OSS-Fuzz: Add oscore conf parse fuzzer

tests/oss-fuzz/oscore_conf_parse_target.c

@@ -0,0 +1,46 @@
+#include "coap3/coap_internal.h"
+
+int
+LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  coap_oscore_conf_t *oscore_conf;
+  coap_str_const_t conf_mem;
+  cose_encrypt0_t cose[1];
+  uint8_t *buf;
+
+  if (size < 1)
+    return 0;
+
+  /* Initialize libcoap */
+  coap_startup();
+  coap_set_log_level(COAP_LOG_EMERG);
+
+  /* The coap_new_oscore_conf() API expects null-terminated input data. */
+  buf = (uint8_t *)malloc(size + 1);
+  if (buf == NULL) {
+    coap_cleanup();
+    return 0;
+  }
+  memcpy(buf, data, size);
+  buf[size] = '\0';
+
+  /* Initialisation */
+  conf_mem.s = buf;
+  conf_mem.length = size + 1;
+
+  /* Attempt to parse the fuzzer input as OSCORE configuration */
+  oscore_conf = coap_new_oscore_conf(conf_mem, NULL, NULL, 0);
+
+  /* Clean up if parsing succeeded */
+  if (oscore_conf) {
+    coap_delete_oscore_conf(oscore_conf);
+  }
+
+  free(buf);
+
+  /* Attempt to decode OSCORE option value */
+  cose_encrypt0_init(cose);
+  oscore_decode_option_value(data, size, cose);
+
+  coap_cleanup();
+  return 0;
+}