Merge branch 'hs/taintwarn'

This is a "forward" port of the taintwarn patches that are applied to
4.94.2+fixes.

23 files changed, 276 insertions, 199 deletions

diff --git a/src/src/EDITME b/src/src/EDITME
index 8cd34e8be..f4329fabf 100644
--- a/src/src/EDITME
+++ b/src/src/EDITME
@@ -748,6 +748,13 @@ FIXED_NEVER_USERS=root
 
 # WHITELIST_D_MACROS=TLS:SPOOL
 
+# The next setting enables a main config option
+# "allow_insecure_tainted_data" to turn taint failures into warnings.
+# Though this option is new, it is deprecated already now, and will be
+# ignored in future releases of Exim. It is meant as mitigation for
+# upgrading old (possibly insecure) configurations to more secure ones.
+ALLOW_INSECURE_TAINTED_DATA=yes
+
 #------------------------------------------------------------------------------
 # Exim has support for the AUTH (authentication) extension of the SMTP
 # protocol, as defined by RFC 2554. If you don't know what SMTP authentication
diff --git a/src/src/acl.c b/src/src/acl.c
index f358516a1..1bf118764 100644
--- a/src/src/acl.c
+++ b/src/src/acl.c
@@ -3702,20 +3702,22 @@ for (; cb; cb = cb->next)
     #endif
 
     case ACLC_QUEUE:
-    if (is_tainted(arg))
       {
-      *log_msgptr = string_sprintf("Tainted name '%s' for queue not permitted",
-				    arg);
-      return ERROR;
-      }
-    if (Ustrchr(arg, '/'))
-      {
-      *log_msgptr = string_sprintf(
-	      "Directory separator not permitted in queue name: '%s'", arg);
-      return ERROR;
+      uschar *m;
+      if ((m = is_tainted2(arg, 0, "Tainted name '%s' for queue not permitted", arg)))
+        {
+        *log_msgptr = m;
+        return ERROR;
+        }
+      if (Ustrchr(arg, '/'))
+        {
+        *log_msgptr = string_sprintf(
+                "Directory separator not permitted in queue name: '%s'", arg);
+        return ERROR;
+        }
+      queue_name = string_copy_perm(arg, FALSE);
+      break;
       }
-    queue_name = string_copy_perm(arg, FALSE);
-    break;
 
     case ACLC_RATELIMIT:
     rc = acl_ratelimit(arg, where, log_msgptr);
@@ -4088,25 +4090,14 @@ while (isspace(*ss)) ss++;
 
 acl_text = ss;
 
-#ifdef notyet_taintwarn
 if (  !f.running_in_test_harness
    &&  is_tainted2(acl_text, LOG_MAIN|LOG_PANIC,
-			  "attempt to use tainted ACL text \"%s\"", acl_text))
+			  "Tainted ACL text \"%s\"", acl_text))
   {
   /* Avoid leaking info to an attacker */
   *log_msgptr = US"internal configuration error";
   return ERROR;
   }
-#else
-if (is_tainted(acl_text) && !f.running_in_test_harness)
-  {
-  log_write(0, LOG_MAIN|LOG_PANIC,
-    "attempt to use tainted ACL text \"%s\"", acl_text);
-  /* Avoid leaking info to an attacker */
-  *log_msgptr = US"internal configuration error";
-  return ERROR;
-  }
-#endif
 
 /* Handle the case of a string that does not contain any spaces. Look for a
 named ACL among those read from the configuration, or a previously read file.
@@ -4131,6 +4122,12 @@ if (Ustrchr(ss, ' ') == NULL)
   else if (*ss == '/')
     {
     struct stat statbuf;
+    if (is_tainted2(ss, LOG_MAIN|LOG_PANIC, "Tainted ACL file name '%s'", ss))
+      {
+      /* Avoid leaking info to an attacker */
+      *log_msgptr = US"internal configuration error";
+      return ERROR;
+      }
     if ((fd = Uopen(ss, O_RDONLY, 0)) < 0)
       {
       *log_msgptr = string_sprintf("failed to open ACL file \"%s\": %s", ss,
diff --git a/src/src/config.h.defaults b/src/src/config.h.defaults
index e233fb3e5..877cc7bc4 100644
--- a/src/src/config.h.defaults
+++ b/src/src/config.h.defaults
@@ -17,6 +17,8 @@ Do not put spaces between # and the 'define'.
 #define ALT_CONFIG_PREFIX
 #define TRUSTED_CONFIG_LIST
 
+#define ALLOW_INSECURE_TAINTED_DATA
+
 #define APPENDFILE_MODE            0600
 #define APPENDFILE_DIRECTORY_MODE  0700
 #define APPENDFILE_LOCKFILE_MODE   0600
diff --git a/src/src/dbstuff.h b/src/src/dbstuff.h
index 8a8a5fb67..2f00dffb4 100644
--- a/src/src/dbstuff.h
+++ b/src/src/dbstuff.h
@@ -640,11 +640,9 @@ after reading data. */
       : (flags) == O_RDWR ? "O_RDWR"	\
       : (flags) == (O_RDWR|O_CREAT) ? "O_RDWR|O_CREAT"	\
       : "??");	\
-  if (is_tainted(name) || is_tainted(dirname)) \
-    { \
-    log_write(0, LOG_MAIN|LOG_PANIC, "Tainted name for DB file not permitted"); \
+  if (is_tainted2(name, LOG_MAIN|LOG_PANIC, "Tainted name '%s' for DB file not permitted", name) \
+      || is_tainted2(dirname, LOG_MAIN|LOG_PANIC, "Tainted name '%s' for DB directory not permitted", dirname)) \
     *dbpp = NULL; \
-    } \
   else \
     { EXIM_DBOPEN__(name, dirname, flags, mode, dbpp); } \
   DEBUG(D_hints_lookup) debug_printf_indent("returned from EXIM_DBOPEN: %p\n", *dbpp); \
diff --git a/src/src/deliver.c b/src/src/deliver.c
index 4e472ebe6..f9f674643 100644
--- a/src/src/deliver.c
+++ b/src/src/deliver.c
@@ -5550,10 +5550,11 @@ FILE * fp = NULL;
 if (!s || !*s)
   log_write(0, LOG_MAIN|LOG_PANIC,
     "Failed to expand %s: '%s'\n", varname, filename);
-else if (*s != '/' || is_tainted(s))
-  log_write(0, LOG_MAIN|LOG_PANIC,
-    "%s is not %s after expansion: '%s'\n",
-    varname, *s == '/' ? "untainted" : "absolute", s);
+else if (*s != '/')
+  log_write(0, LOG_MAIN|LOG_PANIC, "%s is not absolute after expansion: '%s'\n",
+    varname, s);
+else if (is_tainted2(s, LOG_MAIN|LOG_PANIC, "Tainted %s after expansion: '%s'\n", varname, s))
+  ;
 else if (!(fp = Ufopen(s, "rb")))
   log_write(0, LOG_MAIN|LOG_PANIC, "Failed to open %s for %s "
     "message texts: %s", s, reason, strerror(errno));
@@ -6163,9 +6164,10 @@ else if (system_filter && process_recipients != RECIP_FAIL_TIMEOUT)
           if (!tmp)
             p->message = string_sprintf("failed to expand \"%s\" as a "
               "system filter transport name", tpname);
-	  if (is_tainted(tmp))
-            p->message = string_sprintf("attempt to used tainted value '%s' for"
-	      "transport '%s' as a system filter", tmp, tpname);
+          { uschar *m;
+	  if ((m = is_tainted2(tmp, 0, "Tainted values '%s' " "for transport '%s' as a system filter", tmp, tpname)))
+            p->message = m;
+          }
           tpname = tmp;
           }
         else
diff --git a/src/src/directory.c b/src/src/directory.c
index f54a781b7..3273eb89b 100644
--- a/src/src/directory.c
+++ b/src/src/directory.c
@@ -44,8 +44,8 @@ uschar c = 1;
 struct stat statbuf;
 uschar * path;
 
-if (is_tainted(name)) 
-  { p = US"create"; path = US name; errno = ERRNO_TAINT; goto bad; }
+if (is_tainted2(name, LOG_MAIN|LOG_PANIC, "Tainted path '%s' for new directory", name))
+  { p = US"create"; path = US name; errno = EACCES; goto bad; }
 
 if (parent)
   {
diff --git a/src/src/expand.c b/src/src/expand.c
index 989e97b84..4fb935528 100644
--- a/src/src/expand.c
+++ b/src/src/expand.c
@@ -4483,13 +4483,13 @@ DEBUG(D_expand)
 f.expand_string_forcedfail = FALSE;
 expand_string_message = US"";
 
-if (is_tainted(string))
+{ uschar *m;
+if ((m = is_tainted2(string, LOG_MAIN|LOG_PANIC, "Tainted string '%s' in expansion", s)))
   {
-  expand_string_message =
-    string_sprintf("attempt to expand tainted string '%s'", s);
-  log_write(0, LOG_MAIN|LOG_PANIC, "%s", expand_string_message);
+  expand_string_message = m;
   goto EXPAND_FAILED;
   }
+}
 
 while (*s)
   {
@@ -7645,10 +7645,12 @@ while (*s)
 	/* Manually track tainting, as we deal in individual chars below */
 
 	if (is_tainted(sub))
+          {
 	  if (yield->s && yield->ptr)
 	    gstring_rebuffer(yield);
 	  else
 	    yield->s = store_get(yield->size = Ustrlen(sub), TRUE);
+          }
 
 	/* Check the UTF-8, byte-by-byte */
 
@@ -8209,6 +8211,7 @@ that is a bad idea, because expand_string_message is in dynamic store. */
 EXPAND_FAILED:
 if (left) *left = s;
 DEBUG(D_expand)
+  {
   DEBUG(D_noutf8)
     {
     debug_printf_indent("|failed to expand: %s\n", string);
@@ -8228,6 +8231,7 @@ DEBUG(D_expand)
     if (f.expand_string_forcedfail)
       debug_printf_indent(UTF8_UP_RIGHT "failure was forced\n");
     }
+  }
 if (resetok_p && !resetok) *resetok_p = FALSE;
 expand_level--;
 return NULL;
diff --git a/src/src/functions.h b/src/src/functions.h
index 4212c3328..6029ab4b1 100644
--- a/src/src/functions.h
+++ b/src/src/functions.h
@@ -1125,20 +1125,50 @@ if (f.running_in_test_harness && f.testsuite_delays) millisleep(millisec);
 
 /******************************************************************************/
 /* Taint-checked file opens */
+static inline uschar *
+is_tainted2(const void *p, int lflags, const char* fmt, ...)
+{
+va_list ap;
+uschar *msg;
+rmark mark;
+
+if (!is_tainted(p))
+  return NULL;
+
+mark = store_mark();
+va_start(ap, fmt);
+msg = string_from_gstring(string_vformat(NULL, SVFMT_TAINT_NOCHK|SVFMT_EXTEND, fmt, ap));
+va_end(ap);
+
+#ifdef ALLOW_INSECURE_TAINTED_DATA
+if (allow_insecure_tainted_data)
+  {
+  if LOGGING(tainted) log_write(0, LOG_MAIN, "Warning: %s", msg);
+  store_reset(mark);
+  return NULL;
+  }
+#endif
+
+if (lflags) log_write(0, lflags, "%s", msg);
+return msg; /* no store_reset(), as the message might be used afterwards and Exim
+            is expected to exit anyway, so we do not care about the leaked
+            storage */
+}
 
 static inline int
 exim_open2(const char *pathname, int flags)
 {
-if (!is_tainted(pathname)) return open(pathname, flags);
-log_write(0, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname);
+if (!is_tainted2(pathname, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname))
+  return open(pathname, flags);
 errno = EACCES;
 return -1;
 }
+
 static inline int
 exim_open(const char *pathname, int flags, mode_t mode)
 {
-if (!is_tainted(pathname)) return open(pathname, flags, mode);
-log_write(0, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname);
+if (!is_tainted2(pathname, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname))
+  return open(pathname, flags, mode);
 errno = EACCES;
 return -1;
 }
@@ -1146,16 +1176,16 @@ return -1;
 static inline int
 exim_openat(int dirfd, const char *pathname, int flags)
 {
-if (!is_tainted(pathname)) return openat(dirfd, pathname, flags);
-log_write(0, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname);
+if (!is_tainted2(pathname, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname))
+  return openat(dirfd, pathname, flags);
 errno = EACCES;
 return -1;
 }
 static inline int
 exim_openat4(int dirfd, const char *pathname, int flags, mode_t mode)
 {
-if (!is_tainted(pathname)) return openat(dirfd, pathname, flags, mode);
-log_write(0, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname);
+if (!is_tainted2(pathname, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname))
+  return openat(dirfd, pathname, flags, mode);
 errno = EACCES;
 return -1;
 }
@@ -1164,8 +1194,8 @@ return -1;
 static inline FILE *
 exim_fopen(const char *pathname, const char *mode)
 {
-if (!is_tainted(pathname)) return fopen(pathname, mode);
-log_write(0, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname);
+if (!is_tainted2(pathname, LOG_MAIN|LOG_PANIC, "Tainted filename '%s'", pathname))
+  return fopen(pathname, mode);
 errno = EACCES;
 return NULL;
 }
@@ -1173,8 +1203,8 @@ return NULL;
 static inline DIR *
 exim_opendir(const uschar * name)
 {
-if (!is_tainted(name)) return opendir(CCS name);
-log_write(0, LOG_MAIN|LOG_PANIC, "Tainted dirname '%s'", name);
+if (!is_tainted2(name, LOG_MAIN|LOG_PANIC, "Tainted dirname '%s'", name))
+  return opendir(CCS name);
 errno = EACCES;
 return NULL;
 }
diff --git a/src/src/globals.c b/src/src/globals.c
index e96586048..9e68aaca8 100644
--- a/src/src/globals.c
+++ b/src/src/globals.c
@@ -98,6 +98,10 @@ int     sqlite_lock_timeout    = 5;
 BOOL    move_frozen_messages   = FALSE;
 #endif
 
+#ifdef ALLOW_INSECURE_TAINTED_DATA
+BOOL    allow_insecure_tainted_data = FALSE;
+#endif
+
 /* These variables are outside the #ifdef because it keeps the code less
 cluttered in several places (e.g. during logging) if we can always refer to
 them. Also, the tls_ variables are now always visible.  Note that these are
@@ -1055,6 +1059,9 @@ int     log_default[]          = { /* for initializing log_selector */
   Li_size_reject,
   Li_skip_delivery,
   Li_smtp_confirmation,
+#ifdef ALLOW_INSECURE_TAINTED_DATA
+  Li_tainted,
+#endif
   Li_tls_certificate_verified,
   Li_tls_cipher,
   -1
@@ -1124,6 +1131,9 @@ bit_table log_options[]        = { /* must be in alphabetical order,
   BIT_TABLE(L, smtp_protocol_error),
   BIT_TABLE(L, smtp_syntax_error),
   BIT_TABLE(L, subject),
+#ifdef ALLOW_INSECURE_TAINTED_DATA
+  BIT_TABLE(L, tainted),
+#endif
   BIT_TABLE(L, tls_certificate_verified),
   BIT_TABLE(L, tls_cipher),
   BIT_TABLE(L, tls_peerdn),
diff --git a/src/src/globals.h b/src/src/globals.h
index 937cce776..657e6c706 100644
--- a/src/src/globals.h
+++ b/src/src/globals.h
@@ -77,6 +77,10 @@ extern int     sqlite_lock_timeout;    /* Internal lock waiting timeout */
 extern BOOL    move_frozen_messages;   /* Get them out of the normal directory */
 #endif
 
+#ifdef ALLOW_INSECURE_TAINTED_DATA
+extern BOOL    allow_insecure_tainted_data;
+#endif
+
 /* These variables are outside the #ifdef because it keeps the code less
 cluttered in several places (e.g. during logging) if we can always refer to
 them. Also, the tls_ variables are now always visible. */
diff --git a/src/src/log.c b/src/src/log.c
index e22fc4fdf..1b77f98fa 100644
--- a/src/src/log.c
+++ b/src/src/log.c
@@ -288,8 +288,11 @@ if (fd < 0 && errno == ENOENT)
   uschar *lastslash = Ustrrchr(name, '/');
   *lastslash = 0;
   created = directory_make(NULL, name, LOG_DIRECTORY_MODE, FALSE);
-  DEBUG(D_any) debug_printf("%s log directory %s\n",
-    created ? "created" : "failed to create", name);
+  DEBUG(D_any)
+    if (created)
+      debug_printf("created log directory %s\n", name);
+    else
+      debug_printf("failed to create log directory %s: %s\n", name, strerror(errno));
   *lastslash = '/';
   if (created) fd = Uopen(name, flags, LOG_MODE);
   }
@@ -452,7 +455,7 @@ return fd;
 it does not exist. This may be called recursively on failure, in order to open
 the panic log.
 
-The directory is in the static variable file_path. This is static so that it
+The directory is in the static variable file_path. This is static so that
 the work of sorting out the path is done just once per Exim process.
 
 Exim is normally configured to avoid running as root wherever possible, the log
@@ -487,62 +490,64 @@ people want, I hope. */
 
 ok = string_format(buffer, sizeof(buffer), CS file_path, log_names[type]);
 
-/* Save the name of the mainlog for rollover processing. Without a datestamp,
-it gets statted to see if it has been cycled. With a datestamp, the datestamp
-will be compared. The static slot for saving it is the same size as buffer,
-and the text has been checked above to fit, so this use of strcpy() is OK. */
-
-if (type == lt_main)
+switch (type)
   {
-  Ustrcpy(mainlog_name, buffer);
-  if (string_datestamp_offset > 0)
-    mainlog_datestamp = mainlog_name + string_datestamp_offset;
-  }
+  case lt_main:
+    /* Save the name of the mainlog for rollover processing. Without a datestamp,
+    it gets statted to see if it has been cycled. With a datestamp, the datestamp
+    will be compared. The static slot for saving it is the same size as buffer,
+    and the text has been checked above to fit, so this use of strcpy() is OK. */
+
+    Ustrcpy(mainlog_name, buffer);
+    if (string_datestamp_offset > 0)
+      mainlog_datestamp = mainlog_name + string_datestamp_offset;
+    break;
 
-/* Ditto for the reject log */
+  case lt_reject:
+    /* Ditto for the reject log */
 
-else if (type == lt_reject)
-  {
-  Ustrcpy(rejectlog_name, buffer);
-  if (string_datestamp_offset > 0)
-    rejectlog_datestamp = rejectlog_name + string_datestamp_offset;
-  }
+    Ustrcpy(rejectlog_name, buffer);
+    if (string_datestamp_offset > 0)
+      rejectlog_datestamp = rejectlog_name + string_datestamp_offset;
+    break;
 
-/* and deal with the debug log (which keeps the datestamp, but does not
-update it) */
+  case lt_debug:
+    /* and deal with the debug log (which keeps the datestamp, but does not
+    update it) */
 
-else if (type == lt_debug)
-  {
-  Ustrcpy(debuglog_name, buffer);
-  if (tag)
-    {
-    /* this won't change the offset of the datestamp */
-    ok2 = string_format(buffer, sizeof(buffer), "%s%s",
-      debuglog_name, tag);
-    if (ok2)
-      Ustrcpy(debuglog_name, buffer);
-    }
-  }
+    Ustrcpy(debuglog_name, buffer);
+    if (tag)
+      {
+      /* this won't change the offset of the datestamp */
+      ok2 = string_format(buffer, sizeof(buffer), "%s%s",
+        debuglog_name, tag);
+      if (ok2)
+        Ustrcpy(debuglog_name, buffer);
+      }
+    break;
 
-/* Remove any datestamp if this is the panic log. This is rare, so there's no
-need to optimize getting the datestamp length. We remove one non-alphanumeric
-char afterwards if at the start, otherwise one before. */
+  default:
+    /* Remove any datestamp if this is the panic log. This is rare, so there's no
+  need to optimize getting the datestamp length. We remove one non-alphanumeric
+  char afterwards if at the start, otherwise one before. */
 
-else if (string_datestamp_offset >= 0)
-  {
-  uschar * from = buffer + string_datestamp_offset;
-  uschar * to = from + string_datestamp_length;
+    if (string_datestamp_offset >= 0)
+      {
+      uschar * from = buffer + string_datestamp_offset;
+      uschar * to = from + string_datestamp_length;
 
-  if (from == buffer || from[-1] == '/')
-    {
-    if (!isalnum(*to)) to++;
-    }
-  else
-    if (!isalnum(from[-1])) from--;
+      if (from == buffer || from[-1] == '/')
+        {
+        if (!isalnum(*to)) to++;
+        }
+      else
+        if (!isalnum(from[-1])) from--;
 
-  /* This copy is ok, because we know that to is a substring of from. But
-  due to overlap we must use memmove() not Ustrcpy(). */
-  memmove(from, to, Ustrlen(to)+1);
+      /* This copy is ok, because we know that to is a substring of from. But
+      due to overlap we must use memmove() not Ustrcpy(). */
+      memmove(from, to, Ustrlen(to)+1);
+      }
+    break;
   }
 
 /* If the file name is too long, it is an unrecoverable disaster */
@@ -556,9 +561,7 @@ if (!ok)
 *fd = log_open_as_exim(buffer);
 
 if (*fd >= 0)
-  {
   return;
-  }
 
 euid = geteuid();
 
@@ -710,26 +713,62 @@ return total_written;
 }
 
 
+/* Pull the file out of the configured or the compiled-in list.
+Called for an empty log_file_path element, for debug logging activation
+when file_path has not previously been set, and from the appenfile transport setup. */
 
-static void
-set_file_path(void)
+void
+set_file_path(BOOL *multiple)
 {
+uschar *s;
 int sep = ':';              /* Fixed separator - outside use */
-uschar *t;
-const uschar *tt = US LOG_FILE_PATH;
-while ((t = string_nextinlist(&tt, &sep, log_buffer, LOG_BUFFER_SIZE)))
-  {
-  if (Ustrcmp(t, "syslog") == 0 || t[0] == 0) continue;
-  file_path = string_copy(t);
-  break;
-  }
+const uschar *ss = *log_file_path ? log_file_path : US LOG_FILE_PATH;
+
+if (*ss)
+  for (logging_mode = 0;
+       s = string_nextinlist(&ss, &sep, log_buffer, LOG_BUFFER_SIZE); )
+    {
+    if (Ustrcmp(s, "syslog") == 0)
+      logging_mode |= LOG_MODE_SYSLOG;
+    else if (!(logging_mode & LOG_MODE_FILE))  /* no file yet */
+      {
+      logging_mode |= LOG_MODE_FILE;
+      if (*s) file_path = string_copy(s);     /* If a non-empty path is given, use it */
+      }
+    else if (multiple) *multiple = TRUE;
+    }
+else
+  logging_mode = LOG_MODE_FILE;
+
+/* Set up the ultimate default if necessary. */
+
+if (logging_mode & LOG_MODE_FILE  &&  !*file_path)
+  if (LOG_FILE_PATH[0])
+    {
+      /* If we still do not have a file_path, we take
+      the first non-empty, non-syslog item in LOG_FILE_PATH, if there is
+      one.  If there is no such item, use the ultimate default in the
+      spool directory. */
+
+       for (ss = US LOG_FILE_PATH;
+            s = string_nextinlist(&ss, &sep, log_buffer, LOG_BUFFER_SIZE);)
+          {
+            if (*s != '/') continue;
+            file_path = string_copy(s);
+          }
+    }
+  else file_path = string_sprintf("%s/log/%%slog", spool_directory);
 }
 
 
 void
 mainlog_close(void)
 {
-if (mainlogfd < 0) return;
+/* avoid closing it if it is closed already or if we do not see a chance
+to open the file mainlog later again */
+if (mainlogfd < 0 /* already closed */
+   || !(geteuid() == 0 || geteuid() == exim_uid))
+  return;
 (void)close(mainlogfd);
 mainlogfd = -1;
 mainlog_inode = 0;
@@ -841,41 +880,9 @@ if (!path_inspected)
 
   store_pool = POOL_PERM;
 
-  /* If nothing has been set, don't waste effort... the default values for the
-  statics are file_path="" and logging_mode = LOG_MODE_FILE. */
-
-  if (*log_file_path)
-    {
-    int sep = ':';              /* Fixed separator - outside use */
-    uschar *s;
-    const uschar *ss = log_file_path;
-
-    logging_mode = 0;
-    while ((s = string_nextinlist(&ss, &sep, log_buffer, LOG_BUFFER_SIZE)))
-      {
-      if (Ustrcmp(s, "syslog") == 0)
-        logging_mode |= LOG_MODE_SYSLOG;
-      else if (logging_mode & LOG_MODE_FILE)
-	multiple = TRUE;
-      else
-        {
-        logging_mode |= LOG_MODE_FILE;
-
-        /* If a non-empty path is given, use it */
-
-        if (*s)
-          file_path = string_copy(s);
-
-        /* If the path is empty, we want to use the first non-empty, non-
-        syslog item in LOG_FILE_PATH, if there is one, since the value of
-        log_file_path may have been set at runtime. If there is no such item,
-        use the ultimate default in the spool directory. */
-
-        else
-	  set_file_path();  /* Empty item in log_file_path */
-        }    /* First non-syslog item in log_file_path */
-      }      /* Scan of log_file_path */
-    }
+  /* make sure that we have a valid log file path in "file_path",
+  the open_log() later relies on it */
+  set_file_path(&multiple);
 
   /* If no modes have been selected, it is a major disaster */
 
@@ -883,11 +890,8 @@ if (!path_inspected)
     die(US"Neither syslog nor file logging set in log_file_path",
         US"Unexpected logging failure");
 
-  /* Set up the ultimate default if necessary. Then revert to the old store
-  pool, and record that we've sorted out the path. */
+  /* Revert to the old store pool, and record that we've sorted out the path. */
 
-  if (logging_mode & LOG_MODE_FILE  &&  !file_path[0])
-    file_path = string_sprintf("%s/log/%%slog", spool_directory);
   store_pool = old_pool;
   path_inspected = TRUE;
 
@@ -1241,6 +1245,7 @@ if (flags & LOG_PANIC)
 
   if (logging_mode & LOG_MODE_FILE)
     {
+    if (!*file_path) set_file_path(NULL);
     panic_recurseflag = TRUE;
     open_log(&paniclogfd, lt_panic, NULL);  /* Won't return on failure */
     panic_recurseflag = FALSE;
@@ -1493,7 +1498,7 @@ if (opts)
 resulting in certain setup not having been done.  Hack this for now so we
 do not segfault; note that nondefault log locations will not work */
 
-if (!*file_path) set_file_path();
+if (!*file_path) set_file_path(NULL);
 
 open_log(&fd, lt_debug, tag_name);
 
@@ -1515,5 +1520,14 @@ debug_file = NULL;
 unlink_log(lt_debug);
 }
 
+/* Called from the appendfile transport setup. */
+void
+open_logs(void)
+{
+set_file_path(NULL);
+if (!(logging_mode & LOG_MODE_FILE)) return;
+open_log(&mainlogfd, lt_main, 0);
+open_log(&rejectlogfd, lt_reject, 0);
+}
 
 /* End of log.c */
diff --git a/src/src/lookups/lf_sqlperform.c b/src/src/lookups/lf_sqlperform.c
index ad1df29d1..38b7c2ad3 100644
--- a/src/src/lookups/lf_sqlperform.c
+++ b/src/src/lookups/lf_sqlperform.c
@@ -102,11 +102,13 @@ if (Ustrncmp(query, "servers", 7) == 0)
         }
       }
 
-    if (is_tainted(server))
-      {
-      *errmsg = string_sprintf("%s server \"%s\" is tainted", name, server);
+    { uschar *m;
+    if ((m = is_tainted2(server, 0, "Tainted %s server '%s'", name, server)))
+     {
+      *errmsg = m;
       return DEFER;
       }
+    }
 
     rc = (*fn)(ss+1, server, result, errmsg, &defer_break, do_cache, opts);
     if (rc != DEFER || defer_break) return rc;
@@ -158,11 +160,13 @@ else
 	server = ele;
 	}
 
-      if (is_tainted(server))
+      { uschar *m;
+      if ((m = is_tainted2(server, 0, "Tainted %s server '%s'", name, server)))
         {
-        *errmsg = string_sprintf("%s server \"%s\" is tainted", name, server);
+        *errmsg = m;
         return DEFER;
         }
+      }
 
       rc = (*fn)(query, server, result, errmsg, &defer_break, do_cache, opts);
       if (rc != DEFER || defer_break) return rc;
diff --git a/src/src/macros.h b/src/src/macros.h
index f8987d604..ccdcc451f 100644
--- a/src/src/macros.h
+++ b/src/src/macros.h
@@ -491,6 +491,9 @@ enum logbit {
   Li_smtp_mailauth,
   Li_smtp_no_mail,
   Li_subject,
+#ifdef ALLOW_INSECURE_TAINTED_DATA
+  Li_tainted,
+#endif
   Li_tls_certificate_verified,
   Li_tls_cipher,
   Li_tls_peerdn,
diff --git a/src/src/parse.c b/src/src/parse.c
index fa3395206..896d00f30 100644
--- a/src/src/parse.c
+++ b/src/src/parse.c
@@ -1415,12 +1415,8 @@ for (;;)
       return FF_ERROR;
       }
 
-    if (is_tainted(filename))
-      {
-      *error = string_sprintf("Tainted name '%s' for included file  not permitted\n",
-       filename);
+    if ((*error = is_tainted2(filename, 0, "Tainted name '%s' for included file not permitted\n", filename)))
       return FF_ERROR;
-      }
 
     /* Check file name if required */
 
diff --git a/src/src/rda.c b/src/src/rda.c
index fb3714ea2..a12e5de29 100644
--- a/src/src/rda.c
+++ b/src/src/rda.c
@@ -179,10 +179,8 @@ struct stat statbuf;
 /* Reading a file is a form of expansion; we wish to deny attackers the
 capability to specify the file name. */
 
-if (is_tainted(filename))
+if ((*error = is_tainted2(filename, 0, "Tainted name '%s' for file read not permitted\n", filename)))
   {
-  *error = string_sprintf("Tainted name '%s' for file read not permitted\n",
-			filename);
   *yield = FF_ERROR;
   return NULL;
   }
diff --git a/src/src/readconf.c b/src/src/readconf.c
index ae36fa0c5..34ebf8769 100644
--- a/src/src/readconf.c
+++ b/src/src/readconf.c
@@ -68,6 +68,9 @@ static optionlist optionlist_config[] = {
   { "add_environment",          opt_stringptr,   {&add_environment} },
   { "admin_groups",             opt_gidlist,     {&admin_groups} },
   { "allow_domain_literals",    opt_bool,        {&allow_domain_literals} },
+#ifdef ALLOW_INSECURE_TAINTED_DATA
+  { "allow_insecure_tainted_data", opt_bool,     {&allow_insecure_tainted_data} },
+#endif
   { "allow_mx_to_ip",           opt_bool,        {&allow_mx_to_ip} },
   { "allow_utf8_domains",       opt_bool,        {&allow_utf8_domains} },
   { "auth_advertise_hosts",     opt_stringptr,   {&auth_advertise_hosts} },
diff --git a/src/src/routers/rf_get_transport.c b/src/src/routers/rf_get_transport.c
index 4a43818ff..32bde9ec3 100644
--- a/src/src/routers/rf_get_transport.c
+++ b/src/src/routers/rf_get_transport.c
@@ -66,10 +66,8 @@ if (expandable)
       "\"%s\" in %s router: %s", tpname, router_name, expand_string_message);
     return FALSE;
     }
-  if (is_tainted(ss))
+  if (is_tainted2(ss, LOG_MAIN|LOG_PANIC, "Tainted tainted value '%s' from '%s' for transport", ss, tpname))
     {
-    log_write(0, LOG_MAIN|LOG_PANIC,
-      "attempt to use tainted value '%s' from '%s' for transport", ss, tpname);
     addr->basic_errno = ERRNO_BADTRANSPORT;
     /* Avoid leaking info to an attacker */
     addr->message = US"internal configuration error";
diff --git a/src/src/search.c b/src/src/search.c
index 421d9c789..81d1d20f9 100644
--- a/src/src/search.c
+++ b/src/src/search.c
@@ -392,12 +392,8 @@ lookup_info *lk = lookup_list[search_type];
 uschar keybuffer[256];
 int old_pool = store_pool;
 
-if (filename && is_tainted(filename))
-  {
-  log_write(0, LOG_MAIN|LOG_PANIC,
-    "Tainted filename for search: '%s'", filename);
+if (filename && is_tainted2(filename, LOG_MAIN|LOG_PANIC, "Tainted filename for search: '%s'", filename))
   return NULL;
-  }
 
 /* Change to the search store pool and remember our reset point */
 
@@ -714,7 +710,7 @@ if (opts)
 /* Arrange to put this database at the top of the LRU chain if it is a type
 that opens real files. */
 
-if (  open_top != (tree_node *)handle 
+if (  open_top != (tree_node *)handle
    && lookup_list[t->name[0]-'0']->type == lookup_absfile)
   {
   search_cache *c = (search_cache *)(t->data.ptr);
diff --git a/src/src/smtp_out.c b/src/src/smtp_out.c
index f103c2752..4e8c44869 100644
--- a/src/src/smtp_out.c
+++ b/src/src/smtp_out.c
@@ -53,11 +53,8 @@ if (!(expint = expand_string(istring)))
   return FALSE;
   }
 
-if (is_tainted(expint))
+if (is_tainted2(expint, LOG_MAIN|LOG_PANIC, "Tainted value '%s' from '%s' for interface", expint, istring))
   {
-  log_write(0, LOG_MAIN|LOG_PANIC,
-    "attempt to use tainted value '%s' from '%s' for interface",
-    expint, istring);
   addr->transport_return = PANIC;
   addr->message = string_sprintf("failed to expand \"interface\" "
       "option for %s: configuration error", msg);
@@ -472,7 +469,7 @@ if (ob->socks_proxy)
   {
   int sock = socks_sock_connect(sc->host, sc->host_af, port, sc->interface,
 				sc->tblock, ob->connect_timeout);
-  
+
   if (sock >= 0)
     {
     if (early_data && early_data->data && early_data->len)
diff --git a/src/src/transports/appendfile.c b/src/src/transports/appendfile.c
index 139f9a3ef..5d957b62e 100644
--- a/src/src/transports/appendfile.c
+++ b/src/src/transports/appendfile.c
@@ -174,6 +174,9 @@ Arguments:
 Returns:     OK, FAIL, or DEFER
 */
 
+void
+open_logs(void);
+
 static int
 appendfile_transport_setup(transport_instance *tblock, address_item *addrlist,
   transport_feedback *dummy, uid_t uid, gid_t gid, uschar **errmsg)
@@ -183,6 +186,14 @@ appendfile_transport_options_block *ob =
 uschar *q = ob->quota;
 double default_value = 0.0;
 
+addrlist = addrlist;    /* Keep picky compilers happy */
+dummy = dummy;
+uid = uid;
+gid = gid;
+
+/* we can't wait until we're not privileged anymore */
+open_logs();
+
 if (ob->expand_maildir_use_size_file)
 	ob->maildir_use_size_file = expand_check_condition(ob->expand_maildir_use_size_file,
 		US"`maildir_use_size_file` in transport", tblock->name);
diff --git a/src/src/transports/autoreply.c b/src/src/transports/autoreply.c
index 865abbf4f..80c7c0db0 100644
--- a/src/src/transports/autoreply.c
+++ b/src/src/transports/autoreply.c
@@ -404,14 +404,15 @@ recipient cache. */
 
 if (oncelog && *oncelog && to)
   {
+  uschar *m;
   time_t then = 0;
 
-  if (is_tainted(oncelog))
+  if ((m = is_tainted2(oncelog, 0, "Tainted '%s' (once file for %s transport)"
+      " not permitted", oncelog, tblock->name)))
     {
     addr->transport_return = DEFER;
     addr->basic_errno = EACCES;
-    addr->message = string_sprintf("Tainted '%s' (once file for %s transport)"
-      " not permitted", oncelog, tblock->name);
+    addr->message = m;
     goto END_OFF;
     }
 
@@ -515,13 +516,14 @@ if (oncelog && *oncelog && to)
 
   if (then != 0 && (once_repeat_sec <= 0 || now - then < once_repeat_sec))
     {
+    uschar *m;
     int log_fd;
-    if (is_tainted(logfile))
+    if ((m = is_tainted2(logfile, 0, "Tainted '%s' (logfile for %s transport)"
+	" not permitted", logfile, tblock->name)))
       {
       addr->transport_return = DEFER;
       addr->basic_errno = EACCES;
-      addr->message = string_sprintf("Tainted '%s' (logfile for %s transport)"
-	" not permitted", logfile, tblock->name);
+      addr->message = m;
       goto END_OFF;
       }
 
@@ -548,12 +550,13 @@ if (oncelog && *oncelog && to)
 /* We are going to send a message. Ensure any requested file is available. */
 if (file)
   {
-  if (is_tainted(file))
+  uschar *m;
+  if ((m = is_tainted2(file, 0, "Tainted '%s' (file for %s transport)"
+      " not permitted", file, tblock->name)))
     {
     addr->transport_return = DEFER;
     addr->basic_errno = EACCES;
-    addr->message = string_sprintf("Tainted '%s' (file for %s transport)"
-      " not permitted", file, tblock->name);
+    addr->message = m;
     return FALSE;
     }
   if (!(ff = Ufopen(file, "rb")) && !ob->file_optional)
diff --git a/src/src/transports/pipe.c b/src/src/transports/pipe.c
index 1cb574ee7..da49307b1 100644
--- a/src/src/transports/pipe.c
+++ b/src/src/transports/pipe.c
@@ -592,13 +592,16 @@ if (!cmd || !*cmd)
     tblock->name);
   return FALSE;
   }
-if (is_tainted(cmd))
+
+{ uschar *m;
+if ((m = is_tainted2(cmd, 0, "Tainted '%s' (command "
+    "for %s transport) not permitted", cmd, tblock->name)))
   {
-  addr->message = string_sprintf("Tainted '%s' (command "
-    "for %s transport) not permitted", cmd, tblock->name);
   addr->transport_return = PANIC;
+  addr->message = m;
   return FALSE;
   }
+}
 
 /* When a pipe is set up by a filter file, there may be values for $thisaddress
 and numerical the variables in existence. These are passed in
diff --git a/src/src/transports/smtp.c b/src/src/transports/smtp.c
index 264ebc094..e2b2250ad 100644
--- a/src/src/transports/smtp.c
+++ b/src/src/transports/smtp.c
@@ -5092,11 +5092,8 @@ if (!hostlist || (ob->hosts_override && ob->hosts))
     else
       if (ob->hosts_randomize) s = expanded_hosts = string_copy(s);
 
-    if (is_tainted(s))
+    if (is_tainted2(s, LOG_MAIN|LOG_PANIC, "Tainted host list '%s' from '%s' in transport %s", s, ob->hosts, tblock->name))
       {
-      log_write(0, LOG_MAIN|LOG_PANIC,
-	"attempt to use tainted host list '%s' from '%s' in transport %s",
-	s, ob->hosts, tblock->name);
       /* Avoid leaking info to an attacker */
       addrlist->message = US"internal configuration error";
       addrlist->transport_return = PANIC;