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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,45 @@ | ||
| package cmd | ||
|
|
||
| import ( | ||
| "log" | ||
|
|
||
| "github.com/ferama/rospo/cmd/cmnflags" | ||
| "github.com/ferama/rospo/pkg/sshc" | ||
| "github.com/spf13/cobra" | ||
| ) | ||
|
|
||
| func init() { | ||
| rootCmd.AddCommand(dnsProxyCmd) | ||
| // sshc options | ||
| cmnflags.AddSshClientFlags(dnsProxyCmd.Flags()) | ||
|
|
||
| dnsProxyCmd.Flags().StringP("listen-address", "l", ":53", "the dns proxy listener address") | ||
| dnsProxyCmd.Flags().StringP("remote-dns-server", "d", sshc.DEFAULT_DNS_SERVER, "the dns address to reach through sshc") | ||
| } | ||
|
|
||
| var dnsProxyCmd = &cobra.Command{ | ||
| Use: "dns-proxy [user@]host[:port]", | ||
| Short: "Starts a dns proxy", | ||
| Long: `Starts a local dns server that sends its request through the ssh tunnel | ||
| to the configured DNS server. | ||
| `, | ||
| Args: cobra.MinimumNArgs(1), | ||
| Run: func(cmd *cobra.Command, args []string) { | ||
| sshcConf := cmnflags.GetSshClientConf(cmd, args[0]) | ||
| conn := sshc.NewSshConnection(sshcConf) | ||
| go conn.Start() | ||
|
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||
| listenAddress, _ := cmd.Flags().GetString("listen-address") | ||
| remoteDnsServer, _ := cmd.Flags().GetString("remote-dns-server") | ||
|
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| conf := &sshc.DnsProxyConf{ | ||
| ListenAddress: listenAddress, | ||
| RemoteDnsAddress: &remoteDnsServer, | ||
| } | ||
| proxy := sshc.NewDnsProxy(conn, conf) | ||
| err := proxy.Start() | ||
| if err != nil { | ||
| log.Fatalln(err) | ||
| } | ||
| }, | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,138 @@ | ||
| package sshc | ||
|
|
||
| import ( | ||
| "encoding/binary" | ||
| "fmt" | ||
| "net" | ||
|
|
||
| "github.com/miekg/dns" | ||
| ) | ||
|
|
||
| const DEFAULT_DNS_SERVER = "1.1.1.1:53" | ||
|
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| type DnsProxy struct { | ||
| sshConn *SshConnection | ||
| remoteDnsServer string | ||
| proxyListenAddr string | ||
| } | ||
|
|
||
| func NewDnsProxy(sshConn *SshConnection, conf *DnsProxyConf) *DnsProxy { | ||
| remoteDnsServer := DEFAULT_DNS_SERVER | ||
| if conf.RemoteDnsAddress != nil { | ||
| remoteDnsServer = *conf.RemoteDnsAddress | ||
| } | ||
| p := &DnsProxy{ | ||
| sshConn: sshConn, | ||
| proxyListenAddr: conf.ListenAddress, | ||
| remoteDnsServer: remoteDnsServer, | ||
| } | ||
|
|
||
| return p | ||
| } | ||
|
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||
| // resolveDomain sends a DNS query for a domain name over TCP | ||
| func (p *DnsProxy) resolveDomain(conn net.Conn, msg *dns.Msg) ([]byte, error) { | ||
| // Pack the DNS message (with the original transaction ID) | ||
| query, err := msg.Pack() | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to pack DNS message: %v", err) | ||
| } | ||
|
|
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| queryLength := make([]byte, 2) | ||
| binary.BigEndian.PutUint16(queryLength, uint16(len(query))) | ||
|
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| if _, err := conn.Write(append(queryLength, query...)); err != nil { | ||
| return nil, fmt.Errorf("failed to send DNS query: %v", err) | ||
| } | ||
|
|
||
| responseLengthBytes := make([]byte, 2) | ||
| if _, err := conn.Read(responseLengthBytes); err != nil { | ||
| return nil, fmt.Errorf("failed to read response length: %v", err) | ||
| } | ||
| responseLength := binary.BigEndian.Uint16(responseLengthBytes) | ||
|
|
||
| response := make([]byte, responseLength) | ||
| if _, err := conn.Read(response); err != nil { | ||
| return nil, fmt.Errorf("failed to read DNS response: %v", err) | ||
| } | ||
|
|
||
| return response, nil | ||
| } | ||
|
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| func (p *DnsProxy) handleDNSQuery(udpConn *net.UDPConn, clientAddr *net.UDPAddr, query []byte) { | ||
| // Unpack the DNS message | ||
| msg := new(dns.Msg) | ||
| if err := msg.Unpack(query); err != nil { | ||
| log.Printf("failed to unpack DNS query: %v", err) | ||
| return | ||
| } | ||
|
|
||
| // Extract the domain name from the query | ||
| if len(msg.Question) == 0 { | ||
| log.Printf("invalid DNS query: no question section") | ||
| return | ||
| } | ||
|
|
||
| originalID := msg.Id // Preserve the original transaction ID | ||
|
|
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| conn, err := p.sshConn.Client.Dial("tcp", p.remoteDnsServer) | ||
| if err != nil { | ||
| log.Printf("unable to connect to remote dns server: %v", err) | ||
| return | ||
| } | ||
| // Resolve the domain through the proxy | ||
| dnsResponse, err := p.resolveDomain(conn, msg) | ||
| if err != nil { | ||
| log.Printf("failed to resolve domain: %v", err) | ||
| return | ||
| } | ||
|
|
||
| // Unpack the DNS response | ||
| reply := new(dns.Msg) | ||
| if err := reply.Unpack(dnsResponse); err != nil { | ||
| log.Printf("failed to unpack DNS response: %v", err) | ||
| return | ||
| } | ||
|
|
||
| // Set the original transaction ID back into the response | ||
| reply.Id = originalID | ||
|
|
||
| // Pack the modified response (with correct ID) | ||
| finalResponse, err := reply.Pack() | ||
| if err != nil { | ||
| log.Printf("failed to pack final DNS response: %v", err) | ||
| return | ||
| } | ||
|
|
||
| // Send the DNS response back to the client | ||
| if _, err := udpConn.WriteToUDP(finalResponse, clientAddr); err != nil { | ||
| log.Printf("failed to send DNS response: %v", err) | ||
| return | ||
| } | ||
| } | ||
|
|
||
| func (p *DnsProxy) Start() error { | ||
| p.sshConn.ReadyWait() | ||
|
|
||
| addr, err := net.ResolveUDPAddr("udp", p.proxyListenAddr) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to resolve UDP address: %v", err) | ||
| } | ||
|
|
||
| udpConn, err := net.ListenUDP("udp", addr) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to listen on UDP port 53: %v", err) | ||
| } | ||
| defer udpConn.Close() | ||
| log.Printf("dns-proxy listening on UDP: %s. Using remote dns: %s", p.proxyListenAddr, p.remoteDnsServer) | ||
|
|
||
| // Handle incoming DNS queries | ||
| buf := make([]byte, 4096) | ||
| for { | ||
| n, clientAddr, err := udpConn.ReadFromUDP(buf) | ||
| if err != nil { | ||
| continue | ||
| } | ||
| go p.handleDNSQuery(udpConn, clientAddr, buf[:n]) | ||
| } | ||
| } |