/
bucket-sse-config.go
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/
bucket-sse-config.go
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// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package sse
import (
"encoding/xml"
"errors"
"io"
"net/http"
"strings"
"github.com/minio/minio/internal/crypto"
xhttp "github.com/minio/minio/internal/http"
)
const (
// AES256 is used with SSE-S3
AES256 Algorithm = "AES256"
// AWSKms is used with SSE-KMS
AWSKms Algorithm = "aws:kms"
)
// Algorithm - represents valid SSE algorithms supported; currently only AES256 is supported
type Algorithm string
// UnmarshalXML - Unmarshals XML tag to valid SSE algorithm
func (alg *Algorithm) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
var s string
if err := d.DecodeElement(&s, &start); err != nil {
return err
}
switch s {
case string(AES256):
*alg = AES256
case string(AWSKms):
*alg = AWSKms
default:
return errors.New("Unknown SSE algorithm")
}
return nil
}
// MarshalXML - Marshals given SSE algorithm to valid XML
func (alg *Algorithm) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
return e.EncodeElement(string(*alg), start)
}
// EncryptionAction - for ApplyServerSideEncryptionByDefault XML tag
type EncryptionAction struct {
Algorithm Algorithm `xml:"SSEAlgorithm,omitempty"`
MasterKeyID string `xml:"KMSMasterKeyID,omitempty"`
}
// Rule - for ServerSideEncryptionConfiguration XML tag
type Rule struct {
DefaultEncryptionAction EncryptionAction `xml:"ApplyServerSideEncryptionByDefault"`
}
const xmlNS = "http://s3.amazonaws.com/doc/2006-03-01/"
// BucketSSEConfig - represents default bucket encryption configuration
type BucketSSEConfig struct {
XMLNS string `xml:"xmlns,attr,omitempty"`
XMLName xml.Name `xml:"ServerSideEncryptionConfiguration"`
Rules []Rule `xml:"Rule"`
}
// ParseBucketSSEConfig - Decodes given XML to a valid default bucket encryption config
func ParseBucketSSEConfig(r io.Reader) (*BucketSSEConfig, error) {
var config BucketSSEConfig
err := xml.NewDecoder(r).Decode(&config)
if err != nil {
return nil, err
}
// Validates server-side encryption config rules
// Only one rule is allowed on AWS S3
if len(config.Rules) != 1 {
return nil, errors.New("only one server-side encryption rule is allowed at a time")
}
for _, rule := range config.Rules {
switch rule.DefaultEncryptionAction.Algorithm {
case AES256:
if rule.DefaultEncryptionAction.MasterKeyID != "" {
return nil, errors.New("MasterKeyID is allowed with aws:kms only")
}
case AWSKms:
keyID := rule.DefaultEncryptionAction.MasterKeyID
if keyID == "" {
return nil, errors.New("MasterKeyID is missing with aws:kms")
}
spaces := strings.HasPrefix(keyID, " ") || strings.HasSuffix(keyID, " ")
if spaces {
return nil, errors.New("MasterKeyID contains unsupported characters")
}
}
}
if config.XMLNS == "" {
config.XMLNS = xmlNS
}
return &config, nil
}
// ApplyOptions ask for specific features to be enabled,
// when bucketSSEConfig is empty.
type ApplyOptions struct {
AutoEncrypt bool
}
// Apply applies the SSE bucket configuration on the given HTTP headers and
// sets the specified SSE headers.
//
// Apply does not overwrite any existing SSE headers. Further, it will
// set minimal SSE-KMS headers if autoEncrypt is true and the BucketSSEConfig
// is nil.
func (b *BucketSSEConfig) Apply(headers http.Header, opts ApplyOptions) {
if crypto.Requested(headers) {
return
}
if b == nil {
if opts.AutoEncrypt {
headers.Set(xhttp.AmzServerSideEncryption, xhttp.AmzEncryptionKMS)
}
return
}
switch b.Algo() {
case xhttp.AmzEncryptionAES:
headers.Set(xhttp.AmzServerSideEncryption, xhttp.AmzEncryptionAES)
case xhttp.AmzEncryptionKMS:
headers.Set(xhttp.AmzServerSideEncryption, xhttp.AmzEncryptionKMS)
headers.Set(xhttp.AmzServerSideEncryptionKmsID, b.KeyID())
}
}
// Algo returns the SSE algorithm specified by the SSE configuration.
func (b *BucketSSEConfig) Algo() Algorithm {
for _, rule := range b.Rules {
return rule.DefaultEncryptionAction.Algorithm
}
return ""
}
// KeyID returns the KMS key ID specified by the SSE configuration.
// If the SSE configuration does not specify SSE-KMS it returns an
// empty key ID.
func (b *BucketSSEConfig) KeyID() string {
for _, rule := range b.Rules {
return strings.TrimPrefix(rule.DefaultEncryptionAction.MasterKeyID, crypto.ARNPrefix)
}
return ""
}