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minio/pkg/signature/signature-v4.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 signature
import (
"bytes"
"crypto/hmac"
"encoding/hex"
"net/http"
"net/url"
"regexp"
"sort"
"strconv"
"strings"
"time"
"unicode/utf8"
"github.com/minio/minio/pkg/crypto/sha256"
"github.com/minio/minio/pkg/probe"
)
// Signature - local variables
type Signature struct {
AccessKeyID string
SecretAccessKey string
Presigned bool
PresignedPolicy string
SignedHeaders []string
Signature string
Request *http.Request
}
const (
authHeaderPrefix = "AWS4-HMAC-SHA256"
iso8601Format = "20060102T150405Z"
yyyymmdd = "20060102"
)
// sumHMAC calculate hmac between two input byte array
func sumHMAC(key []byte, data []byte) []byte {
hash := hmac.New(sha256.New, key)
hash.Write(data)
return hash.Sum(nil)
}
// getURLEncodedName encode the strings from UTF-8 byte representations to HTML hex escape sequences
//
// This is necessary since regular url.Parse() and url.Encode() functions do not support UTF-8
// non english characters cannot be parsed due to the nature in which url.Encode() is written
//
// This function on the other hand is a direct replacement for url.Encode() technique to support
// pretty much every UTF-8 character.
func getURLEncodedName(name string) string {
// if object matches reserved string, no need to encode them
reservedNames := regexp.MustCompile("^[a-zA-Z0-9-_.~/]+$")
if reservedNames.MatchString(name) {
return name
}
var encodedName string
for _, s := range name {
if 'A' <= s && s <= 'Z' || 'a' <= s && s <= 'z' || '0' <= s && s <= '9' { // §2.3 Unreserved characters (mark)
encodedName = encodedName + string(s)
continue
}
switch s {
case '-', '_', '.', '~', '/': // §2.3 Unreserved characters (mark)
encodedName = encodedName + string(s)
continue
default:
len := utf8.RuneLen(s)
if len < 0 {
return name
}
u := make([]byte, len)
utf8.EncodeRune(u, s)
for _, r := range u {
hex := hex.EncodeToString([]byte{r})
encodedName = encodedName + "%" + strings.ToUpper(hex)
}
}
}
return encodedName
}
// getCanonicalHeaders generate a list of request headers with their values
func (r *Signature) getCanonicalHeaders(signedHeaders map[string][]string) string {
var headers []string
vals := make(map[string][]string)
for k, vv := range signedHeaders {
headers = append(headers, strings.ToLower(k))
vals[strings.ToLower(k)] = vv
}
headers = append(headers, "host")
sort.Strings(headers)
var buf bytes.Buffer
for _, k := range headers {
buf.WriteString(k)
buf.WriteByte(':')
switch {
case k == "host":
buf.WriteString(r.Request.Host)
fallthrough
default:
for idx, v := range vals[k] {
if idx > 0 {
buf.WriteByte(',')
}
buf.WriteString(v)
}
buf.WriteByte('\n')
}
}
return buf.String()
}
// getSignedHeaders generate a string i.e alphabetically sorted, semicolon-separated list of lowercase request header names
func (r *Signature) getSignedHeaders(signedHeaders map[string][]string) string {
var headers []string
for k := range signedHeaders {
headers = append(headers, strings.ToLower(k))
}
headers = append(headers, "host")
sort.Strings(headers)
return strings.Join(headers, ";")
}
// extractSignedHeaders extract signed headers from Authorization header
func (r Signature) extractSignedHeaders() map[string][]string {
extractedSignedHeadersMap := make(map[string][]string)
for _, header := range r.SignedHeaders {
val, ok := r.Request.Header[http.CanonicalHeaderKey(header)]
if !ok {
// if not found continue, we will fail later
continue
}
extractedSignedHeadersMap[header] = val
}
return extractedSignedHeadersMap
}
// getCanonicalRequest generate a canonical request of style
//
// canonicalRequest =
// <HTTPMethod>\n
// <CanonicalURI>\n
// <CanonicalQueryString>\n
// <CanonicalHeaders>\n
// <SignedHeaders>\n
// <HashedPayload>
//
func (r *Signature) getCanonicalRequest() string {
payload := r.Request.Header.Get(http.CanonicalHeaderKey("x-amz-content-sha256"))
r.Request.URL.RawQuery = strings.Replace(r.Request.URL.Query().Encode(), "+", "%20", -1)
encodedPath := getURLEncodedName(r.Request.URL.Path)
// convert any space strings back to "+"
encodedPath = strings.Replace(encodedPath, "+", "%20", -1)
canonicalRequest := strings.Join([]string{
r.Request.Method,
encodedPath,
r.Request.URL.RawQuery,
r.getCanonicalHeaders(r.extractSignedHeaders()),
r.getSignedHeaders(r.extractSignedHeaders()),
payload,
}, "\n")
return canonicalRequest
}
// getCanonicalRequest generate a canonical request of style
//
// canonicalRequest =
// <HTTPMethod>\n
// <CanonicalURI>\n
// <CanonicalQueryString>\n
// <CanonicalHeaders>\n
// <SignedHeaders>\n
// <HashedPayload>
//
func (r *Signature) getPresignedCanonicalRequest(presignedQuery string) string {
rawQuery := strings.Replace(presignedQuery, "+", "%20", -1)
encodedPath := getURLEncodedName(r.Request.URL.Path)
// convert any space strings back to "+"
encodedPath = strings.Replace(encodedPath, "+", "%20", -1)
canonicalRequest := strings.Join([]string{
r.Request.Method,
encodedPath,
rawQuery,
r.getCanonicalHeaders(r.extractSignedHeaders()),
r.getSignedHeaders(r.extractSignedHeaders()),
"UNSIGNED-PAYLOAD",
}, "\n")
return canonicalRequest
}
// getScope generate a string of a specific date, an AWS region, and a service
func (r *Signature) getScope(t time.Time) string {
scope := strings.Join([]string{
t.Format(yyyymmdd),
"milkyway",
"s3",
"aws4_request",
}, "/")
return scope
}
// getStringToSign a string based on selected query values
func (r *Signature) getStringToSign(canonicalRequest string, t time.Time) string {
stringToSign := authHeaderPrefix + "\n" + t.Format(iso8601Format) + "\n"
stringToSign = stringToSign + r.getScope(t) + "\n"
stringToSign = stringToSign + hex.EncodeToString(sha256.Sum256([]byte(canonicalRequest)))
return stringToSign
}
// getSigningKey hmac seed to calculate final signature
func (r *Signature) getSigningKey(t time.Time) []byte {
secret := r.SecretAccessKey
date := sumHMAC([]byte("AWS4"+secret), []byte(t.Format(yyyymmdd)))
region := sumHMAC(date, []byte("milkyway"))
service := sumHMAC(region, []byte("s3"))
signingKey := sumHMAC(service, []byte("aws4_request"))
return signingKey
}
// getSignature final signature in hexadecimal form
func (r *Signature) getSignature(signingKey []byte, stringToSign string) string {
return hex.EncodeToString(sumHMAC(signingKey, []byte(stringToSign)))
}
// DoesPolicySignatureMatch - Verify query headers with post policy
// - http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-HTTPPOSTConstructPolicy.html
// returns true if matches, false otherwise. if error is not nil then it is always false
func (r *Signature) DoesPolicySignatureMatch(date string) (bool, *probe.Error) {
t, err := time.Parse(iso8601Format, date)
if err != nil {
return false, probe.NewError(err)
}
signingKey := r.getSigningKey(t)
stringToSign := string(r.PresignedPolicy)
newSignature := r.getSignature(signingKey, stringToSign)
if newSignature != r.Signature {
return false, nil
}
return true, nil
}
// DoesPresignedSignatureMatch - Verify query headers with presigned signature
// - http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html
// returns true if matches, false otherwise. if error is not nil then it is always false
func (r *Signature) DoesPresignedSignatureMatch() (bool, *probe.Error) {
query := make(url.Values)
query.Set("X-Amz-Algorithm", authHeaderPrefix)
var date string
if date = r.Request.URL.Query().Get("X-Amz-Date"); date == "" {
return false, probe.NewError(MissingDateHeader{})
}
t, err := time.Parse(iso8601Format, date)
if err != nil {
return false, probe.NewError(err)
}
if _, ok := r.Request.URL.Query()["X-Amz-Expires"]; !ok {
return false, probe.NewError(MissingExpiresQuery{})
}
expireSeconds, err := strconv.Atoi(r.Request.URL.Query().Get("X-Amz-Expires"))
if err != nil {
return false, probe.NewError(err)
}
if time.Now().UTC().Sub(t) > time.Duration(expireSeconds)*time.Second {
return false, probe.NewError(ExpiredPresignedRequest{})
}
query.Set("X-Amz-Date", t.Format(iso8601Format))
query.Set("X-Amz-Expires", strconv.Itoa(expireSeconds))
query.Set("X-Amz-SignedHeaders", r.getSignedHeaders(r.extractSignedHeaders()))
query.Set("X-Amz-Credential", r.AccessKeyID+"/"+r.getScope(t))
encodedQuery := query.Encode()
newSignature := r.getSignature(r.getSigningKey(t), r.getStringToSign(r.getPresignedCanonicalRequest(encodedQuery), t))
encodedQuery += "&X-Amz-Signature=" + newSignature
if encodedQuery != r.Request.URL.RawQuery {
return false, nil
}
return true, nil
}
// DoesSignatureMatch - Verify authorization header with calculated header in accordance with
// - http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html
// returns true if matches, false otherwise. if error is not nil then it is always false
func (r *Signature) DoesSignatureMatch(hashedPayload string) (bool, *probe.Error) {
// set new calulated payload
r.Request.Header.Set("X-Amz-Content-Sha256", hashedPayload)
// Add date if not present throw error
var date string
if date = r.Request.Header.Get(http.CanonicalHeaderKey("x-amz-date")); date == "" {
if date = r.Request.Header.Get("Date"); date == "" {
return false, probe.NewError(MissingDateHeader{})
}
}
t, err := time.Parse(iso8601Format, date)
if err != nil {
return false, probe.NewError(err)
}
canonicalRequest := r.getCanonicalRequest()
stringToSign := r.getStringToSign(canonicalRequest, t)
signingKey := r.getSigningKey(t)
newSignature := r.getSignature(signingKey, stringToSign)
if newSignature != r.Signature {
return false, nil
}
return true, nil
}