dns: change get_dns_name to return consumed bytes + actual name len.

Because of the DNS name encoding, the consumed bytes in the tvb and
the length of the string of the dns name can be different. We need
to handle them separately for the purpose they are. Moreover the
name string can contain null bytes, then we can't rely on strlen()
but we need the actual length.

Subsequent calls to proto_tree_add_string() will require to pass
the string to format_text() in order have non-printable characters
printed.

Bug: 13289
Change-Id: I6d0b295867ece265f8995f82da2c629992aeb703
Reviewed-on: https://code.wireshark.org/review/19539
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Petri-Dish: Dario Lombardo <lomato@gmail.com>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>

1 files changed, 14 insertions, 9 deletions

diff --git a/epan/dissectors/packet-icmpv6.c b/epan/dissectors/packet-icmpv6.c
index 9e543df268..45e85a48d0 100644
--- a/epan/dissectors/packet-icmpv6.c
+++ b/epan/dissectors/packet-icmpv6.c
@@ -46,6 +46,7 @@
 #include <epan/capture_dissectors.h>
 #include <epan/proto_data.h>
 #include <epan/ipv6.h>
+#include <epan/strutil.h>
 
 #include "packet-ber.h"
 #include "packet-dns.h"
@@ -1520,6 +1521,7 @@ dissect_icmpv6_nd_opt(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree
     int         opt_len;
     int         opt_offset;
     tvbuff_t   *opt_tvb;
+    guint       used_bytes;
 
     while ((int)tvb_reported_length(tvb) > offset) {
         /* there are more options */
@@ -2287,10 +2289,10 @@ dissect_icmpv6_nd_opt(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree
                         opt_offset += padd_length;
                         break;
                     }
-                    dnssl_len = get_dns_name(tvb, opt_offset, 0, opt_offset, &dnssl_name);
-                    proto_tree_add_string(icmp6opt_tree, hf_icmpv6_opt_dnssl, tvb, opt_offset, dnssl_len, dnssl_name);
+                    used_bytes = get_dns_name(tvb, opt_offset, 0, opt_offset, &dnssl_name, &dnssl_len);
+                    proto_tree_add_string(icmp6opt_tree, hf_icmpv6_opt_dnssl, tvb, opt_offset, used_bytes, format_text(dnssl_name, dnssl_len));
                     proto_item_append_text(ti, " %s", dnssl_name);
-                    opt_offset += dnssl_len;
+                    opt_offset += used_bytes;
 
                 }
                 break;
@@ -3390,6 +3392,7 @@ static int
 dissect_nodeinfo(tvbuff_t *tvb, int ni_offset, packet_info *pinfo _U_, proto_tree *tree, guint8 icmp6_type, guint8 icmp6_code)
 {
     guint16     qtype;
+    guint       used_bytes;
     static const int * ni_flags[] = {
         &hf_icmpv6_ni_flag_g,
         &hf_icmpv6_ni_flag_s,
@@ -3430,8 +3433,9 @@ dissect_nodeinfo(tvbuff_t *tvb, int ni_offset, packet_info *pinfo _U_, proto_tre
             case ICMP6_NI_SUBJ_FQDN: {
                 int fqdn_len;
                 const guchar *fqdn_name;
-                fqdn_len = get_dns_name(tvb, ni_offset, 0, ni_offset, &fqdn_name);
-                proto_tree_add_string(tree, hf_icmpv6_ni_query_subject_fqdn, tvb, ni_offset, fqdn_len, fqdn_name);
+                used_bytes = get_dns_name(tvb, ni_offset, 0, ni_offset, &fqdn_name, &fqdn_len);
+                proto_tree_add_string(tree, hf_icmpv6_ni_query_subject_fqdn, tvb, ni_offset, used_bytes,
+                    format_text(fqdn_name, fqdn_len));
                 ni_offset += fqdn_len;
                 break;
             }
@@ -3446,7 +3450,7 @@ dissect_nodeinfo(tvbuff_t *tvb, int ni_offset, packet_info *pinfo _U_, proto_tre
             case NI_QTYPE_NOOP:
                 break;
             case NI_QTYPE_NODENAME: {
-                int node_len;
+                int node_name_len;
                 const guchar *node_name;
                 /* TTL */
                 proto_tree_add_item(tree, hf_icmpv6_ni_reply_node_ttl, tvb, ni_offset, 4, ENC_BIG_ENDIAN);
@@ -3461,9 +3465,10 @@ dissect_nodeinfo(tvbuff_t *tvb, int ni_offset, packet_info *pinfo _U_, proto_tre
                         break;
                     }
                     /* Node Name */
-                    node_len = get_dns_name(tvb, ni_offset, 0, ni_offset, &node_name);
-                    proto_tree_add_string(tree, hf_icmpv6_ni_reply_node_name, tvb, ni_offset, node_len, node_name);
-                    ni_offset += node_len;
+                    used_bytes = get_dns_name(tvb, ni_offset, 0, ni_offset, &node_name, &node_name_len);
+                    proto_tree_add_string(tree, hf_icmpv6_ni_reply_node_name, tvb, ni_offset, used_bytes,
+                        format_text(node_name, node_name_len));
+                    ni_offset += used_bytes;
                 }
                 break;
             }