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Before HTX was introduced, all the HTTP request elements passed in
pseudo-headers fields were used to build an HTTP/1 request whose syntax
was then scrutinized by the HTTP/1 parser, leaving no room to inject
invalid characters.
While NUL, CR and LF are properly blocked, it is possible to inject
spaces in the method so that once translated to HTTP/1, fields are
shifted by one spcae, and a lenient HTTP/1 server could possibly be
fooled into using a part of the method as the URI. For example, the
following request:
H2 request
:method: "GET /admin? HTTP/1.1"
:path: "/static/images"
would become:
GET /admin? HTTP/1.1 /static/images HTTP/1.1
It's important to note that the resulting request is *not* valid, and
that in order for this to be a problem, it requires that this request
is delivered to an already vulnerable HTTP/1 server.
A workaround here is to reject malformed methods by placing this rule
in the frontend or backend, at least before leaving haproxy in H1:
http-request reject if { method -m reg [^A-Z0-9] }
Alternately H2 may be globally disabled by commenting out the "alpn"
directive on "bind" lines, and by rejecting H2 streams creation by
adding the following statement to the global section:
tune.h2.max-concurrent-streams 0
This patch adds a check for each character of the method to make sure
they belong to the ones permitted in a token, as mentioned in RFC7231#4.1.
This should be backported to versions 2.0 and above. For older versions
not having HTX_FL_PARSING_ERROR, a "goto fail" works as well as it
results in a protocol error at the stream level. Non-HTX versions are
safe because the resulting invalid request will be rejected by the
internal HTTP/1 parser.
Thanks to Tim Düsterhus for reporting that one.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)