SEO

Hi,

The crontab -e fix I suggested was just symptom-treatment and
therefore an inferior solution. But I was on the track of a
problem.

The problem comes down to the following: editors should not be
allowed to create backupfiles in worldwritable directories since
the backupfilename is very predictable.

Here is a patch for mg which implements this idea. The comments
also mention other problems so it should be used for consideration
only.


Index: fileio.c
================================================== =================
RCS file: /cvs/src/usr.bin/mg/fileio.c,v
retrieving revision 1.43
diff -u -w -p -r1.43 fileio.c
--- fileio.c 11 Jan 2005 17:19:16 -0000 1.43
+++ fileio.c 30 Jan 2005 10:20:25 -0000
@@ -153,14 +153,25 @@ ffgetline(char *buf, int nbuf, int *nbyt
* with an open fd will get the backup, not the new file. This is
* a problem when using mg with things like crontab and vipw.
*/
+
+/*
+ * Which is an inferior solution to the problem, It's better to *
+ * refuse to make backupfiles in worldwritable-dirs
+ */
+
+/* Another caveat: ewprintf notices are lost if return FALSE is
+ * used since they are overwritten at once. */
+
int
fbackupfile(const char *fn)
{
- struct stat sb;
+ struct stat sb, sd;
int from, to, serrno;
ssize_t nread;
char buf[BUFSIZ];
char *nname;
+ char *wdir;
+ static char cwd[NFILEN];

if (stat(fn, &sb) == -1) {
ewprintf("Can't stat %s : %s", fn, strerror(errno));
@@ -173,6 +184,24 @@ fbackupfile(const char *fn)
return (ABORT);
}

+ if ((wdir = getcwd(cwd, sizeof(cwd))) == NULL) {
+ ewprintf("Can't get current directory!");
+ return (FALSE);
+ }
+
+ if (stat(cwd, &sd) == -1) {
+ ewprintf("Can't stat %s : %s", cwd, strerror(errno));
+ return (FALSE);
+ }
+
+ /* We don't want to create backupfiles in world-writable
+ * directories, like /tmp, since the filename is predic-
+ * table */
+ if (sd.st_mode & S_IWOTH ) {
+ ewprintf("I refuse to create backupfiles in worldwritable dir: %s", wdir);
+ return(FALSE);
+ }
+
if ((from = open(fn, O_RDONLY)) == -1) {
free(nname);
return (FALSE);


# Han