Must bump the value of name_len when adding the rsync prefix.

[rsync/rsync-patches.git] / fake-super.diff

This patch adds a new option:  --fake-super, which tells rsync to copy in a
fake super-user mode that stores various file attributes in an extended-
attribute value instead of as real file-system attributes.  See the changes
to the manpages for details.

To use this patch, run these commands for a successful build:

    patch -p1 <patches/acls.diff
    patch -p1 <patches/xattrs.diff
    patch -p1 <patches/fake-super.diff
    ./prepare-source
    ./configure --enable-xattr-support
    make

If you want ACL support too, use this configure command instead of the one
above:

    ./configure --enable-acl-support --enable-xattr-support

--- old/backup.c
+++ new/backup.c
@@ -129,7 +129,7 @@ static int make_bak_dir(char *fullpath)
 		if (p >= rel) {
 			/* Try to transfer the directory settings of the
 			 * actual dir that the files are coming from. */
-			if (do_stat(rel, &sx.st) < 0) {
+			if (x_stat(rel, &sx.st, NULL) < 0) {
 				rsyserr(FERROR, errno,
 					"make_bak_dir stat %s failed",
 					full_fname(rel));
@@ -200,7 +200,7 @@ static int keep_backup(char *fname)
 	int ret_code;
 
 	/* return if no file to keep */
-	if (do_lstat(fname, &sx.st) < 0)
+	if (x_lstat(fname, &sx.st, NULL) < 0)
 		return 1;
 #ifdef SUPPORT_ACLS
 	sx.acc_acl = sx.def_acl = NULL;
--- old/clientserver.c
+++ new/clientserver.c
@@ -625,6 +625,11 @@ static int rsync_module(int f_in, int f_
 	ret = parse_arguments(&argc, (const char ***) &argv, 0);
 	quiet = 0; /* Don't let someone try to be tricky. */
 
+	if (lp_fake_super(i))
+		am_root = -1;
+	else if (am_root < 0) /* Treat --fake-super from client as --super. */
+		am_root = 2;
+
 	if (filesfrom_fd == 0)
 		filesfrom_fd = f_in;
 
--- old/flist.c
+++ new/flist.c
@@ -181,7 +181,7 @@ static int readlink_stat(const char *pat
 	}
 	return 0;
 #else
-	return do_stat(path, stp);
+	return x_stat(path, stp, NULL);
 #endif
 }
 
@@ -189,17 +189,17 @@ int link_stat(const char *path, STRUCT_S
 {
 #ifdef SUPPORT_LINKS
 	if (copy_links)
-		return do_stat(path, stp);
-	if (do_lstat(path, stp) < 0)
+		return x_stat(path, stp, NULL);
+	if (x_lstat(path, stp, NULL) < 0)
 		return -1;
 	if (follow_dirlinks && S_ISLNK(stp->st_mode)) {
 		STRUCT_STAT st;
-		if (do_stat(path, &st) == 0 && S_ISDIR(st.st_mode))
+		if (x_stat(path, &st, NULL) == 0 && S_ISDIR(st.st_mode))
 			*stp = st;
 	}
 	return 0;
 #else
-	return do_stat(path, stp);
+	return x_stat(path, stp, NULL);
 #endif
 }
 
@@ -234,26 +234,6 @@ static int is_excluded(char *fname, int 
 	return 0;
 }
 
-static int to_wire_mode(mode_t mode)
-{
-#ifdef SUPPORT_LINKS
-#if _S_IFLNK != 0120000
-	if (S_ISLNK(mode))
-		return (mode & ~(_S_IFMT)) | 0120000;
-#endif
-#endif
-	return mode;
-}
-
-static mode_t from_wire_mode(int mode)
-{
-#if _S_IFLNK != 0120000
-	if ((mode & (_S_IFMT)) == 0120000)
-		return (mode & ~(_S_IFMT)) | _S_IFLNK;
-#endif
-	return mode;
-}
-
 static void send_directory(int f, struct file_list *flist,
 			   char *fbuf, int len);
 
@@ -793,7 +773,7 @@ struct file_struct *make_file(char *fnam
 		if (save_errno == ENOENT) {
 #ifdef SUPPORT_LINKS
 			/* Avoid "vanished" error if symlink points nowhere. */
-			if (copy_links && do_lstat(thisname, &st) == 0
+			if (copy_links && x_lstat(thisname, &st, NULL) == 0
 			    && S_ISLNK(st.st_mode)) {
 				io_error |= IOERR_GENERAL;
 				rprintf(FERROR, "symlink has no referent: %s\n",
@@ -963,7 +943,7 @@ struct file_struct *make_file(char *fnam
 		int save_mode = file->mode;
 		file->mode = S_IFDIR; /* Find a directory with our name. */
 		if (flist_find(the_file_list, file) >= 0
-		    && do_stat(thisname, &st2) == 0 && S_ISDIR(st2.st_mode)) {
+		    && x_stat(thisname, &st2, NULL) == 0 && S_ISDIR(st2.st_mode)) {
 			file->modtime = st2.st_mtime;
 			file->length = st2.st_size;
 			file->mode = st2.st_mode;
--- old/loadparm.c
+++ new/loadparm.c
@@ -150,6 +150,7 @@ typedef struct
 	int syslog_facility;
 	int timeout;
 
+	BOOL fake_super;
 	BOOL ignore_errors;
 	BOOL ignore_nonreadable;
 	BOOL list;
@@ -197,6 +198,7 @@ static service sDefault =
  /* syslog_facility; */		LOG_DAEMON,
  /* timeout; */			0,
 
+ /* fake_super; */		False,
  /* ignore_errors; */		False,
  /* ignore_nonreadable; */	False,
  /* list; */			True,
@@ -298,6 +300,7 @@ static struct parm_struct parm_table[] =
  {"dont compress",     P_STRING, P_LOCAL, &sDefault.dont_compress,     NULL,0},
  {"exclude from",      P_STRING, P_LOCAL, &sDefault.exclude_from,      NULL,0},
  {"exclude",           P_STRING, P_LOCAL, &sDefault.exclude,           NULL,0},
+ {"fake super",        P_BOOL,   P_LOCAL, &sDefault.fake_super,        NULL,0},
  {"filter",            P_STRING, P_LOCAL, &sDefault.filter,            NULL,0},
  {"gid",               P_STRING, P_LOCAL, &sDefault.gid,               NULL,0},
  {"hosts allow",       P_STRING, P_LOCAL, &sDefault.hosts_allow,       NULL,0},
@@ -412,6 +415,7 @@ FN_LOCAL_INTEGER(lp_max_connections, max
 FN_LOCAL_INTEGER(lp_max_verbosity, max_verbosity)
 FN_LOCAL_INTEGER(lp_timeout, timeout)
 
+FN_LOCAL_BOOL(lp_fake_super, fake_super)
 FN_LOCAL_BOOL(lp_ignore_errors, ignore_errors)
 FN_LOCAL_BOOL(lp_ignore_nonreadable, ignore_nonreadable)
 FN_LOCAL_BOOL(lp_list, list)
@@ -816,7 +820,7 @@ BOOL lp_load(char *pszFname, int globals
 
 	if (pszFname)
 	    pstrcpy(n2,pszFname);
-	else if (am_server && !am_root)
+	else if (am_server && am_root <= 0)
 	    pstrcpy(n2,RSYNCD_USERCONF);
 	else
 	    pstrcpy(n2,RSYNCD_SYSCONF);
--- old/options.c
+++ new/options.c
@@ -73,7 +73,7 @@ int protocol_version = PROTOCOL_VERSION;
 int sparse_files = 0;
 int do_compression = 0;
 int def_compress_level = Z_DEFAULT_COMPRESSION;
-int am_root = 0;
+int am_root = 0; /* 0 = normal, 1 = root, 2 = --super, -1 = --fake-super */
 int am_server = 0;
 int am_sender = 0;
 int am_generator = 0;
@@ -329,6 +329,9 @@ void usage(enum logcode F)
   rprintf(F," -t, --times                 preserve times\n");
   rprintf(F," -O, --omit-dir-times        omit directories when preserving times\n");
   rprintf(F,"     --super                 receiver attempts super-user activities\n");
+#ifdef SUPPORT_XATTRS
+  rprintf(F,"     --fake-super            store/recover privileged attrs using xattrs\n");
+#endif
   rprintf(F," -S, --sparse                handle sparse files efficiently\n");
   rprintf(F," -n, --dry-run               show what would have been transferred\n");
   rprintf(F," -W, --whole-file            copy files whole (without rsync algorithm)\n");
@@ -453,6 +456,7 @@ static struct poptOption long_options[] 
   {"modify-window",    0,  POPT_ARG_INT,    &modify_window, OPT_MODIFY_WINDOW, 0, 0 },
   {"super",            0,  POPT_ARG_VAL,    &am_root, 2, 0, 0 },
   {"no-super",         0,  POPT_ARG_VAL,    &am_root, 0, 0, 0 },
+  {"fake-super",       0,  POPT_ARG_VAL,    &am_root, -1, 0, 0 },
   {"owner",           'o', POPT_ARG_VAL,    &preserve_uid, 1, 0, 0 },
   {"no-owner",         0,  POPT_ARG_VAL,    &preserve_uid, 0, 0, 0 },
   {"no-o",             0,  POPT_ARG_VAL,    &preserve_uid, 0, 0, 0 },
@@ -1178,6 +1182,14 @@ int parse_arguments(int *argc, const cha
 	}
 #endif
 
+#ifndef SUPPORT_XATTRS
+	if (am_root < 0) {
+		snprintf(err_buf, sizeof err_buf,
+			 "--fake-super requires an rsync with extended attributes enabled\n");
+		return 0;
+	}
+#endif
+
 	if (write_batch && read_batch) {
 		snprintf(err_buf, sizeof err_buf,
 			"--write-batch and --read-batch can not be used together\n");
--- old/rsync.c
+++ new/rsync.c
@@ -196,7 +196,9 @@ int set_file_attrs(char *fname, struct f
 					(long)sxp->st.st_gid, (long)file->gid);
 			}
 		}
-		if (do_lchown(fname,
+		if (am_root < 0) {
+			;
+		} else if (do_lchown(fname,
 		    change_uid ? file->uid : sxp->st.st_uid,
 		    change_gid ? file->gid : sxp->st.st_gid) != 0) {
 			/* shouldn't have attempted to change uid or gid
@@ -205,7 +207,7 @@ int set_file_attrs(char *fname, struct f
 			    change_uid ? "chown" : "chgrp",
 			    full_fname(fname));
 			goto cleanup;
-		}
+		} else
 		/* a lchown had been done - we have to re-stat if the
 		 * destination had the setuid or setgid bits set due
 		 * to the side effect of the chown call */
@@ -222,6 +224,8 @@ int set_file_attrs(char *fname, struct f
 #ifdef SUPPORT_XATTRS
 	if (preserve_xattrs && set_xattr(fname, file, sxp) == 0)
 		updated = 1;
+	if (am_root < 0)
+		set_stat_xattr(fname, file);
 #endif
 #ifdef SUPPORT_ACLS
 	/* It's OK to call set_acl() now, even for a dir, as the generator
@@ -236,7 +240,7 @@ int set_file_attrs(char *fname, struct f
 
 #ifdef HAVE_CHMOD
 	if ((sxp->st.st_mode & CHMOD_BITS) != (new_mode & CHMOD_BITS)) {
-		int ret = do_chmod(fname, new_mode);
+		int ret = am_root < 0 ? 0 : do_chmod(fname, new_mode);
 		if (ret < 0) {
 			rsyserr(FERROR, errno,
 				"failed to set permissions on %s",
--- old/rsync.h
+++ new/rsync.h
@@ -707,6 +707,12 @@ typedef struct {
 
 #include "proto.h"
 
+#ifndef SUPPORT_XATTRS
+#define x_stat(fn,fst,xst) do_stat(fn,fst)
+#define x_lstat(fn,fst,xst) do_lstat(fn,fst)
+#define x_fstat(fd,fst,xst) do_fstat(fd,fst)
+#endif
+
 /* We have replacement versions of these if they're missing. */
 #ifndef HAVE_ASPRINTF
 int asprintf(char **ptr, const char *format, ...);
@@ -924,3 +930,23 @@ int inet_pton(int af, const char *src, v
 #ifdef MAINTAINER_MODE
 const char *get_panic_action(void);
 #endif
+
+static inline int to_wire_mode(mode_t mode)
+{
+#ifdef SUPPORT_LINKS
+#if _S_IFLNK != 0120000
+	if (S_ISLNK(mode))
+		return (mode & ~(_S_IFMT)) | 0120000;
+#endif
+#endif
+	return mode;
+}
+
+static inline mode_t from_wire_mode(int mode)
+{
+#if _S_IFLNK != 0120000
+	if ((mode & (_S_IFMT)) == 0120000)
+		return (mode & ~(_S_IFMT)) | _S_IFLNK;
+#endif
+	return mode;
+}
--- old/rsync.yo
+++ new/rsync.yo
@@ -333,6 +333,7 @@ to the detailed description below for a 
  -t, --times                 preserve times
  -O, --omit-dir-times        omit directories when preserving times
      --super                 receiver attempts super-user activities
+     --fake-super            store/recover privileged attrs using xattrs
  -S, --sparse                handle sparse files efficiently
  -n, --dry-run               show what would have been transferred
  -W, --whole-file            copy files whole (without rsync algorithm)
@@ -846,7 +847,7 @@ permission value can be applied to the f
 dit(bf(-o, --owner)) This option causes rsync to set the owner of the
 destination file to be the same as the source file, but only if the
 receiving rsync is being run as the super-user (see also the bf(--super)
-option to force rsync to attempt super-user activities).
+and bf(--fake-super) options).
 Without this option, the owner is set to the invoking user on the
 receiving side.
 
@@ -869,7 +870,7 @@ default, but may fall back to using the 
 dit(bf(--devices)) This option causes rsync to transfer character and
 block device files to the remote system to recreate these devices.
 This option has no effect if the receiving rsync is not run as the
-super-user and bf(--super) is not specified.
+super-user (see also the bf(--super) and bf(--fake-super) options).
 
 dit(bf(--specials)) This option causes rsync to transfer special files
 such as named sockets and fifos.
@@ -899,6 +900,33 @@ also for ensuring that you will get erro
 being running as the super-user.  To turn off super-user activities, the
 super-user can use bf(--no-super).
 
+dit(bf(--fake-super)) When this option is enabled, rsync simulates
+super-user activities by saving/restoring the privileged attributes via a
+special extended attribute that is attached to each file (as needed).  This
+includes the file's owner and group (if it is not the default), the file's
+device info (device & special files are created as empty text files), and
+any permission bits that we won't allow to be set on the real file (e.g.
+the real file gets u-s,g-s,o-t for safety) or that would limit the owner's
+access (since the real super-user can always access/change a file or
+directory, the files we create can always be accessed/changed by the
+creating user).
+
+The bf(--fake-super) option only affects the side where the option is used.
+To affect the remote side of a remote-shell connection, specify an rsync
+path:
+
+quote(tt(  rsync -av --rsync-path="rsync --fake-super" /src/ host:/dest/))
+
+Since there is only one "side" in a local copy, this option affects both
+the sending and recieving of files.  You'll need to specify a copy using
+"localhost" if you need to avoid this.  Note, however, that it is always
+safe to copy from some non-fake-super files into some fake-super files
+using a local bf(--fake-super) command because the non-fake source files
+will just have their normal attributes.
+
+See also the "fake super" setting in the daemon's rsyncd.conf file.
+This option is overridden by both bf(--super) and bf(--no-super).
+
 dit(bf(-S, --sparse)) Try to handle sparse files efficiently so they take
 up less space on the destination.  Conflicts with bf(--inplace) because it's
 not possible to overwrite data in a sparse fashion.
--- old/rsyncd.conf.yo
+++ new/rsyncd.conf.yo
@@ -226,6 +226,11 @@ file transfers to and from that module s
 was run as root. This complements the "uid" option. The default is gid -2,
 which is normally the group "nobody".
 
+dit(bf(fake super)) Setting "fake super = yes" for a module causes the
+daemon side to behave as if the bf(--fake-user) command-line option had
+been specified.  This allows the full attributes of a file to be stored
+without having to have the daemon actually running as root.
+
 dit(bf(filter)) The "filter" option allows you to specify a space-separated
 list of filter rules that the daemon will not allow to be read or written.
 This is only superficially equivalent to the client specifying these
--- old/syscall.c
+++ new/syscall.c
@@ -28,6 +28,7 @@
 #endif
 
 extern int dry_run;
+extern int am_root;
 extern int read_only;
 extern int list_only;
 extern int preserve_perms;
@@ -79,6 +80,15 @@ int do_mknod(char *pathname, mode_t mode
 {
 	if (dry_run) return 0;
 	RETURN_ERROR_IF_RO_OR_LO;
+
+	/* For --fake-super, we create a normal file with mode 0600. */
+	if (am_root < 0) {
+		int fd = open(pathname, O_WRONLY|O_CREAT|O_TRUNC, S_IWUSR|S_IRUSR);
+		if (fd < 0 || close(fd) < 0)
+			return -1;
+		return 0;
+	}
+
 #if !defined MKNOD_CREATES_FIFOS && defined HAVE_MKFIFO
 	if (S_ISFIFO(mode))
 		return mkfifo(pathname, mode);
--- old/t_unsafe.c
+++ new/t_unsafe.c
@@ -24,7 +24,11 @@
 
 #include "rsync.h"
 
-int dry_run, read_only, list_only, verbose;
+int dry_run = 0;
+int am_root = 0;
+int read_only = 0;
+int list_only = 0;
+int verbose = 0;
 int preserve_perms = 0;
 
 int
--- old/tls.c
+++ new/tls.c
@@ -39,6 +39,7 @@
 
 /* These are to make syscall.o shut up. */
 int dry_run = 0;
+int am_root = 0;
 int read_only = 1;
 int list_only = 0;
 int preserve_perms = 0;
--- old/trimslash.c
+++ new/trimslash.c
@@ -23,6 +23,7 @@
 
 /* These are to make syscall.o shut up. */
 int dry_run = 0;
+int am_root = 0;
 int read_only = 1;
 int list_only = 0;
 int preserve_perms = 0;
--- old/xattr.c
+++ new/xattr.c
@@ -39,13 +39,23 @@ extern unsigned int file_struct_len;
 #define SYSTEM_PREFIX "system."
 #define SPRE_LEN ((int)sizeof SYSTEM_PREFIX - 1)
 
+#define RSYNC_PREFIX "rsync."
+#define XSTAT_SUFFIX "%stat"
+
 #ifdef HAVE_LINUX_XATTRS
 #define RPRE_LEN 0
+#define FAKE_PREFIX USER_PREFIX RSYNC_PREFIX
+#define FPRE_LEN ((int)sizeof FAKE_PREFIX - 1)
+#define XSTAT_ATTR USER_PREFIX RSYNC_PREFIX XSTAT_SUFFIX
 #else
-#define RSYNC_PREFIX "rsync."
 #define RPRE_LEN ((int)sizeof RSYNC_PREFIX - 1)
+#define FPRE_LEN 0
+#define XSTAT_ATTR RSYNC_PREFIX XSTAT_SUFFIX
 #endif
 
+#define XSTAT_LEN ((int)sizeof XSTAT_ATTR - 1)
+#define CENT_POS (UPRE_LEN + (int)sizeof RSYNC_PREFIX - 1)
+
 typedef struct {
 	char *datum, *name;
 	size_t datum_len, name_len;
@@ -143,6 +153,10 @@ static int rsync_xal_get(const char *fna
 			continue;
 #endif
 
+		if (am_root < 0 && name_len == XSTAT_LEN
+		 && name[CENT_POS] == '%' && strcmp(name, XSTAT_ATTR) == 0)
+			continue;
+
 		datum_len = sys_lgetxattr(fname, name, NULL, 0);
 		if (datum_len < 0) {
 			if (errno == ENOTSUP)
@@ -173,6 +187,13 @@ static int rsync_xal_get(const char *fna
 				return -1;
 			}
 		}
+#ifdef HAVE_LINUX_XATTRS
+		if (am_root < 0 && name_len > FPRE_LEN
+		 && strncmp(name, FAKE_PREFIX, FPRE_LEN) == 0) {
+			name += FPRE_LEN;
+			name_len -= FPRE_LEN;
+		}
+#endif
 		rxas = EXPAND_ITEM_LIST(xalp, rsync_xa, RSYNC_XAL_INITIAL);
 		rxas->name = ptr + datum_len;
 		memcpy(rxas->name, name, name_len);
@@ -293,20 +314,23 @@ void receive_xattr(struct file_struct *f
 			rsync_xa *rxa;
 			size_t name_len = read_int(f);
 			size_t datum_len = read_int(f);
+			size_t extra_len = am_root < 0 ? FPRE_LEN + RPRE_LEN : RPRE_LEN;
 			if (name_len + datum_len < name_len)
 				out_of_memory("receive_xattr"); /* overflow */
-#ifndef HAVE_LINUX_XATTRS
-			if (name_len + datum_len + RPRE_LEN < RPRE_LEN)
+			if (name_len + datum_len + extra_len < extra_len)
 				out_of_memory("receive_xattr"); /* overflow */
-#endif
-			ptr = new_array(char, name_len + datum_len + RPRE_LEN);
+			ptr = new_array(char, name_len + datum_len + extra_len);
 			if (!ptr)
 				out_of_memory("receive_xattr");
-			name = ptr + datum_len + RPRE_LEN;
+			name = ptr + datum_len + extra_len;
 			read_buf(f, name, name_len);
 			read_buf(f, ptr, datum_len);
 #ifdef HAVE_LINUX_XATTRS
 			/* Non-root can only save the user namespace. */
+			if (am_root < 0 && strncmp(name, USER_PREFIX, UPRE_LEN) != 0) {
+				name -= FPRE_LEN;
+				memcpy(name, FAKE_PREFIX, FPRE_LEN);
+			} else
 			if (!am_root && strncmp(name, USER_PREFIX, UPRE_LEN) != 0) {
 				free(ptr);
 				continue;
@@ -323,6 +347,11 @@ void receive_xattr(struct file_struct *f
 				memcpy(name, RSYNC_PREFIX, RPRE_LEN);
 			}
 #endif
+			if (am_root < 0 && name_len == XSTAT_LEN
+			 && name[CENT_POS] == '%' && strcmp(name, XSTAT_ATTR) == 0) {
+				free(ptr);
+				continue;
+			}
 			rxa = EXPAND_ITEM_LIST(&temp_xattr, rsync_xa, count);
 			rxa->name = name;
 			rxa->name_len = name_len;
@@ -403,4 +432,146 @@ int set_xattr(const char *fname, const s
 	return rsync_xal_set(fname, lst + ndx); /* TODO:  This needs to return 1 if no xattrs changed! */
 }
 
+int get_stat_xattr(const char *fname, int fd, STRUCT_STAT *fst, STRUCT_STAT *xst)
+{
+	int mode, rdev_major, rdev_minor, uid, gid, len;
+	char buf[256];
+
+	if (am_root >= 0 || IS_DEVICE(fst->st_mode) || IS_SPECIAL(fst->st_mode))
+		return -1;
+
+	if (xst)
+		*xst = *fst;
+	else
+		xst = fst;
+	if (fname) {
+		fd = -1;
+		len = sys_lgetxattr(fname, XSTAT_ATTR, buf, sizeof buf - 1);
+	} else {
+		fname = "fd";
+		len = sys_fgetxattr(fd, XSTAT_ATTR, buf, sizeof buf - 1);
+	}
+	if (len >= (int)sizeof buf) {
+		len = -1;
+		errno = ERANGE;
+	}
+	if (len < 0) {
+		if (errno == ENOTSUP || errno == ENOATTR)
+			return -1;
+		if (errno == EPERM && S_ISLNK(fst->st_mode)) {
+			xst->st_uid = 0;
+			xst->st_gid = 0;
+			return 0;
+		}
+		rsyserr(FERROR, errno, "failed to read xattr %s for %s",
+			XSTAT_ATTR, full_fname(fname));
+		return -1;
+	}
+	buf[len] = '\0';
+
+	if (sscanf(buf, "%o %d,%d %d:%d",
+		   &mode, &rdev_major, &rdev_minor, &uid, &gid) != 5) {
+		rprintf(FERROR, "Corrupt %s xattr attached to %s: \"%s\"\n",
+			XSTAT_ATTR, full_fname(fname), buf);
+		exit_cleanup(RERR_FILEIO);
+	}
+
+	xst->st_mode = from_wire_mode(mode);
+	xst->st_rdev = MAKEDEV(rdev_major, rdev_minor);
+	xst->st_uid = uid;
+	xst->st_gid = gid;
+
+	return 0;
+}
+
+int set_stat_xattr(const char *fname, struct file_struct *file)
+{
+	STRUCT_STAT fst, xst;
+	dev_t rdev;
+	mode_t mode;
+
+	if (dry_run)
+		return 0;
+
+	if (read_only || list_only) {
+		rsyserr(FERROR, EROFS, "failed to write xattr %s for %s",
+			XSTAT_ATTR, full_fname(fname));
+		return -1;
+	}
+
+	if (x_lstat(fname, &fst, &xst) < 0) {
+		rsyserr(FERROR, errno, "failed to re-stat %s",
+			full_fname(fname));
+		return -1;
+	}
+
+	if (IS_DEVICE(file->mode) || IS_SPECIAL(file->mode))
+		rdev = file->u.rdev;
+	else
+		rdev = 0;
+
+	/* Dump the special permissions and enable full owner access. */
+	mode = (fst.st_mode & ~CHMOD_BITS) | (file->mode & ACCESSPERMS)
+	     | (S_ISDIR(fst.st_mode) ? 0700 : 0600);
+	if (fst.st_mode != mode)
+		do_chmod(fname, mode);
+	if (!IS_DEVICE(fst.st_mode) && !IS_SPECIAL(fst.st_mode))
+		fst.st_rdev = 0; /* just in case */
+
+	if (mode == file->mode && fst.st_rdev == rdev
+	 && fst.st_uid == file->uid && fst.st_gid == file->gid) {
+		/* xst.st_mode will be 0 if there's no current stat xattr */
+		if (xst.st_mode && sys_lremovexattr(fname, XSTAT_ATTR) < 0) {
+			rsyserr(FERROR, errno,
+				"delete of stat xattr failed for %s",
+				full_fname(fname));
+			return -1;
+		}
+		return 0;
+	}
+
+	if (xst.st_mode != file->mode || xst.st_rdev != rdev
+	 || xst.st_uid != file->uid || xst.st_gid != file->gid) {
+		char buf[256];
+		int len = snprintf(buf, sizeof buf, "%o %u,%u %u:%u",
+			to_wire_mode(file->mode) & (_S_IFMT|CHMOD_BITS),
+			(int)major(rdev), (int)minor(rdev),
+			(int)file->uid, (int)file->gid);
+		if (sys_lsetxattr(fname, XSTAT_ATTR, buf, len) < 0) {
+			if (errno == EPERM && S_ISLNK(fst.st_mode))
+				return 0;
+			rsyserr(FERROR, errno,
+				"failed to write xattr %s for %s",
+				XSTAT_ATTR, full_fname(fname));
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+int x_stat(const char *fname, STRUCT_STAT *fst, STRUCT_STAT *xst)
+{
+	int ret = do_stat(fname, fst);
+	if ((ret < 0 || get_stat_xattr(fname, -1, fst, xst) < 0) && xst)
+		xst->st_mode = 0;
+	return ret;
+}
+
+int x_lstat(const char *fname, STRUCT_STAT *fst, STRUCT_STAT *xst)
+{
+	int ret = do_lstat(fname, fst);
+	if ((ret < 0 || get_stat_xattr(fname, -1, fst, xst) < 0) && xst)
+		xst->st_mode = 0;
+	return ret;
+}
+
+int x_fstat(int fd, STRUCT_STAT *fst, STRUCT_STAT *xst)
+{
+	int ret = do_fstat(fd, fst);
+	if ((ret < 0 || get_stat_xattr(NULL, fd, fst, xst) < 0) && xst)
+		xst->st_mode = 0;
+	return ret;
+}
+
 #endif /* SUPPORT_XATTRS */