rewrite gid cache system

Uses fixed storage so as to not require C++11 local thread storage or memory allocation.

src/gidcache.cpp

@@ -0,0 +1,143 @@
+/*
+  The MIT License (MIT)
+
+  Copyright (c) 2015 Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+  THE SOFTWARE.
+*/
+
+#include <stdlib.h>
+#include <sys/types.h>
+#include <pwd.h>
+#include <grp.h>
+#include <unistd.h>
+
+#include <cstdlib>
+#include <algorithm>
+
+#include "gidcache.hpp"
+
+bool
+gid_t_rec::operator<(const struct gid_t_rec &b) const
+{
+  return uid < b.uid;
+}
+
+inline
+gid_t_rec *
+gid_t_cache::begin(void)
+{
+  return recs;
+}
+
+inline
+gid_t_rec *
+gid_t_cache::end(void)
+{
+  return recs + size;
+}
+
+inline
+gid_t_rec *
+gid_t_cache::allocrec(void)
+{
+  if(size == MAXRECS)
+    return &recs[rand() % MAXRECS];
+  else
+    return &recs[size++];
+}
+
+inline
+gid_t_rec *
+gid_t_cache::lower_bound(gid_t_rec   *begin,
+                         gid_t_rec   *end,
+                         const uid_t  uid)
+{
+  int step;
+  int count;
+  gid_t_rec *iter;
+
+  count = std::distance(begin,end);
+  while(count > 0)
+    {
+      iter = begin;
+      step = count / 2;
+      std::advance(iter,step);
+      if(iter->uid < uid)
+        {
+          begin  = ++iter;
+          count -= step + 1;
+        }
+      else
+        {
+          count = step;
+        }
+    }
+
+  return begin;
+}
+
+gid_t_rec *
+gid_t_cache::cache(const uid_t uid,
+                   const gid_t gid)
+{
+  int rv;
+  char buf[4096];
+  struct passwd pwd;
+  struct passwd *pwdrv;
+  gid_t_rec *rec;
+
+  rec = allocrec();
+
+  rec->uid = uid;
+  rv = ::getpwuid_r(uid,&pwd,buf,sizeof(buf),&pwdrv);
+  if(pwdrv != NULL && rv == 0)
+    {
+      rec->size = 0;
+      rv = ::getgrouplist(pwd.pw_name,gid,NULL,&rec->size);
+      rec->size = std::min(MAXGIDS,rec->size);
+      rv = ::getgrouplist(pwd.pw_name,gid,rec->gids,&rec->size);
+      if(rv == -1)
+        {
+          rec->gids[0] = gid;
+          rec->size    = 1;
+        }
+    }
+
+  return rec;
+}
+
+void
+gid_t_cache::initgroups(const uid_t uid,
+                        const gid_t gid)
+{
+  gid_t_rec *rec;
+
+  rec = lower_bound(begin(),end(),uid);
+  if(rec == end() || rec->uid != uid)
+    {
+      rec = cache(uid,gid);
+      ::setgroups(rec->size,rec->gids);
+      std::sort(begin(),end());
+    }
+  else
+    {
+      ::setgroups(rec->size,rec->gids);
+    }
+}