Re: pgcrypto compilation error due to stack-allocated EVP_CIPHER_CTX

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От Asif Naeem
Тема Re: pgcrypto compilation error due to stack-allocated EVP_CIPHER_CTX
Дата
Msg-id CAEB4t-MA-mDacUt1EAV1qoVgtxr3TMCS4DiaKQT_t+wxdhSgfw@mail.gmail.com
обсуждение исходный текст
Ответ на Re: pgcrypto compilation error due to stack-allocated EVP_CIPHER_CTX  (Michael Paquier <michael.paquier@gmail.com>)
Ответы Re: [HACKERS] pgcrypto compilation error due to stack-allocated EVP_CIPHER_CTX  (Michael Paquier <michael.paquier@gmail.com>)
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It make sense. I would like to share more comments as following i.e.

static int
bf_check_supported_key_len(void)
{
...
     /* encrypt with 448bits key and verify output */
     evp_ctx = EVP_CIPHER_CTX_new();
     if (!evp_ctx)
          return 1;
     if (!EVP_EncryptInit_ex(evp_ctx, EVP_bf_ecb(), NULL, NULL, NULL))
          goto leave;
     if (!EVP_CIPHER_CTX_set_key_length(evp_ctx, 56))
          goto leave;
     if (!EVP_EncryptInit_ex(evp_ctx, NULL, NULL, key, NULL))
          goto leave;
     if (!EVP_EncryptUpdate(evp_ctx, out, &outlen, data, 8))
          goto leave;
     if (memcmp(out, res, 8) != 0)
          goto leave;                    /* Output does not match -> strong cipher is
                                         * not supported */
     status = 1;
leave:
     EVP_CIPHER_CTX_free(evp_ctx);
     return status;
}

It seems that it need to return 0 instead of 1 in case of failure i.e.

     /* encrypt with 448bits key and verify output */
     evp_ctx = EVP_CIPHER_CTX_new();
     if (!evp_ctx)
          return 0;

We can avoid multiple if conditions and goto statement something like i.e.

     if (EVP_EncryptInit_ex(evp_ctx, EVP_bf_ecb(), NULL, NULL, NULL) &&
         EVP_CIPHER_CTX_set_key_length(evp_ctx, 56) &&
         EVP_EncryptInit_ex(evp_ctx, NULL, NULL, key, NULL) &&
         EVP_EncryptUpdate(evp_ctx, out, &outlen, data, 8) &&
         memcmp(out, res, 8) == 0 )) /* Output does not match -> strong cipher is not supported */
     status = 1;
     EVP_CIPHER_CTX_free(evp_ctx);
     return status;
}

What is your opinion ?. I am hopeful I will be able to share all my findings tomorrow. Thanks.


On Wed, Dec 7, 2016 at 2:23 AM, Michael Paquier <michael.paquier@gmail.com> wrote:
On Tue, Dec 6, 2016 at 11:42 PM, Asif Naeem <anaeem.it@gmail.com> wrote:
> Thanks for updated patch. Although EVP_CIPHER_CTX_cleanup() seems deprecated
> in OpenSSL >= 1.1.0 i.e.
>
>> # if OPENSSL_API_COMPAT < 0x10100000L
>> #  define EVP_CIPHER_CTX_init(c)      EVP_CIPHER_CTX_reset(c)
>> #  define EVP_CIPHER_CTX_cleanup(c)   EVP_CIPHER_CTX_reset(c)
>> # endif
>
>
> I guess use of deprecated function is fine, until OpenSSL library support
> it.

We could use some ifdef block with the OpenSSL version number, but I
am not sure if that's worth complicating the code at this stage.
--
Michael

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