smtp.cpp

   1 #include <gflags/gflags.h>
   2 namespace gflags {
   3 }
   4
   5 // These need to be at least the length of any string it's trying to match.
   6 DEFINE_uint64(cmd_bfr_size, 4 * 1024, "command parser buffer size");
   7 DEFINE_uint64(data_bfr_size, 64 * 1024, "data parser buffer size");
   8
   9 DEFINE_uint64(max_xfer_size, 64 * 1024, "maximum BDAT transfer size");
  10
  11 #include <seccomp.h>
  12
  13 #include <fstream>
  14
  15 #include "Session.hpp"
  16 #include "esc.hpp"
  17 #include "fs.hpp"
  18 #include "iobuffer.hpp"
  19 #include "osutil.hpp"
  20
  21 #include <cstdlib>
  22 #include <memory>
  23
  24 #include <signal.h>
  25
  26 #include <tao/pegtl.hpp>
  27 #include <tao/pegtl/contrib/abnf.hpp>
  28
  29 using namespace tao::pegtl;
  30 using namespace tao::pegtl::abnf;
  31
  32 namespace RFC5321 {
  33
  34 struct Ctx {
  35   Session session;
  36
  37   std::string mb_loc;
  38   std::string mb_dom;
  39
  40   std::pair<std::string, std::string>          param;
  41   std::unordered_map<std::string, std::string> parameters;
  42
  43   std::streamsize chunk_size;
  44
  45   Ctx(fs::path config_path, std::function<void(void)> read_hook)
  46     : session(config_path, read_hook)
  47   {
  48   }
  49 };
  50
  51 // clang-format off
  52
  53 struct UTF8_tail : range<'\x80', '\xBF'> {};
  54
  55 struct UTF8_1 : range<'\x00', '\x7F'> {};
  56
  57 struct UTF8_2 : seq<range<'\xC2', '\xDF'>, UTF8_tail> {};
  58
  59 struct UTF8_3 : sor<seq<one<'\xE0'>, range<'\xA0', '\xBF'>, UTF8_tail>,
  60                     seq<range<'\xE1', '\xEC'>, rep<2, UTF8_tail>>,
  61                     seq<one<'\xED'>, range<'\x80', '\x9F'>, UTF8_tail>,
  62                     seq<range<'\xEE', '\xEF'>, rep<2, UTF8_tail>>> {};
  63
  64 struct UTF8_4 : sor<seq<one<'\xF0'>, range<'\x90', '\xBF'>, rep<2, UTF8_tail>>,
  65                     seq<range<'\xF1', '\xF3'>, rep<3, UTF8_tail>>,
  66                     seq<one<'\xF4'>, range<'\x80', '\x8F'>, rep<2, UTF8_tail>>> {};
  67
  68 struct UTF8_non_ascii : sor<UTF8_2, UTF8_3, UTF8_4> {};
  69
  70 struct quoted_pair : seq<one<'\\'>, sor<VCHAR, WSP>> {};
  71
  72 using dot = one<'.'>;
  73 using colon = one<':'>;
  74 using dash = one<'-'>;
  75
  76 struct u_let_dig : sor<ALPHA, DIGIT, UTF8_non_ascii> {};
  77
  78 struct u_ldh_tail : star<sor<seq<plus<one<'-'>>, u_let_dig>, u_let_dig>> {};
  79
  80 struct u_label : seq<u_let_dig, u_ldh_tail> {};
  81
  82 struct let_dig : sor<ALPHA, DIGIT> {};
  83
  84 struct ldh_tail : star<sor<seq<plus<one<'-'>>, let_dig>, let_dig>> {};
  85
  86 struct ldh_str : seq<let_dig, ldh_tail> {};
  87
  88 // struct label : seq<let_dig, opt<ldh_str>> {};
  89
  90 struct sub_domain : u_label {};
  91
  92 struct domain : list_tail<sub_domain, dot> {};
  93
  94 struct dec_octet : sor<seq<string<'2','5'>, range<'0','5'>>,
  95                        seq<one<'2'>, range<'0','4'>, DIGIT>,
  96                        seq<range<'0', '1'>, rep<2, DIGIT>>,
  97                        rep_min_max<1, 2, DIGIT>> {};
  98
  99 struct IPv4_address_literal
 100     : seq<dec_octet, dot, dec_octet, dot, dec_octet, dot, dec_octet> {};
 101
 102 struct h16 : rep_min_max<1, 4, HEXDIG> {};
 103
 104 struct ls32 : sor<seq<h16, colon, h16>, IPv4_address_literal> {};
 105
 106 struct dcolon : two<':'> {};
 107
 108 struct IPv6address : sor<seq<                                          rep<6, h16, colon>, ls32>,
 109                          seq<                                  dcolon, rep<5, h16, colon>, ls32>,
 110                          seq<opt<h16                        >, dcolon, rep<4, h16, colon>, ls32>,
 111                          seq<opt<h16,     opt<   colon, h16>>, dcolon, rep<3, h16, colon>, ls32>,
 112                          seq<opt<h16, rep_opt<2, colon, h16>>, dcolon, rep<2, h16, colon>, ls32>,
 113                          seq<opt<h16, rep_opt<3, colon, h16>>, dcolon,        h16, colon,  ls32>,
 114                          seq<opt<h16, rep_opt<4, colon, h16>>, dcolon,                     ls32>,
 115                          seq<opt<h16, rep_opt<5, colon, h16>>, dcolon,                      h16>,
 116                          seq<opt<h16, rep_opt<6, colon, h16>>, dcolon                          >> {};
 117
 118 struct IPv6_address_literal : seq<TAO_PEGTL_ISTRING("IPv6:"), IPv6address> {};
 119
 120 struct dcontent : ranges<33, 90, 94, 126> {};
 121
 122 struct standardized_tag : ldh_str {};
 123
 124 struct general_address_literal : seq<standardized_tag, colon, plus<dcontent>> {};
 125
 126 // See rfc 5321 Section 4.1.3
 127 struct address_literal : seq<one<'['>,
 128                              sor<IPv4_address_literal,
 129                                  IPv6_address_literal,
 130                                  general_address_literal>,
 131                              one<']'>> {};
 132
 133 struct at_domain : seq<one<'@'>, domain> {};
 134
 135 // The qtextSMTP rule explained: it's ASCII...
 136 // excluding all the control chars below SPACE
 137 //           34 '"' the double quote
 138 //           92 '\\' the back slash
 139 //           DEL
 140 // So including:
 141 // 32-33:  ' ' and '!'
 142 // 35-91:  "#$%&'()*+,-./" 0-9 ":;<=>?@"  A-Z  '['
 143 // 93-126: "]^_`"  a-z  "{|}~"
 144
 145 struct qtextSMTP : sor<ranges<32, 33, 35, 91, 93, 126>, UTF8_non_ascii> {};
 146
 147 struct graphic : range<32, 126> {};
 148
 149 struct quoted_pairSMTP : seq<one<'\\'>, graphic> {};
 150
 151 struct qcontentSMTP : sor<qtextSMTP, quoted_pairSMTP> {};
 152
 153 struct quoted_string : seq<one<'"'>, plus<qcontentSMTP>, one<'"'>> {};
 154
 155 // excluded from atext are the “specials”: "()<>[]:;@\\,."
 156
 157 struct atext : sor<ALPHA, DIGIT,
 158                    one<'!', '#',
 159                        '$', '%',
 160                        '&', '\'',
 161                        '*', '+',
 162                        '-', '/',
 163                        '=', '?',
 164                        '^', '_',
 165                        '`', '{',
 166                        '|', '}',
 167                        '~'>,
 168                    UTF8_non_ascii> {};
 169
 170 struct atom : plus<atext> {};
 171
 172 struct dot_string : list<atom, dot> {};
 173
 174 struct local_part : sor<dot_string, quoted_string> {};
 175
 176 struct non_local_part : sor<domain, address_literal> {};
 177
 178 struct mailbox : seq<local_part, one<'@'>, non_local_part> {};
 179
 180 struct path : seq<one<'<'>, mailbox, one<'>'>> {};
 181
 182 struct bounce_path : TAO_PEGTL_ISTRING("<>") {};
 183
 184 struct reverse_path : sor<path, bounce_path> {};
 185
 186 struct magic_postmaster : TAO_PEGTL_ISTRING("<Postmaster>") {};
 187
 188 struct forward_path : sor<path, magic_postmaster> {};
 189
 190 struct esmtp_keyword : seq<sor<ALPHA, DIGIT>, star<sor<ALPHA, DIGIT, dash>>> {};
 191
 192 struct esmtp_value : plus<sor<range<33, 60>, range<62, 126>, UTF8_non_ascii>> {};
 193
 194 struct esmtp_param : seq<esmtp_keyword, opt<seq<one<'='>, esmtp_value>>> {};
 195
 196 struct mail_parameters : list<esmtp_param, SP> {};
 197
 198 struct rcpt_parameters : list<esmtp_param, SP> {};
 199
 200 struct string : sor<quoted_string, atom> {};
 201
 202 struct helo : seq<TAO_PEGTL_ISTRING("HELO"),
 203                   SP,
 204                   sor<domain, address_literal>,
 205                   CRLF> {};
 206
 207 struct ehlo : seq<TAO_PEGTL_ISTRING("EHLO"),
 208                   SP,
 209                   sor<domain, address_literal>,
 210                   CRLF> {};
 211
 212 struct mail_from : seq<TAO_PEGTL_ISTRING("MAIL"),
 213                        TAO_PEGTL_ISTRING(" FROM:"),
 214                        opt<SP>, // common enough error, we'll allow it
 215                        reverse_path,
 216                        opt<seq<SP, mail_parameters>>,
 217                        CRLF> {};
 218
 219 struct rcpt_to : seq<TAO_PEGTL_ISTRING("RCPT"),
 220                      TAO_PEGTL_ISTRING(" TO:"),
 221                      opt<SP>, // common error
 222                      forward_path,
 223                      opt<seq<SP, rcpt_parameters>>,
 224                      CRLF> {};
 225
 226 struct chunk_size : plus<DIGIT> {};
 227
 228 struct last : TAO_PEGTL_ISTRING("LAST") {};
 229
 230 struct bdat : seq<TAO_PEGTL_ISTRING("BDAT"), SP, chunk_size, CRLF> {};
 231
 232 struct bdat_last : seq<TAO_PEGTL_ISTRING("BDAT"), SP, chunk_size, SP, last, CRLF> {};
 233
 234 struct data : seq<TAO_PEGTL_ISTRING("DATA"), CRLF> {};
 235
 236 // ## below: DATA sub parse ##
 237
 238 struct data_end : seq<dot, CRLF> {};
 239
 240 struct data_blank : CRLF {};
 241
 242 // This particular crud will trigger an error return with the "no bare
 243 // LF" message.
 244
 245 struct data_not_end : seq<dot, LF> {};
 246
 247 struct data_also_not_end : seq<LF, dot, CRLF> {};
 248
 249
 250 // RFC 5321 text line length section 4.5.3.1.6.
 251 struct data_plain : seq<rep_min_max<1, 998, not_one<'\r', '\n'>>, CRLF> {};
 252
 253 struct data_dot : seq<one<'.'>, rep_min_max<1, 998, not_one<'\r', '\n'>>, CRLF> {};
 254
 255 struct data_long : seq<star<not_one<'\r', '\n'>>, CRLF> {};
 256
 257 struct data_line : seq<sor<data_blank,
 258                            data_not_end,
 259                            data_also_not_end,
 260                            data_dot,
 261                            data_plain,
 262                            data_long>,
 263                        discard> {};
 264
 265 struct data_grammar : until<data_end, data_line> {};
 266
 267 // ## above: DATA sub parse ##
 268
 269 struct rset : seq<TAO_PEGTL_ISTRING("RSET"), CRLF> {};
 270
 271 struct noop : seq<TAO_PEGTL_ISTRING("NOOP"), opt<seq<SP, string>>, CRLF> {};
 272
 273 struct vrfy : seq<TAO_PEGTL_ISTRING("VRFY"), opt<seq<SP, string>>, CRLF> {};
 274
 275 struct help : seq<TAO_PEGTL_ISTRING("HELP"), opt<seq<SP, string>>, CRLF> {};
 276
 277 struct starttls
 278     : seq<TAO_PEGTL_ISTRING("STAR"), TAO_PEGTL_ISTRING("TTLS"), CRLF> {};
 279
 280 struct quit : seq<TAO_PEGTL_ISTRING("QUIT"), CRLF> {};
 281
 282 // Anti-AUTH support
 283
 284 // base64-char     = ALPHA / DIGIT / "+" / "/"
 285 //                   ;; Case-sensitive
 286
 287 struct base64_char : sor<ALPHA, DIGIT, one<'+', '/'>> {};
 288
 289 // base64-terminal = (2base64-char "==") / (3base64-char "=")
 290
 291 struct base64_terminal : sor<seq<rep<2, base64_char>, TAO_PEGTL_ISTRING("==")>,
 292                              seq<rep<3, base64_char>, one<'='>>
 293                              > {};
 294
 295 // base64          = base64-terminal /
 296 //                   ( 1*(4base64-char) [base64-terminal] )
 297
 298 struct base64 : sor<base64_terminal,
 299                     seq<plus<rep<4, base64_char>>,
 300                         opt<base64_terminal>>
 301                     > {};
 302
 303 // initial-response= base64 / "="
 304
 305 struct initial_response : sor<base64, one<'='>> {};
 306
 307 // cancel-response = "*"
 308
 309 struct cancel_response : one<'*'> {};
 310
 311 struct UPPER_ALPHA : range<'A', 'Z'> {};
 312
 313 using HYPHEN = one<'-'>;
 314 using UNDERSCORE = one<'_'>;
 315
 316 struct mech_char : sor<UPPER_ALPHA, DIGIT, HYPHEN, UNDERSCORE> {};
 317 struct sasl_mech : rep_min_max<1, 20, mech_char> {};
 318
 319 // auth-command    = "AUTH" SP sasl-mech [SP initial-response]
 320 //                   *(CRLF [base64]) [CRLF cancel-response]
 321 //                   CRLF
 322 //                   ;; <sasl-mech> is defined in RFC 4422
 323
 324 struct auth : seq<TAO_PEGTL_ISTRING("AUTH"), SP, sasl_mech,
 325                   opt<seq<SP, initial_response>>,
 326                   // star<CRLF, opt<base64>>,
 327                   // opt<seq<CRLF, cancel_response>>,
 328                   CRLF> {};
 329 // bad commands:
 330
 331 struct bogus_cmd_short : seq<rep_min_max<0, 3, not_one<'\r', '\n'>>, CRLF> {};
 332 struct bogus_cmd_long : seq<rep_min_max<4, 1000, not_one<'\r', '\n'>>, CRLF> {};
 333
 334 // commands in size order
 335
 336 struct any_cmd : seq<sor<bogus_cmd_short,
 337                          data,
 338                          quit,
 339                          rset,
 340                          noop,
 341                          vrfy,
 342                          help,
 343                          helo,
 344                          ehlo,
 345                          bdat,
 346                          bdat_last,
 347                          starttls,
 348                          rcpt_to,
 349                          mail_from,
 350                          auth,
 351                          bogus_cmd_long>,
 352                      discard> {};
 353
 354 struct grammar : plus<any_cmd> {};
 355
 356 // clang-format on
 357
 358 template <typename Rule>
 359 struct action : nothing<Rule> {
 360 };
 361
 362 template <typename Rule>
 363 struct data_action : nothing<Rule> {
 364 };
 365
 366 template <>
 367 struct action<bogus_cmd_short> {
 368   template <typename Input>
 369   static void apply(Input const& in, Ctx& ctx)
 370   {
 371     LOG(INFO) << "bogus_cmd_short";
 372     ctx.session.cmd_unrecognized(in.string());
 373   }
 374 };
 375
 376 template <>
 377 struct action<bogus_cmd_long> {
 378   template <typename Input>
 379   static void apply(Input const& in, Ctx& ctx)
 380   {
 381     LOG(INFO) << "bogus_cmd_long";
 382     ctx.session.cmd_unrecognized(in.string());
 383   }
 384 };
 385
 386 template <>
 387 struct action<esmtp_keyword> {
 388   template <typename Input>
 389   static void apply(Input const& in, Ctx& ctx)
 390   {
 391     ctx.param.first = in.string();
 392   }
 393 };
 394
 395 template <>
 396 struct action<esmtp_value> {
 397   template <typename Input>
 398   static void apply(Input const& in, Ctx& ctx)
 399   {
 400     ctx.param.second = in.string();
 401   }
 402 };
 403
 404 template <>
 405 struct action<esmtp_param> {
 406   template <typename Input>
 407   static void apply(Input const& in, Ctx& ctx)
 408   {
 409     ctx.parameters.insert(ctx.param);
 410     ctx.param.first.clear();
 411     ctx.param.second.clear();
 412   }
 413 };
 414
 415 template <>
 416 struct action<local_part> {
 417   template <typename Input>
 418   static void apply(Input const& in, Ctx& ctx)
 419   {
 420     ctx.mb_loc = in.string();
 421     // RFC 5321, section 4.5.3.1.1.
 422     if (ctx.mb_loc.length() > 64) {
 423       LOG(WARNING) << "local part length == " << ctx.mb_loc.length();
 424     }
 425   }
 426 };
 427
 428 template <>
 429 struct action<non_local_part> {
 430   template <typename Input>
 431   static void apply(Input const& in, Ctx& ctx)
 432   {
 433     ctx.mb_dom = in.string();
 434     // RFC 5321, section 4.5.3.1.2.
 435     if (ctx.mb_dom.length() > 255) {
 436       LOG(WARNING) << "domain name or number too long " << ctx.mb_dom;
 437     }
 438   }
 439 };
 440
 441 template <>
 442 struct action<magic_postmaster> {
 443   static void apply0(Ctx& ctx)
 444   {
 445     ctx.mb_loc = std::string{"Postmaster"};
 446     ctx.mb_dom.clear();
 447   }
 448 };
 449
 450 template <>
 451 struct action<helo> {
 452   template <typename Input>
 453   static void apply(Input const& in, Ctx& ctx)
 454   {
 455     auto const b = begin(in) + 5; // +5 for the length of "HELO "
 456     auto const e = std::find(b, end(in) - 2, ' '); // -2 for the CRLF
 457     ctx.session.helo(std::string_view(b, e - b));
 458   }
 459 };
 460
 461 template <>
 462 struct action<ehlo> {
 463   template <typename Input>
 464   static void apply(Input const& in, Ctx& ctx)
 465   {
 466     auto const b = begin(in) + 5; // +5 for the length of "EHLO "
 467     auto const e = std::find(b, end(in) - 2, ' '); // -2 for the CRLF
 468     ctx.session.ehlo(std::string_view(b, e - b));
 469   }
 470 };
 471
 472 template <>
 473 struct action<mail_from> {
 474   static void apply0(Ctx& ctx)
 475   {
 476     ctx.session.mail_from(Mailbox{ctx.mb_loc, ctx.mb_dom}, ctx.parameters);
 477     ctx.mb_loc.clear();
 478     ctx.mb_dom.clear();
 479     ctx.parameters.clear();
 480   }
 481 };
 482
 483 template <>
 484 struct action<rcpt_to> {
 485   static void apply0(Ctx& ctx)
 486   {
 487     ctx.session.rcpt_to(Mailbox{ctx.mb_loc, ctx.mb_dom}, ctx.parameters);
 488     ctx.mb_loc.clear();
 489     ctx.mb_dom.clear();
 490     ctx.parameters.clear();
 491   }
 492 };
 493
 494 template <>
 495 struct action<chunk_size> {
 496   template <typename Input>
 497   static void apply(Input const& in, Ctx& ctx)
 498   {
 499     ctx.chunk_size = std::strtoull(in.string().c_str(), nullptr, 10);
 500   }
 501 };
 502
 503 void bdat_act(Ctx& ctx, bool last)
 504 {
 505   auto status_returned = false;
 506
 507   if (!ctx.session.bdat_start(ctx.chunk_size))
 508     status_returned = true;
 509
 510   auto to_xfer = ctx.chunk_size;
 511
 512   auto const bfr_size{std::min(to_xfer, std::streamsize(FLAGS_max_xfer_size))};
 513   iobuffer<char> bfr(bfr_size);
 514
 515   while (to_xfer) {
 516     auto const xfer_sz{std::min(to_xfer, bfr_size)};
 517
 518     ctx.session.in().read(bfr.data(), xfer_sz);
 519     if (!ctx.session.in()) {
 520       LOG(ERROR) << "attempt to read " << xfer_sz << " octets but only got "
 521                  << ctx.session.in().gcount();
 522       if (ctx.session.maxed_out()) {
 523         LOG(ERROR) << "input maxed out";
 524         if (!status_returned)
 525           ctx.session.bdat_size_error();
 526       }
 527       else if (ctx.session.timed_out()) {
 528         LOG(ERROR) << "input timed out";
 529         if (!status_returned)
 530           ctx.session.bdat_io_error();
 531       }
 532       else if (ctx.session.in().eof()) {
 533         LOG(ERROR) << "EOF in BDAT";
 534         if (!status_returned)
 535           ctx.session.bdat_io_error();
 536       }
 537       else {
 538         LOG(ERROR) << "I/O error in BDAT";
 539         if (!status_returned)
 540           ctx.session.bdat_io_error();
 541       }
 542       return;
 543     }
 544     if (!status_returned && !ctx.session.msg_write(bfr.data(), xfer_sz)) {
 545       status_returned = true;
 546     }
 547
 548     to_xfer -= xfer_sz;
 549   }
 550
 551   if (!status_returned) {
 552     ctx.session.bdat_done(ctx.chunk_size, last);
 553   }
 554 }
 555
 556 template <>
 557 struct action<bdat> {
 558   static void apply0(Ctx& ctx)
 559   {
 560     bdat_act(ctx, false);
 561   }
 562 };
 563
 564 template <>
 565 struct action<bdat_last> {
 566   static void apply0(Ctx& ctx)
 567   {
 568     bdat_act(ctx, true);
 569   }
 570 };
 571
 572 template <>
 573 struct data_action<data_end> {
 574   static void apply0(Ctx& ctx) { ctx.session.data_done(); }
 575 };
 576
 577 template <>
 578 struct data_action<data_blank> {
 579   static void apply0(Ctx& ctx)
 580   {
 581     constexpr char CRLF[]{'\r', '\n'};
 582     ctx.session.msg_write(CRLF, sizeof(CRLF));
 583   }
 584 };
 585
 586 template <>
 587 struct data_action<data_plain> {
 588   template <typename Input>
 589   static void apply(Input const& in, Ctx& ctx)
 590   {
 591     auto const len{end(in) - begin(in)};
 592     ctx.session.msg_write(begin(in), len);
 593   }
 594 };
 595
 596 template <>
 597 struct data_action<data_dot> {
 598   template <typename Input>
 599   static void apply(Input const& in, Ctx& ctx)
 600   {
 601     auto const len{end(in) - begin(in) - 1};
 602     ctx.session.msg_write(begin(in) + 1, len);
 603   }
 604 };
 605
 606 template <>
 607 struct data_action<data_long> {
 608   template <typename Input>
 609   static void apply(Input const& in, Ctx& ctx)
 610   {
 611     LOG(WARNING) << "garbage in data stream: \"" << esc(in.string()) << "\"";
 612     auto const len{end(in) - begin(in)};
 613     if (len)
 614       ctx.session.msg_write(begin(in), len);
 615     if (len > 1000) {
 616       LOG(WARNING) << "line too long at " << len << " octets";
 617     }
 618   }
 619 };
 620
 621 template <>
 622 struct data_action<data_not_end> {
 623   static void apply0(Ctx& ctx) __attribute__((noreturn))
 624   {
 625     ctx.session.bare_lf();
 626   }
 627 };
 628
 629 template <>
 630 struct data_action<data_also_not_end> {
 631   static void apply0(Ctx& ctx) __attribute__((noreturn))
 632   {
 633     ctx.session.bare_lf();
 634   }
 635 };
 636
 637 template <>
 638 struct action<data> {
 639   template <typename Input>
 640   static void apply(Input const& in, Ctx& ctx)
 641   {
 642     if (ctx.session.data_start()) {
 643       auto din = istream_input<eol::crlf, 1>(ctx.session.in(),
 644                                              FLAGS_data_bfr_size, "data");
 645       try {
 646         if (!parse_nested<RFC5321::data_grammar, RFC5321::data_action>(in, din,
 647                                                                        ctx)) {
 648           ctx.session.log_stats();
 649           if (!(ctx.session.maxed_out() || ctx.session.timed_out())) {
 650             ctx.session.error("bad DATA syntax");
 651           }
 652         }
 653         return;
 654       }
 655       catch (parse_error const& e) {
 656         LOG(WARNING) << e.what();
 657         ctx.session.error("unable to parse DATA stream");
 658       }
 659       catch (std::exception const& e) {
 660         LOG(WARNING) << e.what();
 661         ctx.session.error("unknown problem in DATA stream");
 662       }
 663     }
 664   }
 665 };
 666
 667 template <>
 668 struct action<rset> {
 669   static void apply0(Ctx& ctx) { ctx.session.rset(); }
 670 };
 671
 672 template <typename Input>
 673 std::string_view get_string_view(Input const& in)
 674 {
 675   auto const b   = begin(in) + 4;
 676   auto const len = end(in) - b;
 677   auto       str = std::string_view(b, len);
 678   if (str.front() == ' ')
 679     str.remove_prefix(1);
 680   return str;
 681 }
 682
 683 template <>
 684 struct action<noop> {
 685   template <typename Input>
 686   static void apply(Input const& in, Ctx& ctx)
 687   {
 688     auto const str = get_string_view(in);
 689     ctx.session.noop(str);
 690   }
 691 };
 692
 693 template <>
 694 struct action<vrfy> {
 695   template <typename Input>
 696   static void apply(Input const& in, Ctx& ctx)
 697   {
 698     auto const str = get_string_view(in);
 699     ctx.session.vrfy(str);
 700   }
 701 };
 702
 703 template <>
 704 struct action<help> {
 705   template <typename Input>
 706   static void apply(Input const& in, Ctx& ctx)
 707   {
 708     auto const str = get_string_view(in);
 709     ctx.session.help(str);
 710   }
 711 };
 712
 713 template <>
 714 struct action<starttls> {
 715   static void apply0(Ctx& ctx) { ctx.session.starttls(); }
 716 };
 717
 718 template <>
 719 struct action<quit> {
 720   static void apply0(Ctx& ctx) __attribute__((noreturn)) { ctx.session.quit(); }
 721 };
 722
 723 template <>
 724 struct action<auth> {
 725   static void apply0(Ctx& ctx) __attribute__((noreturn)) { ctx.session.auth(); }
 726 };
 727 } // namespace RFC5321
 728
 729 void timeout(int signum) __attribute__((noreturn));
 730 void timeout(int signum)
 731 {
 732   const char errmsg[] = "421 4.4.2 time-out\r\n";
 733   write(STDOUT_FILENO, errmsg, sizeof errmsg - 1);
 734   _Exit(1);
 735 }
 736
 737 void install_syscall_filter()
 738 {
 739   // scmp_filter_ctx ctx = CHECK_NOTNULL(seccomp_init(SCMP_ACT_ERRNO(EPERM)));
 740   scmp_filter_ctx ctx = CHECK_NOTNULL(seccomp_init(SCMP_ACT_LOG));
 741
 742   auto rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 0);
 743   CHECK_EQ(rc, 0) << "seccomp_rule_add write failed";
 744
 745   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 0);
 746   CHECK_EQ(rc, 0) << "seccomp_rule_add read failed";
 747
 748   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(close), 0);
 749   CHECK_EQ(rc, 0) << "seccomp_rule_add close failed";
 750
 751   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), 0);
 752   CHECK_EQ(rc, 0) << "seccomp_rule_add rt_sigprocmask failed";
 753
 754   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigreturn), 0);
 755   CHECK_EQ(rc, 0) << "seccomp_rule_add rt_sigreturn failed";
 756
 757   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigaction), 0);
 758   CHECK_EQ(rc, 0) << "seccomp_rule_add rt_sigaction failed";
 759
 760   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(newfstatat), 0);
 761   CHECK_EQ(rc, 0) << "seccomp_rule_add newfstatat failed";
 762
 763   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat), 0);
 764   CHECK_EQ(rc, 0) << "seccomp_rule_add openat failed";
 765
 766   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 0);
 767   CHECK_EQ(rc, 0) << "seccomp_rule_add socket failed";
 768
 769   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(connect), 0);
 770   CHECK_EQ(rc, 0) << "seccomp_rule_add connect failed";
 771
 772   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(poll), 0);
 773   CHECK_EQ(rc, 0) << "seccomp_rule_add poll failed";
 774
 775   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sendto), 0);
 776   CHECK_EQ(rc, 0) << "seccomp_rule_add sendto failed";
 777
 778   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(recvfrom), 0);
 779   CHECK_EQ(rc, 0) << "seccomp_rule_add recvfrom failed";
 780
 781   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sigaltstack), 0);
 782   CHECK_EQ(rc, 0) << "seccomp_rule_add sigaltstack failed";
 783
 784   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(prctl), 0);
 785   CHECK_EQ(rc, 0) << "seccomp_rule_add prctl failed";
 786
 787   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(gettid), 0);
 788   CHECK_EQ(rc, 0) << "seccomp_rule_add gettid failed";
 789
 790   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getpid), 0);
 791   CHECK_EQ(rc, 0) << "seccomp_rule_add getpid failed";
 792
 793   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getppid), 0);
 794   CHECK_EQ(rc, 0) << "seccomp_rule_add getppid failed";
 795
 796   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(newfstatat), 0);
 797   CHECK_EQ(rc, 0) << "seccomp_rule_add newfstatat failed";
 798
 799   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(dup), 0);
 800   CHECK_EQ(rc, 0) << "seccomp_rule_add dup failed";
 801
 802   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap), 0);
 803   CHECK_EQ(rc, 0) << "seccomp_rule_add mmap failed";
 804
 805   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(munmap), 0);
 806   CHECK_EQ(rc, 0) << "seccomp_rule_add munmap failed";
 807
 808   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(pipe2), 0);
 809   CHECK_EQ(rc, 0) << "seccomp_rule_add pipe2 failed";
 810
 811   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(readlinkat), 0);
 812   CHECK_EQ(rc, 0) << "seccomp_rule_add readlinkat failed";
 813
 814   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(pselect6), 0);
 815   CHECK_EQ(rc, 0) << "seccomp_rule_add pselect6 failed";
 816
 817   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(uname), 0);
 818   CHECK_EQ(rc, 0) << "seccomp_rule_add uname failed";
 819
 820   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl), 0);
 821   CHECK_EQ(rc, 0) << "seccomp_rule_add fcntl failed";
 822
 823   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(unlink), 0);
 824   CHECK_EQ(rc, 0) << "seccomp_rule_add unlink failed";
 825
 826   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(symlink), 0);
 827   CHECK_EQ(rc, 0) << "seccomp_rule_add symlink failed";
 828
 829   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(madvise), 0);
 830   CHECK_EQ(rc, 0) << "seccomp_rule_add madvise failed";
 831
 832   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 0);
 833   CHECK_EQ(rc, 0) << "seccomp_rule_add mprotect failed";
 834
 835   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), 0);
 836   CHECK_EQ(rc, 0) << "seccomp_rule_add futex failed";
 837
 838   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(writev), 0);
 839   CHECK_EQ(rc, 0) << "seccomp_rule_add writev failed";
 840
 841   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sysinfo), 0);
 842   CHECK_EQ(rc, 0) << "seccomp_rule_add sysinfo failed";
 843
 844   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(brk), 0);
 845   CHECK_EQ(rc, 0) << "seccomp_rule_add brk failed";
 846
 847   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getrandom), 0);
 848   CHECK_EQ(rc, 0) << "seccomp_rule_add getrandom failed";
 849
 850   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getdents64), 0);
 851   CHECK_EQ(rc, 0) << "seccomp_rule_add getdents64 failed";
 852
 853   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(lseek), 0);
 854   CHECK_EQ(rc, 0) << "seccomp_rule_add lseek failed";
 855
 856   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(setsockopt), 0);
 857   CHECK_EQ(rc, 0) << "seccomp_rule_add setsockopt failed";
 858
 859   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(alarm), 0);
 860   CHECK_EQ(rc, 0) << "seccomp_rule_add alarm failed";
 861
 862   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rename), 0);
 863   CHECK_EQ(rc, 0) << "seccomp_rule_add rename failed";
 864
 865   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(clock_gettime), 0);
 866   CHECK_EQ(rc, 0) << "seccomp_rule_add clock_gettime failed";
 867
 868   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit_group), 0);
 869   CHECK_EQ(rc, 0) << "seccomp_rule_add exit_group failed";
 870
 871   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit), 0);
 872   CHECK_EQ(rc, 0) << "seccomp_rule_add exit failed";
 873
 874   // for sanitize
 875
 876   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(clone), 0);
 877   CHECK_EQ(rc, 0) << "seccomp_rule_add clone failed";
 878
 879   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(wait4), 0);
 880   CHECK_EQ(rc, 0) << "seccomp_rule_add wait4 failed";
 881
 882   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sched_yield), 0);
 883   CHECK_EQ(rc, 0) << "seccomp_rule_add sched_yield failed";
 884
 885   rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ptrace), 0);
 886   CHECK_EQ(rc, 0) << "seccomp_rule_add ptrace failed";
 887
 888   rc = seccomp_load(ctx);
 889   CHECK_EQ(rc, 0) << "seccomp_load failed";
 890
 891   // seccomp_export_pfc(ctx, STDERR_FILENO);
 892
 893   seccomp_release(ctx);
 894 }
 895
 896 int main(int argc, char* argv[])
 897 {
 898   std::ios::sync_with_stdio(false);
 899
 900   { // Need to work with either namespace.
 901     using namespace gflags;
 902     using namespace google;
 903     ParseCommandLineFlags(&argc, &argv, true);
 904   }
 905
 906   // Set timeout signal handler to limit total run time.
 907   struct sigaction sact {};
 908   PCHECK(sigemptyset(&sact.sa_mask) == 0);
 909   sact.sa_flags   = 0;
 910   sact.sa_handler = timeout;
 911   PCHECK(sigaction(SIGALRM, &sact, nullptr) == 0);
 912
 913   auto const log_dir{getenv("GOOGLE_LOG_DIR")};
 914   if (log_dir) {
 915     error_code ec;
 916     fs::create_directories(log_dir, ec);
 917   }
 918
 919   google::InitGoogleLogging(argv[0]);
 920
 921   std::unique_ptr<RFC5321::Ctx> ctx;
 922
 923   // Don't wait for STARTTLS to fail if no cert.
 924   auto const config_path = osutil::get_config_dir();
 925   auto const certs = osutil::list_directory(config_path, Config::cert_fn_re);
 926   CHECK_GE(certs.size(), 1) << "no certs found";
 927
 928   auto const read_hook{[&ctx]() { ctx->session.flush(); }};
 929   ctx = std::make_unique<RFC5321::Ctx>(config_path, read_hook);
 930
 931   ctx->session.greeting();
 932
 933   install_syscall_filter();
 934
 935   istream_input<eol::crlf, 1> in{ctx->session.in(), FLAGS_cmd_bfr_size,
 936                                  "session"};
 937
 938   int ret = 0;
 939   try {
 940     ret = !parse<RFC5321::grammar, RFC5321::action>(in, *ctx);
 941   }
 942   catch (std::exception const& e) {
 943     LOG(WARNING) << e.what();
 944   }
 945
 946   if (ctx->session.maxed_out()) {
 947     ctx->session.max_out();
 948   }
 949   else if (ctx->session.timed_out()) {
 950     ctx->session.time_out();
 951   }
 952   // else {
 953   //   ctx->session.error("session end without QUIT command from client");
 954   // }
 955
 956   return ret;
 957 }