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

[Anthony Liguori]

Paul Moore <address@hidden> writes:

> 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 <address@hidden>
>
> 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.

I asked for the specific language in FIPS mandating this.  I don't see
any other VNC server implementing a check like this.  I would rather do
this in a more user friendly fashion like make it a config file option
that a user can set while in fips mode.

Regards,

Anthony Liguori

>
> -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