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/*
* mail_smtp.c
*
* Copyright (C) 2011-19 - ntop.org
* Copyright (C) 2009-2011 by ipoque GmbH
*
* This file is part of nDPI, an open source deep packet inspection
* library based on the OpenDPI and PACE technology by ipoque GmbH
*
* nDPI is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* nDPI 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with nDPI. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include "ndpi_protocol_ids.h"
#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_MAIL_SMTP
#include "ndpi_api.h"
#define SMTP_BIT_220 0x01
#define SMTP_BIT_250 0x02
#define SMTP_BIT_235 0x04
#define SMTP_BIT_334 0x08
#define SMTP_BIT_354 0x10
#define SMTP_BIT_HELO_EHLO 0x20
#define SMTP_BIT_MAIL 0x40
#define SMTP_BIT_RCPT 0x80
#define SMTP_BIT_AUTH 0x100
#define SMTP_BIT_STARTTLS 0x200
#define SMTP_BIT_DATA 0x400
#define SMTP_BIT_NOOP 0x800
#define SMTP_BIT_RSET 0x1000
#define SMTP_BIT_TlRM 0x2000
/* #define SMTP_DEBUG 1 */
static void ndpi_int_mail_smtp_add_connection(struct ndpi_detection_module_struct
*ndpi_struct, struct ndpi_flow_struct *flow) {
#ifdef SMTP_DEBUG
printf("**** %s()\n", __FUNCTION__);
#endif
ndpi_set_detected_protocol(ndpi_struct, flow,
NDPI_PROTOCOL_MAIL_SMTP, NDPI_PROTOCOL_UNKNOWN);
}
/* **************************************** */
static void smtpInitExtraPacketProcessing(struct ndpi_flow_struct *flow);
/* **************************************** */
void ndpi_search_mail_smtp_tcp(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow) {
struct ndpi_packet_struct *packet = &flow->packet;
NDPI_LOG_DBG(ndpi_struct, "search mail_smtp\n");
if((packet->payload_packet_len > 2)
&& (packet->parsed_lines < NDPI_MAX_PARSE_LINES_PER_PACKET)
&& (ntohs(get_u_int16_t(packet->payload, packet->payload_packet_len - 2)) == 0x0d0a)
) {
u_int8_t a;
u_int8_t bit_count = 0;
NDPI_PARSE_PACKET_LINE_INFO(ndpi_struct, flow, packet);
for(a = 0; a < packet->parsed_lines; a++) {
// expected server responses
if(packet->line[a].len >= 3) {
if(memcmp(packet->line[a].ptr, "220", 3) == 0) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_220;
} else if(memcmp(packet->line[a].ptr, "250", 3) == 0) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_250;
} else if(memcmp(packet->line[a].ptr, "235", 3) == 0) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_235;
} else if(memcmp(packet->line[a].ptr, "334", 3) == 0) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_334;
} else if(memcmp(packet->line[a].ptr, "354", 3) == 0) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_354;
}
}
// expected client requests
if(packet->line[a].len >= 5) {
if((((packet->line[a].ptr[0] == 'H' || packet->line[a].ptr[0] == 'h')
&& (packet->line[a].ptr[1] == 'E' || packet->line[a].ptr[1] == 'e'))
|| ((packet->line[a].ptr[0] == 'E' || packet->line[a].ptr[0] == 'e')
&& (packet->line[a].ptr[1] == 'H' || packet->line[a].ptr[1] == 'h')))
&& (packet->line[a].ptr[2] == 'L' || packet->line[a].ptr[2] == 'l')
&& (packet->line[a].ptr[3] == 'O' || packet->line[a].ptr[3] == 'o')
&& packet->line[a].ptr[4] == ' ') {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_HELO_EHLO;
flow->protos.ftp_imap_pop_smtp.auth_found = 0;
} else if((packet->line[a].ptr[0] == 'M' || packet->line[a].ptr[0] == 'm')
&& (packet->line[a].ptr[1] == 'A' || packet->line[a].ptr[1] == 'a')
&& (packet->line[a].ptr[2] == 'I' || packet->line[a].ptr[2] == 'i')
&& (packet->line[a].ptr[3] == 'L' || packet->line[a].ptr[3] == 'l')
&& packet->line[a].ptr[4] == ' ') {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_MAIL;
flow->protos.ftp_imap_pop_smtp.auth_found = 0;
} else if((packet->line[a].ptr[0] == 'R' || packet->line[a].ptr[0] == 'r')
&& (packet->line[a].ptr[1] == 'C' || packet->line[a].ptr[1] == 'c')
&& (packet->line[a].ptr[2] == 'P' || packet->line[a].ptr[2] == 'p')
&& (packet->line[a].ptr[3] == 'T' || packet->line[a].ptr[3] == 't')
&& packet->line[a].ptr[4] == ' ') {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_RCPT;
flow->protos.ftp_imap_pop_smtp.auth_found = 0;
} else if((packet->line[a].ptr[0] == 'A' || packet->line[a].ptr[0] == 'a')
&& (packet->line[a].ptr[1] == 'U' || packet->line[a].ptr[1] == 'u')
&& (packet->line[a].ptr[2] == 'T' || packet->line[a].ptr[2] == 't')
&& (packet->line[a].ptr[3] == 'H' || packet->line[a].ptr[3] == 'h')
&& packet->line[a].ptr[4] == ' ') {
#ifdef SMTP_DEBUG
printf("%s() AUTH [%s]\n", __FUNCTION__, packet->line[a].ptr);
#endif
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_AUTH;
flow->protos.ftp_imap_pop_smtp.auth_found = 1;
} else {
if(packet->line[a].ptr[3] != ' ') {
#ifdef SMTP_DEBUG
printf("%s() => [%s]\n", __FUNCTION__, packet->line[a].ptr);
#endif
if(flow->protos.ftp_imap_pop_smtp.auth_found) {
if(flow->protos.ftp_imap_pop_smtp.username[0] == '\0') {
/* Username */
u_int8_t buf[48];
u_char *out;
size_t out_len;
ndpi_user_pwd_payload_copy(buf, sizeof(buf), 0,
packet->line[a].ptr, packet->line[a].len);
#ifdef SMTP_DEBUG
printf("%s() => [auth: %u] (1) [%s]\n", __FUNCTION__, flow->protos.ftp_imap_pop_smtp.auth_found, buf);
#endif
out = ndpi_base64_decode((const u_char*)buf, (size_t)strlen((const char*)buf), &out_len);
if(out) {
snprintf(flow->protos.ftp_imap_pop_smtp.username,
sizeof(flow->protos.ftp_imap_pop_smtp.username), "%s", out);
ndpi_free(out);
}
} else if(flow->protos.ftp_imap_pop_smtp.password[0] == '\0') {
/* Password */
u_int8_t buf[48];
u_char *out;
size_t out_len;
ndpi_user_pwd_payload_copy(buf, sizeof(buf), 0,
packet->line[a].ptr, packet->line[a].len);
#ifdef SMTP_DEBUG
printf("%s() => [auth: %u] (2) [%s]\n", __FUNCTION__, flow->protos.ftp_imap_pop_smtp.auth_found, buf);
#endif
out = ndpi_base64_decode((const u_char*)buf, (size_t)strlen((const char*)buf), &out_len);
if(out) {
snprintf(flow->protos.ftp_imap_pop_smtp.password,
sizeof(flow->protos.ftp_imap_pop_smtp.password), "%s", out);
ndpi_free(out);
}
} else {
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
return;
}
flow->protos.ftp_imap_pop_smtp.auth_found++;
}
}
}
}
if(packet->line[a].len >= 8) {
if((packet->line[a].ptr[0] == 'S' || packet->line[a].ptr[0] == 's')
&& (packet->line[a].ptr[1] == 'T' || packet->line[a].ptr[1] == 't')
&& (packet->line[a].ptr[2] == 'A' || packet->line[a].ptr[2] == 'a')
&& (packet->line[a].ptr[3] == 'R' || packet->line[a].ptr[3] == 'r')
&& (packet->line[a].ptr[4] == 'T' || packet->line[a].ptr[4] == 't')
&& (packet->line[a].ptr[5] == 'T' || packet->line[a].ptr[5] == 't')
&& (packet->line[a].ptr[6] == 'L' || packet->line[a].ptr[6] == 'l')
&& (packet->line[a].ptr[7] == 'S' || packet->line[a].ptr[7] == 's')) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_STARTTLS;
}
}
if(packet->line[a].len >= 4) {
if((packet->line[a].ptr[0] == 'D' || packet->line[a].ptr[0] == 'd')
&& (packet->line[a].ptr[1] == 'A' || packet->line[a].ptr[1] == 'a')
&& (packet->line[a].ptr[2] == 'T' || packet->line[a].ptr[2] == 't')
&& (packet->line[a].ptr[3] == 'A' || packet->line[a].ptr[3] == 'a')) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_DATA;
} else if((packet->line[a].ptr[0] == 'N' || packet->line[a].ptr[0] == 'n')
&& (packet->line[a].ptr[1] == 'O' || packet->line[a].ptr[1] == 'o')
&& (packet->line[a].ptr[2] == 'O' || packet->line[a].ptr[2] == 'o')
&& (packet->line[a].ptr[3] == 'P' || packet->line[a].ptr[3] == 'p')) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_NOOP;
} else if((packet->line[a].ptr[0] == 'R' || packet->line[a].ptr[0] == 'r')
&& (packet->line[a].ptr[1] == 'S' || packet->line[a].ptr[1] == 's')
&& (packet->line[a].ptr[2] == 'E' || packet->line[a].ptr[2] == 'e')
&& (packet->line[a].ptr[3] == 'T' || packet->line[a].ptr[3] == 't')) {
flow->l4.tcp.smtp_command_bitmask |= SMTP_BIT_RSET;
}
}
}
// now count the bits set in the bitmask
if(flow->l4.tcp.smtp_command_bitmask != 0) {
for(a = 0; a < 16; a++) {
bit_count += (flow->l4.tcp.smtp_command_bitmask >> a) & 0x01;
}
}
NDPI_LOG_DBG2(ndpi_struct, "seen smtp commands and responses: %u\n",
bit_count);
if(bit_count >= 3) {
NDPI_LOG_INFO(ndpi_struct, "mail smtp identified\n");
#ifdef SMTP_DEBUG
printf("%s() [bit_count: %u][%s]\n", __FUNCTION__,
bit_count, flow->protos.ftp_imap_pop_smtp.password);
#endif
ndpi_int_mail_smtp_add_connection(ndpi_struct, flow);
smtpInitExtraPacketProcessing(flow);
return;
}
if(bit_count >= 1 && flow->packet_counter < 12) {
return;
}
}
/* when the first or second packets are split into two packets, those packets are ignored. */
if(flow->packet_counter <= 4 &&
packet->payload_packet_len >= 4 &&
(ntohs(get_u_int16_t(packet->payload, packet->payload_packet_len - 2)) == 0x0d0a
|| memcmp(packet->payload, "220", 3) == 0 || memcmp(packet->payload, "EHLO", 4) == 0)) {
NDPI_LOG_DBG2(ndpi_struct, "maybe SMTP, need next packet\n");
return;
}
if(!flow->check_extra_packets)
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}
/* **************************************** */
int ndpi_extra_search_mail_smtp_tcp(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow) {
int rc;
ndpi_search_mail_smtp_tcp(ndpi_struct, flow);
rc = (flow->protos.ftp_imap_pop_smtp.password[0] == '\0') ? 1 : 0;
#ifdef SMTP_DEBUG
printf("**** %s() [rc: %d]\n", __FUNCTION__, rc);
#endif
return(rc);
}
/* **************************************** */
static void smtpInitExtraPacketProcessing(struct ndpi_flow_struct *flow) {
#ifdef SMTP_DEBUG
static u_int num = 0;
printf("**** %s(%u)\n", __FUNCTION__, ++num);
#endif
flow->check_extra_packets = 1;
/* At most 7 packets should almost always be enough */
flow->max_extra_packets_to_check = 12;
flow->extra_packets_func = ndpi_extra_search_mail_smtp_tcp;
}
/* **************************************** */
void init_mail_smtp_dissector(struct ndpi_detection_module_struct *ndpi_struct,
u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask) {
ndpi_set_bitmask_protocol_detection("MAIL_SMTP", ndpi_struct, detection_bitmask, *id,
NDPI_PROTOCOL_MAIL_SMTP,
ndpi_search_mail_smtp_tcp,
NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
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