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Re: [libvirt] [PATCH 01/12] Add bounds checking on virDomainMigrate*Params RPC calls (CVE-2013-4292)



On Thu, Aug 29, 2013 at 02:58:44PM +0200, Michal Privoznik wrote:
> On 29.08.2013 14:55, Daniel P. Berrange wrote:
> > On Thu, Aug 29, 2013 at 02:34:15PM +0200, Michal Privoznik wrote:
> >> On 29.08.2013 12:49, Daniel P. Berrange wrote:
> >>> From: "Daniel P. Berrange" <berrange redhat com>
> >>>
> >>> The parameters for the virDomainMigrate*Params RPC calls were
> >>> not bounds checks, meaning a malicious client can cause libvirtd
> >>> to consume arbitrary memory
> >>>
> >>> This issue was introduced in the 1.1.0 release of libvirt
> >>>
> >>> Signed-off-by: Daniel P. Berrange <berrange redhat com>
> >>> ---
> >>>  daemon/remote.c              | 42 ++++++++++++++++++++++++++++++++++++++++++
> >>>  src/remote/remote_driver.c   | 42 ++++++++++++++++++++++++++++++++++++++++++
> >>>  src/remote/remote_protocol.x | 15 +++++++++------
> >>>  3 files changed, 93 insertions(+), 6 deletions(-)
> >>>
> >>> diff --git a/daemon/remote.c b/daemon/remote.c
> >>> index 03d5557..a11ba94 100644
> >>> --- a/daemon/remote.c
> >>> +++ b/daemon/remote.c
> >>> @@ -4620,6 +4620,13 @@ remoteDispatchDomainMigrateBegin3Params(
> >>>          goto cleanup;
> >>>      }
> >>>  
> >>> +    if (args->params.params_len > REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX) {
> >>> +        virReportError(VIR_ERR_RPC,
> >>> +                       _("Too many migration parameters '%d' for limit '%d'"),
> >>> +                       args->params.params_len, REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX);
> >>> +        goto cleanup;
> >>> +    }
> >>> +
> >>>      if (!(dom = get_nonnull_domain(priv->conn, args->dom)))
> >>>          goto cleanup;
> >>>  
> >>> @@ -4671,6 +4678,13 @@ remoteDispatchDomainMigratePrepare3Params(
> >>>          goto cleanup;
> >>>      }
> >>>  
> >>> +    if (args->params.params_len > REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX) {
> >>> +        virReportError(VIR_ERR_RPC,
> >>> +                       _("Too many migration parameters '%d' for limit '%d'"),
> >>> +                       args->params.params_len, REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX);
> >>> +        goto cleanup;
> >>> +    }
> >>> +
> >>>      if (!(params = remoteDeserializeTypedParameters(args->params.params_val,
> >>>                                                      args->params.params_len,
> >>>                                                      0, &nparams)))
> >>> @@ -4726,6 +4740,13 @@ remoteDispatchDomainMigratePrepareTunnel3Params(
> >>>          goto cleanup;
> >>>      }
> >>>  
> >>> +    if (args->params.params_len > REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX) {
> >>> +        virReportError(VIR_ERR_RPC,
> >>> +                       _("Too many migration parameters '%d' for limit '%d'"),
> >>> +                       args->params.params_len, REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX);
> >>> +        goto cleanup;
> >>> +    }
> >>> +
> >>>      if (!(params = remoteDeserializeTypedParameters(args->params.params_val,
> >>>                                                      args->params.params_len,
> >>>                                                      0, &nparams)))
> >>> @@ -4790,6 +4811,13 @@ remoteDispatchDomainMigratePerform3Params(
> >>>          goto cleanup;
> >>>      }
> >>>  
> >>> +    if (args->params.params_len > REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX) {
> >>> +        virReportError(VIR_ERR_RPC,
> >>> +                       _("Too many migration parameters '%d' for limit '%d'"),
> >>> +                       args->params.params_len, REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX);
> >>> +        goto cleanup;
> >>> +    }
> >>> +
> >>>      if (!(dom = get_nonnull_domain(priv->conn, args->dom)))
> >>>          goto cleanup;
> >>>  
> >>> @@ -4845,6 +4873,13 @@ remoteDispatchDomainMigrateFinish3Params(
> >>>          goto cleanup;
> >>>      }
> >>>  
> >>> +    if (args->params.params_len > REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX) {
> >>> +        virReportError(VIR_ERR_RPC,
> >>> +                       _("Too many migration parameters '%d' for limit '%d'"),
> >>> +                       args->params.params_len, REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX);
> >>> +        goto cleanup;
> >>> +    }
> >>> +
> >>>      if (!(params = remoteDeserializeTypedParameters(args->params.params_val,
> >>>                                                      args->params.params_len,
> >>>                                                      0, &nparams)))
> >>> @@ -4897,6 +4932,13 @@ remoteDispatchDomainMigrateConfirm3Params(
> >>>          goto cleanup;
> >>>      }
> >>>  
> >>> +    if (args->params.params_len > REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX) {
> >>> +        virReportError(VIR_ERR_RPC,
> >>> +                       _("Too many migration parameters '%d' for limit '%d'"),
> >>> +                       args->params.params_len, REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX);
> >>> +        goto cleanup;
> >>> +    }
> >>> +
> >>>      if (!(dom = get_nonnull_domain(priv->conn, args->dom)))
> >>>          goto cleanup;
> >>
> >> While the above is correct as it fixes the libvirtd (sanitizes input).
> >> However, I don't think we need the following, esp. if we ever change the
> >> limit. The older client won't be able to pass more parameters whereas it
> >> currently can.
> > 
> > As mentioned in the cover letter, we explicitly want to check data
> > received from the server, because this is a robustness issue. If the
> > data stream gets corrupted for some reason, it can cause the client
> > to allocate unbounded amounts of memory. We want to prevent that.
> > 
> > Compatibility when raising limits is already going to be a problem,
> > because the generated xdr methods for decoding the return values will
> > be enforcing this limit. They have really crappy (ie non-existant)
> > error reporting, so the user wil just get a "Unable to decode message
> > payload" error message. These explicit checks in libvirt code ensure
> > we get a useful error message instead.
> > 
> >>> diff --git a/src/remote/remote_protocol.x b/src/remote/remote_protocol.x
> >>> index 7cfebdf..4262c34 100644
> >>> --- a/src/remote/remote_protocol.x
> >>> +++ b/src/remote/remote_protocol.x
> >>> @@ -234,6 +234,9 @@ const REMOTE_DOMAIN_DISK_ERRORS_MAX = 256;
> >>>   */
> >>>  const REMOTE_NODE_MEMORY_PARAMETERS_MAX = 64;
> >>>  
> >>> +/* Upper limit on migrate parameters */
> >>> +const REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX = 64;
> >>> +
> >>>  /* UUID.  VIR_UUID_BUFLEN definition comes from libvirt.h */
> >>>  typedef opaque remote_uuid[VIR_UUID_BUFLEN];
> >>>  
> >>> @@ -2770,7 +2773,7 @@ struct remote_domain_fstrim_args {
> >>>  
> >>>  struct remote_domain_migrate_begin3_params_args {
> >>>      remote_nonnull_domain dom;
> >>> -    remote_typed_param params<>;
> >>> +    remote_typed_param params<REMOTE_DOMAIN_MIGRATE_PARAM_LIST_MAX>;
> >>>      unsigned int flags;
> >>>  };
> >>
> >> Moreover, after you introduce this - won't XDR complain if we try to
> >> encode more than _MAX items?
> > 
> > Yes, it will return an error both at decode or encode time if the
> > length exceeds the limit. We want to get better error reporting
> > though, hence duplicating the checks ourselves.
> > 
> > One day we really ought to just throw away the XDR library code and
> > write our own, can we can dynamic buffer allocation and sensible
> > error reporting.
> > 
> > Daniel
> > 
> 
> Aah, okay. Thanks for your explanation. Makes sense now. In that case:
> ACK series and I vote for push now, prior the release.

Thanks, I pushed this series to master, and the CVE patch I have pushed
to v1.1.0-maint and v1.1.1-maint too


Daniel
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