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

9 files changed, 498 insertions, 1 deletions

diff --git a/server/Makefile.am b/server/Makefile.am
index 575f5212..4ee344bb 100644
--- a/server/Makefile.am
+++ b/server/Makefile.am
@@ -151,6 +151,13 @@ SSSD_TOOLS_OBJ = \
 
 SSSD_RESOLV_OBJ = \
     resolv/async_resolv.c
+if BUILD_ARES_PARSE_SRV
+    SSSD_RESOLV_OBJ += resolv/ares/ares_parse_srv_reply.c
+endif
+if BUILD_ARES_PARSE_TXT
+    SSSD_RESOLV_OBJ += resolv/ares/ares_parse_txt_reply.c
+endif
+
 
 SSSD_LIBS = \
     $(TALLOC_LIBS) \
@@ -200,7 +207,10 @@ dist_noinst_HEADERS = \
     providers/ldap/sdap_async.h \
     tools/tools_util.h \
     krb5_plugin/sssd_krb5_locator_plugin.h \
-    resolv/async_resolv.h
+    resolv/async_resolv.h \
+    resolv/ares/ares_parse_srv_reply.h \
+    resolv/ares/ares_parse_txt_reply.h
+
 
 ####################
 # Program Binaries #
diff --git a/server/external/libcares.m4 b/server/external/libcares.m4
index 09451b3f..020a1708 100644
--- a/server/external/libcares.m4
+++ b/server/external/libcares.m4
@@ -7,3 +7,25 @@ AC_CHECK_HEADERS(ares.h,
     [AC_MSG_ERROR([c-ares header files are not installed])]
 )
 
+dnl Check if this particular version of c-ares supports parsing of SRV records
+AC_CHECK_LIB([cares],
+             [ares_parse_srv_reply],
+             [AC_DEFINE([HAVE_ARES_PARSE_SRV], 1, [Does c-ares support srv parsing?])
+             ],
+             [
+                ares_build_srv=1
+             ]
+)
+
+dnl Check if this particular version of c-ares supports parsing of TXT records
+AC_CHECK_LIB([cares],
+             [ares_parse_txt_reply],
+             [AC_DEFINE([HAVE_ARES_PARSE_TXT], 1, [Does c-ares support txt parsing?])
+             ],
+             [
+                ares_build_txt=1
+             ]
+)
+
+AM_CONDITIONAL(BUILD_ARES_PARSE_SRV, test x$ares_build_srv = x1)
+AM_CONDITIONAL(BUILD_ARES_PARSE_TXT, test x$ares_build_txt = x1)
diff --git a/server/resolv/ares/ares_dns.h b/server/resolv/ares/ares_dns.h
new file mode 100644
index 00000000..c0a9dda6
--- /dev/null
+++ b/server/resolv/ares/ares_dns.h
@@ -0,0 +1,91 @@
+/* $Id: ares_dns.h,v 1.8 2007-02-16 14:22:08 yangtse Exp $ */
+
+/* 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.
+ */
+
+#ifndef ARES__DNS_H
+#define ARES__DNS_H
+
+#define DNS__16BIT(p)                   (((p)[0] << 8) | (p)[1])
+#define DNS__32BIT(p)                   (((p)[0] << 24) | ((p)[1] << 16) | \
+                                         ((p)[2] << 8) | (p)[3])
+
+#define DNS__SET16BIT(p, v)  (((p)[0] = (unsigned char)(((v) >> 8) & 0xff)), \
+                              ((p)[1] = (unsigned char)((v) & 0xff)))
+#define DNS__SET32BIT(p, v)  (((p)[0] = (unsigned char)(((v) >> 24) & 0xff)), \
+                              ((p)[1] = (unsigned char)(((v) >> 16) & 0xff)), \
+                              ((p)[2] = (unsigned char)(((v) >> 8) & 0xff)), \
+                              ((p)[3] = (unsigned char)((v) & 0xff)))
+
+#if 0
+/* we cannot use this approach on systems where we can't access 16/32 bit
+   data on un-aligned addresses */
+#define DNS__16BIT(p)                   ntohs(*(unsigned short*)(p))
+#define DNS__32BIT(p)                   ntohl(*(unsigned long*)(p))
+#define DNS__SET16BIT(p, v)             *(unsigned short*)(p) = htons(v)
+#define DNS__SET32BIT(p, v)             *(unsigned long*)(p) = htonl(v)
+#endif
+
+/* Macros for parsing a DNS header */
+#define DNS_HEADER_QID(h)               DNS__16BIT(h)
+#define DNS_HEADER_QR(h)                (((h)[2] >> 7) & 0x1)
+#define DNS_HEADER_OPCODE(h)            (((h)[2] >> 3) & 0xf)
+#define DNS_HEADER_AA(h)                (((h)[2] >> 2) & 0x1)
+#define DNS_HEADER_TC(h)                (((h)[2] >> 1) & 0x1)
+#define DNS_HEADER_RD(h)                ((h)[2] & 0x1)
+#define DNS_HEADER_RA(h)                (((h)[3] >> 7) & 0x1)
+#define DNS_HEADER_Z(h)                 (((h)[3] >> 4) & 0x7)
+#define DNS_HEADER_RCODE(h)             ((h)[3] & 0xf)
+#define DNS_HEADER_QDCOUNT(h)           DNS__16BIT((h) + 4)
+#define DNS_HEADER_ANCOUNT(h)           DNS__16BIT((h) + 6)
+#define DNS_HEADER_NSCOUNT(h)           DNS__16BIT((h) + 8)
+#define DNS_HEADER_ARCOUNT(h)           DNS__16BIT((h) + 10)
+
+/* Macros for constructing a DNS header */
+#define DNS_HEADER_SET_QID(h, v)      DNS__SET16BIT(h, v)
+#define DNS_HEADER_SET_QR(h, v)       ((h)[2] |= (unsigned char)(((v) & 0x1) << 7))
+#define DNS_HEADER_SET_OPCODE(h, v)   ((h)[2] |= (unsigned char)(((v) & 0xf) << 3))
+#define DNS_HEADER_SET_AA(h, v)       ((h)[2] |= (unsigned char)(((v) & 0x1) << 2))
+#define DNS_HEADER_SET_TC(h, v)       ((h)[2] |= (unsigned char)(((v) & 0x1) << 1))
+#define DNS_HEADER_SET_RD(h, v)       ((h)[2] |= (unsigned char)((v) & 0x1))
+#define DNS_HEADER_SET_RA(h, v)       ((h)[3] |= (unsigned char)(((v) & 0x1) << 7))
+#define DNS_HEADER_SET_Z(h, v)        ((h)[3] |= (unsigned char)(((v) & 0x7) << 4))
+#define DNS_HEADER_SET_RCODE(h, v)    ((h)[3] |= (unsigned char)((v) & 0xf))
+#define DNS_HEADER_SET_QDCOUNT(h, v)  DNS__SET16BIT((h) + 4, v)
+#define DNS_HEADER_SET_ANCOUNT(h, v)  DNS__SET16BIT((h) + 6, v)
+#define DNS_HEADER_SET_NSCOUNT(h, v)  DNS__SET16BIT((h) + 8, v)
+#define DNS_HEADER_SET_ARCOUNT(h, v)  DNS__SET16BIT((h) + 10, v)
+
+/* Macros for parsing the fixed part of a DNS question */
+#define DNS_QUESTION_TYPE(q)            DNS__16BIT(q)
+#define DNS_QUESTION_CLASS(q)           DNS__16BIT((q) + 2)
+
+/* Macros for constructing the fixed part of a DNS question */
+#define DNS_QUESTION_SET_TYPE(q, v)     DNS__SET16BIT(q, v)
+#define DNS_QUESTION_SET_CLASS(q, v)    DNS__SET16BIT((q) + 2, v)
+
+/* Macros for parsing the fixed part of a DNS resource record */
+#define DNS_RR_TYPE(r)                  DNS__16BIT(r)
+#define DNS_RR_CLASS(r)                 DNS__16BIT((r) + 2)
+#define DNS_RR_TTL(r)                   DNS__32BIT((r) + 4)
+#define DNS_RR_LEN(r)                   DNS__16BIT((r) + 8)
+
+/* Macros for constructing the fixed part of a DNS resource record */
+#define DNS_RR_SET_TYPE(r)              DNS__SET16BIT(r, v)
+#define DNS_RR_SET_CLASS(r)             DNS__SET16BIT((r) + 2, v)
+#define DNS_RR_SET_TTL(r)               DNS__SET32BIT((r) + 4, v)
+#define DNS_RR_SET_LEN(r)               DNS__SET16BIT((r) + 8, v)
+
+#endif /* ARES__DNS_H */
diff --git a/server/resolv/ares/ares_parse_srv_reply.c b/server/resolv/ares/ares_parse_srv_reply.c
new file mode 100644
index 00000000..9745fb07
--- /dev/null
+++ b/server/resolv/ares/ares_parse_srv_reply.c
@@ -0,0 +1,173 @@
+/*
+   SSSD
+
+   Async resolver - SRV 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_srv_reply.h"
+
+int _ares_parse_srv_reply (const unsigned char *abuf, int alen,
+                           struct srv_reply **srv_out, int *nsrvreply)
+{
+  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 srv_reply *srv = NULL;
+
+  /* Set *srv_out to NULL for all failure cases. */
+  if (srv_out)
+    *srv_out = NULL;
+  /* Same with *nsrvreply. */
+  if (nsrvreply)
+    *nsrvreply = 0;
+
+  /* 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 srv_reply array; ancount gives an upper bound */
+  srv = malloc ((ancount) * sizeof (struct srv_reply));
+  if (!srv)
+    {
+      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 SRV record */
+      if (rr_class == C_IN && rr_type == T_SRV)
+        {
+          /* parse the SRV record itself */
+          if (rr_len < 6)
+            {
+              status = ARES_EBADRESP;
+              break;
+            }
+
+          srv[i].priority = ntohs (*((const uint16_t *)aptr));
+          aptr += sizeof(uint16_t);
+          srv[i].weight = ntohs (*((const uint16_t *)aptr));
+          aptr += sizeof(uint16_t);
+          srv[i].port = ntohs (*((const uint16_t *)aptr));
+          aptr += sizeof(uint16_t);
+
+          status = ares_expand_name (aptr, abuf, alen, &srv[i].host, &len);
+          if (status != ARES_SUCCESS)
+            break;
+
+          /* Move on to the next record */
+          aptr += len;
+
+          /* Don't lose memory in the next iteration */
+          free (rr_name);
+          rr_name = NULL;
+        }
+    }
+
+  /* clean up on error */
+  if (status != ARES_SUCCESS)
+    {
+      free (srv);
+      free (hostname);
+      free (rr_name);
+      return status;
+    }
+
+  /* everything looks fine, return the data */
+  *srv_out = srv;
+  *nsrvreply = ancount;
+
+  free (hostname);
+  free (rr_name);
+  return status;
+}
diff --git a/server/resolv/ares/ares_parse_srv_reply.h b/server/resolv/ares/ares_parse_srv_reply.h
new file mode 100644
index 00000000..43eb4154
--- /dev/null
+++ b/server/resolv/ares/ares_parse_srv_reply.h
@@ -0,0 +1,14 @@
+#ifndef __ARES_PARSE_SRV_REPLY_H__
+#define __ARES_PARSE_SRV_REPLY_H__
+
+struct srv_reply {
+    u_int16_t weight;
+    u_int16_t priority;
+    u_int16_t port;
+    char *host;
+};
+
+int _ares_parse_srv_reply (const unsigned char *abuf, int alen,
+                           struct srv_reply **srv_out, int *nsrvreply);
+
+#endif /* __ARES_PARSE_SRV_REPLY_H__ */
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;
+}
diff --git a/server/resolv/ares/ares_parse_txt_reply.h b/server/resolv/ares/ares_parse_txt_reply.h
new file mode 100644
index 00000000..b1e32698
--- /dev/null
+++ b/server/resolv/ares/ares_parse_txt_reply.h
@@ -0,0 +1,12 @@
+#ifndef __ARES_PARSE_TXT_REPLY_H__
+#define __ARES_PARSE_TXT_REPLY_H__
+
+struct txt_reply {
+    int length;         /* length of the text */
+    unsigned char *txt; /* may contain nulls */
+};
+
+int _ares_parse_txt_reply(const unsigned char* abuf, int alen,
+                          struct txt_reply **txt_out, int *ntxtreply);
+
+#endif /* __ARES_PARSE_TXT_REPLY_H__ */
diff --git a/server/resolv/async_resolv.c b/server/resolv/async_resolv.c
index 70bea6c8..b77819c0 100644
--- a/server/resolv/async_resolv.c
+++ b/server/resolv/async_resolv.c
@@ -42,6 +42,16 @@
 #include "util/dlinklist.h"
 #include "util/util.h"
 
+#ifndef HAVE_ARES_PARSE_SRV
+#define ares_parse_srv_reply(abuf, alen, srv_out, nsrvreply) \
+    _ares_parse_srv_reply(abuf, alen, srv_out, nsrvreply)
+#endif /* HAVE_ARES_PARSE_SRV */
+
+#ifndef HAVE_ARES_PARSE_TXT
+#define ares_parse_txt_reply(abuf, alen, txt_out, ntxtreply) \
+    _ares_parse_txt_reply(abuf, alen, txt_out, ntxtreply)
+#endif /* HAVE_ARES_PARSE_TXT */
+
 /* TODO: remove later
  * These functions are available in the latest tevent/talloc and are the ones
  * that should be used as tevent_req is rightfully opaque there */
diff --git a/server/resolv/async_resolv.h b/server/resolv/async_resolv.h
index 6acb6b2a..aabf871b 100644
--- a/server/resolv/async_resolv.h
+++ b/server/resolv/async_resolv.h
@@ -29,6 +29,14 @@
 #include <netdb.h>
 #include <ares.h>
 
+#ifndef HAVE_ARES_PARSE_TXT
+#include "resolv/ares/ares_parse_txt_reply.h"
+#endif /* HAVE_ARES_PARSE_TXT */
+
+#ifndef HAVE_ARES_PARSE_SRV
+#include "resolv/ares/ares_parse_srv_reply.h"
+#endif /* HAVE_ARES_PARSE_SRV */
+
 /*
  * An opaque structure which holds context for a module using the async
  * resolver. Is should be used as a "local-global" variable - in sssd,