forked from osmocom/wireshark
434 lines
15 KiB
C
434 lines
15 KiB
C
/* packet-imap.c
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* Routines for imap packet dissection
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* Copyright 1999, Richard Sharpe <rsharpe@ns.aus.com>
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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* Copyright 1998 Gerald Combs
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*
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* Copied from packet-tftp.c
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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#include "config.h"
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#include <epan/packet.h>
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#include <epan/strutil.h>
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#include "packet-ssl.h"
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#include "packet-ssl-utils.h"
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void proto_register_imap(void);
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void proto_reg_handoff_imap(void);
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static int proto_imap = -1;
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static int hf_imap_isrequest = -1;
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static int hf_imap_line = -1;
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static int hf_imap_request = -1;
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static int hf_imap_request_tag = -1;
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static int hf_imap_response = -1;
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static int hf_imap_response_tag = -1;
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static int hf_imap_request_command = -1;
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static int hf_imap_response_status = -1;
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static int hf_imap_request_folder = -1;
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static int hf_imap_request_uid = -1;
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static gint ett_imap = -1;
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static gint ett_imap_reqresp = -1;
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static dissector_handle_t imap_handle;
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static dissector_handle_t ssl_handle;
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static gboolean imap_ssl_heuristic = TRUE;
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#define TCP_PORT_IMAP 143
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#define TCP_PORT_SSL_IMAP 993
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#define MAX_BUFFER 1024
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#define IMAP_HEUR_LEN 5
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typedef struct imap_state {
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gboolean ssl_requested;
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gint ssl_heur_tries_left;
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} imap_state_t;
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/* Heuristic to detect plaintext or TLS ciphertext IMAP */
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static gboolean
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check_imap_heur(tvbuff_t *tvb)
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{
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const gchar *s;
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gint i;
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if (!tvb_bytes_exist(tvb, 0, IMAP_HEUR_LEN)) {
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return TRUE;
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}
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s = (const gchar *)tvb_get_ptr(tvb, 0, IMAP_HEUR_LEN);
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for (i = 0; i < IMAP_HEUR_LEN; i++) {
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if (!g_ascii_isprint(s[i])) {
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return FALSE;
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}
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}
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return TRUE;
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}
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static int
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dissect_imap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
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{
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gboolean is_request;
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proto_tree *imap_tree, *reqresp_tree;
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proto_item *ti, *hidden_item;
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gint offset = 0;
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gint uid_offset = 0;
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gint folder_offset = 0;
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const guchar *line;
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const guchar *lineend;
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const guchar *uid_line;
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const guchar *folder_line;
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gint next_offset;
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int linelen;
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int tokenlen;
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int uid_tokenlen;
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int folder_tokenlen;
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const guchar *next_token;
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const guchar *uid_next_token;
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const guchar *folder_next_token;
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guchar *tokenbuf;
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guchar *command_token;
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int iter;
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int commandlen;
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conversation_t *conversation;
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imap_state_t *session_state;
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conversation = find_or_create_conversation(pinfo);
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session_state = (imap_state_t *)conversation_get_proto_data(conversation, proto_imap);
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if (!session_state) {
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session_state = wmem_new0(wmem_file_scope(), imap_state_t);
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session_state->ssl_requested = FALSE;
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if (imap_ssl_heuristic)
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session_state->ssl_heur_tries_left = 2;
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else
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session_state->ssl_heur_tries_left = -1; /* Disabled */
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conversation_add_proto_data(conversation, proto_imap, session_state);
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}
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if (imap_ssl_heuristic && session_state->ssl_heur_tries_left < 0) {
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/* Preference changed to enabled */
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session_state->ssl_heur_tries_left = 2;
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}
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else if (!imap_ssl_heuristic && session_state->ssl_heur_tries_left >= 0) {
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/* Preference changed to disabled */
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session_state->ssl_heur_tries_left = -1;
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}
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/*
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* It is possible the IMAP session is already running over TLS and the
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* STARTTLS request/response happened before the capture began. Don't assume
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* we have plaintext without performing some heuristic checks first.
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* We have three cases:
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* 1. capture includes STARTTLS command: no need for heuristics
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* 2. capture starts with STARTTLS OK response: next frame will be TLS (need to retry heuristic)
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* 3. capture start after STARTTLS negotiation: current frame is TLS
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*/
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if (session_state->ssl_heur_tries_left > 0) {
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session_state->ssl_heur_tries_left--;
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if (!check_imap_heur(tvb)) {
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ssl_starttls_post_ack(ssl_handle, pinfo, imap_handle);
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session_state->ssl_heur_tries_left = 0;
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return call_dissector(ssl_handle, tvb, pinfo, tree);
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}
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}
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tokenbuf = (guchar *)wmem_alloc0(wmem_packet_scope(), MAX_BUFFER);
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command_token = (guchar *)wmem_alloc0(wmem_packet_scope(), MAX_BUFFER);
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commandlen = 0;
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folder_offset = 0;
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folder_tokenlen = 0;
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folder_line = NULL;
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col_set_str(pinfo->cinfo, COL_PROTOCOL, "IMAP");
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if (pinfo->match_uint == pinfo->destport)
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is_request = TRUE;
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else
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is_request = FALSE;
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/*
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* Put the first line from the buffer into the summary
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* (but leave out the line terminator).
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*/
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linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, FALSE);
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line = tvb_get_ptr(tvb, offset, linelen);
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col_add_fstr(pinfo->cinfo, COL_INFO, "%s: %s", is_request ? "Request" : "Response", format_text(wmem_packet_scope(), line, linelen));
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{
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ti = proto_tree_add_item(tree, proto_imap, tvb, offset, -1, ENC_NA);
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imap_tree = proto_item_add_subtree(ti, ett_imap);
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hidden_item = proto_tree_add_boolean(imap_tree, hf_imap_isrequest, tvb, 0, 0, is_request);
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PROTO_ITEM_SET_HIDDEN(hidden_item);
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while(tvb_offset_exists(tvb, offset)) {
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/*
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* Find the end of each line
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*
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* Note that "tvb_find_line_end()" will return a value that is
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* not longer than what's in the buffer, so the "tvb_get_ptr()"
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* call won't throw an exception.
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*/
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linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, FALSE);
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line = tvb_get_ptr(tvb, offset, linelen);
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lineend = (line + linelen);
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/*
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* Put the line into the protocol tree.
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*/
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ti = proto_tree_add_item(imap_tree, hf_imap_line, tvb, offset, next_offset - offset, ENC_ASCII|ENC_NA);
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reqresp_tree = proto_item_add_subtree(ti, ett_imap_reqresp);
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/*
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* Check that the line doesn't begin with '*', because that's a continuation line.
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* Otherwise if a tag is present then extract tokens.
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*/
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if ( (line) && ((line[0] != '*') || (TRUE == is_request)) ) {
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/*
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* Show each line as tags + requests or replies.
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*/
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/*
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* Extract the first token, and, if there is a first
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* token, add it as the request or reply tag.
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*/
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tokenlen = get_token_len(line, lineend, &next_token);
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if (tokenlen != 0) {
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proto_tree_add_item(reqresp_tree, (is_request) ? hf_imap_request_tag : hf_imap_response_tag, tvb, offset, tokenlen, ENC_ASCII|ENC_NA);
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offset += (gint) (next_token - line);
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linelen -= (int) (next_token - line);
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line = next_token;
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}
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/*
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* Extract second token, and, if there is a second
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* token, and it's not uid, add it as the request or reply command.
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*/
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tokenlen = get_token_len(line, lineend, &next_token);
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if (tokenlen != 0) {
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for (iter = 0; iter < tokenlen && iter < MAX_BUFFER-1; iter++) {
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tokenbuf[iter] = g_ascii_tolower(line[iter]);
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}
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if (tree && is_request && strncmp(tokenbuf, "uid", tokenlen) == 0) {
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proto_tree_add_item(reqresp_tree, hf_imap_request_uid, tvb, offset, tokenlen, ENC_ASCII|ENC_NA);
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/*
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* UID is a precursor to a command, if following the tag,
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* so move to next token to grab the actual command.
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*/
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uid_offset = offset;
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uid_offset += (gint) (next_token - line);
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uid_line = next_token;
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uid_tokenlen = get_token_len(uid_line, lineend, &uid_next_token);
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if (tokenlen != 0) {
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proto_tree_add_item(reqresp_tree, hf_imap_request_command, tvb, uid_offset, uid_tokenlen, ENC_ASCII|ENC_NA);
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/*
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* Save command string to do specialized processing.
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*/
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for (iter = 0; iter < uid_tokenlen && iter < MAX_BUFFER-1; iter++) {
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command_token[iter] = g_ascii_tolower(uid_line[iter]);
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}
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commandlen = uid_tokenlen;
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folder_offset = uid_offset;
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folder_offset += (gint) (uid_next_token - uid_line);
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folder_line = uid_next_token;
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folder_tokenlen = get_token_len(folder_line, lineend, &folder_next_token);
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}
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} else {
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/*
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* Not a UID request so perform normal parsing.
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*/
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proto_tree_add_item(reqresp_tree, (is_request) ? hf_imap_request_command : hf_imap_response_status, tvb, offset, tokenlen, ENC_ASCII|ENC_NA);
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if (is_request) {
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/*
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* Save command string to do specialized processing.
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*/
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for (iter = 0; iter < tokenlen && iter < 256; iter++) {
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command_token[iter] = g_ascii_tolower(line[iter]);
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}
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commandlen = tokenlen;
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folder_offset = offset;
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folder_offset += (gint) (next_token - line);
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folder_line = next_token;
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folder_tokenlen = get_token_len(folder_line, lineend, &folder_next_token);
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}
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}
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if (tree && commandlen > 0 && (
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strncmp(command_token, "select", commandlen) == 0 ||
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strncmp(command_token, "examine", commandlen) == 0 ||
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strncmp(command_token, "create", commandlen) == 0 ||
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strncmp(command_token, "delete", commandlen) == 0 ||
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strncmp(command_token, "rename", commandlen) == 0 ||
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strncmp(command_token, "subscribe", commandlen) == 0 ||
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strncmp(command_token, "unsubscribe", commandlen) == 0 ||
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strncmp(command_token, "status", commandlen) == 0 ||
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strncmp(command_token, "append", commandlen) == 0 ||
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strncmp(command_token, "search", commandlen) == 0)) {
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/*
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* These commands support folder as an argument,
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* so parse out the folder name.
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*/
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if (folder_tokenlen != 0)
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proto_tree_add_item(reqresp_tree, hf_imap_request_folder, tvb, folder_offset, folder_tokenlen, ENC_ASCII|ENC_NA);
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}
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if (tree && is_request && (NULL != folder_line) && strncmp(command_token, "copy", commandlen) == 0) {
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/*
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* Handle the copy command separately since folder
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* is the second argument for this command.
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*/
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folder_offset += (gint) (folder_next_token - folder_line);
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folder_line = folder_next_token;
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folder_tokenlen = get_token_len(folder_line, lineend, &folder_next_token);
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if (folder_tokenlen != 0)
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proto_tree_add_item(reqresp_tree, hf_imap_request_folder, tvb, folder_offset, folder_tokenlen, ENC_ASCII|ENC_NA);
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}
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/* If not yet switched to TLS, check for STARTTLS. */
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if (session_state->ssl_requested) {
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if (!is_request && strncmp(tokenbuf, "ok", tokenlen) == 0) {
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/* STARTTLS accepted, next reply will be TLS. */
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ssl_starttls_ack(ssl_handle, pinfo, imap_handle);
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if (session_state->ssl_heur_tries_left > 0) {
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session_state->ssl_heur_tries_left = 0;
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}
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}
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session_state->ssl_requested = FALSE;
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}
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if (is_request && commandlen > 0 &&
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strncmp(command_token, "starttls", commandlen) == 0) {
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/* If next response is OK, then TLS should be commenced. */
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session_state->ssl_requested = TRUE;
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}
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}
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/*
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* Add the rest of the line as request or reply data.
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*/
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if (linelen != 0) {
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proto_tree_add_item(reqresp_tree, (is_request) ? hf_imap_request : hf_imap_response, tvb, offset, linelen, ENC_ASCII|ENC_NA);
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}
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}
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offset = next_offset; /* Skip over last line and \r\n at the end of it */
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}
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}
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return tvb_captured_length(tvb);
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}
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void
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proto_register_imap(void)
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{
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static hf_register_info hf[] = {
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{ &hf_imap_isrequest,
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{ "Request", "imap.isrequest",
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FT_BOOLEAN, BASE_NONE, NULL, 0x0,
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"TRUE if IMAP request, FALSE otherwise", HFILL }
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},
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{ &hf_imap_line,
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{ "Line", "imap.line",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"A line of an IMAP message", HFILL }
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},
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{ &hf_imap_request,
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{ "Request", "imap.request",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"Remainder of request line", HFILL }
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},
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{ &hf_imap_request_tag,
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{ "Request Tag", "imap.request_tag",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"First token of request line", HFILL }
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},
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{ &hf_imap_response,
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{ "Response", "imap.response",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"Remainder of response line", HFILL }
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},
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{ &hf_imap_response_tag,
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{ "Response Tag", "imap.response_tag",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"First token of response line", HFILL }
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},
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{ &hf_imap_request_command,
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{ "Request Command", "imap.request.command",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"Request command name", HFILL }
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},
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{ &hf_imap_response_status,
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{ "Response Status", "imap.response.status",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"Response status code", HFILL }
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},
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{ &hf_imap_request_folder,
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{ "Request Folder", "imap.request.folder",
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FT_STRINGZ, BASE_NONE, NULL, 0x0,
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"Request command folder", HFILL }
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},
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{ &hf_imap_request_uid,
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{ "Request isUID", "imap.request.command.uid",
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FT_BOOLEAN, BASE_NONE, NULL, 0x0,
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"Request command uid", HFILL }
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}
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};
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static gint *ett[] = {
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&ett_imap,
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&ett_imap_reqresp,
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};
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module_t *imap_module;
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proto_imap = proto_register_protocol("Internet Message Access Protocol", "IMAP", "imap");
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imap_handle = register_dissector("imap", dissect_imap, proto_imap);
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proto_register_field_array(proto_imap, hf, array_length(hf));
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proto_register_subtree_array(ett, array_length(ett));
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imap_module = prefs_register_protocol(proto_imap, NULL);
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prefs_register_bool_preference(imap_module, "ssl_heuristic",
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"Use heuristic detection for TLS",
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"Whether to use heuristics for post-STARTTLS detection of encrypted IMAP conversations",
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&imap_ssl_heuristic);
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}
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void
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proto_reg_handoff_imap(void)
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{
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dissector_add_uint_with_preference("tcp.port", TCP_PORT_IMAP, imap_handle);
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ssl_dissector_add(TCP_PORT_SSL_IMAP, imap_handle);
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ssl_handle = find_dissector("ssl");
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}
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/*
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* Editor modelines - http://www.wireshark.org/tools/modelines.html
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*
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* Local variables:
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* c-basic-offset: 2
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* tab-width: 8
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* indent-tabs-mode: nil
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* End:
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*
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* vi: set shiftwidth=2 tabstop=8 expandtab:
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* :indentSize=2:tabSize=8:noTabs=true
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*/
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