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[Pal/Linux-SGX] Lazily zero-out the heap instead of proactively on init

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Previously, Linux-SGX PAL initialized the whole heap to zero from
within the enclave at startup. This led to significant slowdown on
large-sized enclaves. This commit removes the old proactive logic
and instead zeroes-out the heap lazily, when enclave pages are
actually requested. This does not change the security guarantees
because the whole heap is anyway RWX on SGX v1, and the attacker
may exploit app vulnerabilities (if any) by supplying malicious data
within the enclave during runtime.
This commit is contained in:
Dmitrii Kuvaiskii
2020-07-07 16:01:12 -07:00
parent e7f5600a5d
commit 647bca34a5
2 changed files with 3 additions and 17 deletions
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Pal/src/host/Linux-SGX/db_main.c
-17
View File
@@ -207,23 +207,6 @@ void pal_linux_main(char* uptr_args, uint64_t args_size, char* uptr_env, uint64_
g_pal_sec.exec_addr = GET_ENCLAVE_TLS(exec_addr);
g_pal_sec.exec_size = GET_ENCLAVE_TLS(exec_size);
/* Zero the heap. We need to take care to not zero the exec area. */
void* zero1_start = g_pal_sec.heap_min;
void* zero1_end = g_pal_sec.heap_max;
void* zero2_start = g_pal_sec.heap_max;
void* zero2_end = g_pal_sec.heap_max;
if (g_pal_sec.exec_addr != NULL) {
zero1_end = MIN(zero1_end, SATURATED_P_SUB(g_pal_sec.exec_addr, MEMORY_GAP, 0));
zero2_start = SATURATED_P_ADD(g_pal_sec.exec_addr + g_pal_sec.exec_size, MEMORY_GAP,
zero2_end);
}
memset(zero1_start, 0, zero1_end - zero1_start);
memset(zero2_start, 0, zero2_end - zero2_start);
/* relocate PAL itself */
g_pal_map.l_addr = elf_machine_load_address();
g_pal_map.l_name = ENCLAVE_PAL_FILENAME;
Pal/src/host/Linux-SGX/enclave_pages.c
+3
View File
@@ -163,6 +163,9 @@ static void* __create_vma_and_merge(void* addr, size_t size, bool is_pal_interna
vma->top = addr + size;
vma->is_pal_internal = is_pal_internal;
/* initialize the contents of the new VMA to zero */
memset(vma->bottom, 0, vma->top - vma->bottom);
/* how much memory was freed because [addr, addr + size) overlapped with VMAs */
size_t freed = 0;