€•‡?      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ./translations/zh_CN/userspace-api/no_new_privs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ./translations/zh_TW/userspace-api/no_new_privs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ./translations/it_IT/userspace-api/no_new_privs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ./translations/ja_JP/userspace-api/no_new_privs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ./translations/ko_KR/userspace-api/no_new_privs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ./translations/sp_SP/userspace-api/no_new_privs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒNo New Privileges Flag”h]”hŒNo New Privileges Flag”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒH/var/lib/git/docbuild/linux/Documentation/userspace-api/no_new_privs.rst”h KubhŒ	paragraph”“”)”}”(hXs  The execve system call can grant a newly-started program privileges that
its parent did not have.  The most obvious examples are setuid/setgid
programs and file capabilities.  To prevent the parent program from
gaining these privileges as well, the kernel and user code must be
careful to prevent the parent from doing anything that could subvert the
child.  For example:”h]”hXs  The execve system call can grant a newly-started program privileges that
its parent did not have.  The most obvious examples are setuid/setgid
programs and file capabilities.  To prevent the parent program from
gaining these privileges as well, the kernel and user code must be
careful to prevent the parent from doing anything that could subvert the
child.  For example:”…””}”(hh¹hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubhŒblock_quote”“”)”}”(hX:  - The dynamic loader handles ``LD_*`` environment variables differently if
  a program is setuid.

- chroot is disallowed to unprivileged processes, since it would allow
  ``/etc/passwd`` to be replaced from the point of view of a process that
  inherited chroot.

- The exec code has special handling for ptrace.
”h]”hŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒ^The dynamic loader handles ``LD_*`` environment variables differently if
a program is setuid.
”h]”h¸)”}”(hŒ]The dynamic loader handles ``LD_*`` environment variables differently if
a program is setuid.”h]”(hŒThe dynamic loader handles ”…””}”(hhØhžhhŸNh NubhŒliteral”“”)”}”(hŒ``LD_*``”h]”hŒLD_*”…””}”(hhâhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhhØubhŒ: environment variables differently if
a program is setuid.”…””}”(hhØhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÔubah}”(h]”h ]”h"]”h$]”h&]”uh1hÒhhÏubhÓ)”}”(hŒŸchroot is disallowed to unprivileged processes, since it would allow
``/etc/passwd`` to be replaced from the point of view of a process that
inherited chroot.
”h]”h¸)”}”(hŒžchroot is disallowed to unprivileged processes, since it would allow
``/etc/passwd`` to be replaced from the point of view of a process that
inherited chroot.”h]”(hŒEchroot is disallowed to unprivileged processes, since it would allow
”…””}”(hj  hžhhŸNh Nubhá)”}”(hŒ``/etc/passwd``”h]”hŒ/etc/passwd”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj  ubhŒJ to be replaced from the point of view of a process that
inherited chroot.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj   ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÒhhÏubhÓ)”}”(hŒ/The exec code has special handling for ptrace.
”h]”h¸)”}”(hŒ.The exec code has special handling for ptrace.”h]”hŒ.The exec code has special handling for ptrace.”…””}”(hj.  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj*  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÒhhÏubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1hÍhŸh¶h KhhÉubah}”(h]”h ]”h"]”h$]”h&]”uh1hÇhŸh¶h Khh£hžhubh¸)”}”(hX•  These are all ad-hoc fixes.  The ``no_new_privs`` bit (since Linux 3.5) is a
new, generic mechanism to make it safe for a process to modify its
execution environment in a manner that persists across execve.  Any task
can set ``no_new_privs``.  Once the bit is set, it is inherited across fork,
clone, and execve and cannot be unset.  With ``no_new_privs`` set, ``execve()``
promises not to grant the privilege to do anything that could not have
been done without the execve call.  For example, the setuid and setgid
bits will no longer change the uid or gid; file capabilities will not
add to the permitted set, and LSMs will not relax constraints after
execve.”h]”(hŒ!These are all ad-hoc fixes.  The ”…””}”(hjP  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hjX  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjP  ubhŒ° bit (since Linux 3.5) is a
new, generic mechanism to make it safe for a process to modify its
execution environment in a manner that persists across execve.  Any task
can set ”…””}”(hjP  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hjj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjP  ubhŒb.  Once the bit is set, it is inherited across fork,
clone, and execve and cannot be unset.  With ”…””}”(hjP  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj|  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjP  ubhŒ set, ”…””}”(hjP  hžhhŸNh Nubhá)”}”(hŒ``execve()``”h]”hŒexecve()”…””}”(hjŽ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjP  ubhX   
promises not to grant the privilege to do anything that could not have
been done without the execve call.  For example, the setuid and setgid
bits will no longer change the uid or gid; file capabilities will not
add to the permitted set, and LSMs will not relax constraints after
execve.”…””}”(hjP  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒTo set ``no_new_privs``, use::”h]”(hŒTo set ”…””}”(hj¦  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj®  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj¦  ubhŒ, use:”…””}”(hj¦  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K hh£hžhubhŒliteral_block”“”)”}”(hŒ'prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);”h]”hŒ'prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);”…””}”hjÈ  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1jÆ  hŸh¶h K"hh£hžhubh¸)”}”(hŒöBe careful, though: LSMs might also not tighten constraints on exec
in ``no_new_privs`` mode.  (This means that setting up a general-purpose
service launcher to set ``no_new_privs`` before execing daemons may
interfere with LSM-based sandboxing.)”h]”(hŒGBe careful, though: LSMs might also not tighten constraints on exec
in ”…””}”(hjØ  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hjà  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjØ  ubhŒN mode.  (This means that setting up a general-purpose
service launcher to set ”…””}”(hjØ  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hjò  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjØ  ubhŒA before execing daemons may
interfere with LSM-based sandboxing.)”…””}”(hjØ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K$hh£hžhubh¸)”}”(hŒÀNote that ``no_new_privs`` does not prevent privilege changes that do not
involve ``execve()``.  An appropriately privileged task can still call
``setuid(2)`` and receive SCM_RIGHTS datagrams.”h]”(hŒ
Note that ”…””}”(hj
  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj
  ubhŒ8 does not prevent privilege changes that do not
involve ”…””}”(hj
  hžhhŸNh Nubhá)”}”(hŒ``execve()``”h]”hŒexecve()”…””}”(hj$  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj
  ubhŒ3.  An appropriately privileged task can still call
”…””}”(hj
  hžhhŸNh Nubhá)”}”(hŒ``setuid(2)``”h]”hŒ	setuid(2)”…””}”(hj6  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj
  ubhŒ" and receive SCM_RIGHTS datagrams.”…””}”(hj
  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K)hh£hžhubh¸)”}”(hŒ9There are two main use cases for ``no_new_privs`` so far:”h]”(hŒ!There are two main use cases for ”…””}”(hjN  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hjV  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjN  ubhŒ so far:”…””}”(hjN  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K-hh£hžhubhÈ)”}”(hXh  - Filters installed for the seccomp mode 2 sandbox persist across
  execve and can change the behavior of newly-executed programs.
  Unprivileged users are therefore only allowed to install such filters
  if ``no_new_privs`` is set.

- By itself, ``no_new_privs`` can be used to reduce the attack surface
  available to an unprivileged user.  If everything running with a
  given uid has ``no_new_privs`` set, then that uid will be unable to
  escalate its privileges by directly attacking setuid, setgid, and
  fcap-using binaries; it will need to compromise something without the
  ``no_new_privs`` bit set first.
”h]”hÎ)”}”(hhh]”(hÓ)”}”(hŒáFilters installed for the seccomp mode 2 sandbox persist across
execve and can change the behavior of newly-executed programs.
Unprivileged users are therefore only allowed to install such filters
if ``no_new_privs`` is set.
”h]”h¸)”}”(hŒàFilters installed for the seccomp mode 2 sandbox persist across
execve and can change the behavior of newly-executed programs.
Unprivileged users are therefore only allowed to install such filters
if ``no_new_privs`` is set.”h]”(hŒÈFilters installed for the seccomp mode 2 sandbox persist across
execve and can change the behavior of newly-executed programs.
Unprivileged users are therefore only allowed to install such filters
if ”…””}”(hjy  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjy  ubhŒ is set.”…””}”(hjy  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K/hju  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÒhjr  ubhÓ)”}”(hXr  By itself, ``no_new_privs`` can be used to reduce the attack surface
available to an unprivileged user.  If everything running with a
given uid has ``no_new_privs`` set, then that uid will be unable to
escalate its privileges by directly attacking setuid, setgid, and
fcap-using binaries; it will need to compromise something without the
``no_new_privs`` bit set first.
”h]”h¸)”}”(hXq  By itself, ``no_new_privs`` can be used to reduce the attack surface
available to an unprivileged user.  If everything running with a
given uid has ``no_new_privs`` set, then that uid will be unable to
escalate its privileges by directly attacking setuid, setgid, and
fcap-using binaries; it will need to compromise something without the
``no_new_privs`` bit set first.”h]”(hŒBy itself, ”…””}”(hj£  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj«  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj£  ubhŒy can be used to reduce the attack surface
available to an unprivileged user.  If everything running with a
given uid has ”…””}”(hj£  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj½  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj£  ubhŒ® set, then that uid will be unable to
escalate its privileges by directly attacking setuid, setgid, and
fcap-using binaries; it will need to compromise something without the
”…””}”(hj£  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hjÏ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhj£  ubhŒ bit set first.”…””}”(hj£  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K4hjŸ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÒhjr  ubeh}”(h]”h ]”h"]”h$]”h&]”jH  jI  uh1hÍhŸh¶h K/hjn  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÇhŸh¶h K/hh£hžhubh¸)”}”(hXI  In the future, other potentially dangerous kernel features could become
available to unprivileged tasks if ``no_new_privs`` is set.  In principle,
several options to ``unshare(2)`` and ``clone(2)`` would be safe when
``no_new_privs`` is set, and ``no_new_privs`` + ``chroot`` is considerable less
dangerous than chroot by itself.”h]”(hŒkIn the future, other potentially dangerous kernel features could become
available to unprivileged tasks if ”…””}”(hjù  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjù  ubhŒ+ is set.  In principle,
several options to ”…””}”(hjù  hžhhŸNh Nubhá)”}”(hŒ``unshare(2)``”h]”hŒ
unshare(2)”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjù  ubhŒ and ”…””}”(hjù  hžhhŸNh Nubhá)”}”(hŒ``clone(2)``”h]”hŒclone(2)”…””}”(hj%  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjù  ubhŒ would be safe when
”…””}”(hjù  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hj7  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjù  ubhŒ is set, and ”…””}”(hjù  hžhhŸNh Nubhá)”}”(hŒ``no_new_privs``”h]”hŒno_new_privs”…””}”(hjI  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjù  ubhŒ + ”…””}”(hjù  hžhhŸNh Nubhá)”}”(hŒ
``chroot``”h]”hŒchroot”…””}”(hj[  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhjù  ubhŒ6 is considerable less
dangerous than chroot by itself.”…””}”(hjù  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K;hh£hžhubeh}”(h]”Œno-new-privileges-flag”ah ]”h"]”Œno new privileges flag”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
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