librpc/ndr: add ndr_pull_append/pop()

They can be used to parse a fragmented NDR byte stream.

ndr_pull_append() appends more data that can be processed
and ndr_pull_pop() removed already processed data.

This will be used to implement dcerpc pipes, where we can get
a verify large amount of pipe chunks, once we processed a chunk
we can forget about the related data, but we may need to keep some
bytes in order to get the alignment right.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>

diff --git a/librpc/ndr/libndr.h b/librpc/ndr/libndr.h
index f52038eb3b8db448e9cb863647a5d1bfc176064d..79de7a0f379fd9fd00d2976316d289d105328109 100644 (file)
--- a/librpc/ndr/libndr.h
+++ b/librpc/ndr/libndr.h
@@ -480,6 +480,8 @@ enum ndr_err_code ndr_pull_relative_ptr2(struct ndr_pull *ndr, const void *p);
 enum ndr_err_code ndr_pull_relative_ptr_short(struct ndr_pull *ndr, uint16_t *v);
 size_t ndr_align_size(uint32_t offset, size_t n);
 struct ndr_pull *ndr_pull_init_blob(const DATA_BLOB *blob, TALLOC_CTX *mem_ctx);
+enum ndr_err_code ndr_pull_append(struct ndr_pull *ndr, DATA_BLOB *blob);
+enum ndr_err_code ndr_pull_pop(struct ndr_pull *ndr);
 enum ndr_err_code ndr_pull_advance(struct ndr_pull *ndr, uint32_t size);
 struct ndr_push *ndr_push_init_ctx(TALLOC_CTX *mem_ctx);
 DATA_BLOB ndr_push_blob(struct ndr_push *ndr);

diff --git a/librpc/ndr/ndr.c b/librpc/ndr/ndr.c
index 367a9cde937f0ea47fb630948736e21495edfb40..76073ed0b72b5b8c2684b2eaeac4593c1c5e2f3a 100644 (file)
--- a/librpc/ndr/ndr.c
+++ b/librpc/ndr/ndr.c
@@ -75,6 +75,111 @@ _PUBLIC_ struct ndr_pull *ndr_pull_init_blob(const DATA_BLOB *blob, TALLOC_CTX *
        return ndr;
 }
 
+_PUBLIC_ enum ndr_err_code ndr_pull_append(struct ndr_pull *ndr, DATA_BLOB *blob)
+{
+       enum ndr_err_code ndr_err;
+       DATA_BLOB b;
+       uint32_t append = 0;
+       bool ok;
+
+       if (blob->length == 0) {
+               return NDR_ERR_SUCCESS;
+       }
+
+       ndr_err = ndr_token_retrieve(&ndr->array_size_list, ndr, &append);
+       if (ndr_err == NDR_ERR_TOKEN) {
+               append = 0;
+               ndr_err = NDR_ERR_SUCCESS;
+       }
+       NDR_CHECK(ndr_err);
+
+       if (ndr->data_size == 0) {
+               ndr->data = NULL;
+               append = UINT32_MAX;
+       }
+
+       if (append == UINT32_MAX) {
+               /*
+                * append == UINT32_MAX means that
+                * ndr->data is either NULL or a valid
+                * talloc child of ndr, which means
+                * we can use data_blob_append() without
+                * data_blob_talloc() of the existing callers data
+                */
+               b = data_blob_const(ndr->data, ndr->data_size);
+       } else {
+               b = data_blob_talloc(ndr, ndr->data, ndr->data_size);
+               if (b.data == NULL) {
+                       return ndr_pull_error(ndr, NDR_ERR_ALLOC, "%s", __location__);
+               }
+       }
+
+       ok = data_blob_append(ndr, &b, blob->data, blob->length);
+       if (!ok) {
+               return ndr_pull_error(ndr, NDR_ERR_ALLOC, "%s", __location__);
+       }
+
+       ndr->data = b.data;
+       ndr->data_size = b.length;
+
+       return ndr_token_store(ndr, &ndr->array_size_list, ndr, UINT32_MAX);
+}
+
+_PUBLIC_ enum ndr_err_code ndr_pull_pop(struct ndr_pull *ndr)
+{
+       uint32_t skip = 0;
+       uint32_t append = 0;
+
+       if (ndr->relative_base_offset != 0) {
+               return ndr_pull_error(ndr, NDR_ERR_RELATIVE,
+                                     "%s", __location__);
+       }
+       if (ndr->relative_highest_offset != 0) {
+               return ndr_pull_error(ndr, NDR_ERR_RELATIVE,
+                                     "%s", __location__);
+       }
+       if (ndr->relative_list != NULL) {
+               return ndr_pull_error(ndr, NDR_ERR_RELATIVE,
+                                     "%s", __location__);
+       }
+       if (ndr->relative_base_list != NULL) {
+               return ndr_pull_error(ndr, NDR_ERR_RELATIVE,
+                                     "%s", __location__);
+       }
+
+       /*
+        * we need to keep up to 7 bytes
+        * in order to get the aligment right.
+        */
+       skip = ndr->offset & 0xFFFFFFF8;
+
+       if (skip == 0) {
+               return NDR_ERR_SUCCESS;
+       }
+
+       ndr->offset -= skip;
+       ndr->data_size -= skip;
+
+       append = ndr_token_peek(&ndr->array_size_list, ndr);
+       if (append != UINT32_MAX) {
+               /*
+                * here we assume, that ndr->data is not a
+                * talloc child of ndr.
+                */
+               ndr->data += skip;
+               return NDR_ERR_SUCCESS;
+       }
+
+       memmove(ndr->data, ndr->data + skip, ndr->data_size);
+
+       ndr->data = talloc_realloc(ndr, ndr->data, uint8_t, ndr->data_size);
+       if (ndr->data_size != 0 && ndr->data == NULL) {
+               return ndr_pull_error(ndr, NDR_ERR_ALLOC, "%s", __location__);
+       }
+
+       return NDR_ERR_SUCCESS;
+}
+
 /*
   advance by 'size' bytes
 */