Re: [Qemu-devel] [PATCH] vnc: disable VNC password authentication (security type 2) when in FIPS mode

[George Wilson]

Anthony Liguori <address@hidden> wrote on 05/01/2012 06:26:05 PM:

> Anthony Liguori <address@hidden>
> 05/01/2012 06:26 PM
>
> To
>
> Paul Moore <address@hidden>
>
> cc
>
> address@hidden, George Wilson/Austin/address@hidden
>
> Subject
>
> Re: [Qemu-devel] [PATCH] vnc: disable VNC password authentication
> (security type 2) when in FIPS mode
>
> On 05/01/2012 04:20 PM, Paul Moore wrote:
> > FIPS 140-2 requires disabling certain ciphers, including DES, which is used
> > by VNC to obscure passwords when they are sent over the network.  The
> > solution for FIPS users is to disable the use of VNC password auth when the
> > host system is operating in FIPS mode.
>
> Sorry, what?
>
> Does FIPS really require software to detect when FIPS is enabled andactively
> disable features???  That's absurd.
>
> Can you point to another software package that does something like this?

Yes, it's true that only FIPS-approved algorithms are permitted for use in FIPS
mode.  The kernel and all other FIPS 140-2 validated crypto modules like OpenSSL
and NSS are required to restrict algorithms to the approved set.  The kernel
sets /proc/sys/crypto/fips_enabled so that programs can detect FIPS mode and
behave in accordance with the standard.

>
> Regards,
>
> Anthony Liguori
>
> >
> > This patch causes qemu to emits a syslog entry indicating that VNC password
> > auth is disabled when it detects the host is running in FIPS mode, and
> > unless a VNC password was specified on the command line it continues
> > normally.  However, if a VNC password was given on the command line, qemu
> > fails with an error message to stderr explaining that that VNC password
> > auth is not allowed in FIPS mode.
> >
> > Signed-off-by: Paul Moore<address@hidden>
> > ---
> >   qemu-doc.texi |    8 +++++---
> >   ui/vnc.c      |   32 ++++++++++++++++++++++++++++++++
> >   ui/vnc.h      |    1 +
> >   3 files changed, 38 insertions(+), 3 deletions(-)
> >
> > diff --git a/qemu-doc.texi b/qemu-doc.texi
> > index e5d7ac4..f9b113e 100644
> > --- a/qemu-doc.texi
> > +++ b/qemu-doc.texi
> > @@ -1124,9 +1124,11 @@ the protocol limits passwords to 8
> characters it should not be considered
> >   to provide high security. The password can be fairly easily
> brute-forced by
> >   a client making repeat connections. For this reason, a VNC
> server using password
> >   authentication should be restricted to only listen on the
> loopback interface
> > -or UNIX domain sockets. Password authentication is requested with
> the @code{password}
> > -option, and then once QEMU is running the password is set with
> the monitor. Until
> > -the monitor is used to set the password all clients will be rejected.
> > +or UNIX domain sockets. Password authentication is not supported
> when operating
> > +in FIPS 140-2 compliance mode as it requires the use of the DES
> cipher. Password
> > +authentication is requested with the @code{password} option, and
> then once QEMU
> > +is running the password is set with the monitor. Until the
> monitor is used to
> > +set the password all clients will be rejected.
> >
> >   @example
> >   qemu [...OPTIONS...] -vnc :1,password -monitor stdio
> > diff --git a/ui/vnc.c b/ui/vnc.c
> > index deb9ecd..620791e 100644
> > --- a/ui/vnc.c
> > +++ b/ui/vnc.c
> > @@ -32,6 +32,7 @@
> >   #include "acl.h"
> >   #include "qemu-objects.h"
> >   #include "qmp-commands.h"
> > +#include<syslog.h>
> >
> >   #define VNC_REFRESH_INTERVAL_BASE 30
> >   #define VNC_REFRESH_INTERVAL_INC  50
> > @@ -48,6 +49,24 @@ static DisplayChangeListener *dcl;
> >   static int vnc_cursor_define(VncState *vs);
> >   static void vnc_release_modifiers(VncState *vs);
> >
> > +static int fips_enabled(void)
> > +{
> > +    int enabled = 0;
> > +    char value;
> > +    FILE *fds;
> > +
> > +    fds = fopen("/proc/sys/crypto/fips_enabled", "r");
> > +    if (fds == NULL) {
> > +        return 0;
> > +    }
> > +    if (fread(&value, sizeof(value), 1, fds) == 1&&  value == '1') {
> > +        enabled = 1;
> > +    }
> > +    fclose(fds);
> > +
> > +    return enabled;
> > +}
> > +
> >   static void vnc_set_share_mode(VncState *vs, VncShareMode mode)
> >   {
> >   #ifdef _VNC_DEBUG
> > @@ -2748,6 +2767,12 @@ void vnc_display_init(DisplayState *ds)
> >       dcl->idle = 1;
> >       vnc_display = vs;
> >
> > +    vs->fips = fips_enabled();
> > +    VNC_DEBUG("FIPS mode %s\n", (vs->fips ? "enabled" : "disabled"));
> > +    if (vs->fips) {
> > +        syslog(LOG_NOTICE, "Disabling VNC password auth due to
> FIPS mode\n");
> > +    }
> > +
> >       vs->lsock = -1;
> >
> >       vs->ds = ds;
> > @@ -2892,6 +2917,13 @@ int vnc_display_open(DisplayState *ds,
> const char *display)
> >       while ((options = strchr(options, ','))) {
> >           options++;
> >           if (strncmp(options, "password", 8) == 0) {
> > +            if (vs->fips) {
> > +                fprintf(stderr,
> > +                        "VNC password auth disabled due to FIPS mode\n");
> > +                g_free(vs->display);
> > +                vs->display = NULL;
> > +                return -1;
> > +            }
> >               password = 1; /* Require password auth */
> >           } else if (strncmp(options, "reverse", 7) == 0) {
> >               reverse = 1;
> > diff --git a/ui/vnc.h b/ui/vnc.h
> > index a851ebd..8746a98 100644
> > --- a/ui/vnc.h
> > +++ b/ui/vnc.h
> > @@ -160,6 +160,7 @@ struct VncDisplay
> >       char *display;
> >       char *password;
> >       time_t expires;
> > +    int fips;
> >       int auth;
> >       bool lossy;
> >       bool non_adaptive;
> >
> >
> >
>

Regards,
George Wilson