From 502ab0eff1bba68a1d0492a9d9da3616b0301724 Mon Sep 17 00:00:00 2001
From: Damien Miller <djm@mindrot.org>
Date: Wed, 9 Jan 2013 15:57:36 +1100
Subject: [PATCH]    - djm@cvs.openbsd.org 2013/01/03 12:54:49     
 [sftp-server.8 sftp-server.c]      allow specification of an alternate start
 directory for sftp-server(8)      "I like this" markus@

---
 ChangeLog     |  4 ++++
 sftp-server.8 | 16 ++++++++++++++--
 sftp-server.c | 23 ++++++++++++++++++-----
 3 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 67d4884d6..ab80dca45 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -19,6 +19,10 @@
    - djm@cvs.openbsd.org 2013/01/03 12:49:01
      [PROTOCOL]
      fix description of MAC calculation for EtM modes; ok markus@
+   - djm@cvs.openbsd.org 2013/01/03 12:54:49
+     [sftp-server.8 sftp-server.c]
+     allow specification of an alternate start directory for sftp-server(8)
+     "I like this" markus@
 
 20121217
  - (dtucker) [Makefile.in] Add some scaffolding so that the new regress
diff --git a/sftp-server.8 b/sftp-server.8
index bb19c15e1..4d15f1249 100644
--- a/sftp-server.8
+++ b/sftp-server.8
@@ -1,4 +1,4 @@
-.\" $OpenBSD: sftp-server.8,v 1.19 2010/01/09 03:36:00 jmc Exp $
+.\" $OpenBSD: sftp-server.8,v 1.20 2013/01/03 12:54:49 djm Exp $
 .\"
 .\" Copyright (c) 2000 Markus Friedl.  All rights reserved.
 .\"
@@ -22,7 +22,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: January 9 2010 $
+.Dd $Mdocdate: January 3 2013 $
 .Dt SFTP-SERVER 8
 .Os
 .Sh NAME
@@ -31,6 +31,7 @@
 .Sh SYNOPSIS
 .Nm sftp-server
 .Op Fl ehR
+.Op Fl d Ar start_directory
 .Op Fl f Ar log_facility
 .Op Fl l Ar log_level
 .Op Fl u Ar umask
@@ -56,6 +57,17 @@ for more information.
 .Pp
 Valid options are:
 .Bl -tag -width Ds
+.It Fl d
+specifies an alternate starting directory for users.
+The pathname may contain the following tokens that are expanded at runtime:
+%% is replaced by a literal '%',
+%h is replaced by the home directory of the user being authenticated,
+and %u is replaced by the username of that user.
+The default is to use the user's home directory.
+This option is useful in conjunction with the
+.Xr sshd_config 5
+.Cm ChrootDirectory
+option.
 .It Fl e
 Causes
 .Nm
diff --git a/sftp-server.c b/sftp-server.c
index 9d01c7d79..c8858147a 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-server.c,v 1.94 2011/06/17 21:46:16 djm Exp $ */
+/* $OpenBSD: sftp-server.c,v 1.95 2013/01/03 12:54:49 djm Exp $ */
 /*
  * Copyright (c) 2000-2004 Markus Friedl.  All rights reserved.
  *
@@ -1402,7 +1402,7 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 	int in, out, max, ch, skipargs = 0, log_stderr = 0;
 	ssize_t len, olen, set_size;
 	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
-	char *cp, buf[4*4096];
+	char *cp, *homedir = NULL, buf[4*4096];
 	long mask;
 
 	extern char *optarg;
@@ -1411,7 +1411,9 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 	__progname = ssh_get_progname(argv[0]);
 	log_init(__progname, log_level, log_facility, log_stderr);
 
-	while (!skipargs && (ch = getopt(argc, argv, "f:l:u:cehR")) != -1) {
+	pw = pwcopy(user_pw);
+
+	while (!skipargs && (ch = getopt(argc, argv, "d:f:l:u:cehR")) != -1) {
 		switch (ch) {
 		case 'R':
 			readonly = 1;
@@ -1436,6 +1438,12 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 			if (log_facility == SYSLOG_FACILITY_NOT_SET)
 				error("Invalid log facility \"%s\"", optarg);
 			break;
+		case 'd':
+			cp = tilde_expand_filename(optarg, user_pw->pw_uid);
+			homedir = percent_expand(cp, "d", user_pw->pw_dir,
+			    "u", user_pw->pw_name, (char *)NULL);
+			free(cp);
+			break;
 		case 'u':
 			errno = 0;
 			mask = strtol(optarg, &cp, 8);
@@ -1463,8 +1471,6 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 	} else
 		client_addr = xstrdup("UNKNOWN");
 
-	pw = pwcopy(user_pw);
-
 	logit("session opened for local user %s from [%s]",
 	    pw->pw_name, client_addr);
 
@@ -1489,6 +1495,13 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 	rset = (fd_set *)xmalloc(set_size);
 	wset = (fd_set *)xmalloc(set_size);
 
+	if (homedir != NULL) {
+		if (chdir(homedir) != 0) {
+			error("chdir to \"%s\" failed: %s", homedir,
+			    strerror(errno));
+		}
+	}
+
 	for (;;) {
 		memset(rset, 0, set_size);
 		memset(wset, 0, set_size);