Add ares helpers into sssd

This patch adds ares parsing functions that are not yet upstreamed
together with a private ares header file (ares_dns.h) that contains
some necessary macros for parsing common structures in the replies.

Users of these two parsing functions must also include the header files
ares_parse_{srv,txt}_reply.h that contain the function and structures
declarations that should eventually end up in upstream ares.h

1 files changed, 157 insertions, 0 deletions

diff --git a/server/resolv/ares/ares_parse_txt_reply.c b/server/resolv/ares/ares_parse_txt_reply.c
new file mode 100644
index 00000000..feb6af23
--- /dev/null
+++ b/server/resolv/ares/ares_parse_txt_reply.c
@@ -0,0 +1,157 @@
+/*
+   SSSD
+
+   Async resolver - TXT records parsing
+
+   Authors:
+        Jakub Hrozek <jhrozek@redhat.com>
+
+   Copyright (C) Red Hat, Inc 2009
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/*
+ * This code is based on other c-ares parsing licensed as follows:
+
+ * Copyright 1998 by the Massachusetts Institute of Technology.
+ *
+ * Permission to use, copy, modify, and distribute this
+ * software and its documentation for any purpose and without
+ * fee is hereby granted, provided that the above copyright
+ * notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting
+ * documentation, and that the name of M.I.T. not be used in
+ * advertising or publicity pertaining to distribution of the
+ * software without specific, written prior permission.
+ * M.I.T. makes no representations about the suitability of
+ * this software for any purpose.  It is provided "as is"
+ * without express or implied warranty.
+ */
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <arpa/nameser.h>
+#include <stdlib.h>
+#include <string.h>
+#include "ares.h"
+/* this drags in some private macros c-ares uses */
+#include "ares_dns.h"
+
+#include "ares_parse_txt_reply.h"
+
+int _ares_parse_txt_reply(const unsigned char* abuf, int alen,
+                          struct txt_reply **txt_out, int *ntxtreply)
+{
+  unsigned int qdcount, ancount;
+  const unsigned char *aptr;
+  int status, i, rr_type, rr_class, rr_len;
+  long len;
+  char *hostname = NULL, *rr_name = NULL;
+  struct txt_reply *txt = NULL;
+
+  if (txt_out)
+      *txt_out = NULL;
+
+  /* Give up if abuf doesn't have room for a header. */
+  if (alen < HFIXEDSZ)
+    return ARES_EBADRESP;
+
+  /* Fetch the question and answer count from the header. */
+  qdcount = DNS_HEADER_QDCOUNT(abuf);
+  ancount = DNS_HEADER_ANCOUNT(abuf);
+  if (qdcount != 1)
+    return ARES_EBADRESP;
+  if (ancount == 0)
+    return ARES_ENODATA;
+
+  /* Expand the name from the question, and skip past the question. */
+  aptr = abuf + HFIXEDSZ;
+  status = ares_expand_name(aptr, abuf, alen, &hostname, &len);
+  if (status != ARES_SUCCESS)
+    return status;
+
+  if (aptr + len + QFIXEDSZ > abuf + alen)
+    {
+      free (hostname);
+      return ARES_EBADRESP;
+    }
+  aptr += len + QFIXEDSZ;
+
+  /* Allocate txt_reply array; ancount gives an upper bound */
+  txt = malloc ((ancount) * sizeof (struct txt_reply));
+  if (!txt)
+    {
+      free (hostname);
+      return ARES_ENOMEM;
+    }
+
+  /* Examine each answer resource record (RR) in turn. */
+  for (i = 0; i < (int) ancount; i++)
+    {
+      /* Decode the RR up to the data field. */
+      status = ares_expand_name(aptr, abuf, alen, &rr_name, &len);
+      if (status != ARES_SUCCESS)
+	{
+	  break;
+	}
+      aptr += len;
+      if (aptr + RRFIXEDSZ > abuf + alen)
+	{
+	  status = ARES_EBADRESP;
+	  break;
+	}
+      rr_type = DNS_RR_TYPE(aptr);
+      rr_class = DNS_RR_CLASS(aptr);
+      rr_len = DNS_RR_LEN(aptr);
+      aptr += RRFIXEDSZ;
+
+      /* Check if we are really looking at a TXT record */
+      if (rr_class == C_IN && rr_type == T_TXT)
+	{
+            /* Grab the TXT payload */
+            txt[i].length = rr_len;
+            txt[i].txt = malloc(sizeof(unsigned char) * rr_len);
+            if (txt[i].txt == NULL)
+            {
+                status = ARES_ENOMEM;
+                break;
+            }
+            memcpy((void *) txt[i].txt, aptr+1, sizeof(unsigned char) * rr_len);
+            /* Move on to the next record */
+            aptr += rr_len;
+        }
+
+      /* Don't lose memory in the next iteration */
+      free(rr_name);
+      rr_name = NULL;
+    }
+
+  free(hostname);
+  free(rr_name);
+
+  /* clean up on error */
+  if (status != ARES_SUCCESS)
+    {
+      free (txt);
+      return status;
+    }
+
+  /* everything looks fine, return the data */
+  *txt_out = txt;
+  *ntxtreply = ancount;
+  return 0;
+}