[PATCH V2 29/32] selftests/sgx: Test invalid access to removed enclave page

Reinette Chatre
2022-02-08T01:07:03Z

Removing a page from an initialized enclave involves three steps:
(1) the user requests changing the page type to SGX_PAGE_TYPE_TRIM
via the SGX_IOC_ENCLAVE_MODIFY_TYPE ioctl(), (2) on success the
ENCLU[EACCEPT] instruction is run from within the enclave to accept
the page removal, (3) the user initiates the actual removal of the
page via the SGX_IOC_ENCLAVE_REMOVE_PAGES ioctl().

Test two possible invalid accesses during the page removal flow:
* Test the behavior when a request to remove the page by changing its
type to SGX_PAGE_TYPE_TRIM completes successfully but instead of
executing ENCLU[EACCEPT] from within the enclave the enclave attempts
to read from the page. Even though the page is accessible from the
page table entries its type is SGX_PAGE_TYPE_TRIM and thus not
accessible according to SGX. The expected behavior is a page fault
with the SGX flag set in the error code.
* Test the behavior when the page type is changed successfully and
ENCLU[EACCEPT] was run from within the enclave. The final ioctl(),
SGX_IOC_ENCLAVE_REMOVE_PAGES, is omitted and replaced with an
attempt to access the page. Even though the page is accessible
from the page table entries its type is SGX_PAGE_TYPE_TRIM and
thus not accessible according to SGX. The expected behavior is
a page fault with the SGX flag set in the error code.

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).
- Use ioctl() instead of ioctl (Dave).

tools/testing/selftests/sgx/main.c | 247 +++++++++++++++++++++++++++++
1 file changed, 247 insertions(+)

diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c
index e9513ced1853..239d3c9df169 100644
--- a/tools/testing/selftests/sgx/main.c
+++ b/tools/testing/selftests/sgx/main.c
@@ -1588,4 +1588,251 @@ TEST_F(enclave, remove_added_page_no_eaccept)
EXPECT_EQ(remove_ioc.count, 0);
}

+/*
+ * Request enclave page removal but instead of correctly following with
+ * EACCEPT a read attempt to page is made from within the enclave.
+ */
+TEST_F(enclave, remove_added_page_invalid_access)
+{
+ struct encl_op_get_from_addr get_addr_op;
+ struct encl_op_put_to_addr put_addr_op;
+ struct sgx_enclave_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(&ioc, 0, sizeof(ioc));
+ ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPE, &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(&ioc, 0, sizeof(ioc));
+ memset(&secinfo, 0, sizeof(secinfo));
+
+ secinfo.flags = SGX_PAGE_TYPE_TRIM << 8;
+ ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+ ioc.length = PAGE_SIZE;
+ ioc.secinfo = (unsigned long)&secinfo;
+
+ ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPE, &ioc);
+ errno_save = ret == -1 ? errno : 0;
+
+ EXPECT_EQ(ret, 0);
+ EXPECT_EQ(errno_save, 0);
+ EXPECT_EQ(ioc.result, 0);
+ EXPECT_EQ(ioc.count, 4096);
+
+ /*
+ * Read from page that was just removed.
+ */
+ get_addr_op.value = 0;
+
+ EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+ /*
+ * From kernel perspective the page is present but according to SGX the
+ * page should not be accessible so a #PF with SGX bit set is
+ * expected.
+ */
+
+ EXPECT_EQ(self->run.function, ERESUME);
+ EXPECT_EQ(self->run.exception_vector, 14);
+ EXPECT_EQ(self->run.exception_error_code, 0x8005);
+ EXPECT_EQ(self->run.exception_addr, data_start);
+}
+
+/*
+ * Request enclave page removal and correctly follow with
+ * EACCEPT but do not follow with removal ioctl() but instead a read attempt
+ * to removed page is made from within the enclave.
+ */
+TEST_F(enclave, remove_added_page_invalid_access_after_eaccept)
+{
+ struct encl_op_get_from_addr get_addr_op;
+ struct encl_op_put_to_addr put_addr_op;
+ struct encl_op_eaccept eaccept_op;
+ struct sgx_enclave_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(&ioc, 0, sizeof(ioc));
+ ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPE, &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(&ioc, 0, sizeof(ioc));
+ memset(&secinfo, 0, sizeof(secinfo));
+
+ secinfo.flags = SGX_PAGE_TYPE_TRIM << 8;
+ ioc.offset = encl_get_data_offset(&self->encl) + PAGE_SIZE;
+ ioc.length = PAGE_SIZE;
+ ioc.secinfo = (unsigned long)&secinfo;
+
+ ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPE, &ioc);
+ errno_save = ret == -1 ? errno : 0;
+
+ EXPECT_EQ(ret, 0);
+ EXPECT_EQ(errno_save, 0);
+ EXPECT_EQ(ioc.result, 0);
+ EXPECT_EQ(ioc.count, 4096);
+
+ eaccept_op.epc_addr = (unsigned long)data_start;
+ eaccept_op.ret = 0;
+ eaccept_op.flags = SGX_SECINFO_TRIM | SGX_SECINFO_MODIFIED;
+ eaccept_op.header.type = ENCL_OP_EACCEPT;
+
+ EXPECT_EQ(ENCL_CALL(&eaccept_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);
+ EXPECT_EQ(eaccept_op.ret, 0);
+
+ /* Skip ioctl() to remove page. */
+
+ /*
+ * Read from page that was just removed.
+ */
+ get_addr_op.value = 0;
+
+ EXPECT_EQ(ENCL_CALL(&get_addr_op, &self->run, true), 0);
+
+ /*
+ * From kernel perspective the page is present but according to SGX the
+ * page should not be accessible so a #PF with SGX bit set is
+ * expected.
+ */
+
+ EXPECT_EQ(self->run.function, ERESUME);
+ EXPECT_EQ(self->run.exception_vector, 14);
+ EXPECT_EQ(self->run.exception_error_code, 0x8005);
+ EXPECT_EQ(self->run.exception_addr, data_start);
+}
+
TEST_HARNESS_MAIN
--
2.25.1