2 files changed, 35 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index 2240c725c..9b05c30f8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1674,7 +1674,6 @@ AC_CHECK_FUNCS([ \
         pstat \
         readpassphrase \
         reallocarray \
-        realpath \
         recvmsg \
         rresvport_af \
         sendmsg \
@@ -1891,6 +1890,32 @@ AC_CHECK_FUNCS([setresgid], [
         )
 ])
 
+AC_CHECK_FUNCS([realpath], [
+        dnl the sftp v3 spec says SSH_FXP_REALPATH will "canonicalize any given
+        dnl path name", however some implementations of realpath (and some
+        dnl versions of the POSIX spec) do not work on non-existent files,
+        dnl so we use the OpenBSD implementation on those platforms.
+        AC_MSG_CHECKING([if realpath works with non-existent files])
+        AC_RUN_IFELSE(
+                [AC_LANG_PROGRAM([[
+#include <limits.h>
+#include <stdlib.h>
+#include <errno.h>
+                ]], [[
+                char buf[PATH_MAX];
+                if (realpath("/opensshnonexistentfilename1234", buf) == NULL)
+                        if (errno == ENOENT)
+                                exit(1);
+                exit(0);
+                ]])],
+                [AC_MSG_RESULT([yes])],
+                [AC_DEFINE([BROKEN_REALPATH], [1],
+                        [realpath does not work with nonexistent files])
+                 AC_MSG_RESULT([no])],
+                [AC_MSG_WARN([cross compiling: assuming working])]
+        )
+])
+
 dnl    Checks for time functions
 AC_CHECK_FUNCS([gettimeofday time])
 dnl    Checks for utmp functions
diff --git a/openbsd-compat/openbsd-compat.h b/openbsd-compat/openbsd-compat.h
index cb59ccd57..1ff7114ef 100644
--- a/openbsd-compat/openbsd-compat.h
+++ b/openbsd-compat/openbsd-compat.h
@@ -70,8 +70,16 @@ void *reallocarray(void *, size_t, size_t);
 #endif
 
 #if !defined(HAVE_REALPATH) || defined(BROKEN_REALPATH)
+/*
+ * glibc's FORTIFY_SOURCE can redefine this and prevent us picking up the
+ * compat version.
+ */
+# ifdef BROKEN_REALPATH
+#  define realpath(x, y) _ssh_compat_realpath(x, y)
+# endif
+
 char *realpath(const char *path, char *resolved);
-#endif 
+#endif
 
 #ifndef HAVE_RRESVPORT_AF
 int rresvport_af(int *alport, sa_family_t af);