Dear OpenSSL community, in a C++ (vc14, OpenSSL 1.0.2h/m) project, I'm trying to negotiate a secret between two parties, using EC crypto. I've used https://wiki.openssl.org/index.php/EVP_Key_Agreement as a recipe and wrapped memory allocations into unique_ptrs. The code fulfills its purpose of deriving a shared secret, but memory leak detection with _CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF ); _CrtSetReportMode( _CRT_WARN, _CRTDBG_MODE_FILE ); _CrtSetReportFile( _CRT_WARN, _CRTDBG_FILE_STDOUT ); produces a warning: Detected memory leaks! Dumping objects -> {10316} normal block at 0x00307680, 12 bytes long. Data: < v0 > F0 76 30 00 00 00 00 00 0D 00 00 00 {10315} normal block at 0x00351068, 16 bytes long. Data: < > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 {10314} normal block at 0x00350F68, 20 bytes long. Data: < h 5 > 00 00 00 00 68 10 35 00 00 00 00 00 04 00 00 00 {10313} normal block at 0x003076F0, 12 bytes long. Data: < h 5 > 0D 00 00 00 68 0F 35 00 00 00 00 00 {10312} normal block at 0x00310A70, 64 bytes long. Data: < > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 {10311} normal block at 0x00309E98, 96 bytes long. Data: <p 1 A ' > 70 0A 31 00 90 41 20 0F A0 0D 27 0F 08 00 00 00 Object dump complete.
Let me note two things: - The line without which the memory leak disappears is the line triggering the actual secret derivation: if(EVP_PKEY_derive(ctx.get(), skey.get(), &skeylen) <= 0) - The size of the leak is independent of how often I run the procedure of generating two sets of keys and then calling DeriveSecret(). *** Therefore, I'm wondering whether I've missed a call to free that I must trigger to deallocate this memory. *** I have added an allocation hook to check, as an example, when the 96-byte allocation occurs: [Name] [Language] libeay32.dll!default_malloc_ex(unsigned int num, const char * file, int line) Line 79 C libeay32.dll!CRYPTO_malloc(int num, const char * file, int line) Line 342 C libeay32.dll!lh_new(unsigned long(*)(const void *) h, int(*)(const void *, const void *) c) Line 120 C libeay32.dll!ex_data_check() Line 279 C libeay32.dll!def_get_class(int class_index) Line 316 C libeay32.dll!int_new_ex_data(int class_index, void * obj, crypto_ex_data_st * ad) Line 421 C libeay32.dll!CRYPTO_new_ex_data(int class_index, void * obj, crypto_ex_data_st * ad) Line 583 C libeay32.dll!ECDH_DATA_new_method(engine_st * engine) Line 165 C libeay32.dll!ecdh_data_new() Line 178 C libeay32.dll!ecdh_check(ec_key_st * key) Line 215 C libeay32.dll!ECDH_compute_key(void * out, unsigned int outlen, const ec_point_st * pub_key, ec_key_st * eckey, void *(*)(const void *, unsigned int, void *, unsigned int *) KDF) Line 77 C libeay32.dll!pkey_ec_derive(evp_pkey_ctx_st * ctx, unsigned char * key, unsigned int * keylen) Line 237 C libeay32.dll!pkey_ec_kdf_derive(evp_pkey_ctx_st * ctx, unsigned char * key, unsigned int * keylen) Line 252 C libeay32.dll!EVP_PKEY_derive(evp_pkey_ctx_st * ctx, unsigned char * key, unsigned int * pkeylen) Line 345 C [.]DeriveSecret() Line 802 C++ Please see below for how I call EVP_PKEY_derive. Can you tell me what I'm missing? Do you need more info? Thank you for looking into this and helping! Regards, Holger template<typename T> using deleted_unique_ptr = std::unique_ptr<T,std::function<void(T*)>>; deleted_unique_ptr<EVP_PKEY> m_pOwnKey; deleted_unique_ptr<EVP_PKEY> m_pPeerKey; void [...]::DeriveSecret() { if (!(m_pOwnKey && m_pOwnKey->pkey.ec)) { throw KeyUninitializedError("Secret cannot be derived if own key is missing"); } if (!m_pPeerKey) { throw KeyUninitializedError("Secret cannot be derived if peer key is missing"); } deleted_unique_ptr<EVP_PKEY_CTX> ctx(EVP_PKEY_CTX_new(m_pOwnKey.get(), NULL), [](EVP_PKEY_CTX* obj) { EVP_PKEY_CTX_free(obj); }); size_t skeylen; if(!ctx) { /* Error occurred */ throw OpenSslError("Error creating EVP_PKEY_CTX"); } if(EVP_PKEY_derive_init(ctx.get()) <= 0) { /* Error */ throw OpenSslError("Error in EVP_PKEY_derive_init"); } if(EVP_PKEY_derive_set_peer(ctx.get(), m_pPeerKey.get()) <= 0) { /* Error */ throw OpenSslError("Error setting peer key in key negotiation"); } /* Determine buffer length */ if(EVP_PKEY_derive(ctx.get(), NULL, &skeylen) <= 0) { /* Error */ throw OpenSslError("Error computing length of shared secret"); } if (skeylen != secretSize) { throw OpenSslError("Shared secret has unexpected size"); } deleted_unique_ptr<unsigned char> skey((unsigned char*)OPENSSL_malloc(skeylen), [](unsigned char* obj) { OPENSSL_free(obj); }); /// @note The derivation of the secret seems to leak memory within OpenSSL if(EVP_PKEY_derive(ctx.get(), skey.get(), &skeylen) <= 0) { /* Error */ throw OpenSslError("Error deriving shared secret"); } [...] } Dr. Holger Seiberlich Software Developer Bruker Optik GmbH Rudolf-Plank-Str. 27 76275 Ettlingen, Germany Phone: +49 7243 504-2626 Fax: +49 7243 504-42626 holger.seiberl...@bruker.com www.bruker.com Sitz der Gesellschaft ist Ettlingen, HRB 36 2608 Amtsgericht Mannheim Geschäftsführer: Urban Faeh, Marc Beisel, Juergen Srega Diese E-Mail und alle Anlagen können Betriebs- oder Geschäftsgeheimnisse, oder sonstige vertrauliche Informationen enthalten. Sollten Sie diese E-Mail irrtümlich erhalten haben, ist Ihnen eine Kenntnisnahme des Inhalts, eine Vervielfältigung oder Weitergabe der E-Mail und aller Anlagen ausdrücklich untersagt. Bitte benachrichtigen Sie den Absender und löschen/vernichten Sie die empfangene E-Mail und alle Anlagen. Vielen Dank. This message and any attachments may contain trade secrets or privileged, undisclosed or otherwise confidential information. If you have received this e-mail in error, you are hereby notified that any review, copying or distribution of it and its attachments is strictly prohibited. Please inform the sender immediately and delete/destroy the original message and any copies. Thank you. -- openssl-users mailing list To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users