glibc/grp/compat-initgroups.c

/* Prototype for the setgrent functions we use here.  */
typedef enum nss_status (*set_function) (void);

/* Prototype for the endgrent functions we use here.  */
typedef enum nss_status (*end_function) (void);

/* Prototype for the setgrent functions we use here.  */
typedef enum nss_status (*get_function) (struct group *, char *,
					 size_t, int *);

static enum nss_status
compat_call (service_user *nip, const char *user, gid_t group, long int *start,
	     long int *size, gid_t **groupsp, long int limit, int *errnop)
{
  struct group grpbuf;
  size_t buflen = __sysconf (_SC_GETGR_R_SIZE_MAX);
  char *tmpbuf;
  enum nss_status status;
  set_function setgrent_fct;
  get_function getgrent_fct;
  end_function endgrent_fct;
  gid_t *groups = *groupsp;

  getgrent_fct = __nss_lookup_function (nip, "getgrent_r");
  if (getgrent_fct == NULL)
    return NSS_STATUS_UNAVAIL;

  setgrent_fct = __nss_lookup_function (nip, "setgrent");
  if (setgrent_fct)
    {
      status = DL_CALL_FCT (setgrent_fct, ());
      if (status != NSS_STATUS_SUCCESS)
	return status;
    }

  endgrent_fct = __nss_lookup_function (nip, "endgrent");

  tmpbuf = __alloca (buflen);

  do
    {
      while ((status = DL_CALL_FCT (getgrent_fct,
				     (&grpbuf, tmpbuf, buflen, errnop)),
	      status == NSS_STATUS_TRYAGAIN)
	     && *errnop == ERANGE)
        {
          buflen *= 2;
          tmpbuf = __alloca (buflen);
        }

      if (status != NSS_STATUS_SUCCESS)
        goto done;

      if (grpbuf.gr_gid != group)
        {
          char **m;

          for (m = grpbuf.gr_mem; *m != NULL; ++m)
            if (strcmp (*m, user) == 0)
              {
                /* Matches user.  Insert this group.  */
                if (__builtin_expect (*start == *size, 0))
                  {
                    /* Need a bigger buffer.  */
		    gid_t *newgroups;
		    long int newsize;

		    if (limit > 0 && *size == limit)
		      /* We reached the maximum.  */
		      goto done;

		    if (limit <= 0)
		      newsize = 2 * *size;
		    else
		      newsize = MIN (limit, 2 * *size);

                    newgroups = realloc (groups, newsize * sizeof (*groups));
                    if (newgroups == NULL)
                      goto done;
		    *groupsp = groups = newgroups;
                    *size = newsize;
                  }

                groups[*start] = grpbuf.gr_gid;
                *start += 1;

                break;
              }
        }
    }
  while (status == NSS_STATUS_SUCCESS);

 done:
  if (endgrent_fct)
    DL_CALL_FCT (endgrent_fct, ());

  return NSS_STATUS_SUCCESS;
}