%%% Copyright 2009 Andrew Thompson <andrew@hijacked.us>. All rights reserved.
%%%
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%%% modification, are permitted provided that the following conditions are met:
%%%
%%% 1. Redistributions of source code must retain the above copyright notice,
%%% this list of conditions and the following disclaimer.
%%% 2. Redistributions in binary form must reproduce the above copyright
%%% notice, this list of conditions and the following disclaimer in the
%%% documentation and/or other materials provided with the distribution.
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%%% THIS SOFTWARE IS PROVIDED BY THE FREEBSD PROJECT ``AS IS'' AND ANY EXPRESS OR
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%% @doc Module with some general utility functions for SMTP.
-module(smtp_util).
-export([
mxlookup/1,
guess_FQDN/0,
compute_cram_digest/2,
get_cram_string/1,
trim_crlf/1,
rfc5322_timestamp/0,
zone/0,
generate_message_id/0,
parse_rfc822_addresses/1,
parse_rfc5322_addresses/1,
combine_rfc822_addresses/1,
generate_message_boundary/0
]).
-include_lib("kernel/include/inet.hrl").
-type name_address() :: {Name :: string() | undefined, Address :: string()}.
% Use parse_rfc5322_addresses/1 instead
-deprecated([{parse_rfc822_addresses, 1}]).
%% @doc returns a sorted list of mx servers for `Domain', lowest distance first
mxlookup(Domain) ->
case whereis(inet_db) of
P when is_pid(P) ->
ok;
_ ->
inet_db:start()
end,
case lists:keyfind(nameserver, 1, inet_db:get_rc()) of
false ->
% we got no nameservers configured, suck in resolv.conf
inet_config:do_load_resolv(os:type(), longnames);
_ ->
ok
end,
case inet_res:lookup(Domain, in, mx) of
[] ->
lists:map(fun(X) -> {10, inet_parse:ntoa(X)} end, inet_res:lookup(Domain, in, a));
Result ->
lists:sort(Result)
end.
%% @doc guess the current host's fully qualified domain name, on error return "localhost"
-spec guess_FQDN() -> string().
guess_FQDN() ->
{ok, Hostname} = inet:gethostname(),
guess_FQDN_1(Hostname, inet:gethostbyname(Hostname)).
guess_FQDN_1(_Hostname, {ok, #hostent{h_name = FQDN}}) ->
FQDN;
guess_FQDN_1(Hostname, {error, nxdomain = Error}) ->
error_logger:info_msg(
"~p could not get FQDN for ~p (error ~p), using \"localhost\" instead.",
[?MODULE, Error, Hostname]
),
"localhost".
%% @doc Compute the CRAM digest of `Key' and `Data'
-spec compute_cram_digest(Key :: binary(), Data :: binary()) -> binary().
compute_cram_digest(Key, Data) ->
Bin = hmac_md5(Key, Data),
list_to_binary([io_lib:format("~2.16.0b", [X]) || <<X>> <= Bin]).
-ifdef(OTP_RELEASE).
-if(?OTP_RELEASE >= 23).
-define(CRYPTO_MAC, true).
-endif.
-endif.
-ifdef(CRYPTO_MAC).
hmac_md5(Key, Data) ->
crypto:mac(hmac, md5, Key, Data).
-else.
hmac_md5(Key, Data) ->
crypto:hmac(md5, Key, Data).
-endif.
%% @doc Generate a seed string for CRAM.
-spec get_cram_string(Hostname :: string()) -> string().
get_cram_string(Hostname) ->
binary_to_list(
base64:encode(
lists:flatten(
io_lib:format("<~B.~B@~s>", [
rand:uniform(4294967295), rand:uniform(4294967295), Hostname
])
)
)
).
%% @doc Trim \r\n from `String'
-spec trim_crlf(String :: string()) -> string().
trim_crlf(String) ->
string:strip(string:strip(String, right, $\n), right, $\r).
-define(DAYS, ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]).
-define(MONTHS, [
"Jan",
"Feb",
"Mar",
"Apr",
"May",
"Jun",
"Jul",
"Aug",
"Sep",
"Oct",
"Nov",
"Dec"
]).
%% @doc Generate a RFC 5322 timestamp based on the current time
rfc5322_timestamp() ->
{{Year, Month, Day}, {Hour, Minute, Second}} = calendar:local_time(),
NDay = calendar:day_of_the_week(Year, Month, Day),
DoW = lists:nth(NDay, ?DAYS),
MoY = lists:nth(Month, ?MONTHS),
io_lib:format("~s, ~b ~s ~b ~2..0b:~2..0b:~2..0b ~s", [
DoW, Day, MoY, Year, Hour, Minute, Second, zone()
]).
%% @doc Calculate the current timezone and format it like -0400. Borrowed from YAWS.
zone() ->
Time = erlang:universaltime(),
LocalTime = calendar:universal_time_to_local_time(Time),
DiffSecs =
calendar:datetime_to_gregorian_seconds(LocalTime) -
calendar:datetime_to_gregorian_seconds(Time),
zone((DiffSecs / 3600) * 100).
%% Ugly reformatting code to get times like +0000 and -1300
zone(Val) when Val < 0 ->
io_lib:format("-~4..0w", [trunc(abs(Val))]);
zone(Val) when Val >= 0 ->
io_lib:format("+~4..0w", [trunc(abs(Val))]).
%% @doc Generate a unique message ID
generate_message_id() ->
FQDN = guess_FQDN(),
Md5 = [
io_lib:format("~2.16.0b", [X])
|| <<X>> <= erlang:md5(term_to_binary([unique_id(), FQDN]))
],
io_lib:format("<~s@~s>", [Md5, FQDN]).
%% @doc Generate a unique MIME message boundary
generate_message_boundary() ->
FQDN = guess_FQDN(),
[
"_=",
[
io_lib:format("~2.36.0b", [X])
|| <<X>> <= erlang:md5(term_to_binary([unique_id(), FQDN]))
],
"=_"
].
unique_id() ->
{erlang:system_time(), erlang:unique_integer()}.
-define(is_whitespace(Ch), (Ch =< 32)).
combine_rfc822_addresses([]) ->
<<>>;
combine_rfc822_addresses(Addresses) ->
iolist_to_binary(combine_rfc822_addresses(Addresses, [])).
combine_rfc822_addresses([], [32, $, | Acc]) ->
lists:reverse(Acc);
combine_rfc822_addresses([{undefined, Email} | Rest], Acc) ->
combine_rfc822_addresses(Rest, [32, $,, Email | Acc]);
combine_rfc822_addresses([{"", Email} | Rest], Acc) ->
combine_rfc822_addresses(Rest, [32, $,, Email | Acc]);
combine_rfc822_addresses([{<<>>, Email} | Rest], Acc) ->
combine_rfc822_addresses(Rest, [32, $,, Email | Acc]);
combine_rfc822_addresses([{Name, Email} | Rest], Acc) ->
Quoted = [opt_quoted(Name), " <", Email, ">"],
combine_rfc822_addresses(Rest, [32, $,, Quoted | Acc]).
opt_quoted(B) when is_binary(B) ->
opt_quoted(binary_to_list(B));
opt_quoted(S) when is_list(S) ->
NoControls = lists:map(
fun
(C) when C < 32 -> 32;
(C) -> C
end,
S
),
case lists:any(fun is_special/1, NoControls) of
false ->
NoControls;
true ->
lists:flatten([
$",
lists:map(
fun
($\") -> [$\\, $\"];
($\\) -> [$\\, $\\];
(C) -> C
end,
NoControls
),
$"
])
end.
% See https://www.w3.org/Protocols/rfc822/3_Lexical.html#z2
is_special($() -> true;
is_special($)) -> true;
is_special($<) -> true;
is_special($>) -> true;
is_special($@) -> true;
is_special($,) -> true;
is_special($;) -> true;
is_special($:) -> true;
is_special($\\) -> true;
is_special($\") -> true;
is_special($.) -> true;
is_special($[) -> true;
is_special($]) -> true;
% special for some smtp servers
is_special($') -> true;
is_special(_) -> false.
%% @doc Parse list of mail addresses in RFC-5322#section-3.4 `mailbox-list' format
-spec parse_rfc5322_addresses(string() | binary()) -> {ok, [name_address()]} | {error, any()}.
parse_rfc5322_addresses(B) when is_binary(B) ->
parse_rfc5322_addresses(unicode:characters_to_list(B));
parse_rfc5322_addresses(S) when is_list(S) ->
case smtp_rfc5322_scan:string(S) of
{ok, Tokens, _L} ->
F = fun({Name, {addr, Local, Domain}}) ->
{Name, Local ++ "@" ++ Domain}
end,
case smtp_rfc5322_parse:parse(Tokens) of
{ok, {mailbox_list, AddrList}} ->
{ok, lists:map(F, AddrList)};
{ok, {group, {_Groupame, AddrList}}} ->
{ok, lists:map(F, AddrList)};
{error, _} = Err ->
Err
end;
{error, Reason, _L} ->
{error, Reason}
end.
-spec parse_rfc822_addresses(string() | binary()) -> {ok, [name_address()]} | {error, any()}.
parse_rfc822_addresses(B) when is_binary(B) ->
parse_rfc822_addresses(unicode:characters_to_list(B));
parse_rfc822_addresses(S) when is_list(S) ->
Scanned = lists:reverse([{'$end', 0} | scan_rfc822(S, [])]),
smtp_rfc822_parse:parse(Scanned).
scan_rfc822([], Acc) ->
Acc;
scan_rfc822([Ch | R], Acc) when ?is_whitespace(Ch) ->
scan_rfc822(R, Acc);
scan_rfc822([$" | R], Acc) ->
{Token, Rest} = scan_rfc822_scan_endquote(R, [], false),
scan_rfc822(Rest, [{string, 0, Token} | Acc]);
scan_rfc822([$, | Rest], Acc) ->
scan_rfc822(Rest, [{',', 0} | Acc]);
scan_rfc822([$< | Rest], Acc) ->
{Token, R} = scan_rfc822_scan_endpointybracket(Rest),
scan_rfc822(R, [{'>', 0}, {string, 0, Token}, {'<', 0} | Acc]);
scan_rfc822(String, Acc) ->
%% Capture everything except "SP < > ,"
case re:run(String, "^([^\s<>,]+)(.*)", [{capture, all_but_first, list}]) of
{match, [Token, Rest]} ->
scan_rfc822(Rest, [{string, 0, Token} | Acc]);
nomatch ->
[{string, 0, String} | Acc]
end.
scan_rfc822_scan_endpointybracket(String) ->
case re:run(String, "(.*?)>(.*)", [{capture, all_but_first, list}]) of
{match, [Token, Rest]} ->
{Token, Rest};
nomatch ->
{String, []}
end.
scan_rfc822_scan_endquote([$\\ | R], Acc, InEscape) ->
%% in escape
scan_rfc822_scan_endquote(R, Acc, not (InEscape));
scan_rfc822_scan_endquote([$" | R], Acc, true) ->
scan_rfc822_scan_endquote(R, [$" | Acc], false);
scan_rfc822_scan_endquote([$" | Rest], Acc, false) ->
%% Done!
{lists:reverse(Acc), Rest};
scan_rfc822_scan_endquote([Ch | Rest], Acc, _) ->
scan_rfc822_scan_endquote(Rest, [Ch | Acc], false).
