sniffnet 0.3.2

Application to sniff and filter network traffic. Generates a human-readable report of the observed packets.
sniffnet-0.3.2 is not a library.

sniffnet (network packets sniffer/filter)

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Aim of the application is to intercept and filter network traffic through a user specified interface of a computer.

The application will periodically generate and update a human-readable textual report, providing statistics about the observed network packets.

Several command line options are available to select the network adapter to inspect, to set a desired report update frequency and to specify filters on the observed traffic.

Install

The application binary can be installed with cargo install sniffnet

The application can then be run using sniffnet [OPTIONS]

Command line options

  • -a, --adapter: specifies the name of the network adapter to be inspected; if omitted the default adapter is chosen.

  • --app: filters packets on the basis of the provided application layer protocol.

  • -d, --device-list: prints list of the available network interfaces. Immediately terminates the program.

  • -h, --highest-port: specifies the maximum port value to be considered; if omitted there is no ports higher bound.

  • -i, --interval: sets the interval of time between report updates (value in seconds).

  • -l, --lowest-port: specifies the minimum port value to be considered; if omitted there is no ports lower bound.

  • -m, --minimum-packets: sets the minimum value of transited packets for an [address:port] to be printed in the report.

  • -n, --net: filters packets on the basis of the provided IP address version (IPv4 or IPv6).

  • -o, --output-file: specifies the name of output file containing the textual report; if omitted the file name is sniffnet_report.txt

  • -t, --trans: filters packets on the basis of the provided transport layer protocol (TCP or UDP).

User interactions during application execution

The user can interact with the sniffing process through the terminal window.

  • Pause: to temporarily pause the sniffing process, the user can type a 'p' character in the terminal window.

  • Resume: to later resume the sniffing process, the user can type a 'r' character in the terminal window.

  • Stop: to stop the application execution, the user can type a 's' character in the terminal window.

Textual report structure

In this section is reported the structure of the output report file generated, to help the users better understand and interpret it.

Report header

The first section of the textual report contains a header summarizing different useful information.

report_part_1

First, it specifies the name of the network adapter analyzed during the sniffing process.

Then there is a detail about the initial timestamp of the sniffing process, the last timestamp in which the report was updated, and the number of times the report was updated (re-written from scratch with updated data).

It also describes the status of the possible filters applicable by the user through the command line: IP address version, transport layer protocol, port minimum and maximum number, and application layer protocol.

Finally, it reports some statistics about the observed traffic: the number of [address:port] pairs considered, the total number of sniffed packets, the number (and percentage) of packets selected according to the active filters and a list of the observed application layer protocols with the respective packets count.

Report addresses list

The second section of the textual report is dedicated to the packets stream analysis for each [address:port] pair.

This analysis results in a list in which each element represents an [address:port] pair with the relative statistics.

Note that such list of elements is sorted in descending order of exchanged packets.

report_part_2

For each element it is reported the amount of exchanged data measured in number of packets and in number of bytes between the source (on the left) and the destination (on the right).

For each [address:port] pair are reported the first and the last timestamp in which a packet was transmitted between that [address:port] pair.

Level 4 and level 7 carried protocols are also described (respectively transport layer and application layer protocols); please note that application level protocols are just inferred from the transport port numbers.

Supported application layer protocols

Port number(s) Application protocol Description
20, 21 FTP File Transfer Protocol
22 SSH Secure Shell
23 Telnet Telnet
25 SMTP Simple Mail Transfer Protocol
49 TACACS Terminal Access Controller Access-Control System
53 DNS Domain Name System
67, 68 DHCP Dynamic Host Configuration Protocol
69 TFTP Trivial File Transfer Protocol
80, 8080 HTTP Hypertext Transfer Protocol
109, 110 POP Post Office Protocol
123 NTP Network Time Protocol
137, 138, 139 NetBIOS NetBIOS
143, 220 IMAP Internet Message Access Protocol
161, 162, 199 SNMP Simple Network Management Protocol
179 BGP Border Gateway Protocol
389 LDAP Lightweight Directory Access Protocol
443 HTTPS Hypertext Transfer Protocol over SSL/TLS
636 LDAPS Lightweight Directory Access Protocol over TLS/SSL
989, 990 FTPS File Transfer Protocol over TLS/SSL
993 IMAPS Internet Message Access Protocol over TLS/SSL
995 POP3S Post Office Protocol 3 over TLS/SSL
1900 SSDP Simple Service Discovery Protocol
5222 XMPP Extensible Messaging and Presence Protocol
5353 mDNS Multicast DNS

Implementation details

The application consists in three different execution flows.

The main thread waits for eventual user actions (by putting the terminal in raw mode through the crossterm::screen::raw::into_raw_mode() function and creating a crossterm::SyncReader which allows to read the input synchronously); in doing so it signals to the secondary threads when to pause or resume their work. The signaling is made possible by setting an application status, shared with the secondary threads and associated to a mutex and a condition variable.

The main() function, entry point of program execution, generates two secondary threads: one is in charge of waiting for network packets and parsing them, while the other is in charge of updating the textual report every interval seconds (with interval defined by the user through the -i option; if omitted it's equal to 5 seconds).

The thread in charge of parsing packets also insert them into a shared map, where the key part is represented by an AddressPort struct and the value part is represented by a ReportInfo struct. Before parsing each packet it checks the application status: if it is Status::Pause it waits, otherwise it proceeds parsing the packet. This thread waits for packets without consuming CPU resources through the pcap::Capture::next() function.

The thread in charge of updating the textual report sleeps for interval seconds and re-writes the report with updated traffic statistics. Before updating the report it checks the application status: if it is Status::Pause it waits, otherwise it proceeds writing the report.

Error conditions

Wrong command line options specification

  • Not existing adapter name: if a non-existing adapter name is provided, the application raises an error and terminates. In this case the application will suggest using the -d option to print on the standard output a list of the available devices. sniffnet -d prints a list of all the available network adapters names and addresses, as in the example that follows.

   device_list

  • Invalid application layer protocol filter: if an invalid string is provided the application raises an error and terminates. The list of the supported application layer protocols is available in this section. Note that not including the --app option is equal to provide --app "no filter".

  • Invalid highest port number: if the provided highest port number is not an integer in the range 0..=65535 the program raises an error and terminates. If also the lowest port number is specified and highest_port < lowest_port == true the program raises an error and terminates.

  • Invalid interval value: if the provided interval value is not an integer in the range 1..=u64::MAX the program raises an error and terminates.

  • Invalid lowest port number: if the provided lowest port number is not an integer in the range 0..=65535 the program raises an error and terminates. If also the highest port number is specified and highest_port < lowest_port == true the program raises an error and terminates.

  • Invalid minimum packets value: if the provided minimum packets value is not an integer in the range 0..=u128::MAX the program raises an error and terminates.

  • Invalid network layer protocol filter: if a string different from "IPv4", "IPv6" or "no filter" is provided (not case-sensitive), the application raises an error and terminates. Note that not including the -n option is equal to provide -n "no filter".

  • Invalid output file extension: there is no particular limitation on the output file name. However, if an invalid file extension is provided the file may result unreadable if the extension is not subsequently removed.

  • Invalid transport layer protocol filter: if a string different from "TCP", "UDP" or "no filter" is provided (not case-sensitive), the application raises an error and terminates. Note that not including the -t option is equal to provide -t "no filter".

Pcap permission denied error

You may incur in this error if you have not the privilege to open a network adapter. Full error is reported below.

error_permissions

To solve this error you can execute the following command: sudo chown username /dev/bp*

Where username can be retrieved with the command whoami

Alternatively, you can run the application as root: sudo sniffnet [OPTIONS]

In both cases you will be requested to insert your system password.

Windows configuration problems

In order to make pcap work properly on Windows systems, it is needed to download WinCap and the WinPcap Developer's Pack and to add the /Lib or /Lib/x64 folder to the LIB environment variable.

Linux configuration problems

To correctly use pcap on Linux systems, install the libraries and header files for the libpcap library. For example:

On Debian based Linux: install libpcap-dev.

On Fedora Linux: install libpcap-devel.

Note that if you are not running as root, you need to set capabilities like so: sudo setcap cap_net_raw,cap_net_admin=eip path/to/bin.

Textual report contains just the header

If the textual output is not reporting packets statistics, make sure you are sniffing the correct network adapter (use the -d option to see the full list of your network adapters' names and addresses). To inspect a network adapter of your choice, remember to specify the -a option followed by the name of the adapter to be analyzed. If you don't include such option a default adapter is chosen by the application, but it may not be the one you expected to sniff.

Note that to see report updates while sniffnet is running you may have to close and re-open the report file.

If you are still not able to see any packet statistic, then it probably means that you are just not receiving packets from the network: surf the web to receive some packets.

Other errors

Other errors, not previously listed, may occur seldom.

Most of such errors are due to the unwrapping of Result<T>, which may exceptionally contain the Err value.

This may happen in one of the following situations: activation of a pcap Capture handle, retrieval of network adapters list through pcap, selection of the default device through pcap, creation of the output file, cloning of the output file handle, acquisition of a Mutex lock, writing of the output file.

All those exceptional scenarios are managed through calls to the expect() method, providing textual feedback to the user on the cause of the panic.

The unwrap() method is used only on Option<T> values when it's certain they contain Some value.

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