Revert "Show the DNSSEC status (ad=) always in -bt/-bv output"
[exim.git] / src / src / verify.c
index 4474f2c5bed908514254e7646cd360eb7037c303..e00e7b9eba828f4dbfc5512496a8d971041f1e85 100644 (file)
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) University of Cambridge 1995 - 2014 */
+/* Copyright (c) University of Cambridge 1995 - 2015 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions concerned with verifying things. The original code for callout
@@ -58,7 +58,7 @@ Returns:            the cache record if a non-expired one exists, else NULL
 */
 
 static dbdata_callout_cache *
-get_callout_cache_record(open_db *dbm_file, uschar *key, uschar *type,
+get_callout_cache_record(open_db *dbm_file, const uschar *key, uschar *type,
   int positive_expire, int negative_expire)
 {
 BOOL negative;
@@ -70,7 +70,7 @@ cache_record = dbfn_read_with_length(dbm_file, key, &length);
 
 if (cache_record == NULL)
   {
-  HDEBUG(D_verify) debug_printf("callout cache: no %s record found\n", type);
+  HDEBUG(D_verify) debug_printf("callout cache: no %s record found for %s\n", type, key);
   return NULL;
   }
 
@@ -84,7 +84,7 @@ now = time(NULL);
 
 if (now - cache_record->time_stamp > expire)
   {
-  HDEBUG(D_verify) debug_printf("callout cache: %s record expired\n", type);
+  HDEBUG(D_verify) debug_printf("callout cache: %s record expired for %s\n", type, key);
   return NULL;
   }
 
@@ -111,7 +111,7 @@ if (type[0] == 'd' && cache_record->result != ccache_reject)
     cache_record->random_result = ccache_unknown;
   }
 
-HDEBUG(D_verify) debug_printf("callout cache: found %s record\n", type);
+HDEBUG(D_verify) debug_printf("callout cache: found %s record for %s\n", type, key);
 return cache_record;
 }
 
@@ -164,7 +164,7 @@ BOOL done = FALSE;
 uschar *address_key;
 uschar *from_address;
 uschar *random_local_part = NULL;
-uschar *save_deliver_domain = deliver_domain;
+const uschar *save_deliver_domain = deliver_domain;
 uschar **failure_ptr = is_recipient?
   &recipient_verify_failure : &sender_verify_failure;
 open_db dbblock;
@@ -173,6 +173,9 @@ dbdata_callout_cache new_domain_record;
 dbdata_callout_cache_address new_address_record;
 host_item *host;
 time_t callout_start_time;
+#ifdef EXPERIMENTAL_INTERNATIONAL
+BOOL utf8_offered = FALSE;
+#endif
 
 new_domain_record.result = ccache_unknown;
 new_domain_record.postmaster_result = ccache_unknown;
@@ -388,12 +391,9 @@ else
   log the fact, but carry on without randomming. */
 
   if (callout_random && callout_random_local_part != NULL)
-    {
-    random_local_part = expand_string(callout_random_local_part);
-    if (random_local_part == NULL)
+    if (!(random_local_part = expand_string(callout_random_local_part)))
       log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
         "callout_random_local_part: %s", expand_string_message);
-    }
 
   /* Default the connect and overall callout timeouts if not set, and record the
   time we are starting so that we can enforce it. */
@@ -535,6 +535,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
     uschar *interface = NULL;  /* Outgoing interface to use; NULL => any */
 #if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_DANE)
     BOOL dane = FALSE;
+    BOOL dane_required;
     dns_answer tlsa_dnsa;
 #endif
     uschar inbuffer[4096];
@@ -577,9 +578,10 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
     deliver_domain = addr->domain;
     transport_name = addr->transport->name;
 
-    if (!smtp_get_interface(tf->interface, host_af, addr, NULL, &interface,
-            US"callout") ||
-        !smtp_get_port(tf->port, addr, &port, US"callout"))
+    if (  !smtp_get_interface(tf->interface, host_af, addr, NULL, &interface,
+            US"callout")
+       || !smtp_get_port(tf->port, addr, &port, US"callout")
+       )
       log_write(0, LOG_MAIN|LOG_PANIC, "<%s>: %s", addr->address,
         addr->message);
 
@@ -590,36 +592,6 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 
     HDEBUG(D_verify) debug_printf("interface=%s port=%d\n", interface, port);
 
-#if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_DANE)
-      {
-      BOOL dane_required;
-      int rc;
-
-      tls_out.dane_verified = FALSE;
-      tls_out.tlsa_usage = 0;
-
-      dane_required =
-       verify_check_given_host(&ob->hosts_require_dane, host) == OK;
-
-      if (host->dnssec == DS_YES)
-       {
-       if(  dane_required
-         || verify_check_given_host(&ob->hosts_try_dane, host) == OK
-         )
-         if ((rc = tlsa_lookup(host, &tlsa_dnsa, dane_required, &dane)) != OK)
-           return rc;
-       }
-      else if (dane_required)
-       {
-       log_write(0, LOG_MAIN, "DANE error: %s lookup not DNSSEC", host->name);
-       return FAIL;
-       }
-
-      if (dane)
-       ob->tls_tempfail_tryclear = FALSE;
-      }
-#endif  /*DANE*/
-
     /* Set up the buffer for reading SMTP response packets. */
 
     inblock.buffer = inbuffer;
@@ -635,22 +607,17 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
     outblock.cmd_count = 0;
     outblock.authenticating = FALSE;
 
-    /* Reset the parameters of a TLS session */
-    tls_out.cipher = tls_out.peerdn = NULL;
-
     /* Connect to the host; on failure, just loop for the next one, but we
     set the error for the last one. Use the callout_connect timeout. */
 
     tls_retry_connection:
 
+    /* Reset the parameters of a TLS session */
+    tls_out.cipher = tls_out.peerdn = tls_out.peercert = NULL;
+
     inblock.sock = outblock.sock =
-      smtp_connect(host, host_af, port, interface, callout_connect, TRUE, NULL
-#ifdef EXPERIMENTAL_EVENT
-    /*XXX event action? NULL for now. */
-                 , NULL
-#endif
-                 );
-    /* reconsider DSCP here */
+      smtp_connect(host, host_af, port, interface, callout_connect,
+                 addr->transport);
     if (inblock.sock < 0)
       {
       addr->message = string_sprintf("could not connect to %s [%s]: %s",
@@ -661,6 +628,36 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
       continue;
       }
 
+#if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_DANE)
+      {
+      int rc;
+
+      tls_out.dane_verified = FALSE;
+      tls_out.tlsa_usage = 0;
+
+      dane_required =
+       verify_check_given_host(&ob->hosts_require_dane, host) == OK;
+
+      if (host->dnssec == DS_YES)
+       {
+       if(  (  dane_required
+            || verify_check_given_host(&ob->hosts_try_dane, host) == OK
+            )
+         && (rc = tlsa_lookup(host, &tlsa_dnsa, dane_required, &dane)) != OK
+         )
+         return rc;
+       }
+      else if (dane_required)
+       {
+       log_write(0, LOG_MAIN, "DANE error: %s lookup not DNSSEC", host->name);
+       return FAIL;
+       }
+
+      if (dane)
+       ob->tls_tempfail_tryclear = FALSE;
+      }
+#endif  /*DANE*/
+
     /* Expand the helo_data string to find the host name to use. */
 
     if (tf->helo_data != NULL)
@@ -704,7 +701,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
       }
 
     /* Not worth checking greeting line for ESMTP support */
-    if (!(esmtp = verify_check_given_host(&(ob->hosts_avoid_esmtp), host) != OK))
+    if (!(esmtp = verify_check_given_host(&ob->hosts_avoid_esmtp, host) != OK))
       DEBUG(D_transport)
         debug_printf("not sending EHLO (host matches hosts_avoid_esmtp)\n");
 
@@ -797,6 +794,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
        int oldtimeout = ob->command_timeout;
        int rc;
 
+       tls_negotiate:
        ob->command_timeout = callout;
         rc = tls_client_start(inblock.sock, host, addr, addr->transport
 # ifdef EXPERIMENTAL_DANE
@@ -805,26 +803,44 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
                            );
        ob->command_timeout = oldtimeout;
 
-        /* TLS negotiation failed; give an error.  Try in clear on a new connection,
-           if the options permit it for this host. */
+        /* TLS negotiation failed; give an error.  Try in clear on a new
+       connection, if the options permit it for this host. */
         if (rc != OK)
           {
-         if (  rc == DEFER
-            && ob->tls_tempfail_tryclear
-            && !smtps
-            && verify_check_given_host(&ob->hosts_require_tls, host) != OK
-            )
+         if (rc == DEFER)
            {
            (void)close(inblock.sock);
 # ifdef EXPERIMENTAL_EVENT
            (void) event_raise(addr->transport->event_action,
                                    US"tcp:close", NULL);
 # endif
-           log_write(0, LOG_MAIN, "TLS session failure: delivering unencrypted "
-             "to %s [%s] (not in hosts_require_tls)", host->name, host->address);
-           suppress_tls = TRUE;
-           goto tls_retry_connection;
+# ifdef EXPERIMENTAL_DANE
+           if (dane)
+             {
+             if (!dane_required)
+               {
+               log_write(0, LOG_MAIN, "DANE attempt failed;"
+                 " trying CA-root TLS to %s [%s] (not in hosts_require_dane)",
+                 host->name, host->address);
+               dane = FALSE;
+               goto tls_negotiate;
+               }
+             }
+           else
+# endif
+             if (  ob->tls_tempfail_tryclear
+                && !smtps
+                && verify_check_given_host(&ob->hosts_require_tls, host) != OK
+                )
+             {
+             log_write(0, LOG_MAIN, "TLS session failure:"
+               " delivering unencrypted to %s [%s] (not in hosts_require_tls)",
+               host->name, host->address);
+             suppress_tls = TRUE;
+             goto tls_retry_connection;
+             }
            }
+
          /*save_errno = ERRNO_TLSFAILURE;*/
          /*message = US"failure while setting up TLS session";*/
          send_quit = FALSE;
@@ -907,6 +923,40 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
         }
       }
 
+#ifdef EXPERIMENTAL_INTERNATIONAL
+    else if (  addr->prop.utf8_msg
+           && !addr->prop.utf8_downcvt
+           && !(  esmtp
+               && (  regex_UTF8
+                  || ( (regex_UTF8 = regex_must_compile(
+                         US"\\n250[\\s\\-]SMTPUTF8(\\s|\\n|$)", FALSE, TRUE)),
+                     TRUE
+                  )  )
+               && (  (utf8_offered = pcre_exec(regex_UTF8, NULL,
+                           CS responsebuffer, Ustrlen(responsebuffer),
+                           0, PCRE_EOPT, NULL, 0) >= 0)
+                  || addr->prop.utf8_downcvt_maybe
+           )   )  )
+      {
+      HDEBUG(D_acl|D_v) debug_printf("utf8 required but not offered\n");
+      errno = ERRNO_UTF8_FWD;
+      setflag(addr, af_verify_nsfail);
+      done = FALSE;
+      }
+    else if (  addr->prop.utf8_msg
+           && (addr->prop.utf8_downcvt || !utf8_offered)
+           && (setflag(addr, af_utf8_downcvt),
+               from_address = string_address_utf8_to_alabel(from_address,
+                                     &addr->message),
+               addr->message
+           )  )
+      {
+      errno = ERRNO_EXPANDFAIL;
+      setflag(addr, af_verify_nsfail);
+      done = FALSE;
+      }
+#endif
+
     /* If we haven't authenticated, but are required to, give up. */
     /* Try to AUTH */
 
@@ -924,7 +974,13 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
       ( (addr->auth_sndr = client_authenticated_sender),
 
     /* Send the MAIL command */
-        (smtp_write_command(&outblock, FALSE, "MAIL FROM:<%s>%s\r\n",
+        (smtp_write_command(&outblock, FALSE,
+#ifdef EXPERIMENTAL_INTERNATIONAL
+         addr->prop.utf8_msg && !addr->prop.utf8_downcvt
+         ? "MAIL FROM:<%s>%s SMTPUTF8\r\n"
+         :
+#endif
+           "MAIL FROM:<%s>%s\r\n",
           from_address, responsebuffer) >= 0)
       )  &&
 
@@ -963,6 +1019,23 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 
     else
       {
+      const uschar * rcpt_domain = addr->domain;
+
+#ifdef EXPERIMENTAL_INTERNATIONAL
+      uschar * errstr = NULL;
+      if (  testflag(addr, af_utf8_downcvt)
+        && (rcpt_domain = string_domain_utf8_to_alabel(rcpt_domain,
+                                   &errstr), errstr)
+        )
+       {
+       addr->message = errstr;
+       errno = ERRNO_EXPANDFAIL;
+       setflag(addr, af_verify_nsfail);
+       done = FALSE;
+       rcpt_domain = US"";  /*XXX errorhandling! */
+       }
+#endif
+
       new_domain_record.result =
         (old_domain_cache_result == ccache_reject_mfnull)?
           ccache_reject_mfnull: ccache_accept;
@@ -975,7 +1048,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
         BOOL random_ok =
           smtp_write_command(&outblock, FALSE,
             "RCPT TO:<%.1000s@%.1000s>\r\n", random_local_part,
-            addr->domain) >= 0 &&
+            rcpt_domain) >= 0 &&
           smtp_read_response(&inblock, randombuffer,
             sizeof(randombuffer), '2', callout);
 
@@ -990,10 +1063,15 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 
         /* Otherwise, cache a real negative response, and get back to the right
         state to send RCPT. Unless there's some problem such as a dropped
-        connection, we expect to succeed, because the commands succeeded above. */
+        connection, we expect to succeed, because the commands succeeded above.
+       However, some servers drop the connection after responding to  an
+       invalid recipient, so on (any) error we drop and remake the connection.
+       */
 
         else if (errno == 0)
           {
+         /* This would be ok for 1st rcpt a cutthrough, but no way to
+         handle a subsequent.  So refuse to support any */
          cancel_cutthrough_connection("random-recipient");
 
           if (randombuffer[0] == '5')
@@ -1004,10 +1082,32 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
             smtp_read_response(&inblock, responsebuffer, sizeof(responsebuffer),
               '2', callout) &&
 
-            smtp_write_command(&outblock, FALSE, "MAIL FROM:<%s>\r\n",
+            smtp_write_command(&outblock, FALSE,
+#ifdef EXPERIMENTAL_INTERNATIONAL
+             addr->prop.utf8_msg && !addr->prop.utf8_downcvt
+             ? "MAIL FROM:<%s> SMTPUTF8\r\n"
+             :
+#endif
+               "MAIL FROM:<%s>\r\n",
               from_address) >= 0 &&
             smtp_read_response(&inblock, responsebuffer, sizeof(responsebuffer),
               '2', callout);
+
+         if (!done)
+           {
+           HDEBUG(D_acl|D_v)
+             debug_printf("problem after random/rset/mfrom; reopen conn\n");
+           random_local_part = NULL;
+#ifdef SUPPORT_TLS
+           tls_close(FALSE, TRUE);
+#endif
+           (void)close(inblock.sock);
+#ifdef EXPERIMENTAL_EVENT
+           (void) event_raise(addr->transport->event_action,
+                             US"tcp:close", NULL);
+#endif
+           goto tls_retry_connection;
+           }
           }
         else done = FALSE;    /* Some timeout/connection problem */
         }                     /* Random check */
@@ -1020,11 +1120,27 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
         /* Get the rcpt_include_affixes flag from the transport if there is one,
         but assume FALSE if there is not. */
 
+       uschar * rcpt = transport_rcpt_address(addr,
+              addr->transport ? addr->transport->rcpt_include_affixes : FALSE);
+
+#ifdef EXPERIMENTAL_INTERNATIONAL
+       /*XXX should the conversion be moved into transport_rcpt_address() ? */
+       uschar * dummy_errstr = NULL;
+       if (  testflag(addr, af_utf8_downcvt)
+          && (rcpt = string_address_utf8_to_alabel(rcpt, &dummy_errstr),
+              dummy_errstr
+          )  )
+       {
+       errno = ERRNO_EXPANDFAIL;
+       *failure_ptr = US"recipient";
+       done = FALSE;
+       }
+       else
+#endif
+
         done =
           smtp_write_command(&outblock, FALSE, "RCPT TO:<%.1000s>\r\n",
-            transport_rcpt_address(addr,
-              (addr->transport == NULL)? FALSE :
-               addr->transport->rcpt_include_affixes)) >= 0 &&
+            rcpt) >= 0 &&
           smtp_read_response(&inblock, responsebuffer, sizeof(responsebuffer),
             '2', callout);
 
@@ -1041,8 +1157,9 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 
         if (done && pm_mailfrom != NULL)
           {
-          /*XXX not suitable for cutthrough - we cannot afford to do an RSET
-         and lose the original mail-from */
+          /* Could possibly shift before main verify, just above, and be ok
+         for cutthrough.  But no way to handle a subsequent rcpt, so just
+         refuse any */
        cancel_cutthrough_connection("postmaster verify");
        HDEBUG(D_acl|D_v) debug_printf("Cutthrough cancelled by presence of postmaster verify\n");
 
@@ -1060,7 +1177,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 
             ((
             smtp_write_command(&outblock, FALSE,
-              "RCPT TO:<postmaster@%.1000s>\r\n", addr->domain) >= 0 &&
+              "RCPT TO:<postmaster@%.1000s>\r\n", rcpt_domain) >= 0 &&
             smtp_read_response(&inblock, responsebuffer,
               sizeof(responsebuffer), '2', callout)
             )
@@ -1111,6 +1228,21 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
         HDEBUG(D_verify) debug_printf("SMTP timeout\n");
         send_quit = FALSE;
         }
+#ifdef EXPERIMENTAL_INTERNATIONAL
+      else if (errno == ERRNO_UTF8_FWD)
+       {
+       extern int acl_where;   /* src/acl.c */
+       errno = 0;
+       addr->message = string_sprintf(
+           "response to \"%s\" from %s [%s] did not include SMTPUTF8",
+            big_buffer, host->name, host->address);
+        addr->user_message = acl_where == ACL_WHERE_RCPT
+         ? US"533 mailbox name not allowed"
+         : US"550 mailbox unavailable";
+       yield = FAIL;
+       done = TRUE;
+       }
+#endif
       else if (errno == 0)
         {
         if (*responsebuffer == 0) Ustrcpy(responsebuffer, US"connection dropped");
@@ -1149,6 +1281,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
        && !random_local_part
        && !pm_mailfrom
        && cutthrough.fd < 0
+       && !lmtp
        )
       {
       cutthrough.fd = outblock.sock;   /* We assume no buffer in use in the outblock */
@@ -1580,7 +1713,7 @@ if (addr != vaddr)
   vaddr->user_message = addr->user_message;
   vaddr->basic_errno = addr->basic_errno;
   vaddr->more_errno = addr->more_errno;
-  vaddr->p.address_data = addr->p.address_data;
+  vaddr->prop.address_data = addr->prop.address_data;
   copyflag(vaddr, addr, af_pass_message);
   }
 return yield;
@@ -1841,8 +1974,8 @@ while (addr_new != NULL)
 
   /* Just in case some router parameter refers to it. */
 
-  return_path = (addr->p.errors_address != NULL)?
-    addr->p.errors_address : sender_address;
+  return_path = (addr->prop.errors_address != NULL)?
+    addr->prop.errors_address : sender_address;
 
   /* Split the address into domain and local part, handling the %-hack if
   necessary, and then route it. While routing a sender address, set
@@ -1902,7 +2035,7 @@ while (addr_new != NULL)
         if (tf.hosts != NULL && (host_list == NULL || tf.hosts_override))
           {
           uschar *s;
-          uschar *save_deliver_domain = deliver_domain;
+          const uschar *save_deliver_domain = deliver_domain;
           uschar *save_deliver_localpart = deliver_localpart;
 
           host_list = NULL;    /* Ignore the router's hosts */
@@ -1922,7 +2055,6 @@ while (addr_new != NULL)
           else
             {
             int flags;
-            uschar *canonical_name;
             host_item *host, *nexthost;
             host_build_hostlist(&host_list, s, tf.hosts_randomize);
 
@@ -1941,21 +2073,20 @@ while (addr_new != NULL)
               nexthost = host->next;
               if (tf.gethostbyname ||
                   string_is_ip_address(host->name, NULL) != 0)
-                (void)host_find_byname(host, NULL, flags, &canonical_name, TRUE);
+                (void)host_find_byname(host, NULL, flags, NULL, TRUE);
               else
                {
-               uschar * d_request = NULL, * d_require = NULL;
+               dnssec_domains * dnssec_domains = NULL;
                if (Ustrcmp(addr->transport->driver_name, "smtp") == 0)
                  {
                  smtp_transport_options_block * ob =
                      (smtp_transport_options_block *)
                        addr->transport->options_block;
-                 d_request = ob->dnssec_request_domains;
-                 d_require = ob->dnssec_require_domains;
+                 dnssec_domains = &ob->dnssec;
                  }
 
                 (void)host_find_bydns(host, NULL, flags, NULL, NULL, NULL,
-                 d_request, d_require, &canonical_name, NULL);
+                 dnssec_domains, NULL, NULL);
                }
               }
             }
@@ -2136,7 +2267,7 @@ while (addr_new != NULL)
       /* If we have carried on to verify a child address, we want the value
       of $address_data to be that of the child */
 
-      vaddr->p.address_data = addr->p.address_data;
+      vaddr->prop.address_data = addr->prop.address_data;
       yield = OK;
       goto out;
       }
@@ -2168,8 +2299,8 @@ for (addr_list = addr_local, i = 0; i < 2; addr_list = addr_remote, i++)
 
     fprintf(f, "%s", CS addr->address);
 #ifdef EXPERIMENTAL_SRS
-    if(addr->p.srs_sender)
-      fprintf(f, "    [srs = %s]", addr->p.srs_sender);
+    if(addr->prop.srs_sender)
+      fprintf(f, "    [srs = %s]", addr->prop.srs_sender);
 #endif
 
     /* If the address is a duplicate, show something about it. */
@@ -2232,6 +2363,12 @@ for (addr_list = addr_local, i = 0; i < 2; addr_list = addr_remote, i++)
         while (len++ < maxaddlen) fprintf(f," ");
         if (h->mx >= 0) fprintf(f, "MX=%d", h->mx);
         if (h->port != PORT_NONE) fprintf(f, " port=%d", h->port);
+        if (running_in_test_harness)
+#ifndef DISABLE_DNSSEC
+          fprintf(f, " ad=%s", h->dnssec==DS_YES ? "yes" : "no");
+#else
+          fprintf(f, " ad=no");
+#endif
         if (h->status == hstatus_unusable) fprintf(f, " ** unusable **");
         fprintf(f, "\n");
         }
@@ -2351,7 +2488,8 @@ for (h = header_list; h != NULL && yield == OK; h = h->next)
         verb = US"begins";
         }
 
-      *msgptr = string_printing(
+      /* deconst cast ok as we're passing a non-const to string_printing() */
+      *msgptr = US string_printing(
         string_sprintf("%s: failing address in \"%.*s:\" header %s: %.*s",
           errmess, tt - h->text, h->text, verb, len, s));
 
@@ -2872,9 +3010,9 @@ if (*p == 0) goto END_OFF;
 /* The rest of the line is the data we want. We turn it into printing
 characters when we save it, so that it cannot mess up the format of any logging
 or Received: lines into which it gets inserted. We keep a maximum of 127
-characters. */
+characters. The deconst cast is ok as we fed a nonconst to string_printing() */
 
-sender_ident = string_printing(string_copyn(p, 127));
+sender_ident = US string_printing(string_copyn(p, 127));
 DEBUG(D_ident) debug_printf("sender_ident = %s\n", sender_ident);
 
 END_OFF:
@@ -2919,7 +3057,7 @@ Returns:         OK      matched
 */
 
 int
-check_host(void *arg, uschar *ss, uschar **valueptr, uschar **error)
+check_host(void *arg, const uschar *ss, const uschar **valueptr, uschar **error)
 {
 check_host_block *cb = (check_host_block *)arg;
 int mlen = -1;
@@ -2927,7 +3065,7 @@ int maskoffset;
 BOOL iplookup = FALSE;
 BOOL isquery = FALSE;
 BOOL isiponly = cb->host_name != NULL && cb->host_name[0] == 0;
-uschar *t;
+const uschar *t;
 uschar *semicolon;
 uschar **aliases;
 
@@ -3108,6 +3246,10 @@ if (*t == 0)
   h.address = NULL;
   h.mx = MX_NONE;
 
+  /* Using byname rather than bydns here means we cannot determine dnssec
+  status.  On the other hand it is unclear how that could be either
+  propagated up or enforced. */
+
   rc = host_find_byname(&h, NULL, HOST_FIND_QUALIFY_SINGLE, NULL, FALSE);
   if (rc == HOST_FOUND || rc == HOST_FOUND_LOCAL)
     {
@@ -3140,7 +3282,7 @@ on spec. */
 
 if ((semicolon = Ustrchr(ss, ';')) != NULL)
   {
-  uschar *affix;
+  const uschar *affix;
   int partial, affixlen, starflags, id;
 
   *semicolon = 0;
@@ -3241,12 +3383,12 @@ determined from the IP address, the result is FAIL unless the item
 "+allow_unknown" was met earlier in the list, in which case OK is returned. */
 
 int
-verify_check_this_host(uschar **listptr, unsigned int *cache_bits,
-  uschar *host_name, uschar *host_address, uschar **valueptr)
+verify_check_this_host(const uschar **listptr, unsigned int *cache_bits,
+  const uschar *host_name, const uschar *host_address, const uschar **valueptr)
 {
 int rc;
 unsigned int *local_cache_bits = cache_bits;
-uschar *save_host_address = deliver_host_address;
+const uschar *save_host_address = deliver_host_address;
 check_host_block cb;
 cb.host_name = host_name;
 cb.host_address = host_address;
@@ -3291,7 +3433,7 @@ return rc;
 int
 verify_check_given_host(uschar **listptr, host_item *host)
 {
-return verify_check_this_host(listptr, NULL, host->name, host->address, NULL);
+return verify_check_this_host(CUSS listptr, NULL, host->name, host->address, NULL);
 }
 
 /*************************************************
@@ -3313,7 +3455,7 @@ Returns:               the yield of verify_check_this_host(),
 int
 verify_check_host(uschar **listptr)
 {
-return verify_check_this_host(listptr, sender_host_cache, NULL,
+return verify_check_this_host(CUSS listptr, sender_host_cache, NULL,
   (sender_host_address == NULL)? US"" : sender_host_address, NULL);
 }
 
@@ -3481,13 +3623,13 @@ if (t == NULL)
     dns_record *rr;
     dns_address **addrp = &(cb->rhs);
     for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
-         rr != NULL;
+         rr;
          rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
       {
       if (rr->type == T_A)
         {
         dns_address *da = dns_address_from_rr(&dnsa, rr);
-        if (da != NULL)
+        if (da)
           {
           *addrp = da;
           while (da->next != NULL) da = da->next;
@@ -3544,7 +3686,7 @@ if (cb->rc == DNS_SUCCEED)
       {
       int ipsep = ',';
       uschar ip[46];
-      uschar *ptr = iplist;
+      const uschar *ptr = iplist;
       uschar *res;
 
       /* Handle exact matching */
@@ -3747,11 +3889,11 @@ Returns:    OK      successful lookup (i.e. the address is on the list), or
 */
 
 int
-verify_check_dnsbl(uschar **listptr)
+verify_check_dnsbl(const uschar **listptr)
 {
 int sep = 0;
 int defer_return = FAIL;
-uschar *list = *listptr;
+const uschar *list = *listptr;
 uschar *domain;
 uschar *s;
 uschar buffer[1024];
@@ -3897,7 +4039,7 @@ while ((domain = string_nextinlist(&list, &sep, buffer, sizeof(buffer))) != NULL
     uschar keybuffer[256];
     uschar keyrevadd[128];
 
-    while ((keydomain = string_nextinlist(&key, &keysep, keybuffer,
+    while ((keydomain = string_nextinlist(CUSS &key, &keysep, keybuffer,
             sizeof(keybuffer))) != NULL)
       {
       uschar *prepend = keydomain;