Implement AUTH

This patch implements the AUTH SMTP command, using per-domain user databases.

Note that we don't really use or check the validation for anything, this is
just implementing the command itself.

internal/auth/auth_test.go

@@ -0,0 +1,93 @@
+package auth
+
+import (
+	"encoding/base64"
+	"testing"
+	"time"
+
+	"blitiri.com.ar/go/chasquid/internal/userdb"
+)
+
+func TestDecodeResponse(t *testing.T) {
+	// Successful cases. Note we hard-code the response for extra assurance.
+	cases := []struct {
+		response, user, domain, passwd string
+	}{
+		{"dUBkAHVAZABwYXNz", "u", "d", "pass"},     // u@d\0u@d\0pass
+		{"dUBkAABwYXNz", "u", "d", "pass"},         // u@d\0\0pass
+		{"AHVAZABwYXNz", "u", "d", "pass"},         // \0u@d\0pass
+		{"dUBkAABwYXNz/w==", "u", "d", "pass\xff"}, // u@d\0\0pass\xff
+
+		// "ñaca@ñeque\0\0clavaré"
+		{"w7FhY2FAw7FlcXVlAABjbGF2YXLDqQ==", "ñaca", "ñeque", "clavaré"},
+	}
+	for _, c := range cases {
+		u, d, p, err := DecodeResponse(c.response)
+		if err != nil {
+			t.Errorf("Error in case %v: %v", c, err)
+		}
+
+		if u != c.user || d != c.domain || p != c.passwd {
+			t.Errorf("Expected %q %q %q ; got %q %q %q",
+				c.user, c.domain, c.passwd, u, d, p)
+		}
+	}
+
+	_, _, _, err := DecodeResponse("this is not base64 encoded")
+	if err == nil {
+		t.Errorf("invalid base64 did not fail as expected")
+	}
+
+	failedCases := []string{
+		"", "\x00", "\x00\x00", "\x00\x00\x00", "\x00\x00\x00\x00",
+		"a\x00b", "a\x00b\x00c", "a@a\x00b@b\x00pass", "a\x00a\x00pass",
+		"\xffa@b\x00\xffa@b\x00pass",
+	}
+	for _, c := range failedCases {
+		r := base64.StdEncoding.EncodeToString([]byte(c))
+		_, _, _, err := DecodeResponse(r)
+		if err == nil {
+			t.Errorf("Expected case %q to fail, but succeeded", c)
+		} else {
+			t.Logf("OK: %q failed with %v", c, err)
+		}
+	}
+}
+
+func TestAuthenticate(t *testing.T) {
+	db := userdb.New("/dev/null")
+	db.AddUser("user", "password")
+
+	// Test the correct case first
+	ts := time.Now()
+	if !Authenticate(db, "user", "password") {
+		t.Errorf("failed valid authentication for user/password")
+	}
+	if time.Since(ts) < AuthenticateTime {
+		t.Errorf("authentication was too fast")
+	}
+
+	// Incorrect cases.
+	cases := []struct{ user, password string }{
+		{"user", "incorrect"},
+		{"invalid", "p"},
+	}
+	for _, c := range cases {
+		ts = time.Now()
+		if Authenticate(db, c.user, c.password) {
+			t.Errorf("successful auth on %v", c)
+		}
+		if time.Since(ts) < AuthenticateTime {
+			t.Errorf("authentication was too fast")
+		}
+	}
+
+	// And the special case of a nil userdb.
+	ts = time.Now()
+	if Authenticate(nil, "user", "password") {
+		t.Errorf("successful auth on a nil userdb")
+	}
+	if time.Since(ts) < AuthenticateTime {
+		t.Errorf("authentication was too fast")
+	}
+}