[Buildroot] [PATCH 1/5] package/gvfs: fix CVE-2019-3827

[Yann E. MORIN <yann.morin.1998@free.fr>]

Fabrice, All,

On 2020-03-29 18:02 +0200, Fabrice Fontaine spake thusly:
> An incorrect permission check in the admin backend in gvfs before
> version 1.39.4 was found that allows reading and modify arbitrary files
> by privileged users without asking for password when no authentication
> agent is running. This vulnerability can be exploited by malicious
> programs running under privileges of users belonging to the wheel group
> to further escalate its privileges by modifying system files without
> user's knowledge. Successful exploitation requires uncommon system
> configuration.
> 
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>

Patch series applied to master, thanks.

Any reason why you sent one patch for each CVE, rather than a single
patch?

Regards,
Yann E. MORIN.

> ---
>  ...authentication-agent-isn-t-available.patch | 46 +++++++++++++++++++
>  package/gvfs/gvfs.mk                          |  3 ++
>  2 files changed, 49 insertions(+)
>  create mode 100644 package/gvfs/0001-admin-Prevent-access-if-any-authentication-agent-isn-t-available.patch
> 
> diff --git a/package/gvfs/0001-admin-Prevent-access-if-any-authentication-agent-isn-t-available.patch b/package/gvfs/0001-admin-Prevent-access-if-any-authentication-agent-isn-t-available.patch
> new file mode 100644
> index 0000000000..2715371534
> --- /dev/null
> +++ b/package/gvfs/0001-admin-Prevent-access-if-any-authentication-agent-isn-t-available.patch
> @@ -0,0 +1,46 @@
> +From d8d0c8c40049cfd824b2b90d0cd47914052b9811 Mon Sep 17 00:00:00 2001
> +From: Ondrej Holy <oholy@redhat.com>
> +Date: Wed, 2 Jan 2019 17:13:27 +0100
> +Subject: [PATCH] admin: Prevent access if any authentication agent isn't
> + available
> +
> +The backend currently allows to access and modify files without prompting
> +for password if any polkit authentication agent isn't available. This seems
> +isn't usually problem, because polkit agents are integral parts of
> +graphical environments / linux distributions. The agents can't be simply
> +disabled without root permissions and are automatically respawned. However,
> +this might be a problem in some non-standard cases.
> +
> +This affects only users which belong to wheel group (i.e. those who are
> +already allowed to use sudo). It doesn't allow privilege escalation for
> +users, who don't belong to that group.
> +
> +Let's return permission denied error also when the subject can't be
> +authorized by any polkit agent to prevent this behavior.
> +
> +Closes: https://gitlab.gnome.org/GNOME/gvfs/issues/355
> +
> +Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> +[Retrieved from:
> +https://gitlab.gnome.org/GNOME/gvfs/commit/d8d0c8c40049cfd824b2b90d0cd47914052b9811]
> +---
> + daemon/gvfsbackendadmin.c | 3 +--
> + 1 file changed, 1 insertion(+), 2 deletions(-)
> +
> +diff --git a/daemon/gvfsbackendadmin.c b/daemon/gvfsbackendadmin.c
> +index ec0f2392..0f849008 100644
> +--- a/daemon/gvfsbackendadmin.c
> ++++ b/daemon/gvfsbackendadmin.c
> +@@ -130,8 +130,7 @@ check_permission (GVfsBackendAdmin *self,
> +       return FALSE;
> +     }
> + 
> +-  is_authorized = polkit_authorization_result_get_is_authorized (result) ||
> +-    polkit_authorization_result_get_is_challenge (result);
> ++  is_authorized = polkit_authorization_result_get_is_authorized (result);
> + 
> +   g_object_unref (result);
> + 
> +-- 
> +2.24.1
> +
> diff --git a/package/gvfs/gvfs.mk b/package/gvfs/gvfs.mk
> index c380a710fb..6c927fa345 100644
> --- a/package/gvfs/gvfs.mk
> +++ b/package/gvfs/gvfs.mk
> @@ -15,6 +15,9 @@ GVFS_LICENSE = LGPL-2.0+
>  GVFS_LICENSE_FILES = COPYING
>  GVFS_LIBS = $(TARGET_NLS_LIBS)
>  
> +# 0001-admin-Prevent-access-if-any-authentication-agent-isn-t-available.patch
> +GVFS_IGNORE_CVES += CVE-2019-3827
> +
>  # Export ac_cv_path_LIBGCRYPT_CONFIG unconditionally to prevent
>  # build system from searching the host paths.
>  GVFS_CONF_ENV = \
> -- 
> 2.25.1
> 
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