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Overview
Comment:Break out the test for writable shadow tables into a separate subroutine.
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Timelines: family | ancestors | descendants | both | defensive-improvements
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SHA3-256: 8ad34d36a141fa8f5d9bd784dfeb892c983897a6dc6b867607cc668508acf944
User & Date: drh 2019-11-16 13:51:31.727
Context
2019-11-16
14:15
Do not allow CREATE TABLE or CREATE VIEW of an object with a name that looks like a shadow table name. (Closed-Leaf check-in: 6aef58b629 user: drh tags: defensive-improvements)
13:51
Break out the test for writable shadow tables into a separate subroutine. (check-in: 8ad34d36a1 user: drh tags: defensive-improvements)
12:04
Do not allow shadow tables to be dropped in defensive mode. (check-in: 70390bbca4 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/alter.c.
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** in pParse->zErr (system tables may not be altered) and returns non-zero.
**
** Or, if zName is not a system table, zero is returned.
*/
static int isAlterableTable(Parse *pParse, Table *pTab){
  if( 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) 
#ifndef SQLITE_OMIT_VIRTUALTABLE
   || ( (pTab->tabFlags & TF_Shadow) 
     && (pParse->db->flags & SQLITE_Defensive)
     && pParse->db->nVdbeExec==0
   )
#endif
  ){
    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);
    return 1;
  }
  return 0;








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** in pParse->zErr (system tables may not be altered) and returns non-zero.
**
** Or, if zName is not a system table, zero is returned.
*/
static int isAlterableTable(Parse *pParse, Table *pTab){
  if( 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) 
#ifndef SQLITE_OMIT_VIRTUALTABLE
   || ( (pTab->tabFlags & TF_Shadow)!=0

        && sqlite3ReadOnlyShadowTables(pParse->db)
   )
#endif
  ){
    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);
    return 1;
  }
  return 0;
︙︙
Changes to src/build.c.
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    sqlite3VdbeAddOp4(v, OP_VDestroy, iDb, 0, 0, pTab->zName, 0);
    sqlite3MayAbort(pParse);
  }
  sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
  sqlite3ChangeCookie(pParse, iDb);
  sqliteViewResetAll(db, iDb);
}

















/*
** Return true if it is not allowed to drop the given table
*/
static int tableMayNotBeDropped(Parse *pParse, Table *pTab){
  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
    if( sqlite3StrNICmp(pTab->zName+7, "stat", 4)==0 ) return 0;
    if( sqlite3StrNICmp(pTab->zName+7, "parameters", 10)==0 ) return 0;
    return 1;
  }
  if( pTab->tabFlags & TF_Shadow ){
    sqlite3 *db = pParse->db;
    if( (db->flags & SQLITE_Defensive)!=0 && db->nVdbeExec==0 ) return 1;
  }
  return 0;
}

/*
** This routine is called to do the work of a DROP TABLE statement.
** pName is the name of the table to be dropped.








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    sqlite3VdbeAddOp4(v, OP_VDestroy, iDb, 0, 0, pTab->zName, 0);
    sqlite3MayAbort(pParse);
  }
  sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
  sqlite3ChangeCookie(pParse, iDb);
  sqliteViewResetAll(db, iDb);
}

/*
** Return TRUE if shadow tables should be read-only in the current
** context.
*/
int sqlite3ReadOnlyShadowTables(sqlite3 *db){
#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( (db->flags & SQLITE_Defensive)!=0
   && db->pVtabCtx==0
   && db->nVdbeExec==0
  ){
    return 1;
  }
#endif
  return 0;
}

/*
** Return true if it is not allowed to drop the given table
*/
static int tableMayNotBeDropped(sqlite3 *db, Table *pTab){
  if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
    if( sqlite3StrNICmp(pTab->zName+7, "stat", 4)==0 ) return 0;
    if( sqlite3StrNICmp(pTab->zName+7, "parameters", 10)==0 ) return 0;
    return 1;
  }
  if( (pTab->tabFlags & TF_Shadow)!=0 && sqlite3ReadOnlyShadowTables(db) ){

    return 1;
  }
  return 0;
}

/*
** This routine is called to do the work of a DROP TABLE statement.
** pName is the name of the table to be dropped.
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      goto exit_drop_table;
    }
    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
      goto exit_drop_table;
    }
  }
#endif
  if( tableMayNotBeDropped(pParse, pTab) ){
    sqlite3ErrorMsg(pParse, "table %s may not be dropped", pTab->zName);
    goto exit_drop_table;
  }

#ifndef SQLITE_OMIT_VIEW
  /* Ensure DROP TABLE is not used on a view, and DROP VIEW is not used
  ** on a table.








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      goto exit_drop_table;
    }
    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
      goto exit_drop_table;
    }
  }
#endif
  if( tableMayNotBeDropped(db, pTab) ){
    sqlite3ErrorMsg(pParse, "table %s may not be dropped", pTab->zName);
    goto exit_drop_table;
  }

#ifndef SQLITE_OMIT_VIEW
  /* Ensure DROP TABLE is not used on a view, and DROP VIEW is not used
  ** on a table.
︙︙
Changes to src/delete.c.
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  }
  if( (pTab->tabFlags & (TF_Readonly|TF_Shadow))==0 ) return 0;
  db = pParse->db;
  if( (pTab->tabFlags & TF_Readonly)!=0 ){
    return sqlite3WritableSchema(db)==0 && pParse->nested==0;
  }
  assert( pTab->tabFlags & TF_Shadow );
  return (db->flags & SQLITE_Defensive)!=0 
#ifndef SQLITE_OMIT_VIRTUALTABLE
          && db->pVtabCtx==0
#endif
          && db->nVdbeExec==0;
}

/*
** Check to make sure the given table is writable.  If it is not
** writable, generate an error message and return 1.  If it is
** writable return 0;
*/








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  }
  if( (pTab->tabFlags & (TF_Readonly|TF_Shadow))==0 ) return 0;
  db = pParse->db;
  if( (pTab->tabFlags & TF_Readonly)!=0 ){
    return sqlite3WritableSchema(db)==0 && pParse->nested==0;
  }
  assert( pTab->tabFlags & TF_Shadow );
  return sqlite3ReadOnlyShadowTables(db);




}

/*
** Check to make sure the given table is writable.  If it is not
** writable, generate an error message and return 1.  If it is
** writable return 0;
*/
︙︙
Changes to src/sqliteInt.h.
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     const char*,
     const sqlite3_module*,
     void*,
     void(*)(void*)
   );
#  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
#endif

int sqlite3VtabEponymousTableInit(Parse*,Module*);
void sqlite3VtabEponymousTableClear(sqlite3*,Module*);
void sqlite3VtabMakeWritable(Parse*,Table*);
void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*, int);
void sqlite3VtabFinishParse(Parse*, Token*);
void sqlite3VtabArgInit(Parse*);
void sqlite3VtabArgExtend(Parse*, Token*);








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     const char*,
     const sqlite3_module*,
     void*,
     void(*)(void*)
   );
#  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
#endif
int sqlite3ReadOnlyShadowTables(sqlite3 *db);
int sqlite3VtabEponymousTableInit(Parse*,Module*);
void sqlite3VtabEponymousTableClear(sqlite3*,Module*);
void sqlite3VtabMakeWritable(Parse*,Table*);
void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*, int);
void sqlite3VtabFinishParse(Parse*, Token*);
void sqlite3VtabArgInit(Parse*);
void sqlite3VtabArgExtend(Parse*, Token*);
︙︙