path: root/net/samba416/files/0026-vfs-add-a-compatibility-option-to-the-vfs_streams_xa.patch

From 2d73ccb27ffcdf419d569260fcca6e9ee3b9538a Mon Sep 17 00:00:00 2001
From: "Timur I. Bakeyev" <timur@FreeBSD.org>
Date: Thu, 29 Sep 2022 03:24:26 +0200
Subject: [PATCH 26/28] vfs: add a compatibility option to the
 vfs_streams_xattr

When enabled, the module does not append a trailing 0
byte to the end of the extended attribute data.

This is primarily a consideration when the administrator
wishes to expose extended attributes that have been written
by another application as alternate data streams via
Samba.

An example where this parameter may be required is when
migrating a netatalk share to Samba. See manpage for
vfs_fruit for additional considerations regarding
Netatalk and Samba compatibility.

Signed-off-by: Timur I. Bakeyev <timur@FreeBSD.org>
---
 docs-xml/manpages/vfs_streams_xattr.8.xml | 25 ++++++
 source3/modules/vfs_streams_xattr.c       | 95 +++++++++++++++++------
 2 files changed, 97 insertions(+), 23 deletions(-)

diff --git a/docs-xml/manpages/vfs_streams_xattr.8.xml b/docs-xml/manpages/vfs_streams_xattr.8.xml
index 6645928c016..0f38d510a82 100644
--- a/docs-xml/manpages/vfs_streams_xattr.8.xml
+++ b/docs-xml/manpages/vfs_streams_xattr.8.xml
@@ -71,6 +71,31 @@
 	    </listitem>
 	  </varlistentry>
 
+	  <varlistentry>
+	    <term>streams_xattr:xattr_compat = [yes|no]</term>
+	    <listitem>
+	      <para>When enabled, the module does not append a trailing 0
+	      byte to the end of the extended attribute data. This parameter
+	      must not be changed once data has been written to the share
+	      since it may result in dropping the last byte from xattr data.
+
+	      This is primarily a consideration when the administrator
+	      wishes to expose extended attributes that have been written
+	      by another application as alternate data streams via
+	      Samba.
+
+	      An example where this parameter may be required is when
+	      migrating a netatalk share to Samba. See manpage for
+	      vfs_fruit for additional considerations regarding
+	      Netatalk and Samba compatibility.
+
+	      WARNING: this parameter must not be changed on existing
+	      Samba shares or new shares that export paths currently
+	      or previously have been shared by Samba.
+	      The default is <command>yes</command>.</para>
+	    </listitem>
+	  </varlistentry>
+
 	</variablelist>
 
 </refsect1>
diff --git a/source3/modules/vfs_streams_xattr.c b/source3/modules/vfs_streams_xattr.c
index b69a4f342f5..070111e3ee9 100644
--- a/source3/modules/vfs_streams_xattr.c
+++ b/source3/modules/vfs_streams_xattr.c
@@ -35,6 +35,7 @@ struct streams_xattr_config {
 	const char *prefix;
 	size_t prefix_len;
 	bool store_stream_type;
+	int xattr_compat_bytes;
 };
 
 struct stream_io {
@@ -45,22 +46,28 @@ struct stream_io {
 	vfs_handle_struct *handle;
 };
 
-static ssize_t get_xattr_size_fsp(struct files_struct *fsp,
+static ssize_t get_xattr_size_fsp(vfs_handle_struct *handle,
+				  struct files_struct *fsp,
 			          const char *xattr_name)
 {
 	NTSTATUS status;
 	struct ea_struct ea;
 	ssize_t result;
+	struct streams_xattr_config *config = NULL;
+
+	SMB_VFS_HANDLE_GET_DATA(handle, config, struct streams_xattr_config,
+				return -1);
 
 	status = get_ea_value_fsp(talloc_tos(),
 				  fsp,
 				  xattr_name,
 				  &ea);
+
 	if (!NT_STATUS_IS_OK(status)) {
 		return -1;
 	}
 
-	result = ea.value.length-1;
+	result = ea.value.length - config->xattr_compat_bytes;
 	TALLOC_FREE(ea.value.data);
 	return result;
 }
@@ -197,7 +204,8 @@ static int streams_xattr_fstat(vfs_handle_struct *handle, files_struct *fsp,
 		return -1;
 	}
 
-	sbuf->st_ex_size = get_xattr_size_fsp(fsp->base_fsp,
+	sbuf->st_ex_size = get_xattr_size_fsp(handle,
+					      fsp->base_fsp,
 					      io->xattr_name);
 	if (sbuf->st_ex_size == -1) {
 		SET_STAT_INVALID(*sbuf);
@@ -273,7 +281,7 @@ static int streams_xattr_stat(vfs_handle_struct *handle,
 		fsp = fsp->base_fsp;
 	}
 
-	smb_fname->st.st_ex_size = get_xattr_size_fsp(fsp,
+	smb_fname->st.st_ex_size = get_xattr_size_fsp(handle, fsp,
 						      xattr_name);
 	if (smb_fname->st.st_ex_size == -1) {
 		TALLOC_FREE(xattr_name);
@@ -308,6 +316,7 @@ static int streams_xattr_lstat(vfs_handle_struct *handle,
 		errno = ENOENT;
 		return -1;
 	}
+
 	return SMB_VFS_NEXT_LSTAT(handle, smb_fname);
 }
 
@@ -346,6 +355,11 @@ static int streams_xattr_openat(struct vfs_handle_struct *handle,
 	/*
 	 * For now assert this, so the below SMB_VFS_SETXATTR() works.
 	 */
+#ifdef O_EMPTY_PATH
+	if (flags & O_EMPTY_PATH) {
+		return vfs_fake_fd();
+	}
+#endif
 	SMB_ASSERT(fsp_get_pathref_fd(dirfsp) == AT_FDCWD);
 
 	status = streams_xattr_get_name(handle, talloc_tos(),
@@ -355,6 +369,8 @@ static int streams_xattr_openat(struct vfs_handle_struct *handle,
 		goto fail;
 	}
 
+	fsp->fsp_flags.have_proc_fds = fsp->conn->have_proc_fds;
+
 	status = get_ea_value_fsp(talloc_tos(),
 				  fsp->base_fsp,
 				  xattr_name,
@@ -393,7 +409,8 @@ static int streams_xattr_openat(struct vfs_handle_struct *handle,
 		 */
 
 		/*
-		 * Darn, xattrs need at least 1 byte
+		 * If xattr_compat_bytes is set we need to
+		 * provide one extra trailing byte
 		 */
 		char null = '\0';
 
@@ -402,7 +419,8 @@ static int streams_xattr_openat(struct vfs_handle_struct *handle,
 
 		ret = SMB_VFS_FSETXATTR(fsp->base_fsp,
 				       xattr_name,
-				       &null, sizeof(null),
+				       (config->xattr_compat_bytes) ? &null : NULL,
+				       (config->xattr_compat_bytes) ? sizeof(null) : 0,
 				       flags & O_EXCL ? XATTR_CREATE : 0);
 		if (ret != 0) {
 			goto fail;
@@ -411,13 +429,13 @@ static int streams_xattr_openat(struct vfs_handle_struct *handle,
 
 	fakefd = vfs_fake_fd();
 
-        sio = VFS_ADD_FSP_EXTENSION(handle, fsp, struct stream_io, NULL);
-        if (sio == NULL) {
-                errno = ENOMEM;
-                goto fail;
-        }
+	sio = VFS_ADD_FSP_EXTENSION(handle, fsp, struct stream_io, NULL);
+	if (sio == NULL) {
+		errno = ENOMEM;
+		goto fail;
+	}
 
-        sio->xattr_name = talloc_strdup(VFS_MEMCTX_FSP_EXTENSION(handle, fsp),
+	sio->xattr_name = talloc_strdup(VFS_MEMCTX_FSP_EXTENSION(handle, fsp),
 					xattr_name);
 	if (sio->xattr_name == NULL) {
 		errno = ENOMEM;
@@ -823,12 +841,16 @@ static bool collect_one_stream(struct ea_struct *ea, void *private_data)
 {
 	struct streaminfo_state *state =
 		(struct streaminfo_state *)private_data;
+	struct streams_xattr_config *config = NULL;
+
+	SMB_VFS_HANDLE_GET_DATA(state->handle, config, struct streams_xattr_config,
+				return false);
 
 	if (!add_one_stream(state->mem_ctx,
 			    &state->num_streams, &state->streams,
-			    ea->name, ea->value.length-1,
+			    ea->name, ea->value.length - config->xattr_compat_bytes,
 			    smb_roundup(state->handle->conn,
-					ea->value.length-1))) {
+					ea->value.length - config->xattr_compat_bytes))) {
 		state->status = NT_STATUS_NO_MEMORY;
 		return false;
 	}
@@ -890,6 +912,7 @@ static int streams_xattr_connect(vfs_handle_struct *handle,
 	const char *default_prefix = SAMBA_XATTR_DOSSTREAM_PREFIX;
 	const char *prefix;
 	int rc;
+	bool xattr_compat;
 
 	rc = SMB_VFS_NEXT_CONNECT(handle, service, user);
 	if (rc != 0) {
@@ -920,6 +943,13 @@ static int streams_xattr_connect(vfs_handle_struct *handle,
 						 "store_stream_type",
 						 true);
 
+	xattr_compat = lp_parm_bool(SNUM(handle->conn),
+				    "streams_xattr",
+				    "xattr_compat",
+				    true);
+
+        config->xattr_compat_bytes = xattr_compat ? 0 : 1;
+
 	SMB_VFS_HANDLE_SET_DATA(handle, config,
 				NULL, struct stream_xattr_config,
 				return -1);
@@ -936,6 +966,7 @@ static ssize_t streams_xattr_pwrite(vfs_handle_struct *handle,
 	struct ea_struct ea;
 	NTSTATUS status;
 	int ret;
+	struct streams_xattr_config *config = NULL;
 
 	DEBUG(10, ("streams_xattr_pwrite called for %d bytes\n", (int)n));
 
@@ -947,6 +978,9 @@ static ssize_t streams_xattr_pwrite(vfs_handle_struct *handle,
 		return -1;
 	}
 
+	SMB_VFS_HANDLE_GET_DATA(handle, config, struct streams_xattr_config,
+				return -1);
+
 	if ((offset + n) >= lp_smbd_max_xattr_size(SNUM(handle->conn))) {
 		/*
 		 * Requested write is beyond what can be read based on
@@ -976,11 +1010,11 @@ static ssize_t streams_xattr_pwrite(vfs_handle_struct *handle,
 		return -1;
 	}
 
-        if ((offset + n) > ea.value.length-1) {
+        if ((offset + n) > ea.value.length - config->xattr_compat_bytes) {
 		uint8_t *tmp;
 
 		tmp = talloc_realloc(talloc_tos(), ea.value.data, uint8_t,
-					   offset + n + 1);
+					   offset + n + config->xattr_compat_bytes);
 
 		if (tmp == NULL) {
 			TALLOC_FREE(ea.value.data);
@@ -988,8 +1022,10 @@ static ssize_t streams_xattr_pwrite(vfs_handle_struct *handle,
                         return -1;
                 }
 		ea.value.data = tmp;
-		ea.value.length = offset + n + 1;
-		ea.value.data[offset+n] = 0;
+		ea.value.length = offset + n + config->xattr_compat_bytes;
+		if (config->xattr_compat_bytes) {
+			ea.value.data[offset+n] = 0;
+		}
         }
 
         memcpy(ea.value.data + offset, data, n);
@@ -1017,6 +1053,11 @@ static ssize_t streams_xattr_pread(vfs_handle_struct *handle,
 	struct ea_struct ea;
 	NTSTATUS status;
 	size_t length, overlap;
+	struct smb_filename *smb_fname_base = NULL;
+	struct streams_xattr_config *config = NULL;
+
+	SMB_VFS_HANDLE_GET_DATA(handle, config, struct streams_xattr_config,
+				return -1);
 
 	DEBUG(10, ("streams_xattr_pread: offset=%d, size=%d\n",
 		   (int)offset, (int)n));
@@ -1037,7 +1078,7 @@ static ssize_t streams_xattr_pread(vfs_handle_struct *handle,
 		return -1;
 	}
 
-	length = ea.value.length-1;
+	length = ea.value.length - config->xattr_compat_bytes;
 
 	DBG_DEBUG("get_ea_value_fsp returned %d bytes\n",
 		   (int)length);
@@ -1225,6 +1266,12 @@ static int streams_xattr_ftruncate(struct vfs_handle_struct *handle,
         struct stream_io *sio =
 		(struct stream_io *)VFS_FETCH_FSP_EXTENSION(handle, fsp);
 
+	struct smb_filename *smb_fname_base = NULL;
+	struct streams_xattr_config *config = NULL;
+
+	SMB_VFS_HANDLE_GET_DATA(handle, config, struct streams_xattr_config,
+				return -1);
+
 	DEBUG(10, ("streams_xattr_ftruncate called for file %s offset %.0f\n",
 		   fsp_str_dbg(fsp), (double)offset));
 
@@ -1254,14 +1301,16 @@ static int streams_xattr_ftruncate(struct vfs_handle_struct *handle,
 	}
 
 	/* Did we expand ? */
-	if (ea.value.length < offset + 1) {
+	if (ea.value.length < offset + config->xattr_compat_bytes) {
 		memset(&tmp[ea.value.length], '\0',
-			offset + 1 - ea.value.length);
+			offset + config->xattr_compat_bytes - ea.value.length);
 	}
 
 	ea.value.data = tmp;
-	ea.value.length = offset + 1;
-	ea.value.data[offset] = 0;
+	ea.value.length = offset + config->xattr_compat_bytes;
+	if (config->xattr_compat_bytes) {
+		ea.value.data[offset] = 0;
+	}
 
 	ret = SMB_VFS_FSETXATTR(fsp->base_fsp,
 				sio->xattr_name,
-- 
2.37.1