LibCrypto: Add MGF1

Author: https://github.com/stelar7
Commit: 73a534494c
Pull-request: https://github.com/SerenityOS/serenity/pull/23879
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/nico
Reviewed-by: https://github.com/tcl3

Tests/LibCrypto/CMakeLists.txt

@@ -3,13 +3,14 @@ set(TEST_SOURCES
     TestASN1.cpp
     TestBigFraction.cpp
     TestBigInteger.cpp
-    TestChecksum.cpp
     TestChaCha20.cpp
     TestChacha20Poly1305.cpp
+    TestChecksum.cpp
     TestCurves.cpp
     TestEd25519.cpp
     TestHash.cpp
     TestHMAC.cpp
+    TestMGF.cpp
     TestPBKDF2.cpp
     TestPoly1305.cpp
     TestRSA.cpp

Tests/LibCrypto/TestMGF.cpp

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2024, stelar7  <dudedbz@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCrypto/Hash/MGF.h>
+#include <LibCrypto/Hash/SHA1.h>
+#include <LibCrypto/Hash/SHA2.h>
+#include <LibTest/TestCase.h>
+
+static ByteBuffer operator""_b(char const* string, size_t length)
+{
+    return ByteBuffer::copy(string, length).release_value();
+}
+
+TEST_CASE(test_mgf1_short)
+{
+    u8 expected_result[3] {
+        0x1a, 0xc9, 0x07
+    };
+    auto expected = ReadonlyBytes { expected_result, 3 };
+
+    ByteBuffer seed = { "foo"_b };
+    auto length = 3;
+    ByteBuffer result = MUST(Crypto::Hash::MGF::mgf1<Crypto::Hash::SHA1>(seed, length));
+
+    EXPECT_EQ(expected, result);
+}
+
+TEST_CASE(test_mgf1_long)
+{
+    u8 expected_result[50] {
+        0xbc, 0x0c, 0x65, 0x5e, 0x01, 0x6b, 0xc2, 0x93, 0x1d, 0x85, 0xa2, 0xe6, 0x75, 0x18, 0x1a, 0xdc,
+        0xef, 0x7f, 0x58, 0x1f, 0x76, 0xdf, 0x27, 0x39, 0xda, 0x74, 0xfa, 0xac, 0x41, 0x62, 0x7b, 0xe2,
+        0xf7, 0xf4, 0x15, 0xc8, 0x9e, 0x98, 0x3f, 0xd0, 0xce, 0x80, 0xce, 0xd9, 0x87, 0x86, 0x41, 0xcb,
+        0x48, 0x76
+    };
+    auto expected = ReadonlyBytes { expected_result, 50 };
+
+    ByteBuffer seed = { "bar"_b };
+    auto length = 50;
+    ByteBuffer result = MUST(Crypto::Hash::MGF::mgf1<Crypto::Hash::SHA1>(seed, length));
+
+    EXPECT_EQ(expected, result);
+}
+
+TEST_CASE(test_mgf1_long_sha256)
+{
+    u8 expected_result[50] {
+        0x38, 0x25, 0x76, 0xa7, 0x84, 0x10, 0x21, 0xcc, 0x28, 0xfc, 0x4c, 0x09, 0x48, 0x75, 0x3f, 0xb8,
+        0x31, 0x20, 0x90, 0xce, 0xa9, 0x42, 0xea, 0x4c, 0x4e, 0x73, 0x5d, 0x10, 0xdc, 0x72, 0x4b, 0x15,
+        0x5f, 0x9f, 0x60, 0x69, 0xf2, 0x89, 0xd6, 0x1d, 0xac, 0xa0, 0xcb, 0x81, 0x45, 0x02, 0xef, 0x04,
+        0xea, 0xe1
+    };
+    auto expected = ReadonlyBytes { expected_result, 50 };
+
+    ByteBuffer seed = { "bar"_b };
+    auto length = 50;
+    ByteBuffer result = MUST(Crypto::Hash::MGF::mgf1<Crypto::Hash::SHA256>(seed, length));
+
+    EXPECT_EQ(expected, result);
+}

Userland/Libraries/LibCrypto/Hash/MGF.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2024, stelar7 <dudedbz@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/ByteReader.h>
+#include <AK/Endian.h>
+
+namespace Crypto::Hash {
+
+class MGF {
+public:
+    // https://datatracker.ietf.org/doc/html/rfc2437#section-10.2.1
+    template<typename HashFunction>
+    static ErrorOr<ByteBuffer> mgf1(ReadonlyBytes seed, size_t length)
+    requires requires { HashFunction::digest_size(); }
+    {
+        HashFunction hash;
+
+        size_t h_len = hash.digest_size();
+
+        // 1. If length > 2^32(hLen), output "mask too long" and stop.
+        if (length > (h_len << 32))
+            return Error::from_string_view("mask too long"sv);
+
+        // 2. Let T be the empty octet string.
+        auto t = TRY(ByteBuffer::create_uninitialized(0));
+
+        // 3. For counter from 0 to ceil(length / hLen) - 1, do the following:
+        auto counter = 0u;
+        auto iterations = AK::ceil_div(length, h_len) - 1;
+
+        auto c = TRY(ByteBuffer::create_uninitialized(4));
+        for (; counter <= iterations; ++counter) {
+            // a. Convert counter to an octet string C of length 4 with the primitive I2OSP: C = I2OSP(counter, 4)
+            ByteReader::store(static_cast<u8*>(c.data()), AK::convert_between_host_and_big_endian(static_cast<u32>(counter)));
+
+            // b. Concatenate the hash of the seed Z and C to the octet string T: T = T || Hash (Z || C)
+            hash.update(seed);
+            hash.update(c);
+            auto digest = hash.digest();
+
+            TRY(t.try_append(digest.bytes()));
+        }
+
+        // 4. Output the leading l octets of T as the octet string mask.
+        return t.slice(0, length);
+    }
+};
+
+}