From 5a641ceca19cb43a37b990c8ea16e8e071dd91ba Mon Sep 17 00:00:00 2001
From: Drew DeVault <sir@cmpwn.com>
Date: Mon, 21 Feb 2022 10:55:02 +0100
Subject: [PATCH] Implement IMAP auth provider

---
 auth/imap.go         | 66 ++++++++++++++++++++++++++++++++++++++++++++
 auth/interface.go    | 11 ++++++++
 auth/middleware.go   |  0
 auth/postgresql.go   |  0
 cmd/tokidoki/main.go |  6 ++++
 go.mod               |  7 ++++-
 go.sum               | 11 ++++++++
 7 files changed, 100 insertions(+), 1 deletion(-)
 delete mode 100644 auth/middleware.go
 delete mode 100644 auth/postgresql.go

diff --git a/auth/imap.go b/auth/imap.go
index e69de29..71fb1ae 100644
--- a/auth/imap.go
+++ b/auth/imap.go
@@ -0,0 +1,66 @@
+package auth
+
+import (
+	"log"
+	"net/http"
+
+	"github.com/emersion/go-imap/client"
+	"github.com/emersion/go-sasl"
+)
+
+type IMAPProvider struct {
+	addr string
+	tls  bool
+}
+
+// Initializes a new IMAP auth provider with the given connection string.
+func NewIMAP(addr string, tls bool) AuthProvider {
+	prov := &IMAPProvider{addr, tls}
+	conn, err := prov.dial()
+	if err != nil {
+		log.Fatalf("Error dialing configured IMAP auth server: %s", err.Error())
+	}
+	conn.Close()
+	return prov
+}
+
+func (prov *IMAPProvider) Middleware() func(http.Handler) http.Handler {
+	return func (next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			prov.doAuth(next, w, r)
+		})
+	}
+}
+
+func (prov *IMAPProvider) doAuth(next http.Handler,
+	w http.ResponseWriter, r *http.Request) {
+	user, pass, ok := r.BasicAuth()
+	if !ok {
+		w.Header().Add("WWW-Authenticate", `Basic realm="Please provide your IMAP credentials", charset="UTF-8"`)
+		http.Error(w, "HTTP Basic auth is required", http.StatusUnauthorized)
+		return
+	}
+
+	conn, err := prov.dial()
+	if err != nil {
+		http.Error(w, "Temporary authentication error, try again later", http.StatusServiceUnavailable)
+		return
+	}
+	defer conn.Close()
+
+	auth := sasl.NewPlainClient("", user, pass)
+	if err := conn.Authenticate(auth); err != nil {
+		http.Error(w, "Invalid username or password", http.StatusUnauthorized)
+		return
+	}
+
+	next.ServeHTTP(w, r)
+}
+
+func (prov *IMAPProvider) dial() (*client.Client, error) {
+	if prov.tls {
+		return client.DialTLS(prov.addr, nil)
+	} else {
+		return client.Dial(prov.addr)
+	}
+}
diff --git a/auth/interface.go b/auth/interface.go
index e69de29..39b3d03 100644
--- a/auth/interface.go
+++ b/auth/interface.go
@@ -0,0 +1,11 @@
+package auth
+
+import (
+	"net/http"
+)
+
+// Abstracts the authentication backend for the server.
+type AuthProvider interface {
+	// Returns HTTP middleware for performing authentication.
+	Middleware() func(http.Handler) http.Handler
+}
diff --git a/auth/middleware.go b/auth/middleware.go
deleted file mode 100644
index e69de29..0000000
diff --git a/auth/postgresql.go b/auth/postgresql.go
deleted file mode 100644
index e69de29..0000000
diff --git a/cmd/tokidoki/main.go b/cmd/tokidoki/main.go
index 3279797..0d4de38 100644
--- a/cmd/tokidoki/main.go
+++ b/cmd/tokidoki/main.go
@@ -8,6 +8,8 @@ import (
 	
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
+
+	"git.sr.ht/~sircmpwn/tokidoki/auth"
 )
 
 func main() {
@@ -25,6 +27,10 @@ func main() {
 	mux := chi.NewRouter()
 	mux.Use(middleware.Logger)
 
+	// TODO: Configurable
+	authProvider := auth.NewIMAP("imap.migadu.com:993", true)
+	mux.Use(authProvider.Middleware())
+
 	mux.Get("/", func (w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("Hello world!\n"))
 	})
diff --git a/go.mod b/go.mod
index 788df4c..a516366 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,9 @@ module git.sr.ht/~sircmpwn/tokidoki
 
 go 1.17
 
-require github.com/go-chi/chi/v5 v5.0.7 // indirect
+require (
+	github.com/emersion/go-imap v1.2.0 // indirect
+	github.com/emersion/go-sasl v0.0.0-20211008083017-0b9dcfb154ac // indirect
+	github.com/go-chi/chi/v5 v5.0.7 // indirect
+	golang.org/x/text v0.3.7 // indirect
+)
diff --git a/go.sum b/go.sum
index 433d671..5086cd8 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,13 @@
+github.com/emersion/go-imap v1.2.0 h1:lyUQ3+EVM21/qbWE/4Ya5UG9r5+usDxlg4yfp3TgHFA=
+github.com/emersion/go-imap v1.2.0/go.mod h1:Qlx1FSx2FTxjnjWpIlVNEuX+ylerZQNFE5NsmKFSejY=
+github.com/emersion/go-message v0.15.0/go.mod h1:wQUEfE+38+7EW8p8aZ96ptg6bAb1iwdgej19uXASlE4=
+github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
+github.com/emersion/go-sasl v0.0.0-20211008083017-0b9dcfb154ac h1:tn/OQ2PmwQ0XFVgAHfjlLyqMewry25Rz7jWnVoh4Ggs=
+github.com/emersion/go-sasl v0.0.0-20211008083017-0b9dcfb154ac/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
+github.com/emersion/go-textwrapper v0.0.0-20200911093747-65d896831594/go.mod h1:aqO8z8wPrjkscevZJFVE1wXJrLpC5LtJG7fqLOsPb2U=
 github.com/go-chi/chi/v5 v5.0.7 h1:rDTPXLDHGATaeHvVlLcR4Qe0zftYethFucbjVQ1PxU8=
 github.com/go-chi/chi/v5 v5.0.7/go.mod h1:DslCQbL2OYiznFReuXYUmQ2hGd1aDpCnlMNITLSKoi8=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
+golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=