72 lines
1.8 KiB
Go
72 lines
1.8 KiB
Go
package ssh2
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import (
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"io"
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"net"
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"github.com/gliderlabs/ssh"
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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 localForwardChannelData struct {
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DestAddr string
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DestPort uint32
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OriginAddr string
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OriginPort uint32
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}
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// seetupForwardHandler sets up the forwarding handler for the ssh server
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func (ssh2 *SSH2) setupForwardHandler(server *ssh.Server) {
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if server.ChannelHandlers == nil {
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server.ChannelHandlers = make(map[string]ssh.ChannelHandler)
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for n, h := range ssh.DefaultChannelHandlers {
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server.ChannelHandlers[n] = h
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}
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}
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server.ChannelHandlers["direct-tcpip"] = ssh2.handleDirectTCP
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}
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// handleDirectTCP handles a direct tcp connection for the server
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func (ssh2 *SSH2) handleDirectTCP(srv *ssh.Server, conn *gossh.ServerConn, newChan gossh.NewChannel, ctx ssh.Context) {
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d := localForwardChannelData{}
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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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slug, ok := ssh2.Config.SlugFromHost(d.DestAddr)
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if !ok || d.DestPort != 22 || !hasPermission(ctx, slug) {
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newChan.Reject(gossh.Prohibited, "permission denied")
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return
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}
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// TODO: move this into an instance function somewhere
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dest := net.JoinHostPort(slug+"."+ssh2.Config.DefaultDomain+".wisski", "22")
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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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