cloudinit/config/validate/rules.go

/*
   Copyright 2014 CoreOS, Inc.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package validate

import (
	"fmt"
	"path"
	"reflect"
	"strings"

	"github.com/coreos/coreos-cloudinit/config"
)

type rule func(config node, report *Report)

// Rules contains all of the validation rules.
var Rules []rule = []rule{
	checkStructure,
	checkValidity,
	checkWriteFiles,
}

// checkStructure compares the provided config to the empty config.CloudConfig
// structure. Each node is checked to make sure that it exists in the known
// structure and that its type is compatible.
func checkStructure(cfg node, report *Report) {
	g := NewNode(config.CloudConfig{}, NewContext([]byte{}))
	checkNodeStructure(cfg, g, report)
}

func checkNodeStructure(n, g node, r *Report) {
	if !isCompatible(n.Kind(), g.Kind()) {
		r.Warning(n.line, fmt.Sprintf("incorrect type for %q (want %s)", n.name, g.HumanType()))
		return
	}

	switch g.Kind() {
	case reflect.Struct:
		for _, cn := range n.children {
			if cg := g.Child(cn.name); cg.IsValid() {
				checkNodeStructure(cn, cg, r)
			} else {
				r.Warning(cn.line, fmt.Sprintf("unrecognized key %q", cn.name))
			}
		}
	case reflect.Slice:
		for _, cn := range n.children {
			var cg node
			c := g.Type().Elem()
			toNode(reflect.New(c).Elem().Interface(), context{}, &cg)
			checkNodeStructure(cn, cg, r)
		}
	case reflect.String, reflect.Int, reflect.Float64, reflect.Bool:
	default:
		panic(fmt.Sprintf("checkNodeStructure(): unhandled kind %s", g.Kind()))
	}
}

// isCompatible determines if the type of kind n can be converted to the type
// of kind g in the context of YAML. This is not an exhaustive list, but its
// enough for the purposes of cloud-config validation.
func isCompatible(n, g reflect.Kind) bool {
	switch g {
	case reflect.String:
		return n == reflect.String || n == reflect.Int || n == reflect.Float64 || n == reflect.Bool
	case reflect.Struct:
		return n == reflect.Struct || n == reflect.Map
	case reflect.Float64:
		return n == reflect.Float64 || n == reflect.Int
	case reflect.Bool, reflect.Slice, reflect.Int:
		return n == g
	default:
		panic(fmt.Sprintf("isCompatible(): unhandled kind %s", g))
	}
}

// checkValidity checks the value of every node in the provided config by
// running config.AssertValid() on it.
func checkValidity(cfg node, report *Report) {
	g := NewNode(config.CloudConfig{}, NewContext([]byte{}))
	checkNodeValidity(cfg, g, report)
}

func checkNodeValidity(n, g node, r *Report) {
	if err := config.AssertValid(n.Value, g.field.Tag.Get("valid")); err != nil {
		r.Error(n.line, fmt.Sprintf("invalid value %v", n.Value.Interface()))
	}
	switch g.Kind() {
	case reflect.Struct:
		for _, cn := range n.children {
			if cg := g.Child(cn.name); cg.IsValid() {
				checkNodeValidity(cn, cg, r)
			}
		}
	case reflect.Slice:
		for _, cn := range n.children {
			var cg node
			c := g.Type().Elem()
			toNode(reflect.New(c).Elem().Interface(), context{}, &cg)
			checkNodeValidity(cn, cg, r)
		}
	case reflect.String, reflect.Int, reflect.Float64, reflect.Bool:
	default:
		panic(fmt.Sprintf("checkNodeValidity(): unhandled kind %s", g.Kind()))
	}
}

// checkWriteFiles checks to make sure that the target file can actually be
// written. Note that this check is approximate (it only checks to see if the file
// is under /usr).
func checkWriteFiles(cfg node, report *Report) {
	for _, f := range cfg.Child("write_files").children {
		c := f.Child("path")
		if !c.IsValid() {
			continue
		}

		d := path.Dir(c.String())
		switch {
		case strings.HasPrefix(d, "/usr"):
			report.Error(c.line, "file cannot be written to a read-only filesystem")
		}
	}
}