Avoid bugs in some implementations of dlopen() by avoiding calls to

dlopen() with a filename argument that exceeds FILENAME_MAX bytes.
[forum:/forumpost/08a0d6d9bf|Forum post 08a0d6d9bf].

FossilOrigin-Name: 01f3877c7172d52225705d2461addc6129fe9cdb04e6f643518fc74bb4b526e4

manifest

@@ -1,5 +1,5 @@
-C Fix\sa\scrash\sin\snew\sALTER\sTABLE\scode\sthat\scould\sfollow\san\sOOM.
-D 2021-06-11T12:14:58.334
+C Avoid\sbugs\sin\ssome\simplementations\sof\sdlopen()\sby\savoiding\scalls\sto\ndlopen()\swith\sa\sfilename\sargument\sthat\sexceeds\sFILENAME_MAX\sbytes.\n[forum:/forumpost/08a0d6d9bf|Forum\spost\s08a0d6d9bf].
+D 2021-06-11T12:41:14.442
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -507,7 +507,7 @@ F src/hwtime.h cb1d7e3e1ed94b7aa6fde95ae2c2daccc3df826be26fc9ed7fd90d1750ae6144
 F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
 F src/insert.c 2189e0e596010a0dc5405d9f14f78db1ee2fa71138c931f5b6ea96610b95bfc1
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
-F src/loadext.c 8c9c8cd2bd8eecdb06d9b6e89de7e9e65bae45cc8fc33609cc74023a5c296067
+F src/loadext.c 12684b3f19cd103cea97cdf14d0758196d0c646e12a898d7245141a9abfde9a4
 F src/main.c 7a1b7017af16977b298ef5a0b824b1153f1c878f94885a098620c3c1b1078ce9
 F src/malloc.c cbc93cdd429c4594912017d92ab656e2579aca64dbd1c6888551275bed46f25b
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
@@ -524,8 +524,8 @@ F src/mutex_noop.c 9d4309c075ba9cc7249e19412d3d62f7f94839c4
 F src/mutex_unix.c dd2b3f1cc1863079bc1349ac0fec395a500090c4fe4e11ab775310a49f2f956d
 F src/mutex_w32.c caa50e1c0258ac4443f52e00fe8aaea73b6d0728bd8856bedfff822cae418541
 F src/notify.c 89a97dc854c3aa62ad5f384ef50c5a4a11d70fcc69f86de3e991573421130ed6
-F src/os.c 6e94cd64b134c9317e52ad534117578e3df66ec180d70dbf4b1d7eb1db8e5a5d
-F src/os.h 48388821692e87da174ea198bf96b1b2d9d83be5dfc908f673ee21fafbe0d432
+F src/os.c 59ed1f503347e8b5434c0ce7d7d0f02a3f24a72fea8b26d0bba2de8dfaef778b
+F src/os.h 26890f540b475598cd9881dcc68931377b8d429d3ea3e2eeb64470cde64199f8
 F src/os_common.h b2f4707a603e36811d9b1a13278bffd757857b85
 F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
 F src/os_unix.c efa60c1cb54dba767abbba3c6dd67d3df5ef8aa26e2e499c37f055f56a374068
@@ -1918,7 +1918,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 852ee0e91ceae090157c4ab2805530f5d7985a490ce77f54d7b148f56e466f79
-R 4908855f822587627e5ff1f9cc5f199c
-U dan
-Z 6050252f76b9f756fd3413a1f8f80a55
+P 6f1f2a0a9cd75ca43b81cc325296b843ccefe6f8040da8f2e873f49928423f10
+R 23cea976e993f7dc439db4b62b27e10a
+U drh
+Z 412447a47d8555a8bfce30ac9e03c884

manifest.uuid

@@ -1 +1 @@
-6f1f2a0a9cd75ca43b81cc325296b843ccefe6f8040da8f2e873f49928423f10
+01f3877c7172d52225705d2461addc6129fe9cdb04e6f643518fc74bb4b526e4

src/loadext.c

@@ -515,7 +515,7 @@ static int sqlite3LoadExtension(
   const char *zEntry;
   char *zAltEntry = 0;
   void **aHandle;
-  u64 nMsg = 300 + sqlite3Strlen30(zFile);
+  u64 nMsg = strlen(zFile);
   int ii;
   int rc;
 
@@ -549,6 +549,12 @@ static int sqlite3LoadExtension(
 
   zEntry = zProc ? zProc : "sqlite3_extension_init";
 
+  /* tag-20210611-1.  Some dlopen() implementations will segfault if given
+  ** an oversize filename.  Most filesystems have a pathname limit of 4K,
+  ** so limit the extension filename length to about twice that.
+  ** https://sqlite.org/forum/forumpost/08a0d6d9bf */
+  if( nMsg>SQLITE_MAX_PATHLEN ) goto extension_not_found;
+    
   handle = sqlite3OsDlOpen(pVfs, zFile);
 #if SQLITE_OS_UNIX || SQLITE_OS_WIN
   for(ii=0; ii<ArraySize(azEndings) && handle==0; ii++){
@@ -558,17 +564,7 @@ static int sqlite3LoadExtension(
     sqlite3_free(zAltFile);
   }
 #endif
-  if( handle==0 ){
-    if( pzErrMsg ){
-      *pzErrMsg = zErrmsg = sqlite3_malloc64(nMsg);
-      if( zErrmsg ){
-        sqlite3_snprintf(nMsg, zErrmsg, 
-            "unable to open shared library [%s]", zFile);
-        sqlite3OsDlError(pVfs, nMsg-1, zErrmsg);
-      }
-    }
-    return SQLITE_ERROR;
-  }
+  if( handle==0 ) goto extension_not_found;
   xInit = (sqlite3_loadext_entry)sqlite3OsDlSym(pVfs, handle, zEntry);
 
   /* If no entry point was specified and the default legacy
@@ -605,10 +601,11 @@ static int sqlite3LoadExtension(
   }
   if( xInit==0 ){
     if( pzErrMsg ){
-      nMsg += sqlite3Strlen30(zEntry);
+      nMsg += strlen(zEntry) + 300;
       *pzErrMsg = zErrmsg = sqlite3_malloc64(nMsg);
       if( zErrmsg ){
-        sqlite3_snprintf(nMsg, zErrmsg,
+        assert( nMsg<0x7fffffff );  /* zErrmsg would be NULL if not so */
+        sqlite3_snprintf((int)nMsg, zErrmsg,
             "no entry point [%s] in shared library [%s]", zEntry, zFile);
         sqlite3OsDlError(pVfs, nMsg-1, zErrmsg);
       }
@@ -642,6 +639,19 @@ static int sqlite3LoadExtension(
 
   db->aExtension[db->nExtension++] = handle;
   return SQLITE_OK;
+
+extension_not_found:
+  if( pzErrMsg ){
+    nMsg += 300;
+    *pzErrMsg = zErrmsg = sqlite3_malloc64(nMsg);
+    if( zErrmsg ){
+      assert( nMsg<0x7fffffff );  /* zErrmsg would be NULL if not so */
+      sqlite3_snprintf((int)nMsg, zErrmsg,
+          "unable to open shared library [%.*s]", SQLITE_MAX_PATHLEN, zFile);
+      sqlite3OsDlError(pVfs, nMsg-1, zErrmsg);
+    }
+  }
+  return SQLITE_ERROR;
 }
 int sqlite3_load_extension(
   sqlite3 *db,          /* Load the extension into this database connection */

src/os.c

@@ -252,6 +252,8 @@ int sqlite3OsFullPathname(
 }
 #ifndef SQLITE_OMIT_LOAD_EXTENSION
 void *sqlite3OsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  assert( zPath!=0 );
+  assert( strlen(zPath)<=SQLITE_MAX_PATHLEN );  /* tag-20210611-1 */
   return pVfs->xDlOpen(pVfs, zPath);
 }
 void sqlite3OsDlError(sqlite3_vfs *pVfs, int nByte, char *zBufOut){

src/os.h

@@ -33,6 +33,12 @@
 # define SET_FULLSYNC(x,y)
 #endif
 
+/* Maximum pathname length.  Note: FILENAME_MAX defined by stdio.h
+*/
+#ifndef SQLITE_MAX_PATHLEN
+# define SQLITE_MAX_PATHLEN FILENAME_MAX
+#endif
+
 /*
 ** The default size of a disk sector
 */