pirserver/ZT_LSORAMclient.cc

#include "pirclient.h"
#include "utils.h"

EC_KEY *ENCLAVE_PUBLIC_KEY = NULL;

class ZT_LSORAMClient : public PIRClient {

public:
    ZT_LSORAMClient();

    // Create a PIR query.  The plainquery must be exactly 32 bytes
    // long.
    virtual void create(const string &plainquery, const string &params,
        void *&queryid, string &pirquery);

    //Helper functions for create()
    void setupEnclavePublicKey(const string &params);
    int encryptLSORAMRequest(EC_KEY* target_public_key,
        unsigned char *serialized_request, uint32_t request_size, unsigned char
        **encrypted_request, unsigned char **client_pubkey, uint32_t *pubkey_size_x, 
        uint32_t *pubkey_size_y, unsigned char **ecdh_aes_key, unsigned char **iv, 
        unsigned char **tag);

    // Extract the plaintext response from a PIR response.  Returns
    // true if successful, false if unsuccessful.
    virtual bool extract(void *&queryid, const string &pirresponse,
        string &plainresponse);

    // Helper functions for extract()
    int decryptLSORAMResponse(unsigned char *encrypted_response, 
        uint32_t response_size, unsigned char *tag, unsigned char *aes_key,
        unsigned char *iv, unsigned char **response); 
};

ZT_LSORAMClient::ZT_LSORAMClient() {
}

// Put anything you'll need to decrypt the response in here
struct Decryptstate {
    //The AES-key used to encrypt query
    string decrypt_key;
    string iv;
};


/*

Inputs: a target pub key, a seriailzed request and request size.
Outputs: instantiates and populates:
          client_pubkey, aes_key (from target_pubkey and generated client_pubkey ECDH)
          iv, encrypted request and tag for the request
*/
int ZT_LSORAMClient::encryptLSORAMRequest(EC_KEY* target_public_key, unsigned char *serialized_request,
     uint32_t request_size, unsigned char **encrypted_request, unsigned char **client_pubkey,
     uint32_t *pubkey_size_x, uint32_t *pubkey_size_y, unsigned char **ecdh_aes_key, 
     unsigned char **iv, unsigned char **tag){

  //Generate a new key
  EC_KEY *ephemeral_key = NULL;
  BIGNUM *x, *y;
  x = BN_new();
  y = BN_new();
  BN_CTX *bn_ctx = BN_CTX_new();
  const EC_GROUP *curve = NULL;

  if(NULL == (curve = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1)))
    fprintf(stderr, "ZT_LSORAMClient: Setting EC_GROUP failed \n");

  ephemeral_key = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
  if(ephemeral_key==NULL)
    fprintf(stderr, "ZT_LSORAMClient: EC_KEY_new_by_curve_name Fail\n");

  int ret = EC_KEY_generate_key(ephemeral_key);
  if(ret!=1)
    fprintf(stderr, "ZT_LSORAMClient: EC_KEY_generate_key Fail\n");

  const EC_POINT *pub_point;
  pub_point = EC_KEY_get0_public_key((const EC_KEY *) ephemeral_key);
  if(pub_point == NULL)
    fprintf(stderr, "ZT_LSORAMClient: EC_KEY_get0_public_key Fail\n");
      
  ret = EC_POINT_get_affine_coordinates_GFp(curve, pub_point, x, y, bn_ctx);
  if(ret==0)
    fprintf(stderr, "ZT_LSORAMClient: EC_POINT_get_affine_coordinates_GFp Failed \n");
      
  unsigned char *bin_x, *bin_y;
  uint32_t size_bin_x = BN_num_bytes(x);
  uint32_t size_bin_y = BN_num_bytes(y);
  printf("(%d, %d)\n", size_bin_x, size_bin_y);
  bin_x = (unsigned char*) malloc(EC_KEY_SIZE);
  bin_y = (unsigned char*) malloc(EC_KEY_SIZE);
  BN_bn2bin(x, bin_x);
  BN_bn2bin(y, bin_y);
  *pubkey_size_x = size_bin_x;
  *pubkey_size_y = size_bin_y;
  *client_pubkey = (unsigned char*) malloc(size_bin_x + size_bin_y);
  memcpy(*client_pubkey, bin_x, size_bin_x);
  memcpy(*client_pubkey + size_bin_x, bin_y, size_bin_y);

  /*
  unsigned char *ptr = *client_pubkey;
  printf("Serialized Client's Public Key in encryptLSORAM :\n");
  for(int t = 0; t < size_bin_x; t++)
  printf("%02X", ptr[t]);
  printf("\n");
  printf("Serialized Client's Public Key in encryptLSORAM :\n");
  for(int t = 0; t < size_bin_y; t++)
    printf("%02X", ptr[size_bin_x + t]);
  printf("\n");
  */

  uint32_t field_size = EC_GROUP_get_degree(EC_KEY_get0_group(target_public_key));
  uint32_t secret_len = (field_size+7)/8;
  unsigned char *secret = (unsigned char*) malloc(secret_len);
  //Returns a 32 byte secret	
  secret_len = ECDH_compute_key(secret, secret_len, EC_KEY_get0_public_key(target_public_key),
					  ephemeral_key, NULL);

  //Sample IV;
  *ecdh_aes_key = (unsigned char*) malloc (KEY_LENGTH);
  *iv = (unsigned char*) malloc (IV_LENGTH);
 
  memcpy(*ecdh_aes_key, secret, KEY_LENGTH);
  memcpy(*iv, secret + KEY_LENGTH, IV_LENGTH);

  /*
  unsigned char *ecdh_ptr = (unsigned char *) *ecdh_aes_key;
  unsigned char *iv_ptr = (unsigned char *) *iv;
  
  printf("KEY_LENGTH = %d\n", KEY_LENGTH);
  printf("ecdh_key computed by Client :\n");
  for(int t = 0; t < KEY_LENGTH; t++)
    printf("%02X",  ecdh_ptr[t]);
  printf("\n");
  printf("iv computed by Client :\n");
  for(int t = 0; t < IV_LENGTH; t++)
    printf("%02X", iv_ptr[t]);
  printf("\n");
  */

  BN_CTX_free(bn_ctx);

  *encrypted_request = (unsigned char*) malloc (request_size);
  *tag = (unsigned char*) malloc (TAG_SIZE);

  uint32_t encrypted_request_size;
  /*
  printf("Request bytes before encrypting: \n"); 
  for(int t = 0; t < request_size; t++)
    printf("%02X", serialized_request[t]);
  printf("\n"); 
  */
  encrypted_request_size = AES_GCM_128_encrypt(serialized_request, request_size,
           NULL, 0, (unsigned char*) *ecdh_aes_key, (unsigned char*) *iv, 
           IV_LENGTH, *encrypted_request, *tag);

  /*
  unsigned char*tag_ptr = *tag;
  printf("Tag bytes after encryption: \n"); 
  for(uint32_t t = 0; t < TAG_SIZE; t++)
    printf("%02X", tag_ptr[t]);
  printf("\n"); 
 
  printf("Request_size = %d, Encrypted_request_size = %d,\n", request_size, encrypted_request_size); 
  printf("Request bytes after encrypting: \n");
  unsigned char *encrypted_ptr = (unsigned char*) *encrypted_request;
  for(uint32_t t = 0; t < encrypted_request_size; t++)
    printf("%02X",  encrypted_ptr[t]);
  printf("\n"); 
  */
  return encrypted_request_size;
}

void ZT_LSORAMClient::setupEnclavePublicKey(const string &params){
  const char *serialized_key;
  unsigned char bin_x[PRIME256V1_KEY_SIZE];
  unsigned char bin_y[PRIME256V1_KEY_SIZE];
  BIGNUM *x, *y;
  EC_GROUP *curve;

  if(NULL == (curve = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1)))
	fprintf(stderr, "ZT_LSORAMClient:Setting EC_GROUP failed \n");
  EC_POINT *pub_point = EC_POINT_new(curve);

  serialized_key = params.c_str();
  memcpy(bin_x, serialized_key, PRIME256V1_KEY_SIZE);
  memcpy(bin_y, serialized_key + PRIME256V1_KEY_SIZE, PRIME256V1_KEY_SIZE);

  //Load the Enclave Public Key
  ENCLAVE_PUBLIC_KEY = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
  
  BN_CTX *bn_ctx = BN_CTX_new();
  x = BN_bin2bn(bin_x, PRIME256V1_KEY_SIZE, NULL);
  y = BN_bin2bn(bin_y, PRIME256V1_KEY_SIZE, NULL);
  if(EC_POINT_set_affine_coordinates_GFp(curve, pub_point, x, y, bn_ctx)==0)
	  fprintf(stderr, "ZT_LSORAMClient: EC_POINT_set_affine_coordinates FAILED \n");

  if(EC_KEY_set_public_key(ENCLAVE_PUBLIC_KEY, pub_point)==0)
	  fprintf(stderr, "ZT_LSORAMClient: EC_KEY_set_public_key FAILED \n");

  BN_CTX_free(bn_ctx);
}

void
ZT_LSORAMClient::create(const string &plainquery, const string &params,
        void *&queryid, string &pirquery)
{

  // TODO: In ZT_LSORAMClient Lookupquery should be:
  // encrypted_query||tag_in||pk_x_size||pk_y_size||client_pubkey
  // client_pubkey (of size pk_x_size+pk_y_size)

  fprintf(stderr, "ZT_LSORAMClient: Starting create() ");

  if (plainquery.length() == 32) {
  //if (plainquery.length() == 32 && params.length() == 64) {
    //Setup Enclave_Pub_key
    setupEnclavePublicKey(params);
    fprintf(stderr, "ZT_LSORAMClient Done with setupEnclavePublicKey()\n");
 
    //Encrypt the query
    unsigned char *request = (unsigned char*) plainquery.c_str(); 
    unsigned char *tag, *encrypted_request, *ecdh_aes_key, *iv, *client_pubkey;
    uint32_t pubkey_size_x, pubkey_size_y;
    
    fprintf(stderr, "ZT_LSORAMClient: In create, HSDesc Key = ");
    for(int i = 0;i<BLINDED_KEY_SIZE; i++){
      fprintf(stderr, "%02X", request[i]);
    } 
    fprintf(stderr, "\n");

    encryptLSORAMRequest(ENCLAVE_PUBLIC_KEY,(unsigned char*) request, BLINDED_KEY_SIZE, 
           &encrypted_request, &client_pubkey, &pubkey_size_x, &pubkey_size_y,
           &ecdh_aes_key, &iv, &tag);

    // Format encrypted query into pirquery as :
    // encrypted_query||tag_in||pk_x_size||pk_y_size||client_pubkey
    // client_pubkey (of size pk_x_size+pk_y_size)
    uint32_t pirquery_cstr_size = BLINDED_KEY_SIZE + TAG_SIZE 
             + (2 * sizeof(uint32_t)) + pubkey_size_x + pubkey_size_y;
    unsigned char *pirquery_cstr = (unsigned char*) malloc(pirquery_cstr_size);

    unsigned char *ptr = pirquery_cstr;
    memcpy(ptr, encrypted_request, BLINDED_KEY_SIZE);
    ptr+=BLINDED_KEY_SIZE;
    memcpy(ptr, tag, TAG_SIZE);
    ptr+=TAG_SIZE;
    memcpy(ptr, &pubkey_size_x, sizeof(uint32_t));
    ptr+=sizeof(uint32_t);
    memcpy(ptr, &pubkey_size_y, sizeof(uint32_t)); 
    ptr+=sizeof(uint32_t);
    memcpy(ptr, client_pubkey, pubkey_size_x+pubkey_size_y);
    pirquery.assign((const char*) pirquery_cstr, pirquery_cstr_size);   

    //Store shared session key into DecryptState
    Decryptstate *ds = new Decryptstate();

    fprintf(stderr, "ZT_LSORAMClient: In create, AES_KEY = ");
    for(int i = 0;i<KEY_LENGTH; i++){
      fprintf(stderr, "%02X", ecdh_aes_key[i]);
    } 

    ds->decrypt_key.assign((const char*) ecdh_aes_key, KEY_LENGTH);
    ds->iv.assign((const char*) iv, IV_LENGTH);
    queryid = ds; 

    //Free all buffers
    free(pirquery_cstr);
    free(tag);
    free(client_pubkey);
    free(ecdh_aes_key);
    free(iv);
    free(encrypted_request); 
  }
  else{
    fprintf(stderr, "Error ZT_LSORAMClient: plainquery.length or params.length!= 32");
  }
}


int ZT_LSORAMClient::decryptLSORAMResponse(unsigned char *encrypted_response, uint32_t response_size, 
    unsigned char *tag, unsigned char *aes_key, unsigned char *iv, unsigned char **response) {

  *response = (unsigned char*) malloc (response_size);
  AES_GCM_128_decrypt(encrypted_response, response_size, NULL, 0, tag, aes_key, iv, IV_LENGTH, *response);
  return response_size;
}

bool
ZT_LSORAMClient::extract(void *&queryid, const string &pirresponse,
        string &plainresponse)
{

  fprintf(stderr, "ZT_LSORAMClient: Starting extract()\n");
  //pirresponse = encrypted_response||tag_out
  if(pirresponse.length()!=(DESCRIPTOR_MAX_SIZE+TAG_SIZE)){
    fprintf(stderr, "ZT_LSORAMClient: pirresponse size does not match expected value" 
           "(DESCRIPTOR_MAX_SIZE + TAG_SIZE)\n");
    return 0;
  }  
  
  Decryptstate *ds = (Decryptstate *)queryid;
  
  unsigned char *aes_key = (unsigned char*) ds->decrypt_key.c_str();
  unsigned char *iv = (unsigned char*) ds->iv.c_str();

  fprintf(stderr, "ZT_LSORAMClient: In extract, AES_KEY = ");
  for(int i = 0;i<KEY_LENGTH; i++){
    fprintf(stderr, "%02X", aes_key[i]);
  } 

  string encrypted_response = pirresponse.substr(0, DESCRIPTOR_MAX_SIZE);
  string tag_out = pirresponse.substr(DESCRIPTOR_MAX_SIZE, TAG_SIZE);  
  unsigned char *response;
 
  decryptLSORAMResponse((unsigned char *)encrypted_response.c_str(), 
         DESCRIPTOR_MAX_SIZE, (unsigned char*) tag_out.c_str(), aes_key, iv, 
         &response); 
   
  delete ds;
  queryid = NULL;

  unsigned char *value_ptr = response;
  fprintf(stderr, "ZT_LSORAMClient: In extract, after decryption");
  fprintf(stderr, "ZT_LSORAMClient: (First 32 bytes of) HSDesc Value = ");
  for(int i = 0; i <32; i++){
    fprintf(stderr, "%02X", value_ptr[i]);
  }    
  fprintf(stderr,"\n");

  //Populate plainresponse with response
  plainresponse.assign((const char*) response, DESCRIPTOR_MAX_SIZE);

  free(response);
  fprintf(stderr, "ZT_LSORAMClient:Finished extract()\n");
  return true;
   
}

int main(int argc, char **argv) {
    ZT_LSORAMClient client;

    client.mainloop();

    return 0;
}