c072a10770
* Support port forwarding of literal IPv6 addresses To disambiguate between colons as host:port separators and as IPv6 address separators, literal IPv6 addresses use square brackets around the address (https://en.wikipedia.org/wiki/IPv6_address#Literal_IPv6_addresses_in_network_resource_identifiers). So host ::1, port 22 is written as [::1]:22, and therefore a simple concatenation of host, colon, and port doesn't work. Fortunately net.JoinHostPort already implements this functionality, so with a bit of type gymnastics we can generate dest in an IPv6-safe way. * Support port forwarding of literal IPv6 addresses To disambiguate between colons as host:port separators and as IPv6 address separators, literal IPv6 addresses use square brackets around the address (https://en.wikipedia.org/wiki/IPv6_address#Literal_IPv6_addresses_in_network_resource_identifiers). So host ::1, port 22 is written as [::1]:22, and therefore a simple concatenation of host, colon, and port doesn't work. Fortunately net.JoinHostPort already implements this functionality, so with a bit of type gymnastics we can generate dest in an IPv6-safe way.
59 lines
1.3 KiB
Go
59 lines
1.3 KiB
Go
package ssh
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import (
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"io"
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"net"
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"strconv"
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gossh "golang.org/x/crypto/ssh"
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)
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// direct-tcpip data struct as specified in RFC4254, Section 7.2
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type forwardData struct {
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DestinationHost string
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DestinationPort uint32
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OriginatorHost string
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OriginatorPort uint32
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}
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func directTcpipHandler(srv *Server, conn *gossh.ServerConn, newChan gossh.NewChannel, ctx Context) {
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d := forwardData{}
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if err := gossh.Unmarshal(newChan.ExtraData(), &d); err != nil {
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newChan.Reject(gossh.ConnectionFailed, "error parsing forward data: "+err.Error())
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return
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}
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if srv.LocalPortForwardingCallback == nil || !srv.LocalPortForwardingCallback(ctx, d.DestinationHost, d.DestinationPort) {
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newChan.Reject(gossh.Prohibited, "port forwarding is disabled")
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return
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}
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dest := net.JoinHostPort(d.DestinationHost, strconv.FormatInt(int64(d.DestinationPort), 10))
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var dialer net.Dialer
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dconn, err := dialer.DialContext(ctx, "tcp", dest)
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if err != nil {
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newChan.Reject(gossh.ConnectionFailed, err.Error())
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return
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}
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ch, reqs, err := newChan.Accept()
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if err != nil {
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dconn.Close()
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return
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}
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go gossh.DiscardRequests(reqs)
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go func() {
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defer ch.Close()
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defer dconn.Close()
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io.Copy(ch, dconn)
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}()
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go func() {
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defer ch.Close()
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defer dconn.Close()
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io.Copy(dconn, ch)
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}()
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}
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