Taint: speed up slow-mode is_tainted

[user/henk/code/exim.git] / src / src / store.c

diff --git a/src/src/store.c b/src/src/store.c
index 045f27f8e1218bf7ece27244ebe622f740333535..b65649f4aad1db3c55d976b5f55c09e295554b9d 100644 (file)
--- a/src/src/store.c
+++ b/src/src/store.c
@@ -41,8 +41,30 @@ The following different types of store are recognized:
   and tainted.  The latter is used for values derived from untrusted input, and
   the string-expansion mechanism refuses to operate on such values (obviously,
   it can expand an untainted value to return a tainted result).  The classes
   and tainted.  The latter is used for values derived from untrusted input, and
   the string-expansion mechanism refuses to operate on such values (obviously,
   it can expand an untainted value to return a tainted result).  The classes

-  are implemented by duplicating the three pool types. Pool resets are requested
+  are implemented by duplicating the three pool types.  Pool resets are requested

   against the nontainted sibling and apply to both siblings.
   against the nontainted sibling and apply to both siblings.

+
+  Only memory blocks requested for tainted use are regarded as tainted; anything
+  else (including stack auto variables) is untainted.  Care is needed when coding
+  to not copy untrusted data into untainted memory, as downstream taint-checks
+  would be avoided.
+
+  Internally we currently use malloc for nontainted pools, and mmap for tainted
+  pools.  The disparity is for speed of testing the taintedness of pointers;
+  because Linux appears to use distinct non-overlapping address allocations for
+  mmap vs. everything else, which means only two pointer-compares suffice for the
+  test.  Other OS' cannot use that optimisation, and a more lengthy test against
+  the limits of tainted-pool allcations has to be done.
+
+  Intermediate layers (eg. the string functions) can test for taint, and use this
+  for ensurinng that results have proper state.  For example the
+  string_vformat_trc() routing supporting the string_sprintf() interface will
+  recopy a string being built into a tainted allocation if it meets a %s for a
+  tainted argument.  Any intermediate-layer function that (can) return a new
+  allocation should behave this way; returning a tainted result if any tainted
+  content is used.  Users of functions that modify existing allocations should
+  check if a tainted source and an untainted destination is used, and fail instead
+  (sprintf() being the classic case).

 */
 
 
 */
 
 


@@ -135,6 +157,7 @@ static int max_pool_malloc; /* max value for pool_malloc */
 static int max_nonpool_malloc; /* max value for nonpool_malloc */
 
 
 static int max_nonpool_malloc; /* max value for nonpool_malloc */
 
 

+#ifndef COMPILE_UTILITY

 static const uschar * pooluse[NPOOLS] = {
 [POOL_MAIN] =          US"main",
 [POOL_PERM] =          US"perm",
 static const uschar * pooluse[NPOOLS] = {
 [POOL_MAIN] =          US"main",
 [POOL_PERM] =          US"perm",


@@ -151,16 +174,25 @@ static const uschar * poolclass[NPOOLS] = {
 [POOL_TAINT_PERM] =    US"tainted",
 [POOL_TAINT_SEARCH] =  US"tainted",
 };
 [POOL_TAINT_PERM] =    US"tainted",
 [POOL_TAINT_SEARCH] =  US"tainted",
 };

+#endif

 
 
 static void * store_mmap(int, const char *, int);
 static void * internal_store_malloc(int, const char *, int);
 
 
 static void * store_mmap(int, const char *, int);
 static void * internal_store_malloc(int, const char *, int);

-static void   internal_store_free(void *, const char *, int linenumber);
+static void   internal_untainted_free(void *, const char *, int linenumber);
+static void   internal_tainted_free(storeblock *, const char *, int linenumber);

 
 /******************************************************************************/
 
 
 /******************************************************************************/
 

-/* Slower version check, for use when platform intermixes malloc and mmap area
-addresses. */
+#ifndef TAINT_CHECK_FAST
+/* Test if a pointer refers to tainted memory.
+
+Slower version check, for use when platform intermixes malloc and mmap area
+addresses. Test against the current-block of all tainted pools first, then all
+blocks of all tainted pools.
+
+Return: TRUE iff tainted
+*/

 
 BOOL
 is_tainted_fn(const void * p)
 
 BOOL
 is_tainted_fn(const void * p)


@@ -168,24 +200,22 @@ is_tainted_fn(const void * p)
 storeblock * b;
 int pool;
 
 storeblock * b;
 int pool;
 

-for (pool = 0; pool < nelem(chainbase); pool++)
+for (pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)

   if ((b = current_block[pool]))
     {
     char * bc = CS b + ALIGNED_SIZEOF_STOREBLOCK;
   if ((b = current_block[pool]))
     {
     char * bc = CS b + ALIGNED_SIZEOF_STOREBLOCK;

-    if (CS p >= bc && CS p <= bc + b->length) goto hit;
+    if (CS p >= bc && CS p <= bc + b->length) return TRUE;

     }
 
     }
 

-for (pool = 0; pool < nelem(chainbase); pool++)
+for (pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)

   for (b = chainbase[pool]; b; b = b->next)
     {
     char * bc = CS b + ALIGNED_SIZEOF_STOREBLOCK;
   for (b = chainbase[pool]; b; b = b->next)
     {
     char * bc = CS b + ALIGNED_SIZEOF_STOREBLOCK;

-    if (CS p >= bc && CS p <= bc + b->length) goto hit;
+    if (CS p >= bc && CS p <= bc + b->length) return TRUE;

     }
 return FALSE;
     }
 return FALSE;

-
-hit:
-return pool >= POOL_TAINT_BASE;

 }
 }

+#endif

 
 
 void
 
 
 void


@@ -206,7 +236,8 @@ block, getting a new one if necessary. The address is saved in
 store_last_was_get.
 
 Arguments:
 store_last_was_get.
 
 Arguments:

-  size        amount wanted
+  size        amount wanted, bytes
+  tainted     class: set to true for untrusted data (eg. from smtp input)

   func        function from which called
   linenumber  line number in source file
 
   func        function from which called
   linenumber  line number in source file
 


@@ -246,15 +277,9 @@ if (size > yield_length[pool])
     /* Give up on this block, because it's too small */
     nblocks[pool]--;
     if (pool < POOL_TAINT_BASE)
     /* Give up on this block, because it's too small */
     nblocks[pool]--;
     if (pool < POOL_TAINT_BASE)

-      internal_store_free(newblock, func, linenumber);
+      internal_untainted_free(newblock, func, linenumber);

     else
     else

-      {
-#ifndef COMPILE_UTILITY
-      DEBUG(D_memory)
-       debug_printf("---Unmap %6p %-20s %4d\n", newblock, func, linenumber);
-#endif
-      munmap(newblock, newblock->length + ALIGNED_SIZEOF_STOREBLOCK);
-      }
+      internal_tainted_free(newblock, func, linenumber);

     newblock = NULL;
     }
 
     newblock = NULL;
     }
 


@@ -513,15 +538,9 @@ while ((b = bb))
   pool_malloc -= siz;
   nblocks[pool]--;
   if (pool < POOL_TAINT_BASE)
   pool_malloc -= siz;
   nblocks[pool]--;
   if (pool < POOL_TAINT_BASE)

-    internal_store_free(b, func, linenumber);
+    internal_untainted_free(b, func, linenumber);

   else
   else

-    {
-#ifndef COMPILE_UTILITY
-    DEBUG(D_memory)
-      debug_printf("---Unmap %6p %-20s %4d\n", b, func, linenumber);
-#endif
-    munmap(b, b->length + ALIGNED_SIZEOF_STOREBLOCK);
-    }
+    internal_tainted_free(b, func, linenumber);

   }
 
 /* Cut out the debugging stuff for utilities, but stop picky compilers from
   }
 
 /* Cut out the debugging stuff for utilities, but stop picky compilers from


@@ -797,7 +816,7 @@ if (!(yield = mmap(NULL, (size_t)size,
     "called from line %d of %s", size, line, func);
 
 if (yield < tainted_base) tainted_base = yield;
     "called from line %d of %s", size, line, func);
 
 if (yield < tainted_base) tainted_base = yield;

-if ((top = yield + size) > tainted_top) tainted_top = top;
+if ((top = US yield + size) > tainted_top) tainted_top = top;

 
 return store_alloc_tail(yield, size, func, line, US"Mmap");
 }
 
 return store_alloc_tail(yield, size, func, line, US"Mmap");
 }


@@ -856,7 +875,7 @@ Returns:      nothing
 */
 
 static void
 */
 
 static void

-internal_store_free(void *block, const char *func, int linenumber)
+internal_untainted_free(void * block, const char * func, int linenumber)

 {
 #ifdef COMPILE_UTILITY
 func = func;
 {
 #ifdef COMPILE_UTILITY
 func = func;


@@ -869,10 +888,24 @@ free(block);
 }
 
 void
 }
 
 void

-store_free_3(void *block, const char *func, int linenumber)
+store_free_3(void * block, const char * func, int linenumber)

 {
 n_nonpool_blocks--;
 {
 n_nonpool_blocks--;

-internal_store_free(block, func, linenumber);
+internal_untainted_free(block, func, linenumber);
+}
+
+/******************************************************************************/
+static void
+internal_tainted_free(storeblock * block, const char * func, int linenumber)
+{
+#ifdef COMPILE_UTILITY
+func = func;
+linenumber = linenumber;
+#else
+DEBUG(D_memory)
+  debug_printf("---Unmap %6p %-20s %4d\n", block, func, linenumber);
+#endif
+munmap((void *)block, block->length + ALIGNED_SIZEOF_STOREBLOCK);

 }
 
 /******************************************************************************/
 }
 
 /******************************************************************************/