rsync/rsync-2.6.9-munge-symlinks.patch

--- rsync-2.6.9/clientserver.c	2006-10-23 17:36:42.000000000 -0700
+++ ./clientserver.c	2007-11-26 21:32:53.000000000 -0800
@@ -55,6 +55,7 @@ extern struct filter_list_struct server_
 char *auth_user;
 int read_only = 0;
 int module_id = -1;
+int munge_symlinks = 0;
 struct chmod_mode_struct *daemon_chmod_modes;
 
 /* Length of lp_path() string when in daemon mode & not chrooted, else 0. */
@@ -524,6 +525,18 @@ static int rsync_module(int f_in, int f_
 		sanitize_paths = 1;
 	}
 
+	if ((munge_symlinks = lp_munge_symlinks(i)) < 0)
+		munge_symlinks = !use_chroot;
+	if (munge_symlinks) {
+		STRUCT_STAT st;
+		if (stat(SYMLINK_PREFIX, &st) == 0 && S_ISDIR(st.st_mode)) {
+			rprintf(FLOG, "Symlink munging is unsupported when a %s directory exists.\n",
+				SYMLINK_PREFIX);
+			io_printf(f_out, "@ERROR: daemon security issue -- contact admin\n", name);
+			exit_cleanup(RERR_UNSUPPORTED);
+		}
+	}
+
 	if (am_root) {
 		/* XXXX: You could argue that if the daemon is started
 		 * by a non-root user and they explicitly specify a
--- rsync-2.6.9/flist.c	2006-10-13 18:17:36.000000000 -0700
+++ ./flist.c	2007-11-27 12:56:25.000000000 -0800
@@ -53,6 +53,7 @@ extern int copy_links;
 extern int copy_unsafe_links;
 extern int protocol_version;
 extern int sanitize_paths;
+extern int munge_symlinks;
 extern struct stats stats;
 extern struct file_list *the_file_list;
 
@@ -174,6 +175,11 @@ static int readlink_stat(const char *pat
 			}
 			return do_stat(path, stp);
 		}
+		if (munge_symlinks && am_sender && llen > SYMLINK_PREFIX_LEN
+		 && strncmp(linkbuf, SYMLINK_PREFIX, SYMLINK_PREFIX_LEN) == 0) {
+			memmove(linkbuf, linkbuf + SYMLINK_PREFIX_LEN,
+				llen - SYMLINK_PREFIX_LEN + 1);
+		}
 	}
 	return 0;
 #else
@@ -591,6 +597,8 @@ static struct file_struct *receive_file_
 				linkname_len - 1);
 			overflow_exit("receive_file_entry");
 		}
+		if (munge_symlinks)
+			linkname_len += SYMLINK_PREFIX_LEN;
 	}
 	else
 #endif
@@ -658,10 +666,17 @@ static struct file_struct *receive_file_
 #ifdef SUPPORT_LINKS
 	if (linkname_len) {
 		file->u.link = bp;
+		if (munge_symlinks) {
+			strlcpy(bp, SYMLINK_PREFIX, linkname_len);
+			bp += SYMLINK_PREFIX_LEN;
+			linkname_len -= SYMLINK_PREFIX_LEN;
+		}
 		read_sbuf(f, bp, linkname_len - 1);
-		if (sanitize_paths)
+		if (sanitize_paths && !munge_symlinks) {
 			sanitize_path(bp, bp, "", lastdir_depth, NULL);
-		bp += linkname_len;
+			bp += strlen(bp) + 1;
+		} else
+			bp += linkname_len;
 	}
 #endif
 
--- rsync-2.6.9/loadparm.c	2006-10-12 23:49:44.000000000 -0700
+++ ./loadparm.c	2007-11-26 11:46:46.000000000 -0800
@@ -153,6 +153,7 @@ typedef struct
 	BOOL ignore_errors;
 	BOOL ignore_nonreadable;
 	BOOL list;
+	BOOL munge_symlinks;
 	BOOL read_only;
 	BOOL strict_modes;
 	BOOL transfer_logging;
@@ -200,6 +201,7 @@ static service sDefault =
  /* ignore_errors; */		False,
  /* ignore_nonreadable; */	False,
  /* list; */			True,
+ /* munge_symlinks; */		(BOOL)-1,
  /* read_only; */		True,
  /* strict_modes; */		True,
  /* transfer_logging; */	False,
@@ -313,6 +315,7 @@ static struct parm_struct parm_table[] =
  {"log format",        P_STRING, P_LOCAL, &sDefault.log_format,        NULL,0},
  {"max connections",   P_INTEGER,P_LOCAL, &sDefault.max_connections,   NULL,0},
  {"max verbosity",     P_INTEGER,P_LOCAL, &sDefault.max_verbosity,     NULL,0},
+ {"munge symlinks",    P_BOOL,   P_LOCAL, &sDefault.munge_symlinks,    NULL,0},
  {"name",              P_STRING, P_LOCAL, &sDefault.name,              NULL,0},
  {"outgoing chmod",    P_STRING, P_LOCAL, &sDefault.outgoing_chmod,    NULL,0},
  {"path",              P_PATH,   P_LOCAL, &sDefault.path,              NULL,0},
@@ -415,6 +418,7 @@ FN_LOCAL_INTEGER(lp_timeout, timeout)
 FN_LOCAL_BOOL(lp_ignore_errors, ignore_errors)
 FN_LOCAL_BOOL(lp_ignore_nonreadable, ignore_nonreadable)
 FN_LOCAL_BOOL(lp_list, list)
+FN_LOCAL_BOOL(lp_munge_symlinks, munge_symlinks)
 FN_LOCAL_BOOL(lp_read_only, read_only)
 FN_LOCAL_BOOL(lp_strict_modes, strict_modes)
 FN_LOCAL_BOOL(lp_transfer_logging, transfer_logging)
--- rsync-2.6.9/proto.h	2006-11-06 20:39:47.000000000 -0800
+++ ./proto.h	2007-11-27 13:15:23.000000000 -0800
@@ -176,6 +176,7 @@ int lp_timeout(int );
 BOOL lp_ignore_errors(int );
 BOOL lp_ignore_nonreadable(int );
 BOOL lp_list(int );
+BOOL lp_munge_symlinks(int );
 BOOL lp_read_only(int );
 BOOL lp_strict_modes(int );
 BOOL lp_transfer_logging(int );
--- rsync-2.6.9/rsync.h	2006-10-23 20:31:30.000000000 -0700
+++ ./rsync.h	2007-11-26 21:34:11.000000000 -0800
@@ -33,6 +33,9 @@
 #define DEFAULT_LOCK_FILE "/var/run/rsyncd.lock"
 #define URL_PREFIX "rsync://"
 
+#define SYMLINK_PREFIX "/rsyncd-munged/"
+#define SYMLINK_PREFIX_LEN ((int)sizeof SYMLINK_PREFIX - 1)
+
 #define BACKUP_SUFFIX "~"
 
 /* a non-zero CHAR_OFFSET makes the rolling sum stronger, but is
--- rsync-2.6.9/rsyncd.conf.5	2006-11-06 20:39:52.000000000 -0800
+++ ./rsyncd.conf.5	2007-11-27 13:15:23.000000000 -0800
@@ -145,12 +145,15 @@ the advantage of extra protection agains
 holes, but it has the disadvantages of requiring super-user privileges,
 of not being able to follow symbolic links that are either absolute or outside
 of the new root path, and of complicating the preservation of usernames and groups
-(see below)\&.  When "use chroot" is false, for security reasons,
-symlinks may only be relative paths pointing to other files within the root
-path, and leading slashes are removed from most absolute paths (options
-such as \fB\-\-backup\-dir\fP, \fB\-\-compare\-dest\fP, etc\&. interpret an absolute path as
-rooted in the module\&'s "path" dir, just as if chroot was specified)\&.
-The default for "use chroot" is true\&.
+(see below)\&.  When "use chroot" is false, rsync will: (1) munge symlinks by
+default for security reasons (see "munge symlinks" for a way to turn this
+off, but only if you trust your users), (2) substitute leading slashes in
+absolute paths with the module\&'s path (so that options such as
+\fB\-\-backup\-dir\fP, \fB\-\-compare\-dest\fP, etc\&. interpret an absolute path as
+rooted in the module\&'s "path" dir), and (3) trim "\&.\&." path elements from
+args if rsync believes they would escape the chroot\&.
+The default for "use chroot" is true, and is the safer choice (especially
+if the module is not read-only)\&.
 .IP 
 In order to preserve usernames and groupnames, rsync needs to be able to
 use the standard library functions for looking up names and IDs (i\&.e\&.
@@ -181,6 +184,41 @@ access to some of the excluded files ins
 do this automatically, but you might as well specify both to be extra
 sure)\&.
 .IP 
+.IP "\fBmunge symlinks\fP"
+The "munge symlinks" option 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
+your daemon module is writable\&.  The default is disabled when "use chroot"
+is on and enabled when "use chroot" is off\&.
+.IP 
+If you disable this option on a daemon that is not read-only, there
+are tricks that a user can play with uploaded symlinks to access
+daemon-excluded items (if your module has any), and, if "use chroot"
+is off, rsync can even be tricked into showing or changing data that
+is outside the module\&'s path (as access-permissions allow)\&.
+.IP 
+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\&.  When using the "munge symlinks" option in a chroot area,
+you should add this path to the exclude setting for the module so that
+the user can\&'t try to create it\&.
+.IP 
+Note:  rsync makes no attempt to verify that any pre-existing symlinks in
+the hierarchy are as safe as you want them to be\&.  If you setup an rsync
+daemon on a new area or locally add symlinks, you can manually protect your
+symlinks from being abused by prefixing "/rsyncd-munged/" to the start of
+every symlink\&'s value\&.  There is a perl script in the support directory
+of the source code named "munge-symlinks" that can be used to add or remove
+this prefix from your symlinks\&.
+.IP 
+When this option is disabled on a writable module and "use chroot" is off,
+incoming symlinks will be modified to drop a leading slash and to remove "\&.\&."
+path elements that rsync believes will allow a symlink to escape the module\&'s
+hierarchy\&.  There are tricky ways to work around this, though, so you had
+better trust your users if you choose this combination of options\&.
+.IP 
 .IP "\fBmax connections\fP"
 The "max connections" option allows you to
 specify the maximum number of simultaneous connections you will allow\&.
--- rsync-2.6.9/rsyncd.conf.yo	2006-11-06 20:39:47.000000000 -0800
+++ ./rsyncd.conf.yo	2007-11-27 13:14:07.000000000 -0800
@@ -129,12 +129,15 @@ the advantage of extra protection agains
 holes, but it has the disadvantages of requiring super-user privileges,
 of not being able to follow symbolic links that are either absolute or outside
 of the new root path, and of complicating the preservation of usernames and groups
-(see below).  When "use chroot" is false, for security reasons,
-symlinks may only be relative paths pointing to other files within the root
-path, and leading slashes are removed from most absolute paths (options
-such as bf(--backup-dir), bf(--compare-dest), etc. interpret an absolute path as
-rooted in the module's "path" dir, just as if chroot was specified).
-The default for "use chroot" is true.
+(see below).  When "use chroot" is false, rsync will: (1) munge symlinks by
+default for security reasons (see "munge symlinks" for a way to turn this
+off, but only if you trust your users), (2) substitute leading slashes in
+absolute paths with the module's path (so that options such as
+bf(--backup-dir), bf(--compare-dest), etc. interpret an absolute path as
+rooted in the module's "path" dir), and (3) trim ".." path elements from
+args if rsync believes they would escape the chroot.
+The default for "use chroot" is true, and is the safer choice (especially
+if the module is not read-only).
 
 In order to preserve usernames and groupnames, rsync needs to be able to
 use the standard library functions for looking up names and IDs (i.e.
@@ -158,6 +161,40 @@ access to some of the excluded files ins
 do this automatically, but you might as well specify both to be extra
 sure).
 
+dit(bf(munge symlinks))  The "munge symlinks" option 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
+your daemon module is writable.  The default is disabled when "use chroot"
+is on and enabled when "use chroot" is off.
+
+If you disable this option on a daemon that is not read-only, there
+are tricks that a user can play with uploaded symlinks to access
+daemon-excluded items (if your module has any), and, if "use chroot"
+is off, rsync can even be tricked into showing or changing data that
+is outside the module's path (as access-permissions allow).
+
+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.  When using the "munge symlinks" option in a chroot area,
+you should add this path to the exclude setting for the module so that
+the user can't try to create it.
+
+Note:  rsync makes no attempt to verify that any pre-existing symlinks in
+the hierarchy are as safe as you want them to be.  If you setup an rsync
+daemon on a new area or locally add symlinks, you can manually protect your
+symlinks from being abused by prefixing "/rsyncd-munged/" to the start of
+every symlink's value.  There is a perl script in the support directory
+of the source code named "munge-symlinks" that can be used to add or remove
+this prefix from your symlinks.
+
+When this option is disabled on a writable module and "use chroot" is off,
+incoming symlinks will be modified to drop a leading slash and to remove ".."
+path elements that rsync believes will allow a symlink to escape the module's
+hierarchy.  There are tricky ways to work around this, though, so you had
+better trust your users if you choose this combination of options.
+
 dit(bf(max connections)) The "max connections" option allows you to
 specify the maximum number of simultaneous connections you will allow.
 Any clients connecting when the maximum has been reached will receive a
--- rsync-2.6.9/support/munge-symlinks	1969-12-31 16:00:00.000000000 -0800
+++ ./support/munge-symlinks	2007-11-26 22:04:26.000000000 -0800
@@ -0,0 +1,60 @@
+#!/usr/bin/perl
+# This script will either prefix all symlink values with the string
+# "/rsyncd-munged/" or remove that prefix.
+
+use strict;
+use Getopt::Long;
+
+my $SYMLINK_PREFIX = '/rsyncd-munged/';
+
+my $munge_opt;
+
+&GetOptions(
+    'munge' => sub { $munge_opt = 1 },
+    'unmunge' => sub { $munge_opt = 0 },
+    'all' => \( my $all_opt ),
+    'help|h' => \( my $help_opt ),
+) or &usage;
+
+&usage if $help_opt || !defined $munge_opt;
+
+my $munged_re = $all_opt ? qr/^($SYMLINK_PREFIX)+(?=.)/ : qr/^$SYMLINK_PREFIX(?=.)/;
+
+push(@ARGV, '.') unless @ARGV;
+
+open(PIPE, '-|', 'find', @ARGV, '-type', 'l') or die $!;
+
+while (<PIPE>) {
+    chomp;
+    my $lnk = readlink($_) or next;
+    if ($munge_opt) {
+	next if !$all_opt && $lnk =~ /$munged_re/;
+	$lnk =~ s/^/$SYMLINK_PREFIX/;
+    } else {
+	next unless $lnk =~ s/$munged_re//;
+    }
+    if (!unlink($_)) {
+	warn "Unable to unlink symlink: $_ ($!)\n";
+    } elsif (!symlink($lnk, $_)) {
+	warn "Unable to recreate symlink: $_ -> $lnk ($!)\n";
+    } else {
+	print "$_ -> $lnk\n";
+    }
+}
+
+close PIPE;
+exit;
+
+sub usage
+{
+    die <<EOT;
+Usage: munge-symlinks --munge|--unmunge [--all] [DIR|SYMLINK...]
+
+--munge      Add the $SYMLINK_PREFIX prefix to symlinks if not already
+             present, or always when combined with --all.
+--unmunge    Remove one $SYMLINK_PREFIX prefix from symlinks or all
+             such prefixes with --all.
+
+See the "munge symlinks" option in the rsyncd.conf manpage for more details.
+EOT
+}
--- rsync-2.6.9/testsuite/rsync.fns	2006-05-30 11:26:17.000000000 -0700
+++ ./testsuite/rsync.fns	2007-11-26 11:49:35.000000000 -0800
@@ -231,6 +231,7 @@ build_rsyncd_conf() {
 
 pid file = $pidfile
 use chroot = no
+munge symlinks = no
 hosts allow = localhost 127.0.0.1 $hostname
 log file = $logfile
 log format = %i %h [%a] %m (%u) %l %f%L