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package main
import (
"context"
"crypto/rand"
"encoding/base64"
"encoding/csv"
"flag"
"fmt"
"log"
"math/big"
"net/http"
"net/http/cgi"
"os"
"github.com/casbin/casbin/v2"
"golang.org/x/crypto/bcrypt"
)
var (
reposDir = flag.String("r", "./repos", "Directory containing git repositories")
backendCommand = flag.String("c", "git http-backend", "CGI binary to execute")
addr = flag.String("l", ":8080", "Address/port to listen on")
newToken = flag.Bool("t", false, "make a new token")
)
// LoadTokens load tokens from a csv into a map
func LoadTokens() (map[string]string, error) {
tokenMap := make(map[string]string)
contents, err := os.Open("tokens.csv")
if err != nil {
fmt.Println("File reading error", err)
return tokenMap, err
}
defer contents.Close()
r := csv.NewReader(contents)
tokens, err := r.ReadAll()
if err != nil {
fmt.Println("File reading error", err)
return tokenMap, err
}
for _, acctToken := range tokens {
acct, hash := acctToken[0], acctToken[1]
tokenMap[acct] = hash
}
return tokenMap, err
}
// NewToken generate a new token
func NewToken() (string, string, error) {
tokenBytes := make([]byte, 28)
for i := range tokenBytes {
max := big.NewInt(int64(255))
randInt, err := rand.Int(rand.Reader, max)
if err != nil {
return "", "", err
}
tokenBytes[i] = uint8(randInt.Int64())
}
hashBytes, err := bcrypt.GenerateFromPassword(tokenBytes, bcrypt.DefaultCost)
if err != nil {
return "", "", err
}
token := base64.URLEncoding.EncodeToString(tokenBytes)
hash := string(hashBytes)
return token, hash, nil
}
// GitHttpBackendHandler a handler for git cgi
func GitHttpBackendHandler(reposDir, backendCommand string) http.Handler {
projectDirEnv := fmt.Sprintf("GIT_PROJECT_ROOT=%v", reposDir)
return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
ctx := req.Context()
uid := ctx.Value("urn")
git := &cgi.Handler{
Path: "/bin/sh",
Args: []string{"-c", backendCommand},
Dir: ".",
Env: []string{
projectDirEnv,
"GIT_HTTP_EXPORT_ALL=1",
fmt.Sprintf("REMOTE_USER=%s", uid),
},
}
git.ServeHTTP(rw, req)
})
}
// Authentication middleware to enforce authentication of all requests.
func Authentication(authMap map[string]string, next http.Handler) http.Handler {
return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
u, p, ok := req.BasicAuth()
if !ok {
rw.Header().Set("WWW-Authenticate", `Basic realm="git"`)
http.Error(rw, "Authentication Required", 401)
return
}
urn := fmt.Sprintf("uid:%s", u)
hash, ok := authMap[urn]
if !ok {
http.Error(rw, "Bad Request", 400)
return
}
token, err := base64.URLEncoding.DecodeString(p)
if err != nil {
http.Error(rw, "Bad Request", 400)
return
}
if err := bcrypt.CompareHashAndPassword([]byte(hash), token); err != nil {
http.Error(rw, "Bad Request", 400)
return
}
ctx := context.WithValue(req.Context(), "urn", urn)
next.ServeHTTP(rw, req.WithContext(ctx))
})
}
func Authorization(enf *casbin.Enforcer, next http.Handler) http.Handler {
return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
ctx := req.Context()
urn := ctx.Value("urn")
repo := req.URL.Path
action := req.Method
// defer req.Body.Close()
// body, _ := io.ReadAll(req.Body)
// log.Printf("%s", body)
ok, err := enf.Enforce(urn, repo, action)
if err != nil {
log.Printf("error running enforce %s", err)
http.Error(rw, "Bad Request", http.StatusBadRequest)
}
if !ok {
log.Printf("Access denied")
http.Error(rw, "Access denied", http.StatusUnauthorized)
}
log.Printf("Method %s Url %s", action, repo)
next.ServeHTTP(rw, req.WithContext(ctx))
})
}
func main() {
enf, _ := casbin.NewEnforcer("./auth_model.ini", "./policy.csv")
flag.Parse()
if *newToken {
token, hash, err := NewToken()
if err != nil {
log.Fatal(err)
}
fmt.Printf("token: %s\nhash: %s\n", token, hash)
return
}
tokens, err := LoadTokens()
if err != nil {
log.Fatal(err)
}
router := http.NewServeMux()
// TODO we don't want to use a global
// de-reference args
router.Handle("/", GitHttpBackendHandler(*reposDir, *backendCommand))
mux := Authentication(tokens, Authorization(enf, router))
log.Fatal(http.ListenAndServe(":8080", mux))
}
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