2019-05-10 11:52:10

by Lukasz Pawelczyk

Subject: [PATCH v3] netfilter: xt_owner: Add supplementary groups option

The XT_OWNER_SUPPL_GROUPS flag causes GIDs specified with XT_OWNER_GID
to be also checked in the supplementary groups of a process.

f_cred->group_info cannot be modified during its lifetime and f_cred
holds a reference to it so it's safe to use.

Signed-off-by: Lukasz Pawelczyk <[email protected]>
---

Changes from v2:
- XT_SUPPL_GROUPS -> XT_OWNER_SUPPL_GROUPS
- clarified group_info usage in the commit log

Changes from v1:
- complementary -> supplementary

include/uapi/linux/netfilter/xt_owner.h | 7 ++++---
net/netfilter/xt_owner.c | 23 ++++++++++++++++++++---
2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/netfilter/xt_owner.h b/include/uapi/linux/netfilter/xt_owner.h
index fa3ad84957d5..9e98c09eda32 100644
--- a/include/uapi/linux/netfilter/xt_owner.h
+++ b/include/uapi/linux/netfilter/xt_owner.h
@@ -5,9 +5,10 @@
#include <linux/types.h>

enum {
- XT_OWNER_UID = 1 << 0,
- XT_OWNER_GID = 1 << 1,
- XT_OWNER_SOCKET = 1 << 2,
+ XT_OWNER_UID = 1 << 0,
+ XT_OWNER_GID = 1 << 1,
+ XT_OWNER_SOCKET = 1 << 2,
+ XT_OWNER_SUPPL_GROUPS = 1 << 3,
};

struct xt_owner_match_info {
diff --git a/net/netfilter/xt_owner.c b/net/netfilter/xt_owner.c
index 46686fb73784..a8784502aca6 100644
--- a/net/netfilter/xt_owner.c
+++ b/net/netfilter/xt_owner.c
@@ -91,11 +91,28 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
}

if (info->match & XT_OWNER_GID) {
+ unsigned int i, match = false;
kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
- if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
- gid_lte(filp->f_cred->fsgid, gid_max)) ^
- !(info->invert & XT_OWNER_GID))
+ struct group_info *gi = filp->f_cred->group_info;
+
+ if (gid_gte(filp->f_cred->fsgid, gid_min) &&
+ gid_lte(filp->f_cred->fsgid, gid_max))
+ match = true;
+
+ if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) {
+ for (i = 0; i < gi->ngroups; ++i) {
+ kgid_t group = gi->gid[i];
+
+ if (gid_gte(group, gid_min) &&
+ gid_lte(group, gid_max)) {
+ match = true;
+ break;
+ }
+ }
+ }
+
+ if (match ^ !(info->invert & XT_OWNER_GID))
return false;
}

--
2.20.1

2019-05-31 15:56:57

by Pablo Neira Ayuso

Subject: Re: [PATCH v3] netfilter: xt_owner: Add supplementary groups option

On Fri, May 10, 2019 at 01:46:22PM +0200, Lukasz Pawelczyk wrote:
> The XT_OWNER_SUPPL_GROUPS flag causes GIDs specified with XT_OWNER_GID
> to be also checked in the supplementary groups of a process.
>
> f_cred->group_info cannot be modified during its lifetime and f_cred
> holds a reference to it so it's safe to use.

Applied, thanks.