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// 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
package auth
import (
"bytes"
"context"
"crypto/rand"
"encoding/base64"
"errors"
"fmt"
"net/http"
"strings"
"time"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/bson/primitive"
"go.mongodb.org/mongo-driver/internal/aws/credentials"
v4signer "go.mongodb.org/mongo-driver/internal/aws/signer/v4"
"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
)
type clientState int
const (
clientStarting clientState = iota
clientFirst
clientFinal
clientDone
)
type awsConversation struct {
state clientState
valid bool
nonce []byte
credentials *credentials.Credentials
}
type serverMessage struct {
Nonce primitive.Binary `bson:"s"`
Host string `bson:"h"`
}
const (
amzDateFormat = "20060102T150405Z"
defaultRegion = "us-east-1"
maxHostLength = 255
responceNonceLength = 64
)
// Step takes a string provided from a server (or just an empty string for the
// very first conversation step) and attempts to move the authentication
// conversation forward. It returns a string to be sent to the server or an
// error if the server message is invalid. Calling Step after a conversation
// completes is also an error.
func (ac *awsConversation) Step(challenge []byte) (response []byte, err error) {
switch ac.state {
case clientStarting:
ac.state = clientFirst
response = ac.firstMsg()
case clientFirst:
ac.state = clientFinal
response, err = ac.finalMsg(challenge)
case clientFinal:
ac.state = clientDone
ac.valid = true
default:
response, err = nil, errors.New("Conversation already completed")
}
return
}
// Done returns true if the conversation is completed or has errored.
func (ac *awsConversation) Done() bool {
return ac.state == clientDone
}
// Valid returns true if the conversation successfully authenticated with the
// server, including counter-validation that the server actually has the
// user's stored credentials.
func (ac *awsConversation) Valid() bool {
return ac.valid
}
func getRegion(host string) (string, error) {
region := defaultRegion
if len(host) == 0 {
return "", errors.New("invalid STS host: empty")
}
if len(host) > maxHostLength {
return "", errors.New("invalid STS host: too large")
}
// The implicit region for sts.amazonaws.com is us-east-1
if host == "sts.amazonaws.com" {
return region, nil
}
if strings.HasPrefix(host, ".") || strings.HasSuffix(host, ".") || strings.Contains(host, "..") {
return "", errors.New("invalid STS host: empty part")
}
// If the host has multiple parts, the second part is the region
parts := strings.Split(host, ".")
if len(parts) >= 2 {
region = parts[1]
}
return region, nil
}
func (ac *awsConversation) firstMsg() []byte {
// Values are cached for use in final message parameters
ac.nonce = make([]byte, 32)
_, _ = rand.Read(ac.nonce)
idx, msg := bsoncore.AppendDocumentStart(nil)
msg = bsoncore.AppendInt32Element(msg, "p", 110)
msg = bsoncore.AppendBinaryElement(msg, "r", 0x00, ac.nonce)
msg, _ = bsoncore.AppendDocumentEnd(msg, idx)
return msg
}
func (ac *awsConversation) finalMsg(s1 []byte) ([]byte, error) {
var sm serverMessage
err := bson.Unmarshal(s1, &sm)
if err != nil {
return nil, err
}
// Check nonce prefix
if sm.Nonce.Subtype != 0x00 {
return nil, errors.New("server reply contained unexpected binary subtype")
}
if len(sm.Nonce.Data) != responceNonceLength {
return nil, fmt.Errorf("server reply nonce was not %v bytes", responceNonceLength)
}
if !bytes.HasPrefix(sm.Nonce.Data, ac.nonce) {
return nil, errors.New("server nonce did not extend client nonce")
}
region, err := getRegion(sm.Host)
if err != nil {
return nil, err
}
creds, err := ac.credentials.GetWithContext(context.Background())
if err != nil {
return nil, err
}
currentTime := time.Now().UTC()
body := "Action=GetCallerIdentity&Version=2011-06-15"
// Create http.Request
req, _ := http.NewRequest("POST", "/", strings.NewReader(body))
req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
req.Header.Set("Content-Length", "43")
req.Host = sm.Host
req.Header.Set("X-Amz-Date", currentTime.Format(amzDateFormat))
if len(creds.SessionToken) > 0 {
req.Header.Set("X-Amz-Security-Token", creds.SessionToken)
}
req.Header.Set("X-MongoDB-Server-Nonce", base64.StdEncoding.EncodeToString(sm.Nonce.Data))
req.Header.Set("X-MongoDB-GS2-CB-Flag", "n")
// Create signer with credentials
signer := v4signer.NewSigner(ac.credentials)
// Get signed header
_, err = signer.Sign(req, strings.NewReader(body), "sts", region, currentTime)
if err != nil {
return nil, err
}
// create message
idx, msg := bsoncore.AppendDocumentStart(nil)
msg = bsoncore.AppendStringElement(msg, "a", req.Header.Get("Authorization"))
msg = bsoncore.AppendStringElement(msg, "d", req.Header.Get("X-Amz-Date"))
if len(creds.SessionToken) > 0 {
msg = bsoncore.AppendStringElement(msg, "t", creds.SessionToken)
}
msg, _ = bsoncore.AppendDocumentEnd(msg, idx)
return msg, nil
}
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