decryption of MS office - c

Question

I'm working on decryption of encrypted MS Excel(RC4 encryption with SHA1),password is already known.In vs2010,I've could decrypt it correctly,however,my program hasto work under both Win and linux.And I have no idea to get the encryption key under linux right now,which is something like below under Win:
int getEncrypKey(HCRYPTKEY *hKey, int blocknum)
{
//------------------------H0 = H(salt, password)-----
BYTE *pbSaltandPwdHash = NULL;
DWORD dwSaltandPwdLen = 0;
pbSaltandPwdHash = SHA1_2(psalt, 16, ppwd, strlen(pwd)/2, &dwSaltandPwdLen);
printf("SHA1 of SaltandPwd:\n");
for(DWORD i = 0 ; i < dwSaltandPwdLen ; i++) {
printf("%2.2x ",pbSaltandPwdHash[i]);
}
printf("\n");
//------------------------H0 = H(salt, password)-----
//------------------------Hfinal = H(H0, block)-----
HCRYPTHASH hHash1 = 0;
CryptCreateHash( hCryptProv, CALG_SHA1, 0, 0, &hHash1) ;
CryptHashData( hHash1, pbSaltandPwdHash, dwSaltandPwdLen, 0) ;
CryptHashData( hHash1, (unsigned char*)&blocknum, sizeof(blocknum), 0) ;
//------------------------Hfinal = H(H0, block)-----
CryptDeriveKey(hCryptProv, CALG_RC4, hHash1, 0x00280000, hKey);
if(hHash1 != 0) CryptDestroyHash(hHash1);
if(pbSaltandPwdHash != NULL) free(pbSaltandPwdHash);
return 0;
}
I knew how to get H0 under linux,but I dont know how to get the hHash1 and hKey.

Answer 1

This post sounds like it does the same thing: Implement Windows CryptoAPI CryptDeriveKey Using OpenSSL APIs
A more general way of generating hashes in openssl is below:
Before you do anything:
#include <ssl/evp.h>
int main(int argc, char argv[]) // or in an "initialise" type function
{
OpenSSL_add_all_digests()
...
}
Then to generate the hash (error checking omitted):
const EVP_MD *digest;
EVP_MD_CTX context;
unsigned char hash[EVP_MAX_MD_SIZE];
unsigned int hash_len;
digest = EVP_get_digestbyname("sha1"); /* choose the hash type here */
EVP_MD_CTX_init(&context);
EVP_DigestInit_ex(&contxt, digest, NULL);
EVP_DigestUpdate(&context, pbSaltandPwdHash, dwSaltandPwdLen);
EVP_DigestUpdate(&context, &blocknum, sizeof(blocknum));
EVP_DigestFinal_ex(&context, hash, &hash_len);
EVP_MD_CTX_cleanup(&context);
/* Now use hash and hash_len as required */