Better cover edge cases

Author: mborland

include/boost/crypt2/aes/ecb.hpp

@@ -108,9 +108,9 @@ template <compat::size_t Extent>
 BOOST_CRYPT_GPU_ENABLED_CONSTEXPR auto ecb_impl<Nr>::encrypt_no_padding(
         compat::span<compat::byte, Extent> message) noexcept -> state
 {
-    static_assert(Extent >= block_length_bytes, "Invalid block length");
+    static_assert(Extent == compat::dynamic_extent || Extent % block_length_bytes == 0, "Invalid ciphertext length");
 
-    if (message.size() % block_length_bytes != 0)
+    if (message.size() % block_length_bytes != 0 && !message.empty())
     {
         return state::incorrect_message_length;
     }
@@ -145,7 +145,9 @@ template <compat::size_t Extent>
 BOOST_CRYPT_GPU_ENABLED_CONSTEXPR auto ecb_impl<Nr>::decrypt_no_padding(
         compat::span<compat::byte, Extent> ciphertext) noexcept -> state
 {
-    if (ciphertext.size() % block_length_bytes != 0)
+    static_assert(Extent == compat::dynamic_extent || Extent % block_length_bytes == 0, "Invalid ciphertext length");
+
+    if (ciphertext.size() % block_length_bytes != 0 && !ciphertext.empty())
     {
         return state::incorrect_message_length;
     }

test/test_aes.cpp

@@ -116,6 +116,10 @@ void ecb_test()
     BOOST_TEST(gen2.init(key_span) == boost::crypt::state::success);
     BOOST_TEST(gen2.encrypt_no_padding(bad_message) == boost::crypt::state::incorrect_message_length);
     BOOST_TEST(gen2.encrypt_no_padding(bad_message_span) == boost::crypt::state::incorrect_message_length);
+
+    std::array<std::byte, 1000> incorrect_size {};
+    std::span<std::byte, std::dynamic_extent> incorrect_size_span {incorrect_size};
+    BOOST_TEST(gen2.decrypt_no_padding(incorrect_size_span) == boost::crypt::state::incorrect_message_length);
 }
 
 /*