minio/cmd/signature-v4-parser.go

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/*
* Minio Cloud Storage, (C) 2015 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
import (
"net/url"
"strings"
"time"
)
// credentialHeader data type represents structured form of Credential
// string from authorization header.
type credentialHeader struct {
accessKey string
scope struct {
date time.Time
region string
service string
request string
}
}
// parse credentialHeader string into its structured form.
func parseCredentialHeader(credElement string) (credentialHeader, APIErrorCode) {
creds := strings.Split(strings.TrimSpace(credElement), "=")
if len(creds) != 2 {
return credentialHeader{}, ErrMissingFields
}
if creds[0] != "Credential" {
return credentialHeader{}, ErrMissingCredTag
}
credElements := strings.Split(strings.TrimSpace(creds[1]), "/")
if len(credElements) != 5 {
return credentialHeader{}, ErrCredMalformed
}
if !isAccessKeyValid(credElements[0]) {
return credentialHeader{}, ErrInvalidAccessKeyID
}
// Save access key id.
cred := credentialHeader{
accessKey: credElements[0],
}
var e error
cred.scope.date, e = time.Parse(yyyymmdd, credElements[1])
if e != nil {
return credentialHeader{}, ErrMalformedCredentialDate
}
if credElements[2] == "" {
return credentialHeader{}, ErrMalformedCredentialRegion
}
cred.scope.region = credElements[2]
if credElements[3] != "s3" {
return credentialHeader{}, ErrInvalidService
}
cred.scope.service = credElements[3]
if credElements[4] != "aws4_request" {
return credentialHeader{}, ErrInvalidRequestVersion
}
cred.scope.request = credElements[4]
return cred, ErrNone
}
// Parse signature from signature tag.
func parseSignature(signElement string) (string, APIErrorCode) {
signFields := strings.Split(strings.TrimSpace(signElement), "=")
if len(signFields) != 2 {
return "", ErrMissingFields
}
if signFields[0] != "Signature" {
return "", ErrMissingSignTag
}
if signFields[1] == "" {
return "", ErrMissingFields
}
signature := signFields[1]
return signature, ErrNone
}
// Parse slice of signed headers from signed headers tag.
func parseSignedHeader(signedHdrElement string) ([]string, APIErrorCode) {
signedHdrFields := strings.Split(strings.TrimSpace(signedHdrElement), "=")
if len(signedHdrFields) != 2 {
return nil, ErrMissingFields
}
if signedHdrFields[0] != "SignedHeaders" {
return nil, ErrMissingSignHeadersTag
}
if signedHdrFields[1] == "" {
return nil, ErrMissingFields
}
signedHeaders := strings.Split(signedHdrFields[1], ";")
return signedHeaders, ErrNone
}
// signValues data type represents structured form of AWS Signature V4 header.
type signValues struct {
Credential credentialHeader
SignedHeaders []string
Signature string
}
// preSignValues data type represents structued form of AWS Signature V4 query string.
type preSignValues struct {
signValues
Date time.Time
Expires time.Duration
}
// Parses signature version '4' query string of the following form.
//
// querystring = X-Amz-Algorithm=algorithm
// querystring += &X-Amz-Credential= urlencode(accessKey + '/' + credential_scope)
// querystring += &X-Amz-Date=date
// querystring += &X-Amz-Expires=timeout interval
// querystring += &X-Amz-SignedHeaders=signed_headers
// querystring += &X-Amz-Signature=signature
//
// verifies if any of the necessary query params are missing in the presigned request.
func doesV4PresignParamsExist(query url.Values) APIErrorCode {
v4PresignQueryParams := []string{"X-Amz-Algorithm", "X-Amz-Credential", "X-Amz-Signature", "X-Amz-Date", "X-Amz-SignedHeaders", "X-Amz-Expires"}
for _, v4PresignQueryParam := range v4PresignQueryParams {
if _, ok := query[v4PresignQueryParam]; !ok {
return ErrInvalidQueryParams
}
}
return ErrNone
}
// Parses all the presigned signature values into separate elements.
func parsePreSignV4(query url.Values) (preSignValues, APIErrorCode) {
var err APIErrorCode
// verify whether the required query params exist.
err = doesV4PresignParamsExist(query)
if err != ErrNone {
return preSignValues{}, err
}
// Verify if the query algorithm is supported or not.
if query.Get("X-Amz-Algorithm") != signV4Algorithm {
return preSignValues{}, ErrInvalidQuerySignatureAlgo
}
// Initialize signature version '4' structured header.
preSignV4Values := preSignValues{}
// Save credential.
preSignV4Values.Credential, err = parseCredentialHeader("Credential=" + query.Get("X-Amz-Credential"))
if err != ErrNone {
return preSignValues{}, err
}
var e error
// Save date in native time.Time.
preSignV4Values.Date, e = time.Parse(iso8601Format, query.Get("X-Amz-Date"))
if e != nil {
return preSignValues{}, ErrMalformedPresignedDate
}
// Save expires in native time.Duration.
preSignV4Values.Expires, e = time.ParseDuration(query.Get("X-Amz-Expires") + "s")
if e != nil {
return preSignValues{}, ErrMalformedExpires
}
if preSignV4Values.Expires < 0 {
return preSignValues{}, ErrNegativeExpires
}
// Save signed headers.
preSignV4Values.SignedHeaders, err = parseSignedHeader("SignedHeaders=" + query.Get("X-Amz-SignedHeaders"))
if err != ErrNone {
return preSignValues{}, err
}
// Save signature.
preSignV4Values.Signature, err = parseSignature("Signature=" + query.Get("X-Amz-Signature"))
if err != ErrNone {
return preSignValues{}, err
}
// Return structed form of signature query string.
return preSignV4Values, ErrNone
}
// Parses signature version '4' header of the following form.
//
// Authorization: algorithm Credential=accessKeyID/credScope, \
// SignedHeaders=signedHeaders, Signature=signature
//
func parseSignV4(v4Auth string) (signValues, APIErrorCode) {
// Replace all spaced strings, some clients can send spaced
// parameters and some won't. So we pro-actively remove any spaces
// to make parsing easier.
v4Auth = strings.Replace(v4Auth, " ", "", -1)
if v4Auth == "" {
return signValues{}, ErrAuthHeaderEmpty
}
// Verify if the header algorithm is supported or not.
if !strings.HasPrefix(v4Auth, signV4Algorithm) {
return signValues{}, ErrSignatureVersionNotSupported
}
// Strip off the Algorithm prefix.
v4Auth = strings.TrimPrefix(v4Auth, signV4Algorithm)
authFields := strings.Split(strings.TrimSpace(v4Auth), ",")
if len(authFields) != 3 {
return signValues{}, ErrMissingFields
}
// Initialize signature version '4' structured header.
signV4Values := signValues{}
var err APIErrorCode
// Save credentail values.
signV4Values.Credential, err = parseCredentialHeader(authFields[0])
if err != ErrNone {
return signValues{}, err
}
// Save signed headers.
signV4Values.SignedHeaders, err = parseSignedHeader(authFields[1])
if err != ErrNone {
return signValues{}, err
}
// Save signature.
signV4Values.Signature, err = parseSignature(authFields[2])
if err != ErrNone {
return signValues{}, err
}
// Return the structure here.
return signV4Values, ErrNone
}