Use "use warnings" rather than -w on the #! line.

[rsync/rsync-patches.git] / munge-links.diff

This patch adds the --munge-links option, which works like the daemon's
"munge symlinks" parameter.

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

    patch -p1 <patches/remote-option.diff
    patch -p1 <patches/munge-links.diff
    ./configure                               (optional if already run)
    make

diff --git a/clientserver.c b/clientserver.c
--- a/clientserver.c
+++ b/clientserver.c
@@ -37,6 +37,7 @@ extern int ignore_errors;
 extern int preserve_xattrs;
 extern int kluge_around_eof;
 extern int daemon_over_rsh;
+extern int munge_symlinks;
 extern int sanitize_paths;
 extern int numeric_ids;
 extern int filesfrom_fd;
@@ -66,7 +67,6 @@ extern iconv_t ic_send, ic_recv;
 char *auth_user;
 int read_only = 0;
 int module_id = -1;
-int munge_symlinks = 0;
 struct chmod_mode_struct *daemon_chmod_modes;
 
 /* module_dirlen is the length of the module_dir string when in daemon
@@ -418,6 +418,7 @@ static int rsync_module(int f_in, int f_out, int i, char *addr, char *host)
 	char *name = lp_name(i);
 	int use_chroot = lp_use_chroot(i);
 	int ret, pre_exec_fd = -1;
+	int save_munge_symlinks;
 	pid_t pre_exec_pid = 0;
 	char *request = NULL;
 
@@ -688,9 +689,11 @@ static int rsync_module(int f_in, int f_out, int i, char *addr, char *host)
 		munge_symlinks = !use_chroot || module_dirlen;
 	if (munge_symlinks) {
 		STRUCT_STAT st;
-		if (do_stat(SYMLINK_PREFIX, &st) == 0 && S_ISDIR(st.st_mode)) {
-			rprintf(FLOG, "Symlink munging is unsupported when a %s directory exists.\n",
-				SYMLINK_PREFIX);
+		char prefix[SYMLINK_PREFIX_LEN]; /* NOT +1 ! */
+		strlcpy(prefix, SYMLINK_PREFIX, sizeof prefix); /* trim the trailing slash */
+		if (do_stat(prefix, &st) == 0 && S_ISDIR(st.st_mode)) {
+			rprintf(FLOG, "Symlink munging is unsafe when a %s directory exists.\n",
+				prefix);
 			io_printf(f_out, "@ERROR: daemon security issue -- contact admin\n", name);
 			exit_cleanup(RERR_UNSUPPORTED);
 		}
@@ -746,6 +749,8 @@ static int rsync_module(int f_in, int f_out, int i, char *addr, char *host)
 	read_args(f_in, name, line, sizeof line, rl_nulls, &argv, &argc, &request);
 	orig_argv = argv;
 
+	save_munge_symlinks = munge_symlinks;
+
 	verbose = 0; /* future verbosity is controlled by client options */
 	ret = parse_arguments(&argc, (const char ***) &argv);
 	if (protect_args && ret) {
@@ -757,6 +762,8 @@ static int rsync_module(int f_in, int f_out, int i, char *addr, char *host)
 	} else
 		orig_early_argv = NULL;
 
+	munge_symlinks = save_munge_symlinks; /* The client mustn't control this. */
+
 	if (pre_exec_pid) {
 		err_msg = finish_pre_exec(pre_exec_pid, pre_exec_fd, request,
 					  orig_early_argv, orig_argv);
diff --git a/options.c b/options.c
--- a/options.c
+++ b/options.c
@@ -105,6 +105,7 @@ int connect_timeout = 0;
 int keep_partial = 0;
 int safe_symlinks = 0;
 int copy_unsafe_links = 0;
+int munge_symlinks = 0;
 int size_only = 0;
 int daemon_bwlimit = 0;
 int bwlimit = 0;
@@ -339,6 +340,7 @@ void usage(enum logcode F)
   rprintf(F," -L, --copy-links            transform symlink into referent file/dir\n");
   rprintf(F,"     --copy-unsafe-links     only \"unsafe\" symlinks are transformed\n");
   rprintf(F,"     --safe-links            ignore symlinks that point outside the source tree\n");
+  rprintf(F,"     --munge-links           munge symlinks to make them safer (but unusable)\n");
   rprintf(F," -k, --copy-dirlinks         transform symlink to a dir into referent dir\n");
   rprintf(F," -K, --keep-dirlinks         treat symlinked dir on receiver as dir\n");
   rprintf(F," -H, --hard-links            preserve hard links\n");
@@ -521,6 +523,8 @@ static struct poptOption long_options[] = {
   {"copy-links",      'L', POPT_ARG_NONE,   &copy_links, 0, 0, 0 },
   {"copy-unsafe-links",0,  POPT_ARG_NONE,   &copy_unsafe_links, 0, 0, 0 },
   {"safe-links",       0,  POPT_ARG_NONE,   &safe_symlinks, 0, 0, 0 },
+  {"munge-links",      0,  POPT_ARG_VAL,    &munge_symlinks, 1, 0, 0 },
+  {"no-munge-links",   0,  POPT_ARG_VAL,    &munge_symlinks, 0, 0, 0 },
   {"copy-dirlinks",   'k', POPT_ARG_NONE,   &copy_dirlinks, 0, 0, 0 },
   {"keep-dirlinks",   'K', POPT_ARG_NONE,   &keep_dirlinks, 0, 0, 0 },
   {"hard-links",      'H', POPT_ARG_NONE,   0, 'H', 0, 0 },
@@ -1472,6 +1476,17 @@ int parse_arguments(int *argc_p, const char ***argv_p)
 		need_messages_from_generator = 1;
 	}
 
+	if (munge_symlinks && !am_daemon) {
+		STRUCT_STAT st;
+		char prefix[SYMLINK_PREFIX_LEN]; /* NOT +1 ! */
+		strlcpy(prefix, SYMLINK_PREFIX, sizeof prefix); /* trim the trailing slash */
+		if (do_stat(prefix, &st) == 0 && S_ISDIR(st.st_mode)) {
+			rprintf(FERROR, "Symlink munging is unsafe when a %s directory exists.\n",
+				prefix);
+			exit_cleanup(RERR_UNSUPPORTED);
+		}
+	}
+
 	if (sanitize_paths) {
 		int i;
 		for (i = argc; i-- > 0; )
diff --git a/pipe.c b/pipe.c
--- a/pipe.c
+++ b/pipe.c
@@ -26,6 +26,7 @@ extern int am_sender;
 extern int am_server;
 extern int blocking_io;
 extern int filesfrom_fd;
+extern int munge_symlinks;
 extern mode_t orig_umask;
 extern char *logfile_name;
 extern int remote_option_cnt;
@@ -133,6 +134,7 @@ pid_t local_child(int argc, char **argv, int *f_in, int *f_out,
 		am_sender = 0;
 		am_server = 1;
 		filesfrom_fd = -1;
+		munge_symlinks = 0; /* Each side needs its own option. */
 		chmod_modes = NULL; /* Let the sending side handle this. */
 
 		/* Let the client side handle this. */
diff --git a/rsync.h b/rsync.h
--- a/rsync.h
+++ b/rsync.h
@@ -32,7 +32,7 @@
 #define DEFAULT_LOCK_FILE "/var/run/rsyncd.lock"
 #define URL_PREFIX "rsync://"
 
-#define SYMLINK_PREFIX "/rsyncd-munged/"
+#define SYMLINK_PREFIX "/rsyncd-munged/"  /* This MUST have a trailing slash! */
 #define SYMLINK_PREFIX_LEN ((int)sizeof SYMLINK_PREFIX - 1)
 
 #define BACKUP_SUFFIX "~"
diff --git a/rsync.yo b/rsync.yo
--- a/rsync.yo
+++ b/rsync.yo
@@ -338,6 +338,7 @@ to the detailed description below for a complete description.  verb(
  -L, --copy-links            transform symlink into referent file/dir
      --copy-unsafe-links     only "unsafe" symlinks are transformed
      --safe-links            ignore symlinks that point outside the tree
+     --munge-links           munge symlinks to make them safer
  -k, --copy-dirlinks         transform symlink to dir into referent dir
  -K, --keep-dirlinks         treat symlinked dir on receiver as dir
  -H, --hard-links            preserve hard links
@@ -795,6 +796,25 @@ which point outside the copied tree. All absolute symlinks are
 also ignored. Using this option in conjunction with bf(--relative) may
 give unexpected results.
 
+dit(bf(--munge-links)) This option tells rsync to (1) modify all symlinks on
+the receiving side in a way that makes them unusable but recoverable (see
+below), or (2) to unmunge symlinks on the sending side that had been stored in
+a munged state.  This is useful if you don't quite trust the source of the data
+to not try to slip in a symlink to a unexpected place.
+
+The way rsync disables the use of symlinks is to prefix each one with the
+string "/rsyncd-munged/".  This prevents the links from being used as long as
+that directory does not exist.  When this option is enabled, rsync will refuse
+to run if that path is a directory or a symlink to a directory.
+
+The option only affects the client side of the transfer, so if you need it to
+affect the server, specify it via bf(--remote-option).  (Note that in a local
+transfer, the client side is the sender.)
+
+This option has no affect on a daemon, since the daemon configures whether it
+wants munged symlinks via its "munge symlinks" parameter.  See also the
+"munge-symlinks" perl script in the support directory of the source code.
+
 dit(bf(-k, --copy-dirlinks)) This option causes the sending side to treat
 a symlink to a directory as though it were a real directory.  This is
 useful if you don't want symlinks to non-directories to be affected, as
diff --git a/rsyncd.conf.yo b/rsyncd.conf.yo
--- a/rsyncd.conf.yo
+++ b/rsyncd.conf.yo
@@ -191,8 +191,9 @@ to translate names, and that it is not possible for a user to change those
 resources.
 
 dit(bf(munge symlinks)) This parameter tells rsync to modify
-all incoming symlinks in a way that makes them unusable but recoverable
-(see below).  This should help protect your files from user trickery when
+all symlinks in the same way as the (non-daemon-affecting)
+bf(--munge-links) command-line option (using a method described below).
+This should help protect your files from user trickery when
 your daemon module is writable.  The default is disabled when "use chroot"
 is on and the inside-chroot path is "/", otherwise it is enabled.