Support wolfSSL 4.6+ (#3398)

* Fix testing against reference crypto implementation

Build would fail on CI if using cyassl/wolfssl or polarssl/mbedtls as a
backend and testing it against reference openssl implementation due to
missing include directories, but only if bundled (non-system) b64 is
used.

* Iniitalize size arguments to `wc_DhGenerateKeyPair`

Despite it not being mentioned in the documentation [1] and v4.6 release
notes [2], the two size parameters became [3] not purely "out", but
"in/out", to avoid potential buffer overflows.

[1] https://www.wolfssl.com/documentation/manuals/wolfssl/group__Diffie-Hellman.html
[2] https://github.com/wolfSSL/wolfssl/releases/tag/v4.6.0-stable
[3] 4364700c01

libtransmission/crypto-utils-cyassl.cc

@@ -258,8 +258,8 @@ bool tr_dh_make_key(tr_dh_ctx_t raw_handle, size_t /*private_key_length*/, uint8
 
     auto const lock = std::lock_guard(rng_mutex_);
 
-    auto my_private_key_length = word32{};
-    auto my_public_key_length = word32{};
+    auto my_private_key_length = handle->key_length;
+    auto my_public_key_length = static_cast<word32>(*public_key_length);
     if (!check_result(API(DhGenerateKeyPair)(
             &handle->dh,
             get_rng(),

libtransmission/crypto.cc

@@ -41,7 +41,7 @@ static void ensureKeyExists(tr_crypto* crypto)
 {
     if (crypto->dh == nullptr)
     {
-        size_t public_key_length = 0;
+        size_t public_key_length = KEY_LEN;
         crypto->dh = tr_dh_new(dh_P, sizeof(dh_P), dh_G, sizeof(dh_G));
         tr_dh_make_key(crypto->dh, DhPrivkeyLen, crypto->myPublicKey, &public_key_length);
 

tests/libtransmission/CMakeLists.txt

@@ -52,6 +52,7 @@ target_include_directories(libtransmission-test
 
 target_include_directories(libtransmission-test SYSTEM
     PRIVATE
+        ${B64_INCLUDE_DIRS}
         ${CURL_INCLUDE_DIRS}
         ${EVENT2_INCLUDE_DIRS})