION));
+  
+    /* Store information if we used password. passwd will be dammaged */
+    using_password=test(passwd[0]);
+    
+    /* 
+     Check user permissions. If password failure we'll get scramble back 
+     Do not retry if we already have sent error (result>0) 
+    */ 
+    if (check_user(thd,COM_CHANGE_USER, user, passwd, db, 0, simple_connect,
+        prepared_scramble,0,using_password,&cur_priv_version,&cached_user)<0) 
+    {
+      /* If The client is old we just have to have auth failure */
+      if (simple_connect)
+        goto restore_user; /* Error is already reported */
+          
+      /* Store current used and database as they are erased with next packet */
+    
+      char tmp_user[USERNAME_LENGTH+1];
+      char tmp_db[NAME_LEN+1];
+
+      if (user)
+      {
+        strncpy(tmp_user,user,USERNAME_LENGTH+1);
+        /* Extra safety if we have too long data */
+        tmp_user[USERNAME_LENGTH]=0;   
       } 
-    /* WARNING THIS HAS TO BE REWRITTEN */
-    char tmp_buffer[64];
-    printf("Change user called: %s %s %s\n",user,passwd,db);
-    if (check_user(thd, COM_CHANGE_USER, user, passwd, db, 0,1,tmp_buffer,0,1))
-    {						// Restore old user
+      else
+        tmp_user[0]=0;  
+      if (db)
+      {
+        strncpy(tmp_db,db,NAME_LEN+1);
+        tmp_db[NAME_LEN]=0;
+      }  
+      else 
+        tmp_db[0]=0;
+        
+      /* Write hash and encrypted scramble to client */
+      if (my_net_write(net,prepared_scramble,SCRAMBLE41_LENGTH+4) 
+        || net_flush(net))                      
+        goto restore_user_err;    
+        
+      /* Reading packet back */  
+      if ((pkt_len=my_net_read(net)) == packet_error)     
+        goto restore_user_err;
+      
+      /* We have to get very specific packet size  */  
+      if (pkt_len!=SCRAMBLE41_LENGTH) 
+        goto restore_user;
+      
+      /* Final attempt to check the user based on reply */ 
+      if (check_user(thd,COM_CONNECT, tmp_user, (char*)net->read_pos, 
+          tmp_db, 0, 1,prepared_scramble,1,using_password,&cur_priv_version,
+          &cached_user))
+        goto restore_user;
+    }
+    /* Finally we've authenticated new user */
+    if (max_connections && save_uc)
+      decrease_user_connections(save_uc);
+    x_free((gptr) save_db);
+    x_free((gptr) save_user);
+    thd->password=using_password;
+    break;
+    
+    /* Bad luck  we shall restore old user */
+    restore_user_err:
+    send_error(thd, ER_UNKNOWN_COM_ERROR);
+    
+    restore_user:
     x_free(thd->user);
     x_free(thd->db);
     thd->master_access=save_master_access;
@@ -1064,13 +1153,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
     thd->priv_user=save_priv_user;    
     break;
   }
-    if (max_connections && save_uc)
-      decrease_user_connections(save_uc);
-    x_free((gptr) save_db);
-    x_free((gptr) save_user);
-    thd->password=test(passwd[0]);
-    break;
-  }
+  
   case COM_EXECUTE:
   {
     mysql_stmt_execute(thd, packet);