[V5] [RFC] Adding a SECURITY policy for GDB

[Andrew Burgess <aburgess@redhat.com>]

In V5:

  - Fixed a couple of minor typos that were pointed out by someone
    off-list.

Any additional feedback would be great.

If there's no feedback, how would people feel about me merging this?  So
long as the content is not objectionable then minor corrections or
additions can be made via the normal patch process in the future.

I know I mentioned adding this text to the GDB manual previously, but I
recall someone objected to that at the time.  Right now I'm thinking to
add this as a standalone document, and possibly merge it into the manual
later in the year.

Thoughts?

Thanks,
Andrew

---

GNU Debugger Security Policy
============================

Introduction
------------

  The GNU Debugger (GDB) is a tool for diagnosing issues "inside"
  another program.  This can be done by controlling the execution of
  the program being debugged and allowing the user to inspect and
  modify the state of the running program.  Or GDB can be used to
  analyse the program or a core file generated from the program
  without needing to execute the program.

  The program being debugged may be local i.e. on the system on which
  GDB runs or remote, on a different system.

Policy Objectives
-----------------

  The objective of this policy is define what the GDB project
  considers a security bug and what is a non-security bug, and how
  bugs can be reported.

  Additionally this policy discusses areas of GDB in which there are
  known bugs, how these might lead to security issues, and how this
  risk can be mitigated.

Scope Of This Policy
--------------------

  This policy covers all currently supported versions of GDB as
  released from the official GDB website and covers gdb, gdbserver, as
  well as gcore and gdb-add-index, which are packaged with each GDB
  release.  The official GDB website can be found here:

    https://sourceware.org/gdb/

  Remote debugging uses GDB to connect to a remote target.  GDB sends
  commands to the remote target which then controls the process being
  debugged.  The GDB project provides one remote target, gdbserver,
  which is included with official GDB releases.  Bugs within gdbserver
  are in scope for this policy.

  Other projects also implement remote targets to which GDB can
  connect.  Any bugs in these remote targets are out of scope for this
  policy and should be reported to the relevant project.  However, any
  bugs in GDB caused by a misbehaving remote target, even when that
  target is not gdbserver, are in scope for this policy.

What Is A Security Bug?
-----------------------

  Any bugs in GDB or gdbserver that result in an unexpected crossing
  of a privilege boundary are considered security bugs.  Some examples
  of crossing a privilege boundary include: being able to execute code
  as an arbitrarily different user, or accessing resources
  (e.g. files, sockets, etc) for which the original user would not
  normally have access.

  Any bugs in GDB that result in execution of the program being
  debugged without the user issuing a GDB command triggering execution
  (either from the GDB command line, a GDB configuration file, or from
  the GDB prompt) are considered security bugs.

  GDB will check for and load multiple configuration files.  When
  initially started GDB can load user- and system-specific
  configuration files, this is done unconditionally as it is assumed
  these files are under control of the user and are always safe to
  load.

  GDB can also load per-project and per-program configuration files,
  this is done when a program to debug is loaded into GDB.  These
  configuration files will only be loaded if the user has given GDB
  permission to load these files.  Any bug in GDB which allows
  per-project or per-program configuration files to be loaded without
  permission having been granted by the user is considered a security
  bug.

  When gdbserver is started, if it is passed a program on its command
  line then that program will be started, but paused before executing
  its first instruction.

  Any bug in gdbserver which results in further execution of the
  program being debugged without GDB first connecting to the target
  and sending a command that is intended to trigger execution is a
  security bug in gdbserver.

  Any bug in GDB or gdbserver that can trigger arbitrary code
  execution without the program being debugged having been executed by
  a user command, is considered a security bug, e.g. if loading a
  program into GDB could trigger arbitrary code execution, then this
  is a security issue.

  The additional tools gcore and gdb-add-index are scripts that wrap
  around GDB.  Any issue in these tools that meet the above
  definitions of a security bug, are considered a security bug.

What Is Not A Security Bug
--------------------------

  In the context of local debugging, when GDB is used to execute a
  program, the program runs with the same privileges as GDB itself.

  Any issues that arise from running an untrusted program outside of a
  secure environment are not security bugs in GDB.  Any issues that
  arise from running an untrusted program through GDB inside a secure
  environment are only security bugs if GDB is required in order to
  trigger the issue.

  It is possible for a program to detect when it is run under GDB and
  to change its behavior so that unwanted behavior may only appear
  when a program is run under GDB.  Any issues that arise due to an
  untrusted program detecting GDB and changing its behaviour are not
  security issues in GDB unless the issue also meet some other
  definition of a security bug.

  In the context of remote debugging, the program being debugged is
  run with the same privileges as gdbserver.  As with GDB in the local
  debugging case, any issues that arise from running an untrusted
  program outside of a secure environment are not security bugs in
  gdbserver.

  The connection between GDB and a remote target is not protected by
  either authentication or encryption.  Connecting to a remote target
  allows for arbitrary code execution on the remote system with the
  same privileges as the remote user, and any resource that the remote
  user can access can be read by GDB, and downloaded to the local
  machine on which GDB is running.  As such, users need to take
  independent measures to secure the connection between GDB and the
  remote target.

  Any issues that arise due to a failure to protect the connection
  between GDB and a remote target are not security bugs in either GDB
  or gdbserver.

Security Realities Of The GDB Project
-------------------------------------

  Within this section, references to GDB should be read as meaning
  GDB, gdbserver, gcore, or gdb-add-index, unless specifically stated
  otherwise.

  The most common use case for GDB is a developer trying to resolve
  issues within a program that they have either written themselves, or
  within a program that they trust not to be malicious.  In this
  situation we would say GDB is being used to debug trusted code.
  There is no greater security risk from running the program to debug
  through GDB than there is running the program directly.  Additional
  process isolation for the GDB process is only needed if additional
  isolation would have been applied anyway when running the program to
  debug.

  In some cases a developer may be given a program from an untrusted
  source and be asked to debug an issue.  In this situation we would
  say GDB is being used to debug untrusted code.  In this case the
  user should take all the precautions when running GDB that they
  would normally take when running an untrusted program outside of
  GDB, e.g. running within a secure, sandboxed environment.

  When using GDB to examine, but not execute, an untrusted program
  (with gdbserver, the program will be started, but paused at the
  first instruction and not run further), there should be no security
  risks, however the GDB maintainers don't currently believe that GDB
  or gdbserver is reliable enough to ensure that there are no security
  risks.

  There are known bugs in GDB related to loading malformed executables
  and parsing the debug information, a consequence of these bugs is
  that a malicious program could trigger undefined behaviour in GDB,
  which could be used to trigger arbitrary code execution.

  Given these risks, the advice of the GDB project is that, when using
  GDB with an untrusted binary, always do so in a secure, sandboxed
  environment.

  As there are already known bugs in GDB relating to undefined
  behaviour triggered from malformed programs, further bugs in this
  area should still be reported, but are unlikely to be given high
  priority.  Bugs in GDB that are triggered by well-formed programs
  should also be reported, and are likely to be treated as higher
  priority as these are more likely to impact normal use of GDB.

  When using GDB and gdbserver to perform remote debug, the connection
  between the two components is by design insecure.  It is up to the
  user to protect this connection, for example, by only starting
  gdbserver within a secure network.

Reporting Non-Security Bugs
---------------------------

  NOTE: All bugs reported in the GDB Bugzilla are public.

  Non-security bugs, as well as any security bugs that pose limited
  risk to users should be reported in GDB's bugzilla system.  Bugs
  reported in this way will be public.  The bugzilla system can be
  found here:

    https://sourceware.org/bugzilla/

Reporting Security Bugs
-----------------------

  In order to report a private security bug that is not immediately
  made public, please contact one of the downstream distributions with
  security teams.  The following teams have volunteered to handle such
  bugs:

     Red Hat: secalert@redhat.com
     SUSE:    security@suse.de

  Please report the bug to just one of these teams.  It will be shared
  with other teams as necessary.

  The team contacted will take care of details such as vulnerability
  rating and CVE assignment (http://cve.mitre.org/about/).  It is
  likely that the team will ask to file a public bug because the issue
  is sufficiently minor and does not warrant keeping details of the
  bug private.