Re: [Qemu-devel] [PATCH v4] vnc: disable VNC password authentication (security type 2) when in FIPS mode

[Paul Moore <pmoore@redhat.com>]

On Friday, June 08, 2012 05:38:12 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.
> 
> This patch causes QEMU to emit a message to stderr when the host system is
> running in FIPS mode and a VNC password was specified on the commend line.
> If the system is not running in FIPS mode, or is running in FIPS mode but
> VNC password authentication was not requested, QEMU operates normally.
> 
> Signed-off-by: Paul Moore <pmoore@redhat.com>

Hi Anthony,

Any word on this patch?  Other than Daniel Berrange's reviewed-by tag, the 
discussion of the v4 patch has been quiet and I think we addressed all the 
other remaining issues in the discussion attached to the v2 patch posting.

-Paul

> --
> Changelog
> * v4
> - Removed the use of syslog
> * v3
> - Use fgetc() instead of fgets() in fips_enabled
> - Only emit a syslog message if the caller tries to use VNC password auth
> - Suggest alternative auth methods in the stderr notice
> * v2
> - Protected syslog with _WIN32
> - Protected the guts of fips_enabled() with __linux__
> - Converted fips_enabled() and the fips flag from int to bool
> *v1
> - Initial draft
> ---
>  qemu-doc.texi |    8 +++++---
>  ui/vnc.c      |   27 +++++++++++++++++++++++++++
>  ui/vnc.h      |    1 +
>  3 files changed, 33 insertions(+), 3 deletions(-)
> 
> diff --git a/qemu-doc.texi b/qemu-doc.texi
> index 0af0ff4..fe8d3df 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-system-i386 [...OPTIONS...] -vnc :1,password -monitor stdio
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 54bc5ad..4bd816d 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -48,6 +48,21 @@ static DisplayChangeListener *dcl;
>  static int vnc_cursor_define(VncState *vs);
>  static void vnc_release_modifiers(VncState *vs);
> 
> +static bool fips_enabled(void)
> +{
> +    bool enabled = false;
> +
> +#ifdef __linux__
> +    FILE *fds = fopen("/proc/sys/crypto/fips_enabled", "r");
> +    if (fds != NULL) {
> +        enabled = (fgetc(fds) == '1');
> +        fclose(fds);
> +    }
> +#endif /* __linux__ */
> +
> +    return enabled;
> +}
> +
>  static void vnc_set_share_mode(VncState *vs, VncShareMode mode)
>  {
>  #ifdef _VNC_DEBUG
> @@ -2748,6 +2763,9 @@ 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"));
> +
>      vs->lsock = -1;
> 
>      vs->ds = ds;
> @@ -2896,6 +2914,15 @@ 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, "
> +                        "consider using the VeNCrypt or SASL authentication
> " +                        "methods as an alternative\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..d41631b 100644
> --- a/ui/vnc.h
> +++ b/ui/vnc.h
> @@ -160,6 +160,7 @@ struct VncDisplay
>      char *display;
>      char *password;
>      time_t expires;
> +    bool fips;
>      int auth;
>      bool lossy;
>      bool non_adaptive;
-- 
paul moore
security and virtualization @ redhat