avoid EVP_get_cipherbyname for common cyphers

Author: filimonov

src/Functions/FunctionsAES.cpp

@@ -9,6 +9,9 @@
 
 #include <string>
 #include <cassert>
+#include <array>
+#include <cstring>
+#include <string_view>
 
 namespace DB
 {
@@ -39,11 +42,47 @@ StringRef foldEncryptionKeyInMySQLCompatitableMode(size_t cipher_key_size, Strin
 
 const EVP_CIPHER * getCipherByName(StringRef cipher_name)
 {
-    // NOTE: cipher obtained not via EVP_CIPHER_fetch() would cause extra work on each context reset
-    // with EVP_CIPHER_CTX_reset() or EVP_EncryptInit_ex(), but using EVP_CIPHER_fetch()
-    // causes data race, so we stick to the slower but safer alternative here.
+    using CipherGetter = const EVP_CIPHER *(*)();
+    struct Entry
+    {
+        std::string_view name;
+        CipherGetter getter;
+    };
+
+    /// Fast path to avoid OBJ/namemap lookups in EVP_get_cipherbyname().
+    /// Statically linked OpenSSL provides direct getters for common AES modes.
+    static constexpr std::array<Entry, 21> fast_paths{{
+        {"aes-128-cbc", &EVP_aes_128_cbc},
+        {"aes-192-cbc", &EVP_aes_192_cbc},
+        {"aes-256-cbc", &EVP_aes_256_cbc},
+        {"aes-128-ecb", &EVP_aes_128_ecb},
+        {"aes-192-ecb", &EVP_aes_192_ecb},
+        {"aes-256-ecb", &EVP_aes_256_ecb},
+        {"aes-128-cfb", &EVP_aes_128_cfb},
+        {"aes-192-cfb", &EVP_aes_192_cfb},
+        {"aes-256-cfb", &EVP_aes_256_cfb},
+        {"aes-128-cfb8", &EVP_aes_128_cfb8},
+        {"aes-192-cfb8", &EVP_aes_192_cfb8},
+        {"aes-256-cfb8", &EVP_aes_256_cfb8},
+        {"aes-128-cfb1", &EVP_aes_128_cfb1},
+        {"aes-192-cfb1", &EVP_aes_192_cfb1},
+        {"aes-256-cfb1", &EVP_aes_256_cfb1},
+        {"aes-128-ofb", &EVP_aes_128_ofb},
+        {"aes-192-ofb", &EVP_aes_192_ofb},
+        {"aes-256-ofb", &EVP_aes_256_ofb},
+        {"aes-128-ctr", &EVP_aes_128_ctr},
+        {"aes-192-ctr", &EVP_aes_192_ctr},
+        {"aes-256-ctr", &EVP_aes_256_ctr},
+    }};
+
+    for (const auto & entry : fast_paths)
+    {
+        if (cipher_name.size == entry.name.size()
+            && std::memcmp(cipher_name.data, entry.name.data(), entry.name.size()) == 0)
+            return entry.getter();
+    }
 
-    /// We need zero-terminated string here:
+    /// Fallback keeps compatibility with custom providers/algorithms.
     return EVP_get_cipherbyname(cipher_name.toString().c_str());
 }