sigs.k8s.io/cluster-api-provider-aws@v1.5.5/pkg/internal/mime/mime.go (about)

     1  /*
     2  Copyright 2020 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8  	http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package mime
    18  
    19  import (
    20  	"bytes"
    21  	"fmt"
    22  	"html/template"
    23  	"mime/multipart"
    24  	"net/textproto"
    25  	"strings"
    26  )
    27  
    28  const (
    29  	includePart = "file:///etc/secret-userdata.txt\n"
    30  )
    31  
    32  var (
    33  	includeType = textproto.MIMEHeader{
    34  		"content-type": {"text/x-include-url"},
    35  	}
    36  
    37  	boothookType = textproto.MIMEHeader{
    38  		"content-type": {"text/cloud-boothook"},
    39  	}
    40  
    41  	multipartHeader = strings.Join([]string{
    42  		"MIME-Version: 1.0",
    43  		"Content-Type: multipart/mixed; boundary=\"%s\"",
    44  		"\n",
    45  	}, "\n")
    46  )
    47  
    48  type scriptVariables struct {
    49  	SecretPrefix string
    50  	Chunks       int32
    51  	Region       string
    52  	Endpoint     string
    53  }
    54  
    55  // GenerateInitDocument renders a given template, applies MIME properties
    56  // and returns a series of byte chunks which put together represent a UserData
    57  // script.
    58  func GenerateInitDocument(secretPrefix string, chunks int32, region string, endpoint string, secretFetchScript string) ([]byte, error) {
    59  	var secretFetchTemplate = template.Must(template.New("secret-fetch-script").Parse(secretFetchScript))
    60  
    61  	var buf bytes.Buffer
    62  	mpWriter := multipart.NewWriter(&buf)
    63  	buf.WriteString(fmt.Sprintf(multipartHeader, mpWriter.Boundary()))
    64  	scriptWriter, err := mpWriter.CreatePart(boothookType)
    65  	if err != nil {
    66  		return []byte{}, err
    67  	}
    68  
    69  	scriptVariables := scriptVariables{
    70  		SecretPrefix: secretPrefix,
    71  		Chunks:       chunks,
    72  		Region:       region,
    73  		Endpoint:     endpoint,
    74  	}
    75  
    76  	var scriptBuf bytes.Buffer
    77  	if err := secretFetchTemplate.Execute(&scriptBuf, scriptVariables); err != nil {
    78  		return []byte{}, err
    79  	}
    80  	_, err = scriptWriter.Write(scriptBuf.Bytes())
    81  	if err != nil {
    82  		return []byte{}, err
    83  	}
    84  
    85  	includeWriter, err := mpWriter.CreatePart(includeType)
    86  	if err != nil {
    87  		return []byte{}, err
    88  	}
    89  
    90  	_, err = includeWriter.Write([]byte(includePart))
    91  	if err != nil {
    92  		return []byte{}, err
    93  	}
    94  
    95  	if err := mpWriter.Close(); err != nil {
    96  		return []byte{}, err
    97  	}
    98  
    99  	return buf.Bytes(), nil
   100  }