Initial import: ultra-small bruteforce tool, docs, and .gitignore

brute/source/yescrypt/insecure_memzero.h

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+/*-
+ * Copyright 2014 Colin Percival
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _INSECURE_MEMZERO_H_
+#define _INSECURE_MEMZERO_H_
+
+#ifdef SKIP_MEMZERO
+#define insecure_memzero(buf, len) /* empty */
+#else
+
+#include <stddef.h>
+
+/* Pointer to memory-zeroing function. */
+extern void (* volatile insecure_memzero_ptr)(volatile void *, size_t);
+
+/**
+ * insecure_memzero(buf, len):
+ * Attempt to zero ${len} bytes at ${buf} in spite of optimizing compilers'
+ * best (standards-compliant) attempts to remove the buffer-zeroing.  In
+ * particular, to avoid performing the zeroing, a compiler would need to
+ * use optimistic devirtualization; recognize that non-volatile objects do not
+ * need to be treated as volatile, even if they are accessed via volatile
+ * qualified pointers; and perform link-time optimization; in addition to the
+ * dead-code elimination which often causes buffer-zeroing to be elided.
+ *
+ * Note however that zeroing a buffer does not guarantee that the data held
+ * in the buffer is not stored elsewhere; in particular, there may be copies
+ * held in CPU registers or in anonymous allocations on the stack, even if
+ * every named variable is successfully sanitized.  Solving the "wipe data
+ * from the system" problem will require a C language extension which does not
+ * yet exist.
+ *
+ * For more information, see:
+ * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
+ * http://www.daemonology.net/blog/2014-09-06-zeroing-buffers-is-insufficient.html
+ */
+static inline void
+insecure_memzero(volatile void * buf, size_t len)
+{
+
+	(insecure_memzero_ptr)(buf, len);
+}
+
+#endif
+
+#endif /* !_INSECURE_MEMZERO_H_ */