cmd: add certser command.

.golangci.yml

@@ -12,6 +12,12 @@
 
 version: "2"
 
+output:
+  sort-order:
+    - file
+    - linter
+    - severity
+
 issues:
   # Maximum count of issues with the same text.
   # Set to 0 to disable.
@@ -454,6 +460,8 @@ linters:
         - -QF1008
         # We often explicitly enable old/deprecated ciphers for research.
         - -SA1019
+        # Covered by revive.
+        - -ST1003
 
     usetesting:
       # Enable/disable `os.TempDir()` detections.
@@ -472,6 +480,8 @@ linters:
     rules:
       - path: 'ahash/ahash.go'
         linters: [ staticcheck, gosec ]
+      - path: 'twofactor/.*.go'
+        linters: [ exhaustive, mnd, revive ]
       - path: 'backoff/backoff_test.go'
         linters: [ testpackage ]
       - path: 'dbg/dbg_test.go'

CHANGELOG

@@ -1,5 +1,31 @@
 CHANGELOG
 
+v1.13.0 - 2025-11-16
+
+Add:
+- cmd/certser: print serial numbers for certificates.
+- lib/HexEncode: add a new hex encode function handling multiple output
+  formats, including with and without colons.
+
+v1.12.4 - 2025-11-16
+
+Changed:
+
+- Linting fixes for twofactor that were previously masked.
+
+v1.12.3 erroneously tagged and pushed
+
+v1.12.2 - 2025-11-16
+
+Changed:
+
+- add rsc.io/qr dependency for twofactor.
+
+v1.12.1 - 2025-11-16
+
+Changed:
+- twofactor: Remove go.{mod,sum}.
+
 v1.12.0 - 2025-11-16
 
 Added

cmd/certser/main.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"crypto/x509"
+	"flag"
+	"fmt"
+	"strings"
+
+	"git.wntrmute.dev/kyle/goutils/certlib"
+	"git.wntrmute.dev/kyle/goutils/die"
+	"git.wntrmute.dev/kyle/goutils/lib"
+)
+
+const displayInt lib.HexEncodeMode = iota
+
+func parseDisplayMode(mode string) lib.HexEncodeMode {
+	mode = strings.ToLower(mode)
+
+	if mode == "int" {
+		return displayInt
+	}
+
+	return lib.ParseHexEncodeMode(mode)
+}
+
+func serialString(cert *x509.Certificate, mode lib.HexEncodeMode) string {
+	if mode == displayInt {
+		return cert.SerialNumber.String()
+	}
+
+	return lib.HexEncode(cert.SerialNumber.Bytes(), mode)
+}
+
+func main() {
+	displayAs := flag.String("d", "int", "display mode (int, hex, uhex)")
+	showExpiry := flag.Bool("e", false, "show expiry date")
+	flag.Parse()
+
+	displayMode := parseDisplayMode(*displayAs)
+
+	for _, arg := range flag.Args() {
+		cert, err := certlib.LoadCertificate(arg)
+		die.If(err)
+
+		fmt.Printf("%s: %s", arg, serialString(cert, displayMode))
+		if *showExpiry {
+			fmt.Printf(" (%s)", cert.NotAfter.Format("2006-01-02"))
+		}
+		fmt.Println()
+	}
+}

go.mod

@@ -22,4 +22,5 @@ require (
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
+	rsc.io/qr v0.2.0 // indirect
 )

go.sum

@@ -44,3 +44,5 @@ gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+rsc.io/qr v0.2.0 h1:6vBLea5/NRMVTz8V66gipeLycZMl/+UlFmk8DvqQ6WY=
+rsc.io/qr v0.2.0/go.mod h1:IF+uZjkb9fqyeF/4tlBoynqmQxUoPfWEKh921coOuXs=

lib/lib.go

@@ -2,9 +2,11 @@
 package lib
 
 import (
+	"encoding/hex"
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 )
 
@@ -109,3 +111,111 @@ func Duration(d time.Duration) string {
 	s += fmt.Sprintf("%dh%s", hours, d)
 	return s
 }
+
+type HexEncodeMode uint8
+
+const (
+	// HexEncodeLower prints the bytes as lowercase hexadecimal.
+	HexEncodeLower HexEncodeMode = iota + 1
+	// HexEncodeUpper prints the bytes as uppercase hexadecimal.
+	HexEncodeUpper
+	// HexEncodeLowerColon prints the bytes as lowercase hexadecimal
+	// with colons between each pair of bytes.
+	HexEncodeLowerColon
+	// HexEncodeUpperColon prints the bytes as uppercase hexadecimal
+	// with colons between each pair of bytes.
+	HexEncodeUpperColon
+)
+
+func (m HexEncodeMode) String() string {
+	switch m {
+	case HexEncodeLower:
+		return "lower"
+	case HexEncodeUpper:
+		return "upper"
+	case HexEncodeLowerColon:
+		return "lcolon"
+	case HexEncodeUpperColon:
+		return "ucolon"
+	default:
+		panic("invalid hex encode mode")
+	}
+}
+
+func ParseHexEncodeMode(s string) HexEncodeMode {
+	switch strings.ToLower(s) {
+	case "lower":
+		return HexEncodeLower
+	case "upper":
+		return HexEncodeUpper
+	case "lcolon":
+		return HexEncodeLowerColon
+	case "ucolon":
+		return HexEncodeUpperColon
+	}
+
+	panic("invalid hex encode mode")
+}
+
+func hexColons(s string) string {
+	if len(s)%2 != 0 {
+		fmt.Fprintf(os.Stderr, "hex string: %s\n", s)
+		fmt.Fprintf(os.Stderr, "hex length: %d\n", len(s))
+		panic("invalid hex string length")
+	}
+
+	n := len(s)
+	if n <= 2 {
+		return s
+	}
+
+	pairCount := n / 2
+	if n%2 != 0 {
+		pairCount++
+	}
+
+	var b strings.Builder
+	b.Grow(n + pairCount - 1)
+
+	for i := 0; i < n; i += 2 {
+		b.WriteByte(s[i])
+
+		if i+1 < n {
+			b.WriteByte(s[i+1])
+		}
+
+		if i+2 < n {
+			b.WriteByte(':')
+		}
+	}
+
+	return b.String()
+}
+
+func hexEncode(b []byte) string {
+	s := hex.EncodeToString(b)
+
+	if len(s)%2 != 0 {
+		s = "0" + s
+	}
+
+	return s
+}
+
+// HexEncode encodes the given bytes as a hexadecimal string.
+func HexEncode(b []byte, mode HexEncodeMode) string {
+	str := hexEncode(b)
+
+	switch mode {
+	case HexEncodeLower:
+		return str
+	case HexEncodeUpper:
+		return strings.ToUpper(str)
+	case HexEncodeLowerColon:
+		return hexColons(str)
+	case HexEncodeUpperColon:
+		return strings.ToUpper(hexColons(str))
+	default:
+		panic("invalid hex encode mode")
+	}
+}

lib/lib_test.go

@@ -0,0 +1,79 @@
+package lib_test
+
+import (
+	"testing"
+
+	"git.wntrmute.dev/kyle/goutils/lib"
+)
+
+func TestHexEncode_LowerUpper(t *testing.T) {
+	b := []byte{0x0f, 0xa1, 0x00, 0xff}
+
+	gotLower := lib.HexEncode(b, lib.HexEncodeLower)
+	if gotLower != "0fa100ff" {
+		t.Fatalf("lib.HexEncode lower: expected %q, got %q", "0fa100ff", gotLower)
+	}
+
+	gotUpper := lib.HexEncode(b, lib.HexEncodeUpper)
+	if gotUpper != "0FA100FF" {
+		t.Fatalf("lib.HexEncode upper: expected %q, got %q", "0FA100FF", gotUpper)
+	}
+}
+
+func TestHexEncode_ColonModes(t *testing.T) {
+	// Includes leading zero nibble and a zero byte to verify padding and separators
+	b := []byte{0x0f, 0xa1, 0x00, 0xff}
+
+	gotLColon := lib.HexEncode(b, lib.HexEncodeLowerColon)
+	if gotLColon != "0f:a1:00:ff" {
+		t.Fatalf("lib.HexEncode colon lower: expected %q, got %q", "0f:a1:00:ff", gotLColon)
+	}
+
+	gotUColon := lib.HexEncode(b, lib.HexEncodeUpperColon)
+	if gotUColon != "0F:A1:00:FF" {
+		t.Fatalf("lib.HexEncode colon upper: expected %q, got %q", "0F:A1:00:FF", gotUColon)
+	}
+}
+
+func TestHexEncode_EmptyInput(t *testing.T) {
+	var b []byte
+	if got := lib.HexEncode(b, lib.HexEncodeLower); got != "" {
+		t.Fatalf("empty lower: expected empty string, got %q", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpper); got != "" {
+		t.Fatalf("empty upper: expected empty string, got %q", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeLowerColon); got != "" {
+		t.Fatalf("empty colon lower: expected empty string, got %q", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpperColon); got != "" {
+		t.Fatalf("empty colon upper: expected empty string, got %q", got)
+	}
+}
+
+func TestHexEncode_SingleByte(t *testing.T) {
+	b := []byte{0x0f}
+	if got := lib.HexEncode(b, lib.HexEncodeLower); got != "0f" {
+		t.Fatalf("single byte lower: expected %q, got %q", "0f", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpper); got != "0F" {
+		t.Fatalf("single byte upper: expected %q, got %q", "0F", got)
+	}
+	// For a single byte, colon modes should not introduce separators
+	if got := lib.HexEncode(b, lib.HexEncodeLowerColon); got != "0f" {
+		t.Fatalf("single byte colon lower: expected %q, got %q", "0f", got)
+	}
+	if got := lib.HexEncode(b, lib.HexEncodeUpperColon); got != "0F" {
+		t.Fatalf("single byte colon upper: expected %q, got %q", "0F", got)
+	}
+}
+
+func TestHexEncode_InvalidModePanics(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expected panic for invalid mode, but function returned normally")
+		}
+	}()
+	// 0 is not a valid lib.HexEncodeMode (valid modes start at 1)
+	_ = lib.HexEncode([]byte{0x01}, lib.HexEncodeMode(0))
+}

twofactor/.circleci/config.yml

@@ -1,42 +0,0 @@
-# Use the latest 2.1 version of CircleCI pipeline process engine.
-# See: https://circleci.com/docs/2.0/configuration-reference
-version: 2.1
-
-# Define a job to be invoked later in a workflow.
-# See: https://circleci.com/docs/2.0/configuration-reference/#jobs
-jobs:
-  testbuild:
-    working_directory: ~/repo
-    # Specify the execution environment. You can specify an image from Dockerhub or use one of our Convenience Images from CircleCI's Developer Hub.
-    # See: https://circleci.com/docs/2.0/configuration-reference/#docker-machine-macos-windows-executor
-    docker:
-      - image: cimg/go:1.22.2
-    # Add steps to the job
-    # See: https://circleci.com/docs/2.0/configuration-reference/#steps
-    steps:
-      - checkout
-      - restore_cache:
-          keys:
-            - go-mod-v4-{{ checksum "go.sum" }}
-      - run:
-          name: Install Dependencies
-          command: go mod download
-      - save_cache:
-          key: go-mod-v4-{{ checksum "go.sum" }}
-          paths:
-            - "/go/pkg/mod"
-      - run:
-          name: Run tests
-          command: go test ./...
-      - run:
-          name: Run build
-          command: go build ./...
-      - store_test_results:
-          path: /tmp/test-reports
-
-# Invoke jobs via workflows
-# See: https://circleci.com/docs/2.0/configuration-reference/#workflows
-workflows:
-  testbuild:
-    jobs:
-      - testbuild

twofactor/LICENSE

@@ -1,19 +0,0 @@
-Copyright (c) 2017 Kyle Isom <kyle@imap.cc>
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.

twofactor/doc.go

@@ -1,4 +1,4 @@
-// twofactor implements two-factor authentication.
+// Package twofactor implements two-factor authentication.
 //
 // Currently supported are RFC 4226 HOTP one-time passwords and
 // RFC 6238 TOTP SHA-1 one-time passwords.

twofactor/go.mod

@@ -1,8 +0,0 @@
-module github.com/gokyle/twofactor
-
-go 1.14
-
-require (
-	github.com/benbjohnson/clock v0.0.0-20161215174838-7dc76406b6d3
-	rsc.io/qr v0.1.0
-)

twofactor/go.sum

@@ -1,4 +0,0 @@
-github.com/benbjohnson/clock v0.0.0-20161215174838-7dc76406b6d3 h1:wOysYcIdqv3WnvwqFFzrYCFALPED7qkUGaLXu359GSc=
-github.com/benbjohnson/clock v0.0.0-20161215174838-7dc76406b6d3/go.mod h1:UMqtWQTnOe4byzwe7Zhwh8f8s+36uszN51sJrSIZlTE=
-rsc.io/qr v0.1.0 h1:M/sAxsU2J5mlQ4W84Bxga2EgdQqOaAliipcjPmMUM5Q=
-rsc.io/qr v0.1.0/go.mod h1:IF+uZjkb9fqyeF/4tlBoynqmQxUoPfWEKh921coOuXs=

twofactor/hotp.go

@@ -2,7 +2,7 @@ package twofactor
 
 import (
 	"crypto"
-	"crypto/sha1"
+	"crypto/sha1" // #nosec G505 - required by RFC
 	"encoding/base32"
 	"io"
 	"net/url"
@@ -15,11 +15,6 @@ type HOTP struct {
 	*OATH
 }
 
-// Type returns OATH_HOTP.
-func (otp *HOTP) Type() Type {
-	return OATH_HOTP
-}
-
 // NewHOTP takes the key, the initial counter value, and the number
 // of digits (typically 6 or 8) and returns a new HOTP instance.
 func NewHOTP(key []byte, counter uint64, digits int) *HOTP {
@@ -34,6 +29,11 @@ func NewHOTP(key []byte, counter uint64, digits int) *HOTP {
 	}
 }
 
+// Type returns OATH_HOTP.
+func (otp *HOTP) Type() Type {
+	return OATH_HOTP
+}
+
 // OTP returns the next OTP and increments the counter.
 func (otp *HOTP) OTP() string {
 	code := otp.OATH.OTP(otp.counter)
@@ -79,7 +79,7 @@ func hotpFromURL(u *url.URL) (*HOTP, string, error) {
 		digits = int(tmpDigits)
 	}
 
-	var counter uint64 = 0
+	var counter uint64
 	if scounter := v.Get("counter"); scounter != "" {
 		var err error
 		counter, err = strconv.ParseUint(scounter, 10, 64)

twofactor/hotp_internal_test.go

@@ -1,7 +1,6 @@
 package twofactor
 
 import (
-	"fmt"
 	"testing"
 )
 
@@ -25,22 +24,19 @@ var rfcHotpExpected = []string{
 // ensures that this implementation is in compliance.
 func TestHotpRFC(t *testing.T) {
 	otp := NewHOTP(rfcHotpKey, 0, 6)
-	for i := 0; i < len(rfcHotpExpected); i++ {
+	for i := range rfcHotpExpected {
 		if otp.Counter() != uint64(i) {
-			fmt.Printf("twofactor: invalid counter (should be %d, is %d",
+			t.Fatalf("twofactor: invalid counter (should be %d, is %d",
 				i, otp.Counter())
-			t.FailNow()
 		}
 		code := otp.OTP()
 		if code == "" {
-			fmt.Printf("twofactor: failed to produce an OTP\n")
-			t.FailNow()
+			t.Fatal("twofactor: failed to produce an OTP")
 		} else if code != rfcHotpExpected[i] {
-			fmt.Printf("twofactor: invalid OTP\n")
-			fmt.Printf("\tExpected: %s\n", rfcHotpExpected[i])
-			fmt.Printf("\t  Actual: %s\n", code)
-			fmt.Printf("\t Counter: %d\n", otp.counter)
-			t.FailNow()
+			t.Logf("twofactor: invalid OTP\n")
+			t.Logf("\tExpected: %s\n", rfcHotpExpected[i])
+			t.Logf("\t  Actual: %s\n", code)
+			t.Fatalf("\t Counter: %d\n", otp.counter)
 		}
 	}
 }
@@ -50,15 +46,13 @@ func TestHotpRFC(t *testing.T) {
 // expected.
 func TestHotpBadRFC(t *testing.T) {
 	otp := NewHOTP(testKey, 0, 6)
-	for i := 0; i < len(rfcHotpExpected); i++ {
+	for i := range rfcHotpExpected {
 		code := otp.OTP()
 		switch code {
 		case "":
-			fmt.Printf("twofactor: failed to produce an OTP\n")
-			t.FailNow()
+			t.Error("twofactor: failed to produce an OTP")
 		case rfcHotpExpected[i]:
-			fmt.Printf("twofactor: should not have received a valid OTP\n")
-			t.FailNow()
+			t.Error("twofactor: should not have received a valid OTP")
 		}
 	}
 }

twofactor/oath.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"hash"
 	"net/url"
+	"strconv"
 
 	"rsc.io/qr"
 )
@@ -25,12 +26,12 @@ type OATH struct {
 }
 
 // Size returns the output size (in characters) of the password.
-func (o OATH) Size() int {
+func (o *OATH) Size() int {
 	return o.size
 }
 
 // Counter returns the OATH token's counter.
-func (o OATH) Counter() uint64 {
+func (o *OATH) Counter() uint64 {
 	return o.counter
 }
 
@@ -40,18 +41,18 @@ func (o *OATH) SetCounter(counter uint64) {
 }
 
 // Key returns the token's secret key.
-func (o OATH) Key() []byte {
-	return o.key[:]
+func (o *OATH) Key() []byte {
+	return o.key
 }
 
 // Hash returns the token's hash function.
-func (o OATH) Hash() func() hash.Hash {
+func (o *OATH) Hash() func() hash.Hash {
 	return o.hash
 }
 
 // URL constructs a URL appropriate for the token (i.e. for use in a
 // QR code).
-func (o OATH) URL(t Type, label string) string {
+func (o *OATH) URL(t Type, label string) string {
 	secret := base32.StdEncoding.EncodeToString(o.key)
 	u := url.URL{}
 	v := url.Values{}
@@ -65,10 +66,10 @@ func (o OATH) URL(t Type, label string) string {
 	u.Path = label
 	v.Add("secret", secret)
 	if o.Counter() != 0 && t == OATH_HOTP {
-		v.Add("counter", fmt.Sprintf("%d", o.Counter()))
+		v.Add("counter", strconv.FormatUint(o.Counter(), 10))
 	}
 	if o.Size() != defaultSize {
-		v.Add("digits", fmt.Sprintf("%d", o.Size()))
+		v.Add("digits", strconv.Itoa(o.Size()))
 	}
 
 	switch o.algo {
@@ -84,7 +85,6 @@ func (o OATH) URL(t Type, label string) string {
 
 	u.RawQuery = v.Encode()
 	return u.String()
-
 }
 
 var digits = []int64{
@@ -101,10 +101,10 @@ var digits = []int64{
 	10: 10000000000,
 }
 
-// The top-level type should provide a counter; for example, HOTP
+// OTP top-level type should provide a counter; for example, HOTP
 // will provide the counter directly while TOTP will provide the
 // time-stepped counter.
-func (o OATH) OTP(counter uint64) string {
+func (o *OATH) OTP(counter uint64) string {
 	var ctr [8]byte
 	binary.BigEndian.PutUint64(ctr[:], counter)
 
@@ -140,7 +140,7 @@ func truncate(in []byte) int64 {
 
 // QR generates a byte slice containing the a QR code encoded as a
 // PNG with level Q error correction.
-func (o OATH) QR(t Type, label string) ([]byte, error) {
+func (o *OATH) QR(t Type, label string) ([]byte, error) {
 	u := o.URL(t, label)
 	code, err := qr.Encode(u, qr.Q)
 	if err != nil {

twofactor/oath_internal_test.go

@@ -1,7 +1,6 @@
 package twofactor
 
 import (
-	"fmt"
 	"testing"
 )
 
@@ -17,14 +16,12 @@ var truncExpect int64 = 0x50ef7f19
 // This test runs through the truncation example given in the RFC.
 func TestTruncate(t *testing.T) {
 	if result := truncate(sha1Hmac); result != truncExpect {
-		fmt.Printf("hotp: expected truncate -> %d, saw %d\n",
+		t.Fatalf("hotp: expected truncate -> %d, saw %d\n",
 			truncExpect, result)
-		t.FailNow()
 	}
 
 	sha1Hmac[19]++
 	if result := truncate(sha1Hmac); result == truncExpect {
-		fmt.Println("hotp: expected truncation to fail")
-		t.FailNow()
+		t.Fatal("hotp: expected truncation to fail")
 	}
 }

twofactor/otp.go

@@ -24,7 +24,7 @@ var (
 	ErrInvalidAlgo = errors.New("twofactor: invalid algorithm")
 )
 
-// Type OTP represents a one-time password token -- whether a
+// OTP represents a one-time password token -- whether a
 // software taken (as in the case of Google Authenticator) or a
 // hardware token (as in the case of a YubiKey).
 type OTP interface {
@@ -65,8 +65,8 @@ func otpString(otp OTP) string {
 }
 
 // FromURL constructs a new OTP token from a URL string.
-func FromURL(URL string) (OTP, string, error) {
-	u, err := url.Parse(URL)
+func FromURL(otpURL string) (OTP, string, error) {
+	u, err := url.Parse(otpURL)
 	if err != nil {
 		return nil, "", err
 	}

twofactor/otp_internal_test.go

@@ -1,7 +1,6 @@
 package twofactor
 
 import (
-	"fmt"
 	"io"
 	"testing"
 )
@@ -10,8 +9,7 @@ func TestHOTPString(t *testing.T) {
 	hotp := NewHOTP(nil, 0, 6)
 	hotpString := otpString(hotp)
 	if hotpString != "OATH-HOTP, 6" {
-		fmt.Println("twofactor: invalid OTP string")
-		t.FailNow()
+		t.Fatal("twofactor: invalid OTP string")
 	}
 }
 
@@ -23,35 +21,32 @@ func TestURL(t *testing.T) {
 	otp := NewHOTP(testKey, 0, 6)
 	url := otp.URL("testuser@foo")
 	otp2, id, err := FromURL(url)
-	if err != nil {
-		fmt.Printf("hotp: failed to parse HOTP URL\n")
-		t.FailNow()
-	} else if id != ident {
-		fmt.Printf("hotp: bad label\n")
-		fmt.Printf("\texpected: %s\n", ident)
-		fmt.Printf("\t  actual: %s\n", id)
-		t.FailNow()
-	} else if otp2.Counter() != otp.Counter() {
-		fmt.Printf("hotp: OTP counters aren't synced\n")
-		fmt.Printf("\toriginal: %d\n", otp.Counter())
-		fmt.Printf("\t  second: %d\n", otp2.Counter())
-		t.FailNow()
+	switch {
+	case err != nil:
+		t.Fatal("hotp: failed to parse HOTP URL\n")
+	case id != ident:
+		t.Logf("hotp: bad label\n")
+		t.Logf("\texpected: %s\n", ident)
+		t.Fatalf("\t  actual: %s\n", id)
+	case otp2.Counter() != otp.Counter():
+		t.Logf("hotp: OTP counters aren't synced\n")
+		t.Logf("\toriginal: %d\n", otp.Counter())
+		t.Fatalf("\t  second: %d\n", otp2.Counter())
 	}
 
 	code1 := otp.OTP()
 	code2 := otp2.OTP()
 	if code1 != code2 {
-		fmt.Printf("hotp: mismatched OTPs\n")
-		fmt.Printf("\texpected: %s\n", code1)
-		fmt.Printf("\t  actual: %s\n", code2)
+		t.Logf("hotp: mismatched OTPs\n")
+		t.Logf("\texpected: %s\n", code1)
+		t.Fatalf("\t  actual: %s\n", code2)
 	}
 
 	// There's not much we can do test the QR code, except to
 	// ensure it doesn't fail.
 	_, err = otp.QR(ident)
 	if err != nil {
-		fmt.Printf("hotp: failed to generate QR code PNG (%v)\n", err)
-		t.FailNow()
+		t.Fatalf("hotp: failed to generate QR code PNG (%v)\n", err)
 	}
 
 	// This should fail because the maximum size of an alphanumeric
@@ -63,16 +58,14 @@ func TestURL(t *testing.T) {
 	var tooBigIdent = make([]byte, 8192)
 	_, err = io.ReadFull(PRNG, tooBigIdent)
 	if err != nil {
-		fmt.Printf("hotp: failed to read identity (%v)\n", err)
-		t.FailNow()
+		t.Fatalf("hotp: failed to read identity (%v)\n", err)
 	} else if _, err = otp.QR(string(tooBigIdent)); err == nil {
-		fmt.Println("hotp: QR code should fail to encode oversized URL")
-		t.FailNow()
+		t.Fatal("hotp: QR code should fail to encode oversized URL")
 	}
 }
 
 // This test makes sure we can generate codes for padded and non-padded
-// entries
+// entries.
 func TestPaddedURL(t *testing.T) {
 	var urlList = []string{
 		"otpauth://hotp/?secret=ME",
@@ -95,17 +88,15 @@ func TestPaddedURL(t *testing.T) {
 
 	for i := range urlList {
 		if o, id, err := FromURL(urlList[i]); err != nil {
-			fmt.Println("hotp: URL should have parsed successfully (id=", id, ")")
-			fmt.Printf("\turl was: %s\n", urlList[i])
-			t.FailNow()
-			fmt.Printf("\t%s, %s\n", o.OTP(), id)
+			t.Log("hotp: URL should have parsed successfully (id=", id, ")")
+			t.Logf("\turl was: %s\n", urlList[i])
+			t.Fatalf("\t%s, %s\n", o.OTP(), id)
 		} else {
 			code2 := o.OTP()
 			if code2 != codeList[i] {
-				fmt.Printf("hotp: mismatched OTPs\n")
-				fmt.Printf("\texpected: %s\n", codeList[i])
-				fmt.Printf("\t  actual: %s\n", code2)
-				t.FailNow()
+				t.Logf("hotp: mismatched OTPs\n")
+				t.Logf("\texpected: %s\n", codeList[i])
+				t.Fatalf("\t  actual: %s\n", code2)
 			}
 		}
 	}
@@ -128,9 +119,8 @@ func TestBadURL(t *testing.T) {
 
 	for i := range urlList {
 		if _, _, err := FromURL(urlList[i]); err == nil {
-			fmt.Println("hotp: URL should not have parsed successfully")
-			fmt.Printf("\turl was: %s\n", urlList[i])
-			t.FailNow()
+			t.Log("hotp: URL should not have parsed successfully")
+			t.Fatalf("\turl was: %s\n", urlList[i])
 		}
 	}
 }

twofactor/totp.go

@@ -2,7 +2,7 @@ package twofactor
 
 import (
 	"crypto"
-	"crypto/sha1"
+	"crypto/sha1" // #nosec G505 - required by RFC
 	"crypto/sha256"
 	"crypto/sha512"
 	"encoding/base32"
@@ -23,6 +23,42 @@ type TOTP struct {
 	step uint64
 }
 
+// NewTOTP takes a new key, a starting time, a step, the number of
+// digits of output (typically 6 or 8) and the hash algorithm to
+// use, and builds a new OTP.
+func NewTOTP(key []byte, start uint64, step uint64, digits int, algo crypto.Hash) *TOTP {
+	h := hashFromAlgo(algo)
+	if h == nil {
+		return nil
+	}
+
+	return &TOTP{
+		OATH: &OATH{
+			key:     key,
+			counter: start,
+			size:    digits,
+			hash:    h,
+			algo:    algo,
+		},
+		step: step,
+	}
+}
+
+// NewGoogleTOTP takes a secret as a base32-encoded string and
+// returns an appropriate Google Authenticator TOTP instance.
+func NewGoogleTOTP(secret string) (*TOTP, error) {
+	key, err := base32.StdEncoding.DecodeString(secret)
+	if err != nil {
+		return nil, err
+	}
+	return NewTOTP(key, 0, 30, 6, crypto.SHA1), nil
+}
+
+// NewTOTPSHA1 will build a new TOTP using SHA-1.
+func NewTOTPSHA1(key []byte, start uint64, step uint64, digits int) *TOTP {
+	return NewTOTP(key, start, step, digits, crypto.SHA1)
+}
+
 // Type returns OATH_TOTP.
 func (otp *TOTP) Type() Type {
 	return OATH_TOTP
@@ -53,34 +89,7 @@ func (otp *TOTP) otpCounter(t uint64) uint64 {
 
 // OTPCounter returns the current time value for the OTP.
 func (otp *TOTP) OTPCounter() uint64 {
-	return otp.otpCounter(uint64(timeSource.Now().Unix()))
-}
-
-// NewTOTP takes a new key, a starting time, a step, the number of
-// digits of output (typically 6 or 8) and the hash algorithm to
-// use, and builds a new OTP.
-func NewTOTP(key []byte, start uint64, step uint64, digits int, algo crypto.Hash) *TOTP {
-	h := hashFromAlgo(algo)
-	if h == nil {
-		return nil
-	}
-
-	return &TOTP{
-		OATH: &OATH{
-			key:     key,
-			counter: start,
-			size:    digits,
-			hash:    h,
-			algo:    algo,
-		},
-		step: step,
-	}
-
-}
-
-// NewTOTPSHA1 will build a new TOTP using SHA-1.
-func NewTOTPSHA1(key []byte, start uint64, step uint64, digits int) *TOTP {
-	return NewTOTP(key, start, step, digits, crypto.SHA1)
+	return otp.otpCounter(uint64(timeSource.Now().Unix() & 0x7FFFFFFF)) //#nosec G115 - masked out overflow bits
 }
 
 func hashFromAlgo(algo crypto.Hash) func() hash.Hash {
@@ -105,16 +114,6 @@ func GenerateGoogleTOTP() *TOTP {
 	return NewTOTP(key, 0, 30, 6, crypto.SHA1)
 }
 
-// NewGoogleTOTP takes a secret as a base32-encoded string and
-// returns an appropriate Google Authenticator TOTP instance.
-func NewGoogleTOTP(secret string) (*TOTP, error) {
-	key, err := base32.StdEncoding.DecodeString(secret)
-	if err != nil {
-		return nil, err
-	}
-	return NewTOTP(key, 0, 30, 6, crypto.SHA1), nil
-}
-
 func totpFromURL(u *url.URL) (*TOTP, string, error) {
 	label := u.Path[1:]
 	v := u.Query()
@@ -126,11 +125,12 @@ func totpFromURL(u *url.URL) (*TOTP, string, error) {
 
 	var algo = crypto.SHA1
 	if algorithm := v.Get("algorithm"); algorithm != "" {
-		if strings.EqualFold(algorithm, "SHA256") {
+		switch {
+		case strings.EqualFold(algorithm, "SHA256"):
 			algo = crypto.SHA256
-		} else if strings.EqualFold(algorithm, "SHA512") {
+		case strings.EqualFold(algorithm, "SHA512"):
 			algo = crypto.SHA512
-		} else if !strings.EqualFold(algorithm, "SHA1") {
+		case !strings.EqualFold(algorithm, "SHA1"):
 			return nil, "", ErrInvalidAlgo
 		}
 	}

twofactor/totp_internal_test.go

@@ -2,7 +2,6 @@ package twofactor
 
 import (
 	"crypto"
-	"fmt"
 	"testing"
 	"time"
 
@@ -14,6 +13,7 @@ var rfcTotpKey = map[crypto.Hash][]byte{
 	crypto.SHA256: []byte("12345678901234567890123456789012"),
 	crypto.SHA512: []byte("1234567890123456789012345678901234567890123456789012345678901234"),
 }
+
 var rfcTotpStep uint64 = 30
 
 var rfcTotpTests = []struct {
@@ -46,17 +46,15 @@ func TestTotpRFC(t *testing.T) {
 	for _, tc := range rfcTotpTests {
 		otp := NewTOTP(rfcTotpKey[tc.Algo], 0, rfcTotpStep, 8, tc.Algo)
 		if otp.otpCounter(tc.Time) != tc.T {
-			fmt.Printf("twofactor: invalid TOTP (t=%d, h=%d)\n", tc.Time, tc.Algo)
-			fmt.Printf("\texpected: %d\n", tc.T)
-			fmt.Printf("\t  actual: %d\n", otp.otpCounter(tc.Time))
-			t.Fail()
+			t.Logf("twofactor: invalid TOTP (t=%d, h=%d)\n", tc.Time, tc.Algo)
+			t.Logf("\texpected: %d\n", tc.T)
+			t.Errorf("\t  actual: %d\n", otp.otpCounter(tc.Time))
 		}
 
 		if code := otp.otp(otp.otpCounter(tc.Time)); code != tc.Code {
-			fmt.Printf("twofactor: invalid TOTP (t=%d, h=%d)\n", tc.Time, tc.Algo)
-			fmt.Printf("\texpected: %s\n", tc.Code)
-			fmt.Printf("\t  actual: %s\n", code)
-			t.Fail()
+			t.Logf("twofactor: invalid TOTP (t=%d, h=%d)\n", tc.Time, tc.Algo)
+			t.Logf("\texpected: %s\n", tc.Code)
+			t.Errorf("\t  actual: %s\n", code)
 		}
 	}
 }

twofactor/util.go

@@ -5,7 +5,7 @@ import (
 )
 
 // Pad calculates the number of '='s to add to our encoded string
-// to make base32.StdEncoding.DecodeString happy
+// to make base32.StdEncoding.DecodeString happy.
 func Pad(s string) string {
 	if !strings.HasSuffix(s, "=") && len(s)%8 != 0 {
 		for len(s)%8 != 0 {

twofactor/util_test.go

@@ -1,11 +1,12 @@
-package twofactor
+package twofactor_test
 
 import (
 	"encoding/base32"
-	"fmt"
 	"math/rand"
 	"strings"
 	"testing"
+
+	"git.wntrmute.dev/kyle/goutils/twofactor"
 )
 
 const letters = "1234567890!@#$%^&*()abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
@@ -19,34 +20,31 @@ func randString() string {
 }
 
 func TestPadding(t *testing.T) {
-	for i := 0; i < 300; i++ {
+	for range 300 {
 		b := randString()
-		origEncoding := string(b)
-		modEncoding := strings.ReplaceAll(string(b), "=", "")
+		origEncoding := b
+		modEncoding := strings.ReplaceAll(b, "=", "")
 		str, err := base32.StdEncoding.DecodeString(origEncoding)
 		if err != nil {
-			fmt.Println("Can't decode: ", string(b))
-			t.FailNow()
+			t.Fatal("Can't decode: ", b)
 		}
 
-		paddedEncoding := Pad(modEncoding)
+		paddedEncoding := twofactor.Pad(modEncoding)
 		if origEncoding != paddedEncoding {
-			fmt.Println("Padding failed:")
-			fmt.Printf("Expected: '%s'", origEncoding)
-			fmt.Printf("Got: '%s'", paddedEncoding)
-			t.FailNow()
+			t.Log("Padding failed:")
+			t.Logf("Expected: '%s'", origEncoding)
+			t.Fatalf("Got: '%s'", paddedEncoding)
 		} else {
-			mstr, err := base32.StdEncoding.DecodeString(paddedEncoding)
+			var mstr []byte
+			mstr, err = base32.StdEncoding.DecodeString(paddedEncoding)
 			if err != nil {
-				fmt.Println("Can't decode: ", paddedEncoding)
-				t.FailNow()
+				t.Fatal("Can't decode: ", paddedEncoding)
 			}
 
 			if string(mstr) != string(str) {
-				fmt.Println("Re-padding failed:")
-				fmt.Printf("Expected: '%s'", str)
-				fmt.Printf("Got: '%s'", mstr)
-				t.FailNow()
+				t.Log("Re-padding failed:")
+				t.Logf("Expected: '%s'", str)
+				t.Fatalf("Got: '%s'", mstr)
 			}
 		}
 	}