libndr: moved the NDR_* flags to have less overlap

We have 3 different types of flags values in our NDR layer. We've
recently found bugs where these types of flags have been mixed up,
especially by people adding hand written ndr code for tricky
structures. We previously got away with this because (for example)
NDR_SCALARS and NDR_IN had the same value, so mixing up the two
concepts sometimes worked. Unfortunately it also led to bugs where we
didn't do what was expected, such as in our smbtorture ndr test suite,
where passing a ndr_flags value of zero led to only checking that two
empty structures were equal.

This changes the values of the NDR_IN|NDR_OUT and
NDR_SCALARS|NDR_BUFFERS values to be in different bit ranges, and adds
macros for checking the validity of passed in flags. A followup patch
modifies the ndr calls to use these macros, and pidl to generate
them. This should catch misuse of the APIs.

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>

1 files changed, 36 insertions, 8 deletions

diff --git a/librpc/ndr/libndr.h b/librpc/ndr/libndr.h
index 1f65ab4813..c8edfdac39 100644
--- a/librpc/ndr/libndr.h
+++ b/librpc/ndr/libndr.h
@@ -192,7 +192,8 @@ enum ndr_err_code {
 	NDR_ERR_IPV6ADDRESS,
 	NDR_ERR_INVALID_POINTER,
 	NDR_ERR_UNREAD_BYTES,
-	NDR_ERR_NDR64
+	NDR_ERR_NDR64,
+	NDR_ERR_FLAGS
 };
 
 #define NDR_ERR_CODE_IS_SUCCESS(x) (x == NDR_ERR_SUCCESS)
@@ -210,17 +211,44 @@ enum ndr_compression_alg {
 
 /*
   flags passed to control parse flow
+  These are deliberately in a different range to the NDR_IN/NDR_OUT
+  flags to catch mixups
 */
-#define NDR_SCALARS 1
-#define NDR_BUFFERS 2
+#define NDR_SCALARS    0x100
+#define NDR_BUFFERS    0x200
 
 /*
-  flags passed to ndr_print_*()
+  flags passed to ndr_print_*() and ndr pull/push for functions
+  These are deliberately in a different range to the NDR_SCALARS/NDR_BUFFERS
+  flags to catch mixups
 */
-#define NDR_IN 1
-#define NDR_OUT 2
-#define NDR_BOTH 3
-#define NDR_SET_VALUES 4
+#define NDR_IN         0x10
+#define NDR_OUT        0x20
+#define NDR_BOTH       0x30
+#define NDR_SET_VALUES 0x40
+
+
+#define NDR_PULL_CHECK_FLAGS(ndr, ndr_flags) do { \
+	if ((ndr_flags) & ~(NDR_SCALARS|NDR_BUFFERS)) { \
+		return ndr_pull_error(ndr, NDR_ERR_FLAGS, "Invalid pull struct ndr_flags 0x%x", ndr_flags); \
+	} \
+} while (0)
+
+#define NDR_PUSH_CHECK_FLAGS(ndr, ndr_flags) do { \
+	if ((ndr_flags) & ~(NDR_SCALARS|NDR_BUFFERS)) \
+		return ndr_push_error(ndr, NDR_ERR_FLAGS, "Invalid push struct ndr_flags 0x%x", ndr_flags); \
+} while (0)
+
+#define NDR_PULL_CHECK_FN_FLAGS(ndr, flags) do { \
+	if ((flags) & ~(NDR_BOTH|NDR_SET_VALUES)) { \
+		return ndr_pull_error(ndr, NDR_ERR_FLAGS, "Invalid fn pull flags 0x%x", flags); \
+	} \
+} while (0)
+
+#define NDR_PUSH_CHECK_FN_FLAGS(ndr, flags) do { \
+	if ((flags) & ~(NDR_BOTH|NDR_SET_VALUES)) \
+		return ndr_push_error(ndr, NDR_ERR_FLAGS, "Invalid fn push flags 0x%x", flags); \
+} while (0)
 
 #define NDR_PULL_NEED_BYTES(ndr, n) do { \
 	if (unlikely((n) > ndr->data_size || ndr->offset + (n) > ndr->data_size)) { \