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package v2
import (
"crypto/hmac"
"crypto/sha256"
"encoding/base64"
"errors"
"fmt"
"net/http"
"net/url"
"sort"
"strings"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/credentials"
"github.com/aws/aws-sdk-go/aws/request"
)
var (
errInvalidMethod = errors.New("v2 signer only handles HTTP POST")
)
const (
signatureVersion = "2"
signatureMethod = "HmacSHA256"
timeFormat = "2006-01-02T15:04:05Z"
)
type signer struct {
// Values that must be populated from the request
Request *http.Request
Time time.Time
Credentials *credentials.Credentials
Debug aws.LogLevelType
Logger aws.Logger
Query url.Values
stringToSign string
signature string
}
// SignRequestHandler is a named request handler the SDK will use to sign
// service client request with using the V4 signature.
var SignRequestHandler = request.NamedHandler{
Name: "v2.SignRequestHandler", Fn: SignSDKRequest,
}
// SignSDKRequest requests with signature version 2.
//
// Will sign the requests with the service config's Credentials object
// Signing is skipped if the credentials is the credentials.AnonymousCredentials
// object.
func SignSDKRequest(req *request.Request) {
// If the request does not need to be signed ignore the signing of the
// request if the AnonymousCredentials object is used.
if req.Config.Credentials == credentials.AnonymousCredentials {
return
}
if req.HTTPRequest.Method != "POST" && req.HTTPRequest.Method != "GET" {
// The V2 signer only supports GET and POST
req.Error = errInvalidMethod
return
}
v2 := signer{
Request: req.HTTPRequest,
Time: req.Time,
Credentials: req.Config.Credentials,
Debug: req.Config.LogLevel.Value(),
Logger: req.Config.Logger,
}
req.Error = v2.Sign()
if req.Error != nil {
return
}
if req.HTTPRequest.Method == "POST" {
// Set the body of the request based on the modified query parameters
req.SetStringBody(v2.Query.Encode())
// Now that the body has changed, remove any Content-Length header,
// because it will be incorrect
req.HTTPRequest.ContentLength = 0
req.HTTPRequest.Header.Del("Content-Length")
} else {
req.HTTPRequest.URL.RawQuery = v2.Query.Encode()
}
}
func (v2 *signer) Sign() error {
credValue, err := v2.Credentials.Get()
if err != nil {
return err
}
if v2.Request.Method == "POST" {
// Parse the HTTP request to obtain the query parameters that will
// be used to build the string to sign. Note that because the HTTP
// request will need to be modified, the PostForm and Form properties
// are reset to nil after parsing.
v2.Request.ParseForm()
v2.Query = v2.Request.PostForm
v2.Request.PostForm = nil
v2.Request.Form = nil
} else {
v2.Query = v2.Request.URL.Query()
}
// Set new query parameters
v2.Query.Set("AWSAccessKeyId", credValue.AccessKeyID)
v2.Query.Set("SignatureVersion", signatureVersion)
v2.Query.Set("SignatureMethod", signatureMethod)
v2.Query.Set("Timestamp", v2.Time.UTC().Format(timeFormat))
if credValue.SessionToken != "" {
v2.Query.Set("SecurityToken", credValue.SessionToken)
}
// in case this is a retry, ensure no signature present
v2.Query.Del("Signature")
method := v2.Request.Method
host := v2.Request.URL.Host
path := v2.Request.URL.Path
if path == "" {
path = "/"
}
// obtain all of the query keys and sort them
queryKeys := make([]string, 0, len(v2.Query))
for key := range v2.Query {
queryKeys = append(queryKeys, key)
}
sort.Strings(queryKeys)
// build URL-encoded query keys and values
queryKeysAndValues := make([]string, len(queryKeys))
for i, key := range queryKeys {
k := strings.Replace(url.QueryEscape(key), "+", "%20", -1)
v := strings.Replace(url.QueryEscape(v2.Query.Get(key)), "+", "%20", -1)
queryKeysAndValues[i] = k + "=" + v
}
// join into one query string
query := strings.Join(queryKeysAndValues, "&")
// build the canonical string for the V2 signature
v2.stringToSign = strings.Join([]string{
method,
host,
path,
query,
}, "\n")
hash := hmac.New(sha256.New, []byte(credValue.SecretAccessKey))
hash.Write([]byte(v2.stringToSign))
v2.signature = base64.StdEncoding.EncodeToString(hash.Sum(nil))
v2.Query.Set("Signature", v2.signature)
if v2.Debug.Matches(aws.LogDebugWithSigning) {
v2.logSigningInfo()
}
return nil
}
const logSignInfoMsg = `DEBUG: Request Signature:
---[ STRING TO SIGN ]--------------------------------
%s
---[ SIGNATURE ]-------------------------------------
%s
-----------------------------------------------------`
func (v2 *signer) logSigningInfo() {
msg := fmt.Sprintf(logSignInfoMsg, v2.stringToSign, v2.Query.Get("Signature"))
v2.Logger.Log(msg)
}
|
