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Experimental "PRAGMA secure_delete=FAST" pragma. The intent is to overwrite

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deleted content with zeros without increasing the amount of disk I/O.

FossilOrigin-Name: f1682f0faf1a93ded066464b1ddd5f987e21ee0f6bb5e828ed31c3ad903cf2c3
This commit is contained in:
drh 2017-06-19 11:44:22 +00:00
parent 40db2fd7a3
commit a5907a86b8
5 changed files with 53 additions and 27 deletions
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19
manifest
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@ -1,5 +1,5 @@
C Fix\sa\smissing\scomma\sin\sthe\sprevious\scheck-in.
D 2017-06-17T18:49:50.823
C Experimental\s"PRAGMA\ssecure_delete=FAST"\spragma.\s\sThe\sintent\sis\sto\soverwrite\ndeleted\scontent\swith\szeros\swithout\sincreasing\sthe\samount\sof\sdisk\sI/O.
D 2017-06-19T11:44:22.399
F Makefile.in 1cc758ce3374a32425e4d130c2fe7b026b20de5b8843243de75f087c0a2661fb
F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
F Makefile.msc 8eeb80162074004e906b53d7340a12a14c471a83743aab975947e95ce061efcc
@ -348,9 +348,9 @@ F src/auth.c 79f96c6f33bf0e5da8d1c282cee5ebb1852bb8a6ccca3e485d7c459b035d9c3c
F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
F src/btree.c 430e34151e6ef37e42d3f956bb062907c80ff91e1380704b967b8c1a02a98f64
F src/btree.c 127ae15b6328376fa549a2ead30a3ec20db31fe991a287c42cf394965f55fff0
F src/btree.h 3edc5329bc59534d2d15b4f069a9f54b779a7e51289e98fa481ae3c0e526a5ca
F src/btreeInt.h a392d353104b4add58b4a59cb185f5d5693dde832c565b77d8d4c343ed98f610
F src/btreeInt.h 97700795edf8a43245720414798b7b29d8e465aef46bf301ffacd431910c0da1
F src/build.c 88a8cdc11d1c081ed565aa3e795bdf9160f4556463b4c4555e9860b59dd80340
F src/callback.c 2e76147783386374bf01b227f752c81ec872d730
F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
@ -398,7 +398,7 @@ F src/parse.y 0513387ce02fea97897d8caef82d45f347818593f24f1bdc48e0c530a8af122d
F src/pcache.c 62835bed959e2914edd26afadfecce29ece0e870
F src/pcache.h 521bb9610d38ef17a3cc9b5ddafd4546c2ea67fa3d0e464823d73c2a28d50e11
F src/pcache1.c 1195a21fe28e223e024f900b2011e80df53793f0356a24caace4188b098540dc
F src/pragma.c 2362670a9d28b71708aecb2b9b10b3f7be71f4c950961c07e81dc400e3ce6371
F src/pragma.c b5483eba1898652d330231164c17624a93e7a991b2f5c7e8a80f9d85528b308c
F src/pragma.h 37a1311d0388db480388d7ec09054f7103045eff20d4971f8a433b77f40b9921
F src/prepare.c b1140c3d0cf59bc85ace00ce363153041b424b7a
F src/printf.c 8757834f1b54dae512fb25eb1acc8e94a0d15dd2290b58f2563f65973265adb2
@ -1583,7 +1583,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
P 9a443397a6b110f60cae32e1f758914d72931e16ddb423e4d4a119df526bf340
R 48cf46cf5e03c592f1eb729aae9e27b1
P f3db02f49073c3f08c3fd7816d85e5472d5e22df20d862fe4886eb2a97efb15f
R bfe3d3db972c98c6ca95dc686a1c98c9
T *branch * fast-secure-delete
T *sym-fast-secure-delete *
T -sym-trunk *
U drh
Z 1075564756c6da5b66b28900b7b4b32b
Z 1665a7b13a5f9ef4377c01699ae7453e

2
manifest.uuid
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@ -1 +1 @@
f3db02f49073c3f08c3fd7816d85e5472d5e22df20d862fe4886eb2a97efb15f
f1682f0faf1a93ded066464b1ddd5f987e21ee0f6bb5e828ed31c3ad903cf2c3

39
src/btree.c
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@ -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);

10
src/btreeInt.h
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@ -448,10 +448,12 @@ struct BtShared {
#define BTS_READ_ONLY 0x0001 /* Underlying file is readonly */
#define BTS_PAGESIZE_FIXED 0x0002 /* Page size can no longer be changed */
#define BTS_SECURE_DELETE 0x0004 /* PRAGMA secure_delete is enabled */
#define BTS_INITIALLY_EMPTY 0x0008 /* Database was empty at trans start */
#define BTS_NO_WAL 0x0010 /* Do not open write-ahead-log files */
#define BTS_EXCLUSIVE 0x0020 /* pWriter has an exclusive lock */
#define BTS_PENDING 0x0040 /* Waiting for read-locks to clear */
#define BTS_OVERWRITE 0x0008 /* Overwrite deleted content with zeros */
#define BTS_FAST_SECURE 0x000c /* Combination of the previous two */
#define BTS_INITIALLY_EMPTY 0x0010 /* Database was empty at trans start */
#define BTS_NO_WAL 0x0020 /* Do not open write-ahead-log files */
#define BTS_EXCLUSIVE 0x0040 /* pWriter has an exclusive lock */
#define BTS_PENDING 0x0080 /* Waiting for read-locks to clear */
/*
** An instance of the following structure is used to hold information

10
src/pragma.c
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@ -515,18 +515,22 @@ void sqlite3Pragma(
/*
** PRAGMA [schema.]secure_delete
** PRAGMA [schema.]secure_delete=ON/OFF
** PRAGMA [schema.]secure_delete=ON/OFF/FAST
**
** The first form reports the current setting for the
** secure_delete flag. The second form changes the secure_delete
** flag setting and reports thenew value.
** flag setting and reports the new value.
*/
case PragTyp_SECURE_DELETE: {
Btree *pBt = pDb->pBt;
int b = -1;
assert( pBt!=0 );
if( zRight ){
b = sqlite3GetBoolean(zRight, 0);
if( sqlite3_stricmp(zRight, "fast")==0 ){
b = 2;
}else{
b = sqlite3GetBoolean(zRight, 0);
}
}
if( pId2->n==0 && b>=0 ){
int ii;