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Merge pull request #1233 from harshavardhana/bucket-policy

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bucketpolicy: Improve bucket policy validation, avoid nested rules.
This commit is contained in:
Anand Babu (AB) Periasamy 2016-03-15 18:57:02 -07:00
commit c784707ed8
6 changed files with 187 additions and 57 deletions
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8
pkg/s3/access/README.md → Bucket-Policy.md
View File

@ -9,14 +9,10 @@ This package implements parsing and validating bucket access policies based on A
### Supports following set of operations.
*
s3:*
s3:GetObject
s3:ListBucket
s3:PutObject
s3:CreateBucket
s3:GetBucketLocation
s3:DeleteBucket
s3:DeleteObject
s3:AbortMultipartUpload
s3:ListBucketMultipartUploads
@ -31,3 +27,7 @@ Supported applicable condition keys for each conditions.
s3:prefix
s3:max-keys
### Nested policy support.
Nested policies are not allowed.

19
bucket-handlers.go
View File

@ -33,7 +33,6 @@ import (
"github.com/minio/minio/pkg/crypto/sha256"
"github.com/minio/minio/pkg/fs"
"github.com/minio/minio/pkg/probe"
"github.com/minio/minio/pkg/s3/access"
"github.com/minio/minio/pkg/s3/signature4"
)
@ -54,14 +53,14 @@ func enforceBucketPolicy(action string, bucket string, reqURL *url.URL) (s3Error
}
}
// Parse the saved policy.
accessPolicy, e := accesspolicy.Validate(policy)
bucketPolicy, e := parseBucketPolicy(policy)
if e != nil {
errorIf(probe.NewError(e), "Parse policy failed.", nil)
return ErrAccessDenied
}
// Construct resource in 'arn:aws:s3:::examplebucket' format.
resource := accesspolicy.AWSResourcePrefix + strings.TrimPrefix(reqURL.Path, "/")
resource := AWSResourcePrefix + strings.TrimPrefix(reqURL.Path, "/")
// Get conditions for policy verification.
conditions := make(map[string]string)
@ -70,7 +69,7 @@ func enforceBucketPolicy(action string, bucket string, reqURL *url.URL) (s3Error
}
// Validate action, resource and conditions with current policy statements.
if !bucketPolicyEvalStatements(action, resource, conditions, accessPolicy.Statements) {
if !bucketPolicyEvalStatements(action, resource, conditions, bucketPolicy.Statements) {
return ErrAccessDenied
}
return ErrNone
@ -436,12 +435,6 @@ func (api storageAPI) PutBucketHandler(w http.ResponseWriter, r *http.Request) {
// For all unknown auth types return error.
writeErrorResponse(w, r, ErrAccessDenied, r.URL.Path)
return
case authTypeAnonymous:
// http://docs.aws.amazon.com/AmazonS3/latest/dev/mpuAndPermissions.html
if s3Error := enforceBucketPolicy("s3:CreateBucket", bucket, r.URL); s3Error != ErrNone {
writeErrorResponse(w, r, s3Error, r.URL.Path)
return
}
case authTypePresigned:
ok, err := auth.DoesPresignedSignatureMatch()
if err != nil {
@ -639,12 +632,6 @@ func (api storageAPI) DeleteBucketHandler(w http.ResponseWriter, r *http.Request
// For all unknown auth types return error.
writeErrorResponse(w, r, ErrAccessDenied, r.URL.Path)
return
case authTypeAnonymous:
// http://docs.aws.amazon.com/AmazonS3/latest/dev/mpuAndPermissions.html
if s3Error := enforceBucketPolicy("s3:DeleteBucket", bucket, r.URL); s3Error != ErrNone {
writeErrorResponse(w, r, s3Error, r.URL.Path)
return
}
case authTypePresigned, authTypeSigned:
if s3Error := isReqAuthenticated(api.Signature, r); s3Error != ErrNone {
writeErrorResponse(w, r, s3Error, r.URL.Path)

40
bucket-policy-handlers.go
View File

@ -29,7 +29,6 @@ import (
mux "github.com/gorilla/mux"
"github.com/minio/minio/pkg/fs"
"github.com/minio/minio/pkg/probe"
"github.com/minio/minio/pkg/s3/access"
)
// maximum supported access policy size.
@ -37,12 +36,13 @@ const maxAccessPolicySize = 20 * 1024 * 1024 // 20KiB.
// Verify if a given action is valid for the url path based on the
// existing bucket access policy.
func bucketPolicyEvalStatements(action string, resource string, conditions map[string]string, statements []accesspolicy.Statement) bool {
func bucketPolicyEvalStatements(action string, resource string, conditions map[string]string, statements []policyStatement) bool {
for _, statement := range statements {
if bucketPolicyMatchStatement(action, resource, conditions, statement) {
if statement.Effect == "Allow" {
return true
}
// Do not uncomment kept here for readability.
// else statement.Effect == "Deny"
return false
}
@ -52,7 +52,7 @@ func bucketPolicyEvalStatements(action string, resource string, conditions map[s
}
// Verify if action, resource and conditions match input policy statement.
func bucketPolicyMatchStatement(action string, resource string, conditions map[string]string, statement accesspolicy.Statement) bool {
func bucketPolicyMatchStatement(action string, resource string, conditions map[string]string, statement policyStatement) bool {
// Verify if action matches.
if bucketPolicyActionMatch(action, statement) {
// Verify if resource matches.
@ -67,7 +67,7 @@ func bucketPolicyMatchStatement(action string, resource string, conditions map[s
}
// Verify if given action matches with policy statement.
func bucketPolicyActionMatch(action string, statement accesspolicy.Statement) bool {
func bucketPolicyActionMatch(action string, statement policyStatement) bool {
for _, policyAction := range statement.Actions {
// Policy action can be a regex, validate the action with matching string.
matched, e := regexp.MatchString(policyAction, action)
@ -80,7 +80,7 @@ func bucketPolicyActionMatch(action string, statement accesspolicy.Statement) bo
}
// Verify if given resource matches with policy statement.
func bucketPolicyResourceMatch(resource string, statement accesspolicy.Statement) bool {
func bucketPolicyResourceMatch(resource string, statement policyStatement) bool {
for _, presource := range statement.Resources {
matched, e := regexp.MatchString(presource, strings.TrimPrefix(resource, "/"))
fatalIf(probe.NewError(e), "Invalid pattern, please verify the pattern string.", nil)
@ -93,7 +93,7 @@ func bucketPolicyResourceMatch(resource string, statement accesspolicy.Statement
}
// Verify if given condition matches with policy statement.
func bucketPolicyConditionMatch(conditions map[string]string, statement accesspolicy.Statement) bool {
func bucketPolicyConditionMatch(conditions map[string]string, statement policyStatement) bool {
// Supports following conditions.
// - StringEquals
// - StringNotEquals
@ -152,29 +152,25 @@ func (api storageAPI) PutBucketPolicyHandler(w http.ResponseWriter, r *http.Requ
// Read access policy up to maxAccessPolicySize.
// http://docs.aws.amazon.com/AmazonS3/latest/dev/access-policy-language-overview.html
// bucket policies are limited to 20KB in size, using a limit reader.
accessPolicyBytes, e := ioutil.ReadAll(io.LimitReader(r.Body, maxAccessPolicySize))
bucketPolicyBuf, e := ioutil.ReadAll(io.LimitReader(r.Body, maxAccessPolicySize))
if e != nil {
errorIf(probe.NewError(e).Trace(bucket), "Reading policy failed.", nil)
writeErrorResponse(w, r, ErrInternalError, r.URL.Path)
return
}
// Parse access access.
accessPolicy, e := accesspolicy.Validate(accessPolicyBytes)
// Parse bucket policy.
bucketPolicy, e := parseBucketPolicy(bucketPolicyBuf)
if e != nil {
errorIf(probe.NewError(e), "Unable to parse bucket policy.", nil)
writeErrorResponse(w, r, ErrInvalidPolicyDocument, r.URL.Path)
return
}
// If the policy resource has different bucket name, reject it.
for _, statement := range accessPolicy.Statements {
for _, resource := range statement.Resources {
resourcePrefix := strings.SplitAfter(resource, accesspolicy.AWSResourcePrefix)[1]
if !strings.HasPrefix(resourcePrefix, bucket) {
writeErrorResponse(w, r, ErrMalformedPolicy, r.URL.Path)
return
}
}
// Parse check bucket policy.
if s3Error := checkBucketPolicy(bucket, bucketPolicy); s3Error != ErrNone {
writeErrorResponse(w, r, s3Error, r.URL.Path)
return
}
// Set http request for signature verification.
@ -192,10 +188,10 @@ func (api storageAPI) PutBucketPolicyHandler(w http.ResponseWriter, r *http.Requ
}
} else if isRequestSignatureV4(r) {
sh := sha256.New()
sh.Write(accessPolicyBytes)
sh.Write(bucketPolicyBuf)
ok, err := api.Signature.DoesSignatureMatch(hex.EncodeToString(sh.Sum(nil)))
if err != nil {
errorIf(err.Trace(string(accessPolicyBytes)), "SaveBucketPolicy failed.", nil)
errorIf(err.Trace(string(bucketPolicyBuf)), "SaveBucketPolicy failed.", nil)
writeErrorResponse(w, r, ErrSignatureDoesNotMatch, r.URL.Path)
return
}
@ -206,9 +202,9 @@ func (api storageAPI) PutBucketPolicyHandler(w http.ResponseWriter, r *http.Requ
}
// Save bucket policy.
err := writeBucketPolicy(bucket, accessPolicyBytes)
err := writeBucketPolicy(bucket, bucketPolicyBuf)
if err != nil {
errorIf(err.Trace(bucket), "SaveBucketPolicy failed.", nil)
errorIf(err.Trace(bucket, string(bucketPolicyBuf)), "SaveBucketPolicy failed.", nil)
switch err.ToGoError().(type) {
case fs.BucketNameInvalid:
writeErrorResponse(w, r, ErrInvalidBucketName, r.URL.Path)

102
pkg/s3/access/policy.go → bucket-policy-parser.go
View File

@ -14,14 +14,16 @@
* limitations under the License.
*/
// Package accesspolicy implements AWS Access Policy Language parser in
// 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 accesspolicy
package main
import (
"encoding/json"
"errors"
"fmt"
"regexp"
"sort"
"strings"
)
@ -32,14 +34,10 @@ const (
// supportedActionMap - lists all the actions supported by minio.
var supportedActionMap = map[string]struct{}{
"*": {},
"s3:*": {},
"s3:GetObject": {},
"s3:ListBucket": {},
"s3:PutObject": {},
"s3:CreateBucket": {},
"s3:GetBucketLocation": {},
"s3:DeleteBucket": {},
"s3:DeleteObject": {},
"s3:AbortMultipartUpload": {},
"s3:ListBucketMultipartUploads": {},
@ -47,15 +45,15 @@ var supportedActionMap = map[string]struct{}{
}
// User - canonical users list.
type User struct {
type policyUser struct {
AWS []string
}
// Statement - minio policy statement
type Statement struct {
type policyStatement struct {
Sid string
Effect string
Principal User
Principal policyUser `json:"Principal"`
Actions []string `json:"Action"`
Resources []string `json:"Resource"`
Conditions map[string]map[string]string `json:"Condition"`
@ -63,8 +61,8 @@ type Statement struct {
// BucketPolicy - minio policy collection
type BucketPolicy struct {
Version string // date in 0000-00-00 format
Statements []Statement `json:"Statement"`
Version string // date in 0000-00-00 format
Statements []policyStatement `json:"Statement"`
}
// supportedEffectMap - supported effects.
@ -183,9 +181,66 @@ func isValidConditions(conditions map[string]map[string]string) (err error) {
return nil
}
// Validate - validate if request body is of proper JSON and in
// accordance with policy standards.
func Validate(bucketPolicyBuf []byte) (policy BucketPolicy, err error) {
// List of actions for which prefixes are not allowed.
var invalidPrefixActions = map[string]struct{}{
"s3:GetBucketLocation": {},
"s3:ListBucket": {},
"s3:ListBucketMultipartUploads": {},
// Add actions which do not honor prefixes.
}
// checkBucketPolicy validates unmarshalled bucket policy structure.
func checkBucketPolicy(bucket string, bucketPolicy BucketPolicy) APIErrorCode {
// Validate statements for special actions and collect resources
// for others to validate nesting.
var resources []string
for _, statement := range bucketPolicy.Statements {
for _, action := range statement.Actions {
for _, resource := range statement.Resources {
resourcePrefix := strings.SplitAfter(resource, AWSResourcePrefix)[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 prefix begins
// with bucket, if not reject them.
if !strings.HasPrefix(resourcePrefix, bucket) {
return ErrMalformedPolicy
}
// All valid resources collect them separately to verify nesting.
resources = append(resources, resourcePrefix)
}
}
}
}
// Sort strings as shorter first.
sort.Strings(resources)
for len(resources) > 1 {
var resource string
resource, resources = resources[0], resources[1:]
resourceRegex := regexp.MustCompile(resource)
// 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 {
if resourceRegex.MatchString(otherResource) {
return ErrMalformedPolicy
}
}
}
// 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(bucketPolicyBuf []byte) (policy BucketPolicy, err error) {
if err = json.Unmarshal(bucketPolicyBuf, &policy); err != nil {
return BucketPolicy{}, err
}
@ -216,7 +271,7 @@ func Validate(bucketPolicyBuf []byte) (policy BucketPolicy, err error) {
if err := isValidActions(statement.Actions); err != nil {
return BucketPolicy{}, err
}
// Statment resources should be valid.
// Statement resources should be valid.
if err := isValidResources(statement.Resources); err != nil {
return BucketPolicy{}, err
}
@ -225,6 +280,23 @@ func Validate(bucketPolicyBuf []byte) (policy BucketPolicy, err error) {
return BucketPolicy{}, 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 policy, nil
}

5
bucket-policy.go
View File

@ -138,6 +138,11 @@ func writeBucketPolicy(bucket string, accessPolicyBytes []byte) *probe.Error {
}
}
// Create top level directory.
if e := os.MkdirAll(filepath.Dir(bucketPolicyFile), 0700); e != nil {
return probe.NewError(e)
}
// Write bucket policy.
if e := ioutil.WriteFile(bucketPolicyFile, accessPolicyBytes, 0600); e != nil {
return probe.NewError(e)

70
server_fs_test.go
View File

@ -279,6 +279,76 @@ func (s *MyAPIFSCacheSuite) TestAuth(c *C) {
c.Assert(len(accessID), Equals, minioAccessID)
}
func (s *MyAPIFSCacheSuite) TestBucketPolicy(c *C) {
// Sample bucket policy.
bucketPolicyBuf := `{
"Version": "2012-10-17",
"Statement": [
{
"Action": [
"s3:GetBucketLocation",
"s3:ListBucket"
],
"Effect": "Allow",
"Principal": {
"AWS": [
"*"
]
},
"Resource": [
"arn:aws:s3:::policybucket"
]
},
{
"Action": [
"s3:GetObject"
],
"Effect": "Allow",
"Principal": {
"AWS": [
"*"
]
},
"Resource": [
"arn:aws:s3:::policybucket/this*"
]
}
]
}`
// Put a new bucket policy.
request, err := s.newRequest("PUT", testAPIFSCacheServer.URL+"/policybucket?policy", int64(len(bucketPolicyBuf)), bytes.NewReader([]byte(bucketPolicyBuf)))
c.Assert(err, IsNil)
client := http.Client{}
response, err := client.Do(request)
c.Assert(err, IsNil)
c.Assert(response.StatusCode, Equals, http.StatusNoContent)
// Fetch the uploaded policy.
request, err = s.newRequest("GET", testAPIFSCacheServer.URL+"/policybucket?policy", 0, nil)
c.Assert(err, IsNil)
client = http.Client{}
response, err = client.Do(request)
c.Assert(err, IsNil)
c.Assert(response.StatusCode, Equals, http.StatusOK)
bucketPolicyReadBuf, err := ioutil.ReadAll(response.Body)
c.Assert(err, IsNil)
// Verify if downloaded policy matches with previousy uploaded.
c.Assert(bytes.Equal([]byte(bucketPolicyBuf), bucketPolicyReadBuf), Equals, true)
// Delete policy.
request, err = s.newRequest("DELETE", testAPIFSCacheServer.URL+"/policybucket?policy", 0, nil)
c.Assert(err, IsNil)
client = http.Client{}
response, err = client.Do(request)
c.Assert(err, IsNil)
c.Assert(response.StatusCode, Equals, http.StatusNoContent)
}
func (s *MyAPIFSCacheSuite) TestDeleteBucket(c *C) {
request, err := s.newRequest("PUT", testAPIFSCacheServer.URL+"/deletebucket", 0, nil)
c.Assert(err, IsNil)