SECURITY: fix Qualys CVE-2020-SLCWD

[exim.git] / src / src / macros.h

diff --git a/src/src/macros.h b/src/src/macros.h
index 72856a53b0b73ee89fb17f8a70b9802287512c42..f8987d60455f43febeec18eeae0e139e9ac549b9 100644 (file)
--- a/src/src/macros.h
+++ b/src/src/macros.h
@@ -154,7 +154,9 @@ enough to hold all the headers from a normal kind of message. */
 
 /* The initial size of a big buffer for use in various places. It gets put
 into big_buffer_size and in some circumstances increased. It should be at least
-as long as the maximum path length. */
+as long as the maximum path length PLUS room for string additions.
+Let's go with "at least twice as large as maximum path length".
+*/
 
 #ifdef AUTH_HEIMDAL_GSSAPI
                /* RFC 4121 section 5.2, SHOULD support 64K input buffers */
@@ -163,10 +165,12 @@ as long as the maximum path length. */
 # define __BIG_BUFFER_SIZE 16384
 #endif
 
-#if defined PATH_MAX && PATH_MAX > __BIG_BUFFER_SIZE
-# define BIG_BUFFER_SIZE PATH_MAX
-#elif defined MAXPATHLEN && MAXPATHLEN > __BIG_BUFFER_SIZE
-# define BIG_BUFFER_SIZE MAXPATHLEN
+#ifndef PATH_MAX
+/* exim.h will have ensured this exists before including us. */
+# error headers confusion, PATH_MAX missing in macros.h
+#endif
+#if (PATH_MAX*2) > __BIG_BUFFER_SIZE
+# define BIG_BUFFER_SIZE (PATH_MAX*2)
 #else
 # define BIG_BUFFER_SIZE __BIG_BUFFER_SIZE
 #endif