Hi All,
I am trying to write an SSL v3 handshake without using openssl
libraries. I have some problem with creation of MasterSecret in SSL v3. Here is
the code snippet of hardcoded client that i am experimenting with:
My ClientHello:
unsigned char buf[BUFSIZE] =
"\x01" /* Client Hello Message */
"\x00\x00\x29" /* Length */
"\x03\x00" /* Client Version */
"\x44\x44\x44\x44" /* GMT - just dummy values taken for now
*/
"\x66\x66\x66\x66\x66\x66\x66\x66"
"\x66\x66\x66\x66\x66\x66\x66\x66"
"\x66\x66\x66\x66\x66\x66\x66\x66"
"\x66\x66\x66\x66" /* Random Bytes 28 */
"\x00" /* Session ID Length */
"\x00\x02" /* Cipers */
"\x00\x35" /* One cipher - compatible with esx */
"\x01\x00"; /* Compression related details */
client_random is 28 bytes of 0x66 as of now
My Server Random is stored in ssl->server_random[28] array (excluding gmt 4
bytes)
My Client Random is stored in ssl->client_random[28] array (excluding gmt 4
bytes)
Note: I am guessing that client random and server random are 28 bytes long. I
am excluding the 4 bytes of gmt time spec from the random for calculating the
Master Secret
Master Secret Algorithm:
static const unsigned char *salt[10]={
(const unsigned char *)"A",
(const unsigned char *)"BB",
(const unsigned char *)"CCC",
(const unsigned char *)"DDDD",
(const unsigned char *)"EEEEE",
(const unsigned char *)"FFFFFF",
(const unsigned char *)"GGGGGGG",
(const unsigned char *)"HHHHHHHH",
(const unsigned char *)"IIIIIIIII",
(const unsigned char *)"JJJJJJJJJJ"
};
/*
* client_master_secret = MD5(client_premaster_secret + SHA('A' + client_random
+ server_random + client_premaster_secret)) +
* MD5(client_premaster_secret + SHA('BB' + client_random +
server_random + client_premaster_secret)) +
* MD5(client_premaster_secret + SHA('CCC' + client_random +
server_random + client_premaster_secret))
*
*/
tmp = ssl->client_master_secret;
for (i = 0; i < 3; i++) {
SHA_Init(&ctx1_sha);
SHA_Update(&ctx1_sha, salt[i], i + 1);
SHA_Update(&ctx1_sha, ssl->client_random, 28);
SHA_Update(&ctx1_sha, ssl->server_random, 28);
SHA_Update(&ctx1_sha, ssl->client_premaster_secret, 48);
SHA_Final(buf,&ctx1_sha);
MD5_Init(&ctx1_md5);
MD5_Update(&ctx1_md5, ssl->client_premaster_secret, 48);
MD5_Update(&ctx1_md5, buf, 20);
MD5_Final(tmp, &ctx1_md5);
tmp += 16;
}
However, when i analyze using the wireshark decoder for ssl (with the key
specified), i am getting a different MasterSecret calculated in Wireshark than
that calculated by me, though both use the same mechanism
Is something wrong with the MasterSecret calculation algorithm? Can i use a
generic OpenSSL v3 PRF function to calculate the same, without defining the
other parameters of ssl connection structure (because i am only required to
calculate the MasterSecret)?
Thanks and Regards,
Suchindra Chandrahas
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