c-libp2p/crypto/ephemeral.c
2017-02-09 03:34:12 -05:00

235 lines
7 KiB
C

#include <stdlib.h>
#include <string.h>
#include "mbedtls/config.h"
#include "mbedtls/ecdsa.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "libp2p/crypto/ephemeral.h"
struct StretchedKey* libp2p_crypto_ephemeral_stretched_key_new() {
struct StretchedKey* key = (struct StretchedKey*)malloc(sizeof(struct StretchedKey));
if (key != NULL) {
key->cipher_key = NULL;
key->cipher_size = 0;
key->iv = NULL;
key->iv_size = 0;
key->mac_key = NULL;
key->mac_size = 0;
}
return key;
}
void libp2p_crypto_ephemeral_stretched_key_free(struct StretchedKey* key) {
if (key != NULL) {
if (key->cipher_key != NULL)
free(key->cipher_key);
if (key->iv != NULL)
free(key->iv);
if (key->mac_key != NULL)
free(key->mac_key);
free(key);
}
}
struct EphemeralPrivateKey* libp2p_crypto_ephemeral_key_new(uint64_t priv, uint64_t x, uint64_t y, size_t num_bits) {
struct EphemeralPrivateKey* results = (struct EphemeralPrivateKey*)malloc(sizeof(struct EphemeralPrivateKey));
if (results != NULL) {
results->secret_key = priv;
results->num_bits = num_bits;
results->public_key = (struct EphemeralPublicKey*)malloc(sizeof(struct EphemeralPublicKey));
if (results->public_key == NULL) {
free(results);
results = NULL;
} else {
results->public_key->num_bits = num_bits;
results->public_key->x = x;
results->public_key->y = y;
results->public_key->bytes = NULL;
results->public_key->bytes_size = 0;
results->public_key->shared_key = NULL;
results->public_key->shared_key_size = 0;
}
}
return results;
}
void libp2p_crypto_ephemeral_key_free(struct EphemeralPrivateKey* in) {
if (in != NULL) {
if (in->public_key != NULL) {
if (in->public_key->bytes != NULL)
free(in->public_key->bytes);
if (in->public_key->shared_key != NULL)
free(in->public_key->shared_key);
free(in->public_key);
}
free(in);
}
}
void serialize_uint64(const uint64_t in, unsigned char out[8]) {
out[0] = in >> 56;
out[1] = in >> 48;
out[2] = in >> 40;
out[3] = in >> 32;
out[4] = in >> 24;
out[5] = in >> 16;
out[6] = in >> 8;
out[7] = in;
}
uint64_t unserialize_uint64(unsigned char in[8]) {
uint64_t out = 0;
out = (out << 8) | in[0];
out = (out << 8) | in[1];
out = (out << 8) | in[2];
out = (out << 8) | in[3];
out = (out << 8) | in[4];
out = (out << 8) | in[5];
out = (out << 8) | in[6];
out = (out << 8) | in[7];
return out;
}
/***
* Take the public pieces of an ephemeral key and turn them into a byte stream
* @param bit_size the curve bit size
* @param x the x parameter of the ephemeral key
* @param y the y parameter of the ephemeral key
* @param results where to put the bytes
* @param bytes_written how many bytes were written to results
* @returns true(1) on success, otherwise false(0)
*/
int libp2p_crypto_ephemeral_point_marshal(int bit_size, uint64_t x, uint64_t y, unsigned char** results, size_t* bytes_written) {
int byteLen = (bit_size + 7) >> 3;
*results = (unsigned char*)malloc(2*byteLen+1);
*results[0] = 4; // uncompressed point
int uint64_len = 8;
unsigned char buffer[8];
serialize_uint64(x, &buffer[0]);
memcpy(&(*results)[1 + byteLen - uint64_len], &buffer[0], 8);
serialize_uint64(y, &buffer[0]);
memcpy(&(*results)[1 + 2*byteLen - uint64_len], &buffer[0], 8);
*bytes_written = 2 * byteLen + 1;
return 1;
}
int libp2p_crypto_ephemeral_point_unmarshal(int bit_size, unsigned char* buffer, size_t buffer_length, uint64_t* x, uint64_t* y) {
int byteLen = (bit_size + 7) >> 3;
if (buffer_length != 2 * byteLen + 1)
return 0;
if (buffer[0] != 4)
return 0;
unsigned char temp[8];
memcpy((char*)temp, &buffer[1], 8);
*x = unserialize_uint64(temp);
memcpy((char*)temp, &buffer[9], 8);
*y = unserialize_uint64(temp);
return 1;
}
/**
* Generate a Ephemeral keypair
* @param curve the curve to use (P-256, P-384, or P-521)
* @param private_key the struct to store the generated key
* @returns true(1) on success, otherwise false(0)
*/
int libp2p_crypto_ephemeral_keypair_generate(char* curve, struct EphemeralPrivateKey** private_key_ptr) {
int retVal = 0;
mbedtls_ecdsa_context ctx;
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
struct EphemeralPrivateKey* private_key = NULL;
struct EphemeralPublicKey* public_key = NULL;
int selected_curve = 0;
char* pers = "bitShares"; // data for seeding random number generator
if (strcmp(curve, "P-256") == 0)
selected_curve = MBEDTLS_ECP_DP_SECP256R1;
else if (strcmp(curve, "P-384") == 0)
selected_curve = MBEDTLS_ECP_DP_SECP384R1;
else
selected_curve = MBEDTLS_ECP_DP_SECP521R1;
mbedtls_ecdsa_init(&ctx);
// seed random number generator
mbedtls_entropy_init(&entropy);
mbedtls_ctr_drbg_init(&ctr_drbg);
if (mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy, (const unsigned char*)pers, strlen(pers)) != 0)
goto exit;
// generate key
if (mbedtls_ecdsa_genkey(&ctx, selected_curve, mbedtls_ctr_drbg_random, &ctr_drbg) != 0)
goto exit;
*private_key_ptr = libp2p_crypto_ephemeral_key_new(*ctx.d.p, *ctx.Q.X.p, *ctx.Q.Y.p, ctx.grp.nbits);
private_key = *private_key_ptr;
public_key = private_key->public_key;
// Fill in more of the public key
libp2p_crypto_ephemeral_point_marshal(public_key->num_bits, public_key->x, public_key->y, &public_key->bytes, &public_key->bytes_size);
// build shared key, another part of public_key
//mbedtls_ecp_group grp;
mbedtls_ecp_point point;
//mbedtls_ecp_group_init(&grp);
mbedtls_ecp_point_init(&point);
if (mbedtls_ecp_mul(&ctx.grp, &point, &ctx.d, &ctx.Q, mbedtls_ctr_drbg_random, &ctr_drbg) != 0)
goto exit;
public_key->shared_key_size = 8;
public_key->shared_key = (unsigned char*)malloc(8);
serialize_uint64(*point.X.p, public_key->shared_key);
// ship all this stuff back to the caller
retVal = 1;
exit:
mbedtls_ecp_point_free(&point);
mbedtls_ctr_drbg_free(&ctr_drbg);
mbedtls_entropy_free(&entropy);
mbedtls_ecdsa_free(&ctx);
return retVal;
}
/**
* Generate a public key from a private key
* @param public key
* @param results the results
* @param bytes_written the number of bytes written
* @returns true(1) on success, otherwise false(0)
*/
int libp2p_crypto_ephemeral_keypair_to_public_bytes(struct EphemeralPublicKey* public_key, unsigned char** results, size_t* bytes_written) {
return libp2p_crypto_ephemeral_point_marshal(public_key->num_bits, public_key->x, public_key->y, results, bytes_written);
}
/***
* Generate a shared secret from a private key
* @param private key
* @param results
*/
int libp2p_crypto_ephemeral_keypair_to_shared_secret(struct EphemeralPrivateKey* private_key, unsigned char** results, size_t* bytes_written) {
// grab a scalar mult
// in GO, ScalarMult turns the bytes of the private key into a multiplier
// for the points
/*
* Multiplication R = m * P
*/
/*
int mbedtls_ecp_mul( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
const mbedtls_mpi *m, const mbedtls_ecp_point *P,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
*/
// turn it into bytes
//TODO: implement
return 0;
}