[PATCH] mkstemp: replace if system version uses wrong permissions

[Eric Blake]

From: Reuben Thomas <address@hidden>

* m4/mkstemp.m4 (gl_FUNC_MKSTEMP): Add test for non-owner
read/write mode bits set in file created by mkstemp.
* doc/posix-functions/mkstemp.texi (mkstemp): Document the fix.

Signed-off-by: Eric Blake <address@hidden>
---

Here's the final version I'd like to push.  It's modified a bit from
your version; are you okay with it still being in your name?

I tested on HP-UX 10.20 (which still has a cap on the maximum
number of mkstemp invocations, but surprisingly used correct
permissions); as well as verified that Solaris, BSD, Cygwin,
AIX, and Tru64 5.1 still passed.

 ChangeLog                        |    5 +++++
 doc/posix-functions/mkstemp.texi |    8 ++++----
 m4/mkstemp.m4                    |   13 +++++++++++--
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 247d541..958d993 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,11 @@
 2011-04-27  Reuben Thomas  <address@hidden>
        and Eric Blake  <address@hidden>

+       mkstemp: replace if system version uses wrong permissions
+       * m4/mkstemp.m4 (gl_FUNC_MKSTEMP): Add test for non-owner
+       read/write mode bits set in file created by mkstemp.
+       * doc/posix-functions/mkstemp.texi (mkstemp): Document the fix.
+
        mkstemp: mention clean-temp module
        * lib/mkstemp.c: Add comment.
        * doc/posix-functions/mkstemp.texi (mkstemp): Likewise.
diff --git a/doc/posix-functions/mkstemp.texi b/doc/posix-functions/mkstemp.texi
index 5a1e145..5f62b44 100644
--- a/doc/posix-functions/mkstemp.texi
+++ b/doc/posix-functions/mkstemp.texi
@@ -15,14 +15,14 @@ mkstemp
 On some platforms (HP-UX 10.20, SunOS 4.1.4, Solaris 2.5.1), mkstemp has a 
silly
 limit that it can create no more than 26 files from a given template.  On
 OSF/1 4.0f, it can create only 32 files per process.
address@hidden
+On some older platforms, @code{mkstemp} can create a world or group
+writable or readable file, if you haven't set the process umask to
+077.  This is a security risk.
 @end itemize

 Portability problems not fixed by Gnulib:
 @itemize
address@hidden
-On platforms other than glibc 2.0.7 or newer, @code{mkstemp} can create a
-world or group writable or readable file, if you haven't set the process
-umask to 077.  This is a security risk.
 @end itemize

 The gnulib module clean-temp can create temporary files that are less
diff --git a/m4/mkstemp.m4 b/m4/mkstemp.m4
index c5cd282..06187c6 100644
--- a/m4/mkstemp.m4
+++ b/m4/mkstemp.m4
@@ -1,4 +1,4 @@
-#serial 19
+#serial 20

 # Copyright (C) 2001, 2003-2007, 2009-2011 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
@@ -10,6 +10,8 @@
 # Other systems lack mkstemp altogether.
 # On OSF1/Tru64 V4.0F, the system-provided mkstemp function can create
 # only 32 files per process.
+# On some hosts, mkstemp creates files with mode 0666, which is a security
+# problem and a violation of POSIX 2008.
 # On systems like the above, arrange to use the replacement function.
 AC_DEFUN([gl_FUNC_MKSTEMP],
 [
@@ -30,6 +32,7 @@ AC_DEFUN([gl_FUNC_MKSTEMP],
               off_t large = (off_t) 4294967295u;
               if (large < 0)
                 large = 2147483647;
+              umask (0);
               for (i = 0; i < 70; i++)
                 {
                   char templ[] = "conftest.mkstemp/coXXXXXX";
@@ -39,9 +42,15 @@ AC_DEFUN([gl_FUNC_MKSTEMP],
                     result |= 1;
                   else
                     {
+                      struct stat st;
                       if (lseek (fd, large, SEEK_SET) != large)
                         result |= 2;
-                      close (fd);
+                      if (fstat (fd, &st) < 0)
+                        result |= 4;
+                      else if (st.st_mode & 0077)
+                        result |= 8;
+                      if (close (fd))
+                        result |= 16;
                     }
                 }
               return result;]])],
-- 
1.7.4.4