database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-08-05 15:55:57 +03:00
Code Activity

Add the "PRAGMA secure_delete=FAST" option, which overwrites most deleted

Browse Source 
content without increasing the amount of I/O.  Deleted content might persist
on the free page list, however.  And extra CPU cycles are used for zeroing,
of course.

FossilOrigin-Name: 38978ce65b280bb7cba3fc08ba91485fb1b84cd9fbba2e950ecf41c021ff452a
This commit is contained in:
drh
2017-07-07 20:06:28 +00:00
parent a690ff360b a5907a86b8
commit 08f1efeb16
5 changed files with 51 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

39
src/btree.c
View File

@@ -1640,7 +1640,7 @@ static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
/* Overwrite deleted information with zeros when the secure_delete
** option is enabled */
if( pPage->pBt->btsFlags & BTS_SECURE_DELETE ){
if( pPage->pBt->btsFlags & BTS_FAST_SECURE ){
memset(&data[iStart], 0, iSize);
}
@@ -1931,7 +1931,7 @@ static void zeroPage(MemPage *pPage, int flags){
assert( sqlite3PagerGetData(pPage->pDbPage) == data );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( sqlite3_mutex_held(pBt->mutex) );
if( pBt->btsFlags & BTS_SECURE_DELETE ){
if( pBt->btsFlags & BTS_FAST_SECURE ){
memset(&data[hdr], 0, pBt->usableSize - hdr);
}
data[hdr] = (char)flags;
@@ -2354,8 +2354,10 @@ int sqlite3BtreeOpen(
pBt->pCursor = 0;
pBt->pPage1 = 0;
if( sqlite3PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
#ifdef SQLITE_SECURE_DELETE
#if defined(SQLITE_SECURE_DELETE)
pBt->btsFlags |= BTS_SECURE_DELETE;
#elif defined(SQLITE_FAST_SECURE_DELETE)
pBt->btsFlags |= BTS_OVERWRITE;
#endif
/* EVIDENCE-OF: R-51873-39618 The page size for a database file is
** determined by the 2-byte integer located at an offset of 16 bytes from
@@ -2803,19 +2805,34 @@ int sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
}
/*
** Set the BTS_SECURE_DELETE flag if newFlag is 0 or 1. If newFlag is -1,
** then make no changes. Always return the value of the BTS_SECURE_DELETE
** setting after the change.
** Change the values for the BTS_SECURE_DELETE and BTS_OVERWRITE flags:
**
** newFlag==0 Both BTS_SECURE_DELETE and BTS_OVERWRITE are cleared
** newFlag==1 BTS_SECURE_DELETE set and BTS_OVERWRITE is cleared
** newFlag==2 BTS_SECURE_DELETE cleared and BTS_OVERWRITE is set
** newFlag==(-1) No changes
**
** This routine acts as a query if newFlag is less than zero
**
** With BTS_OVERWRITE set, deleted content is overwritten by zeros, but
** freelist leaf pages are not written back to the database. Thus in-page
** deleted content is cleared, but freelist deleted content is not.
**
** With BTS_SECURE_DELETE, operation is like BTS_OVERWRITE with the addition
** that freelist leaf pages are written back into the database, increasing
** the amount of disk I/O.
*/
int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
int b;
if( p==0 ) return 0;
sqlite3BtreeEnter(p);
assert( BTS_OVERWRITE==BTS_SECURE_DELETE*2 );
assert( BTS_FAST_SECURE==(BTS_OVERWRITE|BTS_SECURE_DELETE) );
if( newFlag>=0 ){
p->pBt->btsFlags &= ~BTS_SECURE_DELETE;
if( newFlag ) p->pBt->btsFlags |= BTS_SECURE_DELETE;
}
b = (p->pBt->btsFlags & BTS_SECURE_DELETE)!=0;
p->pBt->btsFlags &= ~BTS_FAST_SECURE;
p->pBt->btsFlags |= BTS_SECURE_DELETE*newFlag;
}
b = (p->pBt->btsFlags & BTS_FAST_SECURE)/BTS_SECURE_DELETE;
sqlite3BtreeLeave(p);
return b;
}
@@ -7210,7 +7227,7 @@ static int balance_nonroot(
** In this case, temporarily copy the cell into the aOvflSpace[]
** buffer. It will be copied out again as soon as the aSpace[] buffer
** is allocated. */
if( pBt->btsFlags & BTS_SECURE_DELETE ){
if( pBt->btsFlags & BTS_FAST_SECURE ){
int iOff;
iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);