ref: 94f2907dc40a6415a10c252cb9ba3971f1f7e838
dir: /third_party/boringssl/src/crypto/hpke/hpke.c/
/* Copyright (c) 2020, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <openssl/hpke.h>
#include <assert.h>
#include <string.h>
#include <openssl/aead.h>
#include <openssl/bytestring.h>
#include <openssl/curve25519.h>
#include <openssl/digest.h>
#include <openssl/ec.h>
#include <openssl/err.h>
#include <openssl/evp_errors.h>
#include <openssl/hkdf.h>
#include <openssl/mem.h>
#include <openssl/rand.h>
#include <openssl/sha.h>
#include "../fipsmodule/ec/internal.h"
#include "../internal.h"
// This file implements RFC 9180.
#define MAX_SEED_LEN X25519_PRIVATE_KEY_LEN
#define MAX_SHARED_SECRET_LEN SHA256_DIGEST_LENGTH
struct evp_hpke_kem_st {
uint16_t id;
size_t public_key_len;
size_t private_key_len;
size_t seed_len;
size_t enc_len;
int (*init_key)(EVP_HPKE_KEY *key, const uint8_t *priv_key,
size_t priv_key_len);
int (*generate_key)(EVP_HPKE_KEY *key);
int (*encap_with_seed)(const EVP_HPKE_KEM *kem, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, uint8_t *out_enc,
size_t *out_enc_len, size_t max_enc,
const uint8_t *peer_public_key,
size_t peer_public_key_len, const uint8_t *seed,
size_t seed_len);
int (*decap)(const EVP_HPKE_KEY *key, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, const uint8_t *enc,
size_t enc_len);
int (*auth_encap_with_seed)(const EVP_HPKE_KEY *key,
uint8_t *out_shared_secret,
size_t *out_shared_secret_len, uint8_t *out_enc,
size_t *out_enc_len, size_t max_enc,
const uint8_t *peer_public_key,
size_t peer_public_key_len, const uint8_t *seed,
size_t seed_len);
int (*auth_decap)(const EVP_HPKE_KEY *key, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, const uint8_t *enc,
size_t enc_len, const uint8_t *peer_public_key,
size_t peer_public_key_len);
};
struct evp_hpke_kdf_st {
uint16_t id;
// We only support HKDF-based KDFs.
const EVP_MD *(*hkdf_md_func)(void);
};
struct evp_hpke_aead_st {
uint16_t id;
const EVP_AEAD *(*aead_func)(void);
};
// Low-level labeled KDF functions.
static const char kHpkeVersionId[] = "HPKE-v1";
static int add_label_string(CBB *cbb, const char *label) {
return CBB_add_bytes(cbb, (const uint8_t *)label, strlen(label));
}
static int hpke_labeled_extract(const EVP_MD *hkdf_md, uint8_t *out_key,
size_t *out_len, const uint8_t *salt,
size_t salt_len, const uint8_t *suite_id,
size_t suite_id_len, const char *label,
const uint8_t *ikm, size_t ikm_len) {
// labeledIKM = concat("HPKE-v1", suite_id, label, IKM)
CBB labeled_ikm;
int ok = CBB_init(&labeled_ikm, 0) &&
add_label_string(&labeled_ikm, kHpkeVersionId) &&
CBB_add_bytes(&labeled_ikm, suite_id, suite_id_len) &&
add_label_string(&labeled_ikm, label) &&
CBB_add_bytes(&labeled_ikm, ikm, ikm_len) &&
HKDF_extract(out_key, out_len, hkdf_md, CBB_data(&labeled_ikm),
CBB_len(&labeled_ikm), salt, salt_len);
CBB_cleanup(&labeled_ikm);
return ok;
}
static int hpke_labeled_expand(const EVP_MD *hkdf_md, uint8_t *out_key,
size_t out_len, const uint8_t *prk,
size_t prk_len, const uint8_t *suite_id,
size_t suite_id_len, const char *label,
const uint8_t *info, size_t info_len) {
// labeledInfo = concat(I2OSP(L, 2), "HPKE-v1", suite_id, label, info)
CBB labeled_info;
int ok = CBB_init(&labeled_info, 0) && //
CBB_add_u16(&labeled_info, out_len) &&
add_label_string(&labeled_info, kHpkeVersionId) &&
CBB_add_bytes(&labeled_info, suite_id, suite_id_len) &&
add_label_string(&labeled_info, label) &&
CBB_add_bytes(&labeled_info, info, info_len) &&
HKDF_expand(out_key, out_len, hkdf_md, prk, prk_len,
CBB_data(&labeled_info), CBB_len(&labeled_info));
CBB_cleanup(&labeled_info);
return ok;
}
// KEM implementations.
// dhkem_extract_and_expand implements the ExtractAndExpand operation in the
// DHKEM construction. See section 4.1 of RFC 9180.
static int dhkem_extract_and_expand(uint16_t kem_id, const EVP_MD *hkdf_md,
uint8_t *out_key, size_t out_len,
const uint8_t *dh, size_t dh_len,
const uint8_t *kem_context,
size_t kem_context_len) {
// concat("KEM", I2OSP(kem_id, 2))
uint8_t suite_id[5] = {'K', 'E', 'M', kem_id >> 8, kem_id & 0xff};
uint8_t prk[EVP_MAX_MD_SIZE];
size_t prk_len;
return hpke_labeled_extract(hkdf_md, prk, &prk_len, NULL, 0, suite_id,
sizeof(suite_id), "eae_prk", dh, dh_len) &&
hpke_labeled_expand(hkdf_md, out_key, out_len, prk, prk_len, suite_id,
sizeof(suite_id), "shared_secret", kem_context,
kem_context_len);
}
static int x25519_init_key(EVP_HPKE_KEY *key, const uint8_t *priv_key,
size_t priv_key_len) {
if (priv_key_len != X25519_PRIVATE_KEY_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
return 0;
}
OPENSSL_memcpy(key->private_key, priv_key, priv_key_len);
X25519_public_from_private(key->public_key, priv_key);
return 1;
}
static int x25519_generate_key(EVP_HPKE_KEY *key) {
X25519_keypair(key->public_key, key->private_key);
return 1;
}
static int x25519_encap_with_seed(
const EVP_HPKE_KEM *kem, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, uint8_t *out_enc, size_t *out_enc_len,
size_t max_enc, const uint8_t *peer_public_key, size_t peer_public_key_len,
const uint8_t *seed, size_t seed_len) {
if (max_enc < X25519_PUBLIC_VALUE_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_BUFFER_SIZE);
return 0;
}
if (seed_len != X25519_PRIVATE_KEY_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
return 0;
}
X25519_public_from_private(out_enc, seed);
uint8_t dh[X25519_SHARED_KEY_LEN];
if (peer_public_key_len != X25519_PUBLIC_VALUE_LEN ||
!X25519(dh, seed, peer_public_key)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[2 * X25519_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, out_enc, X25519_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + X25519_PUBLIC_VALUE_LEN, peer_public_key,
X25519_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_enc_len = X25519_PUBLIC_VALUE_LEN;
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
static int x25519_decap(const EVP_HPKE_KEY *key, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, const uint8_t *enc,
size_t enc_len) {
uint8_t dh[X25519_SHARED_KEY_LEN];
if (enc_len != X25519_PUBLIC_VALUE_LEN ||
!X25519(dh, key->private_key, enc)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[2 * X25519_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, enc, X25519_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + X25519_PUBLIC_VALUE_LEN, key->public_key,
X25519_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(key->kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
static int x25519_auth_encap_with_seed(
const EVP_HPKE_KEY *key, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, uint8_t *out_enc, size_t *out_enc_len,
size_t max_enc, const uint8_t *peer_public_key, size_t peer_public_key_len,
const uint8_t *seed, size_t seed_len) {
if (max_enc < X25519_PUBLIC_VALUE_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_BUFFER_SIZE);
return 0;
}
if (seed_len != X25519_PRIVATE_KEY_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
return 0;
}
X25519_public_from_private(out_enc, seed);
uint8_t dh[2 * X25519_SHARED_KEY_LEN];
if (peer_public_key_len != X25519_PUBLIC_VALUE_LEN ||
!X25519(dh, seed, peer_public_key) ||
!X25519(dh + X25519_SHARED_KEY_LEN, key->private_key, peer_public_key)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[3 * X25519_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, out_enc, X25519_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + X25519_PUBLIC_VALUE_LEN, peer_public_key,
X25519_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + 2 * X25519_PUBLIC_VALUE_LEN, key->public_key,
X25519_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(key->kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_enc_len = X25519_PUBLIC_VALUE_LEN;
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
static int x25519_auth_decap(const EVP_HPKE_KEY *key,
uint8_t *out_shared_secret,
size_t *out_shared_secret_len, const uint8_t *enc,
size_t enc_len, const uint8_t *peer_public_key,
size_t peer_public_key_len) {
uint8_t dh[2 * X25519_SHARED_KEY_LEN];
if (enc_len != X25519_PUBLIC_VALUE_LEN ||
peer_public_key_len != X25519_PUBLIC_VALUE_LEN ||
!X25519(dh, key->private_key, enc) ||
!X25519(dh + X25519_SHARED_KEY_LEN, key->private_key, peer_public_key)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[3 * X25519_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, enc, X25519_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + X25519_PUBLIC_VALUE_LEN, key->public_key,
X25519_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + 2 * X25519_PUBLIC_VALUE_LEN, peer_public_key,
X25519_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(key->kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
const EVP_HPKE_KEM *EVP_hpke_x25519_hkdf_sha256(void) {
static const EVP_HPKE_KEM kKEM = {
/*id=*/EVP_HPKE_DHKEM_X25519_HKDF_SHA256,
/*public_key_len=*/X25519_PUBLIC_VALUE_LEN,
/*private_key_len=*/X25519_PRIVATE_KEY_LEN,
/*seed_len=*/X25519_PRIVATE_KEY_LEN,
/*enc_len=*/X25519_PUBLIC_VALUE_LEN,
x25519_init_key,
x25519_generate_key,
x25519_encap_with_seed,
x25519_decap,
x25519_auth_encap_with_seed,
x25519_auth_decap,
};
return &kKEM;
}
#define P256_PRIVATE_KEY_LEN 32
#define P256_PUBLIC_KEY_LEN 65
#define P256_PUBLIC_VALUE_LEN 65
#define P256_SEED_LEN 32
#define P256_SHARED_KEY_LEN 32
static int p256_public_from_private(uint8_t out_pub[P256_PUBLIC_VALUE_LEN],
const uint8_t priv[P256_PRIVATE_KEY_LEN]) {
const EC_GROUP *const group = EC_group_p256();
const uint8_t kAllZeros[P256_PRIVATE_KEY_LEN] = {0};
EC_SCALAR private_scalar;
EC_JACOBIAN public_point;
EC_AFFINE public_point_affine;
if (CRYPTO_memcmp(kAllZeros, priv, sizeof(kAllZeros)) == 0) {
OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
return 0;
}
if (!ec_scalar_from_bytes(group, &private_scalar, priv,
P256_PRIVATE_KEY_LEN) ||
!ec_point_mul_scalar_base(group, &public_point, &private_scalar) ||
!ec_jacobian_to_affine(group, &public_point_affine, &public_point)) {
return 0;
}
size_t out_len_x, out_len_y;
out_pub[0] = POINT_CONVERSION_UNCOMPRESSED;
ec_felem_to_bytes(group, &out_pub[1], &out_len_x, &public_point_affine.X);
ec_felem_to_bytes(group, &out_pub[33], &out_len_y, &public_point_affine.Y);
return 1;
}
static int p256_init_key(EVP_HPKE_KEY *key, const uint8_t *priv_key,
size_t priv_key_len) {
if (priv_key_len != P256_PRIVATE_KEY_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
return 0;
}
if (!p256_public_from_private(key->public_key, priv_key)) {
return 0;
}
OPENSSL_memcpy(key->private_key, priv_key, priv_key_len);
return 1;
}
static int p256_private_key_from_seed(uint8_t out_priv[P256_PRIVATE_KEY_LEN],
const uint8_t seed[P256_SEED_LEN]) {
// https://www.rfc-editor.org/rfc/rfc9180.html#name-derivekeypair
const uint8_t suite_id[5] = {'K', 'E', 'M',
EVP_HPKE_DHKEM_P256_HKDF_SHA256 >> 8,
EVP_HPKE_DHKEM_P256_HKDF_SHA256 & 0xff};
uint8_t dkp_prk[32];
size_t dkp_prk_len;
if (!hpke_labeled_extract(EVP_sha256(), dkp_prk, &dkp_prk_len, NULL, 0,
suite_id, sizeof(suite_id), "dkp_prk", seed,
P256_SEED_LEN)) {
return 0;
}
assert(dkp_prk_len == sizeof(dkp_prk));
const EC_GROUP *const group = EC_group_p256();
EC_SCALAR private_scalar;
for (unsigned counter = 0; counter < 256; counter++) {
const uint8_t counter_byte = counter & 0xff;
if (!hpke_labeled_expand(EVP_sha256(), out_priv, P256_PRIVATE_KEY_LEN,
dkp_prk, sizeof(dkp_prk), suite_id,
sizeof(suite_id), "candidate", &counter_byte,
sizeof(counter_byte))) {
return 0;
}
// This checks that the scalar is less than the order.
if (ec_scalar_from_bytes(group, &private_scalar, out_priv,
P256_PRIVATE_KEY_LEN)) {
return 1;
}
}
// This happens with probability of 2^-(32*256).
OPENSSL_PUT_ERROR(EVP, ERR_R_INTERNAL_ERROR);
return 0;
}
static int p256_generate_key(EVP_HPKE_KEY *key) {
uint8_t seed[P256_SEED_LEN];
RAND_bytes(seed, sizeof(seed));
if (!p256_private_key_from_seed(key->private_key, seed) ||
!p256_public_from_private(key->public_key, key->private_key)) {
return 0;
}
return 1;
}
static int p256(uint8_t out_dh[P256_SHARED_KEY_LEN],
const uint8_t my_private[P256_PRIVATE_KEY_LEN],
const uint8_t their_public[P256_PUBLIC_VALUE_LEN]) {
const EC_GROUP *const group = EC_group_p256();
EC_SCALAR private_scalar;
EC_FELEM x, y;
EC_JACOBIAN shared_point, their_point;
EC_AFFINE their_point_affine, shared_point_affine;
if (their_public[0] != POINT_CONVERSION_UNCOMPRESSED ||
!ec_felem_from_bytes(group, &x, &their_public[1], 32) ||
!ec_felem_from_bytes(group, &y, &their_public[33], 32) ||
!ec_point_set_affine_coordinates(group, &their_point_affine, &x, &y) ||
!ec_scalar_from_bytes(group, &private_scalar, my_private,
P256_PRIVATE_KEY_LEN)) {
OPENSSL_PUT_ERROR(EVP, ERR_R_INTERNAL_ERROR);
return 0;
}
ec_affine_to_jacobian(group, &their_point, &their_point_affine);
if (!ec_point_mul_scalar(group, &shared_point, &their_point,
&private_scalar) ||
!ec_jacobian_to_affine(group, &shared_point_affine, &shared_point)) {
OPENSSL_PUT_ERROR(EVP, ERR_R_INTERNAL_ERROR);
return 0;
}
size_t out_len;
ec_felem_to_bytes(group, out_dh, &out_len, &shared_point_affine.X);
assert(out_len == P256_SHARED_KEY_LEN);
return 1;
}
static int p256_encap_with_seed(const EVP_HPKE_KEM *kem,
uint8_t *out_shared_secret,
size_t *out_shared_secret_len, uint8_t *out_enc,
size_t *out_enc_len, size_t max_enc,
const uint8_t *peer_public_key,
size_t peer_public_key_len, const uint8_t *seed,
size_t seed_len) {
if (max_enc < P256_PUBLIC_VALUE_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_BUFFER_SIZE);
return 0;
}
if (seed_len != P256_SEED_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
return 0;
}
uint8_t private_key[P256_PRIVATE_KEY_LEN];
if (!p256_private_key_from_seed(private_key, seed)) {
return 0;
}
p256_public_from_private(out_enc, private_key);
uint8_t dh[P256_SHARED_KEY_LEN];
if (peer_public_key_len != P256_PUBLIC_VALUE_LEN ||
!p256(dh, private_key, peer_public_key)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[2 * P256_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, out_enc, P256_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + P256_PUBLIC_VALUE_LEN, peer_public_key,
P256_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_enc_len = P256_PUBLIC_VALUE_LEN;
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
static int p256_decap(const EVP_HPKE_KEY *key, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, const uint8_t *enc,
size_t enc_len) {
uint8_t dh[P256_SHARED_KEY_LEN];
if (enc_len != P256_PUBLIC_VALUE_LEN || //
!p256(dh, key->private_key, enc)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[2 * P256_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, enc, P256_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + P256_PUBLIC_VALUE_LEN, key->public_key,
P256_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(key->kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
static int p256_auth_encap_with_seed(
const EVP_HPKE_KEY *key, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, uint8_t *out_enc, size_t *out_enc_len,
size_t max_enc, const uint8_t *peer_public_key, size_t peer_public_key_len,
const uint8_t *seed, size_t seed_len) {
if (max_enc < P256_PUBLIC_VALUE_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_BUFFER_SIZE);
return 0;
}
if (seed_len != P256_SEED_LEN) {
OPENSSL_PUT_ERROR(EVP, EVP_R_DECODE_ERROR);
return 0;
}
uint8_t private_key[P256_PRIVATE_KEY_LEN];
if (!p256_private_key_from_seed(private_key, seed)) {
return 0;
}
p256_public_from_private(out_enc, private_key);
uint8_t dh[2 * P256_SHARED_KEY_LEN];
if (peer_public_key_len != P256_PUBLIC_VALUE_LEN ||
!p256(dh, private_key, peer_public_key) ||
!p256(dh + P256_SHARED_KEY_LEN, key->private_key, peer_public_key)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[3 * P256_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, out_enc, P256_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + P256_PUBLIC_VALUE_LEN, peer_public_key,
P256_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + 2 * P256_PUBLIC_VALUE_LEN, key->public_key,
P256_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(key->kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_enc_len = P256_PUBLIC_VALUE_LEN;
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
static int p256_auth_decap(const EVP_HPKE_KEY *key, uint8_t *out_shared_secret,
size_t *out_shared_secret_len, const uint8_t *enc,
size_t enc_len, const uint8_t *peer_public_key,
size_t peer_public_key_len) {
uint8_t dh[2 * P256_SHARED_KEY_LEN];
if (enc_len != P256_PUBLIC_VALUE_LEN ||
peer_public_key_len != P256_PUBLIC_VALUE_LEN ||
!p256(dh, key->private_key, enc) ||
!p256(dh + P256_SHARED_KEY_LEN, key->private_key, peer_public_key)) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PEER_KEY);
return 0;
}
uint8_t kem_context[3 * P256_PUBLIC_VALUE_LEN];
OPENSSL_memcpy(kem_context, enc, P256_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + P256_PUBLIC_VALUE_LEN, key->public_key,
P256_PUBLIC_VALUE_LEN);
OPENSSL_memcpy(kem_context + 2 * P256_PUBLIC_VALUE_LEN, peer_public_key,
P256_PUBLIC_VALUE_LEN);
if (!dhkem_extract_and_expand(key->kem->id, EVP_sha256(), out_shared_secret,
SHA256_DIGEST_LENGTH, dh, sizeof(dh),
kem_context, sizeof(kem_context))) {
return 0;
}
*out_shared_secret_len = SHA256_DIGEST_LENGTH;
return 1;
}
const EVP_HPKE_KEM *EVP_hpke_p256_hkdf_sha256(void) {
static const EVP_HPKE_KEM kKEM = {
/*id=*/EVP_HPKE_DHKEM_P256_HKDF_SHA256,
/*public_key_len=*/P256_PUBLIC_KEY_LEN,
/*private_key_len=*/P256_PRIVATE_KEY_LEN,
/*seed_len=*/P256_SEED_LEN,
/*enc_len=*/P256_PUBLIC_VALUE_LEN,
p256_init_key,
p256_generate_key,
p256_encap_with_seed,
p256_decap,
p256_auth_encap_with_seed,
p256_auth_decap,
};
return &kKEM;
}
uint16_t EVP_HPKE_KEM_id(const EVP_HPKE_KEM *kem) { return kem->id; }
size_t EVP_HPKE_KEM_public_key_len(const EVP_HPKE_KEM *kem) {
return kem->public_key_len;
}
size_t EVP_HPKE_KEM_private_key_len(const EVP_HPKE_KEM *kem) {
return kem->private_key_len;
}
size_t EVP_HPKE_KEM_enc_len(const EVP_HPKE_KEM *kem) { return kem->enc_len; }
void EVP_HPKE_KEY_zero(EVP_HPKE_KEY *key) {
OPENSSL_memset(key, 0, sizeof(EVP_HPKE_KEY));
}
void EVP_HPKE_KEY_cleanup(EVP_HPKE_KEY *key) {
// Nothing to clean up for now, but we may introduce a cleanup process in the
// future.
}
EVP_HPKE_KEY *EVP_HPKE_KEY_new(void) {
EVP_HPKE_KEY *key = OPENSSL_malloc(sizeof(EVP_HPKE_KEY));
if (key == NULL) {
return NULL;
}
EVP_HPKE_KEY_zero(key);
return key;
}
void EVP_HPKE_KEY_free(EVP_HPKE_KEY *key) {
if (key != NULL) {
EVP_HPKE_KEY_cleanup(key);
OPENSSL_free(key);
}
}
int EVP_HPKE_KEY_copy(EVP_HPKE_KEY *dst, const EVP_HPKE_KEY *src) {
// For now, |EVP_HPKE_KEY| is trivially copyable.
OPENSSL_memcpy(dst, src, sizeof(EVP_HPKE_KEY));
return 1;
}
void EVP_HPKE_KEY_move(EVP_HPKE_KEY *out, EVP_HPKE_KEY *in) {
EVP_HPKE_KEY_cleanup(out);
// For now, |EVP_HPKE_KEY| is trivially movable.
// Note that Rust may move this structure. See
// bssl-crypto/src/scoped.rs:EvpHpkeKey.
OPENSSL_memcpy(out, in, sizeof(EVP_HPKE_KEY));
EVP_HPKE_KEY_zero(in);
}
int EVP_HPKE_KEY_init(EVP_HPKE_KEY *key, const EVP_HPKE_KEM *kem,
const uint8_t *priv_key, size_t priv_key_len) {
EVP_HPKE_KEY_zero(key);
key->kem = kem;
if (!kem->init_key(key, priv_key, priv_key_len)) {
key->kem = NULL;
return 0;
}
return 1;
}
int EVP_HPKE_KEY_generate(EVP_HPKE_KEY *key, const EVP_HPKE_KEM *kem) {
EVP_HPKE_KEY_zero(key);
key->kem = kem;
if (!kem->generate_key(key)) {
key->kem = NULL;
return 0;
}
return 1;
}
const EVP_HPKE_KEM *EVP_HPKE_KEY_kem(const EVP_HPKE_KEY *key) {
return key->kem;
}
int EVP_HPKE_KEY_public_key(const EVP_HPKE_KEY *key, uint8_t *out,
size_t *out_len, size_t max_out) {
if (max_out < key->kem->public_key_len) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_BUFFER_SIZE);
return 0;
}
OPENSSL_memcpy(out, key->public_key, key->kem->public_key_len);
*out_len = key->kem->public_key_len;
return 1;
}
int EVP_HPKE_KEY_private_key(const EVP_HPKE_KEY *key, uint8_t *out,
size_t *out_len, size_t max_out) {
if (max_out < key->kem->private_key_len) {
OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_BUFFER_SIZE);
return 0;
}
OPENSSL_memcpy(out, key->private_key, key->kem->private_key_len);
*out_len = key->kem->private_key_len;
return 1;
}
// Supported KDFs and AEADs.
const EVP_HPKE_KDF *EVP_hpke_hkdf_sha256(void) {
static const EVP_HPKE_KDF kKDF = {EVP_HPKE_HKDF_SHA256, &EVP_sha256};
return &kKDF;
}
uint16_t EVP_HPKE_KDF_id(const EVP_HPKE_KDF *kdf) { return kdf->id; }
const EVP_MD *EVP_HPKE_KDF_hkdf_md(const EVP_HPKE_KDF *kdf) {
return kdf->hkdf_md_func();
}
const EVP_HPKE_AEAD *EVP_hpke_aes_128_gcm(void) {
static const EVP_HPKE_AEAD kAEAD = {EVP_HPKE_AES_128_GCM,
&EVP_aead_aes_128_gcm};
return &kAEAD;
}
const EVP_HPKE_AEAD *EVP_hpke_aes_256_gcm(void) {
static const EVP_HPKE_AEAD kAEAD = {EVP_HPKE_AES_256_GCM,
&EVP_aead_aes_256_gcm};
return &kAEAD;
}
const EVP_HPKE_AEAD *EVP_hpke_chacha20_poly1305(void) {
static const EVP_HPKE_AEAD kAEAD = {EVP_HPKE_CHACHA20_POLY1305,
&EVP_aead_chacha20_poly1305};
return &kAEAD;
}
uint16_t EVP_HPKE_AEAD_id(const EVP_HPKE_AEAD *aead) { return aead->id; }
const EVP_AEAD *EVP_HPKE_AEAD_aead(const EVP_HPKE_AEAD *aead) {
return aead->aead_func();
}
// HPKE implementation.
// This is strlen("HPKE") + 3 * sizeof(uint16_t).
#define HPKE_SUITE_ID_LEN 10
// The suite_id for non-KEM pieces of HPKE is defined as concat("HPKE",
// I2OSP(kem_id, 2), I2OSP(kdf_id, 2), I2OSP(aead_id, 2)).
static int hpke_build_suite_id(const EVP_HPKE_CTX *ctx,
uint8_t out[HPKE_SUITE_ID_LEN]) {
CBB cbb;
CBB_init_fixed(&cbb, out, HPKE_SUITE_ID_LEN);
return add_label_string(&cbb, "HPKE") && //
CBB_add_u16(&cbb, ctx->kem->id) && //
CBB_add_u16(&cbb, ctx->kdf->id) && //
CBB_add_u16(&cbb, ctx->aead->id);
}
#define HPKE_MODE_BASE 0
#define HPKE_MODE_AUTH 2
static int hpke_key_schedule(EVP_HPKE_CTX *ctx, uint8_t mode,
const uint8_t *shared_secret,
size_t shared_secret_len, const uint8_t *info,
size_t info_len) {
uint8_t suite_id[HPKE_SUITE_ID_LEN];
if (!hpke_build_suite_id(ctx, suite_id)) {
return 0;
}
// psk_id_hash = LabeledExtract("", "psk_id_hash", psk_id)
// TODO(davidben): Precompute this value and store it with the EVP_HPKE_KDF.
const EVP_MD *hkdf_md = ctx->kdf->hkdf_md_func();
uint8_t psk_id_hash[EVP_MAX_MD_SIZE];
size_t psk_id_hash_len;
if (!hpke_labeled_extract(hkdf_md, psk_id_hash, &psk_id_hash_len, NULL, 0,
suite_id, sizeof(suite_id), "psk_id_hash", NULL,
0)) {
return 0;
}
// info_hash = LabeledExtract("", "info_hash", info)
uint8_t info_hash[EVP_MAX_MD_SIZE];
size_t info_hash_len;
if (!hpke_labeled_extract(hkdf_md, info_hash, &info_hash_len, NULL, 0,
suite_id, sizeof(suite_id), "info_hash", info,
info_len)) {
return 0;
}
// key_schedule_context = concat(mode, psk_id_hash, info_hash)
uint8_t context[sizeof(uint8_t) + 2 * EVP_MAX_MD_SIZE];
size_t context_len;
CBB context_cbb;
CBB_init_fixed(&context_cbb, context, sizeof(context));
if (!CBB_add_u8(&context_cbb, mode) ||
!CBB_add_bytes(&context_cbb, psk_id_hash, psk_id_hash_len) ||
!CBB_add_bytes(&context_cbb, info_hash, info_hash_len) ||
!CBB_finish(&context_cbb, NULL, &context_len)) {
return 0;
}
// secret = LabeledExtract(shared_secret, "secret", psk)
uint8_t secret[EVP_MAX_MD_SIZE];
size_t secret_len;
if (!hpke_labeled_extract(hkdf_md, secret, &secret_len, shared_secret,
shared_secret_len, suite_id, sizeof(suite_id),
"secret", NULL, 0)) {
return 0;
}
// key = LabeledExpand(secret, "key", key_schedule_context, Nk)
const EVP_AEAD *aead = EVP_HPKE_AEAD_aead(ctx->aead);
uint8_t key[EVP_AEAD_MAX_KEY_LENGTH];
const size_t kKeyLen = EVP_AEAD_key_length(aead);
if (!hpke_labeled_expand(hkdf_md, key, kKeyLen, secret, secret_len, suite_id,
sizeof(suite_id), "key", context, context_len) ||
!EVP_AEAD_CTX_init(&ctx->aead_ctx, aead, key, kKeyLen,
EVP_AEAD_DEFAULT_TAG_LENGTH, NULL)) {
return 0;
}
// base_nonce = LabeledExpand(secret, "base_nonce", key_schedule_context, Nn)
if (!hpke_labeled_expand(hkdf_md, ctx->base_nonce,
EVP_AEAD_nonce_length(aead), secret, secret_len,
suite_id, sizeof(suite_id), "base_nonce", context,
context_len)) {
return 0;
}
// exporter_secret = LabeledExpand(secret, "exp", key_schedule_context, Nh)
if (!hpke_labeled_expand(hkdf_md, ctx->exporter_secret, EVP_MD_size(hkdf_md),
secret, secret_len, suite_id, sizeof(suite_id),
"exp", context, context_len)) {
return 0;
}
return 1;
}
void EVP_HPKE_CTX_zero(EVP_HPKE_CTX *ctx) {
OPENSSL_memset(ctx, 0, sizeof(EVP_HPKE_CTX));
EVP_AEAD_CTX_zero(&ctx->aead_ctx);
}
void EVP_HPKE_CTX_cleanup(EVP_HPKE_CTX *ctx) {
EVP_AEAD_CTX_cleanup(&ctx->aead_ctx);
}
EVP_HPKE_CTX *EVP_HPKE_CTX_new(void) {
EVP_HPKE_CTX *ctx = OPENSSL_malloc(sizeof(EVP_HPKE_CTX));
if (ctx == NULL) {
return NULL;
}
EVP_HPKE_CTX_zero(ctx);
return ctx;
}
void EVP_HPKE_CTX_free(EVP_HPKE_CTX *ctx) {
if (ctx != NULL) {
EVP_HPKE_CTX_cleanup(ctx);
OPENSSL_free(ctx);
}
}
int EVP_HPKE_CTX_setup_sender(EVP_HPKE_CTX *ctx, uint8_t *out_enc,
size_t *out_enc_len, size_t max_enc,
const EVP_HPKE_KEM *kem, const EVP_HPKE_KDF *kdf,
const EVP_HPKE_AEAD *aead,
const uint8_t *peer_public_key,
size_t peer_public_key_len, const uint8_t *info,
size_t info_len) {
uint8_t seed[MAX_SEED_LEN];
RAND_bytes(seed, kem->seed_len);
return EVP_HPKE_CTX_setup_sender_with_seed_for_testing(
ctx, out_enc, out_enc_len, max_enc, kem, kdf, aead, peer_public_key,
peer_public_key_len, info, info_len, seed, kem->seed_len);
}
int EVP_HPKE_CTX_setup_sender_with_seed_for_testing(
EVP_HPKE_CTX *ctx, uint8_t *out_enc, size_t *out_enc_len, size_t max_enc,
const EVP_HPKE_KEM *kem, const EVP_HPKE_KDF *kdf, const EVP_HPKE_AEAD *aead,
const uint8_t *peer_public_key, size_t peer_public_key_len,
const uint8_t *info, size_t info_len, const uint8_t *seed,
size_t seed_len) {
EVP_HPKE_CTX_zero(ctx);
ctx->is_sender = 1;
ctx->kem = kem;
ctx->kdf = kdf;
ctx->aead = aead;
uint8_t shared_secret[MAX_SHARED_SECRET_LEN];
size_t shared_secret_len;
if (!kem->encap_with_seed(kem, shared_secret, &shared_secret_len, out_enc,
out_enc_len, max_enc, peer_public_key,
peer_public_key_len, seed, seed_len) ||
!hpke_key_schedule(ctx, HPKE_MODE_BASE, shared_secret, shared_secret_len,
info, info_len)) {
EVP_HPKE_CTX_cleanup(ctx);
return 0;
}
return 1;
}
int EVP_HPKE_CTX_setup_recipient(EVP_HPKE_CTX *ctx, const EVP_HPKE_KEY *key,
const EVP_HPKE_KDF *kdf,
const EVP_HPKE_AEAD *aead, const uint8_t *enc,
size_t enc_len, const uint8_t *info,
size_t info_len) {
EVP_HPKE_CTX_zero(ctx);
ctx->is_sender = 0;
ctx->kem = key->kem;
ctx->kdf = kdf;
ctx->aead = aead;
uint8_t shared_secret[MAX_SHARED_SECRET_LEN];
size_t shared_secret_len;
if (!key->kem->decap(key, shared_secret, &shared_secret_len, enc, enc_len) ||
!hpke_key_schedule(ctx, HPKE_MODE_BASE, shared_secret, shared_secret_len,
info, info_len)) {
EVP_HPKE_CTX_cleanup(ctx);
return 0;
}
return 1;
}
int EVP_HPKE_CTX_setup_auth_sender(
EVP_HPKE_CTX *ctx, uint8_t *out_enc, size_t *out_enc_len, size_t max_enc,
const EVP_HPKE_KEY *key, const EVP_HPKE_KDF *kdf, const EVP_HPKE_AEAD *aead,
const uint8_t *peer_public_key, size_t peer_public_key_len,
const uint8_t *info, size_t info_len) {
uint8_t seed[MAX_SEED_LEN];
RAND_bytes(seed, key->kem->seed_len);
return EVP_HPKE_CTX_setup_auth_sender_with_seed_for_testing(
ctx, out_enc, out_enc_len, max_enc, key, kdf, aead, peer_public_key,
peer_public_key_len, info, info_len, seed, key->kem->seed_len);
}
int EVP_HPKE_CTX_setup_auth_sender_with_seed_for_testing(
EVP_HPKE_CTX *ctx, uint8_t *out_enc, size_t *out_enc_len, size_t max_enc,
const EVP_HPKE_KEY *key, const EVP_HPKE_KDF *kdf, const EVP_HPKE_AEAD *aead,
const uint8_t *peer_public_key, size_t peer_public_key_len,
const uint8_t *info, size_t info_len, const uint8_t *seed,
size_t seed_len) {
if (key->kem->auth_encap_with_seed == NULL) {
// Not all HPKE KEMs support AuthEncap.
OPENSSL_PUT_ERROR(EVP, EVP_R_OPERATION_NOT_SUPPORTED_FOR_THIS_KEYTYPE);
return 0;
}
EVP_HPKE_CTX_zero(ctx);
ctx->is_sender = 1;
ctx->kem = key->kem;
ctx->kdf = kdf;
ctx->aead = aead;
uint8_t shared_secret[MAX_SHARED_SECRET_LEN];
size_t shared_secret_len;
if (!key->kem->auth_encap_with_seed(
key, shared_secret, &shared_secret_len, out_enc, out_enc_len, max_enc,
peer_public_key, peer_public_key_len, seed, seed_len) ||
!hpke_key_schedule(ctx, HPKE_MODE_AUTH, shared_secret, shared_secret_len,
info, info_len)) {
EVP_HPKE_CTX_cleanup(ctx);
return 0;
}
return 1;
}
int EVP_HPKE_CTX_setup_auth_recipient(
EVP_HPKE_CTX *ctx, const EVP_HPKE_KEY *key, const EVP_HPKE_KDF *kdf,
const EVP_HPKE_AEAD *aead, const uint8_t *enc, size_t enc_len,
const uint8_t *info, size_t info_len, const uint8_t *peer_public_key,
size_t peer_public_key_len) {
if (key->kem->auth_decap == NULL) {
// Not all HPKE KEMs support AuthDecap.
OPENSSL_PUT_ERROR(EVP, EVP_R_OPERATION_NOT_SUPPORTED_FOR_THIS_KEYTYPE);
return 0;
}
EVP_HPKE_CTX_zero(ctx);
ctx->is_sender = 0;
ctx->kem = key->kem;
ctx->kdf = kdf;
ctx->aead = aead;
uint8_t shared_secret[MAX_SHARED_SECRET_LEN];
size_t shared_secret_len;
if (!key->kem->auth_decap(key, shared_secret, &shared_secret_len, enc,
enc_len, peer_public_key, peer_public_key_len) ||
!hpke_key_schedule(ctx, HPKE_MODE_AUTH, shared_secret, shared_secret_len,
info, info_len)) {
EVP_HPKE_CTX_cleanup(ctx);
return 0;
}
return 1;
}
static void hpke_nonce(const EVP_HPKE_CTX *ctx, uint8_t *out_nonce,
size_t nonce_len) {
assert(nonce_len >= 8);
// Write padded big-endian bytes of |ctx->seq| to |out_nonce|.
OPENSSL_memset(out_nonce, 0, nonce_len);
uint64_t seq_copy = ctx->seq;
for (size_t i = 0; i < 8; i++) {
out_nonce[nonce_len - i - 1] = seq_copy & 0xff;
seq_copy >>= 8;
}
// XOR the encoded sequence with the |ctx->base_nonce|.
for (size_t i = 0; i < nonce_len; i++) {
out_nonce[i] ^= ctx->base_nonce[i];
}
}
int EVP_HPKE_CTX_open(EVP_HPKE_CTX *ctx, uint8_t *out, size_t *out_len,
size_t max_out_len, const uint8_t *in, size_t in_len,
const uint8_t *ad, size_t ad_len) {
if (ctx->is_sender) {
OPENSSL_PUT_ERROR(EVP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
return 0;
}
if (ctx->seq == UINT64_MAX) {
OPENSSL_PUT_ERROR(EVP, ERR_R_OVERFLOW);
return 0;
}
uint8_t nonce[EVP_AEAD_MAX_NONCE_LENGTH];
const size_t nonce_len = EVP_AEAD_nonce_length(ctx->aead_ctx.aead);
hpke_nonce(ctx, nonce, nonce_len);
if (!EVP_AEAD_CTX_open(&ctx->aead_ctx, out, out_len, max_out_len, nonce,
nonce_len, in, in_len, ad, ad_len)) {
return 0;
}
ctx->seq++;
return 1;
}
int EVP_HPKE_CTX_seal(EVP_HPKE_CTX *ctx, uint8_t *out, size_t *out_len,
size_t max_out_len, const uint8_t *in, size_t in_len,
const uint8_t *ad, size_t ad_len) {
if (!ctx->is_sender) {
OPENSSL_PUT_ERROR(EVP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
return 0;
}
if (ctx->seq == UINT64_MAX) {
OPENSSL_PUT_ERROR(EVP, ERR_R_OVERFLOW);
return 0;
}
uint8_t nonce[EVP_AEAD_MAX_NONCE_LENGTH];
const size_t nonce_len = EVP_AEAD_nonce_length(ctx->aead_ctx.aead);
hpke_nonce(ctx, nonce, nonce_len);
if (!EVP_AEAD_CTX_seal(&ctx->aead_ctx, out, out_len, max_out_len, nonce,
nonce_len, in, in_len, ad, ad_len)) {
return 0;
}
ctx->seq++;
return 1;
}
int EVP_HPKE_CTX_export(const EVP_HPKE_CTX *ctx, uint8_t *out,
size_t secret_len, const uint8_t *context,
size_t context_len) {
uint8_t suite_id[HPKE_SUITE_ID_LEN];
if (!hpke_build_suite_id(ctx, suite_id)) {
return 0;
}
const EVP_MD *hkdf_md = ctx->kdf->hkdf_md_func();
if (!hpke_labeled_expand(hkdf_md, out, secret_len, ctx->exporter_secret,
EVP_MD_size(hkdf_md), suite_id, sizeof(suite_id),
"sec", context, context_len)) {
return 0;
}
return 1;
}
size_t EVP_HPKE_CTX_max_overhead(const EVP_HPKE_CTX *ctx) {
assert(ctx->is_sender);
return EVP_AEAD_max_overhead(EVP_AEAD_CTX_aead(&ctx->aead_ctx));
}
const EVP_HPKE_KEM *EVP_HPKE_CTX_kem(const EVP_HPKE_CTX *ctx) {
return ctx->kem;
}
const EVP_HPKE_AEAD *EVP_HPKE_CTX_aead(const EVP_HPKE_CTX *ctx) {
return ctx->aead;
}
const EVP_HPKE_KDF *EVP_HPKE_CTX_kdf(const EVP_HPKE_CTX *ctx) {
return ctx->kdf;
}