[PATCH V2 28/32] selftests/sgx: Test faulty enclave behavior

Reinette Chatre
2022-02-08T01:07:14Z

Removing a page from an initialized enclave involves three steps:
first the user requests changing the page type to SGX_PAGE_TYPE_TRIM
via an ioctl(), on success the ENCLU[EACCEPT] instruction needs to be
run from within the enclave to accept the page removal, finally the
user requests page removal to be completed via an ioctl(). Only after
acceptance (ENCLU[EACCEPT]) from within the enclave can the kernel
remove the page from a running enclave.

Test the behavior when the user's request to change the page type
succeeds, but the ENCLU[EACCEPT] instruction is not run before the
ioctl() requesting page removal is run. This should not be permitted.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
Changes since V1:
- Update to support ioctl() name change (SGX_IOC_PAGE_MODT ->
SGX_IOC_ENCLAVE_MODIFY_TYPE) and provide secinfo as parameter instead
of just page type (Jarkko).
- Update test to reflect page removal ioctl() and struct name change:
SGX_IOC_PAGE_REMOVE->SGX_IOC_ENCLAVE_REMOVE_PAGES,
struct sgx_page_remove -> struct sgx_enclave_remove_pages (Jarkko).
- Use ioctl() instead of ioctl in text (Dave).

tools/testing/selftests/sgx/main.c | 116 +++++++++++++++++++++++++++++
1 file changed, 116 insertions(+)

diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c
index 53a581bd56c5..e9513ced1853 100644
--- a/tools/testing/selftests/sgx/main.c
+++ b/tools/testing/selftests/sgx/main.c
@@ -1472,4 +1472,120 @@ TEST_F(enclave, tcs_create)
munmap(addr, 3 * PAGE_SIZE);
}

+/*
+ * Ensure sane behavior if user requests page removal, does not run
+ * EACCEPT from within enclave but still attempts to finalize page removal
+ * with the SGX_IOC_ENCLAVE_REMOVE_PAGES ioctl(). The latter should fail
+ * because the removal was not EACCEPTed from within the enclave.
+ */
+TEST_F(enclave, remove_added_page_no_eaccept)
+{
+ struct sgx_enclave_remove_pages remove_ioc;
+ struct encl_op_get_from_addr get_addr_op;
+ struct encl_op_put_to_addr put_addr_op;
+ struct sgx_enclave_modt modt_ioc;
+ struct sgx_secinfo secinfo;
+ unsigned long data_start;
+ int ret, errno_save;
+
+ ASSERT_TRUE(setup_test_encl(ENCL_HEAP_SIZE_DEFAULT, &self->encl, _metadata));
+
+ memset(&self->run, 0, sizeof(self->run));
+ self->run.tcs = self->encl.encl_base;
+
+ /*
+ * Hardware (SGX2) and kernel support is needed for this test. Start
+ * with check that test has a chance of succeeding.
+ */
+ memset(&modt_ioc, 0, sizeof(modt_ioc));
+ ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPE, &modt_ioc);
+
+ if (ret == -1) {
+ if (errno == ENOTTY)
+ SKIP(return, "Kernel does not support SGX_IOC_ENCLAVE_MODIFY_TYPE ioctl()");
+ else if (errno == ENODEV)
+ SKIP(return, "System does not support SGX2");
+ }
+
+ /*
+ * Invalid parameters were provided during sanity check,
+ * expect command to fail.
+ */
+ EXPECT_EQ(ret, -1);
+
+ /*
+ * Page that will be removed is the second data page in the .data
+ * segment. This forms part of the local encl_buffer within the
+ * enclave.
+ */
+ data_start = self->encl.encl_base +
+ encl_get_data_offset(&self->encl) + PAGE_SIZE;
+
+ /*
+ * Sanity check that page at @data_start is writable before
+ * removing it.
+ *
+ * Start by writing MAGIC to test page.
+ */
+ put_addr_op.value = MAGIC;
+ put_addr_op.addr = data_start;
+ put_addr_op.header.type = ENCL_OP_PUT_TO_ADDRESS;
+
+ EXPECT_EQ(ENCL_CALL(&put_addr_op, &self->run, true), 0);
+
+ EXPECT_EEXIT(&self->run);
+ EXPECT_EQ(self->run.exception_vector, 0);
+ EXPECT_EQ(self->run.exception_error_code, 0);
+ EXPECT_EQ(self->run.exception_addr, 0);
+
+ /*
+ * Read memory that was just written to, confirming that data
+ * previously written (MAGIC) is present.
+ */
+ get_addr_op.value = 0;
+ get_addr_op.addr = data_start;
+ get_addr_op.header.type = ENCL_OP_GET_FROM_ADDRESS;
+
+ EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+ EXPECT_EQ(get_addr_op.value, MAGIC);
+ EXPECT_EEXIT(&self->run);
+ EXPECT_EQ(self->run.exception_vector, 0);
+ EXPECT_EQ(self->run.exception_error_code, 0);
+ EXPECT_EQ(self->run.exception_addr, 0);
+
+ /* Start page removal by requesting change of page type to PT_TRIM */
+ memset(&modt_ioc, 0, sizeof(modt_ioc));
+ memset(&secinfo, 0, sizeof(secinfo));
+
+ secinfo.flags = SGX_PAGE_TYPE_TRIM << 8;
+ modt_ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+ modt_ioc.length = PAGE_SIZE;
+ modt_ioc.secinfo = (unsigned long)&secinfo;
+
+ ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPE, &modt_ioc);
+ errno_save = ret == -1 ? errno : 0;
+
+ EXPECT_EQ(ret, 0);
+ EXPECT_EQ(errno_save, 0);
+ EXPECT_EQ(modt_ioc.result, 0);
+ EXPECT_EQ(modt_ioc.count, 4096);
+
+ /* Skip EACCEPT */
+
+ /* Send final ioctl() to complete page removal */
+ memset(&remove_ioc, 0, sizeof(remove_ioc));
+
+ remove_ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+ remove_ioc.length = PAGE_SIZE;
+
+ ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_REMOVE_PAGES, &remove_ioc);
+ errno_save = ret == -1 ? errno : 0;
+
+ /* Operation not permitted since EACCEPT was omitted. */
+ EXPECT_EQ(ret, -1);
+ EXPECT_EQ(errno_save, EPERM);
+ EXPECT_EQ(remove_ioc.count, 0);
+}
+
TEST_HARNESS_MAIN
--
2.25.1