Add support for server side bucket replication (#9882)

pkg/bucket/policy/action.go

@@ -149,28 +149,49 @@ const (
 
 	// PutObjectVersionTaggingAction - PutObjectVersionTagging Rest API action.
 	PutObjectVersionTaggingAction = "s3:PutObjectVersionTagging"
+
+	// GetReplicationConfigurationAction  - GetReplicationConfiguration REST API action
+	GetReplicationConfigurationAction = "s3:GetReplicationConfiguration"
+	// PutReplicationConfigurationAction  - PutReplicationConfiguration REST API action
+	PutReplicationConfigurationAction = "s3:PutReplicationConfiguration"
+
+	// ReplicateObjectAction  - ReplicateObject REST API action
+	ReplicateObjectAction = "s3:ReplicateObject"
+
+	// ReplicateDeleteAction  - ReplicateDelete REST API action
+	ReplicateDeleteAction = "s3:ReplicateDelete"
+
+	// ReplicateTagsAction  - ReplicateTags REST API action
+	ReplicateTagsAction = "s3:ReplicateTags"
+
+	// GetObjectVersionForReplicationAction  - GetObjectVersionForReplication REST API action
+	GetObjectVersionForReplicationAction = "s3:GetObjectVersionForReplication"
 )
 
 // List of all supported object actions.
 var supportedObjectActions = map[Action]struct{}{
-	AbortMultipartUploadAction:       {},
-	DeleteObjectAction:               {},
-	GetObjectAction:                  {},
-	ListMultipartUploadPartsAction:   {},
-	PutObjectAction:                  {},
-	BypassGovernanceRetentionAction:  {},
-	PutObjectRetentionAction:         {},
-	GetObjectRetentionAction:         {},
-	PutObjectLegalHoldAction:         {},
-	GetObjectLegalHoldAction:         {},
-	GetObjectTaggingAction:           {},
-	PutObjectTaggingAction:           {},
-	DeleteObjectTaggingAction:        {},
-	GetObjectVersionAction:           {},
-	GetObjectVersionTaggingAction:    {},
-	DeleteObjectVersionAction:        {},
-	DeleteObjectVersionTaggingAction: {},
-	PutObjectVersionTaggingAction:    {},
+	AbortMultipartUploadAction:           {},
+	DeleteObjectAction:                   {},
+	GetObjectAction:                      {},
+	ListMultipartUploadPartsAction:       {},
+	PutObjectAction:                      {},
+	BypassGovernanceRetentionAction:      {},
+	PutObjectRetentionAction:             {},
+	GetObjectRetentionAction:             {},
+	PutObjectLegalHoldAction:             {},
+	GetObjectLegalHoldAction:             {},
+	GetObjectTaggingAction:               {},
+	PutObjectTaggingAction:               {},
+	DeleteObjectTaggingAction:            {},
+	GetObjectVersionAction:               {},
+	GetObjectVersionTaggingAction:        {},
+	DeleteObjectVersionAction:            {},
+	DeleteObjectVersionTaggingAction:     {},
+	PutObjectVersionTaggingAction:        {},
+	ReplicateObjectAction:                {},
+	ReplicateDeleteAction:                {},
+	ReplicateTagsAction:                  {},
+	GetObjectVersionForReplicationAction: {},
 }
 
 // isObjectAction - returns whether action is object type or not.
@@ -224,6 +245,12 @@ var supportedActions = map[Action]struct{}{
 	GetBucketEncryptionAction:              {},
 	PutBucketVersioningAction:              {},
 	GetBucketVersioningAction:              {},
+	GetReplicationConfigurationAction:      {},
+	PutReplicationConfigurationAction:      {},
+	ReplicateObjectAction:                  {},
+	ReplicateDeleteAction:                  {},
+	ReplicateTagsAction:                    {},
+	GetObjectVersionForReplicationAction:   {},
 }
 
 // IsValid - checks if action is valid or not.
@@ -366,4 +393,10 @@ var actionConditionKeyMap = map[Action]condition.KeySet{
 		append([]condition.Key{
 			condition.S3VersionID,
 		}, condition.CommonKeys...)...),
+	GetReplicationConfigurationAction:    condition.NewKeySet(condition.CommonKeys...),
+	PutReplicationConfigurationAction:    condition.NewKeySet(condition.CommonKeys...),
+	ReplicateObjectAction:                condition.NewKeySet(condition.CommonKeys...),
+	ReplicateDeleteAction:                condition.NewKeySet(condition.CommonKeys...),
+	ReplicateTagsAction:                  condition.NewKeySet(condition.CommonKeys...),
+	GetObjectVersionForReplicationAction: condition.NewKeySet(condition.CommonKeys...),
 }

pkg/bucket/replication/and.go

@@ -0,0 +1,62 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, 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 replication
+
+import (
+	"encoding/xml"
+)
+
+// And - a tag to combine a prefix and multiple tags for replication configuration rule.
+type And struct {
+	XMLName xml.Name `xml:"And" json:"And"`
+	Prefix  string   `xml:"Prefix,omitempty" json:"Prefix,omitempty"`
+	Tags    []Tag    `xml:"Tag,omitempty" json:"Tag,omitempty"`
+}
+
+var errDuplicateTagKey = Errorf("Duplicate Tag Keys are not allowed")
+
+// isEmpty returns true if Tags field is null
+func (a And) isEmpty() bool {
+	return len(a.Tags) == 0 && a.Prefix == ""
+}
+
+// Validate - validates the And field
+func (a And) Validate() error {
+	if a.ContainsDuplicateTag() {
+		return errDuplicateTagKey
+	}
+	for _, t := range a.Tags {
+		if err := t.Validate(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// ContainsDuplicateTag - returns true if duplicate keys are present in And
+func (a And) ContainsDuplicateTag() bool {
+	x := make(map[string]struct{}, len(a.Tags))
+
+	for _, t := range a.Tags {
+		if _, has := x[t.Key]; has {
+			return true
+		}
+		x[t.Key] = struct{}{}
+	}
+
+	return false
+}

pkg/bucket/replication/destination.go

@@ -0,0 +1,118 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, 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 replication
+
+import (
+	"encoding/xml"
+	"fmt"
+	"strings"
+
+	"github.com/minio/minio/pkg/wildcard"
+)
+
+// DestinationARNPrefix - destination ARN prefix as per AWS S3 specification.
+const DestinationARNPrefix = "arn:aws:s3:::"
+
+// Destination - destination in ReplicationConfiguration.
+type Destination struct {
+	XMLName      xml.Name `xml:"Destination" json:"Destination"`
+	Bucket       string   `xml:"Bucket" json:"Bucket"`
+	StorageClass string   `xml:"StorageClass" json:"StorageClass"`
+	//EncryptionConfiguration TODO: not needed for MinIO
+}
+
+func (d Destination) isValidStorageClass() bool {
+	if d.StorageClass == "" {
+		return true
+	}
+	return d.StorageClass == "STANDARD" || d.StorageClass == "REDUCED_REDUNDANCY"
+}
+
+// IsValid - checks whether Destination is valid or not.
+func (d Destination) IsValid() bool {
+	return d.Bucket != "" || !d.isValidStorageClass()
+}
+
+func (d Destination) String() string {
+	return DestinationARNPrefix + d.Bucket
+}
+
+// MarshalXML - encodes to XML data.
+func (d Destination) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+	if err := e.EncodeElement(d.String(), xml.StartElement{Name: xml.Name{Local: "Bucket"}}); err != nil {
+		return err
+	}
+	if d.StorageClass != "" {
+		if err := e.EncodeElement(d.StorageClass, xml.StartElement{Name: xml.Name{Local: "StorageClass"}}); err != nil {
+			return err
+		}
+	}
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+}
+
+// UnmarshalXML - decodes XML data.
+func (d *Destination) UnmarshalXML(dec *xml.Decoder, start xml.StartElement) (err error) {
+	// Make subtype to avoid recursive UnmarshalXML().
+	type destination Destination
+	dest := destination{}
+
+	if err := dec.DecodeElement(&dest, &start); err != nil {
+		return err
+	}
+	parsedDest, err := parseDestination(dest.Bucket)
+	if err != nil {
+		return err
+	}
+	if dest.StorageClass != "" {
+		switch dest.StorageClass {
+		case "STANDARD", "REDUCED_REDUNDANCY":
+		default:
+			return fmt.Errorf("unknown storage class %v", dest.StorageClass)
+		}
+	}
+	parsedDest.StorageClass = dest.StorageClass
+	*d = parsedDest
+	return nil
+}
+
+// Validate - validates Resource is for given bucket or not.
+func (d Destination) Validate(bucketName string) error {
+	if !d.IsValid() {
+		return Errorf("invalid destination")
+	}
+
+	if !wildcard.Match(d.Bucket, bucketName) {
+		return Errorf("bucket name does not match")
+	}
+	return nil
+}
+
+// parseDestination - parses string to Destination.
+func parseDestination(s string) (Destination, error) {
+	if !strings.HasPrefix(s, DestinationARNPrefix) {
+		return Destination{}, Errorf("invalid destination '%v'", s)
+	}
+
+	bucketName := strings.TrimPrefix(s, DestinationARNPrefix)
+
+	return Destination{
+		Bucket: bucketName,
+	}, nil
+}

pkg/bucket/replication/error.go

@@ -0,0 +1,44 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, 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 replication
+
+import (
+	"fmt"
+)
+
+// Error is the generic type for any error happening during tag
+// parsing.
+type Error struct {
+	err error
+}
+
+// Errorf - formats according to a format specifier and returns
+// the string as a value that satisfies error of type tagging.Error
+func Errorf(format string, a ...interface{}) error {
+	return Error{err: fmt.Errorf(format, a...)}
+}
+
+// Unwrap the internal error.
+func (e Error) Unwrap() error { return e.err }
+
+// Error 'error' compatible method.
+func (e Error) Error() string {
+	if e.err == nil {
+		return "replication: cause <nil>"
+	}
+	return e.err.Error()
+}

pkg/bucket/replication/filter.go

@@ -0,0 +1,120 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, 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 replication
+
+import (
+	"encoding/xml"
+)
+
+var (
+	errInvalidFilter = Errorf("Filter must have exactly one of Prefix, Tag, or And specified")
+)
+
+// Filter - a filter for a replication configuration Rule.
+type Filter struct {
+	XMLName xml.Name `xml:"Filter" json:"Filter"`
+	Prefix  string
+	And     And
+	Tag     Tag
+	// Caching tags, only once
+	cachedTags map[string]struct{}
+}
+
+// IsEmpty returns true if filter is not set
+func (f Filter) IsEmpty() bool {
+	return f.And.isEmpty() && f.Tag.IsEmpty() && f.Prefix == ""
+}
+
+// MarshalXML - produces the xml representation of the Filter struct
+// only one of Prefix, And and Tag should be present in the output.
+func (f Filter) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	if err := e.EncodeToken(start); err != nil {
+		return err
+	}
+
+	switch {
+	case !f.And.isEmpty():
+		if err := e.EncodeElement(f.And, xml.StartElement{Name: xml.Name{Local: "And"}}); err != nil {
+			return err
+		}
+	case !f.Tag.IsEmpty():
+		if err := e.EncodeElement(f.Tag, xml.StartElement{Name: xml.Name{Local: "Tag"}}); err != nil {
+			return err
+		}
+	default:
+		// Always print Prefix field when both And & Tag are empty
+		if err := e.EncodeElement(f.Prefix, xml.StartElement{Name: xml.Name{Local: "Prefix"}}); err != nil {
+			return err
+		}
+	}
+
+	return e.EncodeToken(xml.EndElement{Name: start.Name})
+}
+
+// Validate - validates the filter element
+func (f Filter) Validate() error {
+	// A Filter must have exactly one of Prefix, Tag, or And specified.
+	if !f.And.isEmpty() {
+		if f.Prefix != "" {
+			return errInvalidFilter
+		}
+		if !f.Tag.IsEmpty() {
+			return errInvalidFilter
+		}
+		if err := f.And.Validate(); err != nil {
+			return err
+		}
+	}
+	if f.Prefix != "" {
+		if !f.Tag.IsEmpty() {
+			return errInvalidFilter
+		}
+	}
+	if !f.Tag.IsEmpty() {
+		if err := f.Tag.Validate(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// TestTags tests if the object tags satisfy the Filter tags requirement,
+// it returns true if there is no tags in the underlying Filter.
+func (f *Filter) TestTags(ttags []string) bool {
+	if f.cachedTags == nil {
+		tags := make(map[string]struct{})
+		for _, t := range append(f.And.Tags, f.Tag) {
+			if !t.IsEmpty() {
+				tags[t.String()] = struct{}{}
+			}
+		}
+		f.cachedTags = tags
+	}
+	for ct := range f.cachedTags {
+		foundTag := false
+		for _, t := range ttags {
+			if ct == t {
+				foundTag = true
+				break
+			}
+		}
+		if !foundTag {
+			return false
+		}
+	}
+	return true
+}

pkg/bucket/replication/replication.go

@@ -0,0 +1,206 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, 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 replication
+
+import (
+	"encoding/xml"
+	"io"
+	"sort"
+	"strings"
+)
+
+// StatusType of Replication for x-amz-replication-status header
+type StatusType string
+
+const (
+	// Pending - replication is pending.
+	Pending StatusType = "PENDING"
+
+	// Complete - replication completed ok.
+	Complete StatusType = "COMPLETE"
+
+	// Failed - replication failed.
+	Failed StatusType = "FAILED"
+
+	// Replica - this is a replica.
+	Replica StatusType = "REPLICA"
+)
+
+// String returns string representation of status
+func (s StatusType) String() string {
+	return string(s)
+}
+
+var (
+	errReplicationTooManyRules        = Errorf("Replication configuration allows a maximum of 1000 rules")
+	errReplicationNoRule              = Errorf("Replication configuration should have at least one rule")
+	errReplicationUniquePriority      = Errorf("Replication configuration has duplicate priority")
+	errReplicationDestinationMismatch = Errorf("The destination bucket must be same for all rules")
+	errReplicationArnMissing          = Errorf("Replication Arn missing")
+)
+
+// Config - replication configuration specified in
+// https://docs.aws.amazon.com/AmazonS3/latest/dev/replication-add-config.html
+type Config struct {
+	XMLName xml.Name `xml:"ReplicationConfiguration" json:"-"`
+	Rules   []Rule   `xml:"Rule" json:"Rules"`
+	// ReplicationArn is a MinIO only extension and optional for AWS
+	ReplicationArn string `xml:"ReplicationArn,omitempty" json:"ReplicationArn,omitempty"`
+}
+
+// Maximum 2MiB size per replication config.
+const maxReplicationConfigSize = 2 << 20
+
+// ParseConfig parses ReplicationConfiguration from xml
+func ParseConfig(reader io.Reader) (*Config, error) {
+	config := Config{}
+	if err := xml.NewDecoder(io.LimitReader(reader, maxReplicationConfigSize)).Decode(&config); err != nil {
+		return nil, err
+	}
+	return &config, nil
+}
+
+// Validate - validates the replication configuration
+func (c Config) Validate(bucket string, sameTarget bool) error {
+	// replication config can't have more than 1000 rules
+	if len(c.Rules) > 1000 {
+		return errReplicationTooManyRules
+	}
+	// replication config should have at least one rule
+	if len(c.Rules) == 0 {
+		return errReplicationNoRule
+	}
+	if c.ReplicationArn == "" {
+		return errReplicationArnMissing
+	}
+	// Validate all the rules in the replication config
+	targetMap := make(map[string]struct{})
+	priorityMap := make(map[string]struct{})
+	for _, r := range c.Rules {
+		if len(targetMap) == 0 {
+			targetMap[r.Destination.Bucket] = struct{}{}
+		}
+		if _, ok := targetMap[r.Destination.Bucket]; !ok {
+			return errReplicationDestinationMismatch
+		}
+		if err := r.Validate(bucket, sameTarget); err != nil {
+			return err
+		}
+		if _, ok := priorityMap[string(r.Priority)]; ok {
+			return errReplicationUniquePriority
+		}
+		priorityMap[string(r.Priority)] = struct{}{}
+	}
+	return nil
+}
+
+// ObjectOpts provides information to deduce whether replication
+// can be triggered on the resultant object.
+type ObjectOpts struct {
+	Name         string
+	UserTags     string
+	VersionID    string
+	IsLatest     bool
+	DeleteMarker bool
+	SSEC         bool
+}
+
+// FilterActionableRules returns the rules actions that need to be executed
+// after evaluating prefix/tag filtering
+func (c Config) FilterActionableRules(obj ObjectOpts) []Rule {
+	if obj.Name == "" {
+		return nil
+	}
+	var rules []Rule
+	for _, rule := range c.Rules {
+		if rule.Status == Disabled {
+			continue
+		}
+		if !strings.HasPrefix(obj.Name, rule.Prefix()) {
+			continue
+		}
+		if rule.Filter.TestTags(strings.Split(obj.UserTags, "&")) {
+			rules = append(rules, rule)
+		}
+	}
+	sort.Slice(rules[:], func(i, j int) bool {
+		return rules[i].Priority > rules[j].Priority
+	})
+	return rules
+}
+
+// GetDestination returns destination bucket and storage class.
+func (c Config) GetDestination() Destination {
+	for _, rule := range c.Rules {
+		if rule.Status == Disabled {
+			continue
+		}
+		return rule.Destination
+	}
+	return Destination{}
+}
+
+// Replicate returns true if the object should be replicated.
+func (c Config) Replicate(obj ObjectOpts) bool {
+
+	for _, rule := range c.FilterActionableRules(obj) {
+
+		if obj.DeleteMarker {
+			// Indicates whether MinIO will remove a delete marker. By default, delete markers
+			// are not replicated.
+			return false
+		}
+		if obj.SSEC {
+			return false
+		}
+		if obj.VersionID != "" && !obj.IsLatest {
+			return false
+		}
+		if rule.Status == Disabled {
+			continue
+		}
+		return true
+	}
+	return false
+}
+
+// HasActiveRules - returns whether replication policy has active rules
+// Optionally a prefix can be supplied.
+// If recursive is specified the function will also return true if any level below the
+// prefix has active rules. If no prefix is specified recursive is effectively true.
+func (c Config) HasActiveRules(prefix string, recursive bool) bool {
+	if len(c.Rules) == 0 {
+		return false
+	}
+	for _, rule := range c.Rules {
+		if rule.Status == Disabled {
+			continue
+		}
+		if len(prefix) > 0 && len(rule.Filter.Prefix) > 0 {
+			// incoming prefix must be in rule prefix
+			if !recursive && !strings.HasPrefix(prefix, rule.Filter.Prefix) {
+				continue
+			}
+			// If recursive, we can skip this rule if it doesn't match the tested prefix.
+			if recursive && !strings.HasPrefix(rule.Filter.Prefix, prefix) {
+				continue
+			}
+		}
+		return true
+	}
+	return false
+}

pkg/bucket/replication/rule.go

@@ -0,0 +1,156 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, 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 replication
+
+import (
+	"bytes"
+	"encoding/xml"
+)
+
+// Status represents Enabled/Disabled status
+type Status string
+
+// Supported status types
+const (
+	Enabled  Status = "Enabled"
+	Disabled Status = "Disabled"
+)
+
+// DeleteMarkerReplication - whether delete markers are replicated - https://docs.aws.amazon.com/AmazonS3/latest/dev/replication-add-config.html
+type DeleteMarkerReplication struct {
+	Status Status `xml:"Status"` // should be set to "Disabled" by default
+}
+
+// IsEmpty returns true if DeleteMarkerReplication is not set
+func (d DeleteMarkerReplication) IsEmpty() bool {
+	return len(d.Status) == 0
+}
+
+// Validate validates whether the status is disabled.
+func (d DeleteMarkerReplication) Validate() error {
+	if d.IsEmpty() {
+		return errDeleteMarkerReplicationMissing
+	}
+	if d.Status != Disabled {
+		return errInvalidDeleteMarkerReplicationStatus
+	}
+	return nil
+}
+
+// Rule - a rule for replication configuration.
+type Rule struct {
+	XMLName                 xml.Name                `xml:"Rule" json:"Rule"`
+	ID                      string                  `xml:"ID,omitempty" json:"ID,omitempty"`
+	Status                  Status                  `xml:"Status" json:"Status"`
+	Priority                int                     `xml:"Priority" json:"Priority"`
+	DeleteMarkerReplication DeleteMarkerReplication `xml:"DeleteMarkerReplication" json:"DeleteMarkerReplication"`
+	Destination             Destination             `xml:"Destination" json:"Destination"`
+	Filter                  Filter                  `xml:"Filter" json:"Filter"`
+}
+
+var (
+	errInvalidRuleID                        = Errorf("ID must be less than 255 characters")
+	errEmptyRuleStatus                      = Errorf("Status should not be empty")
+	errInvalidRuleStatus                    = Errorf("Status must be set to either Enabled or Disabled")
+	errDeleteMarkerReplicationMissing       = Errorf("DeleteMarkerReplication must be specified")
+	errPriorityMissing                      = Errorf("Priority must be specified")
+	errInvalidDeleteMarkerReplicationStatus = Errorf("Delete marker replication is currently not supported")
+	errDestinationSourceIdentical           = Errorf("Destination bucket cannot be the same as the source bucket.")
+)
+
+// validateID - checks if ID is valid or not.
+func (r Rule) validateID() error {
+	// cannot be longer than 255 characters
+	if len(r.ID) > 255 {
+		return errInvalidRuleID
+	}
+	return nil
+}
+
+// validateStatus - checks if status is valid or not.
+func (r Rule) validateStatus() error {
+	// Status can't be empty
+	if len(r.Status) == 0 {
+		return errEmptyRuleStatus
+	}
+
+	// Status must be one of Enabled or Disabled
+	if r.Status != Enabled && r.Status != Disabled {
+		return errInvalidRuleStatus
+	}
+	return nil
+}
+
+func (r Rule) validateFilter() error {
+	if err := r.Filter.Validate(); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Prefix - a rule can either have prefix under <filter></filter> or under
+// <filter><and></and></filter>. This method returns the prefix from the
+// location where it is available
+func (r Rule) Prefix() string {
+	if r.Filter.Prefix != "" {
+		return r.Filter.Prefix
+	}
+	return r.Filter.And.Prefix
+}
+
+// Tags - a rule can either have tag under <filter></filter> or under
+// <filter><and></and></filter>. This method returns all the tags from the
+// rule in the format tag1=value1&tag2=value2
+func (r Rule) Tags() string {
+	if !r.Filter.Tag.IsEmpty() {
+		return r.Filter.Tag.String()
+	}
+	if len(r.Filter.And.Tags) != 0 {
+		var buf bytes.Buffer
+		for _, t := range r.Filter.And.Tags {
+			if buf.Len() > 0 {
+				buf.WriteString("&")
+			}
+			buf.WriteString(t.String())
+		}
+		return buf.String()
+	}
+	return ""
+}
+
+// Validate - validates the rule element
+func (r Rule) Validate(bucket string, sameTarget bool) error {
+	if err := r.validateID(); err != nil {
+		return err
+	}
+	if err := r.validateStatus(); err != nil {
+		return err
+	}
+	if err := r.validateFilter(); err != nil {
+		return err
+	}
+	if err := r.DeleteMarkerReplication.Validate(); err != nil {
+		return err
+	}
+	if r.Priority <= 0 {
+		return errPriorityMissing
+	}
+	if r.Destination.Bucket == bucket && sameTarget {
+		return errDestinationSourceIdentical
+	}
+	return nil
+}

pkg/bucket/replication/tag.go

@@ -0,0 +1,56 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, 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 replication
+
+import (
+	"encoding/xml"
+	"unicode/utf8"
+)
+
+// Tag - a tag for a replication configuration Rule filter.
+type Tag struct {
+	XMLName xml.Name `xml:"Tag" json:"Tag"`
+	Key     string   `xml:"Key,omitempty" json:"Key,omitempty"`
+	Value   string   `xml:"Value,omitempty" json:"Value,omitempty"`
+}
+
+var (
+	errInvalidTagKey   = Errorf("The TagKey you have provided is invalid")
+	errInvalidTagValue = Errorf("The TagValue you have provided is invalid")
+)
+
+func (tag Tag) String() string {
+	return tag.Key + "=" + tag.Value
+}
+
+// IsEmpty returns whether this tag is empty or not.
+func (tag Tag) IsEmpty() bool {
+	return tag.Key == ""
+}
+
+// Validate checks this tag.
+func (tag Tag) Validate() error {
+	if len(tag.Key) == 0 || utf8.RuneCountInString(tag.Key) > 128 {
+		return errInvalidTagKey
+	}
+
+	if utf8.RuneCountInString(tag.Value) > 256 {
+		return errInvalidTagValue
+	}
+
+	return nil
+}