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277 lines
9 KiB
Go
277 lines
9 KiB
Go
package policy
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/*
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* MinIO Cloud Storage, (C) 2015, 2016, 2017 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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import (
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"encoding/json"
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"errors"
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"fmt"
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"net/http"
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"reflect"
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"strconv"
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"strings"
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"time"
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)
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// startWithConds - map which indicates if a given condition supports starts-with policy operator
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var startsWithConds = map[string]bool{
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"$acl": true,
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"$bucket": false,
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"$cache-control": true,
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"$content-type": true,
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"$content-disposition": true,
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"$content-encoding": true,
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"$expires": true,
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"$key": true,
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"$success_action_redirect": true,
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"$redirect": true,
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"$success_action_status": false,
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"$x-amz-algorithm": false,
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"$x-amz-credential": false,
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"$x-amz-date": false,
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}
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// Add policy conditionals.
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const (
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policyCondEqual = "eq"
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policyCondStartsWith = "starts-with"
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policyCondContentLength = "content-length-range"
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)
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// toString - Safely convert interface to string without causing panic.
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func toString(val interface{}) string {
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switch v := val.(type) {
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case string:
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return v
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default:
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return ""
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}
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}
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// toLowerString - safely convert interface to lower string
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func toLowerString(val interface{}) string {
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return strings.ToLower(toString(val))
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}
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// toInteger _ Safely convert interface to integer without causing panic.
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func toInteger(val interface{}) (int64, error) {
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switch v := val.(type) {
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case float64:
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return int64(v), nil
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case int64:
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return v, nil
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case int:
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return int64(v), nil
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case string:
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i, err := strconv.Atoi(v)
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return int64(i), err
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default:
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return 0, errors.New("Invalid number format")
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}
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}
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// isString - Safely check if val is of type string without causing panic.
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func isString(val interface{}) bool {
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_, ok := val.(string)
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return ok
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}
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// ContentLengthRange - policy content-length-range field.
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type contentLengthRange struct {
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Min int64
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Max int64
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Valid bool // If content-length-range was part of policy
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}
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// PostPolicyForm provides strict static type conversion and validation for Amazon S3's POST policy JSON string.
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type PostPolicyForm struct {
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Expiration time.Time // Expiration date and time of the POST policy.
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Conditions struct { // Conditional policy structure.
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Policies []struct {
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Operator string
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Key string
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Value string
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}
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ContentLengthRange contentLengthRange
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}
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}
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// ParsePostPolicyForm - Parse JSON policy string into typed PostPolicyForm structure.
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func ParsePostPolicyForm(policy string) (ppf PostPolicyForm, e error) {
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// Convert po into interfaces and
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// perform strict type conversion using reflection.
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var rawPolicy struct {
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Expiration string `json:"expiration"`
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Conditions []interface{} `json:"conditions"`
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}
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err := json.Unmarshal([]byte(policy), &rawPolicy)
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if err != nil {
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return ppf, err
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}
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parsedPolicy := PostPolicyForm{}
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// Parse expiry time.
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parsedPolicy.Expiration, err = time.Parse(time.RFC3339Nano, rawPolicy.Expiration)
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if err != nil {
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return ppf, err
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}
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// Parse conditions.
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for _, val := range rawPolicy.Conditions {
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switch condt := val.(type) {
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case map[string]interface{}: // Handle key:value map types.
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for k, v := range condt {
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if !isString(v) { // Pre-check value type.
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// All values must be of type string.
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return parsedPolicy, fmt.Errorf("Unknown type %s of conditional field value %s found in POST policy form", reflect.TypeOf(condt).String(), condt)
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}
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// {"acl": "public-read" } is an alternate way to indicate - [ "eq", "$acl", "public-read" ]
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// In this case we will just collapse this into "eq" for all use cases.
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parsedPolicy.Conditions.Policies = append(parsedPolicy.Conditions.Policies, struct {
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Operator string
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Key string
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Value string
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}{
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policyCondEqual, "$" + strings.ToLower(k), toString(v),
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})
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}
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case []interface{}: // Handle array types.
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if len(condt) != 3 { // Return error if we have insufficient elements.
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return parsedPolicy, fmt.Errorf("Malformed conditional fields %s of type %s found in POST policy form", condt, reflect.TypeOf(condt).String())
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}
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switch toLowerString(condt[0]) {
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case policyCondEqual, policyCondStartsWith:
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for _, v := range condt { // Pre-check all values for type.
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if !isString(v) {
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// All values must be of type string.
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return parsedPolicy, fmt.Errorf("Unknown type %s of conditional field value %s found in POST policy form", reflect.TypeOf(condt).String(), condt)
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}
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}
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operator, matchType, value := toLowerString(condt[0]), toLowerString(condt[1]), toString(condt[2])
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if !strings.HasPrefix(matchType, "$") {
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return parsedPolicy, fmt.Errorf("Invalid according to Policy: Policy Condition failed: [%s, %s, %s]", operator, matchType, value)
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}
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parsedPolicy.Conditions.Policies = append(parsedPolicy.Conditions.Policies, struct {
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Operator string
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Key string
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Value string
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}{
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operator, matchType, value,
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})
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case policyCondContentLength:
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min, err := toInteger(condt[1])
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if err != nil {
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return parsedPolicy, err
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}
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max, err := toInteger(condt[2])
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if err != nil {
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return parsedPolicy, err
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}
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parsedPolicy.Conditions.ContentLengthRange = contentLengthRange{
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Min: min,
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Max: max,
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Valid: true,
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}
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default:
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// Condition should be valid.
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return parsedPolicy, fmt.Errorf("Unknown type %s of conditional field value %s found in POST policy form",
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reflect.TypeOf(condt).String(), condt)
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}
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default:
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return parsedPolicy, fmt.Errorf("Unknown field %s of type %s found in POST policy form",
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condt, reflect.TypeOf(condt).String())
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}
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}
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return parsedPolicy, nil
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}
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// checkPolicyCond returns a boolean to indicate if a condition is satisified according
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// to the passed operator
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func checkPolicyCond(op string, input1, input2 string) bool {
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switch op {
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case policyCondEqual:
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return input1 == input2
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case policyCondStartsWith:
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return strings.HasPrefix(input1, input2)
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}
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return false
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}
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// CheckPostPolicy - apply policy conditions and validate input values.
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// (http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-HTTPPOSTConstructPolicy.html)
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func CheckPostPolicy(formValues http.Header, postPolicyForm PostPolicyForm) error {
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// Check if policy document expiry date is still not reached
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if !postPolicyForm.Expiration.After(time.Now().UTC()) {
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return fmt.Errorf("Invalid according to Policy: Policy expired")
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}
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// map to store the metadata
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metaMap := make(map[string]string)
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for _, policy := range postPolicyForm.Conditions.Policies {
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if strings.HasPrefix(policy.Key, "$x-amz-meta-") {
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formCanonicalName := http.CanonicalHeaderKey(strings.TrimPrefix(policy.Key, "$"))
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metaMap[formCanonicalName] = policy.Value
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}
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}
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// Check if any extra metadata field is passed as input
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for key := range formValues {
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if strings.HasPrefix(key, "X-Amz-Meta-") {
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if _, ok := metaMap[key]; !ok {
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return fmt.Errorf("Invalid according to Policy: Extra input fields: %s", key)
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}
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}
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}
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// Flag to indicate if all policies conditions are satisfied
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var condPassed bool
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// Iterate over policy conditions and check them against received form fields
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for _, policy := range postPolicyForm.Conditions.Policies {
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// Form fields names are in canonical format, convert conditions names
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// to canonical for simplification purpose, so `$key` will become `Key`
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formCanonicalName := http.CanonicalHeaderKey(strings.TrimPrefix(policy.Key, "$"))
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// Operator for the current policy condition
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op := policy.Operator
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// If the current policy condition is known
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if startsWithSupported, condFound := startsWithConds[policy.Key]; condFound {
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// Check if the current condition supports starts-with operator
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if op == policyCondStartsWith && !startsWithSupported {
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return fmt.Errorf("Invalid according to Policy: Policy Condition failed")
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}
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// Check if current policy condition is satisfied
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condPassed = checkPolicyCond(op, formValues.Get(formCanonicalName), policy.Value)
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if !condPassed {
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return fmt.Errorf("Invalid according to Policy: Policy Condition failed")
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}
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} else {
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// This covers all conditions X-Amz-Meta-* and X-Amz-*
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if strings.HasPrefix(policy.Key, "$x-amz-meta-") || strings.HasPrefix(policy.Key, "$x-amz-") {
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// Check if policy condition is satisfied
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condPassed = checkPolicyCond(op, formValues.Get(formCanonicalName), policy.Value)
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if !condPassed {
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return fmt.Errorf("Invalid according to Policy: Policy Condition failed: [%s, %s, %s]", op, policy.Key, policy.Value)
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}
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}
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}
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}
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return nil
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}
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