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312 lines
10 KiB
312 lines
10 KiB
/*
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* Minio Cloud Storage, (C) 2015, 2016 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// Package cmd This file implements AWS Access Policy Language parser in
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// accordance with http://docs.aws.amazon.com/AmazonS3/latest/dev/access-policy-language-overview.html
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package cmd
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import (
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"path"
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"sort"
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"strings"
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"github.com/minio/minio-go/pkg/set"
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)
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const (
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// AWSResourcePrefix - bucket policy resource prefix.
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AWSResourcePrefix = "arn:aws:s3:::"
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)
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// supportedActionMap - lists all the actions supported by minio.
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var supportedActionMap = set.CreateStringSet("*", "*", "s3:*", "s3:GetObject",
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"s3:ListBucket", "s3:PutObject", "s3:GetBucketLocation", "s3:DeleteObject",
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"s3:AbortMultipartUpload", "s3:ListBucketMultipartUploads", "s3:ListMultipartUploadParts")
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// supported Conditions type.
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var supportedConditionsType = set.CreateStringSet("StringEquals", "StringNotEquals")
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// Validate s3:prefix, s3:max-keys are present if not
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// supported keys for the conditions.
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var supportedConditionsKey = set.CreateStringSet("s3:prefix", "s3:max-keys")
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// supportedEffectMap - supported effects.
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var supportedEffectMap = set.CreateStringSet("Allow", "Deny")
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// policyUser - canonical users list.
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type policyUser struct {
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AWS set.StringSet `json:"AWS,omitempty"`
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CanonicalUser set.StringSet `json:"CanonicalUser,omitempty"`
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}
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// Statement - minio policy statement
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type policyStatement struct {
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Actions set.StringSet `json:"Action"`
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Conditions map[string]map[string]set.StringSet `json:"Condition,omitempty"`
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Effect string
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Principal policyUser `json:"Principal"`
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Resources set.StringSet `json:"Resource"`
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Sid string
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}
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// bucketPolicy - collection of various bucket policy statements.
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type bucketPolicy struct {
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Version string // date in YYYY-MM-DD format
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Statements []policyStatement `json:"Statement"`
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}
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// Stringer implementation for the bucket policies.
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func (b bucketPolicy) String() string {
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bbytes, err := json.Marshal(&b)
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if err != nil {
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errorIf(err, "Unable to unmarshal bucket policy into JSON %#v", b)
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return ""
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}
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return string(bbytes)
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}
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// isValidActions - are actions valid.
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func isValidActions(actions set.StringSet) (err error) {
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// Statement actions cannot be empty.
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if len(actions) == 0 {
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err = errors.New("Action list cannot be empty.")
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return err
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}
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if unsupportedActions := actions.Difference(supportedActionMap); !unsupportedActions.IsEmpty() {
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err = fmt.Errorf("Unsupported actions found: ‘%#v’, please validate your policy document.", unsupportedActions)
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return err
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}
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return nil
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}
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// isValidEffect - is effect valid.
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func isValidEffect(effect string) (err error) {
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// Statement effect cannot be empty.
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if effect == "" {
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err = errors.New("Policy effect cannot be empty.")
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return err
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}
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if !supportedEffectMap.Contains(effect) {
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err = errors.New("Unsupported Effect found: ‘" + effect + "’, please validate your policy document.")
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return err
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}
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return nil
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}
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// isValidResources - are valid resources.
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func isValidResources(resources set.StringSet) (err error) {
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// Statement resources cannot be empty.
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if len(resources) == 0 {
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err = errors.New("Resource list cannot be empty.")
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return err
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}
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for resource := range resources {
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if !strings.HasPrefix(resource, AWSResourcePrefix) {
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err = errors.New("Unsupported resource style found: ‘" + resource + "’, please validate your policy document.")
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return err
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}
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resourceSuffix := strings.SplitAfter(resource, AWSResourcePrefix)[1]
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if len(resourceSuffix) == 0 || strings.HasPrefix(resourceSuffix, "/") {
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err = errors.New("Invalid resource style found: ‘" + resource + "’, please validate your policy document.")
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return err
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}
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}
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return nil
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}
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// isValidPrincipals - are valid principals.
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func isValidPrincipals(principals set.StringSet) (err error) {
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// Statement principal should have a value.
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if len(principals) == 0 {
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err = errors.New("Principal cannot be empty.")
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return err
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}
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if unsuppPrincipals := principals.Difference(set.CreateStringSet([]string{"*"}...)); !unsuppPrincipals.IsEmpty() {
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// Minio does not support or implement IAM, "*" is the only valid value.
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// Amazon s3 doc on principals: http://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements.html#Principal
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err = fmt.Errorf("Unsupported principals found: ‘%#v’, please validate your policy document.", unsuppPrincipals)
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return err
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}
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return nil
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}
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// isValidConditions - are valid conditions.
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func isValidConditions(conditions map[string]map[string]set.StringSet) (err error) {
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// Verify conditions should be valid.
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// Validate if stringEquals, stringNotEquals are present
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// if not throw an error.
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conditionKeyVal := make(map[string]set.StringSet)
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for conditionType := range conditions {
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if !supportedConditionsType.Contains(conditionType) {
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err = fmt.Errorf("Unsupported condition type '%s', please validate your policy document.", conditionType)
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return err
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}
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for key, value := range conditions[conditionType] {
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if !supportedConditionsKey.Contains(key) {
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err = fmt.Errorf("Unsupported condition key '%s', please validate your policy document.", conditionType)
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return err
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}
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conditionVal, ok := conditionKeyVal[key]
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if ok && !value.Intersection(conditionVal).IsEmpty() {
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err = fmt.Errorf("Ambigious condition values for key '%s', please validate your policy document.", key)
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return err
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}
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conditionKeyVal[key] = value
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}
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}
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return nil
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}
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// List of actions for which prefixes are not allowed.
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var invalidPrefixActions = set.StringSet{
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"s3:GetBucketLocation": {},
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"s3:ListBucket": {},
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"s3:ListBucketMultipartUploads": {},
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// Add actions which do not honor prefixes.
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}
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// resourcePrefix - provides the prefix removing any wildcards.
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func resourcePrefix(resource string) string {
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if strings.HasSuffix(resource, "*") {
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resource = strings.TrimSuffix(resource, "*")
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}
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return path.Clean(resource)
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}
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// checkBucketPolicyResources validates Resources in unmarshalled bucket policy structure.
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// First valation of Resources done for given set of Actions.
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// Later its validated for recursive Resources.
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func checkBucketPolicyResources(bucket string, bucketPolicy *bucketPolicy) APIErrorCode {
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// Validate statements for special actions and collect resources
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// for others to validate nesting.
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var resourceMap = set.NewStringSet()
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for _, statement := range bucketPolicy.Statements {
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for action := range statement.Actions {
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for resource := range statement.Resources {
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resourcePrefix := strings.SplitAfter(resource, AWSResourcePrefix)[1]
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if _, ok := invalidPrefixActions[action]; ok {
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// Resource prefix is not equal to bucket for
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// prefix invalid actions, reject them.
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if resourcePrefix != bucket {
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return ErrMalformedPolicy
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}
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} else {
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// For all other actions validate if resourcePrefix begins
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// with bucket name, if not reject them.
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if strings.Split(resourcePrefix, "/")[0] != bucket {
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return ErrMalformedPolicy
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}
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// All valid resources collect them separately to verify nesting.
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resourceMap.Add(resourcePrefix)
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}
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}
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}
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}
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var resources []string
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for resource := range resourceMap {
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resources = append(resources, resourcePrefix(resource))
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}
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// Sort strings as shorter first.
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sort.Strings(resources)
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for len(resources) > 1 {
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var resource string
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resource, resources = resources[0], resources[1:]
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// Loop through all resources, if one of them matches with
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// previous shorter one, it means we have detected
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// nesting. Reject such rules.
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for _, otherResource := range resources {
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// Common prefix reject such rules.
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if strings.HasPrefix(otherResource, resource) {
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return ErrPolicyNesting
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}
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}
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}
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// No errors found.
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return ErrNone
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}
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// parseBucketPolicy - parses and validates if bucket policy is of
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// proper JSON and follows allowed restrictions with policy standards.
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func parseBucketPolicy(bucketPolicyReader io.Reader, policy *bucketPolicy) (err error) {
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// Parse bucket policy reader.
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decoder := json.NewDecoder(bucketPolicyReader)
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if err = decoder.Decode(&policy); err != nil {
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return err
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}
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// Policy version cannot be empty.
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if len(policy.Version) == 0 {
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err = errors.New("Policy version cannot be empty.")
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return err
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}
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// Policy statements cannot be empty.
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if len(policy.Statements) == 0 {
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err = errors.New("Policy statement cannot be empty.")
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return err
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}
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// Loop through all policy statements and validate entries.
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for _, statement := range policy.Statements {
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// Statement effect should be valid.
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if err := isValidEffect(statement.Effect); err != nil {
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return err
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}
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// Statement principal should be supported format.
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if err := isValidPrincipals(statement.Principal.AWS); err != nil {
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return err
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}
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// Statement actions should be valid.
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if err := isValidActions(statement.Actions); err != nil {
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return err
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}
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// Statement resources should be valid.
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if err := isValidResources(statement.Resources); err != nil {
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return err
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}
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// Statement conditions should be valid.
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if err := isValidConditions(statement.Conditions); err != nil {
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return err
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}
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}
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// Separate deny and allow statements, so that we can apply deny
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// statements in the beginning followed by Allow statements.
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var denyStatements []policyStatement
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var allowStatements []policyStatement
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for _, statement := range policy.Statements {
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if statement.Effect == "Deny" {
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denyStatements = append(denyStatements, statement)
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continue
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}
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// else if statement.Effect == "Allow"
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allowStatements = append(allowStatements, statement)
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}
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// Deny statements are enforced first once matched.
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policy.Statements = append(denyStatements, allowStatements...)
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// Return successfully parsed policy structure.
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return nil
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}
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