jwk: add export option to suppress final CRLF

https://github.com/warmcat/libwebsockets/issues/1746

Adding the final CRLF is a NOP at JSON level, but can disrupt hashing the
JSON if it isn't expecting it.

Add flags to the jwk export so it can be controlled... operation remains
unchanged for old values 0 and 1 but a second flag can be OR-ed to control
issue of final CRLF.

include/libwebsockets/lws-jwk.h

@@ -115,19 +115,30 @@ lws_jwk_destroy(struct lws_jwk *jwk);
 LWS_VISIBLE LWS_EXTERN int
 lws_jwk_dup_oct(struct lws_jwk *jwk, const void *key, int len);
 
+#define LWSJWKF_EXPORT_PRIVATE				(1 << 0)
+#define LWSJWKF_EXPORT_NOCRLF				(1 << 1)
+
 /** lws_jwk_export() - Export a JSON Web key to a textual representation
  *
  * \param jwk: the JWK object to export
- * \param _private: 0 = just export public parts, 1 = export everything
+ * \param flags: control export options
  * \param p: the buffer to write the exported JWK to
  * \param len: the length of the buffer \p p in bytes... reduced by used amount
  *
  * Returns length of the used part of the buffer if OK, or -1 for error.
  *
+ * \p flags can be OR-ed together
+ *
+ * LWSJWKF_EXPORT_PRIVATE: default is only public part, set this to also export
+ *			   the private part
+ *
+ * LWSJWKF_EXPORT_NOCRLF: normally adds a CRLF at the end of the export, if
+ *			  you need to suppress it, set this flag
+ *
  * Serializes the content of the JWK into a char buffer.
  */
 LWS_VISIBLE LWS_EXTERN int
-lws_jwk_export(struct lws_jwk *jwk, int _private, char *p, int *len);
+lws_jwk_export(struct lws_jwk *jwk, int flags, char *p, int *len);
 
 /** lws_jwk_load() - Import a JSON Web key from a file
  *

lib/jose/jwk/jwk.c

@@ -667,7 +667,7 @@ lws_jwk_import(struct lws_jwk *jwk, lws_jwk_key_import_callback cb, void *user,
 
 
 LWS_VISIBLE int
-lws_jwk_export(struct lws_jwk *jwk, int private, char *p, int *len)
+lws_jwk_export(struct lws_jwk *jwk, int flags, char *p, int *len)
 {
 	char *start = p, *end = &p[*len - 1];
 	int n, m, limit, first = 1, asym = 0;
@@ -740,9 +740,9 @@ lws_jwk_export(struct lws_jwk *jwk, int private, char *p, int *len)
 					}
 					tok[pos] = '\0';
 					pos = 0;
-					if (private || !asym ||
-					    (strcmp(tok, "sign") &&
-					    strcmp(tok, "encrypt"))) {
+					if ((flags & LWSJWKF_EXPORT_PRIVATE) ||
+					    !asym || (strcmp(tok, "sign") &&
+						      strcmp(tok, "encrypt"))) {
 						if (!f)
 							*p++ = ',';
 						f = 0;
@@ -758,7 +758,8 @@ lws_jwk_export(struct lws_jwk *jwk, int private, char *p, int *len)
 
 			default:
 				/* both sig and enc require asym private key */
-				if (!private && asym && l->idx == (int)JWK_META_USE)
+				if (!(flags & LWSJWKF_EXPORT_PRIVATE) &&
+				    asym && l->idx == (int)JWK_META_USE)
 					break;
 				if (!first)
 					*p++ = ',';
@@ -771,7 +772,7 @@ lws_jwk_export(struct lws_jwk *jwk, int private, char *p, int *len)
 		}
 
 		if ((!(l->meta & 1)) && jwk->e[l->idx].buf &&
-		    (private || !(l->meta & 2))) {
+		    ((flags & LWSJWKF_EXPORT_PRIVATE) || !(l->meta & 2))) {
 			if (!first)
 				*p++ = ',';
 			first = 0;
@@ -798,7 +799,8 @@ lws_jwk_export(struct lws_jwk *jwk, int private, char *p, int *len)
 		l++;
 	}
 
-	p += lws_snprintf(p, end - p, "}\n");
+	p += lws_snprintf(p, end - p,
+			  (flags & LWSJWKF_EXPORT_NOCRLF) ? "}" : "}\n");
 
 	*len -= p - start;
 
@@ -814,7 +816,7 @@ lws_jwk_rfc7638_fingerprint(struct lws_jwk *jwk, char *digest32)
 
 	tmp = lws_malloc(tmpsize, "rfc7638 tmp");
 
-	n = lws_jwk_export(jwk, 0, tmp, &tmpsize);
+	n = lws_jwk_export(jwk, LWSJWKF_EXPORT_NOCRLF, tmp, &tmpsize);
 	if (n < 0)
 		goto bail;
 
@@ -887,7 +889,7 @@ lws_jwk_save(struct lws_jwk *jwk, const char *filename)
 	if (!buf)
 		return -1;
 
-	n = lws_jwk_export(jwk, 1, buf, &buflen);
+	n = lws_jwk_export(jwk, LWSJWKF_EXPORT_PRIVATE, buf, &buflen);
 	if (n < 0)
 		goto bail;
 

minimal-examples/crypto/minimal-crypto-jwk/main.c

@@ -167,7 +167,7 @@ int main(int argc, const char **argv)
 
 	/* private version */
 
-	if (lws_jwk_export(&jwk, 1, key, &vl) < 0) {
+	if (lws_jwk_export(&jwk, LWSJWKF_EXPORT_PRIVATE, key, &vl) < 0) {
 		lwsl_err("lws_jwk_export failed\n");
 
 		return 1;

minimal-examples/crypto/minimal-crypto-x509/main.c

@@ -178,7 +178,7 @@ int main(int argc, const char **argv)
 		lws_jwk_dump(&jwk);
 		lwsl_notice("Issuing Cert + Private JWK on stdout\n");
 		n = sizeof(pembuf);
-		if (lws_jwk_export(&jwk, 1, pembuf, &n))
+		if (lws_jwk_export(&jwk, LWSJWKF_EXPORT_PRIVATE, pembuf, &n))
 			puts(pembuf);
 	}