From 3149d958f45fb295f503eeb434b3f91d0ff4debf Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Mon, 17 Nov 2025 06:55:20 -0800
Subject: [PATCH] cmd: add certser

---
 cmd/certser/main.go | 61 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 cmd/certser/main.go

diff --git a/cmd/certser/main.go b/cmd/certser/main.go
new file mode 100644
index 0000000..0416be6
--- /dev/null
+++ b/cmd/certser/main.go
@@ -0,0 +1,61 @@
+package main
+
+import (
+	"crypto/x509"
+	"encoding/hex"
+	"flag"
+	"fmt"
+	"strings"
+
+	"git.wntrmute.dev/kyle/goutils/certlib"
+	"git.wntrmute.dev/kyle/goutils/die"
+)
+
+const (
+	displayInt = iota + 1
+	displayLHex
+	displayUHex
+)
+
+func parseDisplayMode(mode string) int {
+	mode = strings.ToLower(mode)
+	switch mode {
+	case "int":
+		return displayInt
+	case "hex":
+		return displayLHex
+	case "uhex":
+		return displayUHex
+	default:
+		die.With("invalid display mode ", mode)
+	}
+
+	return displayInt
+}
+
+func serialString(cert *x509.Certificate, mode int) string {
+	switch mode {
+	case displayInt:
+		return cert.SerialNumber.String()
+	case displayLHex:
+		return hex.EncodeToString(cert.SerialNumber.Bytes())
+	case displayUHex:
+		return strings.ToUpper(hex.EncodeToString(cert.SerialNumber.Bytes()))
+	default:
+		return cert.SerialNumber.String()
+	}
+}
+
+func main() {
+	displayAs := flag.String("d", "int", "display mode (int, hex, uhex)")
+	flag.Parse()
+
+	displayMode := parseDisplayMode(*displayAs)
+
+	for _, arg := range flag.Args() {
+		cert, err := certlib.LoadCertificate(arg)
+		die.If(err)
+
+		fmt.Printf("%s: %x\n", arg, serialString(cert, displayMode))
+	}
+}