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construct/matrix/fed_well_known.cc

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// The Construct
//
// Copyright (C) The Construct Developers, Authors & Contributors
// Copyright (C) 2016-2020 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
namespace ircd::m::fed::well_known
{
static std::tuple<ircd::http::code, ircd::string_view, ircd::string_view>
fetch(const mutable_buffer &,
const net::hostport &,
const string_view &url);
extern log::log log;
}
decltype(ircd::m::fed::well_known::log)
ircd::m::fed::well_known::log
{
"m.well-known"
};
decltype(ircd::m::fed::well_known::cache_default)
ircd::m::fed::well_known::cache_default
{
{ "name", "ircd.m.fed.well-known.cache.default" },
{ "default", 24 * 60 * 60L },
};
decltype(ircd::m::fed::well_known::cache_error)
ircd::m::fed::well_known::cache_error
{
{ "name", "ircd.m.fed.well-known.cache.error" },
{ "default", 36 * 60 * 60L },
};
///NOTE: not yet used until HTTP cache headers in response are respected.
decltype(ircd::m::fed::well_known::cache_max)
ircd::m::fed::well_known::cache_max
{
{ "name", "ircd.m.fed.well-known.cache.max" },
{ "default", 48 * 60 * 60L },
};
decltype(ircd::m::fed::well_known::fetch_timeout)
ircd::m::fed::well_known::fetch_timeout
{
{ "name", "ircd.m.fed.well-known.fetch.timeout" },
{ "default", 15L },
};
decltype(ircd::m::fed::well_known::fetch_redirects)
ircd::m::fed::well_known::fetch_redirects
{
{ "name", "ircd.m.fed.well-known.fetch.redirects" },
{ "default", 2L },
};
ircd::string_view
ircd::m::fed::well_known::get(const mutable_buffer &buf,
const string_view &origin)
try
{
static const string_view type
{
"well-known.matrix.server"
};
const m::room::id::buf room_id
{
"dns", m::my_host()
};
const m::room room
{
room_id
};
const m::event::idx event_idx
{
room.get(std::nothrow, type, origin)
};
const milliseconds origin_server_ts
{
m::get<time_t>(std::nothrow, event_idx, "origin_server_ts", time_t(0))
};
const json::object content
{
origin_server_ts > 0ms?
m::get(std::nothrow, event_idx, "content", buf):
const_buffer{}
};
const seconds ttl
{
content.get<time_t>("ttl", time_t(86400))
};
const string_view cached
{
data(buf), move(buf, json::string(content["m.server"]))
};
const system_point expires
{
origin_server_ts + ttl
};
const bool expired
{
ircd::now<system_point>() > expires
};
const bool valid
{
!empty(cached)
};
// Crucial value that will provide us with a return string for this
// function in any case. This is obtained by either using the value
// found in cache or making a network query for a new value. expired=true
// when a network query needs to be made, otherwise we can return the
// cached value. If the network query fails, this value is still defaulted
// as the origin string to return and we'll also cache that too.
const string_view delegated
{
expired || !valid?
fetch(buf + size(cached), origin):
cached
};
// Branch on valid cache hit to return result.
if(valid && !expired)
{
char tmbuf[48];
log::debug
{
log, "%s found in cache delegated to %s event_idx:%u expires %s",
origin,
cached,
event_idx,
timef(tmbuf, expires, localtime),
};
return delegated;
}
// Conditions for valid expired cache hit w/ failure to reacquire.
const bool fallback
{
valid
&& expired
&& cached != delegated
&& origin == delegated
&& now<system_point>() < expires + seconds(cache_max)
};
if(fallback)
{
char tmbuf[48];
log::debug
{
log, "%s found in cache delegated to %s event_idx:%u expired %s",
origin,
cached,
event_idx,
timef(tmbuf, expires, localtime),
};
return cached;
}
// Any time the well-known result is the same as the origin (that
// includes legitimate errors where fetch_well_known() returns the
// origin to default) we consider that an error and use the error
// TTL value. Sorry, no exponential backoff implemented yet.
const auto cache_ttl
{
origin == delegated?
seconds(cache_error).count():
seconds(cache_default).count()
};
// Write our record to the cache room; note that this doesn't really
// match the format of other DNS records in this room since it's a bit
// simpler, but we don't share the ircd.dns.rr type prefix anyway.
const auto cache_id
{
m::send(room, m::me(), type, origin, json::members
{
{ "ttl", cache_ttl },
{ "m.server", delegated },
})
};
log::debug
{
log, "%s caching delegation to %s to cache in %s",
origin,
delegated,
string_view{cache_id},
};
return delegated;
}
catch(const ctx::interrupted &)
{
throw;
}
catch(const std::exception &e)
{
log::error
{
log, "%s :%s",
origin,
e.what(),
};
return string_view
{
data(buf), move(buf, origin)
};
}
ircd::string_view
ircd::m::fed::well_known::fetch(const mutable_buffer &user_buf,
const string_view &origin)
try
{
static const string_view path
{
"/.well-known/matrix/server"
};
// If the supplied buffer isn't large enough to make the full
// HTTP request, allocate one that is.
const unique_mutable_buffer req_buf
{
size(user_buf) < 8_KiB? 8_KiB: 0UL
};
const mutable_buffer buf
{
req_buf? req_buf: user_buf
};
rfc3986::uri uri;
uri.remote = origin;
uri.path = path;
json::object response;
unique_mutable_buffer carry;
for(size_t i(0); i < fetch_redirects; ++i)
{
const auto &[code, location, content]
{
fetch(buf, uri.remote, uri.path)
};
// Successful error; bail
if(code >= 400)
return string_view
{
data(user_buf), move(user_buf, origin)
};
// Successful result; response content handled after loop.
if(code < 300)
{
response = content;
break;
}
// Indirection code, but no location response header
if(!location)
return string_view
{
data(user_buf), move(user_buf, origin)
};
// Redirection; carry over the new target by copying it because it's
// in the buffer which we'll be overwriting for the new request.
carry = unique_mutable_buffer{location};
uri = string_view{carry};
// Indirection code, bad location header.
if(!uri.path || !uri.remote)
return string_view
{
data(user_buf), move(user_buf, origin)
};
}
const json::string &m_server
{
response["m.server"]
};
if(!m_server)
return string_view
{
data(user_buf), move(user_buf, origin)
};
// This construction validates we didn't get a junk string
volatile const net::hostport ret
{
m_server
};
log::debug
{
log, "%s query to %s found delegation to %s",
origin,
uri.remote,
m_server,
};
// Move the returned string to the front of the buffer; this overwrites
// any other incoming content to focus on just the unquoted string.
return string_view
{
data(user_buf), move(user_buf, m_server)
};
}
catch(const ctx::interrupted &)
{
throw;
}
catch(const std::exception &e)
{
log::derror
{
log, "%s in network query :%s",
origin,
e.what(),
};
return string_view
{
data(user_buf), move(user_buf, origin)
};
}
/// Return a tuple of the HTTP code, any Location header, and the response
/// content. These values are unconditional if this function doesn't throw,
/// but if there's no Location header and/or content then those will be empty
/// string_view's. This function is intended to be run in a loop by the caller
/// to chase redirection. No HTTP codes will throw from here; server and
/// network errors (and others) will.
std::tuple<ircd::http::code, ircd::string_view, ircd::string_view>
ircd::m::fed::well_known::fetch(const mutable_buffer &buf,
const net::hostport &remote,
const string_view &url)
{
// Hard target https service; do not inherit any matrix service from remote.
const net::hostport target
{
host(remote), "https", port(remote)
};
window_buffer wb
{
buf
};
const http::header headers[]
{
{ "User-Agent", info::user_agent },
};
http::request
{
wb, host(target), "GET", url, 0, {}, headers
};
const const_buffer out_head
{
wb.completed()
};
// Remaining space in buffer is used for received head; note that below
// we specify this same buffer for in.content, but that's a trick
// recognized by ircd::server to place received content directly after
// head in this buffer without any additional dynamic allocation.
const mutable_buffer in_head
{
buf + size(out_head)
};
server::request::opts opts;
opts.http_exceptions = false; // 3xx/4xx/5xx response won't throw.
server::request request
{
target,
{ out_head },
{ in_head, in_head },
&opts
};
const auto code
{
request.get(seconds(fetch_timeout))
};
thread_local char rembuf[rfc3986::DOMAIN_BUFSIZE * 2];
log::debug
{
log, "fetch from %s %s :%u %s",
string(rembuf, target),
url,
uint(code),
http::status(code)
};
const http::response::head head
{
request.in.gethead(request)
};
return
{
code,
head.location,
request.in.content,
};
}