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.

FossilOrigin-Name: 179e5d46054e5c86f53a79b7a0823d9a383da8391ad1d3c3b22645927a1e052b

manifest

@@ -1,5 +1,5 @@
-C Performance\simprovement\sin\sthe\sparsing\sof\soptions\sto\s%-formats\sin\sthe\nprintf\simplementation.
-D 2019-02-01T18:46:41.116
+C Prevent\sthe\sprintf\sformatter\sfrom\sdoing\slarge\smemory\sallocations\s-\slarger\nthan\seither\sthe\ssize\sof\sthe\sstatic\sbuffer\sfor\sinterfaces\slike\nsqlite3_snprintf(),\sor\slarger\sthan\sSQLITE_LIMIT_LENGTH\sfor\sinterfaces\sthat\nare\sassociated\swith\sa\sdatabase\sconnection.\s\sThis\shelps\sto\sprevent\sDOS\nattacks\son\sproducts\sthat\slet\shostile\ssources\sinject\sarbitrary\sSQL.\s\sIt\salso\nhelps\sfuzzers\srun\sfaster\sand\smore\seffectively.
+D 2019-02-01T20:29:04.040
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in 178d8eb6840771149cee40b322d1b3be30d330198c522c903c1b66fb5a1bfca4
@@ -510,7 +510,7 @@ F src/pcache1.c fffd5250a323579384a3b3904302b9fe87e186ba24602af3013f749a0234ae98
 F src/pragma.c af67dedaad8bafe9a5f9adcec32a0da6dd118617dd8220ad1d118f5a6bf83a02
 F src/pragma.h b774c8fdd63ed468ab8206b9b530d5d2523ed8889fbb72d1143d09272d5c6b2c
 F src/prepare.c 78027c6231fbb19ca186a5f5f0c0a1375d9c2cec0655273f9bd90d9ff74a34b3
-F src/printf.c fdea5e38f20413dcef9776c12c2d0eb32ea27cb4192a0f71d193574852631c60
+F src/printf.c 15c8c8c4095cdfeb6a295630b6914fbb702e68d06fc9fa08ff18cd3db6c35596
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c c8f207247472c41ac73d738e1c1a80719ad253d1dbb617ed57740492b2a6c097
 F src/rowset.c d977b011993aaea002cab3e0bb2ce50cf346000dff94e944d547b989f4b1fe93
@@ -1804,7 +1804,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 4ca9d5d53d41d08fbce29f9da8cc0948df9c4c3136210af88b499cf889b5ccb8
-R 3a0fd1c7830f595fdcbdfa420aaebcd3
+P 40d8f8ae87abf928542c4e558a4c3a3eab18776a3e8db7ca1c5e5f744ca0bce3
+R 39962f884b7a14fe935665eaeaac0027
 U drh
-Z 027c010e323198cb67ddd7c2ea43d1d6
+Z 9dd5bee31b2eabbe1bf794461fb9903d

manifest.uuid

@@ -1 +1 @@
-40d8f8ae87abf928542c4e558a4c3a3eab18776a3e8db7ca1c5e5f744ca0bce3
+179e5d46054e5c86f53a79b7a0823d9a383da8391ad1d3c3b22645927a1e052b

src/printf.c

@@ -155,6 +155,27 @@ static char *getTextArg(PrintfArguments *p){
   return (char*)sqlite3_value_text(p->apArg[p->nUsed++]);
 }
 
+/*
+** Allocate memory for a temporary buffer needed for printf rendering.
+**
+** If the requested size of the temp buffer is larger than the size
+** of the output buffer in pAccum, then cause an SQLITE_TOOBIG error.
+** Do the size check before the memory allocation to prevent rogue
+** SQL from requesting large allocations using the precision or width
+** field of the printf() function.
+*/
+static char *printfTempBuf(sqlite3_str *pAccum, sqlite3_int64 n){
+  char *z;
+  if( n>pAccum->nAlloc && n>pAccum->mxAlloc ){
+    setStrAccumError(pAccum, SQLITE_TOOBIG);
+    return 0;
+  }
+  z = sqlite3DbMallocRaw(pAccum->db, n);
+  if( z==0 ){
+    setStrAccumError(pAccum, SQLITE_NOMEM);
+  }
+  return z;
+}
 
 /*
 ** On machines with a small stack size, you can redefine the
@@ -422,11 +443,8 @@ void sqlite3_str_vappendf(
           zOut = buf;
         }else{
           u64 n = (u64)precision + 10 + precision/3;
-          zOut = zExtra = sqlite3Malloc( n );
-          if( zOut==0 ){
-            setStrAccumError(pAccum, SQLITE_NOMEM);
-            return;
-          }
+          zOut = zExtra = printfTempBuf(pAccum, n);
+          if( zOut==0 ) return;
           nOut = (int)n;
         }
         bufpt = &zOut[nOut-1];
@@ -545,12 +563,12 @@ void sqlite3_str_vappendf(
         }else{
           e2 = exp;
         }
-        if( MAX(e2,0)+(i64)precision+(i64)width > etBUFSIZE - 15 ){
-          bufpt = zExtra 
-              = sqlite3Malloc( MAX(e2,0)+(i64)precision+(i64)width+15 );
-          if( bufpt==0 ){
-            setStrAccumError(pAccum, SQLITE_NOMEM);
-            return;
+        {
+          i64 szBufNeeded;           /* Size of a temporary buffer needed */
+          szBufNeeded = MAX(e2,0)+(i64)precision+(i64)width+15;
+          if( szBufNeeded > etBUFSIZE ){
+            bufpt = zExtra = printfTempBuf(pAccum, szBufNeeded);
+            if( bufpt==0 ) return;
           }
         }
         zOut = bufpt;
@@ -774,11 +792,8 @@ void sqlite3_str_vappendf(
         needQuote = !isnull && xtype==etSQLESCAPE2;
         n += i + 3;
         if( n>etBUFSIZE ){
-          bufpt = zExtra = sqlite3Malloc( n );
-          if( bufpt==0 ){
-            setStrAccumError(pAccum, SQLITE_NOMEM);
-            return;
-          }
+          bufpt = zExtra = printfTempBuf(pAccum, n);
+          if( bufpt==0 ) return;
         }else{
           bufpt = buf;
         }