Go: crypto/tls: oversized record received with length 20037

[huzeyfecoskun]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go 1.8

What operating system and processor architecture are you using (go env)?

windows

What did you do?

Tls listener is not working as expected.

error
tls: oversized record received with length 20037

What did you expect to see?

i try to read tls connection

What did you see instead?

tls: oversized record received with length 20037

[mvdan]

This isn't enough information. Can you share a piece of code to reproduce the issue? If not, could you describe what the code was doing when this happened?

[FiloSottile]

That looks a lot like trying to connect to a TLS listener with another protocol, for example plain HTTP. If that's not it, we will probably need to see the client or a pcap to debug this.

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)

[henvic]

I just had a similar error... and found the following behavior weird...

Is it expected Go spitting out errors like this?

package main

import (
    "fmt"
    "net/http"
    "net/http/httptest"
    "net/url"
    "os"
)

func main() {
    var Mux = http.NewServeMux()
    var server = httptest.NewTLSServer(Mux)

    transport := &http.Transport{
        Proxy: func(req *http.Request) (*url.URL, error) {
            return url.Parse(server.URL)
        },
    }

    var r, err = http.NewRequest("GET", "https://example.com/", nil)
    if err != nil {
        fmt.Fprintf(os.Stderr, "Unexpected error: %v\n", err)
    }

    _, err = (&http.Client{Transport: transport}).Do(r)

    if err != nil {
        fmt.Fprintf(os.Stderr, "\n\n\nUnexpected request error: %v\n", err)
    }
}

When running:

$ go run foo.go
2017/05/10 10:03:18 http: TLS handshake error from 127.0.0.1:55829: tls: oversized record received with length 20037



Unexpected request error: Get https://example.com/: malformed HTTP response "\x15\x03\x01\x00\x02\x02\x16"

Notice I never printed the "TLS handshake error" error. Go just printed it to stderr. I found it really weird comparing how Go handles errors elsewhere.

Update: Actually I see it is working as intended given that http.ErrorLog is nil (https://github.com/golang/go/blob/48def43fd65388717c3edbdbbc3b3465ff9176ab/src/net/http/server.go#L2374-L2378), however the returned error value could be better, couldn't it?

[mvdan]

Funnily enough, I hit this myself today trying to write a test.

@henvic your example is similar to what I was writing, and both are wrong:

    // Proxy specifies a function to return a proxy for a given
    // Request. If the function returns a non-nil error, the
    // request is aborted with the provided error.
    //
    // The proxy type is determined by the URL scheme. "http"
    // and "socks5" are supported. If the scheme is empty,
    // "http" is assumed.
    //
    // If Proxy is nil or returns a nil *URL, no proxy is used.

Note that the "https" scheme isn't supported. I wonder if a better error should be given, as I was stuck on this for a good 20 minutes.

[mvdan]

Sending a CL with a better error.

[gopherbot]

Change https://golang.org/cl/66010 mentions this issue: net/http: error if Transport.Proxy returns https