mimemail: utf-8 headers with newline in them would cause a crash when encoding

[seriyps]

> Mail = {<<"text">>, <<"plain">>, [{<<"Subject">>, <<"Привет\nмир"/utf8>>}, {<<"From">>, <<"[email protected]">>}, {<<"Content-Type">>, <<"text/plain; charset=utf-8">>}], #{}, <<"Test">>}.
{<<"text">>,<<"plain">>,
 [{<<"Subject">>,
   <<208,159,209,128,208,184,208,178,208,181,209,130,10,208,
     188,208,184,209,128>>},
  {<<"From">>,<<"[email protected]">>},
  {<<"Content-Type">>,<<"text/plain; charset=utf-8">>}],
 #{},<<"Test">>}
> mimemail:encode(Mail).
** exception error: no function clause matching
 mimemail:rfc2047_utf8_encode([10,208,188,208,184,209,128],
                                                                             "5B=0D=2B=0D=8B=0D=08=1D=F9=0D=?Q?8-FTU?=",40,"28=1D=") (gen_smtp/src/mimemail.erl, line 964)
     in function  mimemail:encode_headers/1 (gen_smtp/src/mimemail.erl, line 788)
     in call from mimemail:encode/2 (gen_smtp/src/mimemail.erl, line 165)

here 10 is \n. I guess that's because we don't have clause for characters below 32 here, so, I guess, \t and \r would cause the same issue

gen_smtp/src/mimemail.erl

Lines 964 to 985 in 7b50cfa

	rfc2047_utf8_encode(T, Acc, WordLen, Char) when WordLen + length(Char) > 73 ->
	CloseLine = lists:reverse("?=\r\n "),
	NewLine = Char ++ lists:reverse("=?UTF-8?Q?"),
	%% Make sure that the individual encoded words are not longer than 76 chars (including charset etc)
	rfc2047_utf8_encode(T, NewLine ++ CloseLine ++ Acc, length(NewLine), []);
	rfc2047_utf8_encode([], Acc, _WordLen, Char) ->
	lists:reverse("=?" ++ Char ++ Acc);
	%% ASCII characters dont encode except space, ?, _, =, and .
	rfc2047_utf8_encode([C|T], Acc, WordLen, Char) when C > 32 andalso C < 127 andalso C /= 32
	andalso C /= $? andalso C /= $_ andalso C /= $= andalso C /= $. ->
	rfc2047_utf8_encode(T, Char ++ Acc, WordLen+length(Char), [C]);
	%% Encode all other ASCII
	rfc2047_utf8_encode([C|T], Acc, WordLen, Char) when C >= 32 andalso C < 127 ->
	rfc2047_utf8_encode(T, Char ++ Acc, WordLen+length(Char), encode_byte(C));
	%% First byte of UTF-8 sequence
	%% ensure that encoded 2-4 byte UTF-8 characters keept in one line
	rfc2047_utf8_encode([C|T], Acc, WordLen, Char) when C > 192 andalso C =< 247 ->
	UTFBytes = utf_char_bytes(C),
	{Rest, ExtraUTFBytes} = encode_extra_utf_bytes(UTFBytes-1, T),
	rfc2047_utf8_encode(Rest, Char ++ Acc, WordLen+length(Char), ExtraUTFBytes ++ encode_byte(C)).

[seriyps]

Python seems to QP-encode al lthe characters below 32, except \r and \n:

> import quopri
> quopri.encodestring(b"".join(chr(i).encode("utf8") for i in range(1, 255)))
b'=01=02=03=04=05=06=07=08=09\n=0B=0C\r=0E=0F=10=11=12=13=14=15=16=17=18=19=1A=1B=1C=1D=1E=1F !"#$%&\'()*+,-=\n./0123456789:;<=3D>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuv=\nwxyz{|}~=7F=C2=80=C2=81=C2=82=C2=83=C2=84=C2=85=C2=86=C2=87=C2=88=C2=89=C2=\n=8A=C2=8B=C2=8C=C2=8D=C2=8E=C2=8F=C2=90=C2=91=C2=92=C2=93=C2=94=C2=95=C2=96=\n=C2=97=C2=98=C2=99=C2=9A=C2=9B=C2=9C=C2=9D=C2=9E=C2=9F=C2=A0=C2=A1=C2=A2=C2=\n=A3=C2=A4=C2=A5=C2=A6=C2=A7=C2=A8=C2=A9=C2=AA=C2=AB=C2=AC=C2=AD=C2=AE=C2=AF=\n=C2=B0=C2=B1=C2=B2=C2=B3=C2=B4=C2=B5=C2=B6=C2=B7=C2=B8=C2=B9=C2=BA=C2=BB=C2=\n=BC=C2=BD=C2=BE=C2=BF=C3=80=C3=81=C3=82=C3=83=C3=84=C3=85=C3=86=C3=87=C3=88=\n=C3=89=C3=8A=C3=8B=C3=8C=C3=8D=C3=8E=C3=8F=C3=90=C3=91=C3=92=C3=93=C3=94=C3=\n=95=C3=96=C3=97=C3=98=C3=99=C3=9A=C3=9B=C3=9C=C3=9D=C3=9E=C3=9F=C3=A0=C3=A1=\n=C3=A2=C3=A3=C3=A4=C3=A5=C3=A6=C3=A7=C3=A8=C3=A9=C3=AA=C3=AB=C3=AC=C3=AD=C3=\n=AE=C3=AF=C3=B0=C3=B1=C3=B2=C3=B3=C3=B4=C3=B5=C3=B6=C3=B7=C3=B8=C3=B9=C3=BA=\n=C3=BB=C3=BC=C3=BD=C3=BE'
> print(quopri.encodestring(b"".join(chr(i).encode("utf8") for i in range(1, 255))).decode('ascii'))
"""
=01=02=03=04=05=06=07=08=09
=0E=0F=10=11=12=13=14=15=16=17=18=19=1A=1B=1C=1D=1E=1F !"#$%&'()*+,-=
./0123456789:;<=3D>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuv=
wxyz{|}~=7F=C2=80=C2=81=C2=82=C2=83=C2=84=C2=85=C2=86=C2=87=C2=88=C2=89=C2=
=8A=C2=8B=C2=8C=C2=8D=C2=8E=C2=8F=C2=90=C2=91=C2=92=C2=93=C2=94=C2=95=C2=96=
=C2=97=C2=98=C2=99=C2=9A=C2=9B=C2=9C=C2=9D=C2=9E=C2=9F=C2=A0=C2=A1=C2=A2=C2=
=A3=C2=A4=C2=A5=C2=A6=C2=A7=C2=A8=C2=A9=C2=AA=C2=AB=C2=AC=C2=AD=C2=AE=C2=AF=
=C2=B0=C2=B1=C2=B2=C2=B3=C2=B4=C2=B5=C2=B6=C2=B7=C2=B8=C2=B9=C2=BA=C2=BB=C2=
=BC=C2=BD=C2=BE=C2=BF=C3=80=C3=81=C3=82=C3=83=C3=84=C3=85=C3=86=C3=87=C3=88=
=C3=89=C3=8A=C3=8B=C3=8C=C3=8D=C3=8E=C3=8F=C3=90=C3=91=C3=92=C3=93=C3=94=C3=
=95=C3=96=C3=97=C3=98=C3=99=C3=9A=C3=9B=C3=9C=C3=9D=C3=9E=C3=9F=C3=A0=C3=A1=
=C3=A2=C3=A3=C3=A4=C3=A5=C3=A6=C3=A7=C3=A8=C3=A9=C3=AA=C3=AB=C3=AC=C3=AD=C3=
=AE=C3=AF=C3=B0=C3=B1=C3=B2=C3=B3=C3=B4=C3=B5=C3=B6=C3=B7=C3=B8=C3=B9=C3=BA=
=C3=BB=C3=BC=C3=BD=C3=BE
"""