<Replacement for RSA_public_decrypt>

[Thulasi Goriparthi]

I am not sure why the code you have shared is trying to decrypt the
signature.
If it is done as part of signature verification, don't do this. Use
the actual EVP_PKEY_verify API with corresponding public key.

If you certainly need the decrypted signature, you should do public
encryption with NONE padding.
A Private key is not necessary.

Thanks,
Thulasi

On Fri, 29 Jan 2021 at 17:47, Narayana, Sunil Kumar <sanarayana at rbbn.com>
wrote:

> Yeah, it sounds correct. But since it’s an old application code & we are
> not sure why was it done so, we are little worried to change.
>
> Can you please take a look the attachment which has the complete flow, and
> provide your views which helps us to change it to  PEM_read_PrivateKey()
> or variants as you suggested
>
>
>
> Regards,
>
> Sunil
>
>
>
> *From:* Thulasi Goriparthi <thulasi.goriparthi at gmail.com>
> *Sent:* 29 January 2021 17:24
> *To:* Narayana, Sunil Kumar <sanarayana at rbbn.com>
> *Cc:* openssl-users at openssl.org
> *Subject:* Re: <Replacement for RSA_public_decrypt>
>
>
> ------------------------------
>
> NOTICE: This email was received from an EXTERNAL sender
> ------------------------------
>
>
>
> Isn't it obvious to use PEM_read_PrivateKey() or variants to load the
> private key as EVP_PKEY
>
> and use EVP_PKEY_decrypt* as specified in
> https://www.openssl.org/docs/man1.0.2/man3/EVP_PKEY_decrypt.html
> <https://protect-us.mimecast.com/s/pIHaCqx23xSzZMNwiZOok8?domain=openssl.org>
> ?
>
>
>
> Thanks,
>
> Thulasi.
>
>
>
> On Fri, 29 Jan 2021 at 16:59, Narayana, Sunil Kumar <sanarayana at rbbn.com>
> wrote:
>
> Hi Thulasi,
>
>
>
> Currently in (1.0.1) we are following the following sequence, which now
> need to replace with EVP.
>
>
>
> *Current sequence*
>
>
>
> //to create RSA pubkey
>
> rsa = PEM_read_bio_RSA_PUBKEY(keybio, NULL, NULL, NULL);  // !!!
>
>
>
> //to decrypt using RSA utility
>
> RSA_public_decrypt(len, (unsigned char*)buffer,decrypted,rsa,
> RSA_PKCS1_PADDING) ;
>
>
>
> As you mentioned , if we use PEM_read_bio_PUBKEY to get EVP_PKEY, it will
> be a pubkey right ? but in order to decrypt as per the example in
> https://www.openssl.org/docs/manmaster/man3/EVP_PKEY_decrypt_init.html
> <https://protect-us.mimecast.com/s/iJORCrkY3ki1EBZJTzdO87?domain=openssl.org>
>
> We need to use an RSA private key
>
>
>
> Please suggest.
>
>
>
> Regards,
>
> Sunil
>
> *From:* Thulasi Goriparthi <thulasi.goriparthi at gmail.com>
> *Sent:* 29 January 2021 13:07
> *To:* Narayana, Sunil Kumar <sanarayana at rbbn.com>
> *Cc:* openssl-users at openssl.org
> *Subject:* Re: <Replacement for RSA_public_decrypt>
>
>
> ------------------------------
>
> NOTICE: This email was received from an EXTERNAL sender
> ------------------------------
>
>
>
> Hope, you are referring to
> https://www.openssl.org/docs/man1.0.2/man3/EVP_PKEY_encrypt.html
> <https://protect-us.mimecast.com/s/v2osCv2j32i2xk8Vtz2d4K?domain=openssl.org>
>
>
>
> Use PEM_read_bio_PUBKEY to get EVP_PKEY.
>
> eng is for engine reference. If you have no engine, it can be NULL.
>
>
>
> Thanks,
>
> Thulasi.
>
>
>
> On Fri, 29 Jan 2021 at 10:13, Narayana, Sunil Kumar <sanarayana at rbbn.com>
> wrote:
>
> Dear Openssl team,
>
>
>
>                 While migrating from 1.0.2 to 3.0 we observe that
> RSA_public_decrypt() API been deprecated in 3.0.
>
> We referred the example provided in man page but we are not clear in
> generating the initial ‘key’ required to create CTX.
>
> Please suggest on (key , eng) params to proceed
>
>
>
> Also currently we are using PEM_read_bio_RSA_PUBKEY() to generate RSA, I
> think this might not require in case of EVP, please suggest.
>
>
>
> /*
>
>   * NB: assumes key, eng, in, inlen are already set up
>
>   * and that key is an RSA private key
>
>   */
>
> ctx = EVP_PKEY_CTX_new(key, eng);
>
>
>
>
>
> Regards,
>
> Sunil
>
>
>
>
>
>
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> Notice: This e-mail together with any attachments may contain information
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