util.random: Test whether util.crand works before using it (fix #1734)
util.crand can be configured at compile time to use the Linux
getrandom() system call, available from Linux 3.17, but it is still
possible to load it with an older kernel lacking that system call, where
attempting to use it throws an ENOSYS error.
By testing for this on load we can fall back to /dev/urandom in this
case.
-- Prosody IM
-- Copyright (C) 2008-2014 Matthew Wild
-- Copyright (C) 2008-2014 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--
local ok, crand = pcall(require, "util.crand");
if ok and pcall(crand.bytes, 1) then return crand; end
local urandom, urandom_err = io.open("/dev/urandom", "r");
local function bytes(n)
local data, err = urandom:read(n);
if not data then
if err then
error("Unable to retrieve data from secure random number generator (/dev/urandom): "..tostring(err));
else
error("Secure random number generator (/dev/urandom) returned an end-of-file condition");
end
end
return data;
end
if not urandom then
function bytes()
error("Unable to obtain a secure random number generator, please see https://prosody.im/doc/random ("..urandom_err..")");
end
end
return {
bytes = bytes;
_source = "/dev/urandom";
};