Phase 1 API: pastes CRUD, password lock (argon2id), expiry sweeper, soft delete with 7d grace, public list

password.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/base64"
+	"fmt"
+	"strings"
+
+	"golang.org/x/crypto/argon2"
+)
+
+// argon2id with sane defaults
+const (
+	argonTime    = 1
+	argonMemory  = 64 * 1024
+	argonThreads = 4
+	argonKeyLen  = 32
+	argonSaltLen = 16
+)
+
+func argon2idHash(pw string) (string, error) {
+	salt := make([]byte, argonSaltLen)
+	if _, err := rand.Read(salt); err != nil {
+		return "", err
+	}
+	key := argon2.IDKey([]byte(pw), salt, argonTime, argonMemory, argonThreads, argonKeyLen)
+	return fmt.Sprintf("$argon2id$v=19$m=%d,t=%d,p=%d$%s$%s",
+		argonMemory, argonTime, argonThreads,
+		base64.RawStdEncoding.EncodeToString(salt),
+		base64.RawStdEncoding.EncodeToString(key)), nil
+}
+
+func checkPassword(hash, pw string) bool {
+	parts := strings.Split(hash, "$")
+	if len(parts) != 6 || parts[1] != "argon2id" {
+		return false
+	}
+	var m, t uint32
+	var p uint8
+	fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &m, &t, &p)
+	salt, err1 := base64.RawStdEncoding.DecodeString(parts[4])
+	want, err2 := base64.RawStdEncoding.DecodeString(parts[5])
+	if err1 != nil || err2 != nil {
+		return false
+	}
+	got := argon2.IDKey([]byte(pw), salt, t, m, p, uint32(len(want)))
+	return subtle.ConstantTimeCompare(got, want) == 1
+}
+
+// cryptoRead is used by genSlug
+func cryptoRead(b []byte) (int, error) { return rand.Read(b) }