neko-neko / utmpdump

utmp file dumper, written in golang. Output to json or tsv or csv.

utmpdump

utmpdump is output utmp format file to json or tsv or csv.

Installation

Download latest binary

Multi-platform support

• Windows
• Mac OS X
• Linux 32,64bit

Or get the library

$ go get github.com/neko-neko/utmpdump

Or clone the repository and run

$ go install github.com/neko-neko/utmpdump

Usage

Usage of utmpdump: utmpdump [options]
-f, --file <file> load a specific file instead of utmp
-t, --until <YYYYMMDDHHMMSS> display the lines until the specified time
-s, --since <YYYYMMDDHHMMSS> display the lines since the specified time
-o, --output <json/tsv/csv> display the lines at specific format. Default format is json.

Example

$ utmpdump -f /var/log/wtmp

Contributing

1. Fork it!
2. Create your feature branch: git checkout -b my-new-feature
3. Commit your changes: git commit -am 'Add some feature'
4. Push to the branch: git push origin my-new-feature
5. Submit a pull request :D

Credits

neko-neko

Contributors

stapelberg

License

MIT

utmpdump's Issues

IPv6 address mangled

Thanks for publishing this package!

I did stumble upon an issue, though: printing an utmp record when SSH'ing into my computer via IPv6, I get:

&{Type:7 Pid:1130555 Device:pts/45 Id: User:michael Host:2a02:168:9300:0:6d9:f5ff:fe1f:9de3 Exit:{Termination:0 Exit:0} Session:0 Time:Sun, 27 Oct 2019 11:56:55 CET Addr:22a:6801:93:0:d906:fff5:1ffe:e39d}

You can see that the Addr field (parsed by utmpdump) does not match the Host field (string).

This is because the ut_addr_v6 utmp field is stored in Network Byte Order (big endian), but utmpdump is reading the whole utmp file in little endian:

utmpdump/utmp/utmp.go

Line 78 in e015f7d

err := binary.Read(file, binary.LittleEndian, u)

(Side note: always using little endian to read utmp seems incorrect—isn’t the file stored in native endianness, i.e. in big endian on big endian architectures?)

A simple fix is to swap the bytes like so:

	first := uint32(0x6801022a)
	swapped := (first&0xFF)<<24 | ((first&0xFF00)>>8)<<16 | ((first&0xFF0000)>>16)<<8 | (first&0xFF000000)>>24
	fmt.Printf("%x:%x\n", (swapped>>16)&0xffff, swapped&0xffff)

A cleaner, yet backwards compatibility-breaking fix is to change Addr [4]int32 into AddrV6 [16]byte and return a net.IP from an Addr() accessor, like so:

		ip := make(net.IP, 16)
		if err := binary.Read(bytes.NewReader(r.AddrV6[:]), binary.BigEndian, ip); err != nil {
			return err
		}
		if bytes.Equal(ip[4:], net.IPv6zero[4:]) {
			// IPv4 address, shorten the slice so that net.IP behaves correctly:
			ip = ip[:4]
		}

I’m not sure whether you’re following Semantic Import Versioning in this package (you should! :), so I have not sent a pull request. Feel free to use the above in a fix, or let me know if you’d prefer a PR.

A more tedious, yet backwards-compatible way to fix this issue would be to retain the Addr field, add the AddrV6 field, add an accessor, and instead of using binary.Read, read each field separately so that we can populate both Addr and AddrV6.