[PATCH] extensions: libxt_owner: Add complementary groups option

[Lukasz Pawelczyk <l.pawelczyk@xxxxxxxxxxx>]

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

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

diff --git a/extensions/libxt_owner.c b/extensions/libxt_owner.c
index 87e4df31..950d837c 100644
--- a/extensions/libxt_owner.c
+++ b/extensions/libxt_owner.c
@@ -56,6 +56,7 @@ enum {
 	O_PROCESS,
 	O_SESSION,
 	O_COMM,
+	O_COMPL_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"
+"    --compl-groups                   Also match complementary 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 = "compl-groups", .id = O_COMPL_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_COMPL_GROUPS:
+		if (!(info->match & XT_OWNER_GID))
+			xtables_param_act(XTF_BAD_VALUE, "owner", "--compl-groups", "you need to use --gid-owner first");
+		info->match |= XT_COMPL_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. compl. groups", XT_COMPL_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, "--compl-groups",   XT_COMPL_GROUPS, true);
 }
 
 static int
diff --git a/include/linux/netfilter/xt_owner.h b/include/linux/netfilter/xt_owner.h
index 20817617..80d49dfd 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_COMPL_GROUPS = 1 << 3,
 };
 
 struct xt_owner_match_info {
-- 
2.20.1