[PATCH v2] extensions: libxt_owner: Add supplementary groups option

[Lukasz Pawelczyk <l.pawelczyk@xxxxxxxxxxx>]

The --suppl-groups option causes GIDs specified with --gid-owner to be
also checked in the supplementary groups of a process.

Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@xxxxxxxxxxx>
---
 extensions/libxt_owner.c           | 13 ++++++++++++-
 extensions/libxt_owner.man         |  4 ++++
 include/linux/netfilter/xt_owner.h |  1 +
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/extensions/libxt_owner.c b/extensions/libxt_owner.c
index 87e4df31..6a97e185 100644
--- a/extensions/libxt_owner.c
+++ b/extensions/libxt_owner.c
@@ -56,6 +56,7 @@ enum {
 	O_PROCESS,
 	O_SESSION,
 	O_COMM,
+	O_SUPPL_GROUPS,
 };
 
 static void owner_mt_help_v0(void)
@@ -87,7 +88,8 @@ static void owner_mt_help(void)
 "owner match options:\n"
 "[!] --uid-owner userid[-userid]      Match local UID\n"
 "[!] --gid-owner groupid[-groupid]    Match local GID\n"
-"[!] --socket-exists                  Match if socket exists\n");
+"[!] --socket-exists                  Match if socket exists\n"
+"    --suppl-groups                   Also match supplementary groups set with --gid-owner\n");
 }
 
 #define s struct ipt_owner_info
@@ -131,6 +133,8 @@ static const struct xt_option_entry owner_mt_opts[] = {
 	 .flags = XTOPT_INVERT},
 	{.name = "socket-exists", .id = O_SOCK_EXISTS, .type = XTTYPE_NONE,
 	 .flags = XTOPT_INVERT},
+	{.name = "suppl-groups", .id = O_SUPPL_GROUPS, .type = XTTYPE_NONE,
+	 .flags = XTOPT_INVERT},
 	XTOPT_TABLEEND,
 };
 
@@ -275,6 +279,11 @@ static void owner_mt_parse(struct xt_option_call *cb)
 			info->invert |= XT_OWNER_SOCKET;
 		info->match |= XT_OWNER_SOCKET;
 		break;
+	case O_SUPPL_GROUPS:
+		if (!(info->match & XT_OWNER_GID))
+			xtables_param_act(XTF_BAD_VALUE, "owner", "--suppl-groups", "you need to use --gid-owner first");
+		info->match |= XT_SUPPL_GROUPS;
+		break;
 	}
 }
 
@@ -458,6 +467,7 @@ static void owner_mt_print(const void *ip, const struct xt_entry_match *match,
 	owner_mt_print_item(info, "owner socket exists", XT_OWNER_SOCKET, numeric);
 	owner_mt_print_item(info, "owner UID match",     XT_OWNER_UID,    numeric);
 	owner_mt_print_item(info, "owner GID match",     XT_OWNER_GID,    numeric);
+	owner_mt_print_item(info, "incl. suppl. groups", XT_SUPPL_GROUPS, numeric);
 }
 
 static void
@@ -490,6 +500,7 @@ static void owner_mt_save(const void *ip, const struct xt_entry_match *match)
 	owner_mt_print_item(info, "--socket-exists",  XT_OWNER_SOCKET, true);
 	owner_mt_print_item(info, "--uid-owner",      XT_OWNER_UID,    true);
 	owner_mt_print_item(info, "--gid-owner",      XT_OWNER_GID,    true);
+	owner_mt_print_item(info, "--suppl-groups",   XT_SUPPL_GROUPS, true);
 }
 
 static int
diff --git a/extensions/libxt_owner.man b/extensions/libxt_owner.man
index 49b58cee..e2479865 100644
--- a/extensions/libxt_owner.man
+++ b/extensions/libxt_owner.man
@@ -15,5 +15,9 @@ given user. You may also specify a numerical UID, or an UID range.
 Matches if the packet socket's file structure is owned by the given group.
 You may also specify a numerical GID, or a GID range.
 .TP
+\fB\-\-suppl\-groups\fP
+Causes group(s) specified with \fB\-\-gid-owner\fP to be also checked in the
+supplementary groups of a process.
+.TP
 [\fB!\fP] \fB\-\-socket\-exists\fP
 Matches if the packet is associated with a socket.
diff --git a/include/linux/netfilter/xt_owner.h b/include/linux/netfilter/xt_owner.h
index 20817617..e5a743b6 100644
--- a/include/linux/netfilter/xt_owner.h
+++ b/include/linux/netfilter/xt_owner.h
@@ -7,6 +7,7 @@ enum {
 	XT_OWNER_UID    = 1 << 0,
 	XT_OWNER_GID    = 1 << 1,
 	XT_OWNER_SOCKET = 1 << 2,
+	XT_SUPPL_GROUPS = 1 << 3,
 };
 
 struct xt_owner_match_info {
-- 
2.20.1