♻️ refactor: Extract Instant struct

bare_minimum_crypto/cpp/bmc_test.cpp

@@ -48,7 +48,7 @@ bool is_pubkey_length (const vector <uint8_t> & v) {
 optional <vector <uint8_t>> try_verify_signed_data (
 	const ExpiringSignature & sig,
 	const vector <uint8_t> & pubkey,
-	int64_t now
+	Instant now
 ) {
 	try_sodium_init ();
 	
@@ -67,13 +67,12 @@ optional <vector <uint8_t>> try_verify_signed_data (
 	
 	const json j = json::parse (sig.cert_s);
 	
-	const int64_t not_before = j ["not_before"];
-	const int64_t not_after = j ["not_after"];
+	const TimeRange tr {
+		j ["not_before"],
+		j ["not_after"]
+	};
 	
-	if (now < not_before) {
-		return nullopt;
-	}
-	if (now > not_after) {
+	if (! tr.contains (now)) {
 		return nullopt;
 	}
 	
@@ -86,7 +85,7 @@ optional <vector <uint8_t>> try_verify_signed_data (
 optional <vector <uint8_t>> verify_signed_data (
 	const ExpiringSignature & sig,
 	const vector <uint8_t> & pubkey,
-	int64_t now
+	Instant now
 ) {
 	try {
 		return try_verify_signed_data (sig, pubkey, now);
@@ -100,7 +99,7 @@ optional <vector <uint8_t>> verify_cert_and_data (
 	const ExpiringSignature & signed_cert,
 	const ExpiringSignature & signed_data,
 	const vector <uint8_t> & root_pubkey,
-	int64_t now
+	Instant now
 ) {
 	auto subkey_opt = verify_signed_data (signed_cert, root_pubkey, now);
 	if (! subkey_opt) {
@@ -116,14 +115,14 @@ optional <vector <uint8_t>> verify_cert_and_data (
 	const ExpiringSignature & signed_data,
 	const vector <uint8_t> & root_pubkey
 ) {
-	return verify_cert_and_data (signed_cert, signed_data, root_pubkey, get_seconds_since_epoch ());
+	return verify_cert_and_data (signed_cert, signed_data, root_pubkey, Instant::now ());
 }
 
 optional <vector <uint8_t>> verify_signed_data (
 	const ExpiringSignature & sig,
 	const vector <uint8_t> & pubkey
 ) {
-	return verify_signed_data (sig, pubkey, get_seconds_since_epoch ());
+	return verify_signed_data (sig, pubkey, Instant::now ());
 }
 
 class SigningKey {
@@ -150,20 +149,17 @@ public:
 	
 	optional <ExpiringSignature> sign_base64 (
 		const string & payload_b64,
-		int64_t duration,
-		int64_t now
+		TimeRange tr
 	) const {
 		try_sodium_init ();
 		
-		if (duration > about_1_year) {
+		if (tr.duration () > about_1_year) {
 			return nullopt;
 		}
 		
-		const auto not_after = now + duration;
-		
 		const json j {
-			{"not_before", now},
-			{"not_after", not_after},
+			{"not_before", tr.not_before},
+			{"not_after", tr.not_after},
 			{"payload_b64", payload_b64},
 		};
 		
@@ -180,14 +176,14 @@ public:
 		};
 	}
 	
-	optional <ExpiringSignature> sign_key (const SigningKey & k, int64_t now) const 
+	optional <ExpiringSignature> sign_key (const SigningKey & k, Instant now) const 
 	{
-		return sign_base64 (k.pub_to_base64 (), about_3_months, now);
+		return sign_base64 (k.pub_to_base64 (), TimeRange::from_start_and_dur (now, about_3_months));
 	}
 	
-	optional <ExpiringSignature> sign_data (const vector <uint8_t> & v, int64_t now) const 
+	optional <ExpiringSignature> sign_data (const vector <uint8_t> & v, Instant now) const 
 	{
-		return sign_base64 (base64_encode (v), about_1_week, now);
+		return sign_base64 (base64_encode (v), TimeRange::from_start_and_dur (now, about_1_week));
 	}
 };
 
@@ -207,7 +203,7 @@ int happy_path () {
 	SigningKey signing_key;
 	cerr << "Signing key " << signing_key.pub_to_base64 () << endl;
 	
-	const auto now = get_seconds_since_epoch ();
+	const auto now = Instant::now ();
 	
 	// That signing key signs some important data
 	const auto important_data = copy_to_bytes ("Nikolai, Anna, Ivan, Mikhail, Ivan, Nikolai, Anna. 7 4 1 4 3 5 7 4");
@@ -219,7 +215,7 @@ int happy_path () {
 	{
 		// Check that a different time results in a different cert
 		const auto cert_2 = std::move (*root_key.sign_key (signing_key, now));
-		const auto cert_3 = std::move (*root_key.sign_key (signing_key, now + 1));
+		const auto cert_3 = std::move (*root_key.sign_key (signing_key, Instant {now.x + 1}));
 		
 		if (cert != cert_2) {
 			cerr << "Certs should have been identical" << endl;

bare_minimum_crypto/cpp/time_helpers.cpp

@@ -7,26 +7,66 @@ namespace BareMinimumCrypto {
 	using namespace std;
 	using namespace chrono;
 	
-	int64_t get_seconds_since_epoch () {
+	Instant::Instant (int64_t x): x (x) {}
+	
+	Instant Instant::now () {
 		const auto utc_now = system_clock::now ();
-		return duration_cast <seconds> (utc_now.time_since_epoch ()).count ();
+		return Instant {duration_cast <seconds> (utc_now.time_since_epoch ()).count ()};
+	}
+	
+	bool TimeRange::contains (Instant x) const {
+		if (not_after < not_before) {
+			return false;
+		}
+		
+		if (x.x < not_before) {
+			return false;
+		}
+		
+		if (x.x > not_after) {
+			return false;
+		}
+		
+		return true;
+	}
+	
+	int64_t TimeRange::duration () const {
+		return not_after - not_before;
+	}
+	
+	TimeRange TimeRange::from_start_and_dur (Instant start, int64_t dur) {
+		return TimeRange {
+			start.x,
+			start.x + dur
+		};
 	}
 	
 	// Most tests will use a virtual clock. But just as a smoke test,
 	// make sure real time is realistic.
 
 	int test_time () {
-		const auto seconds_since_epoch = get_seconds_since_epoch ();
+		const auto now = Instant::now ();
 		
 		const auto time_of_writing = 1610844872;
-		if (seconds_since_epoch < time_of_writing) {
-			cerr << "Error: Real time is in the past." << endl;
+		const int64_t about_100_years = (int64_t)100 * 365 * 86400;
+		
+		const TimeRange tr {
+			time_of_writing,
+			time_of_writing + about_100_years
+		};
+		
+		if (! tr.contains (now)) {
+			cerr << "System clock is acting weird" << endl;
 			return 1;
 		}
 		
-		const int64_t about_100_years = (int64_t)100 * 365 * 86400;
-		if (seconds_since_epoch > time_of_writing + about_100_years) {
-			cerr << "Error: Real time is in the far future." << endl;
+		const TimeRange bad_tr {
+			time_of_writing + about_100_years,
+			time_of_writing
+		};
+		
+		if (bad_tr.contains (now)) {
+			cerr << "Invalid TimeRange should not contain any Instants" << endl;
 			return 1;
 		}
 		

bare_minimum_crypto/cpp/time_helpers.h

@@ -7,7 +7,23 @@ namespace BareMinimumCrypto {
 	const int64_t about_3_months = (int64_t)105 * 86400;
 	const int64_t about_1_year = (int64_t)365 * 86400;
 	
-	int64_t get_seconds_since_epoch ();
+	struct Instant {
+		// Seconds since Unix epoch
+		int64_t x;
+		
+		Instant (int64_t x);
+		static Instant now ();
+	};
+	
+	struct TimeRange {
+		int64_t not_before;
+		int64_t not_after;
+		
+		bool contains (Instant x) const;
+		int64_t duration () const;
+		
+		static TimeRange from_start_and_dur (Instant start, int64_t dur);
+	};
 	
 	int test_time ();
 }