b2: Add Server-Side encryption support

This commit adds SSE-C (Server-Side Encryption - Customer) support to
the B2 native backend. The server uses a customer provided AES-256 key
to encrypt the files when you upload them to the bucket, and then it
discards your key from the servers RAM after you're done uploading.

The option names and descriptions are based off the S3 backend
implementation as the way S3 and B2 does SSE-C is pretty similar.

Fixes #6585

backend/b2/api/types.go

@@ -48,6 +48,14 @@ type LifecycleRule struct {
 	FileNamePrefix                                  string `json:"fileNamePrefix"`
 }
 
+// ServerSideEncryption is a configuration object for B2 Server-Side Encryption
+type ServerSideEncryption struct {
+	Mode           string `json:"mode"`
+	Algorithm      string `json:"algorithm"`      // Encryption algorith to use
+	CustomerKey    string `json:"customerKey"`    // User provided Base64 encoded key that is used by the server to encrypt files
+	CustomerKeyMd5 string `json:"customerKeyMd5"` // An MD5 hash of the decoded key
+}
+
 // Timestamp is a UTC time when this file was uploaded. It is a base
 // 10 number of milliseconds since midnight, January 1, 1970 UTC. This
 // fits in a 64 bit integer such as the type "long" in the programming
@@ -261,10 +269,11 @@ type GetFileInfoRequest struct {
 //
 // Example: { "src_last_modified_millis" : "1452802803026", "large_file_sha1" : "a3195dc1e7b46a2ff5da4b3c179175b75671e80d", "color": "blue" }
 type StartLargeFileRequest struct {
-	BucketID    string            `json:"bucketId"`    //The ID of the bucket that the file will go in.
+	BucketID             string               `json:"bucketId"`                       // The ID of the bucket that the file will go in.
 	Name                 string               `json:"fileName"`                       // The name of the file. See Files for requirements on file names.
 	ContentType          string               `json:"contentType"`                    // The MIME type of the content of the file, which will be returned in the Content-Type header when downloading the file. Use the Content-Type b2/x-auto to automatically set the stored Content-Type post upload. In the case where a file extension is absent or the lookup fails, the Content-Type is set to application/octet-stream.
 	Info                 map[string]string    `json:"fileInfo"`                       // A JSON object holding the name/value pairs for the custom file info.
+	ServerSideEncryption ServerSideEncryption `json:"serverSideEncryption,omitempty"` // A JSON object holding values related to Server-Side Encryption
 }
 
 // StartLargeFileResponse is the response to StartLargeFileRequest
@@ -275,7 +284,7 @@ type StartLargeFileResponse struct {
 	BucketID        string            `json:"bucketId"`                  // The unique ID of the bucket.
 	ContentType     string            `json:"contentType"`               // The MIME type of the file.
 	Info            map[string]string `json:"fileInfo"`                  // The custom information that was uploaded with the file. This is a JSON object, holding the name/value pairs that were uploaded with the file.
-	UploadTimestamp Timestamp         `json:"uploadTimestamp"` // This is a UTC time when this file was uploaded.
+	UploadTimestamp Timestamp         `json:"uploadTimestamp,omitempty"` // This is a UTC time when this file was uploaded.
 }
 
 // GetUploadPartURLRequest is passed to b2_get_upload_part_url
@@ -332,6 +341,8 @@ type CopyFileRequest struct {
 	ContentType                     string               `json:"contentType,omitempty"`                     // The MIME type of the content of the file (REPLACE only)
 	Info                            map[string]string    `json:"fileInfo,omitempty"`                        // This field stores the metadata that will be stored with the file. (REPLACE only)
 	DestBucketID                    string               `json:"destinationBucketId,omitempty"`             // The destination ID of the bucket if set, if not the source bucket will be used
+	SourceServerSideEncryption      ServerSideEncryption `json:"sourceServerSideEncryption,omitempty"`      // A JSON object holding values related to Server-Side Encryption for the source file
+	DestinationServerSideEncryption ServerSideEncryption `json:"destinationServerSideEncryption,omitempty"` // A JSON object holding values related to Server-Side Encryption for the destination file
 }
 
 // CopyPartRequest is the request for b2_copy_part - the response is UploadPartResponse
@@ -340,6 +351,8 @@ type CopyPartRequest struct {
 	LargeFileID                     string               `json:"largeFileId"`                               // The ID of the large file the part will belong to, as returned by b2_start_large_file.
 	PartNumber                      int64                `json:"partNumber"`                                // Which part this is (starting from 1)
 	Range                           string               `json:"range,omitempty"`                           // The range of bytes to copy. If not provided, the whole source file will be copied.
+	SourceServerSideEncryption      ServerSideEncryption `json:"sourceServerSideEncryption,omitempty"`      // A JSON object holding values related to Server-Side Encryption for the source file
+	DestinationServerSideEncryption ServerSideEncryption `json:"destinationServerSideEncryption,omitempty"` // A JSON object holding values related to Server-Side Encryption for the destination file
 }
 
 // UpdateBucketRequest describes a request to modify a B2 bucket

backend/b2/b2.go

@@ -8,7 +8,9 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"crypto/md5"
 	"crypto/sha1"
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -53,6 +55,9 @@ const (
 	nameHeader          = "X-Bz-File-Name"
 	timestampHeader     = "X-Bz-Upload-Timestamp"
 	retryAfterHeader    = "Retry-After"
+	sseAlgorithmHeader  = "X-Bz-Server-Side-Encryption-Customer-Algorithm"
+	sseKeyHeader        = "X-Bz-Server-Side-Encryption-Customer-Key"
+	sseMd5Header        = "X-Bz-Server-Side-Encryption-Customer-Key-Md5"
 	minSleep            = 10 * time.Millisecond
 	maxSleep            = 5 * time.Minute
 	decayConstant       = 1 // bigger for slower decay, exponential
@@ -252,6 +257,51 @@ See: [rclone backend lifecycle](#lifecycle) for setting lifecycles after bucket
 			Default: (encoder.Display |
 				encoder.EncodeBackSlash |
 				encoder.EncodeInvalidUtf8),
+		}, {
+			Name:     "sse_customer_algorithm",
+			Help:     "If using SSE-C, the server-side encryption algorithm used when storing this object in B2.",
+			Advanced: true,
+			Examples: []fs.OptionExample{{
+				Value: "",
+				Help:  "None",
+			}, {
+				Value: "AES256",
+				Help:  "Advanced Encryption Standard (256 bits key length)",
+			}},
+		}, {
+			Name: "sse_customer_key",
+			Help: `To use SSE-C, you may provide the secret encryption key encoded in a UTF-8 compatible string to encrypt/decrypt your data
+
+Alternatively you can provide --sse-customer-key-base64.`,
+			Advanced: true,
+			Examples: []fs.OptionExample{{
+				Value: "",
+				Help:  "None",
+			}},
+			Sensitive: true,
+		}, {
+			Name: "sse_customer_key_base64",
+			Help: `To use SSE-C, you may provide the secret encryption key encoded in Base64 format to encrypt/decrypt your data
+
+Alternatively you can provide --sse-customer-key.`,
+			Advanced: true,
+			Examples: []fs.OptionExample{{
+				Value: "",
+				Help:  "None",
+			}},
+			Sensitive: true,
+		}, {
+			Name: "sse_customer_key_md5",
+			Help: `If using SSE-C you may provide the secret encryption key MD5 checksum (optional).
+
+If you leave it blank, this is calculated automatically from the sse_customer_key provided.
+`,
+			Advanced: true,
+			Examples: []fs.OptionExample{{
+				Value: "",
+				Help:  "None",
+			}},
+			Sensitive: true,
 		}},
 	})
 }
@@ -274,6 +324,10 @@ type Options struct {
 	DownloadAuthorizationDuration fs.Duration          `config:"download_auth_duration"`
 	Lifecycle                     int                  `config:"lifecycle"`
 	Enc                           encoder.MultiEncoder `config:"encoding"`
+	SSECustomerAlgorithm          string               `config:"sse_customer_algorithm"`
+	SSECustomerKey                string               `config:"sse_customer_key"`
+	SSECustomerKeyBase64          string               `config:"sse_customer_key_base64"`
+	SSECustomerKeyMD5             string               `config:"sse_customer_key_md5"`
 }
 
 // Fs represents a remote b2 server
@@ -504,6 +558,24 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 	if opt.Endpoint == "" {
 		opt.Endpoint = defaultEndpoint
 	}
+	if opt.SSECustomerKey != "" && opt.SSECustomerKeyBase64 != "" {
+		return nil, errors.New("b2: can't use both sse_customer_key and sse_customer_key_base64 at the same time")
+	} else if opt.SSECustomerKeyBase64 != "" {
+		// Decode the Base64-encoded key and store it in the SSECustomerKey field
+		decoded, err := base64.StdEncoding.DecodeString(opt.SSECustomerKeyBase64)
+		if err != nil {
+			return nil, fmt.Errorf("b2: Could not decode sse_customer_key_base64: %w", err)
+		}
+		opt.SSECustomerKey = string(decoded)
+	} else {
+		// Encode the raw key as Base64
+		opt.SSECustomerKeyBase64 = base64.StdEncoding.EncodeToString([]byte(opt.SSECustomerKey))
+	}
+	if opt.SSECustomerKey != "" && opt.SSECustomerKeyMD5 == "" {
+		// Calculate CustomerKeyMd5 if not supplied
+		md5sumBinary := md5.Sum([]byte(opt.SSECustomerKey))
+		opt.SSECustomerKeyMD5 = base64.StdEncoding.EncodeToString(md5sumBinary[:])
+	}
 	ci := fs.GetConfig(ctx)
 	f := &Fs{
 		name:        name,
@@ -1435,6 +1507,16 @@ func (f *Fs) copy(ctx context.Context, dstObj *Object, srcObj *Object, newInfo *
 		Name:         f.opt.Enc.FromStandardPath(dstPath),
 		DestBucketID: destBucketID,
 	}
+	if f.opt.SSECustomerKey != "" && f.opt.SSECustomerKeyMD5 != "" {
+		serverSideEncryptionConfig := api.ServerSideEncryption{
+			Mode:           "SSE-C",
+			Algorithm:      f.opt.SSECustomerAlgorithm,
+			CustomerKey:    f.opt.SSECustomerKeyBase64,
+			CustomerKeyMd5: f.opt.SSECustomerKeyMD5,
+		}
+		request.SourceServerSideEncryption = serverSideEncryptionConfig
+		request.DestinationServerSideEncryption = serverSideEncryptionConfig
+	}
 	if newInfo == nil {
 		request.MetadataDirective = "COPY"
 	} else {
@@ -1869,6 +1951,7 @@ func (o *Object) getOrHead(ctx context.Context, method string, options []fs.Open
 		Method:       method,
 		Options:      options,
 		NoResponse:   method == "HEAD",
+		ExtraHeaders: map[string]string{},
 	}
 
 	// Use downloadUrl from backblaze if downloadUrl is not set
@@ -1886,6 +1969,11 @@ func (o *Object) getOrHead(ctx context.Context, method string, options []fs.Open
 		bucket, bucketPath := o.split()
 		opts.Path += "/file/" + urlEncode(o.fs.opt.Enc.FromStandardName(bucket)) + "/" + urlEncode(o.fs.opt.Enc.FromStandardPath(bucketPath))
 	}
+	if o.fs.opt.SSECustomerKey != "" && o.fs.opt.SSECustomerKeyMD5 != "" {
+		opts.ExtraHeaders[sseAlgorithmHeader] = o.fs.opt.SSECustomerAlgorithm
+		opts.ExtraHeaders[sseKeyHeader] = o.fs.opt.SSECustomerKeyBase64
+		opts.ExtraHeaders[sseMd5Header] = o.fs.opt.SSECustomerKeyMD5
+	}
 	err = o.fs.pacer.Call(func() (bool, error) {
 		resp, err = o.fs.srv.Call(ctx, &opts)
 		return o.fs.shouldRetry(ctx, resp, err)
@@ -2150,6 +2238,11 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 		},
 		ContentLength: &size,
 	}
+	if o.fs.opt.SSECustomerKey != "" && o.fs.opt.SSECustomerKeyMD5 != "" {
+		opts.ExtraHeaders[sseAlgorithmHeader] = o.fs.opt.SSECustomerAlgorithm
+		opts.ExtraHeaders[sseKeyHeader] = o.fs.opt.SSECustomerKeyBase64
+		opts.ExtraHeaders[sseMd5Header] = o.fs.opt.SSECustomerKeyMD5
+	}
 	var response api.FileInfo
 	// Don't retry, return a retry error instead
 	err = o.fs.pacer.CallNoRetry(func() (bool, error) {

backend/b2/upload.go

@@ -144,6 +144,14 @@ func (f *Fs) newLargeUpload(ctx context.Context, o *Object, in io.Reader, src fs
 		request.ContentType = newInfo.ContentType
 		request.Info = newInfo.Info
 	}
+	if o.fs.opt.SSECustomerKey != "" && o.fs.opt.SSECustomerKeyMD5 != "" {
+		request.ServerSideEncryption = api.ServerSideEncryption{
+			Mode:           "SSE-C",
+			Algorithm:      o.fs.opt.SSECustomerAlgorithm,
+			CustomerKey:    o.fs.opt.SSECustomerKeyBase64,
+			CustomerKeyMd5: o.fs.opt.SSECustomerKeyMD5,
+		}
+	}
 	opts := rest.Opts{
 		Method:  "POST",
 		Path:    "/b2_start_large_file",
@@ -295,6 +303,12 @@ func (up *largeUpload) WriteChunk(ctx context.Context, chunkNumber int, reader i
 			ContentLength: &sizeWithHash,
 		}
 
+		if up.o.fs.opt.SSECustomerKey != "" && up.o.fs.opt.SSECustomerKeyMD5 != "" {
+			opts.ExtraHeaders[sseAlgorithmHeader] = up.o.fs.opt.SSECustomerAlgorithm
+			opts.ExtraHeaders[sseKeyHeader] = up.o.fs.opt.SSECustomerKeyBase64
+			opts.ExtraHeaders[sseMd5Header] = up.o.fs.opt.SSECustomerKeyMD5
+		}
+
 		var response api.UploadPartResponse
 
 		resp, err := up.f.srv.CallJSON(ctx, &opts, nil, &response)
@@ -334,6 +348,17 @@ func (up *largeUpload) copyChunk(ctx context.Context, part int, partSize int64)
 			PartNumber:  int64(part + 1),
 			Range:       fmt.Sprintf("bytes=%d-%d", offset, offset+partSize-1),
 		}
+
+		if up.o.fs.opt.SSECustomerKey != "" && up.o.fs.opt.SSECustomerKeyMD5 != "" {
+			serverSideEncryptionConfig := api.ServerSideEncryption{
+				Mode:           "SSE-C",
+				Algorithm:      up.o.fs.opt.SSECustomerAlgorithm,
+				CustomerKey:    up.o.fs.opt.SSECustomerKeyBase64,
+				CustomerKeyMd5: up.o.fs.opt.SSECustomerKeyMD5,
+			}
+			request.SourceServerSideEncryption = serverSideEncryptionConfig
+			request.DestinationServerSideEncryption = serverSideEncryptionConfig
+		}
 		var response api.UploadPartResponse
 		resp, err := up.f.srv.CallJSON(ctx, &opts, &request, &response)
 		retry, err := up.f.shouldRetry(ctx, resp, err)