OCSP stapling with HAProxy as a server

This patch allows to load and validate OCSP response file in DER format, when
haproxy starts. This file should be kept at the same path as the using server
certificate and *.issuer file (set as ssl crt keyword value at haproxy's bind
line):

	bind *:1443 ssl crt show_ocsp_server.pem

	~/haproxy master$ ls -al show_ocsp_server.pem*
	-rw-r--r-- 1 root root 6918 mai   16 19:25 show_ocsp_server.pem
	-rw-r--r-- 1 root root 1830 mai   16 19:25 show_ocsp_server.pem.issuer
	-rw-r--r-- 1 root root 2281 mai   16 19:25 show_ocsp_server.pem.ocsp

src/ocsp.c

@@ -730,6 +730,7 @@ WOLFSSL_OCSP_CERTID* wolfSSL_OCSP_cert_to_id(
     WOLFSSL_CERT_MANAGER* cm = NULL;
     int ret = -1;
     DerBuffer* derCert = NULL;
+
 #ifdef WOLFSSL_SMALL_STACK
     DecodedCert *cert = NULL;
 #else
@@ -1211,6 +1212,41 @@ int wolfSSL_i2d_OCSP_REQUEST_bio(WOLFSSL_BIO* out,
 }
 #endif /* !NO_BIO */
 
+/* workaround to provide some similar functionaly as i2d_OCSP_CERTID,
+ * as it seems not to be implemented in WolfSSL in the same way as in OpenSSL.
+ * wolfSSL_i2d_OCSP_CERTID in its given implementation always returns 0, when
+ * proper cert_id and valid address in *data are provided. This happens, because
+ * id->rawCertIdSize is always 0 at this stage (HAProxy OCSP load workflow), as
+ * it's not filled by wolfSSL_OCSP_cert_to_id(), called by haproxy before.
+ */
+#if defined(WOLFSSL_HAPROXY)
+
+/* Apparently 128 is max len of CertID defined in rfc2560 (X.509 Internet Public
+ * Key Infrastructure Online Certificate Status Protocol - OCSP)
+ * CertID          ::=     SEQUENCE {
+       hashAlgorithm       AlgorithmIdentifier, -->  word32 hashAlgoOID in OcspEntry
+       issuerNameHash      OCTET STRING, -- Hash of Issuer's DN --> limited by OCSP_DIGEST_SIZE=32
+       issuerKeyHash       OCTET STRING, -- Hash of Issuers public key --> limited by OCSP_DIGEST_SIZE=32
+       serialNumber        CertificateSerialNumber --> limited by EXTERNAL_SERIAL_SIZE=32
+ * }
+ */
+#define OCSP_MAX_CERTID_ASN1_LENGTH 128
+int wolfSSL_i2d_OCSP_CERTID(WOLFSSL_OCSP_CERTID* id, unsigned char** encoded_cert_id)
+{
+	if (id == NULL)
+		return WOLFSSL_FAILURE;
+
+	if (!sizeof(id->issuerHash) || (sizeof(id->issuerHash) > OCSP_MAX_CERTID_ASN1_LENGTH))
+		return WOLFSSL_FAILURE;
+
+	if (!encoded_cert_id)
+		return sizeof(id->issuerHash);
+
+	XMEMCPY(*encoded_cert_id, id->issuerHash, sizeof(id->issuerHash));
+
+	return sizeof(id->issuerHash);
+}
+#else
 int wolfSSL_i2d_OCSP_CERTID(WOLFSSL_OCSP_CERTID* id, unsigned char** data)
 {
     if (id == NULL || data == NULL)
@@ -1231,6 +1267,8 @@ int wolfSSL_i2d_OCSP_CERTID(WOLFSSL_OCSP_CERTID* id, unsigned char** data)
     return id->rawCertIdSize;
 }
 
+#endif  /* WOLFSSL_HAPROXY */
+
 WOLFSSL_OCSP_CERTID* wolfSSL_d2i_OCSP_CERTID(WOLFSSL_OCSP_CERTID** cidOut,
                                              const unsigned char** derIn,
                                              int length)
@@ -1294,9 +1332,11 @@ int wolfSSL_OCSP_id_cmp(WOLFSSL_OCSP_CERTID *a, WOLFSSL_OCSP_CERTID *b)
     if (a == NULL || b == NULL)
         return WOLFSSL_FATAL_ERROR;
 
-    ret = a->hashAlgoOID != b->hashAlgoOID;
-    if (ret == 0)
-        ret = XMEMCMP(a->issuerHash, b->issuerHash, OCSP_DIGEST_SIZE);
+    /* commented this one, as hashAlgoOID is not set by WOLFSSL_OCSP_CERTID
+     * ret = a->hashAlgoOID != b->hashAlgoOID;
+     * if (ret == 0)
+     */
+    ret = XMEMCMP(a->issuerHash, b->issuerHash, OCSP_DIGEST_SIZE);
     if (ret == 0)
         ret = XMEMCMP(a->issuerKeyHash, b->issuerKeyHash, OCSP_DIGEST_SIZE);
     if (ret == 0) {