A small TCP proxy written in Go
This project was intended for debugging text-based protocols. The next version will address binary protocols.
Binaries
Download the latest release, or
Install latest release now with curl https://i.jpillora.com/go-tcp-proxy! | bash
Source
$ go get -v github.com/jpillora/go-tcp-proxy/cmd/tcp-proxy$ tcp-proxy --help
Usage of tcp-proxy:
-c: output ansi colors
-h: output hex
-l="localhost:9999": local address
-n: disable nagles algorithm
-r="localhost:80": remote address
-match="": match regex (in the form 'regex')
-replace="": replace regex (in the form 'regex~replacer')
-v: display server actions
-vv: display server actions and all tcp data
Note: Regex match and replace only works on text strings and does NOT work across packet boundaries
Since HTTP runs over TCP, we can also use tcp-proxy as a primitive HTTP proxy:
$ tcp-proxy -r echo.jpillora.com:80
Proxying from localhost:9999 to echo.jpillora.com:80
Then test with curl:
$ curl -H 'Host: echo.jpillora.com' localhost:9999/foo
{
"method": "GET",
"url": "/foo"
...
}
$ tcp-proxy -r echo.jpillora.com:80 -match 'Host: (.+)'
Proxying from localhost:9999 to echo.jpillora.com:80
Matching Host: (.+)
#run curl again...
Connection #001 Match #1: Host: echo.jpillora.com
$ tcp-proxy -r echo.jpillora.com:80 -replace '"ip": "([^"]+)"~"ip": "REDACTED"'
Proxying from localhost:9999 to echo.jpillora.com:80
Replacing "ip": "([^"]+)" with "ip": "REDACTED"
#run curl again...
{
"ip": "REDACTED",
...
Note: The -replace option is in the form regex~replacer. Where replacer may contain $N to substitute in group N.
- Implement
tcpproxy.Connwhich provides accounting and hooks into the underlyingnet.Conn - Verify wire protocols by providing
encoding.BinaryUnmarshalerto atcpproxy.Conn - Modify wire protocols by also providing a map function
- Implement SOCKS v5 to allow for user-decided remote addresses