CVE-2015-7547 patch for lucid eglibc_2.11.1-0ubuntu7.21

eglibc-2.11.1-0ubuntu7.22_CVE-2015-7547.patch

Index: eglibc-2.11.1/resolv/nss_dns/dns-host.c
===================================================================
--- eglibc-2.11.1.orig/resolv/nss_dns/dns-host.c	2016-02-22 19:37:03.041133126 +0100
+++ eglibc-2.11.1/resolv/nss_dns/dns-host.c	2016-02-22 19:44:47.501119581 +0100
@@ -1025,7 +1025,10 @@
   int h_namelen = 0;
 
   if (ancount == 0)
-    return NSS_STATUS_NOTFOUND;
+    {
+      *h_errnop = HOST_NOT_FOUND;
+      return NSS_STATUS_NOTFOUND;
+    }
 
   while (ancount-- > 0 && cp < end_of_message && had_error == 0)
     {
@@ -1206,7 +1209,14 @@
   /* Special case here: if the resolver sent a result but it only
      contains a CNAME while we are looking for a T_A or T_AAAA record,
      we fail with NOTFOUND instead of TRYAGAIN.  */
-  return canon == NULL ? NSS_STATUS_TRYAGAIN : NSS_STATUS_NOTFOUND;
+  if (canon != NULL)
+    {
+      *h_errnop = HOST_NOT_FOUND;
+      return NSS_STATUS_NOTFOUND;
+    }
+
+  *h_errnop = NETDB_INTERNAL;
+  return NSS_STATUS_TRYAGAIN;
 }
 
 
@@ -1220,11 +1230,103 @@
 
   enum nss_status status = NSS_STATUS_NOTFOUND;
 
+  /* Combining the NSS status of two distinct queries requires some
+     compromise and attention to symmetry (A or AAAA queries can be
+     returned in any order).  What follows is a breakdown of how this
+     code is expected to work and why. We discuss only SUCCESS,
+     TRYAGAIN, NOTFOUND and UNAVAIL, since they are the only returns
+     that apply (though RETURN and MERGE exist).  We make a distinction
+     between TRYAGAIN (recoverable) and TRYAGAIN' (not-recoverable).
+     A recoverable TRYAGAIN is almost always due to buffer size issues
+     and returns ERANGE in errno and the caller is expected to retry
+     with a larger buffer.
+
+     Lastly, you may be tempted to make significant changes to the
+     conditions in this code to bring about symmetry between responses.
+     Please don't change anything without due consideration for
+     expected application behaviour.  Some of the synthesized responses
+     aren't very well thought out and sometimes appear to imply that
+     IPv4 responses are always answer 1, and IPv6 responses are always
+     answer 2, but that's not true (see the implemetnation of send_dg
+     and send_vc to see response can arrive in any order, particlarly
+     for UDP). However, we expect it holds roughly enough of the time
+     that this code works, but certainly needs to be fixed to make this
+     a more robust implementation.
+
+     ----------------------------------------------
+     | Answer 1 Status /   | Synthesized | Reason |
+     | Answer 2 Status     | Status      |        |
+     |--------------------------------------------|
+     | SUCCESS/SUCCESS     | SUCCESS     | [1]    |
+     | SUCCESS/TRYAGAIN    | TRYAGAIN    | [5]    |
+     | SUCCESS/TRYAGAIN'   | SUCCESS     | [1]    |
+     | SUCCESS/NOTFOUND    | SUCCESS     | [1]    |
+     | SUCCESS/UNAVAIL     | SUCCESS     | [1]    |
+     | TRYAGAIN/SUCCESS    | TRYAGAIN    | [2]    |
+     | TRYAGAIN/TRYAGAIN   | TRYAGAIN    | [2]    |
+     | TRYAGAIN/TRYAGAIN'  | TRYAGAIN    | [2]    |
+     | TRYAGAIN/NOTFOUND   | TRYAGAIN    | [2]    |
+     | TRYAGAIN/UNAVAIL    | TRYAGAIN    | [2]    |
+     | TRYAGAIN'/SUCCESS   | SUCCESS     | [3]    |
+     | TRYAGAIN'/TRYAGAIN  | TRYAGAIN    | [3]    |
+     | TRYAGAIN'/TRYAGAIN' | TRYAGAIN'   | [3]    |
+     | TRYAGAIN'/NOTFOUND  | TRYAGAIN'   | [3]    |
+     | TRYAGAIN'/UNAVAIL   | UNAVAIL     | [3]    |
+     | NOTFOUND/SUCCESS    | SUCCESS     | [3]    |
+     | NOTFOUND/TRYAGAIN   | TRYAGAIN    | [3]    |
+     | NOTFOUND/TRYAGAIN'  | TRYAGAIN'   | [3]    |
+     | NOTFOUND/NOTFOUND   | NOTFOUND    | [3]    |
+     | NOTFOUND/UNAVAIL    | UNAVAIL     | [3]    |
+     | UNAVAIL/SUCCESS     | UNAVAIL     | [4]    |
+     | UNAVAIL/TRYAGAIN    | UNAVAIL     | [4]    |
+     | UNAVAIL/TRYAGAIN'   | UNAVAIL     | [4]    |
+     | UNAVAIL/NOTFOUND    | UNAVAIL     | [4]    |
+     | UNAVAIL/UNAVAIL     | UNAVAIL     | [4]    |
+     ----------------------------------------------
+
+     [1] If the first response is a success we return success.
+         This ignores the state of the second answer and in fact
+         incorrectly sets errno and h_errno to that of the second
+	 answer.  However because the response is a success we ignore
+	 *errnop and *h_errnop (though that means you touched errno on
+         success).  We are being conservative here and returning the
+         likely IPv4 response in the first answer as a success.
+
+     [2] If the first response is a recoverable TRYAGAIN we return
+	 that instead of looking at the second response.  The
+	 expectation here is that we have failed to get an IPv4 response
+	 and should retry both queries.
+
+     [3] If the first response was not a SUCCESS and the second
+	 response is not NOTFOUND (had a SUCCESS, need to TRYAGAIN,
+	 or failed entirely e.g. TRYAGAIN' and UNAVAIL) then use the
+	 result from the second response, otherwise the first responses
+	 status is used.  Again we have some odd side-effects when the
+	 second response is NOTFOUND because we overwrite *errnop and
+	 *h_errnop that means that a first answer of NOTFOUND might see
+	 its *errnop and *h_errnop values altered.  Whether it matters
+	 in practice that a first response NOTFOUND has the wrong
+	 *errnop and *h_errnop is undecided.
+
+     [4] If the first response is UNAVAIL we return that instead of
+	 looking at the second response.  The expectation here is that
+	 it will have failed similarly e.g. configuration failure.
+
+     [5] Testing this code is complicated by the fact that truncated
+	 second response buffers might be returned as SUCCESS if the
+	 first answer is a SUCCESS.  To fix this we add symmetry to
+	 TRYAGAIN with the second response.  If the second response
+	 is a recoverable error we now return TRYAGIN even if the first
+	 response was SUCCESS.  */
+
   if (anslen1 > 0)
     status = gaih_getanswer_slice(answer1, anslen1, qname,
 				  &pat, &buffer, &buflen,
 				  errnop, h_errnop, ttlp,
 				  &first);
+
+      /* Use the second response status in some cases.  */
+
   if ((status == NSS_STATUS_SUCCESS || status == NSS_STATUS_NOTFOUND
        || (status == NSS_STATUS_TRYAGAIN
 	   && (errno != ERANGE || *h_errnop != NO_RECOVERY)))
@@ -1236,6 +1338,12 @@
 						     &first);
       if (status != NSS_STATUS_SUCCESS && status2 != NSS_STATUS_NOTFOUND)
 	status = status2;
+      /* Do not return a truncated second response (unless it was
+         unavoidable e.g. unrecoverable TRYAGAIN).  */
+      if (status == NSS_STATUS_SUCCESS
+	  && (status2 == NSS_STATUS_TRYAGAIN
+	      && *errnop == ERANGE && *h_errnop != NO_RECOVERY))
+	status = NSS_STATUS_TRYAGAIN;
     }
 
   return status;
Index: eglibc-2.11.1/resolv/res_query.c
===================================================================
--- eglibc-2.11.1.orig/resolv/res_query.c	2016-02-22 19:45:09.601826296 +0100
+++ eglibc-2.11.1/resolv/res_query.c	2016-02-22 19:57:25.111127023 +0100
@@ -390,6 +390,7 @@
 		  {
 		    free (*answerp2);
 		    *answerp2 = NULL;
+		    *nanswerp2 = 0;
 		  }
 	}
 
@@ -429,6 +430,7 @@
 			  {
 			    free (*answerp2);
 			    *answerp2 = NULL;
+                            *nanswerp2 = 0;
 			  }
 
 			/*
@@ -500,6 +502,7 @@
 	  {
 	    free (*answerp2);
 	    *answerp2 = NULL;
+	    *nanswerp2 = 0;
 	  }
 	if (saved_herrno != -1)
 		RES_SET_H_ERRNO(statp, saved_herrno);
Index: eglibc-2.11.1/resolv/res_send.c
===================================================================
--- eglibc-2.11.1.orig/resolv/res_send.c	2016-02-22 19:57:36.431096292 +0100
+++ eglibc-2.11.1/resolv/res_send.c	2016-02-22 20:18:13.281115935 +0100
@@ -364,6 +364,8 @@
 #ifdef USE_HOOKS
 	if (__builtin_expect (statp->qhook || statp->rhook, 0)) {
 		if (anssiz < MAXPACKET && ansp) {
+			/* Always allocate MAXPACKET, callers expect
+			   this specific size.  */
 			u_char *buf = malloc (MAXPACKET);
 			if (buf == NULL)
 				return (-1);
@@ -661,11 +663,7 @@
 {
 	const HEADER *hp = (HEADER *) buf;
 	const HEADER *hp2 = (HEADER *) buf2;
-	u_char *ans = *ansp;
-	int orig_anssizp = *anssizp;
-	// XXX REMOVE
-	// int anssiz = *anssizp;
-	HEADER *anhp = (HEADER *) ans;
+	HEADER *anhp = (HEADER *) *ansp;
 	struct sockaddr_in6 *nsap = EXT(statp).nsaddrs[ns];
 	int truncating, connreset, resplen, n;
 	struct iovec iov[4];
@@ -741,6 +739,8 @@
 	 * Receive length & response
 	 */
 	int recvresp1 = 0;
+	/* Skip the second response if there is no second query.
+           To do that we mark the second response as received.  */
 	int recvresp2 = buf2 == NULL;
 	uint16_t rlen16;
  read_len:
@@ -777,33 +777,14 @@
 	u_char **thisansp;
 	int *thisresplenp;
 	if ((recvresp1 | recvresp2) == 0 || buf2 == NULL) {
+		/* We have not received any responses
+		   yet or we only have one response to
+		   receive.  */
 		thisanssizp = anssizp;
 		thisansp = anscp ?: ansp;
 		assert (anscp != NULL || ansp2 == NULL);
 		thisresplenp = &resplen;
 	} else {
-		if (*anssizp != MAXPACKET) {
-			/* No buffer allocated for the first
-			   reply.  We can try to use the rest
-			   of the user-provided buffer.  */
-#ifdef _STRING_ARCH_unaligned
-			*anssizp2 = orig_anssizp - resplen;
-			*ansp2 = *ansp + resplen;
-#else
-			int aligned_resplen
-			  = ((resplen + __alignof__ (HEADER) - 1)
-			     & ~(__alignof__ (HEADER) - 1));
-			*anssizp2 = orig_anssizp - aligned_resplen;
-			*ansp2 = *ansp + aligned_resplen;
-#endif
-		} else {
-			/* The first reply did not fit into the
-			   user-provided buffer.  Maybe the second
-			   answer will.  */
-			*anssizp2 = orig_anssizp;
-			*ansp2 = *ansp;
-		}
-
 		thisanssizp = anssizp2;
 		thisansp = ansp2;
 		thisresplenp = resplen2;
@@ -811,10 +792,14 @@
 	anhp = (HEADER *) *thisansp;
 
 	*thisresplenp = rlen;
-	if (rlen > *thisanssizp) {
-		/* Yes, we test ANSCP here.  If we have two buffers
-		   both will be allocatable.  */
-		if (__builtin_expect (anscp != NULL, 1)) {
+	/* Is the answer buffer too small?  */
+	if (*thisanssizp < rlen) {
+		/* If the current buffer is not the the static
+		   user-supplied buffer then we can reallocate
+		   it.  */
+		if (thisansp != NULL && thisansp != ansp) {
+			/* Always allocate MAXPACKET, callers expect
+			   this specific size.  */
 			u_char *newp = malloc (MAXPACKET);
 			if (newp == NULL) {
 				*terrno = ENOMEM;
@@ -824,6 +809,9 @@
 			*thisanssizp = MAXPACKET;
 			*thisansp = newp;
 			anhp = (HEADER *) newp;
+			/* A uint16_t can't be larger than MAXPACKET
+			   thus it's safe to allocate MAXPACKET but
+			   read RLEN bytes instead.  */
 			len = rlen;
 		} else {
 			Dprint(statp->options & RES_DEBUG,
@@ -999,8 +987,6 @@
 {
 	const HEADER *hp = (HEADER *) buf;
 	const HEADER *hp2 = (HEADER *) buf2;
-	u_char *ans = *ansp;
-	int orig_anssizp = *anssizp;
 	struct timespec now, timeout, finish;
 	struct pollfd pfd[1];
 	int ptimeout;
@@ -1032,6 +1018,8 @@
 	int need_recompute = 0;
 	int nwritten = 0;
 	int recvresp1 = 0;
+	/* Skip the second response if there is no second query.
+           To do that we mark the second response as received.  */
 	int recvresp2 = buf2 == NULL;
 	pfd[0].fd = EXT(statp).nssocks[ns];
 	pfd[0].events = POLLOUT;
@@ -1128,50 +1116,51 @@
 		int *thisresplenp;
 
 		if ((recvresp1 | recvresp2) == 0 || buf2 == NULL) {
+			/* We have not received any responses
+			   yet or we only have one response to
+			   receive.  */
 			thisanssizp = anssizp;
 			thisansp = anscp ?: ansp;
 			assert (anscp != NULL || ansp2 == NULL);
 			thisresplenp = &resplen;
 		} else {
-			if (*anssizp != MAXPACKET) {
-				/* No buffer allocated for the first
-				   reply.  We can try to use the rest
-				   of the user-provided buffer.  */
-#ifdef _STRING_ARCH_unaligned
-				*anssizp2 = orig_anssizp - resplen;
-				*ansp2 = *ansp + resplen;
-#else
-				int aligned_resplen
-				  = ((resplen + __alignof__ (HEADER) - 1)
-				     & ~(__alignof__ (HEADER) - 1));
-				*anssizp2 = orig_anssizp - aligned_resplen;
-				*ansp2 = *ansp + aligned_resplen;
-#endif
-			} else {
-				/* The first reply did not fit into the
-				   user-provided buffer.  Maybe the second
-				   answer will.  */
-				*anssizp2 = orig_anssizp;
-				*ansp2 = *ansp;
-			}
-
 			thisanssizp = anssizp2;
 			thisansp = ansp2;
 			thisresplenp = resplen2;
 		}
 
 		if (*thisanssizp < MAXPACKET
-		    /* Yes, we test ANSCP here.  If we have two buffers
-		       both will be allocatable.  */
-		    && anscp
+		    /* If the current buffer is not the the static
+		       user-supplied buffer then we can reallocate
+		       it.  */
+		    && (thisansp != NULL && thisansp != ansp)
+		    /* Is the size too small?  */
 		    && (ioctl (pfd[0].fd, FIONREAD, thisresplenp) < 0
 			|| *thisanssizp < *thisresplenp)) {
+			/* Always allocate MAXPACKET, callers expect
+			   this specific size.  */
 			u_char *newp = malloc (MAXPACKET);
 			if (newp != NULL) {
-				*anssizp = MAXPACKET;
-				*thisansp = ans = newp;
+				*thisanssizp = MAXPACKET;
+				*thisansp = newp;
 			}
 		}
+		/* We could end up with truncation if anscp was NULL
+		   (not allowed to change caller's buffer) and the
+		   response buffer size is too small.  This isn't a
+		   reliable way to detect truncation because the ioctl
+		   may be an inaccurate report of the UDP message size.
+		   Therefore we use this only to issue debug output.
+		   To do truncation accurately with UDP we need
+		   MSG_TRUNC which is only available on Linux.  We
+		   can abstract out the Linux-specific feature in the
+		   future to detect truncation.  */
+		if (__glibc_unlikely (*thisanssizp < *thisresplenp)) {
+			Dprint(statp->options & RES_DEBUG,
+			       (stdout, ";; response may be truncated (UDP)\n")
+			);
+		}
+
 		HEADER *anhp = (HEADER *) *thisansp;
 		socklen_t fromlen = sizeof(struct sockaddr_in6);
 		assert (sizeof(from) <= fromlen);