fix: extend forgejo_auth_token table

- Add a `purpose` column, this allows the `forgejo_auth_token` table to
be used by other parts of Forgejo, while still enjoying the
no-compromise architecture.
- Remove the 'roll your own crypto' time limited code functions and
migrate them to the `forgejo_auth_token` table. This migration ensures
generated codes can only be used for their purpose and ensure they are
invalidated after their usage by deleting it from the database, this
also should help making auditing of the security code easier, as we're
no longer trying to stuff a lot of data into a HMAC construction.
-Helper functions are rewritten to ensure a safe-by-design approach to
these tokens.
- Add the `forgejo_auth_token` to dbconsistency doctor and add it to the
`deleteUser` function.
- TODO: Add cron job to delete expired authorization tokens.
- Unit and integration tests added.

models/user/user.go

@@ -7,7 +7,9 @@ package user
 
 import (
 	"context"
+	"crypto/subtle"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"net/mail"
 	"net/url"
@@ -318,15 +320,14 @@ func (u *User) OrganisationLink() string {
 	return setting.AppSubURL + "/org/" + url.PathEscape(u.Name)
 }
 
-// GenerateEmailActivateCode generates an activate code based on user information and given e-mail.
-func (u *User) GenerateEmailActivateCode(email string) string {
-	code := base.CreateTimeLimitCode(
-		fmt.Sprintf("%d%s%s%s%s", u.ID, email, u.LowerName, u.Passwd, u.Rands),
-		setting.Service.ActiveCodeLives, time.Now(), nil)
-
-	// Add tail hex username
-	code += hex.EncodeToString([]byte(u.LowerName))
-	return code
+// GenerateEmailAuthorizationCode generates an activation code based for the user for the specified purpose.
+// The standard expiry is ActiveCodeLives minutes.
+func (u *User) GenerateEmailAuthorizationCode(ctx context.Context, purpose auth.AuthorizationPurpose) (string, error) {
+	lookup, validator, err := auth.GenerateAuthToken(ctx, u.ID, timeutil.TimeStampNow().Add(int64(setting.Service.ActiveCodeLives)*60), purpose)
+	if err != nil {
+		return "", err
+	}
+	return lookup + ":" + validator, nil
 }
 
 // GetUserFollowers returns range of user's followers.
@@ -838,35 +839,50 @@ func countUsers(ctx context.Context, opts *CountUserFilter) int64 {
 	return count
 }
 
-// GetVerifyUser get user by verify code
-func GetVerifyUser(ctx context.Context, code string) (user *User) {
-	if len(code) <= base.TimeLimitCodeLength {
-		return nil
+// VerifyUserActiveCode verifies that the code is valid for the given purpose for this user.
+// If delete is specified, the token will be deleted.
+func VerifyUserAuthorizationToken(ctx context.Context, code string, purpose auth.AuthorizationPurpose, delete bool) (*User, error) {
+	lookupKey, validator, found := strings.Cut(code, ":")
+	if !found {
+		return nil, nil
 	}
 
-	// use tail hex username query user
-	hexStr := code[base.TimeLimitCodeLength:]
-	if b, err := hex.DecodeString(hexStr); err == nil {
-		if user, err = GetUserByName(ctx, string(b)); user != nil {
-			return user
+	authToken, err := auth.FindAuthToken(ctx, lookupKey, purpose)
+	if err != nil {
+		if errors.Is(err, util.ErrNotExist) {
+			return nil, nil
 		}
-		log.Error("user.getVerifyUser: %v", err)
+		return nil, err
 	}
 
-	return nil
-}
+	if authToken.IsExpired() {
+		return nil, auth.DeleteAuthToken(ctx, authToken)
+	}
 
-// VerifyUserActiveCode verifies active code when active account
-func VerifyUserActiveCode(ctx context.Context, code string) (user *User) {
-	if user = GetVerifyUser(ctx, code); user != nil {
-		// time limit code
-		prefix := code[:base.TimeLimitCodeLength]
-		data := fmt.Sprintf("%d%s%s%s%s", user.ID, user.Email, user.LowerName, user.Passwd, user.Rands)
-		if base.VerifyTimeLimitCode(time.Now(), data, setting.Service.ActiveCodeLives, prefix) {
-			return user
+	rawValidator, err := hex.DecodeString(validator)
+	if err != nil {
+		return nil, err
+	}
+
+	if subtle.ConstantTimeCompare([]byte(authToken.HashedValidator), []byte(auth.HashValidator(rawValidator))) == 0 {
+		return nil, errors.New("validator doesn't match")
+	}
+
+	u, err := GetUserByID(ctx, authToken.UID)
+	if err != nil {
+		if IsErrUserNotExist(err) {
+			return nil, nil
+		}
+		return nil, err
+	}
+
+	if delete {
+		if err := auth.DeleteAuthToken(ctx, authToken); err != nil {
+			return nil, err
 		}
 	}
-	return nil
+
+	return u, nil
 }
 
 // ValidateUser check if user is valid to insert / update into database