/
mime.go
100 lines (82 loc) · 2.41 KB
/
mime.go
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/*
Copyright 2020 The Kubernetes Authors.
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 mime
import (
"bytes"
"fmt"
"html/template"
"mime/multipart"
"net/textproto"
"strings"
)
const (
includePart = "file:///etc/secret-userdata.txt\n"
)
var (
includeType = textproto.MIMEHeader{
"content-type": {"text/x-include-url"},
}
boothookType = textproto.MIMEHeader{
"content-type": {"text/cloud-boothook"},
}
multipartHeader = strings.Join([]string{
"MIME-Version: 1.0",
"Content-Type: multipart/mixed; boundary=\"%s\"",
"\n",
}, "\n")
)
type scriptVariables struct {
SecretPrefix string
Chunks int32
Region string
Endpoint string
}
// GenerateInitDocument renders a given template, applies MIME properties
// and returns a series of byte chunks which put together represent a UserData
// script
func GenerateInitDocument(secretPrefix string, chunks int32, region string, endpoint string, secretFetchScript string) ([]byte, error) {
var secretFetchTemplate = template.Must(template.New("secret-fetch-script").Parse(secretFetchScript))
var buf bytes.Buffer
mpWriter := multipart.NewWriter(&buf)
buf.WriteString(fmt.Sprintf(multipartHeader, mpWriter.Boundary()))
scriptWriter, err := mpWriter.CreatePart(boothookType)
if err != nil {
return []byte{}, err
}
scriptVariables := scriptVariables{
SecretPrefix: secretPrefix,
Chunks: chunks,
Region: region,
Endpoint: endpoint,
}
var scriptBuf bytes.Buffer
if err := secretFetchTemplate.Execute(&scriptBuf, scriptVariables); err != nil {
return []byte{}, err
}
_, err = scriptWriter.Write(scriptBuf.Bytes())
if err != nil {
return []byte{}, err
}
includeWriter, err := mpWriter.CreatePart(includeType)
if err != nil {
return []byte{}, err
}
_, err = includeWriter.Write([]byte(includePart))
if err != nil {
return []byte{}, err
}
if err := mpWriter.Close(); err != nil {
return []byte{}, err
}
return buf.Bytes(), nil
}