Add OCSP client side support to libtls.

   - Provide access to certificate OCSP URL
   - Provide ability to check a raw OCSP reply against an
     established TLS ctx
   - Check and validate OCSP stapling info in the TLS handshake
     if a stapled OCSP response is provided.`

Add example code to show OCSP URL and stapled info
into netcat.

ok jsing@

1 files changed, 399 insertions, 0 deletions

diff --git a/lib/libtls/tls_ocsp.c b/lib/libtls/tls_ocsp.c
new file mode 100644
index 00000000000..113ab0dd3dc
--- /dev/null
+++ b/lib/libtls/tls_ocsp.c
@@ -0,0 +1,399 @@
+/*
+ * Copyright (c) 2015 Marko Kreen <markokr@gmail.com>
+ * Copyright (c) 2016 Bob Beck <beck@openbsd.org>
+ *
+ * Permission to use, copy, modify, and 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 <sys/types.h>
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
+#include <openssl/err.h>
+#include <openssl/ocsp.h>
+#include <openssl/x509.h>
+
+#include <tls.h>
+#include "tls_internal.h"
+
+#define MAXAGE_SEC (14*24*60*60)
+#define JITTER_SEC (60)
+
+/*
+ * State for request.
+ */
+
+static struct tls_ocsp_ctx *
+tls_ocsp_ctx_new(void)
+{
+	return (calloc(1, sizeof(struct tls_ocsp_ctx)));
+}
+
+void
+tls_ocsp_ctx_free(struct tls_ocsp_ctx *ocsp_ctx)
+{
+	if (ocsp_ctx == NULL)
+		return;
+
+	free(ocsp_ctx->ocsp_result);
+	ocsp_ctx->ocsp_result = NULL;
+	free(ocsp_ctx->ocsp_url);
+	ocsp_ctx->ocsp_url = NULL;
+	free(ocsp_ctx->request_data);
+	ocsp_ctx->request_data = NULL;
+	free(ocsp_ctx);
+}
+
+static int
+tls_ocsp_asn1_parse_time(struct tls *ctx, ASN1_GENERALIZEDTIME *gt, time_t *time)
+{
+	struct tm tm;
+
+	if (gt == NULL)
+		return -1;
+	/* RFC 6960 specifies that all times in OCSP must be GENERALIZEDTIME */
+	if (asn1_time_parse(gt->data, gt->length, &tm,
+		V_ASN1_GENERALIZEDTIME) == -1)
+		return -1;
+	if ((*time = timegm(&tm)) == -1)
+		return -1;
+	return 0;
+}
+
+static int
+tls_ocsp_fill_info(struct tls *ctx, int response_status, int cert_status,
+    int crl_reason, ASN1_GENERALIZEDTIME *revtime,
+    ASN1_GENERALIZEDTIME *thisupd, ASN1_GENERALIZEDTIME *nextupd)
+{
+	struct tls_ocsp_result *info = NULL;
+
+	free(ctx->ocsp_ctx->ocsp_result);
+	ctx->ocsp_ctx->ocsp_result = NULL;
+
+	if ((info = calloc(1, sizeof (struct tls_ocsp_result))) == NULL) {
+		tls_set_error(ctx, "calloc");
+		return -1;
+	}
+	info->response_status = response_status;
+	info->cert_status = cert_status;
+	info->crl_reason = crl_reason;
+	if (info->response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
+		info->result_msg =
+		    OCSP_response_status_str(info->response_status);
+	} else if (info->cert_status != V_OCSP_CERTSTATUS_REVOKED) {
+		info->result_msg = OCSP_cert_status_str(info->cert_status);
+	} else {
+		info->result_msg = OCSP_crl_reason_str(info->crl_reason);
+	}
+	info->revocation_time = info->this_update = info->next_update = -1;
+	if (revtime != NULL &&
+	    tls_ocsp_asn1_parse_time(ctx, revtime, &info->revocation_time) != 0) {
+		tls_set_error(ctx,
+		    "unable to parse revocation time in OCSP reply");
+		goto error;
+	}
+	if (thisupd != NULL &&
+	    tls_ocsp_asn1_parse_time(ctx, thisupd, &info->this_update) != 0) {
+		tls_set_error(ctx,
+		    "unable to parse this update time in OCSP reply");
+		goto error;
+	}
+	if (nextupd != NULL &&
+	    tls_ocsp_asn1_parse_time(ctx, nextupd, &info->next_update) != 0) {
+		tls_set_error(ctx,
+		    "unable to parse next update time in OCSP reply");
+		goto error;
+	}
+	ctx->ocsp_ctx->ocsp_result = info;
+	return 0;
+ error:
+	free(info);
+	return -1;
+}
+
+static OCSP_CERTID *
+tls_ocsp_get_certid(X509 *main_cert, STACK_OF(X509) *extra_certs,
+    SSL_CTX *ssl_ctx)
+{
+	X509_NAME *issuer_name;
+	X509 *issuer;
+	X509_STORE_CTX storectx;
+	X509_OBJECT tmpobj;
+	OCSP_CERTID *cid = NULL;
+	X509_STORE *store;
+
+	if ((issuer_name = X509_get_issuer_name(main_cert)) == NULL)
+		return NULL;
+
+	if (extra_certs != NULL) {
+		issuer = X509_find_by_subject(extra_certs, issuer_name);
+		if (issuer != NULL)
+			return OCSP_cert_to_id(NULL, main_cert, issuer);
+	}
+
+	if ((store = SSL_CTX_get_cert_store(ssl_ctx)) == NULL)
+		return NULL;
+	if (X509_STORE_CTX_init(&storectx, store, main_cert, extra_certs) != 1)
+		return NULL;
+	if (X509_STORE_get_by_subject(&storectx, X509_LU_X509, issuer_name,
+		&tmpobj) == 1) {
+		cid = OCSP_cert_to_id(NULL, main_cert, tmpobj.data.x509);
+		X509_OBJECT_free_contents(&tmpobj);
+	}
+	X509_STORE_CTX_cleanup(&storectx);
+	return cid;
+}
+
+struct tls_ocsp_ctx *
+tls_ocsp_setup_from_peer(struct tls *ctx)
+{
+	struct tls_ocsp_ctx *ocsp_ctx = NULL;
+	STACK_OF(OPENSSL_STRING) *ocsp_urls = NULL;
+
+	if ((ocsp_ctx = tls_ocsp_ctx_new()) == NULL)
+		goto failed;
+
+	/* steal state from ctx struct */
+	ocsp_ctx->main_cert = SSL_get_peer_certificate(ctx->ssl_conn);
+	ocsp_ctx->extra_certs = SSL_get_peer_cert_chain(ctx->ssl_conn);
+	if (ocsp_ctx->main_cert == NULL) {
+		tls_set_errorx(ctx, "no peer certificate for OCSP");
+		goto failed;
+	}
+
+	ocsp_urls = X509_get1_ocsp(ocsp_ctx->main_cert);
+	if (ocsp_urls == NULL)
+		goto failed;
+	ocsp_ctx->ocsp_url = strdup(sk_OPENSSL_STRING_value(ocsp_urls, 0));
+	if (ocsp_ctx->ocsp_url == NULL) {
+		tls_set_errorx(ctx, "out of memory");
+		goto failed;
+	}
+
+	X509_email_free(ocsp_urls);
+	return ocsp_ctx;
+
+ failed:
+	tls_ocsp_ctx_free(ocsp_ctx);
+	X509_email_free(ocsp_urls);
+	return NULL;
+}
+
+static int
+tls_ocsp_verify_response(struct tls *ctx, OCSP_RESPONSE *resp)
+{
+	OCSP_BASICRESP *br = NULL;
+	ASN1_GENERALIZEDTIME *revtime = NULL, *thisupd = NULL, *nextupd = NULL;
+	OCSP_CERTID *cid = NULL;
+	STACK_OF(X509) *combined = NULL;
+	int response_status=0, cert_status=0, crl_reason=0;
+	int ret = -1;
+	unsigned long flags;
+
+	if ((br = OCSP_response_get1_basic(resp)) == NULL) {
+		tls_set_errorx(ctx, "cannot load ocsp reply");
+		goto error;
+	}
+
+	/*
+	 * Skip validation of 'extra_certs' as this should be done
+	 * already as part of main handshake.
+	 */
+	flags = OCSP_TRUSTOTHER;
+
+	/* now verify */
+	if (OCSP_basic_verify(br, ctx->ocsp_ctx->extra_certs,
+		SSL_CTX_get_cert_store(ctx->ssl_ctx), flags) != 1) {
+		tls_set_error(ctx, "ocsp verify failed");
+		goto error;
+	}
+
+	/* signature OK, look inside */
+	response_status = OCSP_response_status(resp);
+	if (response_status != OCSP_RESPONSE_STATUS_SUCCESSFUL) {
+		tls_set_errorx(ctx, "ocsp verify failed: response - %s",
+		    OCSP_response_status_str(response_status));
+		goto error;
+	}
+
+	cid = tls_ocsp_get_certid(ctx->ocsp_ctx->main_cert,
+	    ctx->ocsp_ctx->extra_certs, ctx->ssl_ctx);
+	if (cid == NULL) {
+		tls_set_errorx(ctx, "ocsp verify failed: no issuer cert");
+		goto error;
+	}
+
+	if (OCSP_resp_find_status(br, cid, &cert_status, &crl_reason,
+	    &revtime, &thisupd, &nextupd) != 1) {
+		tls_set_errorx(ctx, "ocsp verify failed: no result for cert");
+		goto error;
+	}
+
+	if (OCSP_check_validity(thisupd, nextupd, JITTER_SEC,
+	    MAXAGE_SEC) != 1) {
+		tls_set_errorx(ctx,
+		    "ocsp verify failed: ocsp response not current");
+		goto error;
+	}
+
+	if (tls_ocsp_fill_info(ctx, response_status, cert_status,
+	    crl_reason, revtime, thisupd, nextupd) != 0)
+		goto error;
+
+	/* finally can look at status */
+	if (cert_status != V_OCSP_CERTSTATUS_GOOD && cert_status !=
+	    V_OCSP_CERTSTATUS_UNKNOWN) {
+		tls_set_errorx(ctx, "ocsp verify failed: revoked cert - %s",
+			       OCSP_crl_reason_str(crl_reason));
+		goto error;
+	}
+
+	ret = 0;
+
+ error:
+	sk_X509_free(combined);
+	OCSP_CERTID_free(cid);
+	OCSP_BASICRESP_free(br);
+	return ret;
+}
+
+/* TLS handshake verification callback for stapled requests */
+int
+tls_ocsp_verify_cb(SSL *ssl, void *arg)
+{
+	const unsigned char *raw = NULL;
+	int size, res = -1;
+	struct tls *ctx;
+
+	if ((ctx = SSL_get_app_data(ssl)) == NULL)
+		return -1;
+
+	size = SSL_get_tlsext_status_ocsp_resp(ssl, &raw);
+	if (size <= 0)
+		return 1;
+
+	tls_ocsp_ctx_free(ctx->ocsp_ctx);
+	ctx->ocsp_ctx = tls_ocsp_setup_from_peer(ctx);
+	if (ctx->ocsp_ctx != NULL)
+		res = tls_ocsp_process_response(ctx, raw, size);
+
+	return (res == 0) ? 1 : 0;
+}
+
+/*
+ * Public API
+ */
+
+/* Retrieve OSCP URL from peer certificate, if present */
+const char *
+tls_peer_ocsp_url(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return NULL;
+	return ctx->ocsp_ctx->ocsp_url;
+}
+
+const char *
+tls_peer_ocsp_result(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return NULL;
+	if (ctx->ocsp_ctx->ocsp_result == NULL)
+		return NULL;
+	return ctx->ocsp_ctx->ocsp_result->result_msg;
+}
+
+int
+tls_peer_ocsp_response_status(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return -1;
+	if (ctx->ocsp_ctx->ocsp_result == NULL)
+		return -1;
+	return ctx->ocsp_ctx->ocsp_result->response_status;
+}
+
+int
+tls_peer_ocsp_cert_status(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return -1;
+	if (ctx->ocsp_ctx->ocsp_result == NULL)
+		return -1;
+	return ctx->ocsp_ctx->ocsp_result->cert_status;
+}
+
+int
+tls_peer_ocsp_crl_reason(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return -1;
+	if (ctx->ocsp_ctx->ocsp_result == NULL)
+		return -1;
+	return ctx->ocsp_ctx->ocsp_result->crl_reason;
+}
+
+time_t
+tls_peer_ocsp_this_update(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return -1;
+	if (ctx->ocsp_ctx->ocsp_result == NULL)
+		return -1;
+	return ctx->ocsp_ctx->ocsp_result->this_update;
+}
+
+time_t
+tls_peer_ocsp_next_update(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return -1;
+	if (ctx->ocsp_ctx->ocsp_result == NULL)
+		return -1;
+	return ctx->ocsp_ctx->ocsp_result->next_update;
+}
+
+time_t
+tls_peer_ocsp_revocation_time(struct tls *ctx)
+{
+	if (ctx->ocsp_ctx == NULL)
+		return -1;
+	if (ctx->ocsp_ctx->ocsp_result == NULL)
+		return -1;
+	return ctx->ocsp_ctx->ocsp_result->revocation_time;
+}
+
+/*
+ * Process a raw OCSP response from an OCSP server request.
+ * OCSP details can then be retrieved with tls_peer_ocsp_* functions.
+ * returns 0 if certificate ok, -1 otherwise.
+ */
+int
+tls_ocsp_process_response(struct tls *ctx, const unsigned char *response,
+    size_t size)
+{
+	int ret;
+	OCSP_RESPONSE *resp;
+
+	resp = d2i_OCSP_RESPONSE(NULL, &response, size);
+	if (resp == NULL) {
+		tls_ocsp_ctx_free(ctx->ocsp_ctx);
+		ctx->ocsp_ctx = NULL;
+		tls_set_error(ctx, "unable to parse OCSP response");
+		return -1;
+	}
+	ret = tls_ocsp_verify_response(ctx, resp);
+	OCSP_RESPONSE_free(resp);
+	return ret;
+}