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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I suspect the use of std::string and c_str(). Use a std::vector<char> instead.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> openssl-users [mailto:openssl-users-bounces@openssl.org]
<b>On Behalf Of </b>Jason Qian<br>
<b>Sent:</b> Friday, March 18, 2016 1:19 PM<br>
<b>To:</b> openssl-users@openssl.org<br>
<b>Subject:</b> [openssl-users] help on des_cblock<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">I am new on openSSl and run into a issue need some help.<br>
<br>
<br>
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.
<br>
<br>
Most of time, it is running correctly, but occasionally the server(java) throw a "Given final block not properly padded" exception.<br>
<br>
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)
<br>
<br>
<br>
Server -- java get from getEncoded()<br>
<br>
DES Key size (8) (1,-<span style="background:red">83,-113,-74,-77,109,84,88</span>)<br>
<br>
Client -- openSSL get from des_cblock struct<br>
<br>
DES Key size (8) (<span style="background:red">-83,-113,-74,-77,109,84,88</span>,8)
<br>
<br>
<o:p></o:p></p>
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<p class="MsoNormal">Thanks<o:p></o:p></p>
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<p class="MsoNormal">Jason<o:p></o:p></p>
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<p class="MsoNormal"><br>
Here is the C++ code<br>
<br>
void DiffieHellmanCipher::init(const std::string &Y){<br>
if (Y.length() == 0) {<br>
return;<br>
}<br>
if (m_DH == NULL) {<br>
return;<br>
}<br>
<br>
// convert the Y to BIGNUM<br>
BIGNUM *bnY = NULL;<br>
// Memory for bnY is allocated in BN_dec2bn call.<br>
if (!BN_dec2bn(&bnY, Y.c_str())) {<br>
if (bnY)<br>
BN_free(bnY);<br>
printf("Could not convert Diffie-Hellman Y value to BIGNUM");<br>
}<br>
<br>
// compute the secret key<br>
int dhSize = DH_size(m_DH);<br>
unsigned char *secretKey = (unsigned char*) new char[dhSize + 1];<br>
int secretKeyLen = DH_compute_key(secretKey, bnY, m_DH);<br>
BN_free(bnY);<br>
<br>
if (secretKeyLen < 8) {<br>
delete [] secretKey;<br>
printf("Error computing secret key: key length is too short");<br>
}<br>
<br>
// convert from raw form to odd parity DES key<br>
des_cblock desKey;<br>
memcpy(desKey, secretKey, 8);<br>
delete [] secretKey;<br>
DES_set_odd_parity(&desKey);<br>
<br>
<span style="background:#E69138"> //just print out des_cblock<br>
secretKeyString="(";<br>
char ch[10]="\0";<br>
for(int i=0;i<8;i++){<br>
sprintf(ch,"%d",(char)desKey[i]);<br>
secretKeyString+=ch;<br>
if(i != 7){<br>
secretKeyString+=",";<br>
}<br>
}<br>
secretKeyString+=")";<br>
</span><br>
<br>
int skRet;<br>
if ((skRet = DES_set_key(&desKey, &m_DESKey)) != 0) {<br>
delete [] secretKey;<br>
printf("Error computing secret key: generated key is weak");<br>
}<br>
<br>
m_bInited = true;<br>
}<o:p></o:p></p>
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