*************************************************/
/* Copyright (c) University of Cambridge 1995 - 2018 */
-/* Copyright (c) The Exim maintainers 2019 */
+/* Copyright (c) The Exim maintainers 2019 - 2020 */
/* See the file NOTICE for conditions of use and distribution. */
/* Exim gets and frees all its store through these functions. In the original
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.
+
+ 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.
+
+ 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. 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).
*/
static void *next_yield[NPOOLS];
static int yield_length[NPOOLS] = { -1, -1, -1, -1, -1, -1 };
-/* The limits of the tainted pools. Tracking these on new allocations enables
-a fast is_tainted implementation. We assume the kernel only allocates mmaps using
-one side or the other of data+heap, not both. */
-
-void * tainted_base = (void *)-1;
-void * tainted_top = (void *)0;
-
/* pool_malloc holds the amount of memory used by the store pools; this goes up
and down as store is reset or released. nonpool_malloc is the total got by
malloc from other calls; this doesn't go down because it is just freed by
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",
[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 internal_store_free(void *, const char *, int linenumber);
/******************************************************************************/
+/* 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)
+{
+storeblock * b;
+
+for (int pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)
+ if ((b = current_block[pool]))
+ {
+ uschar * bc = US b + ALIGNED_SIZEOF_STOREBLOCK;
+ if (US p >= bc && US p < bc + b->length) return TRUE;
+ }
+
+for (int pool = POOL_TAINT_BASE; pool < nelem(chainbase); pool++)
+ for (b = chainbase[pool]; b; b = b->next)
+ {
+ uschar * bc = US b + ALIGNED_SIZEOF_STOREBLOCK;
+ if (US p >= bc && US p < bc + b->length) return TRUE;
+ }
+return FALSE;
+}
+
+
void
die_tainted(const uschar * msg, const uschar * func, int line)
{
}
+
/*************************************************
* Get a block from the current pool *
*************************************************/
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
{
int pool = tainted ? store_pool + POOL_TAINT_BASE : store_pool;
+/* Ensure we've been asked to allocate memory.
+A negative size is a sign of a security problem.
+A zero size might be also suspect, but our internal usage deliberately
+does this to return a current watermark value for a later release of
+allocated store. */
+
+if (size < 0 || size >= INT_MAX/2)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+ "bad memory allocation requested (%d bytes) at %s %d",
+ size, func, linenumber);
+
/* Round up the size to a multiple of the alignment. Although this looks a
messy statement, because "alignment" is a constant expression, the compiler can
do a reasonable job of optimizing, especially if the value of "alignment" is a
{
/* Give up on this block, because it's too small */
nblocks[pool]--;
- if (pool < POOL_TAINT_BASE)
- internal_store_free(newblock, func, linenumber);
- 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_store_free(newblock, func, linenumber);
newblock = NULL;
}
if (++nblocks[pool] > maxblocks[pool])
maxblocks[pool] = nblocks[pool];
- newblock = tainted
- ? store_mmap(mlength, func, linenumber)
- : internal_store_malloc(mlength, func, linenumber);
+ newblock = internal_store_malloc(mlength, func, linenumber);
newblock->next = NULL;
newblock->length = length;
int inc = newsize - oldsize;
int rounded_oldsize = oldsize;
+if (oldsize < 0 || newsize < oldsize || newsize >= INT_MAX/2)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+ "bad memory extension requested (%d -> %d bytes) at %s %d",
+ oldsize, newsize, func, linenumber);
+
/* Check that the block being extended was already of the required taint status;
refuse to extend if not. */
nbytes[pool] -= siz;
pool_malloc -= siz;
nblocks[pool]--;
- if (pool < POOL_TAINT_BASE)
- internal_store_free(b, func, linenumber);
- 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_store_free(b, func, linenumber);
}
/* Cut out the debugging stuff for utilities, but stop picky compilers from
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
+if (len < 0 || len > newsize)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+ "bad memory extension requested (%d -> %d bytes) at %s %d",
+ len, newsize, func, linenumber);
+
newtext = store_get(newsize, tainted);
memcpy(newtext, block, len);
if (release_ok) store_release_3(block, pool, func, linenumber);
-/******************************************************************************/
-static void *
-store_alloc_tail(void * yield, int size, const char * func, int line,
- const uschar * type)
-{
-if ((nonpool_malloc += size) > max_nonpool_malloc)
- max_nonpool_malloc = nonpool_malloc;
-
-/* Cut out the debugging stuff for utilities, but stop picky compilers from
-giving warnings. */
-
-#ifdef COMPILE_UTILITY
-func = func; line = line; type = type;
-#else
-
-/* If running in test harness, spend time making sure all the new store
-is not filled with zeros so as to catch problems. */
-
-if (f.running_in_test_harness)
- memset(yield, 0xF0, (size_t)size);
-DEBUG(D_memory) debug_printf("--%6s %6p %5d bytes\t%-14s %4d\tpool %5d nonpool %5d\n",
- type, yield, size, func, line, pool_malloc, nonpool_malloc);
-#endif /* COMPILE_UTILITY */
-
-return yield;
-}
-
-/*************************************************
-* Mmap store *
-*************************************************/
-
-static void *
-store_mmap(int size, const char * func, int line)
-{
-void * yield, * top;
-
-if (size < 16) size = 16;
-
-if (!(yield = mmap(NULL, (size_t)size,
- PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)))
- log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to mmap %d bytes of memory: "
- "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;
-
-return store_alloc_tail(yield, size, func, line, US"Mmap");
-}
-
/*************************************************
* Malloc store *
*************************************************/
Arguments:
size amount of store wanted
func function from which called
- linenumber line number in source file
+ line line number in source file
Returns: pointer to gotten store (panic on failure)
*/
static void *
-internal_store_malloc(int size, const char *func, int linenumber)
+internal_store_malloc(int size, const char *func, int line)
{
void * yield;
+if (size < 0 || size >= INT_MAX/2)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+ "bad memory allocation requested (%d bytes) at %s %d",
+ size, func, line);
+
if (size < 16) size = 16;
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);
+ "called from line %d in %s", size, line, func);
+
+if ((nonpool_malloc += size) > max_nonpool_malloc)
+ max_nonpool_malloc = nonpool_malloc;
+
+/* Cut out the debugging stuff for utilities, but stop picky compilers from
+giving warnings. */
-return store_alloc_tail(yield, size, func, linenumber, US"Malloc");
+#ifdef COMPILE_UTILITY
+func = func; line = line;
+#else
+
+/* If running in test harness, spend time making sure all the new store
+is not filled with zeros so as to catch problems. */
+
+if (f.running_in_test_harness)
+ memset(yield, 0xF0, (size_t)size);
+DEBUG(D_memory) debug_printf("--Malloc %6p %5d bytes\t%-14s %4d\tpool %5d nonpool %5d\n",
+ yield, size, func, line, pool_malloc, nonpool_malloc);
+#endif /* COMPILE_UTILITY */
+
+return yield;
}
void *
*/
static void
-internal_store_free(void *block, const char *func, int linenumber)
+internal_store_free(void * block, const char * func, int linenumber)
{
#ifdef COMPILE_UTILITY
func = func;
}
void
-store_free_3(void *block, const char *func, int linenumber)
+store_free_3(void * block, const char * func, int linenumber)
{
n_nonpool_blocks--;
internal_store_free(block, func, linenumber);