* files.c (do_writeout): Also abort on writing a backup

          file when its owner doesn't match the edited file.

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@4491 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

diff --git a/ChangeLog b/ChangeLog
index 3c4edf96e741c214641bc5f968cc892733c6efb4..fceeddaf57314b9200deb89da7862c341fceba50 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,8 +1,9 @@
 2010-04-02 Chris Allegretta <chrisa@asty.org>
        * files.c (do_writeout): Expand modification check to include both the
          original file's device ID and inode number as reasons to warn the 
-          user that the file has been modified.  Based on security article on nano
-          by Dan Rosenberg.
+          user that the file has been modified.  Also abort on writing a backup
+         file when its owner doesn't match the edited file. Based on security 
+         analysis on nano by Dan Rosenberg.
 
 2010-03-21 Chris Allegretta <chrisa@asty.org>
        * nano.c (page_stdin et al): Don't attempt to reset/reopen the terminal

diff --git a/src/files.c b/src/files.c
index 8e63903a884a621d93c2deaeb65e83b48826a998..632c0f9ab4790e59bc91a76dd836ad6c3caff266 100644 (file)
--- a/src/files.c
+++ b/src/files.c
@@ -1519,6 +1519,7 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
        char *backupname;
        struct utimbuf filetime;
        int copy_status;
+       struct stat backupst;
 
        /* Save the original file's access and modification times. */
        filetime.actime = openfile->current_stat->st_atime;
@@ -1588,6 +1589,15 @@ bool write_file(const char *name, FILE *f_open, bool tmp, append_type
            sprintf(backupname, "%s~", realname);
        }
 
+       if (stat(backupname, &backupst) != -1 &&
+           (backupst.st_uid != st.st_uid)) {
+           statusbar(_("Error writing backup file %s: Permission mismatch"), backupname,
+               strerror(errno));
+           free(backupname);
+           goto cleanup_and_exit;
+       }
+
+
        /* Open the destination backup file.  Before we write to it, we
         * set its permissions, so no unauthorized person can read it as
         * we write. */