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