epan/dissectors/packet-discard.c

   1 /* packet-discard.c
   2  * Routines for Discard Protocol dissection
   3  *
   4  * Discard specs taken from RFC 863
   5  * https://tools.ietf.org/html/rfc863
   6  *
   7  * Inspiration from packet-chargen.c and packet-data.
   8  *
   9  * Wireshark - Network traffic analyzer
  10  * By Gerald Combs <gerald@wireshark.org>
  11  * Copyright 1998 Gerald Combs
  12  *
  13  * SPDX-License-Identifier: GPL-2.0-or-later
  14  */
  15
  16 #include "config.h"
  17
  18 #include <epan/packet.h>
  19 #include <epan/prefs.h>
  20 #include <wsutil/wsgcrypt.h>
  21 #include <wsutil/to_str.h>
  22
  23 #define DISCARD_PORT_UDP 9
  24 #define DISCARD_PORT_TCP 9
  25
  26 void proto_register_discard(void);
  27 void proto_reg_handoff_discard(void);
  28
  29 static int proto_discard;
  30
  31 static int hf_discard_data;
  32 static int hf_discard_text;
  33 static int hf_discard_md5_hash;
  34 static int hf_discard_len;
  35
  36 static bool show_as_text;
  37 static bool generate_md5_hash;
  38
  39 static int ett_discard;
  40
  41 /* dissect_discard - dissects discard packet data
  42  * tvb - tvbuff for packet data (IN)
  43  * pinfo - packet info
  44  * proto_tree - resolved protocol tree
  45  */
  46 static int
  47 dissect_discard(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* dissector_data _U_)
  48 {
  49         proto_tree* discard_tree;
  50         proto_item* ti;
  51         uint32_t len;
  52         uint32_t cap_len;
  53
  54         col_set_str(pinfo->cinfo, COL_PROTOCOL, "DISCARD");
  55
  56         if (show_as_text) {
  57                 col_set_str(pinfo->cinfo, COL_INFO, "Discard: ");
  58         } else {
  59                 col_set_str(pinfo->cinfo, COL_INFO, "Discard");
  60         }
  61
  62         ti = proto_tree_add_item(tree, proto_discard, tvb, 0, -1, ENC_NA);
  63         discard_tree = proto_item_add_subtree(ti, ett_discard);
  64
  65         len = tvb_reported_length(tvb);
  66         cap_len = tvb_captured_length(tvb);
  67
  68         proto_tree_add_item(discard_tree, hf_discard_data, tvb, 0, -1, ENC_NA);
  69
  70         if (show_as_text) {
  71                 char *display_str;
  72
  73                 proto_tree_add_item_ret_display_string(discard_tree, hf_discard_text, tvb, 0, -1, ENC_ASCII, pinfo->pool, &display_str);
  74                 col_append_str(pinfo->cinfo, COL_INFO, display_str);
  75         }
  76
  77         if (generate_md5_hash) {
  78                 const uint8_t *cp;
  79                 uint8_t       digest[HASH_MD5_LENGTH];
  80                 const char   *digest_string;
  81
  82                 cp = tvb_get_ptr(tvb, 0, cap_len);
  83
  84                 gcry_md_hash_buffer(GCRY_MD_MD5, digest, cp, cap_len);
  85                 digest_string = bytes_to_str_punct(pinfo->pool, digest, HASH_MD5_LENGTH, '\0');
  86
  87                 ti = proto_tree_add_string(discard_tree, hf_discard_md5_hash, tvb, 0, 0, digest_string);
  88                 proto_item_set_generated(ti);
  89         }
  90
  91         ti = proto_tree_add_uint(discard_tree, hf_discard_len, tvb, 0, 0, len);
  92         proto_item_set_generated(ti);
  93
  94         if(len > cap_len) {
  95                 /*
  96                  * Trigger _ws.short, e.g. [Packet size limited during capture: DISCARD truncated]
  97                  */
  98                 tvb_get_ptr(tvb, 0, len);
  99         }
 100
 101         return cap_len;
 102 }
 103
 104 void
 105 proto_register_discard(void)
 106 {
 107         static hf_register_info hf[] = {
 108                 { &hf_discard_data, {
 109                         "Data", "discard.data",
 110                         FT_BYTES, BASE_NONE, NULL, 0,
 111                         NULL, HFILL }
 112                 },
 113                 { &hf_discard_text, {
 114                         "Text", "discard.text",
 115                         FT_STRING, BASE_NONE, NULL, 0,
 116                         NULL, HFILL }
 117                 },
 118                 { &hf_discard_md5_hash, {
 119                         "Payload MD5 hash", "discard.md5_hash",
 120                         FT_STRING, BASE_NONE, NULL, 0,
 121                         NULL, HFILL }
 122                 },
 123                 { &hf_discard_len, {
 124                         "Reported Length", "discard.len",
 125                         FT_UINT32, BASE_DEC, NULL, 0,
 126                         NULL, HFILL }
 127                 },
 128         };
 129
 130         static int *ett[] = {
 131                 &ett_discard,
 132         };
 133
 134         module_t *module_data;
 135
 136         proto_discard = proto_register_protocol("Discard Protocol", "DISCARD", "discard");
 137
 138         proto_register_field_array(proto_discard, hf, array_length(hf));
 139         proto_register_subtree_array(ett, array_length(ett));
 140
 141         module_data = prefs_register_protocol(proto_discard, NULL);
 142
 143         prefs_register_bool_preference(module_data,
 144                 "show_as_text",
 145                 "Show data as text",
 146                 "Show data as text in the Packet Details pane",
 147                 &show_as_text);
 148
 149         prefs_register_bool_preference(module_data,
 150                 "md5_hash",
 151                 "Generate MD5 hash",
 152                 "Whether or not MD5 hashes should be generated and shown for each payload.",
 153                 &generate_md5_hash);
 154 }
 155
 156 void
 157 proto_reg_handoff_discard(void)
 158 {
 159         dissector_handle_t discard_handle;
 160
 161         discard_handle = create_dissector_handle(dissect_discard, proto_discard);
 162         dissector_add_uint_with_preference("udp.port", DISCARD_PORT_UDP, discard_handle);
 163         dissector_add_uint_with_preference("tcp.port", DISCARD_PORT_TCP, discard_handle);
 164 }
 165
 166 /*
 167  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 168  *
 169  * Local variables:
 170  * c-basic-offset: 8
 171  * tab-width: 8
 172  * indent-tabs-mode: t
 173  * End:
 174  *
 175  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 176  * :indentSize=8:tabSize=8:noTabs=false:
 177  */