[PATCH V2 1/2] smb2_ioctl: add support for FSCTL_SRV_COPYCHUNK_WRITE

[David Disseldorp]

FSCTL_SRV_COPYCHUNK can only be used when the client has the copy-chunk
target file open with FILE_WRITE_DATA and FILE_READ_DATA.
FSCTL_SRV_COPYCHUNK_WRITE requires only FILE_WRITE_DATA access on the
target, and is therefore suitable for cp --reflink, which opens the
target file O_WRONLY.

Signed-off-by: David Disseldorp <ddiss at samba.org>
---
 source3/smbd/smb2_ioctl_network_fs.c | 44 ++++++++++++++++++++++++++++--------
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/source3/smbd/smb2_ioctl_network_fs.c b/source3/smbd/smb2_ioctl_network_fs.c
index 1e1e3e5..a1d67f8 100644
--- a/source3/smbd/smb2_ioctl_network_fs.c
+++ b/source3/smbd/smb2_ioctl_network_fs.c
@@ -80,29 +80,37 @@ struct fsctl_srv_copychunk_state {
 };
 static void fsctl_srv_copychunk_vfs_done(struct tevent_req *subreq);
 
-static NTSTATUS copychunk_check_handles(struct files_struct *src_fsp,
+static NTSTATUS copychunk_check_handles(uint32_t ctl_code,
+					struct files_struct *src_fsp,
 					struct files_struct *dst_fsp,
 					struct smb_request *smb1req)
 {
 	/*
 	 * [MS-SMB2] 3.3.5.15.6 Handling a Server-Side Data Copy Request
-	 * If Open.GrantedAccess of the destination file does not
-	 * include FILE_WRITE_DATA, then the request MUST be failed with
-	 * STATUS_ACCESS_DENIED. If Open.GrantedAccess of the
-	 * destination file does not include FILE_READ_DATA access and
-	 * the CtlCode is FSCTL_SRV_COPYCHUNK, then the request MUST be
-	 * failed with STATUS_ACCESS_DENIED.
+	 * The server MUST fail the request with STATUS_ACCESS_DENIED if any of
+	 * the following are true:
+	 * - The Open.GrantedAccess of the destination file does not include
+	 *   FILE_WRITE_DATA or FILE_APPEND_DATA.
 	 */
 	if (!CHECK_WRITE(dst_fsp)) {
 		DEBUG(5, ("copy chunk no write on dest handle (%s).\n",
 			smb_fname_str_dbg(dst_fsp->fsp_name) ));
 		return NT_STATUS_ACCESS_DENIED;
 	}
-	if (!CHECK_READ(dst_fsp, smb1req)) {
+	/*
+	 * - The Open.GrantedAccess of the destination file does not include
+	 *   FILE_READ_DATA, and the CtlCode is FSCTL_SRV_COPYCHUNK.
+	 */
+	if ((ctl_code == FSCTL_SRV_COPYCHUNK)
+	  && !CHECK_READ(dst_fsp, smb1req)) {
 		DEBUG(5, ("copy chunk no read on dest handle (%s).\n",
 			smb_fname_str_dbg(dst_fsp->fsp_name) ));
 		return NT_STATUS_ACCESS_DENIED;
 	}
+	/*
+	 * - The Open.GrantedAccess of the source file does not include
+	 *   FILE_READ_DATA access.
+	 */
 	if (!CHECK_READ(src_fsp, smb1req)) {
 		DEBUG(5, ("copy chunk no read on src handle (%s).\n",
 			smb_fname_str_dbg(src_fsp->fsp_name) ));
@@ -136,6 +144,7 @@ static NTSTATUS copychunk_check_handles(struct files_struct *src_fsp,
 
 static struct tevent_req *fsctl_srv_copychunk_send(TALLOC_CTX *mem_ctx,
 						   struct tevent_context *ev,
+						   uint32_t ctl_code,
 						   struct files_struct *dst_fsp,
 						   DATA_BLOB *in_input,
 						   size_t in_max_output,
@@ -150,6 +159,10 @@ static struct tevent_req *fsctl_srv_copychunk_send(TALLOC_CTX *mem_ctx,
 	struct srv_copychunk *chunk;
 	struct fsctl_srv_copychunk_state *state;
 
+	/* handler for both copy-chunk variants */
+	SMB_ASSERT((ctl_code == FSCTL_SRV_COPYCHUNK)
+		|| (ctl_code == FSCTL_SRV_COPYCHUNK_WRITE));
+
 	req = tevent_req_create(mem_ctx, &state,
 				struct fsctl_srv_copychunk_state);
 	if (req == NULL) {
@@ -188,7 +201,8 @@ static struct tevent_req *fsctl_srv_copychunk_send(TALLOC_CTX *mem_ctx,
 
 	state->dst_fsp = dst_fsp;
 
-	state->status = copychunk_check_handles(state->src_fsp,
+	state->status = copychunk_check_handles(ctl_code,
+						state->src_fsp,
 						state->dst_fsp,
 						smb2req->smb1req);
 	if (!NT_STATUS_IS_OK(state->status)) {
@@ -446,8 +460,18 @@ struct tevent_req *smb2_ioctl_network_fs(uint32_t ctl_code,
 	NTSTATUS status;
 
 	switch (ctl_code) {
+	/*
+	 * [MS-SMB2] 2.2.31
+	 * FSCTL_SRV_COPYCHUNK is issued when a handle has
+	 * FILE_READ_DATA and FILE_WRITE_DATA access to the file;
+	 * FSCTL_SRV_COPYCHUNK_WRITE is issued when a handle only has
+	 * FILE_WRITE_DATA access.
+	 */
+	case FSCTL_SRV_COPYCHUNK_WRITE:	/* FALL THROUGH */
 	case FSCTL_SRV_COPYCHUNK:
-		subreq = fsctl_srv_copychunk_send(state, ev, state->fsp,
+		subreq = fsctl_srv_copychunk_send(state, ev,
+						  ctl_code,
+						  state->fsp,
 						  &state->in_input,
 						  state->in_max_output,
 						  state->smb2req);
-- 
1.8.1.4