From 13abbc5ea8c6b0bb145983c7d232dbe3bdc398c3 Mon Sep 17 00:00:00 2001
From: AnotherTest <ali.mpfard@gmail.com>
Date: Sun, 18 Apr 2021 13:44:36 +0430
Subject: [PATCH] LibCrypto: Implement UTCTime and GeneralizedTime parsers

---
 Userland/Libraries/LibCrypto/ASN1/ASN1.cpp | 114 +++++++++++++++++++++
 Userland/Libraries/LibCrypto/ASN1/ASN1.h   |   4 +
 2 files changed, 118 insertions(+)

diff --git a/Userland/Libraries/LibCrypto/ASN1/ASN1.cpp b/Userland/Libraries/LibCrypto/ASN1/ASN1.cpp
index 17d9c68a65..250b106fac 100644
--- a/Userland/Libraries/LibCrypto/ASN1/ASN1.cpp
+++ b/Userland/Libraries/LibCrypto/ASN1/ASN1.cpp
@@ -92,4 +92,118 @@ String type_name(Type type)
     return "InvalidType";
 }
 
+Optional<Core::DateTime> parse_utc_time(const StringView& time)
+{
+    // YYMMDDhhmm[ss]Z or YYMMDDhhmm[ss](+|-)hhmm
+    GenericLexer lexer(time);
+    auto year_in_century = lexer.consume(2).to_uint();
+    auto month = lexer.consume(2).to_uint();
+    auto day = lexer.consume(2).to_uint();
+    auto hour = lexer.consume(2).to_uint();
+    auto minute = lexer.consume(2).to_uint();
+    Optional<unsigned> seconds, offset_hours, offset_minutes;
+    [[maybe_unused]] bool negative_offset = false;
+    if (!lexer.next_is('Z')) {
+        if (!lexer.next_is(is_any_of("+-"))) {
+            seconds = lexer.consume(2).to_uint();
+            if (!seconds.has_value()) {
+                return {};
+            }
+        }
+
+        if (lexer.next_is(is_any_of("+-"))) {
+            negative_offset = lexer.consume() == '-';
+            offset_hours = lexer.consume(2).to_uint();
+            offset_minutes = lexer.consume(2).to_uint();
+            if (!offset_hours.has_value() || !offset_minutes.has_value()) {
+                return {};
+            }
+        } else {
+            lexer.consume();
+        }
+    } else {
+        lexer.consume();
+    }
+
+    if (!year_in_century.has_value() || !month.has_value() || !day.has_value() || !hour.has_value() || !minute.has_value()) {
+        return {};
+    }
+
+    auto full_year = (Core::DateTime::now().year() / 100) * 100 + year_in_century.value();
+    auto full_seconds = seconds.value_or(0);
+
+    // FIXME: Handle offsets!
+    if (offset_hours.has_value() || offset_minutes.has_value())
+        dbgln("FIXME: Implement UTCTime with offset!");
+
+    return Core::DateTime::create(full_year, month.value(), day.value(), hour.value(), minute.value(), full_seconds);
+}
+
+Optional<Core::DateTime> parse_generalized_time(const StringView& time)
+{
+    // YYYYMMDDhh[mm[ss[.fff]]] or YYYYMMDDhh[mm[ss[.fff]]]Z or YYYYMMDDhh[mm[ss[.fff]]](+|-)hhmm
+    GenericLexer lexer(time);
+    auto year = lexer.consume(4).to_uint();
+    auto month = lexer.consume(2).to_uint();
+    auto day = lexer.consume(2).to_uint();
+    auto hour = lexer.consume(2).to_uint();
+    Optional<unsigned> minute, seconds, miliseconds, offset_hours, offset_minutes;
+    [[maybe_unused]] bool negative_offset = false;
+    if (!lexer.is_eof()) {
+        if (lexer.consume_specific('Z'))
+            goto done_parsing;
+
+        if (!lexer.next_is(is_any_of("+-"))) {
+            minute = lexer.consume(2).to_uint();
+            if (!minute.has_value()) {
+                return {};
+            }
+            if (lexer.consume_specific('Z'))
+                goto done_parsing;
+        }
+
+        if (!lexer.next_is(is_any_of("+-"))) {
+            seconds = lexer.consume(2).to_uint();
+            if (!seconds.has_value()) {
+                return {};
+            }
+            if (lexer.consume_specific('Z'))
+                goto done_parsing;
+        }
+
+        if (lexer.consume_specific('.')) {
+            miliseconds = lexer.consume(3).to_uint();
+            if (!miliseconds.has_value()) {
+                return {};
+            }
+            if (lexer.consume_specific('Z'))
+                goto done_parsing;
+        }
+
+        if (lexer.next_is(is_any_of("+-"))) {
+            negative_offset = lexer.consume() == '-';
+            offset_hours = lexer.consume(2).to_uint();
+            offset_minutes = lexer.consume(2).to_uint();
+            if (!offset_hours.has_value() || !offset_minutes.has_value()) {
+                return {};
+            }
+        } else {
+            lexer.consume();
+        }
+    }
+
+done_parsing:;
+
+    if (!year.has_value() || !month.has_value() || !day.has_value() || !hour.has_value()) {
+        return {};
+    }
+
+    // FIXME: Handle offsets!
+    if (offset_hours.has_value() || offset_minutes.has_value())
+        dbgln("FIXME: Implement GeneralizedTime with offset!");
+
+    // Unceremonially drop the miliseconds on the floor.
+    return Core::DateTime::create(year.value(), month.value(), day.value(), hour.value(), minute.value_or(0), seconds.value_or(0));
+}
+
 }
diff --git a/Userland/Libraries/LibCrypto/ASN1/ASN1.h b/Userland/Libraries/LibCrypto/ASN1/ASN1.h
index 6b7d805b56..64ff41b58f 100644
--- a/Userland/Libraries/LibCrypto/ASN1/ASN1.h
+++ b/Userland/Libraries/LibCrypto/ASN1/ASN1.h
@@ -27,6 +27,7 @@
 #pragma once
 
 #include <AK/Types.h>
+#include <LibCore/DateTime.h>
 #include <LibCrypto/BigInt/UnsignedBigInteger.h>
 
 namespace Crypto::ASN1 {
@@ -71,4 +72,7 @@ String kind_name(Kind);
 String class_name(Class);
 String type_name(Type);
 
+Optional<Core::DateTime> parse_utc_time(const StringView&);
+Optional<Core::DateTime> parse_generalized_time(const StringView&);
+
 }