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#!/usr/bin/lua5.2
--[[
Example NHRP events processing script which validates NHRP registration GRE
address against certificate subjectAltName IP, and auto-creates BGP pairings
and filters based on S-BGP extensions.
Copyright (c) 2015-2017 Timo Teräs
See LICENSE file for license details
]]--
local posix = require 'posix'
local struct = require 'struct'
local cq = require 'cqueues'
local cqs = require 'cqueues.socket'
local x509 = require 'openssl.x509'
local x509an = require 'openssl.x509.altname'
local rfc3779 = require 'asn1.rfc3779'
local SOCK = "/var/run/nhrp-events.sock"
posix.unlink(SOCK)
local loop = cq.new()
local nulfd = posix.open("/dev/null", posix.O_RDWR)
local listener = cqs.listen{path=SOCK}
posix.chown(SOCK, "quagga", "quagga")
posix.setpid("u", "quagga")
posix.setpid("g", "quagga")
posix.openlog("nhrp-events", "np")
function string.hex2bin(str)
return str:gsub('..', function(cc) return string.char(tonumber(cc, 16)) end)
end
local function decode_ext(cert, name, tpe)
local ext = cert:getExtension(name)
if not ext then return end
return tpe.decode(ext:getData())
end
local function do_parse_cert(cert, out)
for type, value in pairs(cert:getSubjectAlt()) do
if type == 'IP' then
table.insert(out.GRE, value)
end
end
if #out.GRE == 0 then return end
local asn = decode_ext(cert, 'sbgp-autonomousSysNum', rfc3779.ASIdentifiers)
if asn and asn.asnum and asn.asnum.asIdsOrRanges then
for _, as in ipairs(asn.asnum.asIdsOrRanges) do
if as.id then
out.AS = tonumber(as.id)
break
end
end
end
local addrBlocks = decode_ext(cert, 'sbgp-ipAddrBlock', rfc3779.IPAddrBlocks)
for _, ab in ipairs(addrBlocks or {}) do
if ab.ipAddressChoice and ab.ipAddressChoice.addressesOrRanges then
for _, a in ipairs(ab.ipAddressChoice.addressesOrRanges) do
if a.addressPrefix then
table.insert(out.NET, a.addressPrefix)
end
end
end
end
return true
end
local function parse_cert(certhex)
local out = {
cn = "(no CN)",
AS = 0,
GRE = {},
NET = {},
}
local cert = x509.new(certhex:hex2bin(), 'der')
out.cn = tostring(cert:getSubject())
-- Recognize hubs by certificate's CN to have OU=Hubs
out.hub = out.cn:match("/OU=Hubs/") and true or nil
do_parse_cert(cert, out)
return out
end
local function execute(desc, cmd, ...)
local piper, pipew = posix.pipe()
if piper == nil then
return error("Pipe failed")
end
local pid = posix.fork()
if pid == -1 then
return error("Fork failed")
end
if pid == 0 then
posix.close(piper)
posix.dup2(nulfd, 0)
posix.dup2(pipew, 1)
posix.dup2(nulfd, 2)
posix.execp(cmd, ...)
os.exit(1)
end
posix.close(pipew)
-- This blocks -- perhaps should handle command executions in separate queue.
local output = {}
while true do
local d = posix.read(piper, 8192)
if d == nil or d == "" then break end
table.insert(output, d)
end
posix.close(piper)
local _, reason, status = posix.wait(pid)
if status == 0 then
posix.syslog(6, ("Executed '%s' successfully"):format(desc))
else
posix.syslog(3, ("Failed to execute '%s': %s %d"):format(desc, reason, status))
end
return status, table.concat(output)
end
local function configure_bgp(desc, ...)
local args = {
"-d", "bgpd",
"-c", "configure terminal",
}
for _, val in ipairs({...}) do
table.insert(args, "-c")
table.insert(args, val)
end
return execute(desc, "vtysh", table.unpack(args))
end
local last_bgp_reset = 0
local function bgp_reset(msg, local_cert)
local now = os.time()
if last_bgp_reset + 60 > now then return end
last_bgp_reset = now
configure_bgp("spoke reset",
"route-map RTT-SET permit 10", "set metric rtt", "exit",
"route-map RTT-ADD permit 10", "set metric +rtt", "exit",
("router bgp %d"):format(local_cert.AS),
"no neighbor hubs",
"neighbor hubs peer-group",
"neighbor hubs remote-as 65000",
"neighbor hubs ebgp-multihop 1",
"neighbor hubs disable-connected-check",
"neighbor hubs timers 10 30",
"neighbor hubs timers connect 10",
"neighbor hubs next-hop-self all",
"neighbor hubs soft-reconfiguration inbound",
"neighbor hubs route-map RTT-ADD in")
end
local function bgp_nhs_up(msg, remote_cert, local_cert)
configure_bgp(("nhs-up %s"):format(msg.remote_addr),
("router bgp %s"):format(local_cert.AS),
("neighbor %s peer-group hubs"):format(msg.remote_addr))
end
local function bgp_nhs_down(msg, remote_cert, local_cert)
configure_bgp(("nhs-down %s"):format(msg.remote_addr),
("router bgp %s"):format(local_cert.AS),
("no neighbor %s"):format(msg.remote_addr))
end
local function bgp_create_spoke_rules(msg, remote_cert, local_cert)
if not local_cert.hub then return end
local bgpcfg = {}
for seq, net in ipairs(remote_cert.NET) do
table.insert(bgpcfg,
("ip prefix-list net-%s-in seq %d permit %s le %d"):format(
msg.remote_addr, seq * 5, net,
remote_cert.hub and 32 or 26))
end
table.insert(bgpcfg, ("router bgp %s"):format(local_cert.AS))
if remote_cert.hub then
table.insert(bgpcfg, ("neighbor %s peer-group hubs"):format(msg.remote_addr))
elseif local_cert.AS == remote_cert.AS then
table.insert(bgpcfg, ("neighbor %s peer-group spoke-ibgp"):format(msg.remote_addr))
else
table.insert(bgpcfg, ("neighbor %s remote-as %s"):format(msg.remote_addr, remote_cert.AS))
table.insert(bgpcfg, ("neighbor %s peer-group spoke-ebgp"):format(msg.remote_addr))
end
table.insert(bgpcfg, ("neighbor %s prefix-list net-%s-in in"):format(msg.remote_addr, msg.remote_addr))
local status, output = configure_bgp(("nhc-register %s"):format(msg.remote_addr), table.unpack(bgpcfg))
if output:find("Cannot") then
posix.syslog(6, "BGP: "..output)
configure_bgp(
("nhc-recreate %s"):format(msg.remote_addr),
("router bgp %s"):format(local_cert.AS),
("no neighbor %s"):format(msg.remote_addr),
table.unpack(bgpcfg))
end
end
local function handle_message(msg)
if msg.event ~= "authorize-binding" then return end
-- Verify protocol address against certificate
local auth = false
local local_cert = parse_cert(msg.local_cert)
local remote_cert = parse_cert(msg.remote_cert)
for _, gre in pairs(remote_cert.GRE) do
if gre == msg.remote_addr then auth = true end
end
if not auth then
posix.syslog(3, ("GRE %s to NBMA %s DENIED (cert '%s', allows: %s)"):format(
msg.remote_addr, msg.remote_nbma,
remote_cert.cn, table.concat(remote_cert.GRE, " ")))
return "deny"
end
posix.syslog(6, ("GRE %s to NBMA %s authenticated for %s"):format(
msg.remote_addr, msg.remote_nbma, remote_cert.cn))
-- Automatic BGP binding for hub-spoke connections
if msg.type == "nhs" and msg.old_type ~= "nhs" then
if not local_cert.hub then
if tonumber(msg.num_nhs) == 0 and msg.vc_initiated == "yes" then
bgp_reset(msg, local_cert)
end
bgp_nhs_up(msg, remote_cert, local_cert)
else
bgp_create_spoke_rules(msg, remote_cert, local_cert)
end
elseif msg.type ~= "nhs" and msg.old_type == "nhs" then
bgp_nhs_down(msg, remote_cert, local_cert)
elseif msg.type == "dynamic" and msg.old_type ~= "dynamic" then
bgp_create_spoke_rules(msg, remote_cert, local_cert)
end
return "accept"
end
local function handle_connection(conn)
local msg = {}
for l in conn:lines() do
if l == "" then
res = handle_message(msg)
if msg.eventid then
conn:write(("eventid=%s\nresult=%s\n\n"):format(msg.eventid, res or "default"))
end
msg = {}
else
local key, value = l:match('([^=]*)=(.*)')
if key and value then
msg[key] = value
end
end
end
conn:close()
end
loop:wrap(function()
while true do
local conn = listener:accept()
conn:setmode("b", "bl")
loop:wrap(function()
local ok, msg = pcall(handle_connection, conn)
if not ok then posix.syslog(3, msg) end
conn:close()
end)
end
end)
print(loop:loop())
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