// Copyright (C) MongoDB, Inc. 2017-present.
//
// 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
//
// Based on github.com/aws/aws-sdk-go by Amazon.com, Inc. with code from:
// - github.com/aws/aws-sdk-go/blob/v1.44.225/aws/signer/v4/v4.go
// See THIRD-PARTY-NOTICES for original license terms
package v4
import (
"crypto/hmac"
"crypto/sha256"
"encoding/hex"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"sort"
"strings"
"time"
"go.mongodb.org/mongo-driver/internal/aws"
"go.mongodb.org/mongo-driver/internal/aws/credentials"
)
const (
authorizationHeader = "Authorization"
authHeaderSignatureElem = "Signature="
authHeaderPrefix = "AWS4-HMAC-SHA256"
timeFormat = "20060102T150405Z"
shortTimeFormat = "20060102"
awsV4Request = "aws4_request"
// emptyStringSHA256 is a SHA256 of an empty string
emptyStringSHA256 = `e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855`
)
var ignoredHeaders = rules{
excludeList{
mapRule{
authorizationHeader: struct{}{},
"User-Agent": struct{}{},
"X-Amzn-Trace-Id": struct{}{},
},
},
}
// Signer applies AWS v4 signing to given request. Use this to sign requests
// that need to be signed with AWS V4 Signatures.
type Signer struct {
// The authentication credentials the request will be signed against.
// This value must be set to sign requests.
Credentials *credentials.Credentials
}
// NewSigner returns a Signer pointer configured with the credentials provided.
func NewSigner(credentials *credentials.Credentials) *Signer {
v4 := &Signer{
Credentials: credentials,
}
return v4
}
type signingCtx struct {
ServiceName string
Region string
Request *http.Request
Body io.ReadSeeker
Query url.Values
Time time.Time
SignedHeaderVals http.Header
credValues credentials.Value
bodyDigest string
signedHeaders string
canonicalHeaders string
canonicalString string
credentialString string
stringToSign string
signature string
}
// Sign signs AWS v4 requests with the provided body, service name, region the
// request is made to, and time the request is signed at. The signTime allows
// you to specify that a request is signed for the future, and cannot be
// used until then.
//
// Returns a list of HTTP headers that were included in the signature or an
// error if signing the request failed. Generally for signed requests this value
// is not needed as the full request context will be captured by the http.Request
// value. It is included for reference though.
//
// Sign will set the request's Body to be the `body` parameter passed in. If
// the body is not already an io.ReadCloser, it will be wrapped within one. If
// a `nil` body parameter passed to Sign, the request's Body field will be
// also set to nil. Its important to note that this functionality will not
// change the request's ContentLength of the request.
//
// Sign differs from Presign in that it will sign the request using HTTP
// header values. This type of signing is intended for http.Request values that
// will not be shared, or are shared in a way the header values on the request
// will not be lost.
//
// The requests body is an io.ReadSeeker so the SHA256 of the body can be
// generated. To bypass the signer computing the hash you can set the
// "X-Amz-Content-Sha256" header with a precomputed value. The signer will
// only compute the hash if the request header value is empty.
func (v4 Signer) Sign(r *http.Request, body io.ReadSeeker, service, region string, signTime time.Time) (http.Header, error) {
return v4.signWithBody(r, body, service, region, signTime)
}
func (v4 Signer) signWithBody(r *http.Request, body io.ReadSeeker, service, region string, signTime time.Time) (http.Header, error) {
ctx := &signingCtx{
Request: r,
Body: body,
Query: r.URL.Query(),
Time: signTime,
ServiceName: service,
Region: region,
}
for key := range ctx.Query {
sort.Strings(ctx.Query[key])
}
if ctx.isRequestSigned() {
ctx.Time = time.Now()
}
var err error
ctx.credValues, err = v4.Credentials.GetWithContext(r.Context())
if err != nil {
return http.Header{}, err
}
ctx.sanitizeHostForHeader()
ctx.assignAmzQueryValues()
if err := ctx.build(); err != nil {
return nil, err
}
var reader io.ReadCloser
if body != nil {
var ok bool
if reader, ok = body.(io.ReadCloser); !ok {
reader = ioutil.NopCloser(body)
}
}
r.Body = reader
return ctx.SignedHeaderVals, nil
}
// sanitizeHostForHeader removes default port from host and updates request.Host
func (ctx *signingCtx) sanitizeHostForHeader() {
r := ctx.Request
host := getHost(r)
port := portOnly(host)
if port != "" && isDefaultPort(r.URL.Scheme, port) {
r.Host = stripPort(host)
}
}
func (ctx *signingCtx) assignAmzQueryValues() {
if ctx.credValues.SessionToken != "" {
ctx.Request.Header.Set("X-Amz-Security-Token", ctx.credValues.SessionToken)
}
}
func (ctx *signingCtx) build() error {
ctx.buildTime() // no depends
ctx.buildCredentialString() // no depends
if err := ctx.buildBodyDigest(); err != nil {
return err
}
unsignedHeaders := ctx.Request.Header
ctx.buildCanonicalHeaders(ignoredHeaders, unsignedHeaders)
ctx.buildCanonicalString() // depends on canon headers / signed headers
ctx.buildStringToSign() // depends on canon string
ctx.buildSignature() // depends on string to sign
parts := []string{
authHeaderPrefix + " Credential=" + ctx.credValues.AccessKeyID + "/" + ctx.credentialString,
"SignedHeaders=" + ctx.signedHeaders,
authHeaderSignatureElem + ctx.signature,
}
ctx.Request.Header.Set(authorizationHeader, strings.Join(parts, ", "))
return nil
}
func (ctx *signingCtx) buildTime() {
ctx.Request.Header.Set("X-Amz-Date", formatTime(ctx.Time))
}
func (ctx *signingCtx) buildCredentialString() {
ctx.credentialString = buildSigningScope(ctx.Region, ctx.ServiceName, ctx.Time)
}
func (ctx *signingCtx) buildCanonicalHeaders(r rule, header http.Header) {
headers := make([]string, 0, len(header)+1)
headers = append(headers, "host")
for k, v := range header {
if !r.IsValid(k) {
continue // ignored header
}
if ctx.SignedHeaderVals == nil {
ctx.SignedHeaderVals = make(http.Header)
}
lowerCaseKey := strings.ToLower(k)
if _, ok := ctx.SignedHeaderVals[lowerCaseKey]; ok {
// include additional values
ctx.SignedHeaderVals[lowerCaseKey] = append(ctx.SignedHeaderVals[lowerCaseKey], v...)
continue
}
headers = append(headers, lowerCaseKey)
ctx.SignedHeaderVals[lowerCaseKey] = v
}
sort.Strings(headers)
ctx.signedHeaders = strings.Join(headers, ";")
headerItems := make([]string, len(headers))
for i, k := range headers {
if k == "host" {
if ctx.Request.Host != "" {
headerItems[i] = "host:" + ctx.Request.Host
} else {
headerItems[i] = "host:" + ctx.Request.URL.Host
}
} else {
headerValues := make([]string, len(ctx.SignedHeaderVals[k]))
for i, v := range ctx.SignedHeaderVals[k] {
headerValues[i] = strings.TrimSpace(v)
}
headerItems[i] = k + ":" +
strings.Join(headerValues, ",")
}
}
stripExcessSpaces(headerItems)
ctx.canonicalHeaders = strings.Join(headerItems, "\n")
}
func (ctx *signingCtx) buildCanonicalString() {
ctx.Request.URL.RawQuery = strings.Replace(ctx.Query.Encode(), "+", "%20", -1)
uri := getURIPath(ctx.Request.URL)
uri = EscapePath(uri, false)
ctx.canonicalString = strings.Join([]string{
ctx.Request.Method,
uri,
ctx.Request.URL.RawQuery,
ctx.canonicalHeaders + "\n",
ctx.signedHeaders,
ctx.bodyDigest,
}, "\n")
}
func (ctx *signingCtx) buildStringToSign() {
ctx.stringToSign = strings.Join([]string{
authHeaderPrefix,
formatTime(ctx.Time),
ctx.credentialString,
hex.EncodeToString(hashSHA256([]byte(ctx.canonicalString))),
}, "\n")
}
func (ctx *signingCtx) buildSignature() {
creds := deriveSigningKey(ctx.Region, ctx.ServiceName, ctx.credValues.SecretAccessKey, ctx.Time)
signature := hmacSHA256(creds, []byte(ctx.stringToSign))
ctx.signature = hex.EncodeToString(signature)
}
func (ctx *signingCtx) buildBodyDigest() error {
hash := ctx.Request.Header.Get("X-Amz-Content-Sha256")
if hash == "" {
if ctx.Body == nil {
hash = emptyStringSHA256
} else {
if !aws.IsReaderSeekable(ctx.Body) {
return fmt.Errorf("cannot use unseekable request body %T, for signed request with body", ctx.Body)
}
hashBytes, err := makeSha256Reader(ctx.Body)
if err != nil {
return err
}
hash = hex.EncodeToString(hashBytes)
}
}
ctx.bodyDigest = hash
return nil
}
// isRequestSigned returns if the request is currently signed or presigned
func (ctx *signingCtx) isRequestSigned() bool {
return ctx.Request.Header.Get("Authorization") != ""
}
func hmacSHA256(key []byte, data []byte) []byte {
hash := hmac.New(sha256.New, key)
hash.Write(data)
return hash.Sum(nil)
}
func hashSHA256(data []byte) []byte {
hash := sha256.New()
hash.Write(data)
return hash.Sum(nil)
}
func makeSha256Reader(reader io.ReadSeeker) (hashBytes []byte, err error) {
hash := sha256.New()
start, err := reader.Seek(0, io.SeekCurrent)
if err != nil {
return nil, err
}
defer func() {
// ensure error is return if unable to seek back to start of payload.
_, err = reader.Seek(start, io.SeekStart)
}()
// Use CopyN to avoid allocating the 32KB buffer in io.Copy for bodies
// smaller than 32KB. Fall back to io.Copy if we fail to determine the size.
size, err := aws.SeekerLen(reader)
if err != nil {
_, _ = io.Copy(hash, reader)
} else {
_, _ = io.CopyN(hash, reader, size)
}
return hash.Sum(nil), nil
}
const doubleSpace = " "
// stripExcessSpaces will rewrite the passed in slice's string values to not
// contain multiple side-by-side spaces.
func stripExcessSpaces(vals []string) {
var j, k, l, m, spaces int
for i, str := range vals {
// revive:disable:empty-block
// Trim trailing spaces
for j = len(str) - 1; j >= 0 && str[j] == ' '; j-- {
}
// Trim leading spaces
for k = 0; k < j && str[k] == ' '; k++ {
}
// revive:enable:empty-block
str = str[k : j+1]
// Strip multiple spaces.
j = strings.Index(str, doubleSpace)
if j < 0 {
vals[i] = str
continue
}
buf := []byte(str)
for k, m, l = j, j, len(buf); k < l; k++ {
if buf[k] == ' ' {
if spaces == 0 {
// First space.
buf[m] = buf[k]
m++
}
spaces++
} else {
// End of multiple spaces.
spaces = 0
buf[m] = buf[k]
m++
}
}
vals[i] = string(buf[:m])
}
}
func buildSigningScope(region, service string, dt time.Time) string {
return strings.Join([]string{
formatShortTime(dt),
region,
service,
awsV4Request,
}, "/")
}
func deriveSigningKey(region, service, secretKey string, dt time.Time) []byte {
keyDate := hmacSHA256([]byte("AWS4"+secretKey), []byte(formatShortTime(dt)))
keyRegion := hmacSHA256(keyDate, []byte(region))
keyService := hmacSHA256(keyRegion, []byte(service))
signingKey := hmacSHA256(keyService, []byte(awsV4Request))
return signingKey
}
func formatShortTime(dt time.Time) string {
return dt.UTC().Format(shortTimeFormat)
}
func formatTime(dt time.Time) string {
return dt.UTC().Format(timeFormat)
}