+
+static int final_sig_algs(SSL *s, unsigned int context, int sent, int *al)
+{
+ if (!sent && SSL_IS_TLS13(s)) {
+ *al = TLS13_AD_MISSING_EXTENSION;
+ SSLerr(SSL_F_FINAL_SIG_ALGS, SSL_R_MISSING_SIGALGS_EXTENSION);
+ return 0;
+ }
+
+ return 1;
+}
+
+
+static int final_key_share(SSL *s, unsigned int context, int sent, int *al)
+{
+ if (!SSL_IS_TLS13(s))
+ return 1;
+
+ /*
+ * If
+ * we have no key_share
+ * AND
+ * (we are not resuming
+ * OR the kex_mode doesn't allow non key_share resumes)
+ * THEN
+ * fail
+ */
+ if (((s->server && s->s3->peer_tmp == NULL) || (!s->server && !sent))
+ && (!s->hit
+ || (s->ext.psk_kex_mode & TLSEXT_KEX_MODE_FLAG_KE) == 0)) {
+ /* No suitable share */
+ /* TODO(TLS1.3): Send a HelloRetryRequest */
+ *al = SSL_AD_HANDSHAKE_FAILURE;
+ SSLerr(SSL_F_FINAL_KEY_SHARE, SSL_R_NO_SUITABLE_KEY_SHARE);
+ return 0;
+ }
+
+ /*
+ * For a client side resumption with no key_share we need to generate
+ * the handshake secret (otherwise this is done during key_share
+ * processing).
+ */
+ if (!sent && !s->server && !tls13_generate_handshake_secret(s, NULL, 0)) {
+ *al = SSL_AD_INTERNAL_ERROR;
+ SSLerr(SSL_F_FINAL_KEY_SHARE, ERR_R_INTERNAL_ERROR);
+ return 0;
+ }
+
+ return 1;
+}
+
+static int init_psk_kex_modes(SSL *s, unsigned int context)
+{
+ s->ext.psk_kex_mode = TLSEXT_KEX_MODE_FLAG_NONE;
+ return 1;
+}
+
+int tls_psk_do_binder(SSL *s, const EVP_MD *md, const unsigned char *msgstart,
+ size_t binderoffset, const unsigned char *binderin,
+ unsigned char *binderout,
+ SSL_SESSION *sess, int sign)
+{
+ EVP_PKEY *mackey = NULL;
+ EVP_MD_CTX *mctx = NULL;
+ unsigned char hash[EVP_MAX_MD_SIZE], binderkey[EVP_MAX_MD_SIZE];
+ unsigned char finishedkey[EVP_MAX_MD_SIZE], tmpbinder[EVP_MAX_MD_SIZE];
+ const char resumption_label[] = "resumption psk binder key";
+ size_t bindersize, hashsize = EVP_MD_size(md);
+ int ret = -1;
+
+ /* Generate the early_secret */
+ if (!tls13_generate_secret(s, md, NULL, sess->master_key,
+ sess->master_key_length,
+ (unsigned char *)&s->early_secret)) {
+ SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ /*
+ * Create the handshake hash for the binder key...the messages so far are
+ * empty!
+ */
+ mctx = EVP_MD_CTX_new();
+ if (mctx == NULL
+ || EVP_DigestInit_ex(mctx, md, NULL) <= 0
+ || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
+ SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ /* Generate the binder key */
+ if (!tls13_hkdf_expand(s, md, s->early_secret,
+ (unsigned char *)resumption_label,
+ sizeof(resumption_label) - 1, hash, binderkey,
+ hashsize)) {
+ SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ /* Generate the finished key */
+ if (!tls13_derive_finishedkey(s, md, binderkey, finishedkey, hashsize)) {
+ SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ /*
+ * Get a hash of the ClientHello up to the start of the binders.
+ * TODO(TLS1.3): This will need to be tweaked when we implement
+ * HelloRetryRequest to include the digest of the previous messages here.
+ */
+ if (EVP_DigestInit_ex(mctx, md, NULL) <= 0
+ || EVP_DigestUpdate(mctx, msgstart, binderoffset) <= 0
+ || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
+ SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ mackey = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL, finishedkey, hashsize);
+ if (mackey == NULL) {
+ SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ if (!sign)
+ binderout = tmpbinder;
+
+ bindersize = hashsize;
+ if (EVP_DigestSignInit(mctx, NULL, md, NULL, mackey) <= 0
+ || EVP_DigestSignUpdate(mctx, hash, hashsize) <= 0
+ || EVP_DigestSignFinal(mctx, binderout, &bindersize) <= 0
+ || bindersize != hashsize) {
+ SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
+ goto err;
+ }
+
+ if (sign) {
+ ret = 1;
+ } else {
+ /* HMAC keys can't do EVP_DigestVerify* - use CRYPTO_memcmp instead */
+ ret = (CRYPTO_memcmp(binderin, binderout, hashsize) == 0);
+ }
+
+ err:
+ OPENSSL_cleanse(binderkey, sizeof(binderkey));
+ OPENSSL_cleanse(finishedkey, sizeof(finishedkey));
+ EVP_PKEY_free(mackey);
+ EVP_MD_CTX_free(mctx);
+
+ return ret;
+}