/* * tftp.c * * Copyright (C) 2009-11 - ipoque GmbH * Copyright (C) 2011-22 - ntop.org * * 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 . * */ #include "ndpi_protocol_ids.h" #define NDPI_CURRENT_PROTO NDPI_PROTOCOL_TFTP #include "ndpi_api.h" /* see: https://datatracker.ietf.org/doc/html/rfc1350 */ static void ndpi_int_tftp_add_connection(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow) { ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_TFTP, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI); } static void ndpi_search_tftp(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow) { struct ndpi_packet_struct *packet = &ndpi_struct->packet; u_int16_t block_num; u_int16_t prev_num; NDPI_LOG_DBG(ndpi_struct, "search TFTP\n"); if (packet->payload_packet_len < 4 /* min. header size */ || get_u_int8_t(packet->payload, 0) != 0x00) { NDPI_EXCLUDE_PROTO(ndpi_struct, flow); return; } /* parse TFTP opcode */ switch (get_u_int8_t(packet->payload, 1)) { case 0x01: /* Read request (RRQ) */ case 0x02: /* Write request (WWQ) */ if (packet->payload[packet->payload_packet_len - 1] != 0x00 /* last pdu element is a nul terminated string */) { NDPI_EXCLUDE_PROTO(ndpi_struct, flow); return; } { uint8_t mode_found = 0; size_t mode_len; int i; size_t filename_len = 0; const char *string; size_t len = 0; bool first = true; /* Skip 2 byte opcode. */ for (i = 2; i < packet->payload_packet_len; i++) { /* Search through the payload until we find a NULL terminated string. */ if (packet->payload[i] != '\0') { len++; continue; } string = (const char *)&packet->payload[i - len]; /* Filename should be immediately after opcode followed by the mode. */ if (first) { filename_len = len; len = 0; first = false; continue; } char const * const possible_modes[] = { "netascii", "octet", "mail" }; uint8_t mode_idx; /* Check the string in the payload against the possible TFTP modes. */ for(mode_idx = 0; mode_idx < NDPI_ARRAY_LENGTH(possible_modes); ++mode_idx) { mode_len = strlen(possible_modes[mode_idx]); /* Both are now null terminated */ if (len != mode_len) { continue; } if (strncasecmp(string, possible_modes[mode_idx], mode_len) == 0) { mode_found = 1; break; } } /* Second string searched must've been the mode, break out before any following options. */ break; } /* Exclude the flow as TFPT if there was no filename and mode in the first two strings. */ if (filename_len == 0 || ndpi_is_printable_buffer(&packet->payload[2], filename_len) == 0 || mode_found == 0) { NDPI_EXCLUDE_PROTO(ndpi_struct, flow); return; } /* Dissect RRQ/WWQ filename. */ filename_len = ndpi_min(filename_len, sizeof(flow->protos.tftp.filename) - 1); memcpy(flow->protos.tftp.filename, &packet->payload[2], filename_len); flow->protos.tftp.filename[filename_len] = '\0'; /* We have seen enough and do not need any more TFTP packets. */ NDPI_LOG_INFO(ndpi_struct, "found tftp (RRQ/WWQ)\n"); ndpi_int_tftp_add_connection(ndpi_struct, flow); } return; case 0x03: /* Data (DATA) */ if (packet->payload_packet_len <= 4 /* min DATA header size */) { NDPI_EXCLUDE_PROTO(ndpi_struct, flow); return; } /* First 2 bytes were opcode so next 16 bits are the block number. * This should increment every packet but give some leeway for midstream and packet loss. */ block_num = ntohs(get_u_int16_t(packet->payload, 2)); prev_num = flow->l4.udp.tftp_data_num; flow->l4.udp.tftp_data_num = block_num; if (!(block_num == prev_num + 1 || (prev_num != 0 && block_num == prev_num))) { return; } break; case 0x04: /* Acknowledgment (ACK) */ if (packet->payload_packet_len != 4 /* ACK has a fixed packet size */) { NDPI_EXCLUDE_PROTO(ndpi_struct, flow); return; } /* First 2 bytes were opcode so next 16 bits are the block number. * This should increment every packet but give some leeway for midstream and packet loss. */ block_num = ntohs(get_u_int16_t(packet->payload, 2)); prev_num = flow->l4.udp.tftp_ack_num; flow->l4.udp.tftp_ack_num = block_num; if (!(block_num == prev_num + 1 || (block_num == prev_num))) { return; } break; case 0x05: /* Error (ERROR) */ if (packet->payload_packet_len < 5 || packet->payload[packet->payload_packet_len - 1] != 0x00 || packet->payload[2] != 0x00 || packet->payload[3] > 0x07) { NDPI_EXCLUDE_PROTO(ndpi_struct, flow); return; } break; case 0x06: /* Option Acknowledgment (OACK) */ /* No fixed lengths as it can include the options from the request. */ break; default: NDPI_EXCLUDE_PROTO(ndpi_struct, flow); return; } if (flow->l4.udp.tftp_stage < 3) { NDPI_LOG_DBG2(ndpi_struct, "maybe tftp. need next packet\n"); flow->l4.udp.tftp_stage++; return; } NDPI_LOG_INFO(ndpi_struct, "found tftp\n"); ndpi_int_tftp_add_connection(ndpi_struct, flow); } void init_tftp_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id) { ndpi_set_bitmask_protocol_detection("TFTP", ndpi_struct, *id, NDPI_PROTOCOL_TFTP, ndpi_search_tftp, NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD, SAVE_DETECTION_BITMASK_AS_UNKNOWN, ADD_TO_DETECTION_BITMASK); *id += 1; }