Mercurial > dropbear
view libtommath/README.md @ 1788:1fc0012b9c38
Fix handling of replies to global requests (#112)
The current code assumes that all global requests want / need a reply.
This isn't always true and the request itself indicates if it wants a
reply or not.
It causes a specific problem with [email protected] messages.
These are sent by OpenSSH after authentication to inform the client of
potential other host keys for the host. This can be used to add a new
type of host key or to rotate host keys.
The initial information message from the server is sent as a global
request, but with want_reply set to false. This means that the server
doesn't expect an answer to this message. Instead the client needs to
send a prove request as a reply if it wants to receive proof of
ownership for the host keys.
The bug doesn't cause any current problems with due to how OpenSSH
treats receiving the failure message. It instead treats it as a
keepalive message and further ignores it.
Arguably this is a protocol violation though of Dropbear and it is only
accidental that it doesn't cause a problem with OpenSSH.
The bug was found when adding host keys support to libssh, which is more
strict protocol wise and treats the unexpected failure message an error,
also see https://gitlab.com/libssh/libssh-mirror/-/merge_requests/145
for more information.
The fix here is to honor the want_reply flag in the global request and
to only send a reply if the other side expects a reply.
| author | Dirkjan Bussink <d.bussink@gmail.com> |
|---|---|
| date | Thu, 10 Dec 2020 16:13:13 +0100 |
| parents | 1051e4eea25a |
| children |
line wrap: on
line source
# libtommath This is the git repository for [LibTomMath](http://www.libtom.net/LibTomMath/), a free open source portable number theoretic multiple-precision integer (MPI) library written entirely in C. ## Build Status ### Travis CI master: [](https://travis-ci.org/libtom/libtommath) develop: [](https://travis-ci.org/libtom/libtommath) ### AppVeyor master: [](https://ci.appveyor.com/project/libtom/libtommath/branch/master) develop: [](https://ci.appveyor.com/project/libtom/libtommath/branch/develop) ### ABI Laboratory API/ABI changes: [check here](https://abi-laboratory.pro/tracker/timeline/libtommath/) ## Summary The `develop` branch contains the in-development version. Stable releases are tagged. Documentation is built from the LaTeX file `bn.tex`. There is also limited documentation in `tommath.h`. There is also a document, `tommath.pdf`, which describes the goals of the project and many of the algorithms used. The project can be build by using `make`. Along with the usual `make`, `make clean` and `make install`, there are several other build targets, see the makefile for details. There are also makefiles for certain specific platforms. ## Testing Tests are located in `demo/` and can be built in two flavors. * `make test` creates a stand-alone test binary that executes several test routines. * `make mtest_opponent` creates a test binary that is intended to be run against `mtest`. `mtest` can be built with `make mtest` and test execution is done like `./mtest/mtest | ./mtest_opponent`. `mtest` is creating test vectors using an alternative MPI library and `test` is consuming these vectors to verify correct behavior of ltm ## Building and Installing Building is straightforward for GNU Linux only, the section "Building LibTomMath" in the documentation in `doc/bn.pdf` has the details.