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signer.go
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signer.go
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package signer
import (
"bytes"
"crypto/hmac"
"crypto/sha256"
"fmt"
"io/ioutil"
"net/http"
"sort"
"strings"
"time"
)
const (
DateFormat = "20060102T150405Z"
SignAlgorithm = "SDK-HMAC-SHA256"
HeaderXDateTime = "X-Sdk-Date"
HeaderXHost = "host"
HeaderXAuthorization = "Authorization"
HeaderXContentSha256 = "X-Sdk-Content-Sha256"
)
func hmacsha256(keyByte []byte, dataStr string) ([]byte, error) {
hm := hmac.New(sha256.New, []byte(keyByte))
if _, err := hm.Write([]byte(dataStr)); err != nil {
return nil, err
}
return hm.Sum(nil), nil
}
// Build a CanonicalRequest from a regular request string
func CanonicalRequest(request *http.Request, signedHeaders []string) (string, error) {
var hexencode string
var err error
if hex := request.Header.Get(HeaderXContentSha256); hex != "" {
hexencode = hex
} else {
bodyData, err := RequestPayload(request)
if err != nil {
return "", err
}
hexencode, err = HexEncodeSHA256Hash(bodyData)
if err != nil {
return "", err
}
}
return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s", request.Method, CanonicalURI(request), CanonicalQueryString(request), CanonicalHeaders(request, signedHeaders), strings.Join(signedHeaders, ";"), hexencode), err
}
// CanonicalURI returns request uri
func CanonicalURI(request *http.Request) string {
pattens := strings.Split(request.URL.Path, "/")
var uriSlice []string
for _, v := range pattens {
uriSlice = append(uriSlice, escape(v))
}
urlpath := strings.Join(uriSlice, "/")
if len(urlpath) == 0 || urlpath[len(urlpath)-1] != '/' {
urlpath = urlpath + "/"
}
return urlpath
}
// CanonicalQueryString
func CanonicalQueryString(request *http.Request) string {
var keys []string
queryMap := request.URL.Query()
for key := range queryMap {
keys = append(keys, key)
}
sort.Strings(keys)
var query []string
for _, key := range keys {
k := escape(key)
sort.Strings(queryMap[key])
for _, v := range queryMap[key] {
kv := fmt.Sprintf("%s=%s", k, escape(v))
query = append(query, kv)
}
}
queryStr := strings.Join(query, "&")
request.URL.RawQuery = queryStr
return queryStr
}
// CanonicalHeaders
func CanonicalHeaders(request *http.Request, signerHeaders []string) string {
var canonicalHeaders []string
header := make(map[string][]string)
for k, v := range request.Header {
header[strings.ToLower(k)] = v
}
for _, key := range signerHeaders {
value := header[key]
if strings.EqualFold(key, HeaderXHost) {
value = []string{request.Host}
}
sort.Strings(value)
for _, v := range value {
canonicalHeaders = append(canonicalHeaders, key+":"+strings.TrimSpace(v))
}
}
return fmt.Sprintf("%s\n", strings.Join(canonicalHeaders, "\n"))
}
// SignedHeaders
func SignedHeaders(r *http.Request) []string {
var signedHeaders []string
for key := range r.Header {
signedHeaders = append(signedHeaders, strings.ToLower(key))
}
sort.Strings(signedHeaders)
return signedHeaders
}
// RequestPayload
func RequestPayload(request *http.Request) ([]byte, error) {
if request.Body == nil {
return []byte(""), nil
}
bodyByte, err := ioutil.ReadAll(request.Body)
if err != nil {
return []byte(""), err
}
request.Body = ioutil.NopCloser(bytes.NewBuffer(bodyByte))
return bodyByte, err
}
// Create a "String to Sign".
func StringToSign(canonicalRequest string, t time.Time) (string, error) {
hashStruct := sha256.New()
_, err := hashStruct.Write([]byte(canonicalRequest))
if err != nil {
return "", err
}
return fmt.Sprintf("%s\n%s\n%x",
SignAlgorithm, t.UTC().Format(DateFormat), hashStruct.Sum(nil)), nil
}
// Create the HWS Signature.
func SignStringToSign(stringToSign string, signingKey []byte) (string, error) {
hmsha, err := hmacsha256(signingKey, stringToSign)
return fmt.Sprintf("%x", hmsha), err
}
// HexEncodeSHA256Hash returns hexcode of sha256
func HexEncodeSHA256Hash(body []byte) (string, error) {
hashStruct := sha256.New()
if len(body) == 0 {
body = []byte("")
}
_, err := hashStruct.Write(body)
return fmt.Sprintf("%x", hashStruct.Sum(nil)), err
}
// Get the finalized value for the "Authorization" header. The signature parameter is the output from SignStringToSign
func AuthHeaderValue(signatureStr, accessKeyStr string, signedHeaders []string) string {
return fmt.Sprintf("%s Access=%s, SignedHeaders=%s, Signature=%s", SignAlgorithm, accessKeyStr, strings.Join(signedHeaders, ";"), signatureStr)
}
// Signature HWS meta
type Signer struct {
Key string
Secret string
}
// SignRequest set Authorization header
func (s *Signer) Sign(request *http.Request) error {
var t time.Time
var err error
var date string
if date = request.Header.Get(HeaderXDateTime); date != "" {
t, err = time.Parse(DateFormat, date)
}
if err != nil || date == "" {
t = time.Now()
request.Header.Set(HeaderXDateTime, t.UTC().Format(DateFormat))
}
signedHeaders := SignedHeaders(request)
canonicalRequest, err := CanonicalRequest(request, signedHeaders)
if err != nil {
return err
}
stringToSignStr, err := StringToSign(canonicalRequest, t)
if err != nil {
return err
}
signatureStr, err := SignStringToSign(stringToSignStr, []byte(s.Secret))
if err != nil {
return err
}
authValueStr := AuthHeaderValue(signatureStr, s.Key, signedHeaders)
request.Header.Set(HeaderXAuthorization, authValueStr)
return nil
}