* add chroot() support on Linux

git-svn-id: file:///home/lennart/svn/public/avahi/trunk@907 941a03a8-eaeb-0310-b9a0-b1bbd8fe43fe

1 files changed, 116 insertions, 0 deletions

diff --git a/avahi-daemon/caps.c b/avahi-daemon/caps.c
new file mode 100644
index 0000000..2d0f39a
--- /dev/null
+++ b/avahi-daemon/caps.c
@@ -0,0 +1,116 @@
+/* $Id$ */
+
+/***
+  This file is part of avahi.
+ 
+  avahi is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as
+  published by the Free Software Foundation; either version 2.1 of the
+  License, or (at your option) any later version.
+ 
+  avahi is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+  or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
+  Public License for more details.
+ 
+  You should have received a copy of the GNU Lesser General Public
+  License along with avahi; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+  USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/capability.h>
+#include <sys/prctl.h>
+
+#include <avahi-core/log.h>
+
+#include "caps.h"
+
+int avahi_caps_reduce(void) {
+    int ret = 0;
+    cap_t caps;
+    static cap_value_t cap_values[] = { CAP_SYS_CHROOT, CAP_SETUID, CAP_SETGID };
+    
+    /* Let's reduce our caps to the minimum set and tell Linux to keep
+     * them accross setuid(). This is called before we droppped
+     * priviliges. */
+    
+    caps = cap_init();
+    assert(caps);
+    cap_clear(caps);
+
+    cap_set_flag(caps, CAP_EFFECTIVE, 3, cap_values, CAP_SET);
+    cap_set_flag(caps, CAP_PERMITTED, 3, cap_values, CAP_SET);
+    
+    if (cap_set_proc(caps) < 0) {
+        avahi_log_error("cap_set_proc() failed: %s", strerror(errno));
+        ret = -1;
+    }
+    cap_free(caps);
+
+    /* Retain capabilities accros setuid() */
+    if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0) {
+        avahi_log_error("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno));
+        ret = -1;
+    }
+
+    return ret;
+}
+
+int avahi_caps_reduce2(void) {
+    int ret = 0;
+    cap_t caps;
+    static cap_value_t cap_values[] = { CAP_SYS_CHROOT };
+
+    /* Reduce our caps to the bare minimum and tell Linux not to keep
+     * them across setuid(). This is called after we dropped
+     * privilige. */
+    
+    /* No longer retain caps across setuid() */
+    if (prctl(PR_SET_KEEPCAPS, 0, 0, 0, 0) < 0) {
+        avahi_log_error("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno));
+        ret = -1;
+    }
+
+    caps = cap_init();
+    assert(caps);
+    cap_clear(caps);
+
+    /* setuid() zeroed our effective caps, let's get them back */
+    cap_set_flag(caps, CAP_EFFECTIVE, 1, cap_values, CAP_SET);
+    cap_set_flag(caps, CAP_PERMITTED, 1, cap_values, CAP_SET);
+
+    if (cap_set_proc(caps) < 0) {
+        avahi_log_error("cap_set_proc() failed: %s", strerror(errno));
+        ret = -1;
+    }
+    cap_free(caps);
+
+    return ret;
+}
+
+int avahi_caps_drop_all(void) {
+    cap_t caps;
+    int ret = 0;
+
+    /* Drop all capabilities and turn ourselves into a normal user process */
+
+    caps = cap_init();
+    assert(caps);
+    cap_clear(caps);
+    
+    if (cap_set_proc(caps) < 0) {
+        avahi_log_error("cap_set_proc() failed: %s", strerror(errno));
+        ret = -1;
+    }
+    cap_free(caps);
+    
+    return ret;
+}