lwsac_assert_valid

Author: lws-team

include/libwebsockets/lws-lwsac.h

@@ -287,4 +287,25 @@ lwsac_total_overhead(struct lwsac *head);
 LWS_VISIBLE LWS_EXTERN uint8_t *
 lwsac_scan_extant(struct lwsac *head, uint8_t *find, size_t len, int nul);
 
+/**
+ * lwsac_assert_valid() - checks if check..check + len is a valid pointer into memory owned by ac
+ *
+ * \param ac: the lwsac to confirm with
+ * \param check: the pointer to check
+ * \param len: length in bytes of check area
+ *
+ * Returns 0 if the pointer is in the lwsac, or nonzero if the pointer is
+ * not in a valid region of the lwsac
+ */
+
+LWS_VISIBLE LWS_EXTERN int
+_lwsac_assert_valid(struct lwsac *aco, void *check, size_t len, const char *name_ac, const char *name_blob, const char *filename, int line);
+
+#define __lws_sify(_s) _lws_sify(_s)
+#define _lws_sify(_s) #_s
+
+/* use the below macro to invoke the above function */
+
+#define lwsac_assert_valid(_ac, _check, _len) _lwsac_assert_valid(_ac, _check, _len, __lws_sify(_ac), __lws_sify(_check), __FILE__, __LINE__)
+
 ///@}

lib/misc/lwsac/lwsac.c

@@ -1,7 +1,7 @@
 /*
  * libwebsockets - small server side websockets and web server implementation
  *
- * Copyright (C) 2010 - 2020 Andy Green <andy@warmcat.com>
+ * Copyright (C) 2010 - 2025 Andy Green <andy@warmcat.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to
@@ -356,3 +356,37 @@ lwsac_detach(struct lwsac **head)
 		lwsl_debug("%s: head %p: refcount %d: Marked as detached\n",
 			    __func__, *head, lachead->refcount);
 }
+
+int
+_lwsac_assert_valid(struct lwsac *aco, void *check, size_t len, const char *name_ac, const char *name_blob,
+		    const char *filename, int line)
+{
+	struct lwsac *ac = aco;
+
+	while (ac) {
+		void *pos = (uint8_t *)&ac[1],
+		     *end = ((uint8_t *)ac) + ac->ofs;
+
+		if (check >= pos && (void *)(((uint8_t *)check) + len) <= end)
+			return 0;
+
+		ac = ac->next;
+	}
+
+	ac = aco;
+
+	while (ac) {
+		void *pos = (uint8_t *)&ac[1],
+		     *end = ((uint8_t *)ac) + ac->ofs;
+
+		lwsl_notice("%s: ac chunk  %p -> %p\n", __func__, pos, end);
+
+		ac = ac->next;
+	}
+
+	lwsl_err("%s:%d:  %s (%p) len %u is not found inside lwsac %s (%p)\n", filename, line, name_blob, check, (unsigned int)len, name_ac, aco);
+	assert(0); /* checked ptr is not in ac */
+
+	return 1;
+}
+