debian/patches/75_04-GnuTLS-Fix-client-detection-of-server-reject-of-clie.patch

   1 From c15523829ba17cce5829e2976aa1ff928965d948 Mon Sep 17 00:00:00 2001
   2 From: Jeremy Harris <jgh146exb@wizmail.org>
   3 Date: Sat, 16 Feb 2019 12:59:23 +0000
   4 Subject: [PATCH 7/7] GnuTLS: Fix client detection of server reject of client
   5  cert under TLS1.3
   6
   7 (cherry picked from commit fc243e944ec00b59b75f41d07494116f925d58b4)
   8 ---
   9  doc/ChangeLog         |  7 +++
  10  src/deliver.c             |  2 +-
  11  src/smtp_out.c            | 10 +++--
  12  src/tls-gnu.c             | 23 +++-------
  13  src/transports/lmtp.c     |  3 +-
  14  src/transports/smtp.c     | 81 +++++++++++++++++++++++++++--------
  15  test/confs/2027               |  8 ++--
  16  test/confs/5652               |  1 +
  17  test/confs/5821               |  2 +-
  18  test/log/2027                 |  2 +-
  19  test/runtest                  | 14 ++++++
  20  test/scripts/2000-GnuTLS/2027 |  2 +
  21  12 files changed, 111 insertions(+), 44 deletions(-)
  22
  23 diff --git a/doc/ChangeLog b/doc/ChangeLog
  24 index 66c8a7a1..867a1d8a 100644
  25 --- a/doc/ChangeLog
  26 +++ b/doc/ChangeLog
  27 @@ -11,6 +11,13 @@ Since version 4.92
  28  JH/06 Fix buggy handling of autoreply bounce_return_size_limit, and a possible
  29        buffer overrun for (non-chunking) other transports.
  30
  31 +JH/07 GnuTLS: Our use of late (post-handshake) certificate verification, under
  32 +      TLS1.3, means that a server rejecting a client certificate is not visible
  33 +      to the client until the first read of encrypted data (typically the
  34 +      response to EHLO).  Add detection for that case and treat it as a failed
  35 +      TLS connection attempt, so that the normal retry-in-clear can work (if
  36 +      suitably configured).
  37 +
  38
  39  Exim version 4.92
  40  -----------------
  41 diff --git a/src/deliver.c b/src/deliver.c
  42 index 664d0045..e1799411 100644
  43 --- a/src/deliver.c
  44 +++ b/src/deliver.c
  45 @@ -7433,7 +7433,7 @@ if (addr_senddsn)
  46
  47      tctx.u.fd = fd;
  48      tctx.options = topt_add_return_path | topt_no_body;
  49 -    /*XXX hmm, retval ignored.
  50 +    /*XXX hmm, FALSE(fail) retval ignored.
  51      Could error for any number of reasons, and they are not handled. */
  52      transport_write_message(&tctx, 0);
  53      fflush(f);
  54 diff --git a/src/smtp_out.c b/src/smtp_out.c
  55 index 9bd90c77..b194e804 100644
  56 --- a/src/smtp_out.c
  57 +++ b/src/smtp_out.c
  58 @@ -688,20 +688,22 @@ Returns:    TRUE if a valid, non-error response was received; else FALSE
  59  /*XXX could move to smtp transport; no other users */
  60
  61  BOOL
  62 -smtp_read_response(void * sx0, uschar *buffer, int size, int okdigit,
  63 +smtp_read_response(void * sx0, uschar * buffer, int size, int okdigit,
  64     int timeout)
  65  {
  66  smtp_context * sx = sx0;
  67 -uschar *ptr = buffer;
  68 -int count = 0;
  69 +uschar * ptr = buffer;
  70 +int count = 0, rc;
  71
  72  errno = 0;  /* Ensure errno starts out zero */
  73
  74  #ifdef EXPERIMENTAL_PIPE_CONNECT
  75  if (sx->pending_BANNER || sx->pending_EHLO)
  76 -  if (smtp_reap_early_pipe(sx, &count) != OK)
  77 +  if ((rc = smtp_reap_early_pipe(sx, &count)) != OK)
  78      {
  79      DEBUG(D_transport) debug_printf("failed reaping pipelined cmd responsess\n");
  80 +    buffer[0] = '\0';
  81 +    if (rc == DEFER) errno = ERRNO_TLSFAILURE;
  82      return FALSE;
  83      }
  84  #endif
  85 diff --git a/src/tls-gnu.c b/src/tls-gnu.c
  86 index c404dc29..de2d70c0 100644
  87 --- a/src/tls-gnu.c
  88 +++ b/src/tls-gnu.c
  89 @@ -229,7 +229,7 @@ static gnutls_dh_params_t dh_server_params = NULL;
  90
  91  static const int ssl_session_timeout = 200;
  92
  93 -static const char * const exim_default_gnutls_priority = "NORMAL";
  94 +static const uschar * const exim_default_gnutls_priority = US"NORMAL";
  95
  96  /* Guard library core initialisation */
  97
  98 @@ -1278,7 +1278,6 @@ int rc;
  99  size_t sz;
 100  const char *errpos;
 101  uschar *p;
 102 -BOOL want_default_priorities;
 103
 104  if (!exim_gnutls_base_init_done)
 105    {
 106 @@ -1387,32 +1386,24 @@ and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols.
 107  This was backwards incompatible, but means Exim no longer needs to track
 108  all algorithms and provide string forms for them. */
 109
 110 -want_default_priorities = TRUE;
 111 -
 112 +p = NULL;
 113  if (state->tls_require_ciphers && *state->tls_require_ciphers)
 114    {
 115    if (!expand_check_tlsvar(tls_require_ciphers, errstr))
 116      return DEFER;
 117    if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers)
 118      {
 119 -    DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n",
 120 -        state->exp_tls_require_ciphers);
 121 -
 122 -    rc = gnutls_priority_init(&state->priority_cache,
 123 -        CS state->exp_tls_require_ciphers, &errpos);
 124 -    want_default_priorities = FALSE;
 125      p = state->exp_tls_require_ciphers;
 126 +    DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", p);
 127      }
 128    }
 129 -if (want_default_priorities)
 130 +if (!p)
 131    {
 132 +  p = exim_default_gnutls_priority;
 133    DEBUG(D_tls)
 134 -    debug_printf("GnuTLS using default session cipher/priority \"%s\"\n",
 135 -        exim_default_gnutls_priority);
 136 -  rc = gnutls_priority_init(&state->priority_cache,
 137 -      exim_default_gnutls_priority, &errpos);
 138 -  p = US exim_default_gnutls_priority;
 139 +    debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", p);
 140    }
 141 +rc = gnutls_priority_init(&state->priority_cache, CCS p, &errpos);
 142
 143  exim_gnutls_err_check(rc, string_sprintf(
 144        "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"",
 145 diff --git a/src/transports/lmtp.c b/src/transports/lmtp.c
 146 index 240d78b2..57b346d4 100644
 147 --- a/src/transports/lmtp.c
 148 +++ b/src/transports/lmtp.c
 149 @@ -122,7 +122,8 @@ Arguments:
 150  Returns:       TRUE if a "QUIT" command should be sent, else FALSE
 151  */
 152
 153 -static BOOL check_response(int *errno_value, int more_errno, uschar *buffer,
 154 +static BOOL
 155 +check_response(int *errno_value, int more_errno, uschar *buffer,
 156    int *yield, uschar **message)
 157  {
 158  *yield = '4';    /* Default setting is to give a temporary error */
 159 diff --git a/src/transports/smtp.c b/src/transports/smtp.c
 160 index a351da84..bfd6018d 100644
 161 --- a/src/transports/smtp.c
 162 +++ b/src/transports/smtp.c
 163 @@ -594,6 +594,11 @@ switch(*errno_value)
 164           pl, smtp_command, s);
 165      return FALSE;
 166
 167 +  case ERRNO_TLSFAILURE:       /* Handle bad first read; can happen with
 168 +                               GnuTLS and TLS1.3 */
 169 +    *message = US"bad first read from TLS conn";
 170 +    return TRUE;
 171 +
 172    case ERRNO_FILTER_FAIL:      /* Handle a failed filter process error;
 173                           can't send QUIT as we mustn't end the DATA. */
 174      *message = string_sprintf("transport filter process failed (%d)%s",
 175 @@ -942,6 +947,7 @@ Arguments:
 176
 177  Return:
 178   OK    all well
 179 + DEFER error on first read of TLS'd conn
 180   FAIL  SMTP error in response
 181  */
 182  int
 183 @@ -949,6 +955,7 @@ smtp_reap_early_pipe(smtp_context * sx, int * countp)
 184  {
 185  BOOL pending_BANNER = sx->pending_BANNER;
 186  BOOL pending_EHLO = sx->pending_EHLO;
 187 +int rc = FAIL;
 188
 189  sx->pending_BANNER = FALSE;    /* clear early to avoid recursion */
 190  sx->pending_EHLO = FALSE;
 191 @@ -960,6 +967,7 @@ if (pending_BANNER)
 192    if (!smtp_reap_banner(sx))
 193      {
 194      DEBUG(D_transport) debug_printf("bad banner\n");
 195 +    if (tls_out.active.sock >= 0) rc = DEFER;
 196      goto fail;
 197      }
 198    }
 199 @@ -974,6 +982,7 @@ if (pending_EHLO)
 200    if (!smtp_reap_ehlo(sx))
 201      {
 202      DEBUG(D_transport) debug_printf("bad response for EHLO\n");
 203 +    if (tls_out.active.sock >= 0) rc = DEFER;
 204      goto fail;
 205      }
 206
 207 @@ -1011,7 +1020,7 @@ return OK;
 208  fail:
 209    invalidate_ehlo_cache_entry(sx);
 210    (void) smtp_discard_responses(sx, sx->conn_args.ob, *countp);
 211 -  return FAIL;
 212 +  return rc;
 213  }
 214  #endif
 215
 216 @@ -1056,6 +1065,7 @@ Returns:      3 if at least one address had 2xx and one had 5xx
 217               -2 I/O or other non-response error for RCPT
 218               -3 DATA or MAIL failed - errno and buffer set
 219              -4 banner or EHLO failed (early-pipelining)
 220 +            -5 banner or EHLO failed (early-pipelining, TLS)
 221  */
 222
 223  static int
 224 @@ -1064,10 +1074,11 @@ sync_responses(smtp_context * sx, int count, int pending_DATA)
 225  address_item * addr = sx->sync_addr;
 226  smtp_transport_options_block * ob = sx->conn_args.ob;
 227  int yield = 0;
 228 +int rc;
 229
 230  #ifdef EXPERIMENTAL_PIPE_CONNECT
 231 -if (smtp_reap_early_pipe(sx, &count) != OK)
 232 -  return -4;
 233 +if ((rc = smtp_reap_early_pipe(sx, &count)) != OK)
 234 +  return rc == FAIL ? -4 : -5;
 235  #endif
 236
 237  /* Handle the response for a MAIL command. On error, reinstate the original
 238 @@ -1083,6 +1094,8 @@ if (sx->pending_MAIL)
 239      {
 240      DEBUG(D_transport) debug_printf("bad response for MAIL\n");
 241      Ustrcpy(big_buffer, mail_command);  /* Fits, because it came from there! */
 242 +    if (errno == ERRNO_TLSFAILURE)
 243 +      return -5;
 244      if (errno == 0 && sx->buffer[0] != 0)
 245        {
 246        int save_errno = 0;
 247 @@ -1141,6 +1154,11 @@ while (count-- > 0)
 248        }
 249      }
 250
 251 +  /* Error on first TLS read */
 252 +
 253 +  else if (errno == ERRNO_TLSFAILURE)
 254 +    return -5;
 255 +
 256    /* Timeout while reading the response */
 257
 258    else if (errno == ETIMEDOUT)
 259 @@ -1253,6 +1271,10 @@ if (pending_DATA != 0)
 260      int code;
 261      uschar *msg;
 262      BOOL pass_message;
 263 +
 264 +    if (errno == ERRNO_TLSFAILURE)     /* Error on first TLS read */
 265 +      return -5;
 266 +
 267      if (pending_DATA > 0 || (yield & 1) != 0)
 268        {
 269        if (errno == 0 && sx->buffer[0] == '4')
 270 @@ -1802,7 +1824,9 @@ Args:
 271     tc_chunk_last       add LAST option to SMTP BDAT command
 272     tc_reap_prev                reap response to previous SMTP commands
 273
 274 -Returns:       OK or ERROR
 275 +Returns:
 276 +  OK or ERROR
 277 +  DEFER                        TLS error on first read (EHLO-resp); errno set
 278  */
 279
 280  static int
 281 @@ -1859,10 +1883,12 @@ if (flags & tc_reap_prev  &&  prev_cmd_count > 0)
 282      case 2: sx->completed_addr = TRUE; /* 5xx (only) => progress made */
 283      case 0: break;                     /* No 2xx or 5xx, but no probs */
 284
 285 -    case -1:                           /* Timeout on RCPT */
 286 +    case -5: errno = ERRNO_TLSFAILURE;
 287 +            return DEFER;
 288  #ifdef EXPERIMENTAL_PIPE_CONNECT
 289      case -4:                           /* non-2xx for pipelined banner or EHLO */
 290  #endif
 291 +    case -1:                           /* Timeout on RCPT */
 292      default: return ERROR;             /* I/O error, or any MAIL/DATA error */
 293      }
 294    cmd_count = 1;
 295 @@ -1933,6 +1959,9 @@ BOOL pass_message = FALSE;
 296  uschar * message = NULL;
 297  int yield = OK;
 298  int rc;
 299 +#ifdef SUPPORT_TLS
 300 +uschar * tls_errstr;
 301 +#endif
 302
 303  sx->conn_args.ob = ob;
 304
 305 @@ -2474,27 +2503,27 @@ if (  smtp_peer_options & OPTION_TLS
 306    TLS_NEGOTIATE:
 307      {
 308      address_item * addr;
 309 -    uschar * errstr;
 310      sx->cctx.tls_ctx = tls_client_start(sx->cctx.sock, sx->conn_args.host,
 311                             sx->addrlist, sx->conn_args.tblock,
 312  # ifdef SUPPORT_DANE
 313                              sx->dane ? &tlsa_dnsa : NULL,
 314  # endif
 315 -                            &tls_out, &errstr);
 316 +                            &tls_out, &tls_errstr);
 317
 318      if (!sx->cctx.tls_ctx)
 319        {
 320        /* TLS negotiation failed; give an error. From outside, this function may
 321        be called again to try in clear on a new connection, if the options permit
 322        it for this host. */
 323 -      DEBUG(D_tls) debug_printf("TLS session fail: %s\n", errstr);
 324 +GNUTLS_CONN_FAILED:
 325 +      DEBUG(D_tls) debug_printf("TLS session fail: %s\n", tls_errstr);
 326
 327  # ifdef SUPPORT_DANE
 328        if (sx->dane)
 329          {
 330         log_write(0, LOG_MAIN,
 331           "DANE attempt failed; TLS connection to %s [%s]: %s",
 332 -         sx->conn_args.host->name, sx->conn_args.host->address, errstr);
 333 +         sx->conn_args.host->name, sx->conn_args.host->address, tls_errstr);
 334  #  ifndef DISABLE_EVENT
 335         (void) event_raise(sx->conn_args.tblock->event_action,
 336           US"dane:fail", US"validation-failure");       /* could do with better detail */
 337 @@ -2503,7 +2532,7 @@ if (  smtp_peer_options & OPTION_TLS
 338  # endif
 339
 340        errno = ERRNO_TLSFAILURE;
 341 -      message = string_sprintf("TLS session: %s", errstr);
 342 +      message = string_sprintf("TLS session: %s", tls_errstr);
 343        sx->send_quit = FALSE;
 344        goto TLS_FAILED;
 345        }
 346 @@ -2601,7 +2630,22 @@ if (tls_out.active.sock >= 0)
 347  #endif
 348      {
 349      if (!smtp_reap_ehlo(sx))
 350 +#ifdef USE_GNUTLS
 351 +      {
 352 +      /* The GnuTLS layer in Exim only spots a server-rejection of a client
 353 +      cert late, under TLS1.3 - which means here; the first time we try to
 354 +      receive crypted data.  Treat it as if it was a connect-time failure.
 355 +      See also the early-pipe equivalent... which will be hard; every call
 356 +      to sync_responses will need to check the result.
 357 +      It would be nicer to have GnuTLS check the cert during the handshake.
 358 +      Can it do that, with all the flexibility we need? */
 359 +
 360 +      tls_errstr = US"error on first read";
 361 +      goto GNUTLS_CONN_FAILED;
 362 +      }
 363 +#else
 364        goto RESPONSE_FAILED;
 365 +#endif
 366      smtp_peer_options = 0;
 367      }
 368    }
 369 @@ -3261,6 +3305,7 @@ for (addr = sx->first_addr, address_count = 0;
 370
 371  #ifdef EXPERIMENTAL_PIPE_CONNECT
 372        case -4: return -1;                      /* non-2xx for pipelined banner or EHLO */
 373 +      case -5: return -1;                      /* TLS first-read error */
 374  #endif
 375        }
 376      sx->pending_MAIL = FALSE;            /* Dealt with MAIL */
 377 @@ -3589,11 +3634,12 @@ if (  !(sx.peer_offered & OPTION_CHUNKING)
 378
 379      case 1: sx.ok = TRUE;            /* 2xx (only) => OK, but if LMTP, */
 380      if (!sx.lmtp) sx.completed_addr = TRUE; /* can't tell about progress yet */
 381 -    case 0: break;                       /* No 2xx or 5xx, but no probs */
 382 +    case 0: break;                     /* No 2xx or 5xx, but no probs */
 383
 384 -    case -1: goto END_OFF;               /* Timeout on RCPT */
 385 +    case -1: goto END_OFF;             /* Timeout on RCPT */
 386
 387  #ifdef EXPERIMENTAL_PIPE_CONNECT
 388 +    case -5:                           /* TLS first-read error */
 389      case -4:  HDEBUG(D_transport)
 390                 debug_printf("failed reaping pipelined cmd responses\n");
 391  #endif
 392 @@ -3730,19 +3776,20 @@ else
 393        {
 394        case 3: sx.ok = TRUE;            /* 2xx & 5xx => OK & progress made */
 395        case 2: sx.completed_addr = TRUE;    /* 5xx (only) => progress made */
 396 -      break;
 397 +             break;
 398
 399 -      case 1: sx.ok = TRUE;            /* 2xx (only) => OK, but if LMTP, */
 400 +      case 1: sx.ok = TRUE;            /* 2xx (only) => OK, but if LMTP, */
 401        if (!sx.lmtp) sx.completed_addr = TRUE; /* can't tell about progress yet */
 402 -      case 0: break;                       /* No 2xx or 5xx, but no probs */
 403 +      case 0: break;                   /* No 2xx or 5xx, but no probs */
 404
 405 -      case -1: goto END_OFF;               /* Timeout on RCPT */
 406 +      case -1: goto END_OFF;           /* Timeout on RCPT */
 407
 408  #ifdef EXPERIMENTAL_PIPE_CONNECT
 409 +      case -5:                         /* TLS first-read error */
 410        case -4:  HDEBUG(D_transport)
 411                   debug_printf("failed reaping pipelined cmd responses\n");
 412  #endif
 413 -      default: goto RESPONSE_FAILED;       /* I/O error, or any MAIL/DATA error */
 414 +      default: goto RESPONSE_FAILED;   /* I/O error, or any MAIL/DATA error */
 415        }
 416      }
 417
 418 --
 419 2.20.1
 420