Fix SSH zero address OTP delete (#6390)

* Fix SSH zero address OTP delete

Fixed bug where SSH OTP roles could not be deleted if a zero-address role
previously existed, and there currently exist no zero-address roles.

Fixes #6382

* Eliminate zeroAddressRoles remove function

builtin/logical/ssh/path_config_zeroaddress.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/hashicorp/vault/helper/strutil"
+
 	"github.com/hashicorp/vault/logical"
 	"github.com/hashicorp/vault/logical/framework"
 )
@@ -125,44 +127,11 @@ func (b *backend) removeZeroAddressRole(ctx context.Context, s logical.Storage,
 		return nil
 	}
 
-	err = zeroAddressEntry.remove(roleName)
-	if err != nil {
-		return err
-	}
+	zeroAddressEntry.Roles = strutil.StrListDelete(zeroAddressEntry.Roles, roleName)
 
 	return b.putZeroAddressRoles(ctx, s, zeroAddressEntry.Roles)
 }
 
-// Removes a given role from the comma separated string
-func (r *zeroAddressRoles) remove(roleName string) error {
-	var index int
-	for i, role := range r.Roles {
-		if role == roleName {
-			index = i
-			break
-		}
-	}
-	length := len(r.Roles)
-	if index >= length || index < 0 {
-		return fmt.Errorf("invalid index %d", index)
-	}
-	// If slice has zero or one item, remove the item by setting slice to nil.
-	if length < 2 {
-		r.Roles = nil
-		return nil
-	}
-
-	// Last item to be deleted
-	if length-1 == index {
-		r.Roles = r.Roles[:length-1]
-		return nil
-	}
-
-	// Delete the item by appending all items except the one at index
-	r.Roles = append(r.Roles[:index], r.Roles[index+1:]...)
-	return nil
-}
-
 const pathConfigZeroAddressSyn = `
 Assign zero address as default CIDR block for select roles.
 `