Initial commit

5 files changed, 1400 insertions, 0 deletions

diff --git a/GPL-3 b/GPL-3
new file mode 100644
index 0000000..94a9ed0
--- /dev/null
+++ b/GPL-3
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
+free programs, and that you know you can do these things.
+
+  To protect your rights, we need to prevent others from denying you
+these rights or asking you to surrender the rights.  Therefore, you have
+certain responsibilities if you distribute copies of the software, or if
+you modify it: responsibilities to respect the freedom of others.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must pass on to the recipients the same
+freedoms that you received.  You must make sure that they, too, receive
+or can get the source code.  And you must show them these terms so they
+know their rights.
+
+  Developers that use the GNU GPL protect your rights with two steps:
+(1) assert copyright on the software, and (2) offer you this License
+giving you legal permission to copy, distribute and/or modify it.
+
+  For the developers' and authors' protection, the GPL clearly explains
+that there is no warranty for this free software.  For both users' and
+authors' sake, the GPL requires that modified versions be marked as
+changed, so that their problems will not be attributed erroneously to
+authors of previous versions.
+
+  Some devices are designed to deny users access to install or run
+modified versions of the software inside them, although the manufacturer
+can do so.  This is fundamentally incompatible with the aim of
+protecting users' freedom to change the software.  The systematic
+pattern of such abuse occurs in the area of products for individuals to
+use, which is precisely where it is most unacceptable.  Therefore, we
+have designed this version of the GPL to prohibit the practice for those
+products.  If such problems arise substantially in other domains, we
+stand ready to extend this provision to those domains in future versions
+of the GPL, as needed to protect the freedom of users.
+
+  Finally, every program is threatened constantly by software patents.
+States should not allow patents to restrict development and use of
+software on general-purpose computers, but in those that do, we wish to
+avoid the special danger that patents applied to a free program could
+make it effectively proprietary.  To prevent this, the GPL assures that
+patents cannot be used to render the program non-free.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                       TERMS AND CONDITIONS
+
+  0. Definitions.
+
+  "This License" refers to version 3 of the GNU General Public License.
+
+  "Copyright" also means copyright-like laws that apply to other kinds of
+works, such as semiconductor masks.
+
+  "The Program" refers to any copyrightable work licensed under this
+License.  Each licensee is addressed as "you".  "Licensees" and
+"recipients" may be individuals or organizations.
+
+  To "modify" a work means to copy from or adapt all or part of the work
+in a fashion requiring copyright permission, other than the making of an
+exact copy.  The resulting work is called a "modified version" of the
+earlier work or a work "based on" the earlier work.
+
+  A "covered work" means either the unmodified Program or a work based
+on the Program.
+
+  To "propagate" a work means to do anything with it that, without
+permission, would make you directly or secondarily liable for
+infringement under applicable copyright law, except executing it on a
+computer or modifying a private copy.  Propagation includes copying,
+distribution (with or without modification), making available to the
+public, and in some countries other activities as well.
+
+  To "convey" a work means any kind of propagation that enables other
+parties to make or receive copies.  Mere interaction with a user through
+a computer network, with no transfer of a copy, is not conveying.
+
+  An interactive user interface displays "Appropriate Legal Notices"
+to the extent that it includes a convenient and prominently visible
+feature that (1) displays an appropriate copyright notice, and (2)
+tells the user that there is no warranty for the work (except to the
+extent that warranties are provided), that licensees may convey the
+work under this License, and how to view a copy of this License.  If
+the interface presents a list of user commands or options, such as a
+menu, a prominent item in the list meets this criterion.
+
+  1. Source Code.
+
+  The "source code" for a work means the preferred form of the work
+for making modifications to it.  "Object code" means any non-source
+form of a work.
+
+  A "Standard Interface" means an interface that either is an official
+standard defined by a recognized standards body, or, in the case of
+interfaces specified for a particular programming language, one that
+is widely used among developers working in that language.
+
+  The "System Libraries" of an executable work include anything, other
+than the work as a whole, that (a) is included in the normal form of
+packaging a Major Component, but which is not part of that Major
+Component, and (b) serves only to enable use of the work with that
+Major Component, or to implement a Standard Interface for which an
+implementation is available to the public in source code form.  A
+"Major Component", in this context, means a major essential component
+(kernel, window system, and so on) of the specific operating system
+(if any) on which the executable work runs, or a compiler used to
+produce the work, or an object code interpreter used to run it.
+
+  The "Corresponding Source" for a work in object code form means all
+the source code needed to generate, install, and (for an executable
+work) run the object code and to modify the work, including scripts to
+control those activities.  However, it does not include the work's
+System Libraries, or general-purpose tools or generally available free
+programs which are used unmodified in performing those activities but
+which are not part of the work.  For example, Corresponding Source
+includes interface definition files associated with source files for
+the work, and the source code for shared libraries and dynamically
+linked subprograms that the work is specifically designed to require,
+such as by intimate data communication or control flow between those
+subprograms and other parts of the work.
+
+  The Corresponding Source need not include anything that users
+can regenerate automatically from other parts of the Corresponding
+Source.
+
+  The Corresponding Source for a work in source code form is that
+same work.
+
+  2. Basic Permissions.
+
+  All rights granted under this License are granted for the term of
+copyright on the Program, and are irrevocable provided the stated
+conditions are met.  This License explicitly affirms your unlimited
+permission to run the unmodified Program.  The output from running a
+covered work is covered by this License only if the output, given its
+content, constitutes a covered work.  This License acknowledges your
+rights of fair use or other equivalent, as provided by copyright law.
+
+  You may make, run and propagate covered works that you do not
+convey, without conditions so long as your license otherwise remains
+in force.  You may convey covered works to others for the sole purpose
+of having them make modifications exclusively for you, or provide you
+with facilities for running those works, provided that you comply with
+the terms of this License in conveying all material for which you do
+not control copyright.  Those thus making or running the covered works
+for you must do so exclusively on your behalf, under your direction
+and control, on terms that prohibit them from making any copies of
+your copyrighted material outside their relationship with you.
+
+  Conveying under any other circumstances is permitted solely under
+the conditions stated below.  Sublicensing is not allowed; section 10
+makes it unnecessary.
+
+  3. Protecting Users' Legal Rights From Anti-Circumvention Law.
+
+  No covered work shall be deemed part of an effective technological
+measure under any applicable law fulfilling obligations under article
+11 of the WIPO copyright treaty adopted on 20 December 1996, or
+similar laws prohibiting or restricting circumvention of such
+measures.
+
+  When you convey a covered work, you waive any legal power to forbid
+circumvention of technological measures to the extent such circumvention
+is effected by exercising rights under this License with respect to
+the covered work, and you disclaim any intention to limit operation or
+modification of the work as a means of enforcing, against the work's
+users, your or third parties' legal rights to forbid circumvention of
+technological measures.
+
+  4. Conveying Verbatim Copies.
+
+  You may convey verbatim copies of the Program's source code as you
+receive it, in any medium, provided that you conspicuously and
+appropriately publish on each copy an appropriate copyright notice;
+keep intact all notices stating that this License and any
+non-permissive terms added in accord with section 7 apply to the code;
+keep intact all notices of the absence of any warranty; and give all
+recipients a copy of this License along with the Program.
+
+  You may charge any price or no price for each copy that you convey,
+and you may offer support or warranty protection for a fee.
+
+  5. Conveying Modified Source Versions.
+
+  You may convey a work based on the Program, or the modifications to
+produce it from the Program, in the form of source code under the
+terms of section 4, provided that you also meet all of these conditions:
+
+    a) The work must carry prominent notices stating that you modified
+    it, and giving a relevant date.
+
+    b) The work must carry prominent notices stating that it is
+    released under this License and any conditions added under section
+    7.  This requirement modifies the requirement in section 4 to
+    "keep intact all notices".
+
+    c) You must license the entire work, as a whole, under this
+    License to anyone who comes into possession of a copy.  This
+    License will therefore apply, along with any applicable section 7
+    additional terms, to the whole of the work, and all its parts,
+    regardless of how they are packaged.  This License gives no
+    permission to license the work in any other way, but it does not
+    invalidate such permission if you have separately received it.
+
+    d) If the work has interactive user interfaces, each must display
+    Appropriate Legal Notices; however, if the Program has interactive
+    interfaces that do not display Appropriate Legal Notices, your
+    work need not make them do so.
+
+  A compilation of a covered work with other separate and independent
+works, which are not by their nature extensions of the covered work,
+and which are not combined with it such as to form a larger program,
+in or on a volume of a storage or distribution medium, is called an
+"aggregate" if the compilation and its resulting copyright are not
+used to limit the access or legal rights of the compilation's users
+beyond what the individual works permit.  Inclusion of a covered work
+in an aggregate does not cause this License to apply to the other
+parts of the aggregate.
+
+  6. Conveying Non-Source Forms.
+
+  You may convey a covered work in object code form under the terms
+of sections 4 and 5, provided that you also convey the
+machine-readable Corresponding Source under the terms of this License,
+in one of these ways:
+
+    a) Convey the object code in, or embodied in, a physical product
+    (including a physical distribution medium), accompanied by the
+    Corresponding Source fixed on a durable physical medium
+    customarily used for software interchange.
+
+    b) Convey the object code in, or embodied in, a physical product
+    (including a physical distribution medium), accompanied by a
+    written offer, valid for at least three years and valid for as
+    long as you offer spare parts or customer support for that product
+    model, to give anyone who possesses the object code either (1) a
+    copy of the Corresponding Source for all the software in the
+    product that is covered by this License, on a durable physical
+    medium customarily used for software interchange, for a price no
+    more than your reasonable cost of physically performing this
+    conveying of source, or (2) access to copy the
+    Corresponding Source from a network server at no charge.
+
+    c) Convey individual copies of the object code with a copy of the
+    written offer to provide the Corresponding Source.  This
+    alternative is allowed only occasionally and noncommercially, and
+    only if you received the object code with such an offer, in accord
+    with subsection 6b.
+
+    d) Convey the object code by offering access from a designated
+    place (gratis or for a charge), and offer equivalent access to the
+    Corresponding Source in the same way through the same place at no
+    further charge.  You need not require recipients to copy the
+    Corresponding Source along with the object code.  If the place to
+    copy the object code is a network server, the Corresponding Source
+    may be on a different server (operated by you or a third party)
+    that supports equivalent copying facilities, provided you maintain
+    clear directions next to the object code saying where to find the
+    Corresponding Source.  Regardless of what server hosts the
+    Corresponding Source, you remain obligated to ensure that it is
+    available for as long as needed to satisfy these requirements.
+
+    e) Convey the object code using peer-to-peer transmission, provided
+    you inform other peers where the object code and Corresponding
+    Source of the work are being offered to the general public at no
+    charge under subsection 6d.
+
+  A separable portion of the object code, whose source code is excluded
+from the Corresponding Source as a System Library, need not be
+included in conveying the object code work.
+
+  A "User Product" is either (1) a "consumer product", which means any
+tangible personal property which is normally used for personal, family,
+or household purposes, or (2) anything designed or sold for incorporation
+into a dwelling.  In determining whether a product is a consumer product,
+doubtful cases shall be resolved in favor of coverage.  For a particular
+product received by a particular user, "normally used" refers to a
+typical or common use of that class of product, regardless of the status
+of the particular user or of the way in which the particular user
+actually uses, or expects or is expected to use, the product.  A product
+is a consumer product regardless of whether the product has substantial
+commercial, industrial or non-consumer uses, unless such uses represent
+the only significant mode of use of the product.
+
+  "Installation Information" for a User Product means any methods,
+procedures, authorization keys, or other information required to install
+and execute modified versions of a covered work in that User Product from
+a modified version of its Corresponding Source.  The information must
+suffice to ensure that the continued functioning of the modified object
+code is in no case prevented or interfered with solely because
+modification has been made.
+
+  If you convey an object code work under this section in, or with, or
+specifically for use in, a User Product, and the conveying occurs as
+part of a transaction in which the right of possession and use of the
+User Product is transferred to the recipient in perpetuity or for a
+fixed term (regardless of how the transaction is characterized), the
+Corresponding Source conveyed under this section must be accompanied
+by the Installation Information.  But this requirement does not apply
+if neither you nor any third party retains the ability to install
+modified object code on the User Product (for example, the work has
+been installed in ROM).
+
+  The requirement to provide Installation Information does not include a
+requirement to continue to provide support service, warranty, or updates
+for a work that has been modified or installed by the recipient, or for
+the User Product in which it has been modified or installed.  Access to a
+network may be denied when the modification itself materially and
+adversely affects the operation of the network or violates the rules and
+protocols for communication across the network.
+
+  Corresponding Source conveyed, and Installation Information provided,
+in accord with this section must be in a format that is publicly
+documented (and with an implementation available to the public in
+source code form), and must require no special password or key for
+unpacking, reading or copying.
+
+  7. Additional Terms.
+
+  "Additional permissions" are terms that supplement the terms of this
+License by making exceptions from one or more of its conditions.
+Additional permissions that are applicable to the entire Program shall
+be treated as though they were included in this License, to the extent
+that they are valid under applicable law.  If additional permissions
+apply only to part of the Program, that part may be used separately
+under those permissions, but the entire Program remains governed by
+this License without regard to the additional permissions.
+
+  When you convey a copy of a covered work, you may at your option
+remove any additional permissions from that copy, or from any part of
+it.  (Additional permissions may be written to require their own
+removal in certain cases when you modify the work.)  You may place
+additional permissions on material, added by you to a covered work,
+for which you have or can give appropriate copyright permission.
+
+  Notwithstanding any other provision of this License, for material you
+add to a covered work, you may (if authorized by the copyright holders of
+that material) supplement the terms of this License with terms:
+
+    a) Disclaiming warranty or limiting liability differently from the
+    terms of sections 15 and 16 of this License; or
+
+    b) Requiring preservation of specified reasonable legal notices or
+    author attributions in that material or in the Appropriate Legal
+    Notices displayed by works containing it; or
+
+    c) Prohibiting misrepresentation of the origin of that material, or
+    requiring that modified versions of such material be marked in
+    reasonable ways as different from the original version; or
+
+    d) Limiting the use for publicity purposes of names of licensors or
+    authors of the material; or
+
+    e) Declining to grant rights under trademark law for use of some
+    trade names, trademarks, or service marks; or
+
+    f) Requiring indemnification of licensors and authors of that
+    material by anyone who conveys the material (or modified versions of
+    it) with contractual assumptions of liability to the recipient, for
+    any liability that these contractual assumptions directly impose on
+    those licensors and authors.
+
+  All other non-permissive additional terms are considered "further
+restrictions" within the meaning of section 10.  If the Program as you
+received it, or any part of it, contains a notice stating that it is
+governed by this License along with a term that is a further
+restriction, you may remove that term.  If a license document contains
+a further restriction but permits relicensing or conveying under this
+License, you may add to a covered work material governed by the terms
+of that license document, provided that the further restriction does
+not survive such relicensing or conveying.
+
+  If you add terms to a covered work in accord with this section, you
+must place, in the relevant source files, a statement of the
+additional terms that apply to those files, or a notice indicating
+where to find the applicable terms.
+
+  Additional terms, permissive or non-permissive, may be stated in the
+form of a separately written license, or stated as exceptions;
+the above requirements apply either way.
+
+  8. Termination.
+
+  You may not propagate or modify a covered work except as expressly
+provided under this License.  Any attempt otherwise to propagate or
+modify it is void, and will automatically terminate your rights under
+this License (including any patent licenses granted under the third
+paragraph of section 11).
+
+  However, if you cease all violation of this License, then your
+license from a particular copyright holder is reinstated (a)
+provisionally, unless and until the copyright holder explicitly and
+finally terminates your license, and (b) permanently, if the copyright
+holder fails to notify you of the violation by some reasonable means
+prior to 60 days after the cessation.
+
+  Moreover, your license from a particular copyright holder is
+reinstated permanently if the copyright holder notifies you of the
+violation by some reasonable means, this is the first time you have
+received notice of violation of this License (for any work) from that
+copyright holder, and you cure the violation prior to 30 days after
+your receipt of the notice.
+
+  Termination of your rights under this section does not terminate the
+licenses of parties who have received copies or rights from you under
+this License.  If your rights have been terminated and not permanently
+reinstated, you do not qualify to receive new licenses for the same
+material under section 10.
+
+  9. Acceptance Not Required for Having Copies.
+
+  You are not required to accept this License in order to receive or
+run a copy of the Program.  Ancillary propagation of a covered work
+occurring solely as a consequence of using peer-to-peer transmission
+to receive a copy likewise does not require acceptance.  However,
+nothing other than this License grants you permission to propagate or
+modify any covered work.  These actions infringe copyright if you do
+not accept this License.  Therefore, by modifying or propagating a
+covered work, you indicate your acceptance of this License to do so.
+
+  10. Automatic Licensing of Downstream Recipients.
+
+  Each time you convey a covered work, the recipient automatically
+receives a license from the original licensors, to run, modify and
+propagate that work, subject to this License.  You are not responsible
+for enforcing compliance by third parties with this License.
+
+  An "entity transaction" is a transaction transferring control of an
+organization, or substantially all assets of one, or subdividing an
+organization, or merging organizations.  If propagation of a covered
+work results from an entity transaction, each party to that
+transaction who receives a copy of the work also receives whatever
+licenses to the work the party's predecessor in interest had or could
+give under the previous paragraph, plus a right to possession of the
+Corresponding Source of the work from the predecessor in interest, if
+the predecessor has it or can get it with reasonable efforts.
+
+  You may not impose any further restrictions on the exercise of the
+rights granted or affirmed under this License.  For example, you may
+not impose a license fee, royalty, or other charge for exercise of
+rights granted under this License, and you may not initiate litigation
+(including a cross-claim or counterclaim in a lawsuit) alleging that
+any patent claim is infringed by making, using, selling, offering for
+sale, or importing the Program or any portion of it.
+
+  11. Patents.
+
+  A "contributor" is a copyright holder who authorizes use under this
+License of the Program or a work on which the Program is based.  The
+work thus licensed is called the contributor's "contributor version".
+
+  A contributor's "essential patent claims" are all patent claims
+owned or controlled by the contributor, whether already acquired or
+hereafter acquired, that would be infringed by some manner, permitted
+by this License, of making, using, or selling its contributor version,
+but do not include claims that would be infringed only as a
+consequence of further modification of the contributor version.  For
+purposes of this definition, "control" includes the right to grant
+patent sublicenses in a manner consistent with the requirements of
+this License.
+
+  Each contributor grants you a non-exclusive, worldwide, royalty-free
+patent license under the contributor's essential patent claims, to
+make, use, sell, offer for sale, import and otherwise run, modify and
+propagate the contents of its contributor version.
+
+  In the following three paragraphs, a "patent license" is any express
+agreement or commitment, however denominated, not to enforce a patent
+(such as an express permission to practice a patent or covenant not to
+sue for patent infringement).  To "grant" such a patent license to a
+party means to make such an agreement or commitment not to enforce a
+patent against the party.
+
+  If you convey a covered work, knowingly relying on a patent license,
+and the Corresponding Source of the work is not available for anyone
+to copy, free of charge and under the terms of this License, through a
+publicly available network server or other readily accessible means,
+then you must either (1) cause the Corresponding Source to be so
+available, or (2) arrange to deprive yourself of the benefit of the
+patent license for this particular work, or (3) arrange, in a manner
+consistent with the requirements of this License, to extend the patent
+license to downstream recipients.  "Knowingly relying" means you have
+actual knowledge that, but for the patent license, your conveying the
+covered work in a country, or your recipient's use of the covered work
+in a country, would infringe one or more identifiable patents in that
+country that you have reason to believe are valid.
+
+  If, pursuant to or in connection with a single transaction or
+arrangement, you convey, or propagate by procuring conveyance of, a
+covered work, and grant a patent license to some of the parties
+receiving the covered work authorizing them to use, propagate, modify
+or convey a specific copy of the covered work, then the patent license
+you grant is automatically extended to all recipients of the covered
+work and works based on it.
+
+  A patent license is "discriminatory" if it does not include within
+the scope of its coverage, prohibits the exercise of, or is
+conditioned on the non-exercise of one or more of the rights that are
+specifically granted under this License.  You may not convey a covered
+work if you are a party to an arrangement with a third party that is
+in the business of distributing software, under which you make payment
+to the third party based on the extent of your activity of conveying
+the work, and under which the third party grants, to any of the
+parties who would receive the covered work from you, a discriminatory
+patent license (a) in connection with copies of the covered work
+conveyed by you (or copies made from those copies), or (b) primarily
+for and in connection with specific products or compilations that
+contain the covered work, unless you entered into that arrangement,
+or that patent license was granted, prior to 28 March 2007.
+
+  Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+  12. No Surrender of Others' Freedom.
+
+  If conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot convey a
+covered work so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you may
+not convey it at all.  For example, if you agree to terms that obligate you
+to collect a royalty for further conveying from those to whom you convey
+the Program, the only way you could satisfy both those terms and this
+License would be to refrain entirely from conveying the Program.
+
+  13. Use with the GNU Affero General Public License.
+
+  Notwithstanding any other provision of this License, you have
+permission to link or combine any covered work with a work licensed
+under version 3 of the GNU Affero General Public License into a single
+combined work, and to convey the resulting work.  The terms of this
+License will continue to apply to the part which is the covered work,
+but the special requirements of the GNU Affero General Public License,
+section 13, concerning interaction through a network will apply to the
+combination as such.
+
+  14. Revised Versions of this License.
+
+  The Free Software Foundation may publish revised and/or new versions of
+the GNU General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+  Each version is given a distinguishing version number.  If the
+Program specifies that a certain numbered version of the GNU General
+Public License "or any later version" applies to it, you have the
+option of following the terms and conditions either of that numbered
+version or of any later version published by the Free Software
+Foundation.  If the Program does not specify a version number of the
+GNU General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+  If the Program specifies that a proxy can decide which future
+versions of the GNU General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
+  Later license versions may give you additional or different
+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    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 3 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, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<http://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..368c4dc
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,39 @@
+# Copyright (C) 2013 Timo Weingärtner <timo@tiwe.de>
+#
+# This file is part of ssh-agent-filter.
+#
+# ssh-agent-filter 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 3 of the License, or
+# (at your option) any later version.
+#
+# ssh-agent-filter 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 ssh-agent-filter.  If not, see <http://www.gnu.org/licenses/>.
+
+
+CXXFLAGS ?= -g -O2 -Wall -Wold-style-cast
+
+CXXFLAGS += -std=c++11
+LDFLAGS += -lboost_program_options -lboost_filesystem -lboost_system -lnettle
+
+all: ssh-agent-filter.1
+
+ssh-agent-filter.1: ssh-agent-filter
+	help2man -n $< -o $@ -N ./$<
+
+ssh-agent-filter: ssh-agent-filter.o
+
+ssh-agent-filter.o: ssh-agent-filter.C rfc4251.h ssh-agent.h version.h
+
+version.h:
+	test ! -d .git || git describe | sed 's/^.*$$/#define SSH_AGENT_FILTER_VERSION "ssh-agent-filter \0"/' > $@
+
+clean:
+	$(RM) ssh-agent-filter.1 ssh-agent-filter *.o
+
+.PHONY: version.h
diff --git a/rfc4251.h b/rfc4251.h
new file mode 100644
index 0000000..0a0a4ad
--- /dev/null
+++ b/rfc4251.h
@@ -0,0 +1,254 @@
+/*
+ * rfc4251.h -- implements types from RFC 4251, section 5
+ *
+ * rfc4251byte		byte
+ * rfc4251bool		bool
+ * rfc4251uint32	uint32
+ * rfc4251uint64	uint64
+ * rfc4251string	string, incl. mpint and (without splitting) name-list
+ *
+ * those structs contain the objects in their RFC 4251 representation,
+ * conversions are provided via constructors and cast operators
+ *
+ * Copyright (C) 2013 Timo Weingärtner <timo@tiwe.de>
+ *
+ * This file is part of ssh-agent-filter.
+ *
+ * ssh-agent-filter 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * ssh-agent-filter 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 ssh-agent-filter.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <vector>
+#include <string>
+#include <iostream>
+#include <arpa/inet.h>	// ntohl() / htonl()
+#include <gmpxx.h>
+
+struct rfc4251byte {
+	union {
+		uint8_t value;
+		char buf[1];
+	};
+
+	rfc4251byte () = default;
+	rfc4251byte (rfc4251byte const &) = default;
+	rfc4251byte (rfc4251byte &&) = default;
+
+	inline explicit rfc4251byte (uint8_t v) : value(v) {}
+
+	rfc4251byte & operator= (rfc4251byte const &) = default;
+	rfc4251byte & operator= (rfc4251byte &&) = default;
+
+	inline operator uint8_t () const { return value; }
+};
+
+inline std::istream & operator>> (std::istream & is, rfc4251byte & x) {
+	return is.read(x.buf, sizeof(x.buf));
+}
+
+inline std::ostream & operator<< (std::ostream & os, rfc4251byte const & x) {
+	return os.write(x.buf, sizeof(x.buf));;
+}
+
+
+struct rfc4251bool {
+	union {
+		bool value;
+		char buf[1];
+	};
+
+	rfc4251bool () = default;
+	rfc4251bool (rfc4251bool const &) = default;
+	rfc4251bool (rfc4251bool &&) = default;
+
+	inline explicit rfc4251bool (uint8_t v) : value(v) {}
+
+	rfc4251bool & operator= (rfc4251bool const &) = default;
+	rfc4251bool & operator= (rfc4251bool &&) = default;
+
+	inline operator uint8_t () const { return value; }
+};
+
+inline std::istream & operator>> (std::istream & is, rfc4251bool & x) {
+	return is.read(x.buf, sizeof(x.buf));
+}
+
+inline std::ostream & operator<< (std::ostream & os, rfc4251bool const & x) {
+	return os.write(x.buf, sizeof(x.buf));;
+}
+
+
+struct rfc4251uint32 {
+	union {
+		uint32_t value;
+		char buf[4];
+	};
+
+	rfc4251uint32 () = default;
+	rfc4251uint32 (rfc4251uint32 const &) = default;
+	rfc4251uint32 (rfc4251uint32 &&) = default;
+
+	inline explicit rfc4251uint32 (uint32_t v) { value = htonl(v); }
+
+	rfc4251uint32 & operator= (rfc4251uint32 const &) = default;
+	rfc4251uint32 & operator= (rfc4251uint32 &&) = default;
+
+	inline operator uint32_t () const { return ntohl(value); }
+};
+
+inline std::istream & operator>> (std::istream & is, rfc4251uint32 & x) {
+	return is.read(x.buf, sizeof(x.buf));
+}
+
+inline std::ostream & operator<< (std::ostream & os, rfc4251uint32 const & x) {
+	return os.write(x.buf, sizeof(x.buf));;
+}
+
+
+struct rfc4251uint64 {
+	union {
+		uint64_t value;
+		char buf[8];
+	};
+
+	rfc4251uint64 () = default;
+	rfc4251uint64 (rfc4251uint64 const &) = default;
+	rfc4251uint64 (rfc4251uint64 &&) = default;
+
+	inline explicit rfc4251uint64 (uint64_t v);
+
+	rfc4251uint64 & operator= (rfc4251uint64 const &) = default;
+	rfc4251uint64 & operator= (rfc4251uint64 &&) = default;
+
+	inline explicit operator uint64_t () const;
+};
+
+inline rfc4251uint64::rfc4251uint64 (uint64_t v) {
+	for (int_fast8_t i = 7; i >= 0; --i) {
+		buf[i] = v & 0xff;
+		v >>= 8;
+	}
+}
+
+inline rfc4251uint64::operator uint64_t () const {
+	uint64_t ret{0};
+	for (uint_fast8_t i = 0; i < 8; ++i) {
+		ret |= buf[i];
+		ret <<= 8;
+	}
+	return ret;
+}
+
+inline std::istream & operator>> (std::istream & is, rfc4251uint64 & x) {
+	return is.read(x.buf, sizeof(x.buf));
+}
+
+inline std::ostream & operator<< (std::ostream & os, rfc4251uint64 const & x) {
+	return os.write(x.buf, sizeof(x.buf));;
+}
+
+
+struct rfc4251string {
+	std::vector<char> value;
+	
+	rfc4251string () = default;
+	rfc4251string (rfc4251string const &) = default;
+	rfc4251string (rfc4251string &&) = default;
+	
+	inline explicit rfc4251string (char const *);
+	inline explicit rfc4251string (char const *, size_t);
+	inline explicit rfc4251string (std::string const & s) : rfc4251string{s.data(), s.size()} {}
+	inline explicit rfc4251string (mpz_srcptr);
+	inline explicit rfc4251string (mpz_class const & x) : rfc4251string{x.get_mpz_t()} {}
+
+	rfc4251string & operator= (rfc4251string const &) = default;
+	rfc4251string & operator= (rfc4251string &&) = default;
+
+	inline operator std::string () const;
+	inline operator mpz_class () const;
+};
+
+inline rfc4251string::rfc4251string (char const * s) {
+	auto len = ntohl(*reinterpret_cast<uint32_t const *>(s));
+	value.insert(value.begin(), s, s + 4 + len);
+}
+
+inline rfc4251string::rfc4251string (char const * s, size_t l) {
+	rfc4251uint32 tmp(l);
+	value.insert(value.end(), std::begin(tmp.buf), std::end(tmp.buf));
+	value.insert(value.end(), s, s + l);
+}
+
+inline rfc4251string::rfc4251string (mpz_srcptr x) {
+	if (mpz_sgn(x) == 0)
+		value.assign(4, 0);
+	else if (mpz_sgn(x) == 1) {
+		ssize_t bits = mpz_sizeinbase(x, 2);
+		ssize_t bytes = (bits + 7) / 8;
+		ssize_t extrabyte = bits % 8 ? 0 : 1; // need extra byte if MSB is 1 to keep it non-negative
+		value.resize(4 + bytes + extrabyte);
+		*reinterpret_cast<uint32_t *>(value.data()) = htonl(bytes + extrabyte);
+		value[4] = 0;
+		mpz_export(value.data() + 4 + extrabyte, nullptr, 1, 1, 1, 0, x);
+	} else {
+		mpz_class tmp(x);
+		tmp += 1;
+		x = tmp.get_mpz_t();
+		ssize_t bits = mpz_sizeinbase(x, 2);
+		ssize_t bytes = (bits + 7) / 8;
+		ssize_t extrabyte = bits % 8 ? 0 : 1; // need extra byte if MSB is 1 (0 after ^= below) to keep it negative
+		value.resize(4 + bytes + extrabyte);
+		*reinterpret_cast<uint32_t *>(value.data()) = htonl(bytes + extrabyte);
+		value[4] = 0;
+		mpz_export(value.data() + 4 + extrabyte, nullptr, 1, 1, 1, 0, x);
+		for (auto i = value.data() + 4; i < value.data() + value.size(); ++i)
+			*i ^= 0xff;
+	}
+}
+
+inline rfc4251string::operator std::string () const {
+	return std::string(value.begin() + 4, value.end());
+}
+
+inline rfc4251string::operator mpz_class () const {
+	mpz_class ret;
+	mpz_import(ret.get_mpz_t(), value.size() - 4, 1, 1, 1, 0, value.data() + 4);
+	if (mpz_sizeinbase(ret.get_mpz_t(), 2) == (value.size() - 4) * 8) { // negative
+		mpz_com(ret.get_mpz_t(), ret.get_mpz_t());
+		ret += 1;
+		mpz_neg(ret.get_mpz_t(), ret.get_mpz_t());
+	}
+	return ret;
+}
+
+inline std::istream & operator>> (std::istream & is, rfc4251string & s) {
+	s.value.resize(4);
+	if (is.read(s.value.data(), 4)) {
+		auto len = ntohl(*reinterpret_cast<uint32_t const *>(s.value.data()));
+		s.value.resize(4 + len);
+		is.read(s.value.data() + 4, len);
+	}
+	return is;
+}
+
+inline std::ostream & operator<< (std::ostream & os, rfc4251string const & s) {
+	return os.write(s.value.data(), s.value.size());
+}
+
+inline bool operator== (rfc4251string const & l, rfc4251string const & r) {
+	return l.value == r.value;
+}
+
+inline bool operator< (rfc4251string const & l, rfc4251string const & r) {
+	return l.value < r.value;
+}
diff --git a/ssh-agent-filter.C b/ssh-agent-filter.C
new file mode 100644
index 0000000..5aa086b
--- /dev/null
+++ b/ssh-agent-filter.C
@@ -0,0 +1,378 @@
+/*
+ * ssh-agent-filter.C -- filtering proxy for ssh-agent meant to be forwarded to untrusted servers
+ *
+ * Copyright (C) 2013 Timo Weingärtner <timo@tiwe.de>
+ *
+ * This file is part of ssh-agent-filter.
+ *
+ * ssh-agent-filter 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * ssh-agent-filter 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 ssh-agent-filter.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <boost/program_options.hpp>
+namespace po = boost::program_options;
+
+#include <boost/filesystem.hpp>
+namespace fs = boost::filesystem;
+
+#include <string>
+#include <vector>
+#include <set>
+#include <iostream>
+#include <sstream>
+#include <stdexcept>
+#include <thread>
+#include <ext/stdio_filebuf.h>
+
+#include <csignal>
+#include <cstdlib>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sysexits.h>
+#include <nettle/md5.h>
+#include <nettle/base64.h>
+#include <nettle/base16.h>
+
+#include "rfc4251.h"
+#include "ssh-agent.h"
+#include "version.h"
+
+
+std::vector<std::string> allowed_b64;
+std::vector<std::string> allowed_md5;
+std::vector<std::string> allowed_comment;
+std::set<rfc4251string> allowed_pubkeys;
+bool debug{false};
+fs::path path;
+
+
+std::string md5_hex (std::string const & s) {
+	struct md5_ctx ctx;
+	md5_init(&ctx);
+	md5_update(&ctx, s.size(), reinterpret_cast<uint8_t const *>(s.data()));
+	uint8_t bin[MD5_DIGEST_SIZE];
+	md5_digest(&ctx, MD5_DIGEST_SIZE, bin);
+	uint8_t hex[BASE16_ENCODE_LENGTH(MD5_DIGEST_SIZE)];
+	base16_encode_update(hex, MD5_DIGEST_SIZE, bin);
+	return std::string(reinterpret_cast<char const *>(hex), sizeof(hex));
+}
+
+std::string base64_encode (std::string const & s) {
+	struct base64_encode_ctx ctx;
+	base64_encode_init(&ctx);
+	uint8_t b64[BASE64_ENCODE_LENGTH(s.size())];
+	auto len = base64_encode_update(&ctx, b64, s.size(), reinterpret_cast<uint8_t const *>(s.data()));
+	len += base64_encode_final(&ctx, b64 + len);
+	return std::string(reinterpret_cast<char const *>(b64), len);
+}
+
+int make_upstream_agent_conn () {
+	char const * path;
+	int sock;
+	struct sockaddr_un addr;
+
+	if (!(path = getenv("SSH_AUTH_SOCK"))) {
+		std::clog << "no $SSH_AUTH_SOCK" << std::endl;
+		exit(EX_UNAVAILABLE);
+	}
+
+	if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
+		perror("socket");
+		exit(EX_UNAVAILABLE);
+	}
+	
+	addr.sun_family = AF_UNIX;
+	
+	if (strlen(path) >= sizeof(addr.sun_path)) {
+		std::clog << "$SSH_AUTH_SOCK too long" << std::endl;
+		exit(EX_UNAVAILABLE);
+	}
+
+	strcpy(addr.sun_path, path);
+
+	if (connect(sock, reinterpret_cast<struct sockaddr const *>(&addr), sizeof(addr))) {
+		perror("connect");
+		exit(EX_UNAVAILABLE);
+	}
+
+	return sock;
+}
+
+int make_listen_sock () {
+	int sock;
+	struct sockaddr_un addr;
+	
+	if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
+		perror("socket");
+		exit(EX_UNAVAILABLE);
+	}
+
+	addr.sun_family = AF_UNIX;
+	
+	if (path.native().length() >= sizeof(addr.sun_path)) {
+		std::clog << "path for listen socket too long" << std::endl;
+		exit(EX_UNAVAILABLE);
+	}
+
+	strcpy(addr.sun_path, path.c_str());
+
+	if (bind(sock, reinterpret_cast<struct sockaddr const *>(&addr), sizeof(addr))) {
+		perror("bind");
+		exit(EX_UNAVAILABLE);
+	}
+	
+	if (listen(sock, 0)) {
+		perror("listen");
+		exit(EX_UNAVAILABLE);
+	}
+
+	return sock;
+}
+
+void parse_cmdline (int const argc, char const * const * const argv) {
+	po::options_description opts("OPTIONS");
+	opts.add_options()
+		("comment,c",		po::value(&allowed_comment),	"key specified by comment")
+		("debug,d",		po::bool_switch(&debug),	"show even more stuff")
+		("fingerprint,fp,f",	po::value(&allowed_md5),	"key specified by pubkey's hex-encoded md5 fingerprint")
+		("help,h",		"print this help message")
+		("key,k",		po::value(&allowed_b64),	"key specified by base64-encoded pubkey")
+		("version,V",		"print version information")
+		;
+	po::variables_map config;
+	po::store(po::parse_command_line(argc, argv, opts), config);
+	po::notify(config);
+	
+	if (config.count("help")) {
+		std::cout << "Invocation: ssh-agent-filter [ OPTIONS ] -- [ SSH ARGUMENTS ]" << std::endl;
+		std::cout << opts << std::endl;
+		exit(EX_OK);
+	}
+	
+	if (config.count("version")) {
+		std::cout << SSH_AGENT_FILTER_VERSION << std::endl;
+		exit(EX_OK);
+	}
+
+	// canonicalize hashes
+	for (auto & s : allowed_md5)
+		for (auto it = s.begin(); it != s.end(); )
+			if (isxdigit(*it)) {
+				*it = tolower(*it);
+				++it;
+			} else
+				it = s.erase(it);
+}
+
+void setup_filters () {
+	__gnu_cxx::stdio_filebuf<char> agent_filebuf(make_upstream_agent_conn(), std::ios::in | std::ios::out);
+	std::iostream agent(&agent_filebuf);
+	agent.exceptions(std::ios::badbit | std::ios::failbit);
+	
+	agent << rfc4251string(std::string(1, SSH2_AGENTC_REQUEST_IDENTITIES));
+	rfc4251string answer;
+	agent >> answer;
+	std::istringstream answer_iss(answer);
+	answer_iss.exceptions(std::ios::badbit | std::ios::failbit);
+	rfc4251byte resp_code;
+	answer_iss >> resp_code;
+	if (resp_code != SSH2_AGENT_IDENTITIES_ANSWER)
+		throw std::runtime_error("unexpected answer from ssh-agent");
+	rfc4251uint32 keycount;
+	answer_iss >> keycount;
+	for (uint32_t i = keycount; i; --i) {
+		rfc4251string key;
+		rfc4251string comment;
+		answer_iss >> key >> comment;
+		
+		auto b64 = base64_encode(key);
+		if (debug) std::clog << b64 << std::endl;
+		
+		auto md5 = md5_hex(key);
+		if (debug) std::clog << md5 << std::endl;
+		
+		std::string comm(comment);
+		if (debug) std::clog << comm << std::endl;
+		
+		if (std::count(allowed_b64.begin(), allowed_b64.end(), b64)) {
+			allowed_pubkeys.insert(key);
+			if (debug) std::clog << "key allowed by equal base64 representation" << std::endl;
+		}
+		if (std::count(allowed_md5.begin(), allowed_md5.end(), md5)) {
+			allowed_pubkeys.insert(key);
+			if (debug) std::clog << "key allowed by matching md5 fingerprint" << std::endl;
+		}
+		if (std::count(allowed_comment.begin(), allowed_comment.end(), comm)) {
+			allowed_pubkeys.insert(key);
+			if (debug) std::clog << "key allowed by matching comment" << std::endl;
+		}
+		
+		if (debug) std::clog << std::endl;
+	}
+}
+
+rfc4251string handle_request (rfc4251string const & r) {
+	std::istringstream request(r);
+	std::ostringstream answer;
+	request.exceptions(std::ios::badbit | std::ios::failbit);
+	answer.exceptions(std::ios::badbit | std::ios::failbit);
+	rfc4251byte request_code;
+	request >> request_code;
+	switch (request_code) {
+		case SSH2_AGENTC_REQUEST_IDENTITIES:
+			{
+				__gnu_cxx::stdio_filebuf<char> agent_filebuf(make_upstream_agent_conn(), std::ios::in | std::ios::out);
+				std::iostream agent(&agent_filebuf);
+				agent.exceptions(std::ios::badbit | std::ios::failbit);
+				rfc4251string agent_answer;
+				agent << rfc4251string(std::string(1, SSH2_AGENTC_REQUEST_IDENTITIES));
+				agent >> agent_answer;
+				// temp to test key filtering when signing
+				//return agent_answer;
+				std::istringstream agent_answer_iss(agent_answer);
+				rfc4251byte answer_code;
+				rfc4251uint32 keycount;
+				agent_answer_iss >> answer_code >> keycount;
+				if (answer_code != SSH2_AGENT_IDENTITIES_ANSWER)
+					throw std::runtime_error("unexpected answer from ssh-agent");
+				std::vector<std::pair<rfc4251string, rfc4251string>> keys;
+				for (uint32_t i = keycount; i; --i) {
+					rfc4251string key;
+					rfc4251string comment;
+					agent_answer_iss >> key >> comment;
+					if (allowed_pubkeys.count(key))
+						keys.emplace_back(std::move(key), std::move(comment));
+				}
+				answer << answer_code << rfc4251uint32(keys.size());
+				for (auto const & k : keys)
+					answer << k.first << k.second;
+			}
+			break;
+		case SSH2_AGENTC_SIGN_REQUEST:
+			{
+				rfc4251string key;
+				request >> key;
+				if (allowed_pubkeys.count(key)) {
+					__gnu_cxx::stdio_filebuf<char> agent_filebuf(make_upstream_agent_conn(), std::ios::in | std::ios::out);
+					std::iostream agent(&agent_filebuf);
+					agent.exceptions(std::ios::badbit | std::ios::failbit);
+					rfc4251string agent_answer;
+					
+					agent << r;
+					agent >> agent_answer;
+					return agent_answer;
+				} else
+					answer << rfc4251byte(SSH_AGENT_FAILURE);
+			}
+			break;
+		case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
+			answer << rfc4251byte(SSH_AGENT_RSA_IDENTITIES_ANSWER);
+			// we got no SSHv1 keys
+			answer << rfc4251uint32(0);
+			break;
+		case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
+			answer << rfc4251byte(SSH_AGENT_SUCCESS);
+			break;
+		case SSH_AGENTC_RSA_CHALLENGE:
+		case SSH_AGENTC_ADD_RSA_IDENTITY:
+		case SSH_AGENTC_REMOVE_RSA_IDENTITY:
+		case SSH_AGENTC_ADD_RSA_ID_CONSTRAINED:
+		case SSH2_AGENTC_ADD_IDENTITY:
+		case SSH2_AGENTC_REMOVE_IDENTITY:
+		case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
+		case SSH2_AGENTC_ADD_ID_CONSTRAINED:
+		case SSH_AGENTC_ADD_SMARTCARD_KEY:
+		case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
+		case SSH_AGENTC_LOCK:
+		case SSH_AGENTC_UNLOCK:
+		case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
+		default:
+			answer << rfc4251byte(SSH_AGENT_FAILURE);
+			break;
+	}
+
+	return rfc4251string(answer.str());
+}
+
+void handle_client (int const sock) {
+	// we could use only one streambuf and iostream but when
+	// switching from read to write an lseek call is made that
+	// fails with ESPIPE and causes an exception
+	__gnu_cxx::stdio_filebuf<char> client_filebuf_in(sock, std::ios::in);
+	__gnu_cxx::stdio_filebuf<char> client_filebuf_out(sock, std::ios::out);
+	std::istream client_in(&client_filebuf_in);
+	std::ostream client_out(&client_filebuf_out);
+	client_out.exceptions(std::ios::badbit | std::ios::failbit);
+	
+	rfc4251string request;
+	while (client_in >> request) try {
+		client_out << handle_request(request) << std::flush;
+	} catch (...) {
+		break;
+	}
+}
+
+void sighandler (int sig) {
+	switch (sig) {
+		case SIGINT:
+		case SIGPIPE:
+			break;
+		default:
+			remove(path);
+			std::abort();
+	}
+}
+
+int main (int const argc, char const * const * const argv) {
+	parse_cmdline(argc, argv);
+	
+	setup_filters();
+
+	path = fs::current_path() / ("agent." + std::to_string(getpid()));
+	int listen_sock = make_listen_sock();
+
+	if (not debug) {
+		pid_t pid = fork();
+		if (pid == -1) {
+			perror("fork");
+			exit(EX_OSERR);
+		}
+		if (pid > 0) {
+			std::cout << "SSH_AUTH_SOCK='" << path << "'; export SSH_AUTH_SOCK;" << std::endl;
+			std::cout << "SSH_AGENT_PID='" << pid << "'; export SSH_AGENT_PID;" << std::endl;
+			std::cout << "echo 'Agent pid " << pid << "';" << std::endl;
+			exit(EX_OK);
+		}
+	
+		setsid();
+		chdir("/");
+		int devnull = open("/dev/null", O_RDWR);
+		dup2(devnull, 0);
+		dup2(devnull, 1);
+		dup2(devnull, 2);
+		close(devnull);
+
+		signal(SIGINT, sighandler);
+		signal(SIGPIPE, sighandler);
+		signal(SIGHUP, sighandler);
+		signal(SIGTERM, sighandler);
+	}
+
+	int client_sock;
+	while ((client_sock = accept(listen_sock, nullptr, nullptr)) != -1) {
+		std::thread t(handle_client, client_sock);
+		t.detach();
+	}
+}
diff --git a/ssh-agent.h b/ssh-agent.h
new file mode 100644
index 0000000..7824dc5
--- /dev/null
+++ b/ssh-agent.h
@@ -0,0 +1,55 @@
+/*
+ * ssh-agent.h
+ *
+ * constants copied from http://api.libssh.org/rfc/PROTOCOL.agent
+ *
+ * public domain.
+ */
+
+// 3. Protocol message numbers
+
+// 3.1 Requests from client to agent for protocol 1 key operations
+
+#define SSH_AGENTC_REQUEST_RSA_IDENTITIES		1
+#define SSH_AGENTC_RSA_CHALLENGE			3
+#define SSH_AGENTC_ADD_RSA_IDENTITY			7
+#define SSH_AGENTC_REMOVE_RSA_IDENTITY			8
+#define SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES		9
+#define SSH_AGENTC_ADD_RSA_ID_CONSTRAINED		24
+
+// 3.2 Requests from client to agent for protocol 2 key operations
+
+#define SSH2_AGENTC_REQUEST_IDENTITIES			11
+#define SSH2_AGENTC_SIGN_REQUEST			13
+#define SSH2_AGENTC_ADD_IDENTITY			17
+#define SSH2_AGENTC_REMOVE_IDENTITY			18
+#define SSH2_AGENTC_REMOVE_ALL_IDENTITIES		19
+#define SSH2_AGENTC_ADD_ID_CONSTRAINED			25
+
+// 3.3 Key-type independent requests from client to agent
+
+#define SSH_AGENTC_ADD_SMARTCARD_KEY			20
+#define SSH_AGENTC_REMOVE_SMARTCARD_KEY			21
+#define SSH_AGENTC_LOCK					22
+#define SSH_AGENTC_UNLOCK				23
+#define SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED	26
+
+// 3.4 Generic replies from agent to client
+
+#define SSH_AGENT_FAILURE				5
+#define SSH_AGENT_SUCCESS				6
+
+// 3.5 Replies from agent to client for protocol 1 key operations
+
+#define SSH_AGENT_RSA_IDENTITIES_ANSWER			2
+#define SSH_AGENT_RSA_RESPONSE				4
+
+// 3.6 Replies from agent to client for protocol 2 key operations
+
+#define SSH2_AGENT_IDENTITIES_ANSWER			12
+#define SSH2_AGENT_SIGN_RESPONSE			14
+
+// 3.7 Key constraint identifiers
+
+#define SSH_AGENT_CONSTRAIN_LIFETIME			1
+#define SSH_AGENT_CONSTRAIN_CONFIRM			2