r2180: added RPC flags "padcheck" which enables checking of all received pad

bytes to make sure they are zero. Non-zero values usually indicate one
of two things:

 - the server is leaking data through sending uninitialised memory
 - we have mistaken a real field in the IDL for padding

to differentiate between the two you really need to run with
"print,padcheck" and look carefully at whether the non-zero pad bytes
are random or appear to be deliberate.
(This used to be commit 7fdb778f81f14aaab75ab204431e4342a462957a)

5 files changed, 70 insertions, 16 deletions

diff --git a/source4/librpc/ndr/libndr.h b/source4/librpc/ndr/libndr.h
index cea7290577..9940dc2c05 100644
--- a/source4/librpc/ndr/libndr.h
+++ b/source4/librpc/ndr/libndr.h
@@ -42,7 +42,7 @@ struct ndr_token_list {
 */
 struct ndr_pull {
 	uint32_t flags; /* LIBNDR_FLAG_* */
-	char *data;
+	uint8_t *data;
 	uint32_t data_size;
 	uint32_t offset;
 
@@ -62,7 +62,7 @@ struct ndr_pull_save {
 /* structure passed to functions that generate NDR formatted data */
 struct ndr_push {
 	uint32_t flags; /* LIBNDR_FLAG_* */
-	char *data;
+	uint8_t *data;
 	uint32_t alloc_size;
 	uint32_t offset;
 
@@ -112,6 +112,9 @@ struct ndr_print {
 /* used to force a section of IDL to be little-endian */
 #define LIBNDR_FLAG_LITTLE_ENDIAN (1<<17)
 
+/* used to check if alignment padding is zero */
+#define LIBNDR_FLAG_PAD_CHECK     (1<<18)
+
 
 /* useful macro for debugging */
 #define NDR_PRINT_DEBUG(type, p) ndr_print_debug((ndr_print_fn_t)ndr_print_ ##type, #p, p)
@@ -161,6 +164,9 @@ enum ndr_err_code {
 
 #define NDR_PULL_ALIGN(ndr, n) do { \
 	if (!(ndr->flags & LIBNDR_FLAG_NOALIGN)) { \
+		if (ndr->flags & LIBNDR_FLAG_PAD_CHECK) { \
+			ndr_check_padding(ndr, n); \
+		} \
 		ndr->offset = (ndr->offset + (n-1)) & ~(n-1); \
 	} \
 	if (ndr->offset >= ndr->data_size) { \
diff --git a/source4/librpc/ndr/ndr_basic.c b/source4/librpc/ndr/ndr_basic.c
index 7f36f7e4ba..d015cc5e48 100644
--- a/source4/librpc/ndr/ndr_basic.c
+++ b/source4/librpc/ndr/ndr_basic.c
@@ -28,6 +28,31 @@
 #define NDR_SSVAL(ndr, ofs, v) do { if (NDR_BE(ndr))  { RSSVAL(ndr->data,ofs,v); } else SSVAL(ndr->data,ofs,v); } while (0)
 #define NDR_SIVAL(ndr, ofs, v) do { if (NDR_BE(ndr))  { RSIVAL(ndr->data,ofs,v); } else SIVAL(ndr->data,ofs,v); } while (0)
 
+
+/*
+  check for data leaks from the server by looking for non-zero pad bytes
+  these could also indicate that real structure elements have been
+  mistaken for padding in the IDL
+*/
+void ndr_check_padding(struct ndr_pull *ndr, size_t n)
+{
+	size_t ofs2 = (ndr->offset + (n-1)) & ~(n-1);
+	int i;
+	for (i=ndr->offset;i<ofs2;i++) {
+		if (ndr->data[i] != 0) {
+			break;
+		}
+	}
+	if (i<ofs2) {
+		DEBUG(0,("WARNING: Non-zero padding to %d: ", n));
+		for (i=ndr->offset;i<ofs2;i++) {
+			DEBUG(0,("%02x ", ndr->data[i]));
+		}
+		DEBUG(0,("\n"));
+	}
+
+}
+
 /*
   parse a uint8
 */
diff --git a/source4/librpc/rpc/dcerpc.c b/source4/librpc/rpc/dcerpc.c
index ae56213919..ec22696419 100644
--- a/source4/librpc/rpc/dcerpc.c
+++ b/source4/librpc/rpc/dcerpc.c
@@ -102,16 +102,33 @@ void dcerpc_set_auth_length(DATA_BLOB *blob, uint16_t v)
 	}
 }
 
+
+/*
+  setup for a ndr pull, also setting up any flags from the binding string
+*/
+static struct ndr_pull *ndr_pull_init_flags(struct dcerpc_pipe *p, DATA_BLOB *blob, TALLOC_CTX *mem_ctx)
+{
+	struct ndr_pull *ndr = ndr_pull_init_blob(blob, mem_ctx);
+
+	if (ndr == NULL) return ndr;
+
+	if (p->flags & DCERPC_DEBUG_PAD_CHECK) {
+		ndr->flags |= LIBNDR_FLAG_PAD_CHECK;
+	}
+
+	return ndr;
+}
+
 /* 
    parse a data blob into a dcerpc_packet structure. This handles both
    input and output packets
 */
-static NTSTATUS dcerpc_pull(DATA_BLOB *blob, TALLOC_CTX *mem_ctx, 
+static NTSTATUS dcerpc_pull(struct dcerpc_pipe *p, DATA_BLOB *blob, TALLOC_CTX *mem_ctx, 
 			    struct dcerpc_packet *pkt)
 {
 	struct ndr_pull *ndr;
 
-	ndr = ndr_pull_init_blob(blob, mem_ctx);
+	ndr = ndr_pull_init_flags(p, blob, mem_ctx);
 	if (!ndr) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -137,10 +154,10 @@ static NTSTATUS dcerpc_pull_request_sign(struct dcerpc_pipe *p,
 
 	/* non-signed packets are simpler */
 	if (!p->security_state.auth_info || !p->security_state.generic_state) {
-		return dcerpc_pull(blob, mem_ctx, pkt);
+		return dcerpc_pull(p, blob, mem_ctx, pkt);
 	}
 
-	ndr = ndr_pull_init_blob(blob, mem_ctx);
+	ndr = ndr_pull_init_flags(p, blob, mem_ctx);
 	if (!ndr) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -172,7 +189,7 @@ static NTSTATUS dcerpc_pull_request_sign(struct dcerpc_pipe *p,
 	pkt->u.response.stub_and_verifier.length -= auth_blob.length;
 
 	/* pull the auth structure */
-	ndr = ndr_pull_init_blob(&auth_blob, mem_ctx);
+	ndr = ndr_pull_init_flags(p, &auth_blob, mem_ctx);
 	if (!ndr) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -439,7 +456,7 @@ NTSTATUS dcerpc_bind(struct dcerpc_pipe *p,
 	}
 
 	/* unmarshall the NDR */
-	status = dcerpc_pull(&blob, mem_ctx, &pkt);
+	status = dcerpc_pull(p, &blob, mem_ctx, &pkt);
 	if (!NT_STATUS_IS_OK(status)) {
 		return status;
 	}
@@ -513,7 +530,7 @@ NTSTATUS dcerpc_alter(struct dcerpc_pipe *p,
 	}
 
 	/* unmarshall the NDR */
-	status = dcerpc_pull(&blob, mem_ctx, &pkt);
+	status = dcerpc_pull(p, &blob, mem_ctx, &pkt);
 	if (!NT_STATUS_IS_OK(status)) {
 		return status;
 	}
@@ -855,7 +872,8 @@ NTSTATUS dcerpc_request(struct dcerpc_pipe *p,
   for that to the NDR we initially generated. If they don't match then we know
   we must have a bug in either the pull or push side of our code
 */
-static NTSTATUS dcerpc_ndr_validate_in(TALLOC_CTX *mem_ctx,
+static NTSTATUS dcerpc_ndr_validate_in(struct dcerpc_pipe *p, 
+				       TALLOC_CTX *mem_ctx,
 				       DATA_BLOB blob,
 				       size_t struct_size,
 				       NTSTATUS (*ndr_push)(struct ndr_push *, int, void *),
@@ -872,7 +890,7 @@ static NTSTATUS dcerpc_ndr_validate_in(TALLOC_CTX *mem_ctx,
 		return NT_STATUS_NO_MEMORY;
 	}
 
-	pull = ndr_pull_init_blob(&blob, mem_ctx);
+	pull = ndr_pull_init_flags(p, &blob, mem_ctx);
 	if (!pull) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -918,7 +936,8 @@ static NTSTATUS dcerpc_ndr_validate_in(TALLOC_CTX *mem_ctx,
   initially generated. If they don't match then we know we must have a
   bug in either the pull or push side of our code
 */
-static NTSTATUS dcerpc_ndr_validate_out(TALLOC_CTX *mem_ctx,
+static NTSTATUS dcerpc_ndr_validate_out(struct dcerpc_pipe *p,
+					TALLOC_CTX *mem_ctx,
 					void *struct_ptr,
 					size_t struct_size,
 					NTSTATUS (*ndr_push)(struct ndr_push *, int, void *),
@@ -950,7 +969,7 @@ static NTSTATUS dcerpc_ndr_validate_out(TALLOC_CTX *mem_ctx,
 
 	blob = ndr_push_blob(push);
 
-	pull = ndr_pull_init_blob(&blob, mem_ctx);
+	pull = ndr_pull_init_flags(p, &blob, mem_ctx);
 	if (!pull) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -1032,7 +1051,7 @@ struct rpc_request *dcerpc_ndr_request_send(struct dcerpc_pipe *p,
 	request = ndr_push_blob(push);
 
 	if (p->flags & DCERPC_DEBUG_VALIDATE_IN) {
-		status = dcerpc_ndr_validate_in(mem_ctx, request, struct_size, 
+		status = dcerpc_ndr_validate_in(p, mem_ctx, request, struct_size, 
 						ndr_push, ndr_pull);
 		if (!NT_STATUS_IS_OK(status)) {
 			DEBUG(2,("Validation failed in dcerpc_ndr_request_send - %s\n",
@@ -1086,7 +1105,7 @@ NTSTATUS dcerpc_ndr_request_recv(struct rpc_request *req)
 	talloc_free(req);
 
 	/* prepare for ndr_pull_* */
-	pull = ndr_pull_init_blob(&response, ndr.mem_ctx);
+	pull = ndr_pull_init_flags(p, &response, ndr.mem_ctx);
 	if (!pull) {
 		return NT_STATUS_NO_MEMORY;
 	}
@@ -1105,7 +1124,7 @@ NTSTATUS dcerpc_ndr_request_recv(struct rpc_request *req)
 	}
 
 	if (p->flags & DCERPC_DEBUG_VALIDATE_OUT) {
-		status = dcerpc_ndr_validate_out(ndr.mem_ctx, ndr.struct_ptr, ndr.struct_size, 
+		status = dcerpc_ndr_validate_out(p, ndr.mem_ctx, ndr.struct_ptr, ndr.struct_size, 
 						 ndr.ndr_push, ndr.ndr_pull);
 		if (!NT_STATUS_IS_OK(status)) {
 			return status;
diff --git a/source4/librpc/rpc/dcerpc.h b/source4/librpc/rpc/dcerpc.h
index 91899a9fec..1443e10927 100644
--- a/source4/librpc/rpc/dcerpc.h
+++ b/source4/librpc/rpc/dcerpc.h
@@ -101,6 +101,9 @@ struct dcerpc_pipe {
 
 #define DCERPC_AUTH_OPTIONS    (DCERPC_SEAL|DCERPC_SIGN|DCERPC_SCHANNEL_ANY)
 
+/* check incoming pad bytes */
+#define DCERPC_DEBUG_PAD_CHECK         (1<<12)
+
 /*
   this is used to find pointers to calls
 */
diff --git a/source4/librpc/rpc/dcerpc_util.c b/source4/librpc/rpc/dcerpc_util.c
index 5a3b875c01..c04937353c 100644
--- a/source4/librpc/rpc/dcerpc_util.c
+++ b/source4/librpc/rpc/dcerpc_util.c
@@ -277,6 +277,7 @@ static const struct {
 	{"seal", DCERPC_SEAL},
 	{"validate", DCERPC_DEBUG_VALIDATE_BOTH},
 	{"print", DCERPC_DEBUG_PRINT_BOTH},
+	{"padcheck", DCERPC_DEBUG_PAD_CHECK},
 	{"bigendian", DCERPC_PUSH_BIGENDIAN}
 };