gluten: check limits

Add bounds checking:
  - if offset is larger then the maximum per offset type
  - if memcpy is reading/writing inside gluten

5 files changed, 183 insertions, 11 deletions

diff --git a/common/gluten.h b/common/gluten.h
index b1723ca..d1d3c61 100644
--- a/common/gluten.h
+++ b/common/gluten.h
@@ -26,7 +26,30 @@ extern struct seccomp_data anonymous_seccomp_data;
 	MAX(MAX(MAX(DATA_SIZE, RO_DATA_SIZE), INST_MAX), \
 	    ARRAY_SIZE(anonymous_seccomp_data.args))
 
-#define seccomp_offset_args(x) (sizeof(uint64_t) / sizeof(uint16_t)) * (x)
+#define check_gluten_limits(g, v, size)                                   \
+	do {                                                              \
+		struct gluten_offset off = { v.type, v.offset + (size) }; \
+		if (!is_offset_valid(off))                                \
+			die(" invalid offset: %d", off.offset);           \
+	} while (0)
+
+#define gluten_write(g, dst, src)                               \
+	do {                                                    \
+		void *p = gluten_write_ptr((g), (dst));         \
+		check_gluten_limits((g), (dst), sizeof((src))); \
+		if (p == NULL)                                  \
+			die(" invalid type of offset");         \
+		memcpy(p, &(src), sizeof(src));                 \
+	} while (0)
+
+#define gluten_read(s, g, dst, src, size)                    \
+	do {                                                 \
+		const void *p = gluten_ptr((s), (g), (src)); \
+		check_gluten_limits((g), (src), (size));     \
+		if (p == NULL)                               \
+			die(" invalid type of offset");      \
+		memcpy(&(dst), p, (size));      \
+	} while (0)
 
 enum gluten_offset_type {
 	OFFSET_RO_DATA = 0,
@@ -195,6 +218,22 @@ struct gluten {
 
 BUILD_BUG_ON(INST_SIZE < INST_MAX * sizeof(struct op))
 
+static inline bool is_offset_valid(const struct gluten_offset x)
+{
+	switch (x.type) {
+	case OFFSET_DATA:
+		return x.offset < DATA_SIZE;
+	case OFFSET_RO_DATA:
+		return x.offset < RO_DATA_SIZE;
+	case OFFSET_INSTRUCTION:
+		return x.offset < INST_SIZE;
+	case OFFSET_SECCOMP_DATA:
+		return x.offset < 6;
+	default:
+		return false;
+	}
+}
+
 #ifdef COOKER
 static inline void *gluten_ptr(struct gluten *g, const struct gluten_offset x)
 #else
@@ -202,7 +241,8 @@ static inline void *gluten_write_ptr(struct gluten *g,
 				     const struct gluten_offset x)
 #endif
 {
-	/* TODO: Boundary checks */
+	if (!is_offset_valid(x))
+		die(" invalid offset: %d", x.offset);
 
 	switch (x.type) {
 	case OFFSET_DATA:
@@ -223,6 +263,9 @@ static inline const void *gluten_ptr(const struct seccomp_data *s,
 				     struct gluten *g,
 				     const struct gluten_offset x)
 {
+	if (!is_offset_valid(x))
+		die(" invalid offset: %d", x.offset);
+
 	switch (x.type) {
 	case OFFSET_DATA:
 		return g->data + x.offset;
@@ -237,5 +280,4 @@ static inline const void *gluten_ptr(const struct seccomp_data *s,
 	}
 }
 #endif
-
 #endif /* COMMON_GLUTEN_H */
diff --git a/operations.c b/operations.c
index 870ecf1..bf03ab8 100644
--- a/operations.c
+++ b/operations.c
@@ -177,6 +177,7 @@ int op_load(const struct seccomp_notif *req, int notifier, struct gluten *g,
 		ret = -1;
 		goto out;
 	}
+	check_gluten_limits(&g, load->dst, load->size);
 	if (pread(fd, gluten_write_ptr(g, load->dst), load->size, *src) < 0) {
 		perror("pread");
 		return -1;
@@ -232,7 +233,7 @@ int op_call(const struct seccomp_notif *req, int notifier, struct gluten *g,
 	 * reference
 	 */
 	if (op->has_ret)
-		memcpy(gluten_write_ptr(g, op->ret), &c.ret, sizeof(c.ret));
+		gluten_write(g, op->ret, c.ret);
 
 	return 0;
 }
@@ -263,7 +264,7 @@ int op_return(const struct seccomp_notif *req, int notifier, struct gluten *g,
 	resp.flags = 0;
 	resp.error = 0;
 
-	memcpy(&resp.val, gluten_ptr(NULL, g, op->val), sizeof(resp.val));
+	gluten_read(NULL, g, resp.val, op->val, sizeof(resp.val));
 
 	if (send_target(&resp, notifier) == -1)
 		return -1;
@@ -299,10 +300,8 @@ static int do_inject(const struct seccomp_notif *req, int notifier,
 	resp.newfd_flags = 0;
 	resp.id = req->id;
 
-	memcpy(&resp.newfd, gluten_ptr(NULL, g, op->new_fd),
-	       sizeof(resp.newfd));
-	memcpy(&resp.srcfd, gluten_ptr(NULL, g, op->new_fd),
-	       sizeof(resp.srcfd));
+	gluten_read(NULL, g, resp.newfd, op->new_fd, sizeof(resp.newfd));
+	gluten_read(NULL, g, resp.srcfd, op->old_fd, sizeof(resp.srcfd));
 
 	if (atomic)
 		resp.flags |= SECCOMP_ADDFD_FLAG_SEND;
@@ -351,8 +350,9 @@ int op_resolve_fd(const struct seccomp_notif *req, int notifier,
 
 	(void)notifier;
 
-	memcpy(&path, gluten_ptr(NULL, g, op->path), op->path_size);
-	memcpy(&fd, gluten_ptr(NULL, g, op->fd), sizeof(fd));
+
+	gluten_read(NULL, g, path, op->path, sizeof(op->path_size));
+	gluten_read(NULL, g, fd, op->fd, sizeof(fd));
 
 	snprintf(fdpath, PATH_MAX, "/proc/%d/fd/%d", req->pid, fd);
 	if ((nbytes = readlink(fdpath, buf, op->path_size)) < 0) {
diff --git a/tests/unit/Makefile b/tests/unit/Makefile
index 202e198..966ae7d 100644
--- a/tests/unit/Makefile
+++ b/tests/unit/Makefile
@@ -23,6 +23,10 @@ HEADERS_OP := $(COMMON_DIR)/gluten.h  $(OP_DIR)/operations.h \
 		   $(COMMON_DIR)/common.h testutil.h $(COMMON_DIR)/util.h
 SRCS_OP := $(COMMON_DIR)/common.c $(OP_DIR)/operations.c util.c $(COMMON_DIR)/util.c
 
+HEADERS_ERROR := $(COMMON_DIR)/gluten.h  $(OP_DIR)/operations.h \
+		   $(COMMON_DIR)/common.h testutil.h $(COMMON_DIR)/util.h
+SRCS_ERROR := $(COMMON_DIR)/common.c $(OP_DIR)/operations.c util.c $(COMMON_DIR)/util.c
+
 TARGET := $(shell $(CC) -dumpmachine)
 TARGET_ARCH := $(shell echo $(TARGET) | cut -f1 -d- | tr [A-Z] [a-z])
 TARGET_ARCH := $(shell echo $(TARGET_ARCH) | sed 's/powerpc/ppc/')
@@ -67,5 +71,11 @@ build-operations: test_operations.c $(SRCS_OP) $(HEADERS_OP)
 test-operations: build-operations
 	./operations
 
+build-error-checks: test_errors.c $(SRCS_ERROR) $(HEADERS_ERROR)
+	$(CC) $(CFLAGS) -o error_checks $(SRCS_ERROR) \
+		test_errors.c
+
+test-error-checks: build-error-checks
+	./error_checks
 clean:
 	rm -f operations  op-call filter filter-build
diff --git a/tests/unit/test_errors.c b/tests/unit/test_errors.c
new file mode 100644
index 0000000..d00d42e
--- /dev/null
+++ b/tests/unit/test_errors.c
@@ -0,0 +1,118 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+
+#include <check.h>
+
+#include "operations.h"
+#include "common/common.h"
+#include "common/gluten.h"
+#include "testutil.h"
+
+static void setup_error_check()
+{
+	at = mmap(NULL, sizeof(struct args_target), PROT_READ | PROT_WRITE,
+		  MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+	at->check_fd = false;
+	at->nr = __NR_getpid;
+	at->install_filter = install_notification_filter;
+	setup();
+}
+
+struct gluten_offset test_max_size_data[] = {
+	{ OFFSET_DATA, DATA_SIZE },
+	{ OFFSET_RO_DATA, RO_DATA_SIZE },
+	{ OFFSET_SECCOMP_DATA, 6 },
+	{ OFFSET_INSTRUCTION, INST_SIZE },
+};
+
+START_TEST(test_bound_check)
+{
+	struct op ops[] = {
+		{ OP_RETURN, { { 0 } } },
+	};
+	ops[0].op.ret.val.offset = test_max_size_data[_i].offset;
+	ops[0].op.ret.val.type = test_max_size_data[_i].type;
+
+	eval(&gluten, ops, &req, notifyfd);
+}
+
+START_TEST(test_write_op_return)
+{
+	struct op ops[] = {
+		{ OP_CALL,
+		  { .call = { .nr = __NR_getpid,
+			      .has_ret = true,
+			      .ret = { OFFSET_DATA, DATA_SIZE - 1 } } } },
+	};
+
+	eval(&gluten, ops, &req, notifyfd);
+}
+
+START_TEST(test_write_op_load)
+{
+	char a[30];
+	struct op ops[] = {
+		{ OP_LOAD,
+		  { .load = { { OFFSET_SECCOMP_DATA, 1 },
+			      { OFFSET_DATA, DATA_SIZE - 1 },
+			      sizeof(a) } } },
+	};
+
+	eval(&gluten, ops, &req, notifyfd);
+}
+
+START_TEST(test_read_op_return)
+{
+	struct op ops[] = {
+		{ OP_RETURN, { { 0 } } },
+	};
+	ops[0].op.ret.val.offset = test_max_size_data[_i].offset - 1;
+	ops[0].op.ret.val.type = test_max_size_data[_i].type;
+
+	eval(&gluten, ops, &req, notifyfd);
+}
+
+Suite *error_suite(void)
+{
+	Suite *s;
+	TCase *bounds, *gwrite, *gread;
+
+	s = suite_create("Error handling");
+
+	bounds = tcase_create("bound checks");
+	tcase_add_loop_exit_test(bounds, test_bound_check, EXIT_FAILURE, 0,
+				 sizeof(test_max_size_data) /
+					 sizeof(test_max_size_data[0]));
+	suite_add_tcase(s, bounds);
+
+	gwrite = tcase_create("write gluten");
+	tcase_add_checked_fixture(gwrite, setup_error_check, teardown);
+	tcase_add_exit_test(gwrite, test_write_op_return, EXIT_FAILURE);
+	tcase_add_exit_test(gwrite, test_write_op_load, EXIT_FAILURE);
+	suite_add_tcase(s, gwrite);
+
+	gread = tcase_create("read gluten");
+	tcase_add_loop_exit_test(gread, test_read_op_return, EXIT_FAILURE, 0,
+				 sizeof(test_max_size_data) /
+					 sizeof(test_max_size_data[0]));
+	suite_add_tcase(s, gread);
+
+	return s;
+}
+
+int main(void)
+{
+	int no_failed = 0;
+	Suite *s;
+	SRunner *runner;
+
+	s = error_suite();
+	runner = srunner_create(s);
+
+	srunner_run_all(runner, CK_VERBOSE);
+	no_failed = srunner_ntests_failed(runner);
+	srunner_free(runner);
+	return (no_failed == 0) ? EXIT_SUCCESS : EXIT_FAILURE;
+}
diff --git a/tests/unit/testutil.h b/tests/unit/testutil.h
index 45fe08f..ec881c7 100644
--- a/tests/unit/testutil.h
+++ b/tests/unit/testutil.h
@@ -20,6 +20,8 @@
 static inline void *test_gluten_write_ptr(struct gluten *g,
 					  const struct gluten_offset x)
 {
+	ck_assert_msg(is_offset_valid(x), "offset out of bounds");
+
 	switch (x.type) {
 	case OFFSET_DATA:
 		return (char *)g->data + x.offset;