Avoid a buffer overread in vdbeCompareRecordInt() that might occur if the database is corrupt.

FossilOrigin-Name: 7c0b4381f0e6f33cb13299a915851d9431bf3850

manifest

@@ -1,5 +1,5 @@
-C Fix\sa\stypo\sin\sa\scomment.\s\sNo\schanges\sto\scode.
-D 2014-03-03T19:29:28.807
+C Avoid\sa\sbuffer\soverread\sin\svdbeCompareRecordInt()\sthat\smight\soccur\sif\sthe\sdatabase\sis\scorrupt.
+D 2014-03-03T20:48:50.982
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2ef13430cd359f7b361bb863504e227b25cc7f81
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -281,7 +281,7 @@ F src/vdbe.c 75c3f5d27ab79af214646cf37d7551bc8cec09c2
 F src/vdbe.h d189f92468a17a6f04daeec9df3b767f50557b21
 F src/vdbeInt.h 9ccca0bc7646c918d065943e44bead4bf5de213d
 F src/vdbeapi.c 5bc41aaea448a7fc250902c418f1795859be3820
-F src/vdbeaux.c b817480055ea37f04cbda6524cbcda56d8620c78
+F src/vdbeaux.c 687165bd405b33553c9aaf5da74c249cea083d24
 F src/vdbeblob.c d939997de046b8fcc607cfee4248f3d33dbcca50
 F src/vdbemem.c 2d7918e4c80546d943414668b1485b2581f58a28
 F src/vdbesort.c 46801acb342e5e4c07ba1777fe58880c143abb59
@@ -404,6 +404,7 @@ F test/corruptE.test 193b4ca4e927e77c1d5f4f56203ddc998432a7ee
 F test/corruptF.test be9fde98e4c93648f1ba52b74e5318edc8f59fe4
 F test/corruptG.test 58ec333a01997fe655e34e5bea52b7a2a6b9704d
 F test/corruptH.test 9d8186f6f8751efdfd445d8546fd98f073499039
+F test/corruptI.test d9eca60cb373215d97e0994bf104f9a37e1ac0fc
 F test/count.test 42a251178e32f617eda33f76236a7f79825a50b5
 F test/coveridxscan.test cdb47d01acc4a634a34fd25abe85189e0d0f1e62
 F test/crash.test fb9dc4a02dcba30d4aa5c2c226f98b220b2b959f
@@ -1153,7 +1154,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P ba8993727e5752cbc92c7d78437e9e0510c899f7
-R 84a57b7d3530d77238186688acf2fb15
-U drh
-Z 743719e98998c2037f212aec24c916c8
+P 1f4991ab1676bf85599fc32068ceeddeb05f648c
+R 112194c4c042293d2f5fc41663c08a7a
+U dan
+Z e0c8dc8360525071b6a4931f6b50a318

manifest.uuid

@@ -1 +1 @@
-1f4991ab1676bf85599fc32068ceeddeb05f648c
+7c0b4381f0e6f33cb13299a915851d9431bf3850

src/vdbeaux.c

@@ -3575,7 +3575,8 @@ static int vdbeRecordCompareInt(
   const UnpackedRecord *pPKey2, /* Right key */
   int bSkip                     /* Ignored */
 ){
-  const u8 *aKey = &((const u8*)pKey1)[*(const u8*)pKey1];
+  int szHdr = *(const u8*)pKey1;
+  const u8 *aKey = &((const u8*)pKey1)[*(const u8*)pKey1 & 0x3F];
   int serial_type = ((const u8*)pKey1)[1];
   int res;
   i64 v = pPKey2->aMem[0].u.i;
@@ -3583,7 +3584,6 @@ static int vdbeRecordCompareInt(
   UNUSED_PARAMETER(bSkip);
 
   assert( bSkip==0 );
-
   switch( serial_type ){
     case 1:
       lhs = (char)(aKey[0]);
@@ -3718,12 +3718,20 @@ static int vdbeRecordCompareString(
 ** as the only argument.
 */
 RecordCompare sqlite3VdbeFindCompare(UnpackedRecord *p){
-  /* As the varints that make up a record header are all 5 bytes in size
-  ** or less, if the binary keys being compared have 25 or fewer fields 
-  ** then it is guaranteed that the varint at the start of every record 
-  ** (the record-header size in bytes) fits in a single byte. If this
-  ** is not the case, then sqlite3VdbeRecordCompare() must be used.  */
-  if( (p->pKeyInfo->nField + p->pKeyInfo->nXField)<=25 ){
+  /* varintRecordCompareInt() and varintRecordCompareString() both assume
+  ** that the size-of-header varint that occurs at the start of each record
+  ** fits in a single byte (i.e. is 127 or less). varintRecordCompareInt()
+  ** also assumes that it is safe to overread a buffer by at least the 
+  ** maximum possible legal header size plus 8 bytes. Because there is
+  ** guaranteed to be at least 74 (but not 136) bytes of padding following each
+  ** buffer passed to varintRecordCompareInt() this makes it convenient to
+  ** limit the size of the header to 64 bytes in cases where the first field
+  ** is an integer.
+  **
+  ** The easiest way to enforce this limit is to consider only records with
+  ** 13 fields or less. If the first field is an integer, the maximum legal
+  ** header size is (12*5 + 1 + 1) bytes.  */
+  if( (p->pKeyInfo->nField + p->pKeyInfo->nXField)<=13 ){
     int flags = p->aMem[0].flags;
     if( p->pKeyInfo->aSortOrder[0] ){
       p->r1 = 1;

test/corruptI.test

@@ -0,0 +1,47 @@
+# 2014-01-20
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix corruptI
+
+# Do not use a codec for tests in this file, as the database file is
+# manipulated directly using tcl scripts (using the [hexio_write] command).
+#
+do_not_use_codec
+database_may_be_corrupt
+
+# Initialize the database.
+#
+do_execsql_test 1.1 {
+  PRAGMA page_size=1024;
+  PRAGMA auto_vacuum=0;
+  CREATE TABLE t1(a);
+  CREATE INDEX i1 ON t1(a);
+  INSERT INTO t1 VALUES('a');
+} {}
+db close
+
+do_test 1.2 {
+  set offset [hexio_get_int [hexio_read test.db [expr 2*1024 + 8] 2]]
+  set off [expr 2*1024 + $offset + 1]
+  hexio_write test.db $off FF06
+
+  breakpoint
+
+  sqlite3 db test.db
+  catchsql { SELECT * FROM t1 WHERE a = 10 }
+} {1 {database disk image is malformed}}
+
+
+finish_test
+