Merge #14242: Avoid triggering undefined behaviour (std::memset(nullptr, 0, 0)) if an invalid string is passed to DecodeSecret(...)

d855e4cac8 Avoid triggering undefined behaviour (std::memset(nullptr, 0, 0)) if an invalid string is passed to DecodeSecret(...) (practicalswift)

Pull request description:

  Avoid triggering undefined behaviour (`std::memset(nullptr, 0, 0)`) if an invalid string is passed to `DecodeSecret(...)`.

  Background reading: [memcpy (and friends) with NULL pointers](https://www.imperialviolet.org/2016/06/26/nonnull.html)

  Steps to reproduce:

  ```
  ./configure --with-sanitizers=undefined && make check && ./test/functional/test_runner.py
  ```

Tree-SHA512: b8325ced4f724d9c03065e0747af56b1f297a90d9fb09a24d46c3231a90dce3df6299f2c41f863b5cec18eaeded7b46ee4b93d9a52adc2541eb4c44d2c0965d9

src/key_io.cpp

@@ -142,7 +142,9 @@ CKey DecodeSecret(const std::string& str)
             key.Set(data.begin() + privkey_prefix.size(), data.begin() + privkey_prefix.size() + 32, compressed);
         }
     }
-    memory_cleanse(data.data(), data.size());
+    if (!data.empty()) {
+        memory_cleanse(data.data(), data.size());
+    }
     return key;
 }
 

test/sanitizer_suppressions/ubsan

@@ -4,7 +4,6 @@ bool:wallet/wallet.cpp
 float-divide-by-zero:policy/fees.cpp
 float-divide-by-zero:validation.cpp
 float-divide-by-zero:wallet/wallet.cpp
-nonnull-attribute:support/cleanse.cpp
 unsigned-integer-overflow:arith_uint256.h
 unsigned-integer-overflow:basic_string.h
 unsigned-integer-overflow:bench/bench.h