[Bug 980835] Re: tty[1-6] is now root:tty 0660 instead of root:root 0600

[Adam Conrad]

This is actually the code responsible:

@@ -686,12 +770,16 @@ static void open_tty(char *tty, struct termios *tp, struct options *op)
                log_err("%s: tcgetattr: %m", tty);
 
        /*
-        * Linux login(1) will change tty permissions. Use root owner and group
-        * with permission -rw------- for the period between getty and login.
+        * Detect if this is a virtual console or serial/modem line.
+        * In case of a virtual console the ioctl TIOCMGET fails and
+        * the error number will be set to EINVAL.
         */
-       ignore_result(chown(tty, 0, 0));
-       ignore_result(chmod(tty, 0600));
-       errno = 0;
+       if (ioctl(STDIN_FILENO, TIOCMGET, &serial) < 0 && (errno = EINVAL)) {
+               op->flags |= F_VCONSOLE;
+               if (!op->term)
+                       op->term = DEFAULT_VCTERM;
+       } else if (!op->term)
+               op->term = DEFAULT_STERM;
 
        setenv("TERM", op->term, 1);
 }

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https://bugs.launchpad.net/bugs/980835

Title:
  tty[1-6] is now root:tty 0660 instead of root:root 0600

Status in “util-linux” package in Ubuntu:
  New

Bug description:
  As of precise (2.20.1-1ubuntu3 to be exact), /dev/tty[1-6] now has the following permissions:
  $ ls -l /dev/tty[1-6]
  crw-rw---- 1 root tty 4, 1 Apr 12 13:06 /dev/tty1
  crw-rw---- 1 root tty 4, 2 Apr 12 13:06 /dev/tty2
  crw-rw---- 1 root tty 4, 3 Apr 12 13:06 /dev/tty3
  crw-rw---- 1 root tty 4, 4 Apr 12 13:06 /dev/tty4
  crw-rw---- 1 root tty 4, 5 Apr 12 13:06 /dev/tty5
  crw-rw---- 1 root tty 4, 6 Apr 12 13:06 /dev/tty6

  In 11.10 and earlier (I checked back to hardy), the permissions were:
  $ ls -l /dev/tty[1-6]
  crw------- 1 root root 4, 1 2012-03-25 09:18 /dev/tty1
  crw------- 1 root root 4, 2 2012-03-25 09:17 /dev/tty2
  crw------- 1 root root 4, 3 2012-03-25 09:17 /dev/tty3
  crw------- 1 root root 4, 4 2012-03-25 09:17 /dev/tty4
  crw------- 1 root root 4, 5 2012-03-25 09:17 /dev/tty5
  crw------- 1 root root 4, 6 2012-03-25 09:17 /dev/tty6

  This appears to be because of this util-linux commit:
  http://git.kernel.org/?p=utils/util-linux/util-linux.git;a=commit;h=3aa6b68f7e19fa3e1c2bba75bee921a98b7b46af

  I'm not sure if this is a problem, but it isn't clear why the change was made and I'm having a hard time knowing why the group was changed. This is the bit of code that I think is the cause:
  +               /*
  +                * There is always a race between this reset and the call to
  +                * vhangup() that s.o. can use to get access to your tty.
  +                * Linux login(1) will change tty permissions. Use root owner and group
  +                * with permission -rw------- for the period between getty and login.
  +                */
  +               if (chown (buf, 0, gid) || chmod (buf, (gid ? 0660 : 0600))) {
  +                       if (errno == EROFS)
  +                               log_warn("%s: %m", buf);
  +                       else
  +                               log_err("%s: %m", buf);
  +               }

  There might not be anything to do with this, but I am filing it to get
  other's opinions.

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