nit

src/tls.h

@@ -34,7 +34,7 @@ void mg_tls_handshake(struct mg_connection *);
 // Private
 void mg_tls_ctx_init(struct mg_mgr *);
 void mg_tls_ctx_free(struct mg_mgr *);
-#define MG_IS_DER(buf) ((uint8_t) (buf)[0] == 0x30)  // DER begins with 0x30
+#define MG_IS_DER(buf) (((uint8_t *) (buf))[0] == 0x30)  // DER begins with 0x30
 
 // Low-level IO primives used by TLS layer
 enum { MG_IO_ERR = -1, MG_IO_WAIT = -2, MG_IO_RESET = -3 };

src/tls_mbed.c

@@ -32,7 +32,7 @@ static int mg_mbed_rng(void *ctx, unsigned char *buf, size_t len) {
 static bool mg_load_cert(struct mg_str str, mbedtls_x509_crt *p) {
   int rc;
   if (str.buf == NULL || str.buf[0] == '\0' || str.buf[0] == '*') return true;
-  if (!MG_IS_DER(str.buf[0])) str.len++;  // PEM, include trailing NUL
+  if (!MG_IS_DER(str.buf)) str.len++;  // PEM, include trailing NUL
   if ((rc = mbedtls_x509_crt_parse(p, (uint8_t *) str.buf, str.len)) != 0) {
     MG_ERROR(("cert err %#x", -rc));
     return false;