initial commit

tests/test_padding.cpp

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+// Copyright (c) 2025-2026, Brandon Lehmann
+// BSD 3-Clause License (see LICENSE)
+
+#include "test_harness.h"
+#include "tinyaes/cbc.h"
+
+TEST(pkcs7_full_block_padding)
+{
+    // When input is exactly block-aligned, a full padding block (16 bytes of 0x10) is added
+    std::vector<uint8_t> key(16, 0xAA);
+    std::vector<uint8_t> iv(16, 0x00);
+    std::vector<uint8_t> plaintext(16, 0x42); // Exactly one block
+    std::vector<uint8_t> ct, pt;
+
+    auto result = tinyaes::cbc_encrypt_pkcs7(key, iv, plaintext, ct);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_TRUE(ct.size() == 32); // 16 data + 16 padding
+
+    result = tinyaes::cbc_decrypt_pkcs7(key, iv, ct, pt);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_EQ(pt, plaintext);
+}
+
+TEST(pkcs7_single_byte)
+{
+    std::vector<uint8_t> key(16, 0xBB);
+    std::vector<uint8_t> iv(16, 0x00);
+    std::vector<uint8_t> plaintext = {0xFF};
+    std::vector<uint8_t> ct, pt;
+
+    auto result = tinyaes::cbc_encrypt_pkcs7(key, iv, plaintext, ct);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_TRUE(ct.size() == 16); // 1 + 15 padding
+
+    result = tinyaes::cbc_decrypt_pkcs7(key, iv, ct, pt);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_EQ(pt, plaintext);
+}
+
+TEST(pkcs7_empty_plaintext)
+{
+    std::vector<uint8_t> key(16, 0xCC);
+    std::vector<uint8_t> iv(16, 0x00);
+    std::vector<uint8_t> plaintext; // Empty
+    std::vector<uint8_t> ct, pt;
+
+    auto result = tinyaes::cbc_encrypt_pkcs7(key, iv, plaintext, ct);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_TRUE(ct.size() == 16); // Full block of padding (0x10)
+
+    result = tinyaes::cbc_decrypt_pkcs7(key, iv, ct, pt);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_EQ(pt, plaintext);
+}
+
+TEST(pkcs7_15_byte_plaintext)
+{
+    std::vector<uint8_t> key(16, 0xDD);
+    std::vector<uint8_t> iv(16, 0x00);
+    std::vector<uint8_t> plaintext(15, 0x42);
+    std::vector<uint8_t> ct, pt;
+
+    auto result = tinyaes::cbc_encrypt_pkcs7(key, iv, plaintext, ct);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_TRUE(ct.size() == 16); // 15 + 1 padding byte
+
+    result = tinyaes::cbc_decrypt_pkcs7(key, iv, ct, pt);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+    ASSERT_EQ(pt, plaintext);
+}
+
+TEST(pkcs7_invalid_padding_rejected)
+{
+    // Construct ciphertext that decrypts to invalid padding
+    std::vector<uint8_t> key(16, 0xEE);
+    std::vector<uint8_t> iv(16, 0x00);
+
+    // Encrypt known plaintext, then corrupt last byte of ciphertext
+    std::vector<uint8_t> plaintext(16, 0x42);
+    std::vector<uint8_t> ct, pt;
+
+    auto result = tinyaes::cbc_encrypt_pkcs7(key, iv, plaintext, ct);
+    ASSERT_TRUE(result == tinyaes::Result::Success);
+
+    // Flip a bit in the last block (padding block)
+    ct.back() ^= 0x01;
+
+    result = tinyaes::cbc_decrypt_pkcs7(key, iv, ct, pt);
+    ASSERT_TRUE(result == tinyaes::Result::InvalidPadding);
+}