Fix crash in DNSSEC code when attempting to verify large RRs.

CHANGELOG

@@ -19,6 +19,9 @@ version 2.73
 	    the answers given by --interface-name. Note that reverse queries
 	    (ie looking for names, given addresses) are not affected. 
 	    Thanks to Michael Gorbach for the suggestion.
+
+	    Fix crash in DNSSEC code with long RRs. Thanks to Marco Davids
+	    for the bug report.
 	
 
 version 2.72

src/dnssec.c

@@ -456,16 +456,27 @@ static u16 *get_desc(int type)
 
 /* Return bytes of canonicalised rdata, when the return value is zero, the remaining 
    data, pointed to by *p, should be used raw. */
-static int get_rdata(struct dns_header *header, size_t plen, unsigned char *end, char *buff, 
+static int get_rdata(struct dns_header *header, size_t plen, unsigned char *end, char *buff, int bufflen,
 		     unsigned char **p, u16 **desc)
 {
   int d = **desc;
   
-  (*desc)++;
-  
   /* No more data needs mangling */
   if (d == (u16)-1)
-    return 0;
+    {
+      /* If there's more data than we have space for, just return what fits,
+	 we'll get called again for more chunks */
+      if (end - *p > bufflen)
+	{
+	  memcpy(buff, *p, bufflen);
+	  *p += bufflen;
+	  return bufflen;
+	}
+      
+      return 0;
+    }
+ 
+  (*desc)++;
   
   if (d == 0 && extract_name(header, plen, p, buff, 1, 0))
     /* domain-name, canonicalise */
@@ -560,7 +571,7 @@ static void sort_rrset(struct dns_header *header, size_t plen, u16 *rr_desc, int
 	      if (left1 != 0)
 		memmove(buff1, buff1 + len1 - left1, left1);
 	      
-	      if ((len1 = get_rdata(header, plen, end1, buff1 + left1, &p1, &dp1)) == 0)
+	      if ((len1 = get_rdata(header, plen, end1, buff1 + left1, MAXDNAME - left1, &p1, &dp1)) == 0)
 		{
 		  quit = 1;
 		  len1 = end1 - p1;
@@ -571,7 +582,7 @@ static void sort_rrset(struct dns_header *header, size_t plen, u16 *rr_desc, int
 	      if (left2 != 0)
 		memmove(buff2, buff2 + len2 - left2, left2);
 	      
-	      if ((len2 = get_rdata(header, plen, end2, buff2 + left2, &p2, &dp2)) == 0)
+	      if ((len2 = get_rdata(header, plen, end2, buff2 + left2, MAXDNAME - left2, &p2, &dp2)) == 0)
 		{
 		  quit = 1;
 		  len2 = end2 - p2;
@@ -808,7 +819,7 @@ static int validate_rrset(time_t now, struct dns_header *header, size_t plen, in
 	  /* canonicalise rdata and calculate length of same, use name buffer as workspace */
 	  cp = p;
 	  dp = rr_desc;
-	  for (len = 0; (seg = get_rdata(header, plen, end, name, &cp, &dp)) != 0; len += seg);
+	  for (len = 0; (seg = get_rdata(header, plen, end, name, MAXDNAME, &cp, &dp)) != 0; len += seg);
 	  len += end - cp;
 	  len = htons(len);
 	  hash->update(ctx, 2, (unsigned char *)&len); 
@@ -816,7 +827,7 @@ static int validate_rrset(time_t now, struct dns_header *header, size_t plen, in
 	  /* Now canonicalise again and digest. */
 	  cp = p;
 	  dp = rr_desc;
-	  while ((seg = get_rdata(header, plen, end, name, &cp, &dp)))
+	  while ((seg = get_rdata(header, plen, end, name, MAXDNAME, &cp, &dp)))
 	    hash->update(ctx, seg, (unsigned char *)name);
 	  if (cp != end)
 	    hash->update(ctx, end - cp, cp);