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wireshark/epan/dissectors/packet-imap.c

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/* packet-imap.c
* Routines for imap packet dissection
* Copyright 1999, Richard Sharpe <rsharpe@ns.aus.com>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* Copied from packet-tftp.c
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/strutil.h>
#include "packet-ssl.h"
#include "packet-ssl-utils.h"
void proto_register_imap(void);
void proto_reg_handoff_imap(void);
static int proto_imap = -1;
static int hf_imap_isrequest = -1;
static int hf_imap_line = -1;
static int hf_imap_request = -1;
static int hf_imap_request_tag = -1;
static int hf_imap_response = -1;
static int hf_imap_response_tag = -1;
static int hf_imap_request_command = -1;
static int hf_imap_response_status = -1;
static int hf_imap_request_folder = -1;
static int hf_imap_request_uid = -1;
static gint ett_imap = -1;
static gint ett_imap_reqresp = -1;
static dissector_handle_t imap_handle;
static dissector_handle_t ssl_handle;
static gboolean imap_ssl_heuristic = TRUE;
#define TCP_PORT_IMAP 143
#define TCP_PORT_SSL_IMAP 993
#define MAX_BUFFER 1024
#define IMAP_HEUR_LEN 5
typedef struct imap_state {
gboolean ssl_requested;
gint ssl_heur_tries_left;
} imap_state_t;
/* Heuristic to detect plaintext or TLS ciphertext IMAP */
static gboolean
check_imap_heur(tvbuff_t *tvb)
{
const gchar *s;
gint i;
if (!tvb_bytes_exist(tvb, 0, IMAP_HEUR_LEN)) {
return TRUE;
}
s = (const gchar *)tvb_get_ptr(tvb, 0, IMAP_HEUR_LEN);
for (i = 0; i < IMAP_HEUR_LEN; i++) {
if (!g_ascii_isprint(s[i])) {
return FALSE;
}
}
return TRUE;
}
static int
dissect_imap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
gboolean is_request;
proto_tree *imap_tree, *reqresp_tree;
proto_item *ti, *hidden_item;
gint offset = 0;
gint uid_offset = 0;
gint folder_offset = 0;
const guchar *line;
const guchar *uid_line;
const guchar *folder_line;
gint next_offset;
int linelen;
int tokenlen;
int uid_tokenlen;
int folder_tokenlen;
const guchar *next_token;
const guchar *uid_next_token;
const guchar *folder_next_token;
guchar *tokenbuf;
guchar *command_token;
int iter;
int commandlen;
conversation_t *conversation;
imap_state_t *session_state;
conversation = find_or_create_conversation(pinfo);
session_state = (imap_state_t *)conversation_get_proto_data(conversation, proto_imap);
if (!session_state) {
session_state = wmem_new0(wmem_file_scope(), imap_state_t);
session_state->ssl_requested = FALSE;
if (imap_ssl_heuristic)
session_state->ssl_heur_tries_left = 2;
else
session_state->ssl_heur_tries_left = -1; /* Disabled */
conversation_add_proto_data(conversation, proto_imap, session_state);
}
if (imap_ssl_heuristic && session_state->ssl_heur_tries_left < 0) {
/* Preference changed to enabled */
session_state->ssl_heur_tries_left = 2;
}
else if (!imap_ssl_heuristic && session_state->ssl_heur_tries_left >= 0) {
/* Preference changed to disabled */
session_state->ssl_heur_tries_left = -1;
}
/*
* It is possible the IMAP session is already running over TLS and the
* STARTTLS request/response happened before the capture began. Don't assume
* we have plaintext without performing some heuristic checks first.
* We have three cases:
* 1. capture includes STARTTLS command: no need for heuristics
* 2. capture starts with STARTTLS OK response: next frame will be TLS (need to retry heuristic)
* 3. capture start after STARTTLS negotiation: current frame is TLS
*/
if (session_state->ssl_heur_tries_left > 0) {
session_state->ssl_heur_tries_left--;
if (!check_imap_heur(tvb)) {
ssl_starttls_post_ack(ssl_handle, pinfo, imap_handle);
session_state->ssl_heur_tries_left = 0;
return call_dissector(ssl_handle, tvb, pinfo, tree);
}
}
tokenbuf = (guchar *)wmem_alloc0(wmem_packet_scope(), MAX_BUFFER);
command_token = (guchar *)wmem_alloc0(wmem_packet_scope(), MAX_BUFFER);
commandlen = 0;
folder_offset = 0;
folder_tokenlen = 0;
folder_line = NULL;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "IMAP");
if (pinfo->match_uint == pinfo->destport)
is_request = TRUE;
else
is_request = FALSE;
/*
* Put the first line from the buffer into the summary
* (but leave out the line terminator).
*/
linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, FALSE);
line = tvb_get_ptr(tvb, offset, linelen);
col_add_fstr(pinfo->cinfo, COL_INFO, "%s: %s", is_request ? "Request" : "Response", format_text(line, linelen));
{
ti = proto_tree_add_item(tree, proto_imap, tvb, offset, -1, ENC_NA);
imap_tree = proto_item_add_subtree(ti, ett_imap);
hidden_item = proto_tree_add_boolean(imap_tree, hf_imap_isrequest, tvb, 0, 0, is_request);
PROTO_ITEM_SET_HIDDEN(hidden_item);
while(tvb_offset_exists(tvb, offset)) {
/*
* Find the end of each line
*
* Note that "tvb_find_line_end()" will return a value that is
* not longer than what's in the buffer, so the "tvb_get_ptr()"
* call won't throw an exception.
*/
linelen = tvb_find_line_end(tvb, offset, -1, &next_offset, FALSE);
line = tvb_get_ptr(tvb, offset, linelen);
/*
* Put the line into the protocol tree.
*/
ti = proto_tree_add_item(imap_tree, hf_imap_line, tvb, offset, next_offset - offset, ENC_ASCII|ENC_NA);
reqresp_tree = proto_item_add_subtree(ti, ett_imap_reqresp);
/*
* Check that the line doesn't begin with '*', because that's a continuation line.
* Otherwise if a tag is present then extract tokens.
*/
if ( (line) && ((line[0] != '*') || (TRUE == is_request)) ) {
/*
* Show each line as tags + requests or replies.
*/
/*
* Extract the first token, and, if there is a first
* token, add it as the request or reply tag.
*/
tokenlen = get_token_len(line, line + linelen, &next_token);
if (tokenlen != 0) {
proto_tree_add_item(reqresp_tree, (is_request) ? hf_imap_request_tag : hf_imap_response_tag, tvb, offset, tokenlen, ENC_ASCII|ENC_NA);
offset += (gint) (next_token - line);
linelen -= (int) (next_token - line);
line = next_token;
}
/*
* Extract second token, and, if there is a second
* token, and it's not uid, add it as the request or reply command.
*/
tokenlen = get_token_len(line, line + linelen, &next_token);
if (tokenlen != 0) {
for (iter = 0; iter < tokenlen && iter < MAX_BUFFER-1; iter++) {
tokenbuf[iter] = g_ascii_tolower(line[iter]);
}
if (tree && is_request && strncmp(tokenbuf, "uid", tokenlen) == 0) {
proto_tree_add_item(reqresp_tree, hf_imap_request_uid, tvb, offset, tokenlen, ENC_ASCII|ENC_NA);
/*
* UID is a precursor to a command, if following the tag,
* so move to next token to grab the actual command.
*/
uid_offset = offset;
uid_offset += (gint) (next_token - line);
uid_line = next_token;
uid_tokenlen = get_token_len(uid_line, uid_line + (linelen - tokenlen), &uid_next_token);
if (tokenlen != 0) {
proto_tree_add_item(reqresp_tree, hf_imap_request_command, tvb, uid_offset, uid_tokenlen, ENC_ASCII|ENC_NA);
/*
* Save command string to do specialized processing.
*/
for (iter = 0; iter < uid_tokenlen && iter < MAX_BUFFER-1; iter++) {
command_token[iter] = g_ascii_tolower(uid_line[iter]);
}
commandlen = uid_tokenlen;
folder_offset = uid_offset;
folder_offset += (gint) (uid_next_token - uid_line);
folder_line = uid_next_token;
folder_tokenlen = get_token_len(folder_line, folder_line + (linelen - tokenlen - uid_tokenlen), &folder_next_token);
}
} else {
/*
* Not a UID request so perform normal parsing.
*/
proto_tree_add_item(reqresp_tree, (is_request) ? hf_imap_request_command : hf_imap_response_status, tvb, offset, tokenlen, ENC_ASCII|ENC_NA);
if (is_request) {
/*
* Save command string to do specialized processing.
*/
for (iter = 0; iter < tokenlen && iter < 256; iter++) {
command_token[iter] = g_ascii_tolower(line[iter]);
}
commandlen = tokenlen;
folder_offset = offset;
folder_offset += (gint) (next_token - line);
folder_line = next_token;
folder_tokenlen = get_token_len(folder_line, folder_line + (linelen - tokenlen - 1), &folder_next_token);
}
}
if (tree && commandlen > 0 && (
strncmp(command_token, "select", commandlen) == 0 ||
strncmp(command_token, "examine", commandlen) == 0 ||
strncmp(command_token, "create", commandlen) == 0 ||
strncmp(command_token, "delete", commandlen) == 0 ||
strncmp(command_token, "rename", commandlen) == 0 ||
strncmp(command_token, "subscribe", commandlen) == 0 ||
strncmp(command_token, "unsubscribe", commandlen) == 0 ||
strncmp(command_token, "status", commandlen) == 0 ||
strncmp(command_token, "append", commandlen) == 0 ||
strncmp(command_token, "search", commandlen) == 0)) {
/*
* These commands support folder as an argument,
* so parse out the folder name.
*/
if (folder_tokenlen != 0)
proto_tree_add_item(reqresp_tree, hf_imap_request_folder, tvb, folder_offset, folder_tokenlen, ENC_ASCII|ENC_NA);
}
if (tree && is_request && (NULL != folder_line) && strncmp(command_token, "copy", commandlen) == 0) {
/*
* Handle the copy command separately since folder
* is the second argument for this command.
*/
folder_offset += (gint) (folder_next_token - folder_line);
folder_line = folder_next_token;
folder_tokenlen = get_token_len(folder_line, folder_line + (linelen - tokenlen), &folder_next_token);
if (folder_tokenlen != 0)
proto_tree_add_item(reqresp_tree, hf_imap_request_folder, tvb, folder_offset, folder_tokenlen, ENC_ASCII|ENC_NA);
}
/* If not yet switched to TLS, check for STARTTLS. */
if (session_state->ssl_requested) {
if (!is_request && strncmp(tokenbuf, "ok", tokenlen) == 0) {
/* STARTTLS accepted, next reply will be TLS. */
ssl_starttls_ack(ssl_handle, pinfo, imap_handle);
if (session_state->ssl_heur_tries_left > 0) {
session_state->ssl_heur_tries_left = 0;
}
}
session_state->ssl_requested = FALSE;
}
if (is_request && commandlen > 0 &&
strncmp(command_token, "starttls", commandlen) == 0) {
/* If next response is OK, then TLS should be commenced. */
session_state->ssl_requested = TRUE;
}
}
/*
* Add the rest of the line as request or reply data.
*/
if (linelen != 0) {
proto_tree_add_item(reqresp_tree, (is_request) ? hf_imap_request : hf_imap_response, tvb, offset, linelen, ENC_ASCII|ENC_NA);
}
}
offset = next_offset; /* Skip over last line and \r\n at the end of it */
}
}
return tvb_captured_length(tvb);
}
void
proto_register_imap(void)
{
static hf_register_info hf[] = {
{ &hf_imap_isrequest,
{ "Request", "imap.isrequest",
FT_BOOLEAN, BASE_NONE, NULL, 0x0,
"TRUE if IMAP request, FALSE otherwise", HFILL }
},
{ &hf_imap_line,
{ "Line", "imap.line",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"A line of an IMAP message", HFILL }
},
{ &hf_imap_request,
{ "Request", "imap.request",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"Remainder of request line", HFILL }
},
{ &hf_imap_request_tag,
{ "Request Tag", "imap.request_tag",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"First token of request line", HFILL }
},
{ &hf_imap_response,
{ "Response", "imap.response",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"Remainder of response line", HFILL }
},
{ &hf_imap_response_tag,
{ "Response Tag", "imap.response_tag",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"First token of response line", HFILL }
},
{ &hf_imap_request_command,
{ "Request Command", "imap.request.command",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"Request command name", HFILL }
},
{ &hf_imap_response_status,
{ "Response Status", "imap.response.status",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"Response status code", HFILL }
},
{ &hf_imap_request_folder,
{ "Request Folder", "imap.request.folder",
FT_STRINGZ, BASE_NONE, NULL, 0x0,
"Request command folder", HFILL }
},
{ &hf_imap_request_uid,
{ "Request isUID", "imap.request.command.uid",
FT_BOOLEAN, BASE_NONE, NULL, 0x0,
"Request command uid", HFILL }
}
};
static gint *ett[] = {
&ett_imap,
&ett_imap_reqresp,
};
module_t *imap_module;
proto_imap = proto_register_protocol("Internet Message Access Protocol", "IMAP", "imap");
imap_handle = register_dissector("imap", dissect_imap, proto_imap);
proto_register_field_array(proto_imap, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
imap_module = prefs_register_protocol(proto_imap, NULL);
prefs_register_bool_preference(imap_module, "ssl_heuristic",
"Use heuristic detection for TLS",
"Whether to use heuristics for post-STARTTLS detection of encrypted IMAP conversations",
&imap_ssl_heuristic);
}
void
proto_reg_handoff_imap(void)
{
dissector_add_uint_with_preference("tcp.port", TCP_PORT_IMAP, imap_handle);
ssl_dissector_add(TCP_PORT_SSL_IMAP, imap_handle);
ssl_handle = find_dissector("ssl");
}
/*
* Editor modelines - http://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 2
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=2 tabstop=8 expandtab:
* :indentSize=2:tabSize=8:noTabs=true
*/
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