New APIs: Implement Linux filesystem capabilities.

This adds the following new APIs:
 - cap_get_file
 - cap_set_file

1 files changed, 131 insertions, 0 deletions

diff --git a/daemon/cap.c b/daemon/cap.c
new file mode 100644
index 00000000..3572704c
--- /dev/null
+++ b/daemon/cap.c
@@ -0,0 +1,131 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2012 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <limits.h>
+#include <unistd.h>
+
+#include "guestfs_protocol.h"
+#include "daemon.h"
+#include "actions.h"
+#include "optgroups.h"
+
+#if defined(HAVE_CAP)
+
+#include <sys/capability.h>
+
+int
+optgroup_linuxcaps_available (void)
+{
+  return 1;
+}
+
+char *
+do_cap_get_file (const char *path)
+{
+  cap_t cap;
+  char *r, *ret;
+
+  CHROOT_IN;
+  cap = cap_get_file (path);
+  CHROOT_OUT;
+
+  if (cap == NULL) {
+    reply_with_perror ("%s", path);
+    return NULL;
+  }
+
+  r = cap_to_text (cap, NULL);
+  if (r == NULL) {
+    reply_with_perror ("cap_to_text");
+    cap_free (cap);
+    return NULL;
+  }
+
+  cap_free (cap);
+
+  /* 'r' is not an ordinary pointer that can be freed with free(3)!
+   * In the current implementation of libcap, if you try to do that it
+   * will segfault.  We have to duplicate this into an ordinary
+   * buffer, then call cap_free (r).
+   */
+  ret = strdup (r);
+  if (ret == NULL) {
+    reply_with_perror ("strdup");
+    cap_free (r);
+    return NULL;
+  }
+  cap_free (r);
+
+  return ret;                   /* caller frees */
+}
+
+int
+do_cap_set_file (const char *path, const char *capstr)
+{
+  cap_t cap;
+  int r;
+
+  cap = cap_from_text (capstr);
+  if (cap == NULL) {
+    reply_with_perror ("could not parse cap string: %s: cap_from_text", capstr);
+    return -1;
+  }
+
+  CHROOT_IN;
+  r = cap_set_file (path, cap);
+  CHROOT_OUT;
+
+  if (r == -1) {
+    reply_with_perror ("%s", path);
+    cap_free (cap);
+    return -1;
+  }
+
+  cap_free (cap);
+
+  return 0;
+}
+
+#else /* no libcap */
+
+/* Note that the wrapper code (daemon/stubs.c) ensures that the
+ * functions below are never called because
+ * optgroup_linuxcaps_available returns false.
+ */
+int
+optgroup_linuxcaps_available (void)
+{
+  return 0;
+}
+
+char *
+do_cap_get_file (const char *path)
+{
+  abort ();
+}
+
+int
+do_cap_set_file (const char *path, const char *cap)
+{
+  abort ();
+}
+
+#endif /* no libcap */