Fix taint hybrid-checking on BSD

[exim.git] / src / src / store.c

diff --git a/src/src/store.c b/src/src/store.c
index b65649f4aad1db3c55d976b5f55c09e295554b9d..1fe97e6c9897f0ef7116561da1d483cb3e39fa2f 100644 (file)
--- a/src/src/store.c
+++ b/src/src/store.c
@@ -62,9 +62,11 @@ The following different types of store are recognized:
   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).
+  content is used.  Intermediate-layer functions (eg. Ustrncpy) that modify
+  existing allocations fail if tainted data is written into an untainted area.
+  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).
 */
 
 
@@ -184,7 +186,6 @@ static void   internal_tainted_free(storeblock *, const char *, int linenumber);
 
 /******************************************************************************/
 
-#ifndef TAINT_CHECK_FAST
 /* Test if a pointer refers to tainted memory.
 
 Slower version check, for use when platform intermixes malloc and mmap area
@@ -198,24 +199,22 @@ BOOL
 is_tainted_fn(const void * p)
 {
 storeblock * b;
-int pool;
 
-for (pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)
+for (int pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)
   if ((b = current_block[pool]))
     {
-    char * bc = CS b + ALIGNED_SIZEOF_STOREBLOCK;
-    if (CS p >= bc && CS p <= bc + b->length) return TRUE;
+    uschar * bc = US b + ALIGNED_SIZEOF_STOREBLOCK;
+    if (US p >= bc && US p <= bc + b->length) return TRUE;
     }
 
-for (pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)
+for (int pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)
   for (b = chainbase[pool]; b; b = b->next)
     {
-    char * bc = CS b + ALIGNED_SIZEOF_STOREBLOCK;
-    if (CS p >= bc && CS p <= bc + b->length) return TRUE;
+    uschar * bc = US b + ALIGNED_SIZEOF_STOREBLOCK;
+    if (US p >= bc && US p <= bc + b->length) return TRUE;
     }
 return FALSE;
 }
-#endif
 
 
 void
@@ -225,6 +224,31 @@ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "Taint mismatch, %s: %s %d\n",
        msg, func, line);
 }
 
+static void
+use_slow_taint_check(void)
+{
+#ifndef COMPILE_UTILITY
+DEBUG(D_any) debug_printf("switching to slow-mode taint checking\n");
+#endif
+f.taint_check_slow = TRUE;
+}
+
+static void
+verify_all_untainted(void)
+{
+for (int pool = 0; pool < POOL_TAINT_BASE; pool++)
+  for (storeblock * b = chainbase[pool]; b; b = b->next)
+    {
+    uschar * bc = US b + ALIGNED_SIZEOF_STOREBLOCK;
+    if (is_tainted(bc))
+      {
+      use_slow_taint_check();
+      return;
+      }
+    }
+}
+
+
 
 /*************************************************
 *       Get a block from the current pool        *
@@ -758,7 +782,7 @@ int pool = tainted ? store_pool + POOL_TAINT_BASE : store_pool;
 BOOL release_ok = !tainted && store_last_get[pool] == block;
 uschar * newtext;
 
-#ifndef MACRO_PREDEF
+#if !defined(MACRO_PREDEF) && !defined(COMPILE_UTILITY)
 if (is_tainted(block) != tainted)
   die_tainted(US"store_newblock", CUS func, linenumber);
 #endif
@@ -817,6 +841,7 @@ if (!(yield = mmap(NULL, (size_t)size,
 
 if (yield < tainted_base) tainted_base = yield;
 if ((top = US yield + size) > tainted_top) tainted_top = top;
+if (!f.taint_check_slow) use_slow_taint_check();
 
 return store_alloc_tail(yield, size, func, line, US"Mmap");
 }
@@ -848,6 +873,14 @@ if (!(yield = malloc((size_t)size)))
   log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to malloc %d bytes of memory: "
     "called from line %d in %s", size, linenumber, func);
 
+/* If malloc ever returns apparently tainted memory, which glibc
+malloc will as it uses mmap for larger requests, we must switch to
+the slower checking for tainting (checking an address against all
+the tainted pool block spans, rather than just the mmap span) */
+
+if (!f.taint_check_slow && is_tainted(yield))
+  use_slow_taint_check();
+
 return store_alloc_tail(yield, size, func, linenumber, US"Malloc");
 }