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|
-- Bulk redirects for HAProxy
-- Copyright (C) 2021 Sergey Poznyakoff
--
-- 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, 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/>.
local bulkredirect = {}
__ENV = bulkredirect
--[[
Iterator factory to successively strip off the trailing pathname
element from a path.
On input, T is the pathname (optionally terminated by /).
Returns iterator function that, on each call, returns the pathname
with its trailing element removed. Trailing element here means the
everything past the last '/' character.
]]
local function prevsegm (t)
local s = t
if not s:match("/$") then s = s .. "/" end
return function ()
s = s:match("(.*)/")
return s
end
end
--
-- Module global variables:
--
rt = {}
--[[ Redirection table. It is indexed by the request host name
(the value given by the HTTP Host header). The corresponding value
can be either a string or a table.
A string value refers to another host name (an alias).
A table supplies the actual mapping from an URI to another URL.
When a request to P?Q arrives (where P denotes the pathname part and
Q denotes query arguments), the P is looked up in the table. If the
entry rt[P] does not exist, the trailing pathname component is
removed from P and the resulting string P1 (unless it is empty) is
used as the look-up key. The process continues until either the entry
rt[P1] is found, or P1 is reduced to an empty string. The latter means
there is no redirect for the given P?Q combination.
The lookup process is reduced to a single look up if the global
variable 'exact' is true (see below).
If the entry rt[P1] is found and is a string, it gives the location
of the redirect. Prior to returning a 301 reply, this location is
augmented by pathname part removed from P during the look up process,
and the query part (if any). These modifications are controlled by
the global variables 'strippath' and 'stripquery'. If 'strippath' is
true, the removed pathname components are not added back to the
location. Similarly, if 'stripquery' is true, the query part is not
appended to the location. The 301 reply code is the default. If the
'temporary' global variable is set to true, the code 302 will be used
instead.
If rt[P1] is a table, it must contain a sequence of two elements.
The element rt[P1][1] supplies the new location if Q is not present.
The element rt[P1][2] is an associative table, indexed by possible
values of Q (including empty value). Both rt[P1][1] and rt[P1][2][Q]
can contain either a string or a table value. The string value
supplies the new location as described above. The table value
supplies the new location in the element [1]. Rest of elements
(2 up to 5) are boolean values overriding the default global variables
for this entry. They are located in the following order:
2 - exact
3 - strippath
4 - stripquery
5 - temporary
]]
www = false
--[[ If set to true, the rules for a hostname "X" apply also to
hostname "www.X"
]]
exact = false
--[[ If set to true, no path prefix search is done: the redirection reply
is returned only if the input path is present in the table.
]]
strippath = false
--[[ By default the path components stripped during the look up process
are added back to the returned location. If this variable is set
to true, these components are dropped instead.
]]
stripquery = false
--[[ By default the query part (if any) is appended to the new
location when returning the redirection reply. Setting this variable
to true disables this
]]
temporary = false
-- Whether to return temporary (302) or permanent (301) reply.
--
-- Redirect the request if it matches one of the entries in the RT table.
--
function bulkredirect.request (txn)
local headers = txn.http:req_get_headers()
local reply = txn:reply()
local path = txn.f:path():sub(2)
local host = headers["host"][0]
-- Get the per-host redirection table
local rthost = rt[host]
-- Resolve eventual alias chain.
while type(rthost) == 'string'
do
rthost = rt[rthost]
end
-- If no corresponding host entry found, start from the default
-- entry.
if not rthost then
rthost = rt["*"]
end
if rthost then
local location
-- Successively strip the trailing element off the path and look up
-- the remaining part in the table.
for i in prevsegm(path) do
local exact, strippath, stripquery, temporary = exact, strippath, stripquery, temporary
if rthost[i] then
-- If the entry is found, it is either a table or a string
if type(rthost[i]) == 'table' then
local dt = rthost[i]
local query = txn.f:query()
if query then
if dt[2] then
dt = dt[2][query]
else
dt = dt[1]
end
else
dt = dt[1]
end
location = dt[1]
if dt[2] ~= nil then
exact = dt[2]
end
if dt[3] ~= nil then
strippath = dt[3]
end
if dt[4] ~= nil then
stripquery = dt[4]
end
if dt[5] ~= nil then
temporary = dt[5]
end
else
location = rthost[i]
end
end
if location then
if not (location:match('^http://') or location:match('^https://')
or location:match('^/')) then
location = '/'..location
end
if not exact or i == path or i..'/' == path then
if not strippath then
location = location .. path:sub(i:len() + 1)
end
if not stripquery and txn.f:query() then
location = location .. '?' .. txn.f:query()
end
core.Debug("REDIRECT " .. host .. txn.f:path() .. " to " .. location)
if temporary then
reply:set_status(302, "Moved Temporarily")
else
reply:set_status(301, "Moved Permanently")
end
reply:add_header("Location", location)
txn:done(reply)
break
end
end
end
end
end
-- Populate the redirection table
--[[
Syntax:
input ::= statement | input statement
statement ::= option | domain | redirect
option ::= 'option' optlist [,]
domain ::= '[' HOSTNAME ']'
redirect ::= STRING STRING optlist [,]
optlist ::= OPTNAME | optilist ',' OPTNAME
OPTNAME ::= 'www' | 'exact' | 'strippath' | 'stripquery' | 'temporary'
<or any of these prefixed with 'no'>
HOSTNAME ::= <any valid hostname>
]]
local function parseopt (s, t, loc)
local valid = {
['www'] = true,
['exact'] = true,
['strippath'] = true,
['stripquery'] = true,
['temporary'] = true
}
function options (str, loc)
local s = str
return function ()
if s == nil or s == "" then
return nil
end
local opt, rest
opt, rest = s:match("^(%w+)%s*,%s*(.*)")
if not opt then
opt = s:match("^%w+$")
if not opt then
error(loc .. ": bad option list syntax near " .. s, 0)
end
end
s = rest
return opt
end
end
if not t then
t = _ENV
end
for opt in options(s, loc) do
local neg = opt:match("^no(%w+)$")
local val = true
if neg then
opt = neg
val = not val
end
if not valid[opt] then
error(loc .. ': invalid option ' .. opt, 0)
end
t[opt] = val
end
end
local function set_dst (dt, src, dst)
local path, query = src:match('^(.+)?(.+)')
if path then
if not dt[src] then
dt[src] = {nil, {}}
elseif type(dt[src]) == 'string' then
dt[src] = { { dt[src] }, {} }
end
dt[src][2][query] = dst
elseif type(dt[src]) == 'table' then
dt[src][1] = dst
elseif type(dst) == 'table' then
dt[src] = { dst }
else
dt[src] = dst
end
end
local function clone (orig)
local copy
if type(orig) == 'table' then
copy = {}
for k,v in pairs(orig) do
copy[k] = clone(v)
end
setmetatable(copy, clone(getmetatable(orig)))
else
copy = orig
end
return copy
end
local function www_complement (name)
local s = name:match('^www%.(.+)')
if not s then s = 'www.' .. name end
return s
end
local function populate_www_complements (rt, dup)
local crt = {}
for d,t in pairs(rt) do
local compl = www_complement(d)
if rt[compl] then
for k,v in pairs(t) do
-- FIXME: Error message if rt[compl][k] exists
crt[compl][k] = clone(v)
end
elseif dup then
crt[compl] = clone(t)
else
crt[compl] = d
end
end
for d,t in pairs(crt) do
rt[d] = t
end
end
local function load_redirect_file (f, filename)
local domain
local ln = 1
local rt = {}
local domopt = {}
local parsetab = {
{ '^#', function () end },
{ '^%s*$', function () end },
{ '^option%s+(.*)',
function (s)
local t
if domain then
t = domopt
else
t = _ENV
end
parseopt(s, t, filename .. ':' .. ln)
end
},
{ '^%s*%[(.+)%]%s*$',
function (s)
domain = s
if not rt[domain] then rt[domain] = {} end
end
},
{ '^%s*([^%s]+)%s+([^%s]+)%s*(.*)$',
function (src, dst, optlist)
if not domain then
error(filename .. ':' .. ln .. ': declare [domain] first', 0)
end
if src:match('^/') then
src = src:sub(2)
end
if dst:match('^/') then
dst = dst:sub(2)
end
local optab = domopt
if optlist ~= '' then
optab = clone(domopt)
parseopt(optlist, optab, filename .. ':' .. ln)
end
if optab['exact'] ~= exact then
if type(dst) == 'string' then dst = { dst } end
dst[2] = optab['exact']
end
if optab['strippath'] ~= strippath then
if type(dst) == 'string' then dst = { dst } end
dst[3] = optab['strippath']
end
if optab['stripquery'] ~= stripquery then
if type(dst) == 'string' then dst = { dst } end
dst[4] = optab['stripquery']
end
if optab['temporary'] ~= temporary then
if type(dst) == 'string' then dst = { dst } end
dst[5] = optab['temporary']
end
if optab['www'] ~= nil then
if www == optab['www'] then
return
elseif www then
populate_www_complements (rt, true)
www = nil
end
end
set_dst(rt[domain], src, dst)
if optab['www'] then
local s = www_complement(domain)
if not rt[s] then rt[s] = {} end
set_dst(rt[s], src, dst)
end
end
}
}
for line in f:lines() do
ln = ln + 1
for i = 1, #parsetab do
local t = {line:match(parsetab[i][1])}
if t[1] then
parsetab[i][2](table.unpack(t))
goto continue
end
end
error(filename .. ':' .. ln .. ': syntax error', 0)
::continue::
end
if www then
populate_www_complements (rt, false)
www = nil
end
_ENV['rt'] = rt
end
local function load_redirect_table ()
local name = os.getenv('HAPROXY_BULKREDIRECT')
if name == nil then
name = '/etc/haproxy/bulkredirect.rt'
end
if name:match('%.lua$') then
rt, www, exact, strippath, stripquery, temporary = dofile(name)
else
local file, err = io.open(name,"r")
if file ~= nil then
local status, err = pcall(load_redirect_file, file, name)
file:close()
if not status then
core.Alert(err)
end
else
core.Alert("can't open " .. name .. ": " .. err)
end
end
end
-- Load redirects
load_redirect_table()
-- Register the actions with HAProxy
core.register_action("bulkredirect", {"http-req"}, bulkredirect.request, 0)
|