RE: <Replacement for RSA_public_decrypt>

["Narayana, Sunil Kumar" <sanarayana@xxxxxxxx>]

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@xxxxxxxxx>
Sent: 29 January 2021 17:24
To: Narayana, Sunil Kumar <sanarayana@xxxxxxxx>
Cc: openssl-users@xxxxxxxxxxx
Subject: Re: <Replacement for RSA_public_decrypt>

 

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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 ?

 

Thanks,

Thulasi.

 

On Fri, 29 Jan 2021 at 16:59, Narayana, Sunil Kumar <sanarayana@xxxxxxxx> 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

We need to use an RSA private key

 

Please suggest.

 

Regards,

Sunil

From: Thulasi Goriparthi <thulasi.goriparthi@xxxxxxxxx>
Sent: 29 January 2021 13:07
To: Narayana, Sunil Kumar <sanarayana@xxxxxxxx>
Cc: openssl-users@xxxxxxxxxxx
Subject: Re: <Replacement for RSA_public_decrypt>

 

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Hope, you are referring to https://www.openssl.org/docs/man1.0.2/man3/EVP_PKEY_encrypt.html

 

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@xxxxxxxx> 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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bool DecryptSignature( string publicKey, string signature, string & keyDecrypted)
{
    ostringstream  pem;
    pem << "-----BEGIN PUBLIC KEY-----" << endl;
    while (publicKey.length() > 64)
    {
        pem << publicKey.substr(0,64) << endl;
        publicKey.erase(0,64);
    }
    if ( !publicKey.empty() )
    {
        pem << publicKey << endl;
    }
    pem << "-----END PUBLIC KEY-----" << endl;

    RSA* rsa= CreateRSAPubKey(pem.str().c_str() );
    if ( rsa == NULL )
    {
        return false;
    }

    char *buffer;
    uint32 len;

    Base64Decode(signature, &buffer, &len );
    int32 decryptedLen=RSA_size(rsa);
    unsigned char decrypted[decryptedLen+1];
    int  retlen = RSA_public_decrypt(len, (unsigned char*)buffer,decrypted,rsa, RSA_PKCS1_PADDING) ;

    RSA_free(rsa);
    free(buffer);
    if ( retlen > 0 )
    {
        //lint -e{571} Suspicious cast - decrypted contains ascii bytes representation of hash of signature
        keyDecrypted=string((char*)decrypted, (size_t) retlen );
        return true;
    }
    else
    {
        return false;
    }
}

RSA* CreateRSAPubKey(const char* key)
{
    RSA *rsa = NULL;
    BIO *keybio ;
    keybio = BIO_new_mem_buf((void*)key, -1); // !!!
    if (!keybio)
    {
        return NULL;
    }
    rsa = PEM_read_bio_RSA_PUBKEY(keybio, NULL, NULL, NULL);  // !!!
    if(!rsa )   
    {
        return NULL;
    }
    BIO_free(keybio); // !!!
    return rsa;
}