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

internal/domain/sshserver/auth.go

@@ -0,0 +1,45 @@
+package sshserver
+
+import (
+	"crypto/md5"
+	"fmt"
+	"strings"
+
+	"golang.org/x/crypto/ssh"
+
+	"github.com/forgeo/forgebucket/internal/models"
+)
+
+// lookupKey is the SSH PublicKeyCallback. It computes the MD5 fingerprint of
+// the presented key (matching the format stored by the SSH key registration
+// handler) and looks it up in the database.
+func (s *Server) lookupKey(conn ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
+	fp := fingerprintMD5(key)
+
+	var sshKey models.SSHKey
+	if found, _ := s.db.Where("fingerprint = ?", fp).Get(&sshKey); !found {
+		return nil, fmt.Errorf("unknown key")
+	}
+
+	// Resolve the username so the session handler can use it for permission checks.
+	var user models.User
+	if found, _ := s.db.ID(sshKey.UserID).Get(&user); !found {
+		return nil, fmt.Errorf("user not found")
+	}
+
+	return &ssh.Permissions{
+		Extensions: map[string]string{
+			"username": user.Username,
+			"user_id":  fmt.Sprintf("%d", user.ID),
+		},
+	}, nil
+}
+
+func fingerprintMD5(pub ssh.PublicKey) string {
+	hash := md5.Sum(pub.Marshal())
+	parts := make([]string, len(hash))
+	for i, b := range hash {
+		parts[i] = fmt.Sprintf("%02x", b)
+	}
+	return strings.Join(parts, ":")
+}