Subject: Add extra defenses against strategically corrupt databases to fts3/4.
From: Dan Kennedy <[email-masked]>
Date: Sat, 3 Nov 2018 16:51:30 +0000 (+0000)

Add extra defenses against strategically corrupt databases to fts3/4.

https://sqlite.org/src/info/940f2adc8541a838

Upstream-Status: Backport
CVE: CVE-2018-20506
Affects <= 3.26.0

Signed-off-by: Armin Kuster <[email-masked]>

Index: sqlite-autoconf-3230100/sqlite3.c
===================================================================
--- sqlite-autoconf-3230100.orig/sqlite3.c
+++ sqlite-autoconf-3230100/sqlite3.c
@@ -152368,7 +152368,7 @@ static int fts3ScanInteriorNode(
   const char *zCsr = zNode;       /* Cursor to iterate through node */
   const char *zEnd = &zCsr[nNode];/* End of interior node buffer */
   char *zBuffer = 0;              /* Buffer to load terms into */
-  int nAlloc = 0;                 /* Size of allocated buffer */
+  i64 nAlloc = 0;                 /* Size of allocated buffer */
   int isFirstTerm = 1;            /* True when processing first term on page */
   sqlite3_int64 iChild;           /* Block id of child node to descend to */
 
@@ -152406,14 +152406,14 @@ static int fts3ScanInteriorNode(
     zCsr += fts3GetVarint32(zCsr, &nSuffix);
     
     assert( nPrefix>=0 && nSuffix>=0 );
-    if( &zCsr[nSuffix]>zEnd ){
+    if( nPrefix>zCsr-zNode || nSuffix>zEnd-zCsr ){
       rc = FTS_CORRUPT_VTAB;
       goto finish_scan;
     }
-    if( nPrefix+nSuffix>nAlloc ){
+    if( (i64)nPrefix+nSuffix>nAlloc ){
       char *zNew;
-      nAlloc = (nPrefix+nSuffix) * 2;
-      zNew = (char *)sqlite3_realloc(zBuffer, nAlloc);
+      nAlloc = ((i64)nPrefix+nSuffix) * 2;
+      zNew = (char *)sqlite3_realloc64(zBuffer, nAlloc);
       if( !zNew ){
         rc = SQLITE_NOMEM;
         goto finish_scan;
@@ -162012,15 +162012,19 @@ static int fts3SegReaderNext(
   ** safe (no risk of overread) even if the node data is corrupted. */
   pNext += fts3GetVarint32(pNext, &nPrefix);
   pNext += fts3GetVarint32(pNext, &nSuffix);
-  if( nPrefix<0 || nSuffix<=0 
-   || &pNext[nSuffix]>&pReader->aNode[pReader->nNode] 
+  if( nSuffix<=0 
+   || (&pReader->aNode[pReader->nNode] - pNext)<nSuffix
+   || nPrefix>pReader->nTermAlloc
   ){
     return FTS_CORRUPT_VTAB;
   }
 
-  if( nPrefix+nSuffix>pReader->nTermAlloc ){
-    int nNew = (nPrefix+nSuffix)*2;
-    char *zNew = sqlite3_realloc(pReader->zTerm, nNew);
+  /* Both nPrefix and nSuffix were read by fts3GetVarint32() and so are
+  ** between 0 and 0x7FFFFFFF. But the sum of the two may cause integer
+  ** overflow - hence the (i64) casts.  */
+  if( (i64)nPrefix+nSuffix>(i64)pReader->nTermAlloc ){
+    i64 nNew = ((i64)nPrefix+nSuffix)*2;
+    char *zNew = sqlite3_realloc64(pReader->zTerm, nNew);
     if( !zNew ){
       return SQLITE_NOMEM;
     }
@@ -162042,7 +162046,7 @@ static int fts3SegReaderNext(
   ** b-tree node. And that the final byte of the doclist is 0x00. If either 
   ** of these statements is untrue, then the data structure is corrupt.
   */
-  if( &pReader->aDoclist[pReader->nDoclist]>&pReader->aNode[pReader->nNode] 
+  if( (&pReader->aNode[pReader->nNode] - pReader->aDoclist)<pReader->nDoclist
    || (pReader->nPopulate==0 && pReader->aDoclist[pReader->nDoclist-1])
   ){
     return FTS_CORRUPT_VTAB;
@@ -164367,7 +164371,9 @@ static int nodeReaderNext(NodeReader *p)
       p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nPrefix);
     }
     p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nSuffix);
-
+    if( nPrefix>p->iOff || nSuffix>p->nNode-p->iOff ){
+      return SQLITE_CORRUPT_VTAB;
+    }
     blobGrowBuffer(&p->term, nPrefix+nSuffix, &rc);
     if( rc==SQLITE_OK ){
       memcpy(&p->term.a[nPrefix], &p->aNode[p->iOff], nSuffix);
@@ -164375,6 +164381,9 @@ static int nodeReaderNext(NodeReader *p)
       p->iOff += nSuffix;
       if( p->iChild==0 ){
         p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &p->nDoclist);
+        if( (p->nNode-p->iOff)<p->nDoclist ){
+          return SQLITE_CORRUPT_VTAB;
+        }
         p->aDoclist = &p->aNode[p->iOff];
         p->iOff += p->nDoclist;
       }