Split code into modules

This is a massive commit that restructures the code into modules:

db/
    All functions related to modifying the Database

types/
    All type definitions and methods that can be exclusivly used on
    these types without dependencies

policy/
    All Policy related code, now without dependencies on the Database.

policy/matcher/
    Dedicated code to match machines in a list of FilterRules

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

hscontrol/db/api_key.go

@@ -0,0 +1,125 @@
+package db
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/juanfont/headscale/hscontrol/types"
+	"github.com/juanfont/headscale/hscontrol/util"
+	"golang.org/x/crypto/bcrypt"
+)
+
+const (
+	apiPrefixLength = 7
+	apiKeyLength    = 32
+)
+
+var ErrAPIKeyFailedToParse = errors.New("failed to parse ApiKey")
+
+// CreateAPIKey creates a new ApiKey in a user, and returns it.
+func (hsdb *HSDatabase) CreateAPIKey(
+	expiration *time.Time,
+) (string, *types.APIKey, error) {
+	prefix, err := util.GenerateRandomStringURLSafe(apiPrefixLength)
+	if err != nil {
+		return "", nil, err
+	}
+
+	toBeHashed, err := util.GenerateRandomStringURLSafe(apiKeyLength)
+	if err != nil {
+		return "", nil, err
+	}
+
+	// Key to return to user, this will only be visible _once_
+	keyStr := prefix + "." + toBeHashed
+
+	hash, err := bcrypt.GenerateFromPassword([]byte(toBeHashed), bcrypt.DefaultCost)
+	if err != nil {
+		return "", nil, err
+	}
+
+	key := types.APIKey{
+		Prefix:     prefix,
+		Hash:       hash,
+		Expiration: expiration,
+	}
+
+	if err := hsdb.db.Save(&key).Error; err != nil {
+		return "", nil, fmt.Errorf("failed to save API key to database: %w", err)
+	}
+
+	return keyStr, &key, nil
+}
+
+// ListAPIKeys returns the list of ApiKeys for a user.
+func (hsdb *HSDatabase) ListAPIKeys() ([]types.APIKey, error) {
+	keys := []types.APIKey{}
+	if err := hsdb.db.Find(&keys).Error; err != nil {
+		return nil, err
+	}
+
+	return keys, nil
+}
+
+// GetAPIKey returns a ApiKey for a given key.
+func (hsdb *HSDatabase) GetAPIKey(prefix string) (*types.APIKey, error) {
+	key := types.APIKey{}
+	if result := hsdb.db.First(&key, "prefix = ?", prefix); result.Error != nil {
+		return nil, result.Error
+	}
+
+	return &key, nil
+}
+
+// GetAPIKeyByID returns a ApiKey for a given id.
+func (hsdb *HSDatabase) GetAPIKeyByID(id uint64) (*types.APIKey, error) {
+	key := types.APIKey{}
+	if result := hsdb.db.Find(&types.APIKey{ID: id}).First(&key); result.Error != nil {
+		return nil, result.Error
+	}
+
+	return &key, nil
+}
+
+// DestroyAPIKey destroys a ApiKey. Returns error if the ApiKey
+// does not exist.
+func (hsdb *HSDatabase) DestroyAPIKey(key types.APIKey) error {
+	if result := hsdb.db.Unscoped().Delete(key); result.Error != nil {
+		return result.Error
+	}
+
+	return nil
+}
+
+// ExpireAPIKey marks a ApiKey as expired.
+func (hsdb *HSDatabase) ExpireAPIKey(key *types.APIKey) error {
+	if err := hsdb.db.Model(&key).Update("Expiration", time.Now()).Error; err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (hsdb *HSDatabase) ValidateAPIKey(keyStr string) (bool, error) {
+	prefix, hash, found := strings.Cut(keyStr, ".")
+	if !found {
+		return false, ErrAPIKeyFailedToParse
+	}
+
+	key, err := hsdb.GetAPIKey(prefix)
+	if err != nil {
+		return false, fmt.Errorf("failed to validate api key: %w", err)
+	}
+
+	if key.Expiration.Before(time.Now()) {
+		return false, nil
+	}
+
+	if err := bcrypt.CompareHashAndPassword(key.Hash, []byte(hash)); err != nil {
+		return false, err
+	}
+
+	return true, nil
+}