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diff -up openssh-6.6p1/configure.ac.chroot-cap openssh-6.6p1/configure.ac
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--- openssh-6.6p1/configure.ac.chroot-cap 2016-07-28 10:08:11.183483309 +0200
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+++ openssh-6.6p1/configure.ac 2016-07-28 10:08:11.273483277 +0200
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@@ -4783,6 +4783,37 @@ if test -n "$conf_lastlog_location"; the
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[Define if you want to specify the path to your lastlog file])
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fi
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+AC_ARG_WITH(libcap-ng,
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+ [ --with-libcap-ng=[auto/yes/no] Add Libcap-ng support [default=auto]],,
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+ with_libcap_ng=auto)
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+
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+dnl libcap-ng detection
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+if test x$with_libcap_ng = xno ; then
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+ have_libcap_ng=no;
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+else
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+ # Start by checking for header file
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+ AC_CHECK_HEADER(cap-ng.h, capng_headers=yes, capng_headers=no)
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+
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+ # See if we have libcap-ng library
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+ AC_CHECK_LIB(cap-ng, capng_clear, CAPNG_LDADD=-lcap-ng,)
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+
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+ # Check results are usable
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+ if test x$with_libcap_ng = xyes -a x$CAPNG_LDADD = x ; then
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+ AC_MSG_ERROR(libcap-ng support was requested and the library was not found)
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+ fi
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+ if test x$CAPNG_LDADD != x -a $capng_headers = no ; then
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+ AC_MSG_ERROR(libcap-ng libraries found but headers are missing)
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+ fi
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+fi
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+AC_MSG_CHECKING(whether to use libcap-ng)
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+if test x$CAPNG_LDADD != x ; then
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+ AC_DEFINE(HAVE_LIBCAP_NG,1,[libcap-ng support])
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+ SSHDLIBS="$SSHDLIBS -lcap-ng"
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+ AC_MSG_RESULT(yes)
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+else
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+ AC_MSG_RESULT(no)
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+fi
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+
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dnl utmp detection
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AC_MSG_CHECKING([if your system defines UTMP_FILE])
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AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
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diff -up openssh-6.6p1/session.c.chroot-cap openssh-6.6p1/session.c
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--- openssh-6.6p1/session.c.chroot-cap 2016-07-28 10:08:11.269483278 +0200
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+++ openssh-6.6p1/session.c 2016-07-28 10:09:10.458455211 +0200
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@@ -95,6 +95,10 @@
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#include "monitor_wrap.h"
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#include "sftp.h"
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+#ifdef HAVE_LIBCAP_NG
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+#include <cap-ng.h>
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+#endif
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+
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#if defined(KRB5) && defined(USE_AFS)
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#include <kafs.h>
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#endif
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@@ -1569,6 +1573,7 @@ void
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do_setusercontext(struct passwd *pw)
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{
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char *chroot_path, *tmp;
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+ int dropped_suid = -1;
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platform_setusercontext(pw);
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@@ -1602,10 +1607,25 @@ do_setusercontext(struct passwd *pw)
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pw->pw_uid);
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chroot_path = percent_expand(tmp, "h", pw->pw_dir,
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"u", pw->pw_name, (char *)NULL);
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+#ifdef HAVE_LIBCAP_NG
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+ /* drop suid soon, retain SYS_CHROOT capability */
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+ capng_clear(CAPNG_SELECT_BOTH);
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+ capng_update(CAPNG_ADD, CAPNG_EFFECTIVE|CAPNG_PERMITTED, CAP_SYS_CHROOT);
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+ if (pw->pw_uid != 0 &&
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+ (dropped_suid = capng_change_id(pw->pw_uid, pw->pw_gid, CAPNG_INIT_SUPP_GRP)) != 0)
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+ logit("capng_change_id() = %d (failure): Try to drop UID later", dropped_suid);
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+#endif
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#ifdef WITH_SELINUX
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sshd_selinux_copy_context();
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#endif
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safely_chroot(chroot_path, pw->pw_uid);
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+#ifdef HAVE_LIBCAP_NG
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+ /* Drop chroot capability. Already used */
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+ if (dropped_suid == 0) {
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+ capng_clear(CAPNG_SELECT_BOTH);
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+ capng_apply(CAPNG_SELECT_BOTH);
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+ }
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+#endif
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free(tmp);
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free(chroot_path);
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/* Make sure we don't attempt to chroot again */
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@@ -1629,8 +1648,9 @@ do_setusercontext(struct passwd *pw)
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fatal("set_id(%s) Failed", pw->pw_name);
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}
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# endif /* USE_LIBIAF */
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- /* Permanently switch to the desired uid. */
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- permanently_set_uid(pw);
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+ /* Permanently switch to the desired uid if not yet done. */
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+ if (dropped_suid != 0)
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+ permanently_set_uid(pw);
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#endif
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#ifdef WITH_SELINUX
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