common: Use new function to print status strings.

* common/asshelp2.c (vprint_assuan_status_strings): New.
(print_assuan_status_strings): New.
* agent/command.c (agent_write_status): Replace by call to new
function.
* dirmngr/server.c (dirmngr_status): Ditto.
* g13/server.c (g13_status): Ditto.
* g13/sh-cmd.c (g13_status): Ditto.
* sm/server.c (gpgsm_status2): Ditto.
* scd/command.c (send_status_info): Bump up N.
--

This fixes a potential overflow if LFs are passed to the status
string functions.  This is actually not the case and would be wrong
because neither the truncating in libassuan or our escaping is not the
Right Thing.  In any case the functions need to be more robust and
comply to the promised interface.  Thus the code has been factored out
to a helper function and N has been bumped up correctly and checked in
all cases.

For some uses this changes the behaviour in the error case (i.e. CR or
LF passed): It will now always be C-escaped and not passed to
libassuan which would truncate the line at the first LF.

Reported-by: private_pers

common/asshelp.h

@@ -93,5 +93,12 @@ gpg_error_t vprint_assuan_status (assuan_context_t ctx,
                                   const char *format,
                                   va_list arg_ptr) GPGRT_ATTR_PRINTF(3,0);
 
+gpg_error_t vprint_assuan_status_strings (assuan_context_t ctx,
+                                          const char *keyword,
+                                          va_list arg_ptr);
+gpg_error_t print_assuan_status_strings (assuan_context_t ctx,
+                                         const char *keyword,
+                                         ...) GPGRT_ATTR_SENTINEL(1);
+
 
 #endif /*GNUPG_COMMON_ASSHELP_H*/

common/asshelp2.c

@@ -71,3 +71,66 @@ print_assuan_status (assuan_context_t ctx,
   va_end (arg_ptr);
   return err;
 }
+
+
+/* Helper function to print a list of strings as an assuan status
+ * line.  KEYWORD is the first item on the status line.  ARG_PTR is a
+ * list of strings which are all separated by a space in the output.
+ * The last argument must be a NULL.  Linefeeds and carriage returns
+ * characters (which are not allowed in an Assuan status line) are
+ * silently quoted in C-style.  */
+gpg_error_t
+vprint_assuan_status_strings (assuan_context_t ctx,
+                              const char *keyword, va_list arg_ptr)
+{
+  gpg_error_t err = 0;
+  const char *text;
+  char buf[950], *p;
+  size_t n;
+
+  p = buf;
+  n = 0;
+  while ((text = va_arg (arg_ptr, const char *)) && n < DIM (buf)-3 )
+    {
+      if (n)
+        {
+          *p++ = ' ';
+          n++;
+        }
+      for ( ; *text && n < DIM (buf)-3; n++, text++)
+        {
+          if (*text == '\n')
+            {
+              *p++ = '\\';
+              *p++ = 'n';
+              n++;
+            }
+          else if (*text == '\r')
+            {
+              *p++ = '\\';
+              *p++ = 'r';
+              n++;
+            }
+          else
+            *p++ = *text;
+        }
+    }
+  *p = 0;
+  err = assuan_write_status (ctx, keyword, buf);
+
+  return err;
+}
+
+
+/* See vprint_assuan_status_strings.  */
+gpg_error_t
+print_assuan_status_strings (assuan_context_t ctx, const char *keyword, ...)
+{
+  va_list arg_ptr;
+  gpg_error_t err;
+
+  va_start (arg_ptr, keyword);
+  err = vprint_assuan_status_strings (ctx, keyword, arg_ptr);
+  va_end (arg_ptr);
+  return err;
+}