Add server side support for requesting client certificates in tls 1.3

ok jsing@

1 files changed, 173 insertions, 4 deletions

diff --git a/src/lib/libssl/tls13_server.c b/src/lib/libssl/tls13_server.c
index 64c9741d7d..e5e029c998 100644
--- a/src/lib/libssl/tls13_server.c
+++ b/src/lib/libssl/tls13_server.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_server.c,v 1.18 2020/01/26 03:38:24 beck Exp $ */
+/* $OpenBSD: tls13_server.c,v 1.19 2020/01/26 03:55:22 beck Exp $ */
 /*
  * Copyright (c) 2019, 2020 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2020 Bob Beck <beck@openbsd.org>
@@ -314,13 +314,179 @@ tls13_client_end_of_early_data_recv(struct tls13_ctx *ctx, CBS *cbs)
 int
 tls13_client_certificate_recv(struct tls13_ctx *ctx, CBS *cbs)
 {
-        return 0;
+        CBS cert_request_context, cert_list, cert_data, cert_exts;
+        struct stack_st_X509 *certs = NULL;
+        SSL *s = ctx->ssl;
+        X509 *cert = NULL;
+        EVP_PKEY *pkey;
+        const uint8_t *p;
+        int cert_idx;
+        int ret = 0;
+
+        if (!CBS_get_u8_length_prefixed(cbs, &cert_request_context))
+                goto err;
+        if (CBS_len(&cert_request_context) != 0)
+                goto err;
+        if (!CBS_get_u24_length_prefixed(cbs, &cert_list))
+                goto err;
+
+        if (CBS_len(&cert_list) == 0)
+                return 1;
+
+        if ((certs = sk_X509_new_null()) == NULL)
+                goto err;
+        while (CBS_len(&cert_list) > 0) {
+                if (!CBS_get_u24_length_prefixed(&cert_list, &cert_data))
+                        goto err;
+                if (!CBS_get_u16_length_prefixed(&cert_list, &cert_exts))
+                        goto err;
+
+                p = CBS_data(&cert_data);
+                if ((cert = d2i_X509(NULL, &p, CBS_len(&cert_data))) == NULL)
+                        goto err;
+                if (p != CBS_data(&cert_data) + CBS_len(&cert_data))
+                        goto err;
+
+                if (!sk_X509_push(certs, cert))
+                        goto err;
+
+                cert = NULL;
+        }
+
+        /*
+         * At this stage we still have no proof of possession. As such, it would
+         * be preferable to keep the chain and verify once we have successfully
+         * processed the CertificateVerify message.
+         */
+        if (ssl_verify_cert_chain(s, certs) <= 0 &&
+            s->verify_mode != SSL_VERIFY_NONE) {
+                ctx->alert = ssl_verify_alarm_type(s->verify_result);
+                tls13_set_errorx(ctx, TLS13_ERR_VERIFY_FAILED, 0,
+                    "failed to verify peer certificate", NULL);
+                goto err;
+        }
+        ERR_clear_error();
+
+        cert = sk_X509_value(certs, 0);
+        X509_up_ref(cert);
+
+        if ((pkey = X509_get0_pubkey(cert)) == NULL)
+                goto err;
+        if (EVP_PKEY_missing_parameters(pkey))
+                goto err;
+        if ((cert_idx = ssl_cert_type(cert, pkey)) < 0)
+                goto err;
+
+        ssl_sess_cert_free(SSI(s)->sess_cert);
+        if ((SSI(s)->sess_cert = ssl_sess_cert_new()) == NULL)
+                goto err;
+
+        SSI(s)->sess_cert->cert_chain = certs;
+        certs = NULL;
+
+        X509_up_ref(cert);
+        SSI(s)->sess_cert->peer_pkeys[cert_idx].x509 = cert;
+        SSI(s)->sess_cert->peer_key = &(SSI(s)->sess_cert->peer_pkeys[cert_idx]);
+
+        X509_free(s->session->peer);
+
+        X509_up_ref(cert);
+        s->session->peer = cert;
+        s->session->verify_result = s->verify_result;
+
+        ctx->handshake_stage.hs_type |= WITH_CCV;
+        ret = 1;
+
+ err:
+        sk_X509_pop_free(certs, X509_free);
+        X509_free(cert);
+
+        return ret;
 }
 
 int
 tls13_client_certificate_verify_recv(struct tls13_ctx *ctx, CBS *cbs)
 {
-        return 0;
+        const struct ssl_sigalg *sigalg;
+        uint16_t signature_scheme;
+        uint8_t *sig_content = NULL;
+        size_t sig_content_len;
+        EVP_MD_CTX *mdctx = NULL;
+        EVP_PKEY_CTX *pctx;
+        EVP_PKEY *pkey;
+        X509 *cert;
+        CBS signature;
+        CBB cbb;
+        int ret = 0;
+
+        memset(&cbb, 0, sizeof(cbb));
+
+        if (!CBS_get_u16(cbs, &signature_scheme))
+                goto err;
+        if (!CBS_get_u16_length_prefixed(cbs, &signature))
+                goto err;
+
+        if ((sigalg = ssl_sigalg(signature_scheme, tls13_sigalgs,
+            tls13_sigalgs_len)) == NULL)
+                goto err;
+
+        if (!CBB_init(&cbb, 0))
+                goto err;
+        if (!CBB_add_bytes(&cbb, tls13_cert_verify_pad,
+            sizeof(tls13_cert_verify_pad)))
+                goto err;
+        if (!CBB_add_bytes(&cbb, tls13_cert_client_verify_context,
+            strlen(tls13_cert_client_verify_context)))
+                goto err;
+        if (!CBB_add_u8(&cbb, 0))
+                goto err;
+        if (!CBB_add_bytes(&cbb, ctx->hs->transcript_hash,
+            ctx->hs->transcript_hash_len))
+                goto err;
+        if (!CBB_finish(&cbb, &sig_content, &sig_content_len))
+                goto err;
+
+        if ((cert = ctx->ssl->session->peer) == NULL)
+                goto err;
+        if ((pkey = X509_get0_pubkey(cert)) == NULL)
+                goto err;
+        if (!ssl_sigalg_pkey_ok(sigalg, pkey, 1))
+                goto err;
+
+        if (CBS_len(&signature) > EVP_PKEY_size(pkey))
+                goto err;
+
+        if ((mdctx = EVP_MD_CTX_new()) == NULL)
+                goto err;
+        if (!EVP_DigestVerifyInit(mdctx, &pctx, sigalg->md(), NULL, pkey))
+                goto err;
+        if (sigalg->flags & SIGALG_FLAG_RSA_PSS) {
+                if (!EVP_PKEY_CTX_set_rsa_padding(pctx, RSA_PKCS1_PSS_PADDING))
+                        goto err;
+                if (!EVP_PKEY_CTX_set_rsa_pss_saltlen(pctx, -1))
+                        goto err;
+        }
+        if (!EVP_DigestVerifyUpdate(mdctx, sig_content, sig_content_len)) {
+                ctx->alert = TLS1_AD_DECRYPT_ERROR;
+                goto err;
+        }
+        if (EVP_DigestVerifyFinal(mdctx, CBS_data(&signature),
+            CBS_len(&signature)) <= 0) {
+                ctx->alert = TLS1_AD_DECRYPT_ERROR;
+                goto err;
+        }
+
+        ret = 1;
+
+ err:
+        if (!ret && ctx->alert == 0) {
+                ctx->alert = TLS1_AD_DECODE_ERROR;
+        }
+        CBB_cleanup(&cbb);
+        EVP_MD_CTX_free(mdctx);
+        free(sig_content);
+
+        return ret;
 }
 
 int
@@ -439,7 +605,10 @@ tls13_server_hello_sent(struct tls13_ctx *ctx)
             &secrets->server_handshake_traffic))
                 goto err;
 
-        ctx->handshake_stage.hs_type |= NEGOTIATED | WITHOUT_CR;
+        ctx->handshake_stage.hs_type |= NEGOTIATED;
+        if (!(SSL_get_verify_mode(s) & SSL_VERIFY_PEER))
+                ctx->handshake_stage.hs_type |= WITHOUT_CR;
+
         ret = 1;
 
  err: