[openssl-users] help on des_cblock
Jason Qian
jqian at tibco.com
Fri Mar 18 21:34:01 UTC 2016
Thanks,
Jason
On Fri, Mar 18, 2016 at 4:23 PM, Scott Neugroschl <scott_n at xypro.com> wrote:
> I suspect the use of std::string and c_str(). Use a std::vector<char>
> instead.
>
>
>
> *From:* openssl-users [mailto:openssl-users-bounces at openssl.org] *On
> Behalf Of *Jason Qian
> *Sent:* Friday, March 18, 2016 1:19 PM
> *To:* openssl-users at openssl.org
> *Subject:* [openssl-users] help on des_cblock
>
>
>
> I am new on openSSl and run into a issue need some help.
>
>
> In our application, the client and server perform a Diffie Hellman Key
> exchange and then encrypt the data The client is written in C++(using
> openSSL), and server is in java.
>
> Most of time, it is running correctly, but occasionally the server(java)
> throw a "Given final block not properly padded" exception.
>
> I added more log on the both side. When the exception happen, the keys
> are offset by one(for the working case, they are the same)
>
>
> Server -- java get from getEncoded()
>
> DES Key size (8) (1,-83,-113,-74,-77,109,84,88)
>
> Client -- openSSL get from des_cblock struct
>
> DES Key size (8) (-83,-113,-74,-77,109,84,88,8)
>
> Thanks
>
> Jason
>
>
> Here is the C++ code
>
> void DiffieHellmanCipher::init(const std::string &Y){
> if (Y.length() == 0) {
> return;
> }
> if (m_DH == NULL) {
> return;
> }
>
> // convert the Y to BIGNUM
> BIGNUM *bnY = NULL;
> // Memory for bnY is allocated in BN_dec2bn call.
> if (!BN_dec2bn(&bnY, Y.c_str())) {
> if (bnY)
> BN_free(bnY);
> printf("Could not convert Diffie-Hellman Y value to BIGNUM");
> }
>
> // compute the secret key
> int dhSize = DH_size(m_DH);
> unsigned char *secretKey = (unsigned char*) new char[dhSize + 1];
> int secretKeyLen = DH_compute_key(secretKey, bnY, m_DH);
> BN_free(bnY);
>
> if (secretKeyLen < 8) {
> delete [] secretKey;
> printf("Error computing secret key: key length is too short");
> }
>
> // convert from raw form to odd parity DES key
> des_cblock desKey;
> memcpy(desKey, secretKey, 8);
> delete [] secretKey;
> DES_set_odd_parity(&desKey);
>
> //just print out des_cblock
> secretKeyString="(";
> char ch[10]="\0";
> for(int i=0;i<8;i++){
> sprintf(ch,"%d",(char)desKey[i]);
> secretKeyString+=ch;
> if(i != 7){
> secretKeyString+=",";
> }
> }
> secretKeyString+=")";
>
>
> int skRet;
> if ((skRet = DES_set_key(&desKey, &m_DESKey)) != 0) {
> delete [] secretKey;
> printf("Error computing secret key: generated key is weak");
> }
>
> m_bInited = true;
> }
>
> --
> openssl-users mailing list
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>
>
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