82 lines
2.9 KiB
Go
82 lines
2.9 KiB
Go
package services
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import (
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"crypto/rand"
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"crypto/rsa"
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"fmt"
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"net"
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"strconv"
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"time"
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"golang.org/x/crypto/ssh"
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)
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// NewSSHHandler returns a TCP handler that performs SSH handshake and logs auth attempts.
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// getSigner is used to obtain a host key signer (so the app can reuse/generate one).
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func NewSSHHandler(log LoggerFunc, getSigner func() (ssh.Signer, error)) Handler {
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return func(conn net.Conn) {
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defer conn.Close()
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remote := conn.RemoteAddr().String()
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sessionID := fmt.Sprintf("%x", time.Now().UnixNano())
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start := time.Now()
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signer, err := getSigner()
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if err != nil {
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log(Record{Timestamp: Now(), RemoteAddr: remoteIP(remote), RemotePort: remotePort(remote), Service: "ssh", Details: map[string]string{"error": "hostkey"}, RawPayload: err.Error()})
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return
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}
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var authAttempts int
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var lastUser, lastPass string
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cfg := &ssh.ServerConfig{
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NoClientAuth: false,
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ServerVersion: "SSH-2.0-OpenSSH_7.9p1 Ubuntu-10",
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PasswordCallback: func(c ssh.ConnMetadata, pass []byte) (*ssh.Permissions, error) {
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authAttempts++
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lastUser = c.User()
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lastPass = string(pass)
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log(Record{Timestamp: Now(), RemoteAddr: remoteIP(remote), RemotePort: remotePort(remote), Service: "ssh", Details: map[string]string{
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"event": "auth_attempt",
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"attempt": strconv.Itoa(authAttempts),
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"username": lastUser,
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"password": lastPass,
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"client": string(c.ClientVersion()),
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}})
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return nil, fmt.Errorf("permission denied")
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},
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}
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cfg.AddHostKey(signer)
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_ = conn.SetDeadline(time.Now().Add(2 * time.Minute))
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sc, chans, reqs, err := ssh.NewServerConn(conn, cfg)
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if err != nil {
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log(Record{Timestamp: Now(), RemoteAddr: remoteIP(remote), RemotePort: remotePort(remote), Service: "ssh", Details: map[string]string{
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"event": "session_end",
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"session_id": sessionID,
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"auth_attempts": strconv.Itoa(authAttempts),
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"duration_sec": fmt.Sprintf("%.2f", time.Since(start).Seconds()),
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"last_username": lastUser,
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"last_password": lastPass,
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"error": err.Error(),
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}})
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return
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}
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go ssh.DiscardRequests(reqs)
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for ch := range chans {
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_ = ch.Reject(ssh.Prohibited, "not allowed")
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}
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_ = sc.Close()
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}
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}
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// DefaultSigner provides a simple RSA signer if caller doesn't have one.
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func DefaultSigner() (ssh.Signer, error) {
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key, err := rsa.GenerateKey(rand.Reader, 2048)
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if err != nil {
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return nil, err
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}
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return ssh.NewSignerFromKey(key)
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}
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