added an assert for aes key length >= 4 in aes_key_schedule to prevent division by zero found by clang-analyzer

1 files changed, 6 insertions, 0 deletions

diff --git a/src/lib/block/aes/aes.cpp b/src/lib/block/aes/aes.cpp
index 6cca701af..aac277b4f 100644
--- a/src/lib/block/aes/aes.cpp
+++ b/src/lib/block/aes/aes.cpp
@@ -345,6 +345,12 @@ void aes_key_schedule(const byte key[], size_t length,
                       secure_vector<byte>& ME,
                       secure_vector<byte>& MD)
    {
+
+   // if length is < 4, X = 0, the first for loop is not entered and in
+   // the second for loop "RC[(i-X)/X]" = division by zero
+   // But obviously valid aes length values are only 16, 24 and 32
+   BOTAN_ASSERT( length >= 4, "aes key length has valid size" );
+
    static const u32bit RC[10] = {
       0x01000000, 0x02000000, 0x04000000, 0x08000000, 0x10000000,
       0x20000000, 0x40000000, 0x80000000, 0x1B000000, 0x36000000 };