Local change to use initgroups() instead of setgid() to set
the groups for the process as we are dropping privileges.

TODO(pstew): Generalize and upstream this change.

diff --git a/strongswan-5.0.2/src/libstrongswan/utils/capabilities.c-orig b/strongswan-5.0.2/src/libstrongswan/utils/capabilities.c
index c36a76e..38a6ff6 100644
--- a/strongswan-5.0.2/src/libstrongswan/utils/capabilities.c-orig
+++ b/strongswan-5.0.2/src/libstrongswan/utils/capabilities.c
@@ -57,6 +57,12 @@ struct private_capabilities_t {
 	gid_t gid;
 
 	/**
+	 * user name as retained from pw_name field from the password
+	 * entry retrieved from getwpwnam().
+	 */
+	char *pw_name;
+
+	/**
 	 * capabilities to keep
 	 */
 #ifdef CAPABILITIES_LIBCAP
@@ -145,8 +151,9 @@ METHOD(capabilities_t, resolve_uid, bool,
 	err = errno;
 	this->mutex->unlock(this->mutex);
 #endif /* HAVE GETPWNAM_R */
-	if (pwp)
+	if (pwp && pwp->pw_name != NULL)
 	{
+		this->pw_name = strdup(pwp->pw_name);
 		return TRUE;
 	}
 	DBG1(DBG_LIB, "resolving user '%s' failed: %s", username,
@@ -195,10 +202,11 @@ METHOD(capabilities_t, drop, bool,
 	prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
 #endif
 
-	if (this->gid && setgid(this->gid) != 0)
-	{
-		DBG1(DBG_LIB, "change to unprivileged group %u failed: %s",
-			 this->gid, strerror(errno));
+	if (this->gid && this->pw_name &&
+		 initgroups(this->pw_name, this->gid) != 0) {
+		DBG1(DBG_LIB, "Init groups for unprivileged user %s group %u "
+			"failed: %s",
+			 this->pw_name, this->gid, strerror(errno));
 		return FALSE;
 	}
 	if (this->uid && setuid(this->uid) != 0)
@@ -249,6 +257,7 @@ METHOD(capabilities_t, destroy, void,
 #ifdef CAPABILITIES_LIBCAP
 	cap_free(this->caps);
 #endif /* CAPABILITIES_LIBCAP */
+	free(this->pw_name);
 	free(this);
 }
 
@@ -283,6 +292,8 @@ capabilities_t *capabilities_create()
 	}
 #endif /* CAPABILITIES */
 
+	this->pw_name = NULL;
+
 #ifdef EMULATE_R_FUNCS
 	this->mutex = mutex_create(MUTEX_TYPE_DEFAULT);
 #endif /* EMULATE_R_FUNCS */