Add the SMTPUTF8 extension (RFC 6531) · jcollie.dev/zig-smtp@75bfa30

+4 -1

README.md

··· 226 226 status codes: carried in every server reply and advertised via 227 227 ENHANCEDSTATUSCODES; detected by the client. 228 228 - [RFC 6531](https://datatracker.ietf.org/doc/html/rfc6531) — SMTPUTF8: 229 - detected by the client in EHLO; not implemented by the server. 229 + client (`mailFromUtf8`) and server (advertised; non-ASCII addresses 230 + require the parameter and must be valid UTF-8, rejected with 553 5.6.7 231 + per [RFC 6533](https://datatracker.ietf.org/doc/html/rfc6533) otherwise; 232 + the flag reaches handlers via `Envelope.smtputf8`). 230 233 231 234 TLS itself (TLS 1.3, [RFC 8446](https://datatracker.ietf.org/doc/html/rfc8446)) 232 235 is provided by [ianic/tls.zig](https://github.com/ianic/tls.zig).

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nix/interop-test.nix

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··· 206 206 with subtest(f"zsmtp client to {name}, CHUNKING"): 207 207 deliver("--chunking", port, f"zsmtp to {name} chunked", mailbox) 208 208 209 + with subtest("zsmtp client to postfix, SMTPUTF8"): 210 + machine.succeed( 211 + "printf 'Subject: interop\\r\\n\\r\\nzsmtp to postfix utf8\\r\\n'" 212 + " | zsmtp send --smtputf8 127.0.0.1 25" 213 + " 'böb@example.com' alice@localhost" 214 + ) 215 + machine.wait_until_succeeds( 216 + "grep -r 'zsmtp to postfix utf8' /var/spool/mail/alice/", timeout=60 217 + ) 218 + 209 219 with subtest("zsmtp client to exim, AUTH PLAIN"): 210 220 deliver( 211 221 "--user alice --password secret --auth-method plain",

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src/Client.zig

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··· 414 414 } 415 415 }; 416 416 417 + /// Like `mailFrom`, but requests the SMTPUTF8 extension 418 + /// ([RFC 6531](https://datatracker.ietf.org/doc/html/rfc6531)) so the 419 + /// envelope addresses and message headers may contain UTF-8. Use only when 420 + /// `Extensions.smtputf8` was advertised. 421 + pub fn mailFromUtf8(c: *Client, from: []const u8) Error!void { 422 + try c.send("MAIL FROM:<{s}> SMTPUTF8", .{from}); 423 + _ = try c.expectClass(2); 424 + } 425 + 417 426 /// Sends one BDAT chunk (the CHUNKING extension, 418 427 /// [RFC 3030](https://datatracker.ietf.org/doc/html/rfc3030)) and reads the 419 428 /// server's reply. Use only when `Extensions.chunking` was advertised. The ··· 932 941 // Raw transmission: the leading dot is not stuffed. 933 942 try client.sendMessageChunked(".raw\r\n"); 934 943 try std.testing.expectEqualStrings("BDAT 6 LAST\r\n.raw\r\n", writer.buffered()); 944 + } 945 + 946 + test mailFromUtf8 { 947 + var reader: Io.Reader = .fixed("250 2.1.0 Ok\r\n"); 948 + var out_buf: [64]u8 = undefined; 949 + var writer: Io.Writer = .fixed(&out_buf); 950 + var reply_buf: [64]u8 = undefined; 951 + var client: Client = .init(&reader, &writer, &reply_buf); 952 + 953 + try client.mailFromUtf8("böb@example.com"); 954 + try std.testing.expectEqualStrings("MAIL FROM:<böb@example.com> SMTPUTF8\r\n", writer.buffered()); 935 955 }

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src/Server.zig

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··· 92 92 /// Value of the MAIL BODY= parameter 93 93 /// ([RFC 6152](https://datatracker.ietf.org/doc/html/rfc6152)). 94 94 body: Body = .unspecified, 95 + /// True when the client requested the SMTPUTF8 extension 96 + /// ([RFC 6531](https://datatracker.ietf.org/doc/html/rfc6531)); the 97 + /// envelope addresses and message headers may then contain UTF-8. 98 + smtputf8: bool = false, 95 99 96 100 pub const Body = enum { unspecified, seven_bit, eight_bit_mime }; 97 101 }; ··· 153 157 var recipients: std.ArrayList([]const u8) = .empty; 154 158 var declared_size: ?u64 = null; 155 159 var body: Envelope.Body = .unspecified; 160 + var smtputf8 = false; 156 161 157 162 try s.writer.print("220 {s} ESMTP ready" ++ protocol.crlf, .{s.options.hostname}); 158 163 try s.writer.flush(); ··· 178 183 recipients = .empty; 179 184 declared_size = null; 180 185 body = .unspecified; 186 + smtputf8 = false; 181 187 _ = arena_state.reset(.retain_capacity); 182 188 try s.reply(250, s.options.hostname); 183 189 }, ··· 187 193 recipients = .empty; 188 194 declared_size = null; 189 195 body = .unspecified; 196 + smtputf8 = false; 190 197 _ = arena_state.reset(.retain_capacity); 191 198 // Every reply carries an enhanced status code (RFC 3463), so 192 199 // the ENHANCEDSTATUSCODES extension (RFC 2034) is advertised. 193 - try s.writer.print("250-{s}\r\n250-PIPELINING\r\n250-8BITMIME\r\n250-CHUNKING\r\n250-ENHANCEDSTATUSCODES\r\n", .{s.options.hostname}); 200 + try s.writer.print("250-{s}\r\n250-PIPELINING\r\n250-8BITMIME\r\n250-CHUNKING\r\n250-SMTPUTF8\r\n250-ENHANCEDSTATUSCODES\r\n", .{s.options.hostname}); 194 201 if (s.options.tls) |config| { 195 202 if (config.mode == .starttls and !s.secured) 196 203 try s.writer.writeAll("250-STARTTLS\r\n"); ··· 215 222 } 216 223 var mail_declared_size: ?u64 = null; 217 224 var mail_body: Envelope.Body = .unspecified; 225 + var mail_smtputf8 = false; 218 226 var params_ok = true; 219 227 var params = args.paramIterator(); 220 228 while (params.next()) |param| { ··· 240 248 params_ok = false; 241 249 break; 242 250 } 251 + } else if (std.ascii.eqlIgnoreCase(param.keyword, "SMTPUTF8")) { 252 + if (param.value.len != 0) { 253 + try s.reply(501, "5.5.4 SMTPUTF8 takes no value"); 254 + params_ok = false; 255 + break; 256 + } 257 + mail_smtputf8 = true; 243 258 } else { 244 259 try s.reply(555, "5.5.4 Unrecognized parameter"); 245 260 params_ok = false; ··· 247 262 } 248 263 } 249 264 if (!params_ok) continue; 265 + if (!try s.validateAddress(args.path, mail_smtputf8)) continue; 250 266 if (s.handler.vtable.mailFrom) |callback| { 251 267 switch (callback(s.handler.context, args.path)) { 252 268 .accept => {}, ··· 259 275 from = try arena.dupe(u8, args.path); 260 276 declared_size = mail_declared_size; 261 277 body = mail_body; 278 + smtputf8 = mail_smtputf8; 262 279 try s.reply(250, "2.1.0 Ok"); 263 280 }, 264 281 .rcpt => |args| { ··· 270 287 try s.reply(555, "5.5.4 Unrecognized parameter"); 271 288 continue; 272 289 } 290 + if (!try s.validateAddress(args.path, smtputf8)) continue; 273 291 if (recipients.items.len >= s.options.max_recipients) { 274 292 try s.reply(452, "4.5.3 Too many recipients"); 275 293 continue; ··· 296 314 .recipients = recipients.items, 297 315 .declared_size = declared_size, 298 316 .body = body, 317 + .smtputf8 = smtputf8, 299 318 }); 300 319 from = null; 301 320 recipients = .empty; 302 321 declared_size = null; 303 322 body = .unspecified; 323 + smtputf8 = false; 304 324 _ = arena_state.reset(.retain_capacity); 305 325 }, 306 326 .bdat => |args| { ··· 319 339 .recipients = recipients.items, 320 340 .declared_size = declared_size, 321 341 .body = body, 342 + .smtputf8 = smtputf8, 322 343 }, args); 323 344 from = null; 324 345 recipients = .empty; 325 346 declared_size = null; 326 347 body = .unspecified; 348 + smtputf8 = false; 327 349 _ = arena_state.reset(.retain_capacity); 328 350 switch (outcome) { 329 351 .done => {}, ··· 335 357 recipients = .empty; 336 358 declared_size = null; 337 359 body = .unspecified; 360 + smtputf8 = false; 338 361 _ = arena_state.reset(.retain_capacity); 339 362 try s.reply(250, "2.0.0 Ok"); 340 363 }, ··· 364 387 recipients = .empty; 365 388 declared_size = null; 366 389 body = .unspecified; 390 + smtputf8 = false; 367 391 _ = arena_state.reset(.retain_capacity); 368 392 }, 369 393 .quit => { ··· 842 866 } 843 867 }; 844 868 869 + /// Enforces RFC 6531: a non-ASCII envelope address is only allowed when 870 + /// the transaction requested SMTPUTF8, and must be well-formed UTF-8. 871 + /// Replies and returns false on rejection. 872 + fn validateAddress(s: *Server, path: []const u8, smtputf8: bool) error{WriteFailed}!bool { 873 + for (path) |byte| { 874 + if (byte >= 0x80) { 875 + if (!smtputf8) { 876 + try s.reply(553, "5.6.7 Non-ASCII address requires SMTPUTF8"); 877 + return false; 878 + } 879 + if (!std.unicode.utf8ValidateSlice(path)) { 880 + try s.reply(553, "5.6.7 Address is not valid UTF-8"); 881 + return false; 882 + } 883 + return true; 884 + } 885 + } 886 + return true; 887 + } 888 + 845 889 fn reply(s: *Server, code: u16, text: []const u8) error{WriteFailed}!void { 846 890 try s.writer.print("{d} {s}" ++ protocol.crlf, .{ code, text }); 847 891 try s.writer.flush(); ··· 864 908 reject_recipient: ?[]const u8 = null, 865 909 declared_size: ?u64 = null, 866 910 body: Envelope.Body = .unspecified, 911 + smtputf8: bool = false, 867 912 /// When set, enables the authenticate callback accepting user "alice" 868 913 /// with this password. 869 914 password: ?[]const u8 = null, ··· 914 959 h.messages_accepted += 1; 915 960 h.declared_size = envelope.declared_size; 916 961 h.body = envelope.body; 962 + h.smtputf8 = envelope.smtputf8; 917 963 return .accept; 918 964 } 919 965 }; ··· 955 1001 956 1002 try std.testing.expectEqualStrings( 957 1003 "220 mx.test ESMTP ready\r\n" ++ 958 - "250-mx.test\r\n250-PIPELINING\r\n250-8BITMIME\r\n250-CHUNKING\r\n250-ENHANCEDSTATUSCODES\r\n250 SIZE 16777216\r\n" ++ 1004 + "250-mx.test\r\n250-PIPELINING\r\n250-8BITMIME\r\n250-CHUNKING\r\n250-SMTPUTF8\r\n250-ENHANCEDSTATUSCODES\r\n250 SIZE 16777216\r\n" ++ 959 1005 "250 2.1.0 Ok\r\n" ++ 960 1006 "250 2.1.5 Ok\r\n" ++ 961 1007 "250 2.1.5 Ok\r\n" ++ ··· 1405 1451 "mail from:<a@b> FOO=bar\r\n" ++ 1406 1452 "mail from:<a@b> SIZE=nan\r\n" ++ 1407 1453 "starttls\r\n" ++ 1454 + "mail from:<böb@test.ex>\r\n" ++ 1455 + "mail from:<a@b> SMTPUTF8=YES\r\n" ++ 1456 + "mail from:<böb@test.ex> SMTPUTF8\r\n" ++ 1457 + "rset\r\n" ++ 1408 1458 "BDAT 5\r\n" ++ 1409 1459 "abc\r\n" ++ 1410 1460 "mail from:<chunky@test.ex>\r\n" ++ ··· 1426 1476 "503 5.5.1 Send EHLO first\r\n" ++ 1427 1477 "503 5.5.1 Need MAIL command first\r\n" ++ 1428 1478 "250-localhost\r\n250-PIPELINING\r\n250-8BITMIME\r\n250-CHUNKING\r\n" ++ 1429 - "250-ENHANCEDSTATUSCODES\r\n250 SIZE 16777216\r\n" ++ 1479 + "250-SMTPUTF8\r\n250-ENHANCEDSTATUSCODES\r\n250 SIZE 16777216\r\n" ++ 1430 1480 "501 5.5.4 Syntax error in parameters\r\n" ++ 1431 1481 "501 5.5.4 Syntax error in parameters\r\n" ++ 1432 1482 "250 2.1.0 Ok\r\n" ++ ··· 1447 1497 "555 5.5.4 Unrecognized parameter\r\n" ++ 1448 1498 "501 5.5.2 Invalid SIZE parameter\r\n" ++ 1449 1499 "502 5.5.1 STARTTLS not supported\r\n" ++ 1500 + "553 5.6.7 Non-ASCII address requires SMTPUTF8\r\n" ++ 1501 + "501 5.5.4 SMTPUTF8 takes no value\r\n" ++ 1502 + "250 2.1.0 Ok\r\n" ++ 1503 + "250 2.0.0 Ok\r\n" ++ 1450 1504 "503 5.5.1 Need RCPT command first\r\n" ++ 1451 1505 "250 2.1.0 Ok\r\n" ++ 1452 1506 "250 2.1.5 Ok\r\n" ++ ··· 1620 1674 try std.testing.expect(std.mem.indexOf(u8, output, "250 2.0.0 Ok, message accepted") != null); 1621 1675 // The NOOP after the final chunk proves the stream stayed in sync. 1622 1676 try std.testing.expect(std.mem.indexOf(u8, output, "250 2.0.0 Ok\r\n221") != null); 1677 + } 1678 + 1679 + test "SMTPUTF8 transactions and non-ASCII address enforcement" { 1680 + var h: TestHandler = .{}; 1681 + defer h.deinit(); 1682 + 1683 + var out_buf: [2048]u8 = undefined; 1684 + const output = try runScript( 1685 + "EHLO client.example.org\r\n" ++ 1686 + // Non-ASCII without the parameter: rejected. 1687 + "MAIL FROM:<böb@example.com>\r\n" ++ 1688 + "MAIL FROM:<alice@example.com>\r\n" ++ 1689 + "RCPT TO:<jürgen@example.net>\r\n" ++ 1690 + "RSET\r\n" ++ 1691 + // The parameter takes no value. 1692 + "MAIL FROM:<a@example.com> SMTPUTF8=YES\r\n" ++ 1693 + // Invalid UTF-8 bytes even with the parameter: rejected. 1694 + "MAIL FROM:<b\xff\xfeb@example.com> SMTPUTF8\r\n" ++ 1695 + // Proper internationalized transaction. 1696 + "MAIL FROM:<böb@example.com> SMTPUTF8\r\n" ++ 1697 + "RCPT TO:<jürgen@example.net>\r\n" ++ 1698 + "DATA\r\nSubject: ünïcode\r\n\r\nhello\r\n.\r\n" ++ 1699 + "QUIT\r\n", 1700 + &out_buf, 1701 + h.handler(), 1702 + .{}, 1703 + ); 1704 + 1705 + try std.testing.expectEqual(@as(usize, 1), h.messages_accepted); 1706 + try std.testing.expect(h.smtputf8); 1707 + try std.testing.expectEqualStrings("böb@example.com", h.from.items); 1708 + try std.testing.expectEqualStrings("jürgen@example.net;", h.recipients.items); 1709 + try std.testing.expect(std.mem.indexOf(u8, output, "250-SMTPUTF8\r\n") != null); 1710 + try std.testing.expect(std.mem.indexOf(u8, output, "553 5.6.7 Non-ASCII address requires SMTPUTF8") != null); 1711 + try std.testing.expect(std.mem.indexOf(u8, output, "501 5.5.4 SMTPUTF8 takes no value") != null); 1712 + try std.testing.expect(std.mem.indexOf(u8, output, "553 5.6.7 Address is not valid UTF-8") != null); 1623 1713 }

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src/main.zig

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··· 3 3 4 4 //! Demo CLI for the zsmtp library. 5 5 //! 6 - //! zsmtp send [--tls|--starttls] [--insecure] [--chunking] 6 + //! zsmtp send [--tls|--starttls] [--insecure] [--chunking] [--smtputf8] 7 7 //! [--user <u> --password <p>] 8 8 //! [--auth-method plain|login|cram-md5] <host> <port> <from> <to>... 9 9 //! send a message read from stdin; --tls speaks TLS from the first ··· 39 39 config.insecure = true; 40 40 } else if (std.mem.eql(u8, rest[0], "--chunking")) { 41 41 config.chunking = true; 42 + } else if (std.mem.eql(u8, rest[0], "--smtputf8")) { 43 + config.smtputf8 = true; 42 44 } else if (rest.len >= 2 and std.mem.eql(u8, rest[0], "--user")) { 43 45 config.username = rest[1]; 44 46 rest = rest[1..]; ··· 102 104 mode: enum { plain, tls, starttls } = .plain, 103 105 insecure: bool = false, 104 106 chunking: bool = false, 107 + smtputf8: bool = false, 105 108 username: ?[]const u8 = null, 106 109 password: ?[]const u8 = null, 107 110 auth_method: enum { auto, plain, login, cram_md5 } = .auto, ··· 194 197 std.log.err("server does not advertise CHUNKING", .{}); 195 198 return error.ChunkingNotAdvertised; 196 199 } 197 - transact(&client, from, recipients, &stdin.interface, config.chunking) catch |err| { 200 + if (config.smtputf8 and !extensions.smtputf8) { 201 + std.log.err("server does not advertise SMTPUTF8", .{}); 202 + return error.SmtpUtf8NotAdvertised; 203 + } 204 + transact(&client, from, recipients, &stdin.interface, config.chunking, config.smtputf8) catch |err| { 198 205 if (err == error.UnexpectedReply) { 199 206 const reply = client.last_reply.?; 200 207 std.log.err("server rejected: {d} {s}", .{ reply.code, reply.text }); ··· 213 220 recipients: []const []const u8, 214 221 message: *Io.Reader, 215 222 chunking: bool, 223 + smtputf8: bool, 216 224 ) zsmtp.Client.Error!void { 217 - try client.mailFrom(from); 225 + if (smtputf8) try client.mailFromUtf8(from) else try client.mailFrom(from); 218 226 for (recipients) |recipient| try client.rcptTo(recipient); 219 227 if (chunking) { 220 228 // BDAT sends the input verbatim (no line-ending normalization).

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test/protocol-torture.script

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··· 12 12 ??? 250-PIPELINING 13 13 ??? 250-8BITMIME 14 14 ??? 250-CHUNKING 15 + ??? 250-SMTPUTF8 15 16 ??? 250-ENHANCEDSTATUSCODES 16 17 ??? 250 SIZE 17 18 mail ··· 57 58 ??? 501 58 59 starttls 59 60 ??? 502 61 + mail from:<böb@test.ex> 62 + ??? 553 63 + mail from:<a@b> SMTPUTF8=YES 64 + ??? 501 65 + mail from:<böb@test.ex> SMTPUTF8 66 + ??? 250 67 + rset 68 + ??? 250 60 69 BDAT 5 61 70 abc 62 71 ??? 503

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