TLS: Parse OCSPResponse to extract BasicOCSPResponse

This adds the next step for OCSP stapling. The received OCSPResponse is
parsed to get the BasicOCSPResponse. This commit does not yet process
the BasicOCSPResponse.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/tls/tlsv1_client_ocsp.c

@@ -10,17 +10,160 @@
 
 #include "common.h"
 #include "crypto/tls.h"
+#include "asn1.h"
 #include "tlsv1_common.h"
 #include "tlsv1_record.h"
 #include "tlsv1_client.h"
 #include "tlsv1_client_i.h"
 
 
+/* RFC 6960, 4.2.1: OCSPResponseStatus ::= ENUMERATED */
+enum ocsp_response_status {
+	OCSP_RESP_STATUS_SUCCESSFUL = 0,
+	OCSP_RESP_STATUS_MALFORMED_REQ = 1,
+	OCSP_RESP_STATUS_INT_ERROR = 2,
+	OCSP_RESP_STATUS_TRY_LATER = 3,
+	/* 4 not used */
+	OCSP_RESP_STATUS_SIG_REQUIRED = 5,
+	OCSP_RESP_STATUS_UNAUTHORIZED = 6,
+};
+
+
+static int is_oid_basic_ocsp_resp(struct asn1_oid *oid)
+{
+	return oid->len == 10 &&
+		oid->oid[0] == 1 /* iso */ &&
+		oid->oid[1] == 3 /* identified-organization */ &&
+		oid->oid[2] == 6 /* dod */ &&
+		oid->oid[3] == 1 /* internet */ &&
+		oid->oid[4] == 5 /* security */ &&
+		oid->oid[5] == 5 /* mechanisms */ &&
+		oid->oid[6] == 7 /* id-pkix */ &&
+		oid->oid[7] == 48 /* id-ad */ &&
+		oid->oid[8] == 1 /* id-pkix-ocsp */ &&
+		oid->oid[9] == 1 /* id-pkix-ocsp-basic */;
+}
+
+
+static enum tls_ocsp_result
+tls_process_basic_ocsp_response(struct tlsv1_client *conn, const u8 *resp,
+				size_t len)
+{
+	wpa_hexdump(MSG_MSGDUMP, "OCSP: BasicOCSPResponse", resp, len);
+
+	/*
+	 * RFC 6960, 4.2.1:
+	 * BasicOCSPResponse       ::= SEQUENCE {
+	 *    tbsResponseData      ResponseData,
+	 *    signatureAlgorithm   AlgorithmIdentifier,
+	 *    signature            BIT STRING,
+	 *    certs            [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }
+	 */
+
+	/* TODO */
+	return TLS_OCSP_NO_RESPONSE;
+}
+
+
 enum tls_ocsp_result tls_process_ocsp_response(struct tlsv1_client *conn,
 					       const u8 *resp, size_t len)
 {
+	struct asn1_hdr hdr;
+	const u8 *pos, *end;
+	u8 resp_status;
+	struct asn1_oid oid;
+	char obuf[80];
+
 	wpa_hexdump(MSG_MSGDUMP, "TLSv1: OCSPResponse", resp, len);
 
-	/* TODO */
-	return TLS_OCSP_NO_RESPONSE;
+	/*
+	 * RFC 6960, 4.2.1:
+	 * OCSPResponse ::= SEQUENCE {
+	 *    responseStatus  OCSPResponseStatus,
+	 *    responseBytes   [0] EXPLICIT ResponseBytes OPTIONAL }
+	 */
+
+	if (asn1_get_next(resp, len, &hdr) < 0 ||
+	    hdr.class != ASN1_CLASS_UNIVERSAL ||
+	    hdr.tag != ASN1_TAG_SEQUENCE) {
+		wpa_printf(MSG_DEBUG,
+			   "OCSP: Expected SEQUENCE (OCSPResponse) - found class %d tag 0x%x",
+			   hdr.class, hdr.tag);
+		return TLS_OCSP_INVALID;
+	}
+	pos = hdr.payload;
+	end = hdr.payload + hdr.length;
+
+	/* OCSPResponseStatus ::= ENUMERATED */
+	if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
+	    hdr.class != ASN1_CLASS_UNIVERSAL ||
+	    hdr.tag != ASN1_TAG_ENUMERATED ||
+	    hdr.length != 1) {
+		wpa_printf(MSG_DEBUG,
+			   "OCSP: Expected ENUMERATED (responseStatus) - found class %d tag 0x%x length %u",
+			   hdr.class, hdr.tag, hdr.length);
+		return TLS_OCSP_INVALID;
+	}
+	resp_status = hdr.payload[0];
+	wpa_printf(MSG_DEBUG, "OCSP: responseStatus %u", resp_status);
+	pos = hdr.payload + hdr.length;
+	if (resp_status != OCSP_RESP_STATUS_SUCCESSFUL) {
+		wpa_printf(MSG_DEBUG, "OCSP: No stapling result");
+		return TLS_OCSP_NO_RESPONSE;
+	}
+
+	/* responseBytes   [0] EXPLICIT ResponseBytes OPTIONAL */
+	if (pos == end)
+		return TLS_OCSP_NO_RESPONSE;
+
+	if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
+	    hdr.class != ASN1_CLASS_CONTEXT_SPECIFIC ||
+	    hdr.tag != 0) {
+		wpa_printf(MSG_DEBUG,
+			   "OCSP: Expected [0] EXPLICIT (responseBytes) - found class %d tag 0x%x",
+			   hdr.class, hdr.tag);
+		return TLS_OCSP_INVALID;
+	}
+
+	/*
+	 * ResponseBytes ::= SEQUENCE {
+	 *     responseType   OBJECT IDENTIFIER,
+	 *     response       OCTET STRING }
+	 */
+
+	if (asn1_get_next(hdr.payload, hdr.length, &hdr) < 0 ||
+	    hdr.class != ASN1_CLASS_UNIVERSAL ||
+	    hdr.tag != ASN1_TAG_SEQUENCE) {
+		wpa_printf(MSG_DEBUG,
+			   "OCSP: Expected SEQUENCE (ResponseBytes) - found class %d tag 0x%x",
+			   hdr.class, hdr.tag);
+		return TLS_OCSP_INVALID;
+	}
+	pos = hdr.payload;
+	end = hdr.payload + hdr.length;
+
+	/* responseType   OBJECT IDENTIFIER */
+	if (asn1_get_oid(pos, end - pos, &oid, &pos)) {
+		wpa_printf(MSG_DEBUG,
+			   "OCSP: Failed to parse OID (responseType)");
+		return TLS_OCSP_INVALID;
+	}
+	asn1_oid_to_str(&oid, obuf, sizeof(obuf));
+	wpa_printf(MSG_DEBUG, "OCSP: responseType %s", obuf);
+	if (!is_oid_basic_ocsp_resp(&oid)) {
+		wpa_printf(MSG_DEBUG, "OCSP: Ignore unsupported response type");
+		return TLS_OCSP_NO_RESPONSE;
+	}
+
+	/* response       OCTET STRING */
+	if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
+	    hdr.class != ASN1_CLASS_UNIVERSAL ||
+	    hdr.tag != ASN1_TAG_OCTETSTRING) {
+		wpa_printf(MSG_DEBUG,
+			   "OCSP: Expected OCTET STRING (response) - found class %d tag 0x%x",
+			   hdr.class, hdr.tag);
+		return TLS_OCSP_INVALID;
+	}
+
+	return tls_process_basic_ocsp_response(conn, hdr.payload, hdr.length);
 }