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358 lines (325 loc) · 11.6 KB
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/*
* Minio Cloud Storage, (C) 2015, 2016 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 cmd This file implements AWS Access Policy Language parser in
// accordance with http://docs.aws.amazon.com/AmazonS3/latest/dev/access-policy-language-overview.html
package cmd
import (
"encoding/json"
"errors"
"fmt"
"io"
"sort"
"strings"
"github.com/minio/minio-go/pkg/set"
)
var conditionKeyActionMap = map[string]set.StringSet{
"s3:prefix": set.CreateStringSet("s3:ListBucket"),
"s3:max-keys": set.CreateStringSet("s3:ListBucket"),
}
// supportedActionMap - lists all the actions supported by minio.
var supportedActionMap = set.CreateStringSet("*", "s3:*", "s3:GetObject",
"s3:ListBucket", "s3:PutObject", "s3:GetBucketLocation", "s3:DeleteObject",
"s3:AbortMultipartUpload", "s3:ListBucketMultipartUploads", "s3:ListMultipartUploadParts")
// supported Conditions type.
var supportedConditionsType = set.CreateStringSet("StringEquals", "StringNotEquals", "StringLike", "StringNotLike")
// Validate s3:prefix, s3:max-keys are present if not
// supported keys for the conditions.
var supportedConditionsKey = set.CreateStringSet("s3:prefix", "s3:max-keys", "aws:Referer")
// supportedEffectMap - supported effects.
var supportedEffectMap = set.CreateStringSet("Allow", "Deny")
// Statement - minio policy statement
type policyStatement struct {
Actions set.StringSet `json:"Action"`
Conditions map[string]map[string]set.StringSet `json:"Condition,omitempty"`
Effect string
Principal interface{} `json:"Principal"`
Resources set.StringSet `json:"Resource"`
Sid string
}
// bucketPolicy - collection of various bucket policy statements.
type bucketPolicy struct {
Version string // date in YYYY-MM-DD format
Statements []policyStatement `json:"Statement"`
}
// Stringer implementation for the bucket policies.
func (b bucketPolicy) String() string {
bbytes, err := json.Marshal(&b)
if err != nil {
errorIf(err, "Unable to marshal bucket policy into JSON %#v", b)
return ""
}
return string(bbytes)
}
// isValidActions - are actions valid.
func isValidActions(actions set.StringSet) (err error) {
// Statement actions cannot be empty.
if len(actions) == 0 {
err = errors.New("Action list cannot be empty")
return err
}
if unsupportedActions := actions.Difference(supportedActionMap); !unsupportedActions.IsEmpty() {
err = fmt.Errorf("Unsupported actions found: ‘%#v’, please validate your policy document", unsupportedActions)
return err
}
return nil
}
// isValidEffect - is effect valid.
func isValidEffect(effect string) (err error) {
// Statement effect cannot be empty.
if effect == "" {
err = errors.New("Policy effect cannot be empty")
return err
}
if !supportedEffectMap.Contains(effect) {
err = errors.New("Unsupported Effect found: ‘" + effect + "’, please validate your policy document")
return err
}
return nil
}
// isValidResources - are valid resources.
func isValidResources(resources set.StringSet) (err error) {
// Statement resources cannot be empty.
if len(resources) == 0 {
err = errors.New("Resource list cannot be em
8000
pty")
return err
}
for resource := range resources {
if !hasPrefix(resource, bucketARNPrefix) {
err = errors.New("Unsupported resource style found: ‘" + resource + "’, please validate your policy document")
return err
}
resourceSuffix := strings.SplitAfter(resource, bucketARNPrefix)[1]
if len(resourceSuffix) == 0 || hasPrefix(resourceSuffix, "/") {
err = errors.New("Invalid resource style found: ‘" + resource + "’, please validate your policy document")
return err
}
}
return nil
}
// Parse principals parses a incoming json. Handles cases for
// these three combinations.
// - "Principal": "*",
// - "Principal": { "AWS" : "*" }
// - "Principal": { "AWS" : [ "*" ]}
func parsePrincipals(principal interface{}) set.StringSet {
principals, ok := principal.(map[string]interface{})
if !ok {
var principalStr string
principalStr, ok = principal.(string)
if ok {
return set.CreateStringSet(principalStr)
}
} // else {
var principalStrs []string
for _, p := range principals {
principalStr, isStr := p.(string)
if !isStr {
principalsAdd, isInterface := p.([]interface{})
if !isInterface {
principalStrsAddr, isStrs := p.([]string)
if !isStrs {
continue
}
principalStrs = append(principalStrs, principalStrsAddr...)
} else {
for _, pa := range principalsAdd {
var pstr string
pstr, isStr = pa.(string)
if !isStr {
continue
}
principalStrs = append(principalStrs, pstr)
}
}
continue
} // else {
principalStrs = append(principalStrs, principalStr)
}
return set.CreateStringSet(principalStrs...)
}
// isValidPrincipals - are valid principals.
func isValidPrincipals(principal interface{}) (err error) {
principals := parsePrincipals(principal)
// Statement principal should have a value.
if len(principals) == 0 {
err = errors.New("Principal cannot be empty")
return err
}
if unsuppPrincipals := principals.Difference(set.CreateStringSet([]string{"*"}...)); !unsuppPrincipals.IsEmpty() {
// Minio does not support or implement IAM, "*" is the only valid value.
// Amazon s3 doc on principals: http://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements.html#Principal
err = fmt.Errorf("Unsupported principals found: ‘%#v’, please validate your policy document", unsuppPrincipals)
return err
}
return nil
}
// isValidConditions - returns nil if the given conditions valid and
// corresponding error otherwise.
func isValidConditions(actions set.StringSet, conditions map[string]map[string]set.StringSet) (err error) {
// Verify conditions should be valid. Validate if only
// supported condition keys are present and return error
// otherwise.
conditionKeyVal := make(map[string]set.StringSet)
for conditionType := range conditions {
if !supportedConditionsType.Contains(conditionType) {
err = fmt.Errorf("Unsupported condition type '%s', please validate your policy document", conditionType)
return err
}
for key, value := range conditions[conditionType] {
if !supportedConditionsKey.Contains(key) {
err = fmt.Errorf("Unsupported condition key '%s', please validate your policy document", conditionType)
return err
}
compatibleActions := conditionKeyActionMap[key]
if !compatibleActions.IsEmpty() &&
compatibleActions.Intersection(actions).IsEmpty() {
err = fmt.Errorf("Unsupported condition key %s for the given actions %s, "+
"please validate your policy document", key, actions)
return err
}
conditionVal, ok := conditionKeyVal[key]
if ok && !value.Intersection(conditionVal).IsEmpty() {
err = fmt.Errorf("Ambigious condition values for key '%s', please validate your policy document", key)
return err
}
conditionKeyVal[key] = value
}
}
return nil
}
// List of actions for which prefixes are not allowed.
var invalidPrefixActions = set.StringSet{
"s3:GetBucketLocation": {},
"s3:ListBucket": {},
"s3:ListBucketMultipartUploads": {},
// Add actions which do not honor prefixes.
}
// resourcePrefix - provides the prefix removing any wildcards.
func resourcePrefix(resource string) string {
if strings.HasSuffix(resource, "*") {
resource = strings.TrimSuffix(resource, "*")
}
return resource
}
// checkBucketPolicyResources validates Resources in unmarshalled bucket policy structure.
// - Resources are validated against the given set of Actions.
// -
func checkBucketPolicyResources(bucket string, bucketPolicy *bucketPolicy) APIErrorCode {
// Validate statements for special actions and collect resources
// for others to validate nesting.
var resourceMap = set.NewStringSet()
for _, statement := range bucketPolicy.Statements {
for action := range statement.Actions {
for resource := range statement.Resources {
resourcePrefix := strings.SplitAfter(resource, bucketARNPrefix)[1]
if _, ok := invalidPrefixActions[action]; ok {
// Resource prefix is not equal to bucket for
// prefix invalid actions, reject them.
if resourcePrefix != bucket {
return ErrMalformedPolicy
}
} else {
// For all other actions validate if resourcePrefix begins
// with bucket name, if not reject them.
if strings.Split(resourcePrefix, "/")[0] != bucket {
return ErrMalformedPolicy
}
// All valid resources collect them separately to verify nesting.
resourceMap.Add(resourcePrefix)
}
}
}
}
var resources []string
for resource := range resourceMap {
resources = append(resources, resourcePrefix(resource))
}
// Sort strings as shorter first.
sort.Strings(resources)
for len(resources) > 1 {
var resource string
resource, resources = resources[0], resources[1:]
// Loop through all resources, if one of them matches with
// previous shorter one, it means we have detected
// nesting. Reject such rules.
for _, otherResource := range resources {
// Common prefix reject such rules.
if hasPrefix(otherResource, resource) {
return ErrPolicyNesting
}
}
}
// No errors found.
return ErrNone
}
// parseBucketPolicy - parses and validates if bucket policy is of
// proper JSON and follows allowed restrictions with policy standards.
func parseBucketPolicy(bucketPolicyReader io.Reader, policy *bucketPolicy) (err error) {
// Parse bucket policy reader.
decoder := json.NewDecoder(bucketPolicyReader)
if err = decoder.Decode(&policy); err != nil {
return err
}
// Policy version cannot be empty.
if len(policy.Version) == 0 {
err = errors.New("Policy version cannot be empty")
return err
}
// Policy statements cannot be empty.
if len(policy.Statements) == 0 {
err = errors.New("Policy statement cannot be empty")
return err
}
// Loop through all policy statements and validate entries.
for _, statement := range policy.Statements {
// Statement effect should be valid.
if err := isValidEffect(statement.Effect); err != nil {
return err
}
// Statement principal should be supported format.
if err := isValidPrincipals(statement.Principal); err != nil {
return err
}
// Statement actions should be valid.
if err := isValidActions(statement.Actions); err != nil {
return err
}
// Statement resources should be valid.
if err := isValidResources(statement.Resources); err != nil {
return err
}
// Statement conditions should be valid.
if err := isValidConditions(statement.Actions, statement.Conditions); err != nil {
return err
}
}
// Separate deny and allow statements, so that we can apply deny
// statements in the beginning followed by Allow statements.
var denyStatements []policyStatement
var allowStatements []policyStatement
for _, statement := range policy.Statements {
if statement.Effect == "Deny" {
denyStatements = append(denyStatements, statement)
continue
}
// else if statement.Effect == "Allow"
allowStatements = append(allowStatements, statement)
}
// Deny statements are enforced first once matched.
policy.Statements = append(denyStatements, allowStatements...)
// Return successfully parsed policy structure.
return nil
}