grp/compat-initgroups.c

   1 /* Prototype for the setgrent functions we use here.  */
   2 typedef enum nss_status (*set_function) (void);
   3
   4 /* Prototype for the endgrent functions we use here.  */
   5 typedef enum nss_status (*end_function) (void);
   6
   7 /* Prototype for the setgrent functions we use here.  */
   8 typedef enum nss_status (*get_function) (struct group *, char *,
   9                                          size_t, int *);
  10
  11 /* This file is also used in nscd where __libc_alloca_cutoff is not
  12    available.  */
  13 #ifdef NOT_IN_libc
  14 # define __libc_use_alloca(size) ((size) < __MAX_ALLOCA_CUTOFF * 4)
  15 #endif
  16
  17
  18 static enum nss_status
  19 compat_call (service_user *nip, const char *user, gid_t group, long int *start,
  20              long int *size, gid_t **groupsp, long int limit, int *errnop)
  21 {
  22   struct group grpbuf;
  23   size_t buflen = __sysconf (_SC_GETGR_R_SIZE_MAX);
  24   enum nss_status status;
  25   set_function setgrent_fct;
  26   get_function getgrent_fct;
  27   end_function endgrent_fct;
  28   gid_t *groups = *groupsp;
  29
  30   getgrent_fct = __nss_lookup_function (nip, "getgrent_r");
  31   if (getgrent_fct == NULL)
  32     return NSS_STATUS_UNAVAIL;
  33
  34   setgrent_fct = __nss_lookup_function (nip, "setgrent");
  35   if (setgrent_fct)
  36     {
  37       status = DL_CALL_FCT (setgrent_fct, ());
  38       if (status != NSS_STATUS_SUCCESS)
  39         return status;
  40     }
  41
  42   endgrent_fct = __nss_lookup_function (nip, "endgrent");
  43
  44   char *tmpbuf = __alloca (buflen);
  45   bool use_malloc = false;
  46   enum nss_status result = NSS_STATUS_SUCCESS;
  47
  48   do
  49     {
  50       while ((status = DL_CALL_FCT (getgrent_fct,
  51                                      (&grpbuf, tmpbuf, buflen, errnop)),
  52               status == NSS_STATUS_TRYAGAIN)
  53              && *errnop == ERANGE)
  54         {
  55           if (__libc_use_alloca (buflen * 2))
  56             tmpbuf = extend_alloca (tmpbuf, buflen, buflen * 2);
  57           else
  58             {
  59               buflen *= 2;
  60               char *newbuf = realloc (use_malloc ? tmpbuf : NULL, buflen);
  61               if (newbuf == NULL)
  62                 {
  63                   result = NSS_STATUS_TRYAGAIN;
  64                   goto done;
  65                 }
  66               use_malloc = true;
  67               tmpbuf = newbuf;
  68             }
  69         }
  70
  71       if (status != NSS_STATUS_SUCCESS)
  72         goto done;
  73
  74       if (grpbuf.gr_gid != group)
  75         {
  76           char **m;
  77
  78           for (m = grpbuf.gr_mem; *m != NULL; ++m)
  79             if (strcmp (*m, user) == 0)
  80               {
  81                 /* Check whether the group is already on the list.  */
  82                 long int cnt;
  83                 for (cnt = 0; cnt < *start; ++cnt)
  84                   if (groups[cnt] == grpbuf.gr_gid)
  85                     break;
  86
  87                 if (cnt == *start)
  88                   {
  89                     /* Matches user and not yet on the list.  Insert
  90                        this group.  */
  91                     if (__builtin_expect (*start == *size, 0))
  92                       {
  93                         /* Need a bigger buffer.  */
  94                         gid_t *newgroups;
  95                         long int newsize;
  96
  97                         if (limit > 0 && *size == limit)
  98                           /* We reached the maximum.  */
  99                           goto done;
 100
 101                         if (limit <= 0)
 102                           newsize = 2 * *size;
 103                         else
 104                           newsize = MIN (limit, 2 * *size);
 105
 106                         newgroups = realloc (groups,
 107                                              newsize * sizeof (*groups));
 108                         if (newgroups == NULL)
 109                           goto done;
 110                         *groupsp = groups = newgroups;
 111                         *size = newsize;
 112                       }
 113
 114                     groups[*start] = grpbuf.gr_gid;
 115                     *start += 1;
 116                   }
 117
 118                 break;
 119               }
 120         }
 121     }
 122   while (status == NSS_STATUS_SUCCESS);
 123
 124  done:
 125   if (use_malloc)
 126     free (tmpbuf);
 127
 128   if (endgrent_fct)
 129     DL_CALL_FCT (endgrent_fct, ());
 130
 131   return result;
 132 }