add alternate backend support for getgrouplist

This completes the alternate backend support that was previously added
to the getpw* and getgr* functions. Unlike those, though, it
unconditionally queries nscd. Any groups from nscd that aren't in the
/etc/groups file are added to the returned list, and any that are
present in the file are ignored. The purpose of this behavior is to
provide a view of the group database consistent with what is observed
by the getgr* functions. If group memberships reported by nscd were
honored when the corresponding group already has a definition in the
/etc/groups file, the user's getgrouplist-based membership in the
group would conflict with their non-membership in the reported
gr_mem[] for the group.

The changes made also make getgrouplist thread-safe and eliminate its
clobbering of the global getgrent state.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/passwd/nscd.h b/src/passwd/nscd.h
index 102f0b4b..9a53c328 100644
--- a/src/passwd/nscd.h
+++ b/src/passwd/nscd.h
@@ -8,6 +8,7 @@
 #define GETPWBYUID 1
 #define GETGRBYNAME 2
 #define GETGRBYGID 3
+#define GETINITGR 15
 
 #define REQVERSION 0
 #define REQTYPE 1
@@ -33,6 +34,11 @@
 #define GRMEMCNT 5
 #define GR_LEN 6
 
+#define INITGRVERSION 0
+#define INITGRFOUND 1
+#define INITGRNGRPS 2
+#define INITGR_LEN 3
+
 FILE *__nscd_query(int32_t req, const char *key, int32_t *buf, size_t len, int *swap);
 
 #endif