File content as of revision 13:0a80b49a5e78:

#include <stdint.h>
#include <alloca.h>

#include "prf.h"

void TlsPrfMasterSecret(uint8_t * preMasterSecret, uint8_t* clientRandom, uint8_t* serverRandom, uint8_t* output48)
{
    uint8_t* seed = alloca(13 + 32 + 32);
    for (int i = 0; i < 13; i++) seed[i          ] = "master secret"[i];
    for (int i = 0; i < 32; i++) seed[i + 13     ] = clientRandom[i];
    for (int i = 0; i < 32; i++) seed[i + 13 + 32] = serverRandom[i];
    
    uint8_t* hash = alloca(64);
    PrfHmacSha256(preMasterSecret, 48, seed, 13 + 32 + 32, 2, hash); //2 iterations will generate 64 bytes
    for (int i = 0; i < 48; i++) output48[i] = hash[i];              //just take the first 48 bytes
}

void TlsPrfKeys(uint8_t * masterSecret, uint8_t* clientRandom, uint8_t* serverRandom, uint8_t* client_MAC_key_20,
                                                                                      uint8_t* server_MAC_key_20,
                                                                                      uint8_t* client_key_16,
                                                                                      uint8_t* server_key_16)
{
    uint8_t* seed = alloca(13 + 32 + 32);
    for (int i = 0; i < 13; i++) seed[i          ] = "key expansion"[i];
    for (int i = 0; i < 32; i++) seed[i + 13     ] = serverRandom[i]; //Notice the order relative to the master secret algorithm
    for (int i = 0; i < 32; i++) seed[i + 13 + 32] = clientRandom[i];
    
    uint8_t* hash = alloca(128);                                  //4 iterations of 32 bytes
    PrfHmacSha256(masterSecret, 48, seed, 13 + 32 + 32, 4, hash); //4 iteration will generate the keys required
    for (int i = 0; i < 20; i++) client_MAC_key_20[i] = hash[i     ];
    for (int i = 0; i < 20; i++) server_MAC_key_20[i] = hash[i + 20];
    for (int i = 0; i < 16; i++) client_key_16[i]     = hash[i + 40];
    for (int i = 0; i < 16; i++) server_key_16[i]     = hash[i + 56];
}

void TlsPrfServerFinished(uint8_t * masterSecret, uint8_t* handshakeHash, uint8_t* output12)
{
    uint8_t* seed = alloca(15 + 32);
    for (int i = 0; i < 15; i++) seed[i     ] = "server finished"[i];
    for (int i = 0; i < 32; i++) seed[i + 15] = handshakeHash[i];
    
    uint8_t* hash = alloca(32);
    PrfHmacSha256(masterSecret, 48, seed, 15 + 32, 1, hash);
    for (int i = 0; i < 12; i++) output12[i] = hash[i];
}
void TlsPrfClientFinished(uint8_t * masterSecret, uint8_t* handshakeHash, uint8_t* output12)
{
    uint8_t* seed = alloca(15 + 32);
    for (int i = 0; i < 15; i++) seed[i     ] = "client finished"[i];
    for (int i = 0; i < 32; i++) seed[i + 15] = handshakeHash[i];
    
    uint8_t* hash = alloca(32);
    PrfHmacSha256(masterSecret, 48, seed, 15 + 32, 1, hash);
    for (int i = 0; i < 12; i++) output12[i] = hash[i];
}