Sqlite3 Window function函数远程代码执行漏洞 CVE-2019-5018
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- Vulndb
研究人员发现在Sqlite3 3.26.0的Windows函数功能中存在UAF漏洞。通过特殊伪造的SQL命令可以产生该UAF漏洞，导致远程代码执行。攻击者可以发送恶意SQL命令来触发该漏洞。
漏洞详情
SQLite是实现SQL数据库引擎的常用库函数，被广泛应用于移动设备、浏览器、硬件设备、用户应用中。也是小型、快速、可靠数据库解决方案的常用选择。
SQLite实现了SQL的Window Functions特征，允许对行的子集（Subset、window）进行查询。通过分析含有Window函数的SELECT语句，SELECT语句就会使用sqlite3WindowRewrite函数进行转化。
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src/select.c:5643 sqlite3SelectPrep(pParse, p, 0); ... #ifndef SQLITE_OMIT_WINDOWFUNC if( sqlite3WindowRewrite(pParse, p) ){ goto select_end; } |
在该函数中，如果使用了聚合函数（COUNT, MAX, MIN, AVG, SUM），SELECT对象的表达式列表就会被重写。
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src/window.c:747 int sqlite3WindowRewrite(Parse *pParse, Select *p){ int rc = SQLITE_OK; if( p->pWin && p->pPrior==0 ){ ... Window *pMWin = p->pWin; /* Master window object */ Window *pWin; /* Window object iterator */ ... selectWindowRewriteEList(pParse, pMWin /* window */, pSrc, p->pEList, &pSublist); [0] selectWindowRewriteEList(pParse, pMWin /* window */, pSrc, p->pOrderBy, &pSublist); ... pSublist = exprListAppendList(pParse, pSublist, pMWin->pPartition); |
Master Window对象 pMWin是从SELECT对象中取出的，在重写过程中也用到了。这一过程是为了使其处理window函数进行容易。
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src/window.c:692 static void selectWindowRewriteEList( Parse *pParse, Window *pWin, SrcList *pSrc, ExprList *pEList, ExprList **ppSub ){ Walker sWalker; WindowRewrite sRewrite; memset(&sWalker, 0, sizeof(Walker)); memset(&sRewrite, 0, sizeof(WindowRewrite)); sRewrite.pSub = *ppSub; sRewrite.pWin = pWin; // [1] sRewrite.pSrc = pSrc; sWalker.pParse = pParse; sWalker.xExprCallback = selectWindowRewriteExprCb; sWalker.xSelectCallback = selectWindowRewriteSelectCb; sWalker.u.pRewrite = &sRewrite; (void)sqlite3WalkExprList(&sWalker, pEList); *ppSub = sRewrite.pSub; } ```sql Master window对象是在WindowRewrite对象中使用的。在处理每个表达式过程中，xExprCallback函数会用作处理的回调函数。在处理聚合函数（TKAGGFUNCTION）和添加到表达式列表中后，表达式就会被删除。 ```sql src/window.c:602 static int selectWindowRewriteExprCb(Walker *pWalker, Expr *pExpr){ struct WindowRewrite *p = pWalker->u.pRewrite; Parse *pParse = pWalker->pParse; ... switch( pExpr->op ){ ... /* Fall through. */ case TK_AGG_FUNCTION: case TK_COLUMN: { Expr *pDup = sqlite3ExprDup(pParse->db, pExpr, 0); p->pSub = sqlite3ExprListAppend(pParse, p->pSub, pDup); if( p->pSub ){ assert( ExprHasProperty(pExpr, EP_Static)==0 ); ExprSetProperty(pExpr, EP_Static); sqlite3ExprDelete(pParse->db, pExpr); [2] ExprClearProperty(pExpr, EP_Static); memset(pExpr, 0, sizeof(Expr)); pExpr->op = TK_COLUMN; pExpr->iColumn = p->pSub->nExpr-1; pExpr->iTable = p->pWin->iEphCsr; } ... } |
在表达式删除期间，如果表达式被标记为window function，相关的window对象也会被删除。
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src/window.c:1051 static SQLITE_NOINLINE void sqlite3ExprDeleteNN(sqlite3 *db, Expr *p){ ... if( !ExprHasProperty(p, (EP_TokenOnly|EP_Leaf)) ){ ... if( ExprHasProperty(p, EP_WinFunc) ){ assert( p->op==TK_FUNCTION ); sqlite3WindowDelete(db, p->y.pWin); } } 在 Window删除期间，与Window相关的部分都被删除了。 src/window.c:851 void sqlite3WindowDelete(sqlite3 *db, Window *p){ if( p ){ sqlite3ExprDelete(db, p->pFilter); sqlite3ExprListDelete(db, p->pPartition); sqlite3ExprListDelete(db, p->pOrderBy); sqlite3ExprDelete(db, p->pEnd); sqlite3ExprDelete(db, p->pStart); sqlite3DbFree(db, p->zName); sqlite3DbFree(db, p); } } |
可以看一下原始的sqlite3WindowRewrite函数，删除的部分在表达式列表被重写后重用了。
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src/window.c:785 selectWindowRewriteEList(pParse, pMWin, pSrc, p->pEList, &pSublist); [4] selectWindowRewriteEList(pParse, pMWin, pSrc, p->pOrderBy, &pSublist); pMWin->nBufferCol = (pSublist ? pSublist->nExpr : 0); ... pSublist = exprListAppendList(pParse, pSublist, pMWin->pPartition); [5] src/window.c:723 static ExprList *exprListAppendList( Parse *pParse, ExprList *pList, ExprList *pAppend [5] ){ if( pAppend ){ int i; int nInit = pList ? pList->nExpr : 0; for(i=0; i<pAppend->nExpr; i++){ Expr *pDup = sqlite3ExprDup(pParse->db, pAppend->a[i].pExpr, 0); pList = sqlite3ExprListAppend(pParse, pList, pDup); if( pList ) pList->a[nInit+i].sortOrder = pAppend->a[i].sortOrder; } } return pList; } |
这部分被删除后，会在exprListAppendList中被重用，导致UAF漏洞，最终引发DOS。如果攻击者可以控制释放后的内存，那么就可以破坏更多的数据，有可能导致代码执行。
奔溃信息
使用sqlite3 debug版本来破坏释放的缓存的内容可以证明该漏洞的存在。监控0xfafafafafafafafa附近的奔溃可以说明释放的缓存正在被再次访问。
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src/malloc.c:341 void sqlite3DbFreeNN(sqlite3 *db, void *p){ assert( db==0 || sqlite3_mutex_held(db->mutex) ); assert( p!=0 ); if( db ){ ... if( isLookaside(db, p) ){ LookasideSlot *pBuf = (LookasideSlot*)p; /* Trash all content in the buffer being freed */ memset(p, 0xfa, db->lookaside.sz); [5] pBuf->pNext = db->lookaside.pFree; db->lookaside.pFree = pBuf; return; } ```sql 通过gdb sqlite3运行POC: ```sql [─────────────────────REGISTERS──────────────────────] *RAX 0xfafafafafafafafa RBX 0x0 *RCX 0x7fffffd0 RDX 0x0 *RDI 0x7fffffffc3a0 —▸ 0x7ffff79c7340 (funlockfile) ◂— mov rdx, qword ptr [rdi + 0x88] RSI 0x0 R8 0x0 *R9 0x30 R10 0x0 *R11 0x246 *R12 0x401a20 (_start) ◂— xor ebp, ebp *R13 0x7fffffffe000 ◂— 0x2 R14 0x0 R15 0x0 *RBP 0x7fffffffc900 —▸ 0x7fffffffc990 —▸ 0x7fffffffcc10 —▸ 0x7fffffffce90 ◂— ... *RSP 0x7fffffffc8d0 —▸ 0x4db4f5 (selectWindowRewriteSelectCb) ◂— push rbp *RIP 0x4db723 (exprListAppendList+240) ◂— mov eax, dword ptr [rax] [───────────────────────DISASM───────────────────────] ► 0x4db723 <exprListAppendList+240> mov eax, dword ptr [rax] 0x4db725 <exprListAppendList+242> cmp eax, dword ptr [rbp - 0x10] 0x4db728 <exprListAppendList+245> jg exprListAppendList+94 <0x4db691> ↓ 0x4db691 <exprListAppendList+94> mov rax, qword ptr [rbp - 0x28] 0x4db695 <exprListAppendList+98> mov edx, dword ptr [rbp - 0x10] 0x4db698 <exprListAppendList+101> movsxd rdx, edx 0x4db69b <exprListAppendList+104> shl rdx, 5 0x4db69f <exprListAppendList+108> add rax, rdx 0x4db6a2 <exprListAppendList+111> add rax, 8 0x4db6a6 <exprListAppendList+115> mov rcx, qword ptr [rax] 0x4db6a9 <exprListAppendList+118> mov rax, qword ptr [rbp - 0x18] [───────────────────────SOURCE───────────────────────] 145380 ){ 145381 if( pAppend ){ 145382 int i; 145383 int nInit = pList ? pList->nExpr : 0; 145384 printf("pAppend: [%p] -> %p\n", &pAppend, pAppend); 145385 for(i=0; i<pAppend->nExpr; i++){ // BUG-USE 0 145386 Expr *pDup = sqlite3ExprDup(pParse->db, pAppend->a[i].pExpr, 0); 145387 pList = sqlite3ExprListAppend(pParse, pList, pDup); 145388 if( pList ) pList->a[nInit+i].sortOrder = pAppend->a[i].sortOrder; 145389 } [───────────────────────STACK────────────────────────] 00:0000│ rsp 0x7fffffffc8d0 —▸ 0x4db4f5 (selectWindowRewriteSelectCb) ◂— push rbp 01:0008│ 0x7fffffffc8d8 ◂— 0xfafafafafafafafa 02:0010│ 0x7fffffffc8e0 —▸ 0x746d58 ◂— 0x1 03:0018│ 0x7fffffffc8e8 —▸ 0x7fffffffdb30 —▸ 0x73b348 —▸ 0x736c60 (aVfs.13750) ◂— ... 04:0020│ 0x7fffffffc8f0 ◂— 0x100000000 05:0028│ 0x7fffffffc8f8 ◂— 0xce1ae95b8dd44700 06:0030│ rbp 0x7fffffffc900 —▸ 0x7fffffffc990 —▸ 0x7fffffffcc10 —▸ 0x7fffffffce90 ◂— ... 07:0038│ 0x7fffffffc908 —▸ 0x4db994 (sqlite3WindowRewrite+608) ◂— mov qword ptr [rbp - 0x68], rax [─────────────────────BACKTRACE──────────────────────] ► f 0 4db723 exprListAppendList+240 f 1 4db994 sqlite3WindowRewrite+608 |
PoC利用
可以使用sqlite3 shell运行POC
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./sqlite3 -init poc |
https://www.talosintelligence.com/vulnerability_reports/TALOS-2019-0777
原文连接：Sqlite3 Window function函数远程代码执行漏洞 CVE-2019-5018
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