mediocre-go-lib/cmd/totp-proxy/main.go

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package main
/*
totp-proxy is a reverse proxy which implements basic time-based one-time
password (totp) authentication for any website.
It takes in a JSON object which maps usernames to totp secrets (generated at
a site like https://freeotp.github.io/qrcode.html), as well as a url to
proxy requests to. Users are prompted with a basic-auth prompt, and if they
succeed their totp challenge a cookie is set and requests are proxied to the
destination.
*/
import (
"context"
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"net/http"
"net/url"
"time"
"github.com/mediocregopher/mediocre-go-lib/m"
"github.com/mediocregopher/mediocre-go-lib/mcfg"
"github.com/mediocregopher/mediocre-go-lib/mcrypto"
"github.com/mediocregopher/mediocre-go-lib/mctx"
"github.com/mediocregopher/mediocre-go-lib/merr"
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"github.com/mediocregopher/mediocre-go-lib/mhttp"
"github.com/mediocregopher/mediocre-go-lib/mlog"
"github.com/mediocregopher/mediocre-go-lib/mrand"
"github.com/mediocregopher/mediocre-go-lib/mrun"
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"github.com/mediocregopher/mediocre-go-lib/mtime"
"github.com/pquerna/otp/totp"
)
func main() {
cmp := m.RootServiceComponent()
cookieName := mcfg.String(cmp, "cookie-name",
mcfg.ParamDefault("_totp_proxy"),
mcfg.ParamUsage("String to use as the name for cookies"))
cookieTimeout := mcfg.Duration(cmp, "cookie-timeout",
mcfg.ParamDefault(mtime.Duration{1 * time.Hour}),
mcfg.ParamUsage("Timeout for cookies"))
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var userSecrets map[string]string
mcfg.JSON(cmp, "users", &userSecrets,
mcfg.ParamRequired(),
mcfg.ParamUsage("JSON object which maps usernames to their TOTP secret strings"))
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var secret mcrypto.Secret
secretStr := mcfg.String(cmp, "secret",
mcfg.ParamUsage("String used to sign authentication tokens. If one isn't given a new one will be generated on each startup, invalidating all previous tokens."))
mrun.InitHook(cmp, func(context.Context) error {
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if *secretStr == "" {
*secretStr = mrand.Hex(32)
}
mlog.From(cmp).Info("generating secret")
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secret = mcrypto.NewSecret([]byte(*secretStr))
return nil
})
proxyHandler := new(struct{ http.Handler })
proxyURL := mcfg.String(cmp, "dst-url",
mcfg.ParamRequired(),
mcfg.ParamUsage("URL to proxy requests to. Only the scheme and host should be set."))
mrun.InitHook(cmp, func(context.Context) error {
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u, err := url.Parse(*proxyURL)
if err != nil {
return merr.Wrap(err, cmp.Context())
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}
proxyHandler.Handler = mhttp.ReverseProxy(u)
return nil
})
authHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// TODO mlog.FromHTTP?
ctx := r.Context()
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unauthorized := func() {
mlog.From(cmp).Debug("connection is unauthorized")
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w.Header().Add("WWW-Authenticate", "Basic")
w.WriteHeader(http.StatusUnauthorized)
}
authorized := func() {
mlog.From(cmp).Debug("connection is authorized, rewriting cookies")
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sig := mcrypto.SignString(secret, "")
http.SetCookie(w, &http.Cookie{
Name: *cookieName,
Value: sig.String(),
MaxAge: int((*cookieTimeout).Seconds()),
})
proxyHandler.ServeHTTP(w, r)
}
if cookie, _ := r.Cookie(*cookieName); cookie != nil {
mlog.From(cmp).Debug("authenticating with cookie",
mctx.Annotate(ctx, "cookie", cookie.String()))
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var sig mcrypto.Signature
if err := sig.UnmarshalText([]byte(cookie.Value)); err == nil {
err := mcrypto.VerifyString(secret, sig, "")
if err == nil && time.Since(sig.Time()) < (*cookieTimeout).Duration {
authorized()
return
}
}
}
if user, pass, ok := r.BasicAuth(); ok && pass != "" {
mlog.From(cmp).Debug("authenticating with user",
mctx.Annotate(ctx, "user", user))
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if userSecret, ok := userSecrets[user]; ok {
if totp.Validate(pass, userSecret) {
authorized()
return
}
}
}
unauthorized()
})
mhttp.InstListeningServer(cmp, authHandler)
m.Exec(cmp)
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}