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Overview
| Comment: | Prevent the printf formatter from doing large memory allocations - larger than either the size of the static buffer for interfaces like sqlite3_snprintf(), or larger than SQLITE_LIMIT_LENGTH for interfaces that are associated with a database connection. This helps to prevent DOS attacks on products that let hostile sources inject arbitrary SQL. It also helps fuzzers run faster and more effectively. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
179e5d46054e5c86f53a79b7a0823d9a |
| User & Date: | drh 2019-02-01 20:29:04 |
Context
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2019-02-01
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| 21:08 | Slight adjustment to the printf formatter large memory allocation detector so that it does not overestimate the amount of space needed for oversize %d conversions. (check-in: 1aee70d6 user: drh tags: trunk) | |
| 20:29 | Prevent the printf formatter from doing large memory allocations - larger than either the size of the static buffer for interfaces like sqlite3_snprintf(), or larger than SQLITE_LIMIT_LENGTH for interfaces that are associated with a database connection. This helps to prevent DOS attacks on products that let hostile sources inject arbitrary SQL. It also helps fuzzers run faster and more effectively. (check-in: 179e5d46 user: drh tags: trunk) | |
| 18:46 | Performance improvement in the parsing of options to %-formats in the printf implementation. (check-in: 40d8f8ae user: drh tags: trunk) | |
Changes
Changes to src/printf.c.
151 151 return sqlite3_value_double(p->apArg[p->nUsed++]); 152 152 } 153 153 static char *getTextArg(PrintfArguments *p){ 154 154 if( p->nArg<=p->nUsed ) return 0; 155 155 return (char*)sqlite3_value_text(p->apArg[p->nUsed++]); 156 156 } 157 157 158 +/* 159 +** Allocate memory for a temporary buffer needed for printf rendering. 160 +** 161 +** If the requested size of the temp buffer is larger than the size 162 +** of the output buffer in pAccum, then cause an SQLITE_TOOBIG error. 163 +** Do the size check before the memory allocation to prevent rogue 164 +** SQL from requesting large allocations using the precision or width 165 +** field of the printf() function. 166 +*/ 167 +static char *printfTempBuf(sqlite3_str *pAccum, sqlite3_int64 n){ 168 + char *z; 169 + if( n>pAccum->nAlloc && n>pAccum->mxAlloc ){ 170 + setStrAccumError(pAccum, SQLITE_TOOBIG); 171 + return 0; 172 + } 173 + z = sqlite3DbMallocRaw(pAccum->db, n); 174 + if( z==0 ){ 175 + setStrAccumError(pAccum, SQLITE_NOMEM); 176 + } 177 + return z; 178 +} 158 179 159 180 /* 160 181 ** On machines with a small stack size, you can redefine the 161 182 ** SQLITE_PRINT_BUF_SIZE to be something smaller, if desired. 162 183 */ 163 184 #ifndef SQLITE_PRINT_BUF_SIZE 164 185 # define SQLITE_PRINT_BUF_SIZE 70 ................................................................................ 418 439 precision = width-(prefix!=0); 419 440 } 420 441 if( precision<etBUFSIZE-10-etBUFSIZE/3 ){ 421 442 nOut = etBUFSIZE; 422 443 zOut = buf; 423 444 }else{ 424 445 u64 n = (u64)precision + 10 + precision/3; 425 - zOut = zExtra = sqlite3Malloc( n ); 426 - if( zOut==0 ){ 427 - setStrAccumError(pAccum, SQLITE_NOMEM); 428 - return; 429 - } 446 + zOut = zExtra = printfTempBuf(pAccum, n); 447 + if( zOut==0 ) return; 430 448 nOut = (int)n; 431 449 } 432 450 bufpt = &zOut[nOut-1]; 433 451 if( xtype==etORDINAL ){ 434 452 static const char zOrd[] = "thstndrd"; 435 453 int x = (int)(longvalue % 10); 436 454 if( x>=4 || (longvalue/10)%10==1 ){ ................................................................................ 541 559 flag_rtz = flag_altform2; 542 560 } 543 561 if( xtype==etEXP ){ 544 562 e2 = 0; 545 563 }else{ 546 564 e2 = exp; 547 565 } 548 - if( MAX(e2,0)+(i64)precision+(i64)width > etBUFSIZE - 15 ){ 549 - bufpt = zExtra 550 - = sqlite3Malloc( MAX(e2,0)+(i64)precision+(i64)width+15 ); 551 - if( bufpt==0 ){ 552 - setStrAccumError(pAccum, SQLITE_NOMEM); 553 - return; 566 + { 567 + i64 szBufNeeded; /* Size of a temporary buffer needed */ 568 + szBufNeeded = MAX(e2,0)+(i64)precision+(i64)width+15; 569 + if( szBufNeeded > etBUFSIZE ){ 570 + bufpt = zExtra = printfTempBuf(pAccum, szBufNeeded); 571 + if( bufpt==0 ) return; 554 572 } 555 573 } 556 574 zOut = bufpt; 557 575 nsd = 16 + flag_altform2*10; 558 576 flag_dp = (precision>0 ?1:0) | flag_alternateform | flag_altform2; 559 577 /* The sign in front of the number */ 560 578 if( prefix ){ ................................................................................ 770 788 if( flag_altform2 && (ch&0xc0)==0xc0 ){ 771 789 while( (escarg[i+1]&0xc0)==0x80 ){ i++; } 772 790 } 773 791 } 774 792 needQuote = !isnull && xtype==etSQLESCAPE2; 775 793 n += i + 3; 776 794 if( n>etBUFSIZE ){ 777 - bufpt = zExtra = sqlite3Malloc( n ); 778 - if( bufpt==0 ){ 779 - setStrAccumError(pAccum, SQLITE_NOMEM); 780 - return; 781 - } 795 + bufpt = zExtra = printfTempBuf(pAccum, n); 796 + if( bufpt==0 ) return; 782 797 }else{ 783 798 bufpt = buf; 784 799 } 785 800 j = 0; 786 801 if( needQuote ) bufpt[j++] = q; 787 802 k = i; 788 803 for(i=0; i<k; i++){