[bug#75810,v5,08/14] daemon: Drop Linux ambient capabilities before executing builder.
Commit Message
* config-daemon.ac: Check for <sys/prctl.h>.
* nix/libstore/build.cc (DerivationGoal::runChild): When ‘useChroot’ is
true, call ‘prctl’ to drop all ambient capabilities.
Change-Id: If34637fc508e5fb6d278167f5df7802fc595284f
---
config-daemon.ac | 2 +-
nix/libstore/build.cc | 9 +++++++++
2 files changed, 10 insertions(+), 1 deletion(-)
@@ -79,7 +79,7 @@ if test "x$guix_build_daemon" = "xyes"; then
dnl Chroot support.
AC_CHECK_FUNCS([chroot unshare])
AC_CHECK_HEADERS([sched.h sys/param.h sys/mount.h sys/syscall.h \
- linux/close_range.h])
+ linux/close_range.h sys/prctl.h])
if test "x$ac_cv_func_chroot" != "xyes"; then
AC_MSG_ERROR(['chroot' function missing, bailing out])
@@ -50,6 +50,9 @@
#if HAVE_SCHED_H
#include <sched.h>
#endif
+#if HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#endif
#define CHROOT_ENABLED HAVE_CHROOT && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_PRIVATE)
@@ -2070,6 +2073,12 @@ void DerivationGoal::runChild()
#if CHROOT_ENABLED
if (useChroot) {
+# if HAVE_SYS_PRCTL_H
+ /* Drop ambient capabilities such as CAP_CHOWN that might have
+ been granted when starting guix-daemon. */
+ prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0);
+# endif
+
if (!fixedOutput) {
/* Initialise the loopback interface. */
AutoCloseFD fd(socket(PF_INET, SOCK_DGRAM, IPPROTO_IP));