added git ssh support and ablity to download repo via zip, tar.gz, and bundle

internal/domain/sshserver/server.go

@@ -0,0 +1,121 @@
+// Package sshserver implements an SSH server for git clone/push/pull operations.
+// It authenticates users via their stored SSH public keys and executes
+// git-upload-pack / git-receive-pack as subprocesses.
+package sshserver
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"log"
+	"net"
+	"os"
+
+	"golang.org/x/crypto/ssh"
+	"xorm.io/xorm"
+
+	"github.com/forgeo/forgebucket/internal/config"
+)
+
+// Server is the SSH git server.
+type Server struct {
+	db  *xorm.Engine
+	cfg *config.Config
+}
+
+func New(db *xorm.Engine, cfg *config.Config) *Server {
+	return &Server{db: db, cfg: cfg}
+}
+
+// ListenAndServe binds to cfg.SSHPort, loads or generates a host key, and accepts
+// connections until ctx is cancelled. Returns nil when the context is done.
+func (s *Server) ListenAndServe(ctx context.Context) error {
+	hostKey, err := s.loadOrGenerateHostKey()
+	if err != nil {
+		return fmt.Errorf("sshserver: host key: %w", err)
+	}
+
+	srvConfig := &ssh.ServerConfig{
+		PublicKeyCallback: s.lookupKey,
+	}
+	srvConfig.AddHostKey(hostKey)
+
+	addr := ":" + s.cfg.SSHPort
+	ln, err := net.Listen("tcp", addr)
+	if err != nil {
+		log.Printf("sshserver: cannot bind %s — SSH transport disabled: %v", addr, err)
+		return nil
+	}
+	log.Printf("sshserver: listening on %s", addr)
+
+	go func() {
+		<-ctx.Done()
+		ln.Close()
+	}()
+
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			select {
+			case <-ctx.Done():
+				return nil
+			default:
+				log.Printf("sshserver: accept: %v", err)
+				continue
+			}
+		}
+		go s.handleConn(conn, srvConfig)
+	}
+}
+
+func (s *Server) handleConn(netConn net.Conn, srvConfig *ssh.ServerConfig) {
+	defer netConn.Close()
+
+	sshConn, chans, reqs, err := ssh.NewServerConn(netConn, srvConfig)
+	if err != nil {
+		return
+	}
+	defer sshConn.Close()
+
+	go ssh.DiscardRequests(reqs)
+
+	username, _ := sshConn.Permissions.Extensions["username"]
+
+	for newChan := range chans {
+		if newChan.ChannelType() != "session" {
+			newChan.Reject(ssh.UnknownChannelType, "unknown channel type") //nolint:errcheck
+			continue
+		}
+		ch, requests, err := newChan.Accept()
+		if err != nil {
+			return
+		}
+		go s.handleSession(ch, requests, username)
+	}
+}
+
+// loadOrGenerateHostKey loads the host key from SSHHostKeyPath if set,
+// otherwise generates an ephemeral RSA-4096 key (lost on restart).
+func (s *Server) loadOrGenerateHostKey() (ssh.Signer, error) {
+	if s.cfg.SSHHostKeyPath != "" {
+		data, err := os.ReadFile(s.cfg.SSHHostKeyPath)
+		if err != nil {
+			return nil, fmt.Errorf("read host key %s: %w", s.cfg.SSHHostKeyPath, err)
+		}
+		return ssh.ParsePrivateKey(data)
+	}
+
+	log.Printf("sshserver: SSH_HOST_KEY_PATH not set — generating ephemeral host key (host key changes on restart)")
+	privKey, err := rsa.GenerateKey(rand.Reader, 4096)
+	if err != nil {
+		return nil, fmt.Errorf("generate host key: %w", err)
+	}
+	keyPEM := pem.EncodeToMemory(&pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(privKey),
+	})
+	return ssh.ParsePrivateKey(keyPEM)
+}