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main.go
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main.go
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package main
import (
"bufio"
"bytes"
"crypto/rand"
"crypto/sha256"
"encoding/hex"
"fmt"
"io"
"log"
"net/http"
"os"
"strings"
yaml "gopkg.in/yaml.v2"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/s3"
"gopkg.in/alecthomas/kingpin.v2"
)
var (
app = kingpin.New("s3-basic-auth-proxy", "S3 Basic Auth proxy.")
generateCmd = app.Command("generate", "Generate an example configuration.")
serveCmd = app.Command("serve", "Run the proxy server.")
httpInterface = serveCmd.Flag("addr", "HTTP Server listen address.").Default(":80").String()
configFile = serveCmd.Arg("auth-file", "Authentication file.").Required().File()
hashCmd = app.Command("hash", "Generate a hash and a random salt.")
)
type Config struct {
BufferSize int
Aws struct {
Region string
Bucket string
}
Users map[string]struct {
Hash struct {
Salt string
Sha256 string
}
}
}
const DefaultBufferSize = 1024 * 1024 // 1 MB
func main() {
flagCommand := kingpin.MustParse(app.Parse(os.Args[1:]))
switch flagCommand {
case "generate":
generate()
case "hash":
generateHash()
case "serve":
var buf bytes.Buffer
if _, err := io.Copy(&buf, *configFile); err != nil {
fmt.Println("Could not read configuration file:", err)
os.Exit(1)
}
c := Config{BufferSize: DefaultBufferSize}
if err := yaml.Unmarshal(buf.Bytes(), &c); err != nil {
fmt.Println("Could not parse configuration file:", err)
os.Exit(1)
}
serve(c)
}
}
const SALTLEN = 6
func generateHash() {
var err error
var text string
reader := bufio.NewReader(os.Stdin)
fmt.Print("Enter password: ")
if text, err = reader.ReadString('\n'); err != nil {
fmt.Println("Could not read the password:", err)
os.Exit(1)
}
text = strings.TrimRightFunc(text, func(r rune) bool { return r == '\n' })
data := make([]byte, 6)
if _, err = rand.Read(data); err != nil {
fmt.Println("Could not generate full salt:", err)
os.Exit(1)
}
salt := hex.EncodeToString(data)
fmt.Println("salt:", salt)
fmt.Println("sha256:", calculateSha256(salt, text))
}
func calculateSha256(salt, data string) string {
sum := sha256.Sum256([]byte(salt + data))
a := make([]byte, 32)
copy(a[:], sum[:])
return hex.EncodeToString(a)
}
func generate() {
fmt.Println(strings.Join([]string{
"aws:",
" region: eu-west-1",
" bucket: my-bucket",
"users:",
" erik:",
" password: \"my%secret%password\"",
" peter:",
" # If you want to obfuscate a password, you can put it in here base64-encoded.",
" password: !!binary |",
" aGVqCg==",
" arnold:",
" hash:",
" salt: abcdefg",
" sha256: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824",
}, "\n"))
}
func checkCredentials(c Config, inputUsername, inputPassword string) bool {
for username, userdata := range c.Users {
if username != inputUsername {
continue
}
if calculateSha256(userdata.Hash.Salt, inputPassword) == userdata.Hash.Sha256 {
return true
}
}
return false
}
func serve(c Config) {
awsConfig := aws.Config{
Region: aws.String(c.Aws.Region),
}
s := session.New(&awsConfig)
if _, err := s.Config.Credentials.Get(); err != nil {
fmt.Println("Could not find credentials. Please create: ~/.aws/credentials")
os.Exit(1)
}
service := s3.New(s)
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
var err error
// Authenticate
var username, password string
var ok bool
if username, password, ok = r.BasicAuth(); ok {
ok = checkCredentials(c, username, password)
}
if !ok {
w.Header()["WWW-Authenticate"] = []string{"Basic realm=\"Please enter your username, followed by password.\""}
status := http.StatusUnauthorized
w.WriteHeader(status)
logRequest(r, status, "")
return
}
// Build the S3 request.
request := s3.GetObjectInput{
Bucket: &c.Aws.Bucket,
Key: &r.URL.Path,
}
// TODO: Set cache headers on request.
// Execute the S3 request.
var response *s3.GetObjectOutput
if response, err = service.GetObject(&request); err != nil {
status := http.StatusBadGateway
if awsErr, ok := err.(awserr.RequestFailure); ok {
status = awsErr.StatusCode()
}
logRequest(r, status, err.Error())
http.Error(w, "Error talking to S3.", status)
return
}
defer response.Body.Close()
// Return the response.
// TODO: Write all headers from response to w.
if _, err = io.Copy(bufio.NewWriterSize(w, c.BufferSize), bufio.NewReaderSize(response.Body, c.BufferSize)); err != nil {
status := http.StatusBadGateway
logRequest(r, status, err.Error())
http.Error(w, "Error fetching from S3.", status)
return
}
logRequest(r, http.StatusOK, "")
})
log.Fatal(http.ListenAndServe(*httpInterface, nil))
}
func logRequest(r *http.Request, outcome int, msg string) {
if msg == "" {
msg = "-"
}
log.Println(r.URL.Path, r.RemoteAddr, outcome, msg)
}