Avoid allocating zero bytes for SHA-3 padding

Inspired by #1433

1 files changed, 2 insertions, 15 deletions

diff --git a/src/lib/hash/shake/shake.cpp b/src/lib/hash/shake/shake.cpp
index ab7c9debe..76ed79a27 100644
--- a/src/lib/hash/shake/shake.cpp
+++ b/src/lib/hash/shake/shake.cpp
@@ -47,15 +47,8 @@ void SHAKE_128::add_data(const uint8_t input[], size_t length)
 
 void SHAKE_128::final_result(uint8_t output[])
    {
-   std::vector<uint8_t> padding(SHAKE_128_BITRATE / 8 - m_S_pos);
-
-   padding[0] = 0x1F;
-   padding[padding.size()-1] |= 0x80;
-
-   add_data(padding.data(), padding.size());
-
+   SHA_3::finish(SHAKE_128_BITRATE, m_S, m_S_pos, 0x1F, 0x80);
    SHA_3::expand(SHAKE_128_BITRATE, m_S, output, output_length());
-
    clear();
    }
 
@@ -95,13 +88,7 @@ void SHAKE_256::add_data(const uint8_t input[], size_t length)
 
 void SHAKE_256::final_result(uint8_t output[])
    {
-   std::vector<uint8_t> padding(SHAKE_256_BITRATE / 8 - m_S_pos);
-
-   padding[0] = 0x1F;
-   padding[padding.size()-1] |= 0x80;
-
-   add_data(padding.data(), padding.size());
-
+   SHA_3::finish(SHAKE_256_BITRATE, m_S, m_S_pos, 0x1F, 0x80);
    SHA_3::expand(SHAKE_256_BITRATE, m_S, output, output_length());
 
    clear();